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Andolina C, Graumans W, Guelbeogo M, van Gemert GJ, Ramijth J, Harouna S, Soumanaba Z, Stoter R, Vegte-Bolmer M, Pangos M, Sinnis P, Collins K, Staedke SG, Tiono AB, Drakeley C, Lanke K, Bousema T. Quantification of sporozoite expelling by Anopheles mosquitoes infected with laboratory and naturally circulating P. falciparum gametocytes. eLife 2024; 12:RP90989. [PMID: 38517746 PMCID: PMC10959522 DOI: 10.7554/elife.90989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/24/2024] Open
Abstract
It is currently unknown whether all Plasmodium falciparum-infected mosquitoes are equally infectious. We assessed sporogonic development using cultured gametocytes in the Netherlands and naturally circulating strains in Burkina Faso. We quantified the number of sporozoites expelled into artificial skin in relation to intact oocysts, ruptured oocysts, and residual salivary gland sporozoites. In laboratory conditions, higher total sporozoite burden was associated with shorter duration of sporogony (p<0.001). Overall, 53% (116/216) of infected Anopheles stephensi mosquitoes expelled sporozoites into artificial skin with a median of 136 expelled sporozoites (interquartile range [IQR], 34-501). There was a strong positive correlation between ruptured oocyst number and salivary gland sporozoite load (ρ = 0.8; p<0.0001) and a weaker positive correlation between salivary gland sporozoite load and number of sporozoites expelled (ρ = 0.35; p=0.0002). In Burkina Faso, Anopheles coluzzii mosquitoes were infected by natural gametocyte carriers. Among salivary gland sporozoite positive mosquitoes, 89% (33/37) expelled sporozoites with a median of 1035 expelled sporozoites (IQR, 171-2969). Again, we observed a strong correlation between ruptured oocyst number and salivary gland sporozoite load (ρ = 0.9; p<0.0001) and a positive correlation between salivary gland sporozoite load and the number of sporozoites expelled (ρ = 0.7; p<0.0001). Several mosquitoes expelled multiple parasite clones during probing. Whilst sporozoite expelling was regularly observed from mosquitoes with low infection burdens, our findings indicate that mosquito infection burden is positively associated with the number of expelled sporozoites. Future work is required to determine the direct implications of these findings for transmission potential.
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Affiliation(s)
- Chiara Andolina
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
| | - Wouter Graumans
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
| | - Moussa Guelbeogo
- Centre National de Recherche et de Formation sur le PaludismeOuagadougouBurkina Faso
| | - Geert-Jan van Gemert
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
| | - Jordache Ramijth
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
| | - Soré Harouna
- Centre National de Recherche et de Formation sur le PaludismeOuagadougouBurkina Faso
| | - Zongo Soumanaba
- Centre National de Recherche et de Formation sur le PaludismeOuagadougouBurkina Faso
| | - Rianne Stoter
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
| | - Marga Vegte-Bolmer
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
| | - Martina Pangos
- Department of Plastic and Reconstructive Surgery, Azienda Ospedaliero Universitaria GiulianoIsontina TriesteTriesteItaly
| | - Photini Sinnis
- Department of Molecular Microbiology and Immunology, Johns HopkinsBloomberg School of Public HealthBaltimoreUnited States
| | - Katharine Collins
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
| | - Sarah G Staedke
- Liverpool School of Tropical MedicineLiverpoolUnited Kingdom
| | - Alfred B Tiono
- Centre National de Recherche et de Formation sur le PaludismeOuagadougouBurkina Faso
| | - Chris Drakeley
- Department of Immunology and Infection, London School of Hygiene and Tropical MedicineLondonUnited Kingdom
| | - Kjerstin Lanke
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
| | - Teun Bousema
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
- Department of Immunology and Infection, London School of Hygiene and Tropical MedicineLondonUnited Kingdom
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Locke E, Flores-Garcia Y, Mayer BT, MacGill RS, Borate B, Salgado-Jimenez B, Gerber MW, Mathis-Torres S, Shapiro S, King CR, Zavala F. Establishing RTS,S/AS01 as a benchmark for comparison to next-generation malaria vaccines in a mouse model. NPJ Vaccines 2024; 9:29. [PMID: 38341502 DOI: 10.1038/s41541-024-00819-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Accepted: 01/24/2024] [Indexed: 02/12/2024] Open
Abstract
New strategies are needed to reduce the incidence of malaria, and promising approaches include vaccines targeting the circumsporozoite protein (CSP). To improve upon the malaria vaccine, RTS,S/AS01, it is essential to standardize preclinical assays to measure the potency of next-generation vaccines against this benchmark. We focus on RTS,S/AS01-induced antibody responses and functional activity in conjunction with robust statistical analyses. Transgenic Plasmodium berghei sporozoites containing full-length P. falciparum CSP (tgPb-PfCSP) allow two assessments of efficacy: quantitative reduction in liver infection following intravenous challenge, and sterile protection from mosquito bite challenge. Two or three doses of RTS,S/AS01 were given intramuscularly at 3-week intervals, with challenge 2-weeks after the last vaccination. Minimal inter- and intra-assay variability indicates the reproducibility of the methods. Importantly, the range of this model is suitable for screening more potent vaccines. Levels of induced anti-CSP antibody 2A10 equivalency were also associated with activity: 105 μg/mL (95% CI: 68.8, 141) reduced liver infection by 50%, whereas 285 μg/mL (95% CI: 166, 404) is required for 50% sterile protection from mosquito bite challenge. Additionally, the liver burden model was able to differentiate between protected and non-protected human plasma samples from a controlled human malaria infection study, supporting these models' relevance and predictive capability. Comparison in animal models of CSP-based vaccine candidates to RTS,S/AS01 is now possible under well controlled conditions. Assessment of the quality of induced antibodies, likely a determinant of durability of protection in humans, should be possible using these methods.
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Affiliation(s)
- Emily Locke
- Center for Vaccine Innovation and Access, PATH, Washington, DC, 20001, USA
| | - Yevel Flores-Garcia
- Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Bryan T Mayer
- Vaccine and Infectious Disease Division, Fred Hutchison Cancer Research Center, Seattle, WA, 98109, USA
| | - Randall S MacGill
- Center for Vaccine Innovation and Access, PATH, Washington, DC, 20001, USA
| | - Bhavesh Borate
- Vaccine and Infectious Disease Division, Fred Hutchison Cancer Research Center, Seattle, WA, 98109, USA
| | - Berenice Salgado-Jimenez
- Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Monica W Gerber
- Vaccine and Infectious Disease Division, Fred Hutchison Cancer Research Center, Seattle, WA, 98109, USA
| | - Shamika Mathis-Torres
- Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Sarah Shapiro
- Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - C Richter King
- Center for Vaccine Innovation and Access, PATH, Washington, DC, 20001, USA
| | - Fidel Zavala
- Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
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Zhan Q, He Q, Tiedje KE, Day KP, Pascual M. Hyper-diverse antigenic variation and resilience to transmission-reducing intervention in falciparum malaria. medRxiv 2024:2024.02.01.24301818. [PMID: 38370729 PMCID: PMC10871444 DOI: 10.1101/2024.02.01.24301818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Intervention against falciparum malaria in high transmission regions remains challenging, with relaxation of control efforts typically followed by rapid resurgence. Resilience to intervention co-occurs with incomplete immunity, whereby children eventually become protected from severe disease but not infection and a large transmission reservoir results from high asymptomatic prevalence across all ages. Incomplete immunity relates to the vast antigenic variation of the parasite, with the major surface antigen of the blood stage of infection encoded by the multigene family known as var. Recent deep sampling of var sequences from individual isolates in northern Ghana showed that parasite population structure exhibited persistent features of high-transmission regions despite the considerable decrease in prevalence during transient intervention with indoor residual spraying (IRS). We ask whether despite such apparent limited impact, the transmission system had been brought close to a transition in both prevalence and resurgence ability. With a stochastic agent-based model, we investigate the existence of such a transition to pre-elimination with intervention intensity, and of molecular indicators informative of its approach. We show that resurgence ability decreases sharply and nonlinearly across a narrow region of intervention intensities in model simulations, and identify informative molecular indicators based on var gene sequences. Their application to the survey data indicates that the transmission system in northern Ghana was brought close to transition by IRS. These results suggest that sustaining and intensifying intervention would have pushed malaria dynamics to a slow-rebound regime with an increased probability of local parasite extinction.
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Affiliation(s)
- Qi Zhan
- Committee on Genetics, Genomics and Systems Biology, The University of Chicago; Chicago, IL, 60637, USA
| | - Qixin He
- Department of Biological Sciences, Purdue University; West Lafayette, IN, 47907, USA
| | - Kathryn E Tiedje
- Department of Microbiology and Immunology, Bio21 Institute and Peter Doherty Institute, The University of Melbourne; Melbourne, Australia
| | - Karen P Day
- Department of Microbiology and Immunology, Bio21 Institute and Peter Doherty Institute, The University of Melbourne; Melbourne, Australia
| | - Mercedes Pascual
- Department of Biology, New York University; New York, NY, 10012, USA
- Department of Environmental Studies, New York University; New York, NY, 10012, USA
- Santa Fe Institute; Santa Fe, NM, 87501, USA
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de Roos AM, He Q, Pascual M. An immune memory-structured SIS epidemiological model for hyperdiverse pathogens. Proc Natl Acad Sci U S A 2023; 120:e2218499120. [PMID: 37910552 PMCID: PMC10636369 DOI: 10.1073/pnas.2218499120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 10/02/2023] [Indexed: 11/03/2023] Open
Abstract
A hyperdiverse class of pathogens of humans and wildlife, including the malaria parasite Plasmodium falciparum, relies on multigene families to encode antigenic variation. As a result, high (asymptomatic) prevalence is observed despite high immunity in local populations under high-transmission settings. The vast diversity of "strains" and genes encoding this variation challenges the application of established models for the population dynamics of such infectious diseases. Agent-based models have been formulated to address theory on strain coexistence and structure, but their complexity can limit application to gain insights into population dynamics. Motivated by P. falciparum malaria, we develop an alternative formulation in the form of a structured susceptible-infected-susceptible population model in continuous time, where individuals are classified not only by age, as is standard, but also by the diversity of parasites they have been exposed to and retain in their specific immune memory. We analyze the population dynamics and bifurcation structure of this system of partial-differential equations, showing the existence of alternative steady states and an associated tipping point with transmission intensity. We attribute the critical transition to the positive feedback between parasite genetic diversity and force of infection. Basins of attraction show that intervention must drastically reduce diversity to prevent a rebound to high infection levels. Results emphasize the importance of explicitly considering pathogen diversity and associated specific immune memory in the population dynamics of hyperdiverse epidemiological systems. This statement is discussed in a more general context for ecological competition systems with hyperdiverse trait spaces.
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Affiliation(s)
- André M. de Roos
- Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam1090 GE, The Netherlands
- Santa Fe Institute, Santa Fe, NM87501
| | - Qixin He
- Department of Biological Sciences, Purdue University, West Lafayette, IN47907
| | - Mercedes Pascual
- Santa Fe Institute, Santa Fe, NM87501
- Department of Ecology and Evolution, The University of Chicago, Chicago, IL60637
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5
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Oke CE, Reece SE, Schneider P. Testing a non-destructive assay to track Plasmodium sporozoites in mosquitoes over time. Parasit Vectors 2023; 16:401. [PMID: 37925480 PMCID: PMC10625196 DOI: 10.1186/s13071-023-06015-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 10/14/2023] [Indexed: 11/06/2023] Open
Abstract
BACKGROUND The extrinsic incubation period (EIP), defined as the time it takes for malaria parasites in a mosquito to become infectious to a vertebrate host, is one of the most influential parameters for malaria transmission but remains poorly understood. The EIP is usually estimated by quantifying salivary gland sporozoites in subsets of mosquitoes, which requires terminal sampling. However, assays that allow repeated sampling of individual mosquitoes over time could provide better resolution of the EIP. METHODS We tested a non-destructive assay to quantify sporozoites of two rodent malaria species, Plasmodium chabaudi and Plasmodium berghei, expelled throughout 24-h windows, from sugar-soaked feeding substrates using quantitative-PCR. RESULTS The assay is able to quantify sporozoites from sugar-soaked feeding substrates, but the prevalence of parasite-positive substrates was low. Various methods were attempted to increase the detection of expelled parasites (e.g. running additional technical replicates; using groups rather than individual mosquitoes), but these did not increase the detection rate, suggesting that expulsion of sporozoites is variable and infrequent. CONCLUSIONS We reveal successful detection of expelled sporozoites from sugar-soaked feeding substrates. However, investigations of the biological causes underlying the low detection rate of sporozoites (e.g. mosquito feeding behaviour, frequency of sporozoite expulsion or sporozoite clumping) are needed to maximise the utility of using non-destructive assays to quantify sporozoite dynamics. Increasing detection rates will facilitate the detailed investigation on infection dynamics within mosquitoes, which is necessary to explain the highly variable EIP of Plasmodium and to improve understanding of malaria transmission dynamics.
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Affiliation(s)
- Catherine E Oke
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, UK.
| | - Sarah E Reece
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Petra Schneider
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
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Kwapong SS, Asare KK, Kusi KA, Pappoe F, Ndam N, Tahar R, Poinsignon A, Amoah LE. Mosquito bites and stage-specific antibody responses against Plasmodium falciparum in southern Ghana. Malar J 2023; 22:126. [PMID: 37061695 PMCID: PMC10105943 DOI: 10.1186/s12936-023-04557-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Accepted: 04/07/2023] [Indexed: 04/17/2023] Open
Abstract
BACKGROUND The human host elicits specific immune responses after exposure to various life stages of the malaria parasite as well as components of mosquito saliva injected into the host during a mosquito bite. This study describes differences in IgG responses against antigens derived from the sporozoite (PfCSP), asexual stage parasite (PfEBA175) and the gametocyte (Pfs230), in addition to an Anopheles gambiae salivary gland antigen (gSG6-P1), in two communities in Ghana with similar blood stage malaria parasite prevalence. METHODS This study used archived plasma samples collected from an earlier cross-sectional study that enrolled volunteers aged from 6 months to 70 years from Simiw, peri-urban community (N = 347) and Obom, rural community (N = 291). An archived thick and thin blood smear for microscopy was used for the estimation of Plasmodium parasite density and species and DNA extraction from blood spots and P. falciparum confirmation was performed using PCR. This study used the stored plasma samples to determine IgG antibody levels to P. falciparum and Anopheles salivary antigens using indirect ELISA. RESULTS Individuals from Simiw had significantly higher levels of IgG against mosquito gSG6-P1 [median (95%CI)] [2.590 (2.452-2.783) ng/mL] compared to those from Obom [2.119 (1.957-2.345) ng/mL], p < 0.0001. Both IgG responses against Pfs230proC (p = 0.0006), and PfCSP (p = 0.002) were significantly lower in volunteers from Simiw compared to the participants from Obom. The seroprevalence of PfEBA-175.5R (p = 0.8613), gSG6-P1 (p = 0.0704), PfCSP (p = 0.7798) IgG were all similar in Obom and Simiw. However, Pfs230 seroprevalence was significantly higher at Obom compared to Simiw (p = 0.0006). Spearman correlation analysis showed no significant association between IgG responses against gSG6-P1, PfCSP, Pfs230proC and PfEBA-175.5R and parasite density at both Obom and Simiw (p > 0.05). CONCLUSION In conclusion, the study showed that participants from Simiw had higher concentrations of circulating gSG6-P1 IgG antibodies but lower concentrations of P. falciparum antibodies, PfCSP IgG and Pfs230proC IgG compared to participants from Obom.
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Affiliation(s)
- Sebastian Shine Kwapong
- Department of Microbiology and Immunology, School of Medical Sciences, University of Cape Coast, Cape Coast, Ghana
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Kwame Kumi Asare
- Department of Biomedical Science, School of Allied Health Sciences, University of Cape Coast, Cape Coast, Ghana
- Biomedical and Clinical Research Centre, College of Allied Health Sciences, University of Cape Coast, Cape Coast, Ghana
| | - Kwadwo Asamoah Kusi
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Faustina Pappoe
- Department of Microbiology and Immunology, School of Medical Sciences, University of Cape Coast, Cape Coast, Ghana
| | - Nicaise Ndam
- MERIT, IRD, Université de Paris Cité, 75006, Paris, France
| | - Rachida Tahar
- MERIT, IRD, Université de Paris Cité, 75006, Paris, France
| | - Anne Poinsignon
- IRD, CNRS, MIVEGEC, University of Montpellier, 34000, Montpellier, France
| | - Linda Eva Amoah
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana.
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Tottey S, Shoji Y, Mark Jones R, Musiychuk K, Chichester JA, Miura K, Zhou L, Lee SM, Plieskatt J, Wu Y, Long CA, Streatfield SJ, Yusibov V. Engineering of a plant-produced virus-like particle to improve the display of the Plasmodium falciparum Pfs25 antigen and transmission-blocking activity of the vaccine candidate. Vaccine 2023; 41:938-944. [PMID: 36585278 PMCID: PMC9888754 DOI: 10.1016/j.vaccine.2022.12.048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 12/04/2022] [Accepted: 12/19/2022] [Indexed: 12/29/2022]
Abstract
Malaria kills around 409,000 people a year, mostly children under the age of five. Malaria transmission-blocking vaccines work to reduce malaria prevalence in a community and have the potential to be part of a multifaceted approach required to eliminate the parasites causing the disease. Pfs25 is a leading malaria transmission-blocking antigen and has been successfully produced in a plant expression system as both a subunit vaccine and as a virus-like particle. This study demonstrates an improved version of the virus-like particle antigen display molecule by eliminating known protease sites from the prior A85 variant. This re-engineered molecule, termed B29, displays three times the number of Pfs25 antigens per virus-like particle compared to the original Pfs25 virus-like particle. An improved purification scheme was also developed, resulting in a substantially higher yield and improved purity. The molecule was evaluated in a mouse model and found to induce improved transmission-blocking activity at lower doses and longer durations than the original molecule.
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Affiliation(s)
- Stephen Tottey
- Fraunhofer USA Center Mid-Atlantic, Biotechnology Division, 9 Innovation Way, Newark, DE 19711, USA
| | - Yoko Shoji
- Fraunhofer USA Center Mid-Atlantic, Biotechnology Division, 9 Innovation Way, Newark, DE 19711, USA
| | - R Mark Jones
- Fraunhofer USA Center Mid-Atlantic, Biotechnology Division, 9 Innovation Way, Newark, DE 19711, USA
| | - Konstantin Musiychuk
- Fraunhofer USA Center Mid-Atlantic, Biotechnology Division, 9 Innovation Way, Newark, DE 19711, USA
| | - Jessica A Chichester
- Fraunhofer USA Center Mid-Atlantic, Biotechnology Division, 9 Innovation Way, Newark, DE 19711, USA
| | - Kazutoyo Miura
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Rockville, MD 20852, USA
| | - Luwen Zhou
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Rockville, MD 20852, USA
| | - Shwu-Maan Lee
- PATH's Malaria Vaccine Initiative, Washington, DC 20001, USA
| | | | - Yimin Wu
- PATH's Malaria Vaccine Initiative, Washington, DC 20001, USA
| | - Carole A Long
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Rockville, MD 20852, USA
| | - Stephen J Streatfield
- Fraunhofer USA Center Mid-Atlantic, Biotechnology Division, 9 Innovation Way, Newark, DE 19711, USA.
| | - Vidadi Yusibov
- Fraunhofer USA Center Mid-Atlantic, Biotechnology Division, 9 Innovation Way, Newark, DE 19711, USA
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Broen K, Dickens J, Trangucci R, Ogwang MD, Tenge CN, Masalu N, Reynolds SJ, Kawira E, Kerchan P, Were PA, Kuremu RT, Wekesa WN, Kinyera T, Otim I, Legason ID, Nabalende H, Buller ID, Ayers LW, Bhatia K, Biggar RJ, Goedert JJ, Wilson ML, Mbulaiteye SM, Zelner J. Burkitt lymphoma risk shows geographic and temporal associations with Plasmodium falciparum infections in Uganda, Tanzania, and Kenya. Proc Natl Acad Sci U S A 2023; 120:e2211055120. [PMID: 36595676 DOI: 10.1073/pnas.2211055120] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Endemic Burkitt lymphoma (eBL) is a pediatric cancer coendemic with malaria in sub-Saharan Africa, suggesting an etiological link between them. However, previous cross-sectional studies of limited geographic areas have not found a convincing association. We used spatially detailed data from the Epidemiology of Burkitt Lymphoma in East African Children and Minors (EMBLEM) study to assess this relationship. EMBLEM is a case-control study of eBL from 2010 through 2016 in six regions of Kenya, Uganda, and Tanzania. To measure the intensity of exposure to the malaria parasite, Plasmodium falciparum, among children in these regions, we used high-resolution spatial data from the Malaria Atlas Project to estimate the annual number of P. falciparum infections from 2000 through 2016 for each of 49 districts within the study region. Cumulative P. falciparum exposure, calculated as the sum of annual infections by birth cohort, varied widely, with a median of 47 estimated infections per child by age 10, ranging from 4 to 315 infections. eBL incidence increased 39% for each 100 additional lifetime P. falciparum infections (95% CI: 6.10 to 81.04%) with the risk peaking among children aged 5 to 11 and declining thereafter. Alternative models using estimated annual P. falciparum infections 0 to 10 y before eBL onset were inconclusive, suggesting that eBL risk is a function of cumulative rather than recent cross-sectional exposure. Our findings provide population-level evidence that eBL is a phenotype related to heavy lifetime exposure to P. falciparum malaria and support emphasizing the link between malaria and eBL.
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Van Yperen J, Campillo-Funollet E, Inkpen R, Memon A, Madzvamuse A. A hospital demand and capacity intervention approach for COVID-19. PLoS One 2023; 18:e0283350. [PMID: 37134085 PMCID: PMC10156009 DOI: 10.1371/journal.pone.0283350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Accepted: 03/06/2023] [Indexed: 05/04/2023] Open
Abstract
The mathematical interpretation of interventions for the mitigation of epidemics in the literature often involves finding the optimal time to initiate an intervention and/or the use of the number of infections to manage impact. Whilst these methods may work in theory, in order to implement effectively they may require information which is not likely to be available in the midst of an epidemic, or they may require impeccable data about infection levels in the community. In reality, testing and cases data can only be as good as the policy of implementation and the compliance of the individuals, which implies that accurately estimating the levels of infections becomes difficult or complicated from the data that is provided. In this paper, we demonstrate a different approach to the mathematical modelling of interventions, not based on optimality or cases, but based on demand and capacity of hospitals who have to deal with the epidemic on a day to day basis. In particular, we use data-driven modelling to calibrate a susceptible-exposed-infectious-recovered-died type model to infer parameters that depict the dynamics of the epidemic in several regions of the UK. We use the calibrated parameters for forecasting scenarios and understand, given a maximum capacity of hospital healthcare services, how the timing of interventions, severity of interventions, and conditions for the releasing of interventions affect the overall epidemic-picture. We provide an optimisation method to capture when, in terms of healthcare demand, an intervention should be put into place given a maximum capacity on the service. By using an equivalent agent-based approach, we demonstrate uncertainty quantification on the likelihood that capacity is not breached, by how much if it does, and the limit on demand that almost guarantees capacity is not breached.
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Affiliation(s)
- James Van Yperen
- Department of Mathematics, School of Mathematical and Physical Sciences, University of Sussex, Brighton, United Kingdom
| | - Eduard Campillo-Funollet
- Department of Mathematics, School of Mathematical, Statistical and Actuarial Sciences, University of Kent, Canterbury, United Kingdom
- Department of Mathematics and Statistics, Lancaster University, Lancaster, United Kingdom
| | - Rebecca Inkpen
- Department of Mathematics, School of Mathematical and Physical Sciences, University of Sussex, Brighton, United Kingdom
| | - Anjum Memon
- Department of Primary Care and Public Health, Brighton and Sussex Medical School, Brighton, United Kingdom
| | - Anotida Madzvamuse
- Department of Mathematics, School of Mathematical and Physical Sciences, University of Sussex, Brighton, United Kingdom
- Department of Mathematics, University of Johannesburg, Johannesburg, South Africa
- Department of Mathematics, University of British Columbia, Vancouver, Canada
- Department of Mathematics, University of Pretoria, Pretoria, South Africa
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10
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Kamana E, Bai D, Brown HE, Zhao J. The malaria transmission in Anhui province China. Infect Dis Model 2023; 8:1-10. [PMID: 36582746 DOI: 10.1016/j.idm.2022.11.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 11/22/2022] [Indexed: 11/28/2022] Open
Abstract
Plasmodium vivax and Plasmodium falciparum cases have opposite trends in Anhui China in the past decade. Long term and seasonal trends in the transmission rate of P. falciparum in Africa has been well studied, however that of P. vivax transmitted by Anopheles sinensis in China has not been investigated. There is a lot of work on the relationship between P. vivax cases and climatic factors in China, with sometimes contradicting results. However, how climatic factors affect transmission rate of P. vivax in China is unknown. We used Anhui province as an example to analyze the recent transmission dynamics where two types of malaria have been reported with differing etiologies. We examined breakpoints of the P. vivax and P. falciparum malaria long term dynamics in the recent decade. For locally transmitted P. vivax malaria, we analyzed the transmission rate and its seasonality using the combined human and mosquitos SIR-SI model with time-varied mosquito biting rate. We identified the effects of meteorological factors on the seasonality in transmission rate using a GAM model. For the imported P. falciparum malaria, we analyzed the potential reason for the observed increase in cases. The breakpoints of P. vivax and P. falciparum dynamics happened in a same year, 2010. The seasonality in the transmission rate of P. vivax malaria was high (42.4%) and was linearly associated with temperature and nonlinearly with rainfall. The abrupt increase in imported P. falciparum cases after the breakpoint was significantly related to the increased annual Chinese investment in Africa. Under the conditions of the existing vectors of malaria, long-term trends in climatic factors, and increasing trend in migration to/from endemic areas and imported malaria cases, we should be cautious of the possibility of the reestablishment of malaria in regions where it has been eliminated or the establishment of other vector-borne diseases.
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11
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Nair S, Li X, Nkhoma SC, Anderson T. Fitness Costs of pfhrp2 and pfhrp3 Deletions Underlying Diagnostic Evasion in Malaria Parasites. J Infect Dis 2022; 226:1637-1645. [PMID: 35709327 PMCID: PMC10205895 DOI: 10.1093/infdis/jiac240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 06/14/2022] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Rapid diagnostic tests based on detection of histidine-rich proteins (HRPs) are widely used for malaria diagnosis, but parasites carrying pfhrp deletions can evade detection and are increasing in frequency in some countries. Models aim to predict conditions under which pfhrp2 and/or pfhrp3 deletions will increase, but a key parameter-the fitness cost of deletions-is unknown. METHODS We removed pfhrp2 and/or pfhrp3 from a Malawian parasite clone using gene editing approaches) and measured fitness costs by conducting pairwise competition experiments. RESULTS We observed significant fitness costs of 0.087 ± 0.008 (1 standard error) per asexual cycle for pfhrp2 deletion and 0.113 ± 0.008 for the pfhrp2/3 double deletion, relative to the unedited progenitor parasite. Selection against deletions is strong and comparable to that resulting from drug resistance mutations. CONCLUSIONS Prior modeling suggested that diagnostic selection may drive increased frequency of pfhrp deletions only when fitness costs are mild. Our experiments show that costs of pfhrp deletions are higher than these thresholds, but modeling and empirical results can be reconciled if the duration of infection is short. These results may inform future modeling to understand why pfhrp2/3 deletions are increasing in some locations (Ethiopia and Eritrea) but not in others (Mekong region).
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Affiliation(s)
- Shalini Nair
- Disease Intervention and Prevention Program, Texas Biomedical Research Institute, San Antonio, Texas, USA
| | - Xue Li
- Disease Intervention and Prevention Program, Texas Biomedical Research Institute, San Antonio, Texas, USA
| | - Standwell C Nkhoma
- BEI Resources, American Type Culture Collection, Manassas, Virginia, USA
| | - Tim Anderson
- Disease Intervention and Prevention Program, Texas Biomedical Research Institute, San Antonio, Texas, USA
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12
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Abate A, Kedir S, Bose M, Hassen J, Dembele L, Golassa L. Infectivity of Symptomatic Patients and Their Contribution for Infectiousness of Mosquitoes following a Membrane Feeding Assay in Ethiopia. Microbiol Spectr 2022; 10:e0062822. [PMID: 36066239 PMCID: PMC9602676 DOI: 10.1128/spectrum.00628-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 08/05/2022] [Indexed: 12/30/2022] Open
Abstract
The membrane feeding assay is widely used to evaluate the efficacy of transmission-blocking interventions (TBIs) and identify the reservoir of malaria. This study aimed to determine the infectivity of blood meals from symptomatic Plasmodium-infected patients to an Anopheles arabiensis colony in Ethiopia. A membrane feeding assay was conducted on a total of 63 Plasmodium falciparum- and/or Plasmodium vivax-infected clinical patients in East Shoa Zone, Ethiopia. Detection of P. falciparum and P. vivax in blood samples was done using microscopy. Mosquito infection rates were determined by dissection of mosquitoes' midguts, while mosquito infectiousness was observed by dissection of their salivary glands. The proportion of infectious symptomatic patients was 68.3% (43/63). Using the chi-square or Fisher's exact test, the oocyst infection levels were higher among patients infected with P. vivax, females, and rural residents. Nearly 57% (56.7%, 17/30) of assays produced sporozoites in the salivary glands of mosquitoes. Both oocyst and sporozoite infection rates had positive correlations with parasitemia and gametocytemia. High infectiousness of symptomatic patients was observed, with a greater proportion of infectious mosquitoes per assay. Demonstrating oocyst infection in the mosquitoes might confirm estimates of the infectiousness of mosquitoes, although some of the oocyst-infected mosquitoes failed to produce sporozoites. IMPORTANCE Malaria remains one of the most devastating infectious diseases globally, and transmission-blocking activities are needed. Plasmodium transmission from human to mosquitoes is poorly studied, particularly in endemic countries, and the membrane feeding assay allows it to be determined. In this study, we demonstrated human infectious reservoirs of malaria. Moreover, the effect of Plasmodium-infected patients on the infectiousness of mosquitoes was also observed. These findings are therefore important for designing future evaluation of transmission-blocking interventions that will support the malaria elimination program.
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Affiliation(s)
- Andargie Abate
- Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia
- College of Medicine and Health Sciences, Bahir Dar University, Bahir Dar, Ethiopia
| | - Soriya Kedir
- Adama Regional Laboratory, Oromia Region Health Bureau, Adama, Ethiopia
| | - Mitiku Bose
- Adama Regional Laboratory, Oromia Region Health Bureau, Adama, Ethiopia
| | - Jifar Hassen
- Adama Science and Technology University, Adama, Ethiopia
| | - Laurent Dembele
- Université des Sciences, des Techniques et des Technologies de Bamako (USTTB), Malaria Research and Training Center (MRTC), Bamako, Mali
| | - Lemu Golassa
- Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia
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13
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Ripp J, Smyrnakou X, Neuhoff M, Hentzschel F, Frischknecht F. Phosphorylation of myosin A regulates gliding motility and is essential for
Plasmodium
transmission. EMBO Rep 2022; 23:e54857. [PMID: 35506479 PMCID: PMC9253774 DOI: 10.15252/embr.202254857] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 04/06/2022] [Accepted: 04/08/2022] [Indexed: 11/30/2022] Open
Abstract
Malaria‐causing parasites rely on an actin–myosin‐based motor for the invasion of different host cells and tissue traversal in mosquitoes and vertebrates. The unusual myosin A of Plasmodium spp. has a unique N‐terminal extension, which is important for red blood cell invasion by P. falciparum merozoites in vitro and harbors a phosphorylation site at serine 19. Here, using the rodent‐infecting P. berghei we show that phosphorylation of serine 19 increases ookinete but not sporozoite motility and is essential for efficient transmission of Plasmodium by mosquitoes as S19A mutants show defects in mosquito salivary gland entry. S19A along with E6R mutations slow ookinetes and salivary gland sporozoites in both 2D and 3D environments. In contrast to data from purified proteins, both E6R and S19D mutations lower force generation by sporozoites. Our data show that the phosphorylation cycle of S19 influences parasite migration and force generation and is critical for optimal migration of parasites during transmission from and to the mosquito.
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Affiliation(s)
- Johanna Ripp
- Integrative Parasitology Center for Infectious Diseases University of Heidelberg Medical School Heidelberg Germany
| | - Xanthoula Smyrnakou
- Integrative Parasitology Center for Infectious Diseases University of Heidelberg Medical School Heidelberg Germany
| | - Marie‐Therese Neuhoff
- Integrative Parasitology Center for Infectious Diseases University of Heidelberg Medical School Heidelberg Germany
| | - Franziska Hentzschel
- Integrative Parasitology Center for Infectious Diseases University of Heidelberg Medical School Heidelberg Germany
- German Center for Infection Research DZIF Partner Site Heidelberg Heidelberg Germany
| | - Friedrich Frischknecht
- Integrative Parasitology Center for Infectious Diseases University of Heidelberg Medical School Heidelberg Germany
- German Center for Infection Research DZIF Partner Site Heidelberg Heidelberg Germany
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14
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Ramjith J, Alkema M, Bradley J, Dicko A, Drakeley C, Stone W, Bousema T. Quantifying Reductions in Plasmodium falciparum Infectivity to Mosquitos: A Sample Size Calculator to Inform Clinical Trials on Transmission-Reducing Interventions. Front Immunol 2022; 13:899615. [PMID: 35720362 PMCID: PMC9205189 DOI: 10.3389/fimmu.2022.899615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 05/10/2022] [Indexed: 11/13/2022] Open
Abstract
Malaria transmission depends on the presence of mature Plasmodium transmission stages (gametocytes) that may render blood-feeding Anopheles mosquitos infectious. Transmission-blocking antimalarial drugs and vaccines can prevent transmission by reducing gametocyte densities or infectivity to mosquitos. Mosquito infection outcomes are thereby informative biological endpoints of clinical trials with transmission blocking interventions. Nevertheless, trials are often primarily designed to determine intervention safety; transmission blocking efficacy is difficult to incorporate in sample size considerations due to variation in infection outcomes and considerable inter-study variation. Here, we use clinical trial data from studies in malaria naive and naturally exposed study participants to present an online sample size calculator tool. This sample size calculator allows studies to be powered to detect reductions in the proportion of infected mosquitos or infection burden (oocyst density) in mosquitos. The utility of this online tool is illustrated using trial data with transmission blocking malaria drugs.
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Affiliation(s)
- Jordache Ramjith
- Radboud Institute for Molecular Life Sciences, Department of Medical Microbiology, Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen, Netherlands.,Department for Health Evidence, Biostatistics Research Group, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - Manon Alkema
- Radboud Institute for Molecular Life Sciences, Department of Medical Microbiology, Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen, Netherlands
| | - John Bradley
- Medical Research Council (MRC) International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Alassane Dicko
- Malaria Research and Training Centre, Faculty of Pharmacy and Faculty of Medicine and Dentistry, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Chris Drakeley
- Medical Research Council (MRC) International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Will Stone
- Medical Research Council (MRC) International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Teun Bousema
- Radboud Institute for Molecular Life Sciences, Department of Medical Microbiology, Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen, Netherlands
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15
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Sturm A, Vos MW, Henderson R, Eldering M, Koolen KMJ, Sheshachalam A, Favia G, Samby K, Herreros E, Dechering KJ. Barcoded Asaia bacteria enable mosquito in vivo screens and identify novel systemic insecticides and inhibitors of malaria transmission. PLoS Biol 2021; 19:e3001426. [PMID: 34928952 PMCID: PMC8726507 DOI: 10.1371/journal.pbio.3001426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 01/04/2022] [Accepted: 12/03/2021] [Indexed: 11/18/2022] Open
Abstract
This work addresses the need for new chemical matter in product development for control of pest insects and vector-borne diseases. We present a barcoding strategy that enables phenotypic screens of blood-feeding insects against small molecules in microtiter plate-based arrays and apply this to discovery of novel systemic insecticides and compounds that block malaria parasite development in the mosquito vector. Encoding of the blood meals was achieved through recombinant DNA-tagged Asaia bacteria that successfully colonised Aedes and Anopheles mosquitoes. An arrayed screen of a collection of pesticides showed that chemical classes of avermectins, phenylpyrazoles, and neonicotinoids were enriched for compounds with systemic adulticide activity against Anopheles. Using a luminescent Plasmodium falciparum reporter strain, barcoded screens identified 48 drug-like transmission-blocking compounds from a 400-compound antimicrobial library. The approach significantly increases the throughput in phenotypic screening campaigns using adult insects and identifies novel candidate small molecules for disease control. This study presents a barcoding strategy that enables high-throughput phenotypic screens of blood-feeding insects against small molecules in microtiter plate-based arrays and applies this to the discovery of novel systemic insecticides and compounds that block malaria parasite development in the mosquito vector.
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16
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Shibeshi W, Bagchus W, Yalkinoglu Ö, Tappert A, Engidawork E, Oeuvray C. Reproducibility of malaria sporozoite challenge model in humans for evaluating efficacy of vaccines and drugs: a systematic review. BMC Infect Dis 2021; 21:1274. [PMID: 34930178 PMCID: PMC8686662 DOI: 10.1186/s12879-021-06953-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 12/06/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The development of novel malaria vaccines and antimalarial drugs is limited partly by emerging challenges to conduct field trials in malaria endemic areas, including unknown effects of existing immunity and a reported fall in malaria incidence. As a result, Controlled Human Malaria Infection (CHMI) has become an important approach for accelerated development of malarial vaccines and drugs. We conducted a systematic review of the literature to establish aggregate evidence on the reproducibility of a malaria sporozoite challenge model. METHODS A systematic review of research articles published between 1990 and 2018 on efficacy testing of malaria vaccines and drugs using sporozoite challenge and sporozoite infectivity studies was conducted using Pubmed, Scopus, Embase and Cochrane Library, ClinicalTrials.gov and Trialtrove. The inclusion criteria were randomized and non-randomized, controlled or open-label trials using P. falciparum or P. vivax sporozoite challenges. The data were extracted from articles using standardized data extraction forms and descriptive analysis was performed for evidence synthesis. The endpoints considered were infectivity, prepatent period, parasitemia and safety of sporozoite challenge. RESULTS Seventy CHMI trials conducted with a total of 2329 adult healthy volunteers were used for analysis. CHMI was induced by bites of mosquitoes infected with P. falciparum or P. vivax in 52 trials and by direct venous inoculation of P. falciparum sporozoites (PfSPZ challenge) in 18 trials. Inoculation with P. falciparum-infected mosquitoes produced 100% infectivity in 40 studies and the mean/median prepatent period assessed by thick blood smear (TBS) microscopy was ≤ 12 days in 24 studies. On the other hand, out of 12 infectivity studies conducted using PfSPZ challenge, 100% infection rate was reproduced in 9 studies with a mean or median prepatent period of 11 to 15.3 days as assessed by TBS and 6.8 to 12.6 days by PCR. The safety profile of P. falciparum and P.vivax CHMI was characterized by consistent features of malaria infection. CONCLUSION There is ample evidence on consistency of P. falciparum CHMI models in terms of infectivity and safety endpoints, which supports applicability of CHMI in vaccine and drug development. PfSPZ challenge appears more feasible for African trials based on current evidence of safety and efficacy.
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Affiliation(s)
- Workineh Shibeshi
- Department of Pharmacology and Clinical Pharmacy, School of Pharmacy, College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia.
- Global Health Institute of Merck, Ares Trading S.A., A subsidiary of Merck KGaA, Darmstadt, Germany.
| | - Wilhelmina Bagchus
- Translational Medicine, Merck Serono S.A., An Affiliate of Merck KGaA, Darmstadt, Germany
| | - Özkan Yalkinoglu
- Translational Medicine, Merck Healthcare KGaA, Darmstadt, Germany
| | - Aliona Tappert
- Global Patient Safety, Merck Healthcare KGaA, Darmstadt, Germany
| | - Ephrem Engidawork
- Department of Pharmacology and Clinical Pharmacy, School of Pharmacy, College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia
| | - Claude Oeuvray
- Global Health Institute of Merck, Ares Trading S.A., A subsidiary of Merck KGaA, Darmstadt, Germany
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17
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Efunshile AM, Ojide CK, Igwe D, Onyia B, Jokelainen P, Robertson LJ. Mosquito control at a tertiary teaching hospital in Nigeria. Infect Prev Pract 2021; 3:100172. [PMID: 34604733 PMCID: PMC8473772 DOI: 10.1016/j.infpip.2021.100172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 09/01/2021] [Indexed: 11/25/2022] Open
Abstract
Background Mosquitoes are vectors of numerous diseases, including malaria and yellow fever. Mosquito control is therefore a priority in many countries, especially in healthcare settings. Here we investigated the opinions of patients and staff regarding mosquito control at a hospital in Nigeria, and also gathered data on mosquito-control measures in this setting. Methods We conducted a cross-sectional questionnaire study of staff and patients and an observational approach to obtain data on mosquito-control measures used at a tertiary teaching hospital in Abakaliki, Nigeria. Discussion Both staff (N=517) and patients (N=302) reported experiencing more mosquito bites at the hospital than elsewhere. As well as contributing to discomfort, this exposure may put hospital staff and patients at risk of mosquito-borne infections. Complaints from patients about mosquitoes were reported by over 90% of staff, and over 50% of staff respondents were aware of patient discharge against medical advice due to mosquitoes. The most common control method was killing mosquitoes by hand. We observed a lack of door screens in all wards, window screens were absent or torn, and most beds did not have nets. In the children's wards none of the beds had nets. Conclusions Current measures against mosquitoes in this hospital appeared inadequate, and healthcare staff and hospital patients may be at increased risk of mosquito-borne infections. Mosquito control in the hospital requires attention, and the needs for improvement in mosquito control in the healthcare setting more widely should be evaluated and addressed.
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Affiliation(s)
- Akinwale M Efunshile
- Department of Medical Microbiology, Ebonyi State University, Abakaliki, Nigeria.,Department of Medical Microbiology, Alex Ekweme Federal University Teaching Hospital, Abakaliki, Nigeria
| | - Chiedozie Kingsley Ojide
- Department of Medical Microbiology, Alex Ekweme Federal University Teaching Hospital, Abakaliki, Nigeria
| | - Daniel Igwe
- Department of Medical Microbiology, Alex Ekweme Federal University Teaching Hospital, Abakaliki, Nigeria
| | - Blessing Onyia
- Department of Medical Microbiology, Alex Ekweme Federal University Teaching Hospital, Abakaliki, Nigeria
| | - Pikka Jokelainen
- Laboratory of Parasitology, Department of Bacteria, Parasites & Fungi, Infectious Disease Preparedness, Statens Serum Institut, Artillerivej 5, Copenhagen S, 2300, Denmark
| | - Lucy J Robertson
- Parasitology, Department of Paraclinical Science, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, PO box 5003, Ås, 1432, Norway
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18
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Gizaw Z, Engdaw GT, Nigusie A, Gebrehiwot M, Destaw B. Human Ectoparasites Are Highly Prevalent in the Rural Communities of Northwest Ethiopia: A Community-Based Cross-Sectional Study. Environ Health Insights 2021; 15:11786302211034463. [PMID: 34366670 PMCID: PMC8299896 DOI: 10.1177/11786302211034463] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Accepted: 06/30/2021] [Indexed: 06/13/2023]
Abstract
BACKGROUND Ectoparasites are organisms which inhabit the skin or outgrowths of the skin of another organism (the host). Many ectoparasites are known to be vectors of pathogens, which the parasites typically transmit to hosts. Though, ectoparasites are common in the vulnerable groups and economically disadvantaged communities, there is limited evidence on its magnitude in Ethiopia. This community-based cross-sectional study was, therefore, conducted to assess the prevalence and associated factors of ectoparasites in the rural communities of northwest Ethiopia. METHODS A community-based cross-sectional study design with structured observation was conducted among 1191 randomly selected rural households in northwest Ethiopia in May 2016. Data were collected using structured interviewer administered interview questionnaire and structured observation checklist. Prevalence of human ectoparasites in the rural communities was defined as the presence of one or more lice, fleas, bed bugs, mites, and ticks and the presence of these ectoparasites were observed by trained environmental health experts. Multivariable binary logistic regression analysis was used to identify variables associated with prevalence of ectoparasites on the basis of adjusted odds ratio (AOR) with 95% confidence interval (CI) and P values <.05. RESULTS Of a total of 1191 rural households, human or hair lice were observed in one or more of the family members in 186 (15.6%) rural households. Similarly, fleas were observed in more than half, 609 (51.1%) of rural households and bed bugs were observed in 441 (37%) rural households. Furthermore, mites and ticks were reported in 113 (9.5%) and 130 (10.9%) of the households respectively. Accordingly, one or more ectoparasites were observed in 865 of 1191 rural households. The presence of one or more ectoparasites was, therefore, found to be 72.6% (95% CI = 70%-75.1%). The prevalence of ectoparasites was statistically associated with educational status of the female head being not educated (AOR = 1.476, 95% CI = 1.001, 2.177) and absence close supervision by health extension workers (AOR = 2.151, 95% CI = 1.205, 3.843). CONCLUSION The prevalence of one or more ectoparasites was high in the rural communities of northwest Ethiopia. The high prevalence was associated with education status of the female head and close supervision of households by health extension workers. Disseminating health information about intervention strategies of ectoparasites and closely supervising the rural households need to be considered.
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Affiliation(s)
- Zemichael Gizaw
- Department of Environmental and Occupational Health and Safety, Institute of Public Health, College of Medicine and Health Sciences, University of Gondar, Gondar, Ethiopia
| | - Garedew Tadege Engdaw
- Department of Environmental and Occupational Health and Safety, Institute of Public Health, College of Medicine and Health Sciences, University of Gondar, Gondar, Ethiopia
| | - Adane Nigusie
- Department of Health Education and Behavioral Sciences, Institute of Public Health, College of Medicine and Health Sciences, University of Gondar, Gondar, Ethiopia
| | - Mulat Gebrehiwot
- Department of Environmental and Occupational Health and Safety, Institute of Public Health, College of Medicine and Health Sciences, University of Gondar, Gondar, Ethiopia
| | - Bikes Destaw
- Department of Environmental and Occupational Health and Safety, Institute of Public Health, College of Medicine and Health Sciences, University of Gondar, Gondar, Ethiopia
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Kalbskopf V, Ahrén D, Valkiūnas G, Palinauskas V, Hellgren O. Shifts in gene expression variability in the blood-stage of Plasmodium relictum. Gene 2021; 792:145723. [PMID: 34019936 DOI: 10.1016/j.gene.2021.145723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 05/12/2021] [Accepted: 05/14/2021] [Indexed: 11/22/2022]
Abstract
Avian malaria is a common and widespread disease of birds caused by a diverse group of pathogens of the genera Plasmodium. We investigated the transcriptomal profiles of one of the most common species, Plasmodium relictum, lineage SGS1, at multiple timepoints during the blood stages of the infection under experimental settings. The parasite showed well separated overall transcriptome profiles between day 8 and 20 after the infection, shown by well separated PCA profiles. Moreover, gene expression becomes more heterogenous within the experimental group late in the infection, either due to adaptations to individual differences between the experimental hosts, or due to desynchronisation of the life-cycle of the parasite. Overall, this study shows how the avian malaria system can be used to study gene expression of the avian Plasmodium parasite under controlled experimental settings, thus allowing for future comparative analysis of gene responses of parasite with different life-history traits and host effects.
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20
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Guissou E, Waite JL, Jones M, Bell AS, Suh E, Yameogo KB, Djègbè N, Da DF, Hien DFDS, Yerbanga RS, Ouedraogo AG, Dabiré KR, Cohuet A, Thomas MB, Lefèvre T. A non-destructive sugar-feeding assay for parasite detection and estimating the extrinsic incubation period of Plasmodium falciparum in individual mosquito vectors. Sci Rep 2021; 11:9344. [PMID: 33927245 PMCID: PMC8085177 DOI: 10.1038/s41598-021-88659-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 04/14/2021] [Indexed: 01/19/2023] Open
Abstract
Despite its epidemiological importance, the time Plasmodium parasites take to achieve development in the vector mosquito (the extrinsic incubation period, EIP) remains poorly characterized. A novel non-destructive assay designed to estimate EIP in single mosquitoes, and more broadly to study Plasmodium-Anopheles vectors interactions, is presented. The assay uses small pieces of cotton wool soaked in sugar solution to collect malaria sporozoites from individual mosquitoes during sugar feeding to monitor infection status over time. This technique has been tested across four natural malaria mosquito species of Africa and Asia, infected with Plasmodium falciparum (six field isolates from gametocyte-infected patients in Burkina Faso and the NF54 strain) and across a range of temperatures relevant to malaria transmission in field conditions. Monitoring individual infectious mosquitoes was feasible. The estimated median EIP of P. falciparum at 27 °C was 11 to 14 days depending on mosquito species and parasite isolate. Long-term individual tracking revealed that sporozoites transfer onto cotton wool can occur at least until day 40 post-infection. Short individual EIP were associated with short mosquito lifespan. Correlations between mosquito/parasite traits often reveal trade-offs and constraints and have important implications for understanding the evolution of parasite transmission strategies.
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Affiliation(s)
- Edwige Guissou
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso. .,MIVEGEC, Montpellier University, IRD, CNRS, Montpellier, France. .,Laboratoire mixte international sur les vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso. .,Université Nazi Boni, Bobo Dioulasso, Burkina Faso.
| | - Jessica L Waite
- Center for Infectious Disease Dynamics, The Pennsylvania State University, University Park, PA, 16802, USA.,Green Mountain Antibodies, Inc. 1 Mill St. Suites 1-7, Burlington, VT, 05401, USA
| | - Matthew Jones
- Center for Infectious Disease Dynamics, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Andrew S Bell
- Center for Infectious Disease Dynamics, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Eunho Suh
- Center for Infectious Disease Dynamics, The Pennsylvania State University, University Park, PA, 16802, USA
| | | | - Nicaise Djègbè
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso
| | - Dari F Da
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso
| | - Domonbabele F D S Hien
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso.,Laboratoire mixte international sur les vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso
| | - Rakiswende S Yerbanga
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso.,Laboratoire mixte international sur les vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso
| | | | - Kounbobr Roch Dabiré
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso.,Laboratoire mixte international sur les vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso
| | - Anna Cohuet
- MIVEGEC, Montpellier University, IRD, CNRS, Montpellier, France.,Laboratoire mixte international sur les vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso
| | - Matthew B Thomas
- Center for Infectious Disease Dynamics, The Pennsylvania State University, University Park, PA, 16802, USA.,York Environmental Sustainability Institute and Department of Biology, University of York, York, UK
| | - Thierry Lefèvre
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso.,MIVEGEC, Montpellier University, IRD, CNRS, Montpellier, France.,Laboratoire mixte international sur les vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso.,Centre de Recherche en Écologie et Évolution de la Santé (CREES), Montpellier, France
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21
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Ukegbu CV, Christophides GK, Vlachou D. Identification of Three Novel Plasmodium Factors Involved in Ookinete to Oocyst Developmental Transition. Front Cell Infect Microbiol 2021; 11:634273. [PMID: 33791240 PMCID: PMC8005625 DOI: 10.3389/fcimb.2021.634273] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 02/10/2021] [Indexed: 12/11/2022] Open
Abstract
Plasmodium falciparum malaria remains a major cause of global morbidity and mortality, mainly in sub-Saharan Africa. The numbers of new malaria cases and deaths have been stable in the last years despite intense efforts for disease elimination, highlighting the need for new approaches to stop disease transmission. Further understanding of the parasite transmission biology could provide a framework for the development of such approaches. We phenotypically and functionally characterized three novel genes, PIMMS01, PIMMS57, and PIMMS22, using targeted disruption of their orthologs in the rodent parasite Plasmodium berghei. PIMMS01 and PIMMS57 are specifically and highly expressed in ookinetes, while PIMMS22 transcription starts already in gametocytes and peaks in sporozoites. All three genes show strong phenotypes associated with the ookinete to oocyst transition, as their disruption leads to very low numbers of oocysts and complete abolishment of transmission. PIMMS22 has a secondary essential function in the oocyst. Our results enrich the molecular understanding of the parasite-vector interactions and identify PIMMS01, PIMMS57, and PIMMS22 as new targets of transmission blocking interventions.
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Affiliation(s)
- Chiamaka V Ukegbu
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - George K Christophides
- Department of Life Sciences, Imperial College London, London, United Kingdom.,The Cyprus Institute, Nicosia, Cyprus
| | - Dina Vlachou
- Department of Life Sciences, Imperial College London, London, United Kingdom.,The Cyprus Institute, Nicosia, Cyprus
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22
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Challenger JD, Olivera Mesa D, Da DF, Yerbanga RS, Lefèvre T, Cohuet A, Churcher TS. Predicting the public health impact of a malaria transmission-blocking vaccine. Nat Commun 2021; 12:1494. [PMID: 33686061 PMCID: PMC7940395 DOI: 10.1038/s41467-021-21775-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 02/11/2021] [Indexed: 11/24/2022] Open
Abstract
Transmission-blocking vaccines that interrupt malaria transmission from humans to mosquitoes are being tested in early clinical trials. The activity of such a vaccine is commonly evaluated using membrane-feeding assays. Understanding the field efficacy of such a vaccine requires knowledge of how heavily infected wild, naturally blood-fed mosquitoes are, as this indicates how difficult it will be to block transmission. Here we use data on naturally infected mosquitoes collected in Burkina Faso to translate the laboratory-estimated activity into an estimated activity in the field. A transmission dynamics model is then utilised to predict a transmission-blocking vaccine's public health impact alongside existing interventions. The model suggests that school-aged children are an attractive population to target for vaccination. Benefits of vaccination are distributed across the population, averting the greatest number of cases in younger children. Utilising a transmission-blocking vaccine alongside existing interventions could have a substantial impact against malaria.
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Affiliation(s)
- Joseph D Challenger
- Medical Research Council Centre for Global Infections Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom.
| | - Daniela Olivera Mesa
- Medical Research Council Centre for Global Infections Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Dari F Da
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso
| | - R Serge Yerbanga
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso
- Institut des Sciences et Techniques, Bobo-Dioulasso, Burkina Faso
| | - Thierry Lefèvre
- MIVEGEC, University of Montpellier, CNRS, IRD, Montpellier, France
- Centre de Recherche en Écologie et Évolution de la Santé (CREES), Montpellier, France
| | - Anna Cohuet
- MIVEGEC, University of Montpellier, CNRS, IRD, Montpellier, France
| | - Thomas S Churcher
- Medical Research Council Centre for Global Infections Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
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23
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Reader J, van der Watt ME, Taylor D, Le Manach C, Mittal N, Ottilie S, Theron A, Moyo P, Erlank E, Nardini L, Venter N, Lauterbach S, Bezuidenhout B, Horatscheck A, van Heerden A, Spillman NJ, Cowell AN, Connacher J, Opperman D, Orchard LM, Llinás M, Istvan ES, Goldberg DE, Boyle GA, Calvo D, Mancama D, Coetzer TL, Winzeler EA, Duffy J, Koekemoer LL, Basarab G, Chibale K, Birkholtz LM. Multistage and transmission-blocking targeted antimalarials discovered from the open-source MMV Pandemic Response Box. Nat Commun 2021; 12:269. [PMID: 33431834 DOI: 10.1038/s41467-020-20629-8] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Accepted: 12/10/2020] [Indexed: 12/30/2022] Open
Abstract
Chemical matter is needed to target the divergent biology associated with the different life cycle stages of Plasmodium. Here, we report the parallel de novo screening of the Medicines for Malaria Venture (MMV) Pandemic Response Box against Plasmodium asexual and liver stage parasites, stage IV/V gametocytes, gametes, oocysts and as endectocides. Unique chemotypes were identified with both multistage activity or stage-specific activity, including structurally diverse gametocyte-targeted compounds with potent transmission-blocking activity, such as the JmjC inhibitor ML324 and the antitubercular clinical candidate SQ109. Mechanistic investigations prove that ML324 prevents histone demethylation, resulting in aberrant gene expression and death in gametocytes. Moreover, the selection of parasites resistant to SQ109 implicates the druggable V-type H+-ATPase for the reduced sensitivity. Our data therefore provides an expansive dataset of compounds that could be redirected for antimalarial development and also point towards proteins that can be targeted in multiple parasite life cycle stages. Here, Reader et al. screen the Medicines for Malaria Venture Pandemic Response Box in parallel against Plasmodiumasexual and liver stage parasites, stage IV/V gametocytes, gametes, oocysts and as endectocides. They identify two potent transmission-blocking drugs: a histone demethylase inhibitor ML324 and the antitubercular SQ109.
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24
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Ompad DC, Kessler A, Van Eijk AM, Padhan TK, Haque MA, Sullivan SA, Tozan Y, Rocklöv J, Mohanty S, Pradhan MM, Sahu PK, Carlton JM. The effectiveness of malaria camps as part of the Durgama Anchalare Malaria Nirakaran (DAMaN) program in Odisha, India: study protocol for a cluster-assigned quasi-experimental study. Glob Health Action 2021; 14:1886458. [PMID: 33866961 PMCID: PMC8183513 DOI: 10.1080/16549716.2021.1886458] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The Indian state of Odisha has a longstanding battle with forest malaria. Many remote and rural villages have poor access to health care, a problem that is exacerbated during the rainy season when malaria transmission is at its peak. Approximately 62% of the rural population consists of tribal groups who are among the communities most negatively impacted by malaria. To address the persistently high rates of malaria in these remote regions, the Odisha State Malaria Control Program introduced 'malaria camps' in 2017 where teams of health workers visit villages to educate the population, enhance vector control methods, and perform village-wide screening and treatment. Malaria rates declined statewide, particularly in forested areas, following the introduction of the malaria camps, but the impact of the intervention is yet to be externally evaluated. This study protocol describes a cluster-assigned quasi-experimental stepped-wedge study with a pretest-posttest control group design that evaluates if malaria camps reduce the prevalence of malaria, compared to control villages which receive the usual malaria control interventions (e.g. IRS, ITNs), as detected by PCR.
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Affiliation(s)
- Danielle C. Ompad
- School of Global Public Health, New York University, New York, NY, USA,CONTACT Danielle C. Ompad NYU School of Global Public Health, 715 Broadway, Room 1011, New York, NY10003USA
| | - Anne Kessler
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, NY, USA
| | - Anna Maria Van Eijk
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, NY, USA
| | - Timir K. Padhan
- Department of Molecular & Infectious Diseases, Community Welfare Society Hospital, Rourkela, Odisha, India
| | - Mohammed A. Haque
- Department of Molecular & Infectious Diseases, Community Welfare Society Hospital, Rourkela, Odisha, India
| | - Steven A. Sullivan
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, NY, USA
| | - Yesim Tozan
- School of Global Public Health, New York University, New York, NY, USA
| | - Joacim Rocklöv
- Department of Public Health and Clinical Medicine, Umea University, Umea, Sweden
| | - Sanjib Mohanty
- Department of Molecular & Infectious Diseases, Community Welfare Society Hospital, Rourkela, Odisha, India
| | - Madan M. Pradhan
- Department of Health & Family Welfare, State Vector Borne Disease Control Programme, Bhubaneswar, Odisha, India
| | - Praveen K. Sahu
- Department of Molecular & Infectious Diseases, Community Welfare Society Hospital, Rourkela, Odisha, India
| | - Jane M. Carlton
- School of Global Public Health, New York University, New York, NY, USA,Center for Genomics and Systems Biology, Department of Biology, New York University, New York, NY, USA
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25
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Teboh-Ewungkem MI, Woldegerima WA, Ngwa GA. Mathematical assessment of the impact of human-antibodies on sporogony during the within-mosquito dynamics of Plasmodium falciparum parasites. J Theor Biol 2021; 515:110562. [PMID: 33359209 DOI: 10.1016/j.jtbi.2020.110562] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2020] [Revised: 11/25/2020] [Accepted: 12/14/2020] [Indexed: 11/23/2022]
Abstract
We develop and analyze a deterministic ordinary differential equation mathematical model for the within-mosquito dynamics of the Plasmodium falciparum malaria parasite. Our model takes into account the action and effect of blood resident human-antibodies, ingested by the mosquito during a blood meal from humans, in inhibiting gamete fertilization. The model also captures subsequent developmental processes that lead to the different forms of the parasite within the mosquito. Continuous functions are used to model the switching transition from oocyst to sporozoites as well as human antibody density variations within the mosquito gut are proposed and used. In sum, our model integrates the developmental stages of the parasite within the mosquito such as gametogenesis, fertilization and sporogenesis culminating in the formation of sporozoites. Quantitative and qualitative analyses including a sensitivity analysis for influential parameters are performed. We quantify the average sporozoite load produced at the end of the within-mosquito malaria parasite's developmental stages. Our analysis shows that an increase in the efficiency of the ingested human antibodies in inhibiting fertilization within the mosquito's gut results in lowering the density of oocysts and hence sporozoites that are eventually produced by each mosquito vector. So, it is possible to control and limit oocysts development and hence sporozoites development within a mosquito by boosting the efficiency of antibodies as a pathway to the development of transmission-blocking vaccines which could potentially reduce oocysts prevalence among mosquitoes and hence reduce the transmission potential from mosquitoes to human.
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26
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Abstract
A pervasive characteristic of parasite infections is their tendency to be overdispersed. Understanding the mechanisms underlying this overdispersed distribution is of key importance as it may impact the transmission dynamics of the pathogen. Although multiple factors ranging from environmental stochasticity to inter-individual heterogeneity may explain parasite overdispersion, parasite infection is also overdispersed in an inbred host population maintained under laboratory conditions, suggesting that other mechanisms are at play. Here, we show that the aggregated distribution of malaria parasites within mosquito vectors is partially explained by a temporal heterogeneity in parasite infectivity triggered by the bites of mosquitoes. Parasite transmission tripled between the mosquito's first and last blood feed in a period of only 3 h. Surprisingly, the increase in transmission is not associated with an increase in parasite investment in production of the transmissible stage. Overall, we highlight that Plasmodium is capable of responding to the bites of mosquitoes to increase its own transmission at a much faster pace than initially thought and that this is partly responsible for overdispersed distribution of infection. We discuss the underlying mechanisms as well as the broader implications of this plastic response for the epidemiology of malaria.
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Affiliation(s)
- J Isaïa
- Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - A Rivero
- MIVEGEC (UMR CNRS 5290), Montpellier, France.,CREES (Centre de Recherche en Ecologie et Evolution de la Santé), Montpellier, France
| | - O Glaizot
- Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland.,Musée Cantonal de Zoologie, Lausanne, Switzerland
| | - P Christe
- Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - R Pigeault
- Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland
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27
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McCann RS, Cohee LM, Goupeyou-Youmsi J, Laufer MK. Maximizing Impact: Can Interventions to Prevent Clinical Malaria Reduce Parasite Transmission? Trends Parasitol 2020; 36:906-913. [PMID: 32917511 PMCID: PMC7581555 DOI: 10.1016/j.pt.2020.07.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 06/19/2020] [Accepted: 07/20/2020] [Indexed: 10/23/2022]
Abstract
Malaria interventions may reduce the burden of clinical malaria disease, the transmission of malaria parasites, or both. As malaria interventions are developed and evaluated, including those interventions primarily targeted at reducing disease, they may also impact parasite transmission. Achieving global malaria eradication will require optimizing the transmission-reducing potential of all available interventions. Herein, we discuss the relationship between malaria parasite transmission and disease, including mechanisms by which disease-targeting interventions might also impact parasite transmission. We then focus on three malaria interventions with strong evidence for reducing the burden of clinical malaria disease and examine their potential for also reducing malaria parasite transmission.
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Affiliation(s)
- Robert S McCann
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, USA.
| | - Lauren M Cohee
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Jessy Goupeyou-Youmsi
- MAC Communicable Diseases Action Centre, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Miriam K Laufer
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, USA
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28
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Miura K, Swihart BJ, Fay MP, Kumpitak C, Kiattibutr K, Sattabongkot J, Long CA. Evaluation and modeling of direct membrane-feeding assay with Plasmodium vivax to support development of transmission blocking vaccines. Sci Rep 2020; 10:12569. [PMID: 32724063 DOI: 10.1038/s41598-020-69513-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 07/09/2020] [Indexed: 02/06/2023] Open
Abstract
Standard and direct membrane-feeding assays (SMFA and DMFA) are fundamental assays to evaluate efficacy of transmission-blocking intervention (TBI) candidates against Plasmodium falciparum and vivax. To compare different candidates precisely, it is crucial to understand the error range of measured activity, usually expressed as percent inhibition in either oocyst intensity (% transmission reducing activity, %TRA), or in prevalence of infected mosquitoes (% transmission blocking activity, %TBA). To this end, mathematical models have been proposed for P. falciparum SMFA (PfSMFA), but such study for DMFA is limited. In this study, we analyzed P. vivax DMFA (PvDMFA) data from 22,236 mosquitoes tested from 96 independent assays. While the two assays are quite different, a zero-inflated negative binomial (ZINB) model could reasonably explain the PvDMFA results, as it has for PfSMFA. Our simulation studies based on the ZINB model revealed it is better to report %TRA values with a proper error range, rather than observed %TBA both in SMFA and DMFA. Furthermore, the simulations help in designing a better assay and aid in estimating an error range of a %TRA value when the uncertainty is not reported. This study strongly supports future TBI development by providing a rational method to compare different candidates.
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29
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Bompard A, Da DF, Yerbanga SR, Morlais I, Awono-Ambéné PH, Dabiré RK, Ouédraogo JB, Lefèvre T, Churcher TS, Cohuet A. High Plasmodium infection intensity in naturally infected malaria vectors in Africa. Int J Parasitol 2020; 50:985-96. [PMID: 32681932 DOI: 10.1016/j.ijpara.2020.05.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 05/14/2020] [Accepted: 05/17/2020] [Indexed: 01/18/2023]
Abstract
The population dynamics of human to mosquito malaria transmission in the field has important implications for the genetics, epidemiology and control of malaria. The number of oocysts in oocyst-positive mosquitoes developing from a single, naturally acquired infectious blood meal (herein referred to as a single-feed infection load) greatly influences the efficacy of transmission blocking interventions but still remains poorly documented. During a year-long analysis of malaria parasite transmission in Burkina Faso we caught and dissected wild malaria vectors to assess Plasmodium oocyst prevalence and load (the number of oocysts counted in mosquitoes with detectable oocysts) and the prevalence of salivary gland sporozoites. This was compared with malaria endemicity in the human population, assessed in cross-sectional surveys. Data were analysed using a novel transmission mathematical model to estimate the per bite transmission probability and the average single-feed infection load for each location. The observed oocyst load and the estimated single-feed infection load in naturally infected mosquitoes were substantially higher than previous estimates (means ranging from 3.2 to 24.5 according to seasons and locations) and indicate a strong positive association between the single-feed infection load and parasite prevalence in humans. This work suggests that highly infected mosquitoes are not rare in the field and might have a greater influence on the epidemiology and genetics of the parasite, and on the efficacy of novel transmission blocking interventions.
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30
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Graumans W, Jacobs E, Bousema T, Sinnis P. When Is a Plasmodium-Infected Mosquito an Infectious Mosquito? Trends Parasitol 2020; 36:705-716. [PMID: 32620501 DOI: 10.1016/j.pt.2020.05.011] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Revised: 05/19/2020] [Accepted: 05/20/2020] [Indexed: 12/19/2022]
Abstract
Plasmodium parasites experience significant bottlenecks as they transit through the mosquito and are transmitted to their mammalian host. Oocyst prevalence on mosquito midguts and sporozoite prevalence in salivary glands are nevertheless commonly used to confirm successful malaria transmission, assuming that these are reliable indicators of the mosquito's capacity to give rise to secondary infections. Here we discuss recent insights in sporogonic development and transmission bottlenecks for Plasmodium. We highlight critical gaps in our knowledge and frame their importance in understanding the human and mosquito reservoirs of infection. A better understanding of the events that lead to successful inoculation of infectious sporozoites by mosquitoes is critical to designing effective interventions to shrink the malaria map.
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Affiliation(s)
- Wouter Graumans
- Radboud University Medical Center, Radboud Institute for Health Sciences, Department of Medical Microbiology, Nijmegen, The Netherlands
| | - Ella Jacobs
- Department of Molecular Microbiology and Immunology, and Johns Hopkins Malaria Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Teun Bousema
- Radboud University Medical Center, Radboud Institute for Health Sciences, Department of Medical Microbiology, Nijmegen, The Netherlands; Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, UK.
| | - Photini Sinnis
- Department of Molecular Microbiology and Immunology, and Johns Hopkins Malaria Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
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31
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Pigeault R, Isaïa J, Yerbanga RS, Dabiré KR, Ouédraogo JB, Cohuet A, Lefèvre T, Christe P. Different distribution of malaria parasite in left and right extremities of vertebrate hosts translates into differences in parasite transmission. Sci Rep 2020; 10:10183. [PMID: 32576924 PMCID: PMC7311528 DOI: 10.1038/s41598-020-67180-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 06/04/2020] [Indexed: 11/16/2022] Open
Abstract
Malaria, a vector-borne disease caused by Plasmodium spp., remains a major global cause of mortality. Optimization of disease control strategies requires a thorough understanding of the processes underlying parasite transmission. While the number of transmissible stages (gametocytes) of Plasmodium in blood is frequently used as an indicator of host-to-mosquito transmission potential, this relationship is not always clear. Significant effort has been made in developing molecular tools that improve gametocyte density estimation and therefore prediction of mosquito infection rates. However a significant level of uncertainty around estimates remains. The weakness in the relationship between gametocyte burden, measured from a blood sample, and the mosquito infection rate could be explained by a non-homogeneous distribution of gametocytes in the bloodstream. The estimated gametocyte density would then only be a single snapshot that does not reflect the host infectivity. This aspect of Plasmodium infection, however, remains largely neglected. In both humans and birds, we found here that the gametocyte densities differed depending on which side of the body the sample was taken, suggesting that gametocytes are not homogeneously distributed within the vertebrate host. We observed a fluctuating asymmetry, in other words, the extremity of the body with the highest density of parasites is not always the same from one individual to another. An estimation of gametocyte density from only one blood sample, as is commonly measured, could, therefore, over- or underestimated the infectivity of gametocyte carriers. This might have important consequences on the epidemiology of the disease since we show that this variation influences host-to-mosquito transmission. Vectors fed on the least infected body part had a lower parasite burden than those fed on the most infected part. The heterogeneous distribution of gametocytes in bloodstream should be considered to improve diagnosis and test new malaria control strategies.
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Affiliation(s)
- Romain Pigeault
- Department of Ecology and Evolution, CH-1015, Lausanne, Switzerland.
| | - Julie Isaïa
- Department of Ecology and Evolution, CH-1015, Lausanne, Switzerland
| | | | - Kounbobr R Dabiré
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso
| | | | - Anna Cohuet
- Unité MIVEGEC, IRD 224-CNRS 5290-Université Montpellier, Montpellier, France
| | - Thierry Lefèvre
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso
- Unité MIVEGEC, IRD 224-CNRS 5290-Université Montpellier, Montpellier, France
| | - Philippe Christe
- Department of Ecology and Evolution, CH-1015, Lausanne, Switzerland
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32
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Hickey B, Teneza-Mora N, Lumsden J, Reyes S, Sedegah M, Garver L, Hollingdale MR, Banania JG, Ganeshan H, Dowler M, Reyes A, Tamminga C, Singer A, Simmons A, Belmonte M, Belmonte A, Huang J, Inoue S, Velasco R, Abot S, Vasquez CS, Guzman I, Wong M, Twomey P, Wojnarski M, Moon J, Alcorta Y, Maiolatesi S, Spring M, Davidson S, Chaudhury S, Villasante E, Richie TL, Epstein JE. IMRAS-A clinical trial of mosquito-bite immunization with live, radiation-attenuated P. falciparum sporozoites: Impact of immunization parameters on protective efficacy and generation of a repository of immunologic reagents. PLoS One 2020; 15:e0233840. [PMID: 32555601 PMCID: PMC7299375 DOI: 10.1371/journal.pone.0233840] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 05/12/2020] [Indexed: 12/31/2022] Open
Abstract
Background Immunization with radiation-attenuated sporozoites (RAS) by mosquito bite provides >90% sterile protection against Plasmodium falciparum (Pf) malaria in humans. RAS invade hepatocytes but do not replicate. CD8+ T cells recognizing parasite-derived peptides on the surface of infected hepatocytes are likely the primary protective mechanism. We conducted a randomized clinical trial of RAS immunization to assess safety, to achieve 50% vaccine efficacy (VE) against controlled human malaria infection (CHMI), and to generate reagents from protected and non-protected subjects for future identification of protective immune mechanisms and antigens. Methods Two cohorts (Cohort 1 and Cohort 2) of healthy, malaria-naïve, non-pregnant adults age 18–50 received five monthly immunizations with infected (true-immunized, n = 21) or non-infected (mock-immunized, n = 5) mosquito bites and underwent homologous CHMI at 3 weeks. Immunization parameters were selected for 50% protection based on prior clinical data. Leukapheresis was done to collect plasma and peripheral blood mononuclear cells. Results Adverse event rates were similar in true- and mock-immunized subjects. Two true- and two mock-immunized subjects developed large local reactions likely caused by mosquito salivary gland antigens. In Cohort 1, 11 subjects received 810–1235 infected bites; 6/11 (55%) were protected against CHMI vs. 0/3 mock-immunized and 0/6 infectivity controls (VE 55%). In Cohort 2, 10 subjects received 839–1131 infected bites with a higher first dose and a reduced fifth dose; 9/10 (90%) were protected vs. 0/2 mock-immunized and 0/6 controls (VE 90%). Three/3 (100%) protected subjects administered three booster immunizations were protected against repeat CHMI vs. 0/6 controls (VE 100%). Cohort 2 uniquely showed a significant rise in IFN-γ responses after the third and fifth immunizations and higher antibody responses to CSP. Conclusions PfRAS were generally safe and well tolerated. Cohort 2 had a higher first dose, reduced final dose, higher antibody responses to CSP and significant rise of IFN-γ responses after the third and fifth immunizations. Whether any of these factors contributed to increased protection in Cohort 2 requires further investigation. A cryobank of sera and cells from protected and non-protected individuals was generated for future immunological studies and antigen discovery. Trial registration ClinicalTrials.gov NCT01994525.
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Affiliation(s)
- Bradley Hickey
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
| | - Nimfa Teneza-Mora
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
| | - Joanne Lumsden
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Sharina Reyes
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Martha Sedegah
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
| | - Lindsey Garver
- Walter Reed Army Institute of Research, Silver Spring, MD, United States of America
| | - Michael R. Hollingdale
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
- * E-mail:
| | - Jo Glenna Banania
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Harini Ganeshan
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Megan Dowler
- Walter Reed Army Institute of Research, Silver Spring, MD, United States of America
| | - Anatalio Reyes
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Cindy Tamminga
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
| | - Alexandra Singer
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
| | - Alicia Simmons
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Maria Belmonte
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Arnel Belmonte
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Jun Huang
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Sandra Inoue
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Rachel Velasco
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Steve Abot
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Carlos S. Vasquez
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Ivelese Guzman
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Mimi Wong
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Patrick Twomey
- Walter Reed Army Institute of Research, Silver Spring, MD, United States of America
| | - Mariusz Wojnarski
- Walter Reed Army Institute of Research, Silver Spring, MD, United States of America
| | - James Moon
- Walter Reed Army Institute of Research, Silver Spring, MD, United States of America
| | - Yolanda Alcorta
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Santina Maiolatesi
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
| | - Michele Spring
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
- Walter Reed Army Institute of Research, Silver Spring, MD, United States of America
| | - Silas Davidson
- Walter Reed Army Institute of Research, Silver Spring, MD, United States of America
| | - Sidhartha Chaudhury
- Walter Reed Army Institute of Research, Silver Spring, MD, United States of America
- Biotechnology HPC Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Development Command, Frederick, MD, United States of America
| | - Eileen Villasante
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
| | - Thomas L. Richie
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
| | - Judith E. Epstein
- Malaria Department, Naval Medical Research Center, Silver Spring, MD, United States of America
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Abstract
A current challenge for disease modeling and public health is understanding pathogen dynamics across scales since their ecology and evolution ultimately operate on several coupled scales. This is particularly true for vector-borne diseases, where within-vector, within-host, and between vector–host populations all play crucial roles in diversity and distribution of the pathogen. Despite recent modeling efforts to determine the effect of within-host virus-immune response dynamics on between-host transmission, the role of within-vector viral dynamics on disease spread is overlooked. Here, we formulate an age-since-infection-structured epidemic model coupled to nonlinear ordinary differential equations describing within-host immune-virus dynamics and within-vector viral kinetics, with feedbacks across these scales. We first define the within-host viral-immune response and within-vector viral kinetics-dependent basic reproduction number [Formula: see text] Then we prove that whenever [Formula: see text] the disease-free equilibrium is locally asymptotically stable, and under certain biologically interpretable conditions, globally asymptotically stable. Otherwise, if [Formula: see text] it is unstable and the system has a unique positive endemic equilibrium. In the special case of constant vector to host inoculum size, we show the positive equilibrium is locally asymptotically stable and the disease is weakly uniformly persistent. Furthermore, numerical results suggest that within-vector-viral kinetics and dynamic inoculum size may play a substantial role in epidemics. Finally, we address how the model can be utilized to better predict the success of control strategies such as vaccination and drug treatment.
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Affiliation(s)
- HAYRIYE GULBUDAK
- Department of Mathematics, University of Louisiana at Lafayette, 104 E. University Circle, Lafayette, LA 70503, USA
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34
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Aleshnick M, Ganusov VV, Nasir G, Yenokyan G, Sinnis P. Experimental determination of the force of malaria infection reveals a non-linear relationship to mosquito sporozoite loads. PLoS Pathog 2020; 16:e1008181. [PMID: 32453765 PMCID: PMC7295235 DOI: 10.1371/journal.ppat.1008181] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 06/15/2020] [Accepted: 04/04/2020] [Indexed: 11/30/2022] Open
Abstract
Plasmodium sporozoites are the infective stage of the malaria parasite. Though this is a bottleneck for the parasite, the quantitative dynamics of transmission, from mosquito inoculation of sporozoites to patent blood-stage infection in the mammalian host, are poorly understood. Here we utilize a rodent model to determine the probability of malaria infection after infectious mosquito bite, and consider the impact of mosquito parasite load, blood-meal acquisition, probe-time, and probe location, on infection probability. We found that infection likelihood correlates with mosquito sporozoite load and, to a lesser degree, the duration of probing, and is not dependent upon the mosquito’s ability to find blood. The relationship between sporozoite load and infection probability is non-linear and can be described by a set of models that include a threshold, with mosquitoes harboring over 10,000 salivary gland sporozoites being significantly more likely to initiate a malaria infection. Overall, our data suggest that the small subset of highly infected mosquitoes may contribute disproportionally to malaria transmission in the field and that quantifying mosquito sporozoite loads could aid in predicting the force of infection in different transmission settings. Malaria is a leading cause of death in many parts of the world. Infection is initiated when infected Anopheles mosquitoes inject sporozoites as they look for blood. Though transmission is a bottleneck for the parasite and thus a good point for intervention, many aspects of transmission remain poorly understood. In this study, using a rodent model of malaria, we found that the majority of infective bites do not result in malaria infection. Furthermore, we found that the bites of mosquitoes with heavy parasite burdens are significantly more likely to result in blood stage infection. These data have important implications for designing interventions targeting transmission stages of the malaria parasite as they suggest that reducing parasite loads, even without completely eliminating them, could be effective against disease spread. We also found that mosquitoes that probe but do not succeed in finding blood are equally likely to initiate infection, an important finding for human vaccine trials. Overall this work contributes to our understanding of the epidemiology of malaria and should aid in the development of malaria elimination strategies.
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Affiliation(s)
- Maya Aleshnick
- Johns Hopkins Malaria Research Institute and Department of Molecular Microbiology & Immunology, Baltimore, Maryland, United States of America
| | - Vitaly V. Ganusov
- Departments of Microbiology and Mathematics, University of Tennessee, Knoxville Tennessee, United States of America
| | - Gibran Nasir
- Johns Hopkins Malaria Research Institute and Department of Molecular Microbiology & Immunology, Baltimore, Maryland, United States of America
| | - Gayane Yenokyan
- Johns Hopkins Biostatistics Center, Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Photini Sinnis
- Johns Hopkins Malaria Research Institute and Department of Molecular Microbiology & Immunology, Baltimore, Maryland, United States of America
- * E-mail:
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35
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Abstract
Immunity to malaria has been linked to the availability and function of helper CD4+ T cells, cytotoxic CD8+ T cells and γδ T cells that can respond to both the asymptomatic liver stage and the symptomatic blood stage of Plasmodium sp. infection. These T cell responses are also thought to be modulated by regulatory T cells. However, the precise mechanisms governing the development and function of Plasmodium-specific T cells and their capacity to form tissue-resident and long-lived memory populations are less well understood. The field has arrived at a point where the push for vaccines that exploit T cell-mediated immunity to malaria has made it imperative to define and reconcile the mechanisms that regulate the development and functions of Plasmodium-specific T cells. Here, we review our current understanding of the mechanisms by which T cell subsets orchestrate host resistance to Plasmodium infection on the basis of observational and mechanistic studies in humans, non-human primates and rodent models. We also examine the potential of new experimental strategies and human infection systems to inform a new generation of approaches to harness T cell responses against malaria.
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36
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Bailey RI, Cheng HH, Chase-Topping M, Mays JK, Anacleto O, Dunn JR, Doeschl-Wilson A. Pathogen transmission from vaccinated hosts can cause dose-dependent reduction in virulence. PLoS Biol 2020; 18:e3000619. [PMID: 32134914 PMCID: PMC7058279 DOI: 10.1371/journal.pbio.3000619] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 01/30/2020] [Indexed: 02/07/2023] Open
Abstract
Many livestock and human vaccines are leaky because they block symptoms but do not prevent infection or onward transmission. This leakiness is concerning because it increases vaccination coverage required to prevent disease spread and can promote evolution of increased pathogen virulence. Despite leakiness, vaccination may reduce pathogen load, affecting disease transmission dynamics. However, the impacts on post-transmission disease development and infectiousness in contact individuals are unknown. Here, we use transmission experiments involving Marek disease virus (MDV) in chickens to show that vaccination with a leaky vaccine substantially reduces viral load in both vaccinated individuals and unvaccinated contact individuals they infect. Consequently, contact birds are less likely to develop disease symptoms or die, show less severe symptoms, and shed less infectious virus themselves, when infected by vaccinated birds. These results highlight that even partial vaccination with a leaky vaccine can have unforeseen positive consequences in controlling the spread and symptoms of disease.
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Affiliation(s)
- Richard I. Bailey
- Division of Genetics and Genomics, The Roslin Institute, Easter Bush, Midlothian, United Kingdom
| | - Hans H. Cheng
- USDA, Agricultural Research Service, US National Poultry Research Center, Avian Disease and Oncology Laboratory, East Lansing, Michigan, United States of America
| | - Margo Chase-Topping
- Division of Genetics and Genomics, The Roslin Institute, Easter Bush, Midlothian, United Kingdom
- Usher Institute of Population Health Sciences & Informatics, University of Edinburgh, Edinburgh, United Kingdom
| | - Jody K. Mays
- USDA, Agricultural Research Service, US National Poultry Research Center, Avian Disease and Oncology Laboratory, East Lansing, Michigan, United States of America
| | - Osvaldo Anacleto
- Division of Genetics and Genomics, The Roslin Institute, Easter Bush, Midlothian, United Kingdom
| | - John R. Dunn
- USDA, Agricultural Research Service, US National Poultry Research Center, Avian Disease and Oncology Laboratory, East Lansing, Michigan, United States of America
| | - Andrea Doeschl-Wilson
- Division of Genetics and Genomics, The Roslin Institute, Easter Bush, Midlothian, United Kingdom
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37
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Flores-Garcia Y, Herrera SM, Jhun H, Pérez-Ramos DW, King CR, Locke E, Raghunandan R, Zavala F. Optimization of an in vivo model to study immunity to Plasmodium falciparum pre-erythrocytic stages. Malar J 2019; 18:426. [PMID: 31849326 PMCID: PMC6918627 DOI: 10.1186/s12936-019-3055-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Accepted: 12/07/2019] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND The circumsporozoite protein (CSP) of Plasmodium is a key surface antigen that induces antibodies and T-cells, conferring immune protection in animal models and humans. However, much of the work on CSP and immunity has been developed based on studies using rodent or non-human primate CSP antigens, which may not be entirely translatable to CSP expressed by human malaria parasites, especially considering the host specificity of the different species. METHODS Using a genetically engineered strain of Plasmodium berghei that expresses luciferase, GFP and the Plasmodium falciparum orthologue of CSP, the effect of laboratory preparation, mosquito treatment and mouse factors on sporozoite infectivity was assessed using an in vivo bioluminescence assay on mice. This assay was compared with a PCR-based protection assay using an already described monoclonal antibody that can provide sterile protection against sporozoite challenge. RESULTS Bioluminescence assay demonstrated similar detection levels of the quantity and kinetics of liver-stage infection, compared to PCR-based detection. This assay was used to evaluate treatment of sporozoite and delivery method on mouse infectivity, as well as the effects of age, sex and strain of mice. Finally, this assay was used to test the protective capacity of monoclonal antibody AB317; results strongly recapitulate the findings of previous work on this antibody. CONCLUSIONS The PbGFP-Luc line and in vivo bioluminescence imaging provide highly sensitive read-outs of liver-stage infection in mice, and this method can be useful to reliably evaluate potency of pre-erythrocytic interventions.
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Affiliation(s)
- Yevel Flores-Garcia
- Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
| | - Sonia M Herrera
- Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
| | - Hugo Jhun
- Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
| | - Daniel W Pérez-Ramos
- Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
| | - C Richter King
- PATH Malaria Vaccine Initiative, 455 Massachusetts Avenue, NW, Suite 1000, Washington, DC, 20001, USA
| | - Emily Locke
- PATH Malaria Vaccine Initiative, 455 Massachusetts Avenue, NW, Suite 1000, Washington, DC, 20001, USA
| | - Ramadevi Raghunandan
- PATH Malaria Vaccine Initiative, 455 Massachusetts Avenue, NW, Suite 1000, Washington, DC, 20001, USA
| | - Fidel Zavala
- Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA.
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38
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Lefebvre MN, Harty JT. You Shall Not Pass: Memory CD8 T Cells in Liver-Stage Malaria. Trends Parasitol 2019; 36:147-157. [PMID: 31843536 DOI: 10.1016/j.pt.2019.11.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 11/14/2019] [Accepted: 11/14/2019] [Indexed: 12/15/2022]
Abstract
Each year over 200 million malaria infections occur, with over 400 000 associated deaths. Vaccines formed with attenuated whole parasites can induce protective memory CD8 T cell responses against liver-stage malaria; however, widespread administration of such vaccines is logistically challenging. Recent scientific findings are delineating how protective memory CD8 T cell populations are primed and maintained and how such cells mediate immunity to liver-stage malaria. Memory CD8 T cell anatomic localization and expression of transcription factors, homing receptors, and signaling molecules appear to play integral roles in protective immunity to liver-stage malaria. Further investigation of how such factors contribute to optimal protective memory CD8 T cell generation and maintenance in humans will inform efforts for improved vaccines.
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Affiliation(s)
- Mitchell N Lefebvre
- Interdisciplinary Graduate Program in Immunology, University of Iowa, Iowa City, IA, USA
| | - John T Harty
- Interdisciplinary Graduate Program in Immunology, University of Iowa, Iowa City, IA, USA; Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, USA; Department of Pathology, University of Iowa, Iowa City, IA, USA.
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39
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Depoix D, Marques SR, Ferguson DJP, Chaouch S, Duguet T, Sinden RE, Grellier P, Kohl L. Vital role for
Plasmodium berghei
Kinesin8B in axoneme assembly during male gamete formation and mosquito transmission. Cell Microbiol 2019; 22:e13121. [DOI: 10.1111/cmi.13121] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2019] [Revised: 08/02/2019] [Accepted: 09/23/2019] [Indexed: 12/22/2022]
Affiliation(s)
- Delphine Depoix
- Unité Molécules de Communication et Adaptation des Microorganismes (MCAM), UMR 7245 CNRS Muséum National d'Histoire Naturelle Paris Cedex 05 France
| | | | - David JP Ferguson
- Nuffield Department of Clinical Laboratory Science University of Oxford Oxford UK
| | - Soraya Chaouch
- Unité Molécules de Communication et Adaptation des Microorganismes (MCAM), UMR 7245 CNRS Muséum National d'Histoire Naturelle Paris Cedex 05 France
| | - Thomas Duguet
- Unité Molécules de Communication et Adaptation des Microorganismes (MCAM), UMR 7245 CNRS Muséum National d'Histoire Naturelle Paris Cedex 05 France
- Institute of Parasitology, Macdonald Campus McGill University 21, 111 Lakeshore road Sainte‐Anne‐de‐Bellevue QC Canada
| | - Robert E Sinden
- Department of Life Sciences Imperial College of London London UK
| | - Philippe Grellier
- Unité Molécules de Communication et Adaptation des Microorganismes (MCAM), UMR 7245 CNRS Muséum National d'Histoire Naturelle Paris Cedex 05 France
| | - Linda Kohl
- Unité Molécules de Communication et Adaptation des Microorganismes (MCAM), UMR 7245 CNRS Muséum National d'Histoire Naturelle Paris Cedex 05 France
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40
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Suresh M, Jeevanandam J, Chan YS, Danquah MK, Kalaiarasi JMV. Opportunities for Metal Oxide Nanoparticles as a Potential Mosquitocide. BioNanoSci 2019. [DOI: 10.1007/s12668-019-00703-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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41
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Pathak AK, Shiau JC, Thomas MB, Murdock CC. Field Relevant Variation in Ambient Temperature Modifies Density-Dependent Establishment of Plasmodium falciparum Gametocytes in Mosquitoes. Front Microbiol 2019; 10:2651. [PMID: 31803169 PMCID: PMC6873802 DOI: 10.3389/fmicb.2019.02651] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 10/30/2019] [Indexed: 12/29/2022] Open
Abstract
The relationship between Plasmodium falciparum gametocyte density and infections in mosquitoes is central to understanding the rates of transmission with important implications for control. Here, we determined whether field relevant variation in environmental temperature could also modulate this relationship. Anopheles stephensi were challenged with three densities of P. falciparum gametocytes spanning a ~10-fold gradient, and housed under diurnal/daily temperature range ("DTR") of 9°C (+5°C and -4°C) around means of 20, 24, and 28°C. Vector competence was quantified as the proportion of mosquitoes infected with oocysts in the midguts (oocyst rates) or infectious with sporozoites in the salivary glands (sporozoite rates) at peak periods of infection for each temperature to account for the differences in development rates. In addition, oocyst intensities were also recorded from infected midguts and the overall study replicated across three separate parasite cultures and mosquito cohorts. While vector competence was similar at 20 DTR 9°C and 24 DTR 9°C, oocyst and sporozoite rates were also comparable, with evidence, surprisingly, for higher vector competence in mosquitoes challenged with intermediate gametocyte densities. For the same gametocyte densities however, severe reductions in the sporozoite rates was accompanied by a significant decline in overall vector competence at 28 DTR 9°C, with gametocyte density per se showing a positive and linear effect at this temperature. Unlike vector competence, oocyst intensities decreased with increasing temperatures with a predominantly positive and linear association with gametocyte density, especially at 28 DTR 9°C. Oocyst intensities across individual infected midguts suggested temperature-specific differences in mosquito susceptibility/resistance: at 20 DTR 9°C and 24 DTR 9°C, dispersion (aggregation) increased in a density-dependent manner but not at 28 DTR 9°C where the distributions were consistently random. Limitations notwithstanding, our results suggest that variation in temperature could modify seasonal dynamics of infectious reservoirs with implications for the design and deployment of transmission-blocking vaccines/drugs.
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Affiliation(s)
- Ashutosh K. Pathak
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
- Center for Ecology of Infectious Diseases, University of Georgia, Athens, GA, United States
- Center for Tropical Emerging Global Diseases, University of Georgia, Athens, GA, United States
| | - Justine C. Shiau
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
| | - Matthew B. Thomas
- The Department of Entomology, Center for Infectious Disease Dynamics, The Pennsylvania State University, University Park, PA, United States
| | - Courtney C. Murdock
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
- Center for Ecology of Infectious Diseases, University of Georgia, Athens, GA, United States
- Center for Tropical Emerging Global Diseases, University of Georgia, Athens, GA, United States
- Odum School of Ecology, University of Georgia, Athens, GA, United States
- Center for Vaccines and Immunology, University of Georgia, Athens, GA, United States
- Riverbasin Center, University of Georgia, Athens, GA, United States
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42
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Ghalehnoei H, Bagheri A, Fakhar M, Mishan MA. Circulatory microRNAs: promising non-invasive prognostic and diagnostic biomarkers for parasitic infections. Eur J Clin Microbiol Infect Dis 2019; 39:395-402. [PMID: 31617024 DOI: 10.1007/s10096-019-03715-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 09/16/2019] [Indexed: 12/12/2022]
Abstract
MicroRNAs (miRNAs) are a non-coding subclass of endogenous small regulatory RNAs, with about 18-25 nucleotides length which play a critical role in the regulation of gene expression at the post-transcriptional level in eukaryotes. Aberrant expression of miRNAs has the potential to become powerful non-invasive biomarkers in pathological diagnosis and prognosis of different disorders including infectious diseases. Parasite's life cycle may require the ability to respond to environmental and developmental signals through miRNA-mediated gene expressions. Over the last years, thousands of miRNAs have been identified in the helminthic and protozoan parasites and many pieces of evidence have demonstrated the functional role of miRNAs in the parasites' life cycle. Detection of these miRNAs in biofluids of infected hosts as prognostic and diagnostic biomarkers in infectious diseases is growing rapidly. In this review, we have highlighted altered expressions of host miRNAs, detected parasitic miRNAs in the infected hosts, and suggested some perspectives for future studies.
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Affiliation(s)
- Hossein Ghalehnoei
- Department of Medical Biotechnology, Toxoplasmosis Research Center, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Iran
| | - Abouzar Bagheri
- Department of Clinical Biochemistry-Biophysics and Genetics, Toxoplasmosis Research Center, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Iran.
| | - Mahdi Fakhar
- Department of Parasitology, Toxoplasmosis Research Center, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Iran.
| | - Mohammad Amir Mishan
- Ocular Tissue Engineering Research Center, Student Research Committee, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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43
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Julien JP, Wardemann H. Antibodies against Plasmodium falciparum malaria at the molecular level. Nat Rev Immunol 2019; 19:761-775. [DOI: 10.1038/s41577-019-0209-5] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/24/2019] [Indexed: 12/11/2022]
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44
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Abstract
Plasmodium sporozoites (SPZs) must traverse the mosquito salivary glands (SGs) to reach a new vertebrate host and continue the malaria disease cycle. Although SGs can harbor thousands of sporozoites, only 10 to 100 are deposited into a host during probing. To determine how the SGs might function as a bottleneck in SPZ transmission, we have characterized Anopheles stephensi SGs infected with the rodent malaria parasite Plasmodium berghei using immunofluorescence confocal microscopy. Our analyses corroborate findings from previous electron microscopy studies and provide new insights into the invasion process. We identified sites of SPZ accumulation within SGs across a range of infection intensities. Although SPZs were most often seen in the distal lateral SG lobes, they were also observed in the medial and proximal lateral lobes. Most parasites were associated with either the basement membrane or secretory cavities. SPZs accumulated at physical barriers, including fused salivary ducts and extensions of the chitinous salivary duct wall into the distal lumen. SPZs were observed only rarely within salivary ducts. SPZs appeared to contact each other in many different quantities, not just in the previously described large bundles. Within parasite bundles, all of the SPZs were oriented in the same direction. We found that moderate levels of infection did not necessarily correlate with major SG disruptions or abundant SG cell death. Altogether, our findings suggest that SG architecture largely acts as a barrier to SPZ transmission.IMPORTANCE Malaria continues to have a devastating impact on human health. With growing resistance to insecticides and antimalarial drugs, as well as climate change predictions indicating expansion of vector territories, the impact of malaria is likely to increase. Additional insights regarding pathogen migration through vector mosquitoes are needed to develop novel methods to prevent transmission to new hosts. Pathogens, including the microbes that cause malaria, must invade the salivary glands (SGs) for transmission. Since SG traversal is required for parasite transmission, SGs are ideal targets for transmission-blocking strategies. The work presented here highlights the role that mosquito SG architecture plays in limiting parasite traversal, revealing how the SG transmission bottleneck is imposed. Further, our data provide unprecedented detail about SG-sporozoite interactions and gland-to-gland variation not provided in previous studies.
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Affiliation(s)
- Michael B Wells
- Department of Cell Biology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
- Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Deborah J Andrew
- Department of Cell Biology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
- Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
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45
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Garira W, Mathebula D. A coupled multiscale model to guide malaria control and elimination. J Theor Biol 2019; 475:34-59. [PMID: 31128139 DOI: 10.1016/j.jtbi.2019.05.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2018] [Revised: 05/17/2019] [Accepted: 05/22/2019] [Indexed: 12/16/2022]
Abstract
In this paper, we share with the biomathematics community a new coupled multiscale model which has the potential to inform policy and guide malaria control and elimination. The formulation of this multiscale model is based on integrating four submodels which are: (i) a sub-model for the mosquito-to-human transmission of malaria parasite, (ii) a sub-model for the human-to-mosquito transmission of malaria parasite, (iii) a within-mosquito malaria parasite population dynamics sub-model and (iv) a within-human malaria parasite population dynamics sub-model. The integration of the four submodels is achieved by assuming that the transmission parameters of the sub-model for the mosquito-to-human transmission of malaria at the epidemiological scale are functions of the dependent variables of the within-mosquito sporozoite population dynamics while the transmission parameters of the sub-model for the human-to-mosquito transmission of malaria are functions of the dependent variables of the within-human gametocyte population dynamics. This establishes a unidirectionally coupled multiscale model where the within-human and within-mosquito submodels are unidirectionally coupled to the human-to-mosquito and mosquito-to-human submodels. A fast and slow time scale analysis is performed on this system. The result is a simple multiscale model which describes the mechanics of malaria transmission in terms of the major components of the complete malaria parasite life-cycle. This multiscale modelling approach may be found useful in guiding malaria control and elimination.
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Affiliation(s)
- Winston Garira
- Modelling Health and Environmental Linkages Research Group (MHELRG), Department of Mathematics and Applied Mathematics, University of Venda, Private Bag X5050, Thohoyandou 0950, South Africa.
| | - Dephney Mathebula
- Modelling Health and Environmental Linkages Research Group (MHELRG), Department of Mathematics and Applied Mathematics, University of Venda, Private Bag X5050, Thohoyandou 0950, South Africa
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46
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Miura K, Swihart BJ, Deng B, Zhou L, Pham TP, Diouf A, Fay MP, Long CA. Strong concordance between percent inhibition in oocyst and sporozoite intensities in a Plasmodium falciparum standard membrane-feeding assay. Parasit Vectors 2019; 12:206. [PMID: 31060594 PMCID: PMC6501457 DOI: 10.1186/s13071-019-3470-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 04/29/2019] [Indexed: 11/22/2022] Open
Abstract
Background Effective malaria transmission-blocking vaccines (TBVs) can support malaria eradication programmes, and the standard membrane-feeding assay (SMFA) has been used as a “gold standard” assay for TBV development. However, in SMFA, the inhibitory activity is commonly measured at oocyst stage of parasites, while it is the sporozoites which transmit malaria from a mosquito to a human. A handful of studies have shown that there is a positive correlation between oocyst and sporozoite intensities. However, no study has been completed to compare inhibition levels in oocyst and sporozoite intensities in the presence of transmission-blocking (TB) antibodies. Results Plasmodium falciparum NF54 gametocytes were fed to Anopheles stephensi mosquitoes with or without anti-Pfs25 or anti-Pfs48/45 TB antibodies in 15 independent assays. For each group, a portion of the mosquitoes was dissected for oocyst counts (day 8 after feed), and a portion of the remaining mosquitoes was dissected for sporozoite counts (day 16). This study covered a large range of oocyst and sporozoite intensities: 0.2 to 80.5 on average for oocysts, and 141 to 77,417 for sporozoites. The sporozoite data were well explained by a zero-inflated negative binomial model, regardless of the presence or absence of TB antibodies. Inhibition levels in both oocyst and sporozoite intensities were determined within the same groups in 9 independent assays. When the level of inhibition in sporozoite number (expressed as Log Mean Ratio, LMR; average number in a control group was divided by the one in a test group, then took a log of the ratio) was plotted against LMR in oocyst number, the best-fit slope of a linear regression was not different from 1 (the best estimate, 1.08; 95% confidence interval, 0.87 to 1.29). Furthermore, a Bland–Altman analysis showed a strong agreement between inhibitions in oocysts and in sporozoites. Conclusions The results indicate that percent inhibition in oocyst intensity of a test sample can be directly converted to % inhibition in sporozoite intensity in P. falciparum SMFA. Therefore, if sporozoite intensity determines transmission rate from mosquitoes to humans, the percent inhibition in oocyst intensity measured by SMFA can be used to estimate the TBV efficacy. Electronic supplementary material The online version of this article (10.1186/s13071-019-3470-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Kazutoyo Miura
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Rockville, MD, 20852, USA.
| | - Bruce J Swihart
- Biostatistics Research Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 5601 Fishers Lane, Rockville, MD, 20852, USA
| | - Bingbing Deng
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Rockville, MD, 20852, USA
| | - Luwen Zhou
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Rockville, MD, 20852, USA
| | - Thao P Pham
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Rockville, MD, 20852, USA
| | - Ababacar Diouf
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Rockville, MD, 20852, USA
| | - Michael P Fay
- Biostatistics Research Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 5601 Fishers Lane, Rockville, MD, 20852, USA
| | - Carole A Long
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Rockville, MD, 20852, USA
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Slater HC, Ross A, Felger I, Hofmann NE, Robinson L, Cook J, Gonçalves BP, Björkman A, Ouedraogo AL, Morris U, Msellem M, Koepfli C, Mueller I, Tadesse F, Gadisa E, Das S, Domingo G, Kapulu M, Midega J, Owusu-Agyei S, Nabet C, Piarroux R, Doumbo O, Doumbo SN, Koram K, Lucchi N, Udhayakumar V, Mosha J, Tiono A, Chandramohan D, Gosling R, Mwingira F, Sauerwein R, Paul R, Riley EM, White NJ, Nosten F, Imwong M, Bousema T, Drakeley C, Okell LC. The temporal dynamics and infectiousness of subpatent Plasmodium falciparum infections in relation to parasite density. Nat Commun 2019; 10:1433. [PMID: 30926893 PMCID: PMC6440965 DOI: 10.1038/s41467-019-09441-1] [Citation(s) in RCA: 92] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 03/07/2019] [Indexed: 02/08/2023] Open
Abstract
Malaria infections occurring below the limit of detection of standard diagnostics are common in all endemic settings. However, key questions remain surrounding their contribution to sustaining transmission and whether they need to be detected and targeted to achieve malaria elimination. In this study we analyse a range of malaria datasets to quantify the density, detectability, course of infection and infectiousness of subpatent infections. Asymptomatically infected individuals have lower parasite densities on average in low transmission settings compared to individuals in higher transmission settings. In cohort studies, subpatent infections are found to be predictive of future periods of patent infection and in membrane feeding studies, individuals infected with subpatent asexual parasite densities are found to be approximately a third as infectious to mosquitoes as individuals with patent (asexual parasite) infection. These results indicate that subpatent infections contribute to the infectious reservoir, may be long lasting, and require more sensitive diagnostics to detect them in lower transmission settings. The role of subpatent infections for malaria transmission and elimination is unclear. Here, Slater et al. analyse several malaria datasets to quantify the density, detectability, course of infection and infectiousness of subpatent infections.
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Affiliation(s)
- Hannah C Slater
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG, UK.
| | - Amanda Ross
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, 4002, Switzerland.,University of Basel, Basel, 4001, Switzerland
| | - Ingrid Felger
- University of Basel, Basel, 4001, Switzerland.,Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, 4002, Switzerland
| | - Natalie E Hofmann
- University of Basel, Basel, 4001, Switzerland.,Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, 4002, Switzerland
| | - Leanne Robinson
- Vector-borne Diseases Unit, Papua New Guinea Institute for Medical Research, Madang, Papua New Guinea.,Division of Population Health and Immunity, The Walter and Eliza Hall Institute of Medical Research, Parkville, 3052, VIC, Australia.,Medical Biology, University of Melbourne, Melbourne, 3010, VIC, Australia.,Disease Elimination, Burnet Institute, Melbourne, 3004, VIC, Australia
| | - Jackie Cook
- MRC Tropical Epidemiology Group, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK
| | - Bronner P Gonçalves
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK
| | - Anders Björkman
- Malaria Research, Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 171 77, Stockholm, Sweden
| | - Andre Lin Ouedraogo
- Département de Sciences Biomédicales, Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, 01 BP 2208, Burkina Faso.,Institute for Disease Modeling, Intellectual Ventures, Bellevue, 98005, Washington, USA
| | - Ulrika Morris
- Malaria Research, Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 171 77, Stockholm, Sweden
| | - Mwinyi Msellem
- Department of Training and Research, Mnazi Mmoja Hospital, Zanzibar, Tanzania
| | - Cristian Koepfli
- Population Health and Immunity Division, Walter and Eliza Hall Institute, Melbourne, 3052, Victoria, Australia.,Department of Biological Sciences, University of Notre Dame, Indiana, 46556, USA
| | - Ivo Mueller
- Division of Population Health and Immunity, The Walter and Eliza Hall Institute of Medical Research, Parkville, 3052, VIC, Australia.,Department of Parasites and Insect Vectors, Institut Pasteur, Paris, 75015, France.,Medical Biology, University of Melbourne, Melbourne, 3010, VIC, Australia
| | - Fitsum Tadesse
- Radboud Institute for Health Sciences, Radboud University Medical Centre, Nijmegen, 6525, The Netherlands.,Armauer Hansen Research Institute, Addis Ababa, Ethiopia.,Institute of Biotechnology, Addis Ababa University, Addis Ababa, Ethiopia
| | | | - Smita Das
- Diagnostics Program, PATH, Seattle, Washington, 98121, United States of America
| | - Gonzalo Domingo
- Diagnostics Program, PATH, Seattle, Washington, 98121, United States of America
| | - Melissa Kapulu
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7FZ, UK.,KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya, Centre for Genomics and Global Health, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - Janet Midega
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7FZ, UK.,KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya, Centre for Genomics and Global Health, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - Seth Owusu-Agyei
- Institute of Health, University of Health and Allied Sciences, Hohoe, PMB 31, Ghana
| | - Cécile Nabet
- Sorbonne Université, INSERM, Institut Pierre-Louis d'Epidémiologie et de Santé Publique, AP- HP, Groupe Hospitalier Pitié-Salpêtrière, Service de Parasitologie-Mycologie, Paris, 75646, France
| | - Renaud Piarroux
- Sorbonne Université, INSERM, Institut Pierre-Louis d'Epidémiologie et de Santé Publique, AP- HP, Groupe Hospitalier Pitié-Salpêtrière, Service de Parasitologie-Mycologie, Paris, 75646, France
| | - Ogobara Doumbo
- Malaria Research and Training Centre, Parasitic Diseases Epidemiology Department, UMI 3189, University of Sciences, Technique and Technology, Bamako, Mali
| | - Safiatou Niare Doumbo
- Malaria Research and Training Centre, Parasitic Diseases Epidemiology Department, UMI 3189, University of Sciences, Technique and Technology, Bamako, Mali
| | - Kwadwo Koram
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Naomi Lucchi
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Global Health, Centers for Disease Control and Prevention, Atlanta, 30030, GA, United States of America
| | - Venkatachalam Udhayakumar
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Global Health, Centers for Disease Control and Prevention, Atlanta, 30030, GA, United States of America
| | - Jacklin Mosha
- National Institute for Medical Research, Mwanza Medical Research Centre, Mwanza, Tanzania
| | - Alfred Tiono
- Department of Biomedical Sciences, Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, 01 BP 2208, Burkina Faso
| | - Daniel Chandramohan
- Department of Disease Control, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - Roly Gosling
- Malaria Elimination Initiative, Global Health Group, University of California, San Francisco, San Francisco, 94158, CA, United States
| | - Felista Mwingira
- Biological Sciences Department, Dar es Salaam University College of Education, P. O. Box 2329, Dar es Salaam, Tanzania
| | - Robert Sauerwein
- Radboud Institute for Health Sciences, Radboud University Medical Centre, Nijmegen, 6525, The Netherlands
| | - Richard Paul
- Institut Pasteur de Dakar, Laboratoire d'Entomologie Médicale, Dakar, Senegal
| | - Eleanor M Riley
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK.,The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian, EH25 9RG, UK
| | - Nicholas J White
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, OX3 7FZ, UK.,Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, 10400, Thailand
| | - Francois Nosten
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, OX3 7FZ, UK.,Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, 63110, Thailand
| | - Mallika Imwong
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, 10400, Thailand.,Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, 10400, Thailand
| | - Teun Bousema
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK.,Radboud Institute for Health Sciences, Radboud University Medical Centre, Nijmegen, 6525, The Netherlands
| | - Chris Drakeley
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK
| | - Lucy C Okell
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG, UK
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Maia MF, Kapulu M, Muthui M, Wagah MG, Ferguson HM, Dowell FE, Baldini F, Ranford-Cartwright L. Detection of Plasmodium falciparum infected Anopheles gambiae using near-infrared spectroscopy. Malar J 2019; 18:85. [PMID: 30890179 PMCID: PMC6423776 DOI: 10.1186/s12936-019-2719-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 03/11/2019] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Large-scale surveillance of mosquito populations is crucial to assess the intensity of vector-borne disease transmission and the impact of control interventions. However, there is a lack of accurate, cost-effective and high-throughput tools for mass-screening of vectors. METHODS A total of 750 Anopheles gambiae (Keele strain) mosquitoes were fed Plasmodium falciparum NF54 gametocytes through standard membrane feeding assay (SMFA) and afterwards maintained in insectary conditions to allow for oocyst (8 days) and sporozoite development (14 days). Thereupon, each mosquito was scanned using near infra-red spectroscopy (NIRS) and processed by quantitative polymerase chain reaction (qPCR) to determine the presence of infection and infection load. The spectra collected were randomly assigned to either a training dataset, used to develop calibrations for predicting oocyst- or sporozoite-infection through partial least square regressions (PLS); or to a test dataset, used for validating the calibration's prediction accuracy. RESULTS NIRS detected oocyst- and sporozoite-stage P. falciparum infections with 88% and 95% accuracy, respectively. This study demonstrates proof-of-concept that NIRS is capable of rapidly identifying laboratory strains of human malaria infection in African mosquito vectors. CONCLUSIONS Accurate, low-cost, reagent-free screening of mosquito populations enabled by NIRS could revolutionize surveillance and elimination strategies for the most important human malaria parasite in its primary African vector species. Further research is needed to evaluate how the method performs in the field following adjustments in the training datasets to include data from wild-caught infected and uninfected mosquitoes.
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Affiliation(s)
- Marta F Maia
- Swiss Tropical and Public Health Institute, Socinstrasse 57, 4020, Basel, Switzerland.
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland.
- KEMRI Wellcome Trust Research Programme, P.O. Box 230, Kilifi, 80108, Kenya.
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Old Road Campus Roosevelt Drive, Oxford, OX3 7FZ, UK.
| | - Melissa Kapulu
- KEMRI Wellcome Trust Research Programme, P.O. Box 230, Kilifi, 80108, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Old Road Campus Roosevelt Drive, Oxford, OX3 7FZ, UK
| | - Michelle Muthui
- KEMRI Wellcome Trust Research Programme, P.O. Box 230, Kilifi, 80108, Kenya
| | - Martin G Wagah
- KEMRI Wellcome Trust Research Programme, P.O. Box 230, Kilifi, 80108, Kenya
- Department of Public Health, School of Human and Health Sciences, Pwani University, Kilifi, Kenya
| | - Heather M Ferguson
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, UK
| | - Floyd E Dowell
- USDA, Agricultural Research Service, Center for Grain and Animal Health Research, 1515 College Avenue, Manhattan, KS, 66502, USA
| | - Francesco Baldini
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, UK
| | - Lisa Ranford-Cartwright
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, UK
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49
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Langwig KE, Gomes MGM, Clark MD, Kwitny M, Yamada S, Wargo AR, Lipsitch M. Limited available evidence supports theoretical predictions of reduced vaccine efficacy at higher exposure dose. Sci Rep 2019; 9:3203. [PMID: 30824732 PMCID: PMC6397254 DOI: 10.1038/s41598-019-39698-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 01/30/2019] [Indexed: 12/18/2022] Open
Abstract
Understanding the causes of vaccine failure is important for predicting disease dynamics in vaccinated populations and planning disease interventions. Pathogen exposure dose and heterogeneity in host susceptibility have both been implicated as important factors that may reduce overall vaccine efficacy and cause vaccine failure. Here, we explore the effect of pathogen dose and heterogeneity in host susceptibility in reducing efficacy of vaccines. Using simulation-based methods, we find that increases in pathogen exposure dose decrease vaccine efficacy, but this effect is modified by heterogeneity in host susceptibility. In populations where the mode of vaccine action is highly polarized, vaccine efficacy decreases more slowly with exposure dose than in populations with less variable protection. We compared these theoretical results to empirical estimates from a systematic literature review of vaccines tested over multiple exposure doses. We found that few studies (nine of 5,389) tested vaccine protection against infection over multiple pathogen challenge doses, with seven studies demonstrating a decrease in vaccine efficacy with increasing exposure dose. Our research demonstrates that pathogen dose has potential to be an important determinant of vaccine failure, although the limited empirical data highlight a need for additional studies to test theoretical predictions on the plausibility of reduced host susceptibility and high pathogen dose as mechanisms responsible for reduced vaccine efficacy in high transmission settings.
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Affiliation(s)
- Kate E Langwig
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA. .,Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, 02115, USA.
| | - M Gabriela M Gomes
- CIBIO-InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, Vairão, Portugal.,Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Mercedes D Clark
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Molly Kwitny
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Steffany Yamada
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Andrew R Wargo
- Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, VA, 23062, USA
| | - Marc Lipsitch
- Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, 02115, USA
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50
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Atcheson E, Bauza K, Reyes-Sandoval A. A probabilistic model of pre-erythrocytic malaria vaccine combination in mice. PLoS One 2019; 14:e0209028. [PMID: 30625136 DOI: 10.1371/journal.pone.0209028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Accepted: 11/27/2018] [Indexed: 11/19/2022] Open
Abstract
Malaria remains one the world’s most deadly infectious diseases, with almost half a million deaths and over 150 million clinical cases each year. An effective vaccine would contribute enormously to malaria control and will almost certainly be required for eventual eradication of the disease. However, the leading malaria vaccine candidate, RTS,S, shows only 30–50% efficacy under field conditions, making it less cost-effective than long-lasting insecticide treated bed nets. Other subunit malaria vaccine candidates, including TRAP-based vaccines, show no better protective efficacy. This has led to increased interest in combining subunit malaria vaccines as a means of enhancing protective efficacy. Mathematical models of the effect of combining such vaccines on protective efficacy can help inform optimal vaccine strategies and decision-making at all stages of the clinical process. So far, however, no such model has been developed for pre-clinical murine studies, the stage at which all candidate antigens and combinations begin evaluation. To address this gap, this paper develops a mathematical model of vaccine combination adapted to murine malaria studies. The model is based on simple probabilistic assumptions which put the model on a firmer theoretical footing than previous clinical models, which rather than deriving a relationship between immune responses and protective efficacy posit the relationship to be either exponential or Hill curves. Data from pre-clinical murine malaria studies are used to derive values for unknowns in the model which in turn allows simulations of vaccine combination efficacy and suggests optimal strategies to pursue. Finally, the ability of the model to shed light on fundamental biological variables of murine malaria such as the blood stage growth rate and sporozoite infectivity is explored.
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