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A probabilistic model of pre-erythrocytic malaria vaccine combination in mice. PLoS One 2019; 14:e0209028. [PMID: 30625136 PMCID: PMC6326473 DOI: 10.1371/journal.pone.0209028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [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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Brod F, Miura K, Taylor I, Li Y, Marini A, Salman AM, Spencer AJ, Long CA, Biswas S. Combination of RTS,S and Pfs25-IMX313 Induces a Functional Antibody Response Against Malaria Infection and Transmission in Mice. Front Immunol 2018; 9:2780. [PMID: 30564231 PMCID: PMC6288435 DOI: 10.3389/fimmu.2018.02780] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 11/12/2018] [Indexed: 12/18/2022] Open
Abstract
The last two decades saw a dramatic reduction in malaria incidence rates, but this decrease has been stalling recently, indicating control measures are starting to fail. An effective vaccine, particularly one with a marked effect on disease transmission, would undoubtedly be an invaluable tool for efforts to control and eliminate malaria. RTS,S/AS01, the most advanced malaria vaccine to date, targets the parasite before it invades the liver and has the potential to prevent malaria disease as well as transmission by preventing blood stage infection and therefore gametocytogenesis. Unfortunately efficacy in a phase III clinical trial was limited and it is widely believed that a malaria vaccine needed to contain multiple antigens from different life-cycle stages to have a realistic chance of success. A recent study in mice has shown that partially efficacious interventions targeting the pre-erythrocytic and the sexual lifecycle stage synergise in eliminating malaria from a population over multiple generations. Hence, the combination of RTS,S/AS01 with a transmission blocking vaccine (TBV) is highly appealing as a pragmatic and powerful way to increase vaccine efficacy. Here we demonstrate that combining Pfs25-IMX313, one of the TBV candidates currently in clinical development, with RTS,S/AS01 readily induces a functional immune response against both antigens in outbred CD1 mice. Formulation of Pfs25-IMX313 in AS01 significantly increased antibody titres when compared to formulation in Alhydrogel, resulting in improved transmission reducing activity in standard membrane feeding assays (SMFA). Upon co-formulation of Pfs25-IMX313 with RTS,S/AS01, the immunogenicity of both vaccines was maintained, and functional assessment of the induced antibody response by SMFA and inhibition of sporozoite invasion assay (ISI) showed no reduction in biological activity against parasites of both lifecycle stages. Should this findings be translatable to human vaccination this could greatly aid efforts to eliminate and eventually eradicate malaria.
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Affiliation(s)
- Florian Brod
- Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Kazutoyo Miura
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Disease, National Institutes of Health, Rockville, MD, United States
| | - Iona Taylor
- Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Yuanyuan Li
- Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Arianna Marini
- Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Ahmed M Salman
- Jenner Institute, University of Oxford, Oxford, United Kingdom
| | | | - Carole A Long
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Disease, National Institutes of Health, Rockville, MD, United States
| | - Sumi Biswas
- Jenner Institute, University of Oxford, Oxford, United Kingdom
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53
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Critical examination of approaches exploited to assess the effectiveness of transmission-blocking drugs for malaria. Future Med Chem 2018; 10:2619-2639. [PMID: 30499742 DOI: 10.4155/fmc-2018-0169] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
In the absence of clinically proven vaccines and emerging resistance to common antimalarials and insecticides, the onus of interrupting the life cycle of Plasmodium falciparum, is upon the transmission-blocking drugs. Current transmission-blocking drug primaquine finds its use restricted because of associated hemolytic toxicity issues in Glucose-6-Phosphate-Dehydrogenase deficient individuals. This article provides an extensive review of the assays used by the investigators to evaluate the transmission-blocking activity of drugs. Furthermore, limitations in existing transmission-blocking assessment approaches/studies are also covered in detail. This review is expected to help in the identification of lacunae in current understanding of transmission-blocking strategies, which are hindering our efforts to develop sustainable and effective transmission-blocking interventions.
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Gordon A, Gresh L, Ojeda S, Chowell G, Gonzalez K, Sanchez N, Saborio S, Mercado JC, Kuan G, Balmaseda A, Harris E. Differences in Transmission and Disease Severity Between 2 Successive Waves of Chikungunya. Clin Infect Dis 2018; 67:1760-1767. [PMID: 29697796 PMCID: PMC6233685 DOI: 10.1093/cid/ciy356] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 04/20/2018] [Indexed: 11/13/2022] Open
Abstract
Background Chikungunya, an arboviral disease, caused massive epidemics in Central and South America in 2014-2016. In a prospective pediatric cohort study, we examined the introduction of chikungunya in a naive population and investigated transmission and clinical characteristics. Methods Children presenting to the study health center with a chikungunya-like illness or undifferentiated fever were tested for chikungunya virus (CHIKV) infection by reverse transcriptase-polymerase chain reaction (RT-PCR) and serological assays. Inapparent CHIKV infections in the intervening year were determined by seroconversion in healthy blood samples collected annually. Results A total of 4353 children participated in the cohort study from March 2014 to February 2016 during the 2 epidemic waves of chikungunya. A total of 539 cases of chikungunya were documented, for an incidence rate of 80.2 cases per 1000 person-years (95% confidence interval [CI]: 73.7, 87.2); and a total of 893 CHIKV infections were documented, for an incidence rate of 137.1 infections per 1000 person-years (95% CI: 128.4, 146.4). The seroprevalence of anti-CHIKV antibodies increased linearly with age, with seroprevalence of >45% in 14-year-old children at the end of Epidemic 2. Symptom presentation varied between the epidemics, with Epidemic 2 exhibiting both a higher symptomatic-to-inapparent ratio (1:1.20 in Epidemic 1 vs. 1:0.65 in Epidemic 2) and more severe clinical presentation among cases. The mean reproduction number was also greater in Epidemic 2 than in Epidemic 1. Conclusions The intensity of transmission and severity of clinical presentation varied between the 2 epidemics, with higher transmission intensity associated with greater disease severity.
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Affiliation(s)
- Aubree Gordon
- Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor
| | - Lionel Gresh
- Sustainable Sciences Institute, Managua, Nicaragua
| | - Sergio Ojeda
- Sustainable Sciences Institute, Managua, Nicaragua
| | | | - Karla Gonzalez
- Sustainable Sciences Institute, Managua, Nicaragua
- Laboratorio Nacional de Virología, Centro Nacional de Diagnóstico y Referencia
| | - Nery Sanchez
- Sustainable Sciences Institute, Managua, Nicaragua
| | - Saira Saborio
- Sustainable Sciences Institute, Managua, Nicaragua
- Laboratorio Nacional de Virología, Centro Nacional de Diagnóstico y Referencia
| | - Juan Carlos Mercado
- Sustainable Sciences Institute, Managua, Nicaragua
- Laboratorio Nacional de Virología, Centro Nacional de Diagnóstico y Referencia
| | - Guillermina Kuan
- Sustainable Sciences Institute, Managua, Nicaragua
- Centro de Salud Sócrates Flores Vivas, Ministerio de Salud, Managua, Nicaragua
| | - Angel Balmaseda
- Sustainable Sciences Institute, Managua, Nicaragua
- Laboratorio Nacional de Virología, Centro Nacional de Diagnóstico y Referencia
| | - Eva Harris
- Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley
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Kristan M, Abeku TA, Lines J. Effect of environmental variables and kdr resistance genotype on survival probability and infection rates in Anopheles gambiae (s.s.). Parasit Vectors 2018; 11:560. [PMID: 30367663 PMCID: PMC6204000 DOI: 10.1186/s13071-018-3150-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 10/14/2018] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND Environmental factors, especially ambient temperature and relative humidity affect both mosquitoes and malaria parasites. The early part of sporogony is most sensitive and is affected by high temperatures and temperature fluctuation immediately following ingestion of an infectious blood meal. The aim of this study was to explore whether environmental variables such as temperature, together with the presence of the kdr insecticide resistance mutations, have an impact on survival probability and infection rates in wild Anopheles gambiae (s.s.) exposed and unexposed to a pyrethroid insecticide. METHODS Anopheles gambiae (s.s.) were collected as larvae, reared to adults, and fed on blood samples from 42 Plasmodium falciparum-infected local patients at a health facility in mid-western Uganda, then exposed either to nets treated with sub-lethal doses of deltamethrin or to untreated nets. After seven days, surviving mosquitoes were dissected and their midguts examined for oocysts. Prevalence (proportion infected) and intensity of infection (number of oocysts per infected mosquito) were recorded for each group. Mosquito mortality was recorded daily. Temperature and humidity were recorded every 30 minutes throughout the experiments. RESULTS Our findings indicate that apart from the effect of deltamethrin exposure, mean daily temperature during the incubation period, temperature range during the first 24 hours and on day 4 post-infectious feed had a highly significant effect on the risk of infection. Deltamethrin exposure still significantly impaired survival of kdr homozygous mosquitoes, while mean daily temperature and relative humidity during the incubation period independently affected mosquito mortality. Significant differences in survival of resistant genotypes were detected, with the lowest survival recorded in mosquitoes with heterozygote L1014S/L1014F genotype. CONCLUSIONS This study confirmed that the early part of sporogony is most affected by temperature fluctuations, while environmental factors affect mosquito survival. The impact of insecticide resistance on malaria infection and vector survival needs to be assessed separately for mosquitoes with different resistance mechanisms to fully understand its implications for currently available vector control tools and malaria transmission.
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Affiliation(s)
- Mojca Kristan
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK.
| | | | - Jo Lines
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK
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56
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Modeling the effects of insecticides resistance on malaria vector control in endemic regions of Kenya. Biosystems 2018; 174:49-59. [PMID: 30240719 DOI: 10.1016/j.biosystems.2018.09.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 08/14/2018] [Accepted: 09/11/2018] [Indexed: 11/22/2022]
Abstract
We present a model to investigate the effects of vector resistance to control strategies. The model captures the development of resistance as well as loss of resistance in mosquitoes and how these affect the progress in malaria control. Important thresholds were calculated from mathematical analysis and numerical results presented. Mathematical results reveal the existence of the disease free and endemic equilibria whose existence and stability depends on the control reproduction number, Rc. The disease persist when the Rc>1 and dies out when Rc<1. Control strategies use and adherence needs to be highly efficacious to thwart the effects of insecticides resistance. Moreover, it is not enough to just eradicate resistant mosquitoes.
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57
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Costa G, Gildenhard M, Eldering M, Lindquist RL, Hauser AE, Sauerwein R, Goosmann C, Brinkmann V, Carrillo-Bustamante P, Levashina EA. Non-competitive resource exploitation within mosquito shapes within-host malaria infectivity and virulence. Nat Commun 2018; 9:3474. [PMID: 30150763 PMCID: PMC6110728 DOI: 10.1038/s41467-018-05893-z] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2017] [Accepted: 08/01/2018] [Indexed: 11/22/2022] Open
Abstract
Malaria is a fatal human parasitic disease transmitted by a mosquito vector. Although the evolution of within-host malaria virulence has been the focus of many theoretical and empirical studies, the vector’s contribution to this process is not well understood. Here, we explore how within-vector resource exploitation would impact the evolution of within-host Plasmodium virulence. By combining within-vector dynamics and malaria epidemiology, we develop a mathematical model, which predicts that non-competitive parasitic resource exploitation within-vector restricts within-host parasite virulence. To validate our model, we experimentally manipulate mosquito lipid trafficking and gauge within-vector parasite development and within-host infectivity and virulence. We find that mosquito-derived lipids determine within-host parasite virulence by shaping development (quantity) and metabolic activity (quality) of transmissible sporozoites. Our findings uncover the potential impact of within-vector environment and vector control strategies on the evolution of malaria virulence. The evolution of within-host malaria virulence has been studied, but the vector’s contribution isn’t well understood. Here, Costa et al. show that non-competitive parasitic resource exploitation within-vector, in particular lipid trafficking, restricts within-host infectivity and virulence of the parasite.
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Affiliation(s)
- G Costa
- Vector Biology Unit, Max Planck Institute for Infection Biology (MPIIB), 10117, Berlin, Germany
| | - M Gildenhard
- Vector Biology Unit, Max Planck Institute for Infection Biology (MPIIB), 10117, Berlin, Germany
| | - M Eldering
- Vector Biology Unit, Max Planck Institute for Infection Biology (MPIIB), 10117, Berlin, Germany.,Department of Medical Microbiology, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - R L Lindquist
- Immunodynamics, German Rheumatism Research Centre (DRFZ), 10117, Berlin, Germany
| | - A E Hauser
- Immunodynamics, German Rheumatism Research Centre (DRFZ), 10117, Berlin, Germany.,Immune Dynamics and Intravital Microscopy, Charité-Universitätsmedizin, 10117, Berlin, Germany
| | - R Sauerwein
- Department of Medical Microbiology, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - C Goosmann
- Microscopy Core Facility, Max Planck Institute for Infection Biology (MPIIB), 10117, Berlin, Germany
| | - V Brinkmann
- Microscopy Core Facility, Max Planck Institute for Infection Biology (MPIIB), 10117, Berlin, Germany
| | - P Carrillo-Bustamante
- Vector Biology Unit, Max Planck Institute for Infection Biology (MPIIB), 10117, Berlin, Germany
| | - E A Levashina
- Vector Biology Unit, Max Planck Institute for Infection Biology (MPIIB), 10117, Berlin, Germany.
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58
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Langenberg MCC, Wammes LJ, McCall MBB, Bijker EM, van Gemert GJ, Graumans W, van de Vegte-Bolmer MG, Teelen K, Hermsen CC, Koelewijn R, van Hellemond JJ, van Genderen PJJ, Sauerwein RW. Controlled Human Malaria Infection with Graded Numbers of Plasmodium falciparum NF135.C10- or NF166.C8-Infected Mosquitoes. Am J Trop Med Hyg 2018; 99:709-712. [PMID: 30014816 PMCID: PMC6169176 DOI: 10.4269/ajtmh.18-0194] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Controlled human malaria infections (CHMIs) with Plasmodium falciparum (Pf) parasites are well established. Exposure to five Pf (NF54)-infected Anopheles mosquitoes results in 100% infection rates in malaria-naïve volunteers. Recently Pf clones NF135.C10 and NF166.C8 were generated for application in CHMIs. Here, we tested the clinical infection rates of these clones, using graded numbers of Pf-infected mosquitoes. In a double-blind randomized trial, we exposed 24 malaria-naïve volunteers to bites from one, two, or five mosquitoes infected with NF135.C10 or NF166.C8. The primary endpoint was parasitemia by quantitative polymerase chain reaction. For both strains, bites by five infected mosquitoes resulted in parasitemia in 4/4 volunteers; 3/4 volunteers developed parasitemia after exposure to one or two infected mosquitoes infected with either clone. The prepatent period was 7.25 ± 4.0 days (median ± range). There were no serious adverse events and comparable clinical symptoms between all groups. These data confirm the eligibility of NF135.C10 and NF166.C8 for use in CHMI studies.
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Affiliation(s)
| | - Linda J Wammes
- Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center, Rotterdam, The Netherlands.,Institute for Tropical Diseases, Harbour Hospital, Rotterdam, The Netherlands
| | - Matthew B B McCall
- Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Else M Bijker
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Geert-Jan van Gemert
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Wouter Graumans
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | | | - Karina Teelen
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Cornelis C Hermsen
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Rob Koelewijn
- Institute for Tropical Diseases, Harbour Hospital, Rotterdam, The Netherlands
| | - Jaap J van Hellemond
- Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center, Rotterdam, The Netherlands
| | | | - Robert W Sauerwein
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
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59
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Assessing Plasmodium falciparum transmission in mosquito-feeding assays using quantitative PCR. Malar J 2018; 17:249. [PMID: 29976199 PMCID: PMC6034226 DOI: 10.1186/s12936-018-2382-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Accepted: 06/09/2018] [Indexed: 12/29/2022] Open
Abstract
Background Evaluating the efficacy of transmission-blocking interventions relies on mosquito-feeding assays, with transmission typically assessed by microscopic identification of oocysts in mosquito midguts; however, microscopy has limited throughput, sensitivity and specificity. Where low prevalence and intensity mosquito infections occur, as observed during controlled human malaria infection studies or natural transmission, a reliable method for detection and quantification of low-level midgut infection is required. Here, a semi-automated, Taqman quantitative PCR (qPCR) assay sufficiently sensitive to detect a single-oocyst midgut infection is described. Results Extraction of genomic DNA from Anopheles stephensi midguts using a semi-automated extraction process was shown to have equivalent extraction efficiency to manual DNA extraction. An 18S Plasmodium falciparum qPCR assay was adapted for quantitative detection of P. falciparum midgut oocyst infection using synthetic DNA standards. The assay was validated for sensitivity and specificity, and the limit of detection was 0.7 genomes/µL (95% CI 0.4–1.6 genomes/µL). All microscopy-confirmed oocyst infected midgut samples were detected by qPCR, including all single-oocyst positive midguts. The genome number per oocyst was assessed 8–9 days after feeding assay using both qPCR and droplet digital PCR and was 3722 (IQR: 2951–5453) and 3490 (IQR: 2720–4182), respectively. Conclusions This semi-automated qPCR method enables accurate detection of low-level P. falciparum oocyst infections in mosquito midguts, and may improve the sensitivity, specificity and throughput of assays used to evaluate candidate transmission-blocking interventions. Electronic supplementary material The online version of this article (10.1186/s12936-018-2382-6) contains supplementary material, which is available to authorized users.
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60
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Esperança PM, Blagborough AM, Da DF, Dowell FE, Churcher TS. Detection of Plasmodium berghei infected Anopheles stephensi using near-infrared spectroscopy. Parasit Vectors 2018; 11:377. [PMID: 29954424 PMCID: PMC6027764 DOI: 10.1186/s13071-018-2960-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 06/18/2018] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The proportion of mosquitoes infected with malaria is an important entomological metric used to assess the intensity of transmission and the impact of vector control interventions. Currently, the prevalence of mosquitoes with salivary gland sporozoites is estimated by dissecting mosquitoes under a microscope or using molecular methods. These techniques are laborious, subjective, and require either expensive equipment or training. This study evaluates the potential of near-infrared spectroscopy (NIRS) to identify laboratory reared mosquitoes infected with rodent malaria. METHODS Anopheles stephensi mosquitoes were reared in the laboratory and fed on Plasmodium berghei infected blood. After 12 and 21 days post-feeding mosquitoes were killed, scanned and analysed using NIRS and immediately dissected by microscopy to determine the number of oocysts on the midgut wall or sporozoites in the salivary glands. A predictive classification model was used to determine parasite prevalence and intensity status from spectra. RESULTS The predictive model correctly classifies infectious and uninfectious mosquitoes with an overall accuracy of 72%. The false negative and false positive rates were 30 and 26%, respectively. While NIRS was able to differentiate between uninfectious and highly infectious mosquitoes, differentiating between mid-range infectious groups was less accurate. Multiple scans of the same specimen, with repositioning the mosquito between scans, is shown to improve accuracy. On a smaller dataset NIRS was unable to predict whether mosquitoes harboured oocysts. CONCLUSIONS To our knowledge, we provide the first evidence that NIRS can differentiate between infectious and uninfectious mosquitoes. Currently, distinguishing between different intensities of infection is challenging. The classification model provides a flexible framework and allows for different error rates to be optimised, enabling the sensitivity and specificity of the technique to be varied according to requirements.
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Affiliation(s)
- Pedro M. Esperança
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG UK
| | - Andrew M. Blagborough
- Department of Life Sciences, Imperial College London, South Kensington, London, SW7 2AZ UK
| | - Dari F. Da
- Institut de Recherche en Sciences de la Santé, Direction Régionale, 399 Avenue de la liberté, Bobo Dioulasso, 01 01 BP 545 Burkina Faso
| | - Floyd E. Dowell
- USDA, Agricultural Research Service, Center for Grain and Animal Health Research, 1515 College Avenue, Manhattan, KS 66502 USA
| | - Thomas S. Churcher
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG UK
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61
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Sherrard-Smith E, Sala KA, Betancourt M, Upton LM, Angrisano F, Morin MJ, Ghani AC, Churcher TS, Blagborough AM. Synergy in anti-malarial pre-erythrocytic and transmission-blocking antibodies is achieved by reducing parasite density. eLife 2018; 7:35213. [PMID: 29914622 PMCID: PMC6008048 DOI: 10.7554/elife.35213] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Accepted: 05/18/2018] [Indexed: 01/05/2023] Open
Abstract
Anti-malarial pre-erythrocytic vaccines (PEV) target transmission by inhibiting human infection but are currently partially protective. It has been posited, but never demonstrated, that co-administering transmission-blocking vaccines (TBV) would enhance malaria control. We hypothesized a mechanism that TBV could reduce parasite density in the mosquito salivary glands, thereby enhancing PEV efficacy. This was tested using a multigenerational population assay, passaging Plasmodium berghei to Anopheles stephensi mosquitoes. A combined efficacy of 90.8% (86.7-94.2%) was observed in the PEV +TBV antibody group, higher than the estimated efficacy of 83.3% (95% CrI 79.1-87.0%) if the two antibodies acted independently. Higher PEV efficacy at lower mosquito parasite loads was observed, comprising the first direct evidence that co-administering anti-sporozoite and anti-transmission interventions act synergistically, enhancing PEV efficacy across a range of TBV doses and transmission intensities. Combining partially effective vaccines of differing anti-parasitic classes is a pragmatic, powerful way to accelerate malaria elimination efforts.
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Affiliation(s)
- Ellie Sherrard-Smith
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Katarzyna A Sala
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | | | - Leanna M Upton
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Fiona Angrisano
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | | | - Azra C Ghani
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Thomas S Churcher
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
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62
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Bradley J, Stone W, Da DF, Morlais I, Dicko A, Cohuet A, Guelbeogo WM, Mahamar A, Nsango S, Soumaré HM, Diawara H, Lanke K, Graumans W, Siebelink-Stoter R, van de Vegte-Bolmer M, Chen I, Tiono A, Gonçalves BP, Gosling R, Sauerwein RW, Drakeley C, Churcher TS, Bousema T. Predicting the likelihood and intensity of mosquito infection from sex specific Plasmodium falciparum gametocyte density. eLife 2018; 7:34463. [PMID: 29848446 PMCID: PMC6013255 DOI: 10.7554/elife.34463] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 05/26/2018] [Indexed: 12/02/2022] Open
Abstract
Understanding the importance of gametocyte density on human-to-mosquito transmission is of immediate relevance to malaria control. Previous work (Churcher et al., 2013) indicated a complex relationship between gametocyte density and mosquito infection. Here we use data from 148 feeding experiments on naturally infected gametocyte carriers to show that the relationship is much simpler and depends on both female and male parasite density. The proportion of mosquitoes infected is primarily determined by the density of female gametocytes though transmission from low gametocyte densities may be impeded by a lack of male parasites. Improved precision of gametocyte quantification simplifies the shape of the relationship with infection increasing rapidly before plateauing at higher densities. The mean number of oocysts per mosquito rises quickly with gametocyte density but continues to increase across densities examined. The work highlights the importance of measuring both female and male gametocyte density when estimating the human reservoir of infection.
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Affiliation(s)
- John Bradley
- MRC Tropical Epidemiology Group, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Will Stone
- Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, Netherlands
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Dari F Da
- Institut de Recherche en Sciences de la Santé, Direction, Bobo Dioulasso, Burkina Faso
| | - Isabelle Morlais
- Institut de recherche pour le développement, MIVEGEC (UM-CNRS 5290-IRD 224), Montpellier, France
| | - 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
| | - Anna Cohuet
- Institut de recherche pour le développement, MIVEGEC (UM-CNRS 5290-IRD 224), Montpellier, France
| | - Wamdaogo M Guelbeogo
- Malaria Research and Training Centre, Faculty of Pharmacy and Faculty of Medicine and Dentistry, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Almahamoudou Mahamar
- Institut de recherche pour le développement, MIVEGEC (UM-CNRS 5290-IRD 224), Montpellier, France
| | - Sandrine Nsango
- Faculté de Médecine et des Sciences Pharmaceutiques, Université de Douala, Douala, Cameroon
| | - Harouna M Soumaré
- Institut de recherche pour le développement, MIVEGEC (UM-CNRS 5290-IRD 224), Montpellier, France
| | - Halimatou Diawara
- Institut de recherche pour le développement, MIVEGEC (UM-CNRS 5290-IRD 224), Montpellier, France
| | - Kjerstin Lanke
- Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - Wouter Graumans
- Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - Rianne Siebelink-Stoter
- Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | | | - Ingrid Chen
- Global Health Group, Malaria Elimination Initiative, University of California, San Francisco, San Francisco, United States
| | - Alfred Tiono
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Bronner Pamplona Gonçalves
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Roland Gosling
- Global Health Group, Malaria Elimination Initiative, University of California, San Francisco, San Francisco, United States
| | - Robert W Sauerwein
- Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - Chris Drakeley
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Thomas S Churcher
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, United Kingdom
| | - Teun Bousema
- Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, Netherlands
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
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Cahyaningrum P, Sulistyawati S. Malaria Risk Factors in Kaligesing, Purworejo District, Central Java Province, Indonesia: A Case-control Study. J Prev Med Public Health 2018; 51:148-153. [PMID: 29886710 PMCID: PMC5996187 DOI: 10.3961/jpmph.18.036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 05/16/2018] [Indexed: 11/16/2022] Open
Abstract
Objectives Malaria remains a public health concern worldwide, including Indonesia. Purworejo is a district in which endemic of malaria, they have re-setup to entering malaria elimination in 2021. Accordingly, actions must be taken to accelerate and guaranty that the goal will reach based on an understanding of the risk factors for malaria. Thus, we analysed malaria risk factors based on human and housing conditions in Kaligesing, Purworejo, Indonesia. Methods A case-control study was carried out in Kaligesing subdistrict, Purworejo, Indonesia in July to August 2017. A structured questionnaire and checklist were used to collect data from 96 participants, who consisted of 48 controls and 48 cases. Univariate, bivariate, and multivariate analyses were performed. Results Bivariate analysis found that education level, the presence of a cattle cage within 100 m of the house, not sleeping under a bednet the previous night, and not closing the doors and windows from 6 p.m. to 5 a.m. were significantly (p≤0.25) associated with malaria. Of these factors, only not sleeping under a bednet the previous night and not closing the doors and windows from 6 p.m. to 5 a.m. were significantly associated with malaria. Conclusions The findings of this study demonstrate that potential risk factor for Malaria should be paid of attention all the time, particularly for an area which is targeting Malaria elimination.
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64
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Walk J, van Gemert GJ, Graumans W, Sauerwein RW, Bijker EM. Mosquito Infectivity and Parasitemia after Controlled Human Malaria Infection. Am J Trop Med Hyg 2018; 98:1705-1708. [PMID: 29714158 DOI: 10.4269/ajtmh.17-0952] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Controlled Human Malaria Infection (CHMI) has become an increasingly important tool for the evaluation of drugs and vaccines. Controlled Human Malaria Infection has been demonstrated to be a reproducible model; however, there is some variability in time to onset of parasitemia between volunteers and studies. At our center, mosquitoes infected with Plasmodium falciparum by membrane feeding have variable and high salivary gland sporozoite load (mean 78,415; range 26,500-160,500). To determine whether this load influences parasitemia after CHMI, we analyzed data from 13 studies. We found no correlation between the sporozoite load of a mosquito batch and time to parasitemia or parasite density of first-wave parasitemia. These findings support the use of infected mosquito bite as a reproducible means of inducing P. falciparum infection and suggest that within this range, salivary gland sporozoite load does not influence the stringency of a CHMI.
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Affiliation(s)
- Jona Walk
- Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Geert-Jan van Gemert
- Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Wouter Graumans
- Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Robert W Sauerwein
- Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Else M Bijker
- Department of Pediatrics, Radboud Institute for Molecular Life Sciences, Amalia Children's Hospital, Radboud University Medical Center, Nijmegen, The Netherlands
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65
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Khamis D, El Mouden C, Kura K, Bonsall MB. Optimal control of malaria: combining vector interventions and drug therapies. Malar J 2018; 17:174. [PMID: 29690874 PMCID: PMC5937842 DOI: 10.1186/s12936-018-2321-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 04/18/2018] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND The sterile insect technique and transgenic equivalents are considered promising tools for controlling vector-borne disease in an age of increasing insecticide and drug-resistance. Combining vector interventions with artemisinin-based therapies may achieve the twin goals of suppressing malaria endemicity while managing artemisinin resistance. While the cost-effectiveness of these controls has been investigated independently, their combined usage has not been dynamically optimized in response to ecological and epidemiological processes. RESULTS An optimal control framework based on coupled models of mosquito population dynamics and malaria epidemiology is used to investigate the cost-effectiveness of combining vector control with drug therapies in homogeneous environments with and without vector migration. The costs of endemic malaria are weighed against the costs of administering artemisinin therapies and releasing modified mosquitoes using various cost structures. Larval density dependence is shown to reduce the cost-effectiveness of conventional sterile insect releases compared with transgenic mosquitoes with a late-acting lethal gene. Using drug treatments can reduce the critical vector control release ratio necessary to cause disease fadeout. CONCLUSIONS Combining vector control and drug therapies is the most effective and efficient use of resources, and using optimized implementation strategies can substantially reduce costs.
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Affiliation(s)
- Doran Khamis
- Mathematical Ecology Research Group, Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS UK
| | - Claire El Mouden
- Mathematical Ecology Research Group, Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS UK
| | - Klodeta Kura
- Mathematical Ecology Research Group, Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS UK
| | - Michael B. Bonsall
- Mathematical Ecology Research Group, Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS UK
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66
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Moriyasu T, Nakamura R, Deloer S, Senba M, Kubo M, Inoue M, Culleton R, Hamano S. Schistosoma mansoni infection suppresses the growth of Plasmodium yoelii parasites in the liver and reduces gametocyte infectivity to mosquitoes. PLoS Negl Trop Dis 2018; 12:e0006197. [PMID: 29373600 PMCID: PMC5802944 DOI: 10.1371/journal.pntd.0006197] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 02/07/2018] [Accepted: 12/28/2017] [Indexed: 11/19/2022] Open
Abstract
Malaria and schistosomiasis are major parasitic diseases causing morbidity and mortality in the tropics. Epidemiological surveys have revealed coinfection rates of up to 30% among children in Sub-Saharan Africa. To investigate the impact of coinfection of these two parasites on disease epidemiology and pathology, we carried out coinfection studies using Plasmodium yoelii and Schistosoma mansoni in mice. Malaria parasite growth in the liver following sporozoite inoculation is significantly inhibited in mice infected with S. mansoni, so that when low numbers of sporozoites are inoculated, there is a large reduction in the percentage of mice that go on to develop blood stage malaria. Furthermore, gametocyte infectivity is much reduced in mice with S. mansoni infections. These results have profound implications for understanding the interactions between Plasmodium and Schistosoma species, and have implications for the control of malaria in schistosome endemic areas. Malaria and schistosomiasis are parasitic infectious diseases that cause severe morbidity and mortality in the tropics. Chronic schistosomiasis causes malnutrition and impaired intellectual development to children while malaria can cause fatal acute infections. Since coinfection of these two parasites is common in the tropics, many studies of both epidemiology and coinfection in animal models have been performed in order to reveal interactions between them. Previous animal studies on the interactions between Plasmodium and Schistosoma parasites have focused on the blood stage pathology of the malaria infection, and have consistently shown that parasitaemia can be enhanced in the presence of the helminth. In contrast, we focused on liver immunopathology in mice during coinfection between with Schistosoma and Plasmodium. We show that S. mansoni infection inhibits Plasmodium parasite growth in the liver resulting in a large reduction in the percentage of mice that go on to develop blood stage malaria following inoculation of low numbers of sporozoites. We also demonstrate that gametocyte infectivity is much reduced in mice with S. mansoni infections. Our results imply that S. mansoni infection can reduce malaria transmission both from mosquitoes to mice, and from mice to mosquitoes.
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Affiliation(s)
- Taeko Moriyasu
- Leading Program, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
- Department of Parasitology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan
- The Joint Usage/Research Center on Tropical Disease, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan
| | - Risa Nakamura
- Leading Program, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
- Department of Parasitology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan
- The Joint Usage/Research Center on Tropical Disease, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan
| | - Sharmina Deloer
- Leading Program, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
- Department of Parasitology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan
- The Joint Usage/Research Center on Tropical Disease, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan
| | - Masachika Senba
- Pathology Unit, Department of Pathology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan
| | - Masato Kubo
- Laboratory for Cytokine Regulation, Research Center for Integrative Medical Science (IMS), RIKEN Yokohama Institute, Yokohama, Japan
- Division of Molecular Pathology, Research Institute for Biomedical Science, Tokyo University of Science, Noda, Japan
| | - Megumi Inoue
- Malaria Unit, Department of Pathology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan
| | - Richard Culleton
- Leading Program, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
- Malaria Unit, Department of Pathology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan
- * E-mail: (RC); (SH)
| | - Shinjiro Hamano
- Leading Program, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
- Department of Parasitology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan
- The Joint Usage/Research Center on Tropical Disease, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan
- * E-mail: (RC); (SH)
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Arthropod-borne pathogens of dogs and cats: From pathways and times of transmission to disease control. Vet Parasitol 2017; 251:68-77. [PMID: 29426479 DOI: 10.1016/j.vetpar.2017.12.021] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2017] [Revised: 12/25/2017] [Accepted: 12/26/2017] [Indexed: 11/21/2022]
Abstract
Vector-borne pathogens have developed a close relationship with blood feeding arthropod ectoparasites (e.g., mosquitoes, ticks, phlebotomine sand flies, black flies, fleas, kissing bugs, lice) and exploited a huge variety of vector transmission routes. Therefore, the life cycles of these pathogens result in a long evolved balance with the respective arthropod biology, ecology and blood feeding habits, instrumentally to the infection of several animal species, including humans. Amongst the many parasite transmission modes, such as ingestion of the arthropod, with its faeces or secretions, blood feeding represents the main focus for this article, as it is a central event to the life of almost all arthropod vectors. The time frame in which pathogens are transmitted to any animal host is governed by a large number of biological variables related to the vector, the pathogen, the host and environmental factors. Scientific data available on transmission times for each pathogen are discussed relative to their impact for the success of vector-borne disease control strategies. Blocking pathogen transmission, and thus preventing the infection of dogs and cats, may be achievable by the use of chemical compounds if they are characterised by a fast onset of killing activity or repellence against arthropods. The fast speed of kill exerted by systemic isoxazoline, as well as the repellent effect of pyrethroids have renewed the interest of the scientific community and pharmaceutical companies towards reducing the burden of vector-borne diseases under field conditions. However, endosymbionts and vaccines targeting arthropods or pathogen antigens should be further investigated as alternative strategies towards the goal of achieving an effective integrated control of vector-borne diseases.
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68
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Lefevre T, Ohm J, Dabiré KR, Cohuet A, Choisy M, Thomas MB, Cator L. Transmission traits of malaria parasites within the mosquito: Genetic variation, phenotypic plasticity, and consequences for control. Evol Appl 2017; 11:456-469. [PMID: 29636799 PMCID: PMC5891056 DOI: 10.1111/eva.12571] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 10/23/2017] [Indexed: 12/16/2022] Open
Abstract
Evaluating the risk of emergence and transmission of vector‐borne diseases requires knowledge of the genetic and environmental contributions to pathogen transmission traits. Compared to the significant effort devoted to understanding the biology of malaria transmission from vertebrate hosts to mosquito vectors, the strategies that malaria parasites have evolved to maximize transmission from vectors to vertebrate hosts have been largely overlooked. While determinants of infection success within the mosquito host have recently received attention, the causes of variability for other key transmission traits of malaria, namely the duration of parasite development and its virulence within the vector, as well as its ability to alter mosquito behavior, remain largely unknown. This important gap in our knowledge needs to be bridged in order to obtain an integrative view of the ecology and evolution of malaria transmission strategies. Associations between transmission traits also need to be characterized, as they trade‐offs and constraints could have important implications for understanding the evolution of parasite transmission. Finally, theoretical studies are required to evaluate how genetic and environmental influences on parasite transmission traits can shape malaria dynamics and evolution in response to disease control.
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Affiliation(s)
- Thierry Lefevre
- MIVEGEC, IRD, CNRS University of Montpellier Montpellier France.,Institut de Recherche en Sciences de la Santé (IRSS) Bobo Dioulasso Burkina Faso.,Laboratoire Mixte International sur les Vecteurs (LAMIVECT) Bobo Dioulasso Burkina Faso
| | - Johanna Ohm
- Department of Entomology and Center for Infectious Disease Dynamics Penn State University University Park PA USA
| | - Kounbobr R Dabiré
- Institut de Recherche en Sciences de la Santé (IRSS) Bobo Dioulasso Burkina Faso.,Laboratoire Mixte International sur les Vecteurs (LAMIVECT) Bobo Dioulasso Burkina Faso
| | - Anna Cohuet
- MIVEGEC, IRD, CNRS University of Montpellier Montpellier France
| | - Marc Choisy
- MIVEGEC, IRD, CNRS University of Montpellier Montpellier France.,Oxford University Clinical Research Unit Hanoi Vietnam
| | - Matthew B Thomas
- Department of Entomology and Center for Infectious Disease Dynamics Penn State University University Park PA USA
| | - Lauren Cator
- Grand Challenges in Ecosystems and Environment Imperial College London Ascot UK
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69
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Dechering KJ, Duerr HP, Koolen KMJ, Gemert GJV, Bousema T, Burrows J, Leroy D, Sauerwein RW. Modelling mosquito infection at natural parasite densities identifies drugs targeting EF2, PI4K or ATP4 as key candidates for interrupting malaria transmission. Sci Rep 2017; 7:17680. [PMID: 29247222 PMCID: PMC5732164 DOI: 10.1038/s41598-017-16671-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 11/16/2017] [Indexed: 11/25/2022] Open
Abstract
Eradication of malaria requires a novel type of drug that blocks transmission from the human to the mosquito host, but selection of such a drug is hampered by a lack of translational models. Experimental mosquito infections yield infection intensities that are substantially higher than observed in natural infections and, as a consequence, underestimate the drug effect on the proportion of mosquitoes that become infected. Here we introduce a novel experimental and computational method to adequately describe drug efficacy at natural parasite densities. Parameters of a beta-binomial infection model were established and validated using a large number of experimental mosquito infections at different parasite densities. Analyses of 15 experimental and marketed drugs revealed a class-specific ability to block parasite transmission. Our results highlight the parasite's elongation factor EF2, PI4 kinase and the ATP4 sodium channel as key targets for interruption of transmission, and compounds DDD107498 and KAE609 as most advanced drug candidates.
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Affiliation(s)
- Koen J Dechering
- TropIQ Health Sciences, Transistorweg 5-C02, 6534AT, Nijmegen, The Netherlands.
| | | | - Karin M J Koolen
- TropIQ Health Sciences, Transistorweg 5-C02, 6534AT, Nijmegen, The Netherlands
| | - Geert-Jan van Gemert
- Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Teun Bousema
- Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Jeremy Burrows
- Medicines for Malaria Venture, Route de Pré-Bois 20, 1215, Geneva, 15, Switzerland
| | - Didier Leroy
- Medicines for Malaria Venture, Route de Pré-Bois 20, 1215, Geneva, 15, Switzerland
| | - Robert W Sauerwein
- TropIQ Health Sciences, Transistorweg 5-C02, 6534AT, Nijmegen, The Netherlands
- Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
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70
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Abstract
Vertically transmitted parasites (VTPs) such as Wolbachia are expected not only to minimize the damage they inflict on their hosts, but also to protect their hosts against the damaging effects of coinfecting parasites. By modifying the fitness costs of the infection, VTPs can therefore play an important role in the evolution and epidemiology of infectious diseases.Using a natural system, we explore the effects of a Wolbachia-Plasmodium co-infection on mosquito fecundity. While Plasmodium is known to frequently express its virulence by partially castrating its mosquito vectors, the effects of Wolbachia infections on mosquito fecundity are, in contrast, highly variable. Here, we show that Plasmodium drastically decreases the fecundity of mosquitoes by ca. 20%, and we provide the first evidence that this decrease is independent of the parasite's burden. Wolbachia, on the other hand, increases fecundity by roughly 10%, but does not alter the tolerance (fecundity-burden relationship) of mosquitoes to Plasmodium infection.Although Wolbachia-infected mosquitoes fare overall better than uninfected ones, Wolbachia does not confer a sufficiently high reproductive boost to mosquitoes to compensate for the reproductive losses inflicted by Plasmodium. We discuss the potential mechanisms and implications underlying the conflicting effects of these two parasites on mosquito reproduction.
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71
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Bompard A, Da DF, Yerbanga RS, Biswas S, Kapulu M, Bousema T, Lefèvre T, Cohuet A, Churcher TS. Evaluation of two lead malaria transmission blocking vaccine candidate antibodies in natural parasite-vector combinations. Sci Rep 2017; 7:6766. [PMID: 28754921 PMCID: PMC5533793 DOI: 10.1038/s41598-017-06130-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 06/08/2017] [Indexed: 12/25/2022] Open
Abstract
Transmission blocking vaccines (TBV) which aim to control malaria by inhibiting human-to-mosquito transmission show considerable promise though their utility against naturally circulating parasites remains unknown. The efficacy of two lead candidates targeting Pfs25 and Pfs230 antigens to prevent onwards transmission of naturally occurring parasites to a local mosquito strain is assessed using direct membrane feeding assays and murine antibodies in Burkina Faso. The transmission blocking activity of both candidates depends on the level of parasite exposure (as assessed by the mean number of oocysts in control mosquitoes) and antibody titers. A mathematical framework is devised to allow the efficacy of different candidates to be directly compared and determine the minimal antibody titers required to halt transmission in different settings. The increased efficacy with diminishing parasite exposure indicates that the efficacy of vaccines targeting either Pfs25 or Pfs230 may increase as malaria transmission declines. This has important implications for late-stage candidate selection and assessing how they can support the drive for malaria elimination.
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Affiliation(s)
- Anais Bompard
- MRC Centre for Outbreak Analysis and Modelling, Infectious Disease Epidemiology, Imperial College London, Norfolk Place, London, W2 1PG, United Kingdom.
| | - Dari F Da
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso.,Unité MIVEGEC, IRD 224-CNRS 5290-Université Montpellier, Montpellier, France
| | | | - Sumi Biswas
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Melissa Kapulu
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Teun Bousema
- Department of Medical Microbiology, Nijmegen, The Netherlands
| | - Thierry Lefèvre
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso.,Unité MIVEGEC, IRD 224-CNRS 5290-Université Montpellier, Montpellier, France.,Laboratoire mixte international sur les vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso
| | - Anna Cohuet
- Unité MIVEGEC, IRD 224-CNRS 5290-Université Montpellier, Montpellier, France
| | - Thomas S Churcher
- MRC Centre for Outbreak Analysis and Modelling, Infectious Disease Epidemiology, Imperial College London, Norfolk Place, London, W2 1PG, United Kingdom
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72
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Affiliation(s)
- Robert E. Sinden
- Department of Life Sciences, Imperial College London, London, United Kingdom
- * E-mail:
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73
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Sulyok M, Rückle T, Roth A, Mürbeth RE, Chalon S, Kerr N, Samec SS, Gobeau N, Calle CL, Ibáñez J, Sulyok Z, Held J, Gebru T, Granados P, Brückner S, Nguetse C, Mengue J, Lalremruata A, Sim BKL, Hoffman SL, Möhrle JJ, Kremsner PG, Mordmüller B. DSM265 for Plasmodium falciparum chemoprophylaxis: a randomised, double blinded, phase 1 trial with controlled human malaria infection. THE LANCET. INFECTIOUS DISEASES 2017; 17:636-644. [PMID: 28363637 PMCID: PMC5446410 DOI: 10.1016/s1473-3099(17)30139-1] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 02/05/2017] [Accepted: 02/16/2017] [Indexed: 12/17/2022]
Abstract
BACKGROUND A drug for causal (ie, pre-erythrocytic) prophylaxis of Plasmodium falciparum malaria with prolonged activity would substantially advance malaria control. DSM265 is an experimental antimalarial that selectively inhibits the parasite dihydroorotate dehydrogenase. DSM265 shows in vitro activity against liver and blood stages of P falciparum. We assessed the prophylactic activity of DSM265 against controlled human malaria infection (CHMI). METHODS At the Institute of Tropical Medicine, Eberhard Karls University (Tübingen, Germany), healthy, malaria-naive adults were allocated to receive 400 mg DSM265 or placebo either 1 day (cohort 1A) or 7 days (cohort 2) before CHMI by direct venous inoculation (DVI) of 3200 aseptic, purified, cryopreserved P falciparum sporozoites (PfSPZ Challenge; Sanaria Inc, Rockville, MD, USA). An additional group received daily atovaquone-proguanil (250-100 mg) for 9 days, starting 1 day before CHMI (cohort 1B). Allocation to DSM265, atovaquone-proguanil, or placebo was randomised by an interactive web response system. Allocation to cohort 1A and 1B was open-label, within cohorts 1A and 2, allocation to DSM265 and placebo was double-blinded. All treatments were given orally. Volunteers were treated with an antimalarial on day 28, or when parasitaemic, as detected by thick blood smear (TBS) microscopy. The primary efficacy endpoint was time-to-parasitaemia, assessed by TBS. All participants receiving at least one dose of chemoprophylaxis or placebo were considered for safety, those receiving PfSPZ Challenge for efficacy analyses. Log-rank test was used to compare time-to-parasitemia between interventions. The trial was registered with ClinicalTrials.gov, number NCT02450578. FINDINGS 22 participants were enrolled between Oct 23, 2015, and Jan 18, 2016. Five participants received 400 mg DSM265 and two participants received placebo 1 day before CHMI (cohort 1A), six participants received daily atovaquone-proguanil 1 day before CHMI (cohort 1B), and six participants received 400 mg DSM265 and two participants received placebo 7 days before CHMI (cohort 2). Five of five participants receiving DSM265 1 day before CHMI and six of six in the atovaquone-proguanil cohort were protected, whereas placebo recipients (two of two) developed malaria on days 11 and 14. When given 7 days before CHMI, three of six volunteers receiving DSM265 became TBS positive on days 11, 13, and 24. The remaining three DSM265-treated, TBS-negative participants of cohort 2 developed transient submicroscopic parasitaemia. Both participants receiving placebo 7 days before CHMI became TBS positive on day 11. The only possible DSM265-related adverse event was a moderate transient elevation in serum bilirubin in one participant. INTERPRETATION A single dose of 400 mg DSM265 was well tolerated and had causal prophylactic activity when given 1 day before CHMI. Future trials are needed to investigate further the use of DSM265 for the prophylaxis of malaria. FUNDING Global Health Innovative Technology Fund, Wellcome Trust, Bill & Melinda Gates Foundation through Medicines for Malaria Venture, and the German Center for Infection Research.
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Affiliation(s)
- Mihály Sulyok
- Institute of Tropical Medicine, and German Center for Infection Research, partner site Tübingen, Eberhard Karls University, Tübingen, Germany.
| | | | - Alexandra Roth
- Institute of Tropical Medicine, and German Center for Infection Research, partner site Tübingen, Eberhard Karls University, Tübingen, Germany
| | - Raymund E Mürbeth
- Institute of Tropical Medicine, and German Center for Infection Research, partner site Tübingen, Eberhard Karls University, Tübingen, Germany
| | | | - Nicola Kerr
- Medicines for Malaria Venture, Geneva, Switzerland
| | | | | | - Carlos Lamsfus Calle
- Institute of Tropical Medicine, and German Center for Infection Research, partner site Tübingen, Eberhard Karls University, Tübingen, Germany
| | - Javier Ibáñez
- Institute of Tropical Medicine, and German Center for Infection Research, partner site Tübingen, Eberhard Karls University, Tübingen, Germany
| | - Zita Sulyok
- Institute of Tropical Medicine, and German Center for Infection Research, partner site Tübingen, Eberhard Karls University, Tübingen, Germany
| | - Jana Held
- Institute of Tropical Medicine, and German Center for Infection Research, partner site Tübingen, Eberhard Karls University, Tübingen, Germany
| | - Tamirat Gebru
- Institute of Tropical Medicine, and German Center for Infection Research, partner site Tübingen, Eberhard Karls University, Tübingen, Germany
| | - Patricia Granados
- Institute of Tropical Medicine, and German Center for Infection Research, partner site Tübingen, Eberhard Karls University, Tübingen, Germany
| | - Sina Brückner
- Institute of Tropical Medicine, and German Center for Infection Research, partner site Tübingen, Eberhard Karls University, Tübingen, Germany
| | - Christian Nguetse
- Institute of Tropical Medicine, and German Center for Infection Research, partner site Tübingen, Eberhard Karls University, Tübingen, Germany
| | - Juliana Mengue
- Institute of Tropical Medicine, and German Center for Infection Research, partner site Tübingen, Eberhard Karls University, Tübingen, Germany
| | - Albert Lalremruata
- Institute of Tropical Medicine, and German Center for Infection Research, partner site Tübingen, Eberhard Karls University, Tübingen, Germany
| | | | | | | | - Peter G Kremsner
- Institute of Tropical Medicine, and German Center for Infection Research, partner site Tübingen, Eberhard Karls University, Tübingen, Germany
| | - Benjamin Mordmüller
- Institute of Tropical Medicine, and German Center for Infection Research, partner site Tübingen, Eberhard Karls University, Tübingen, Germany
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