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Markwalter CF, Petersen JEV, Zeno EE, Sumner KM, Freedman E, Mangeni JN, Abel L, Obala AA, Prudhomme-O’Meara W, Taylor SM. Symptomatic malaria enhances protection from reinfection with homologous Plasmodium falciparum parasites. PLoS Pathog 2023; 19:e1011442. [PMID: 37307293 PMCID: PMC10289385 DOI: 10.1371/journal.ppat.1011442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 06/23/2023] [Accepted: 05/24/2023] [Indexed: 06/14/2023] Open
Abstract
A signature remains elusive of naturally-acquired immunity against Plasmodium falciparum. We identified P. falciparum in a 14-month cohort of 239 people in Kenya, genotyped at immunogenic parasite targets expressed in the pre-erythrocytic (circumsporozoite protein, CSP) and blood (apical membrane antigen 1, AMA-1) stages, and classified into epitope type based on variants in the DV10, Th2R, and Th3R epitopes in CSP and the c1L region of AMA-1. Compared to asymptomatic index infections, symptomatic malaria was associated with reduced reinfection by parasites bearing homologous CSP-Th2R (adjusted hazard ratio [aHR]:0.63; 95% CI:0.45-0.89; p = 0.008) CSP-Th3R (aHR:0.71; 95% CI:0.52-0.97; p = 0.033), and AMA-1 c1L (aHR:0.63; 95% CI:0.43-0.94; p = 0.022) epitope types. The association of symptomatic malaria with reduced hazard of homologous reinfection was strongest for rare epitope types. Symptomatic malaria provides more durable protection against reinfection with parasites bearing homologous epitope types. The phenotype represents a legible molecular epidemiologic signature of naturally-acquired immunity by which to identify new antigen targets.
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Affiliation(s)
- Christine F. Markwalter
- Duke Global Health Institute, Duke University, Durham, North Carolina, United States of America
| | - Jens E. V. Petersen
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, North Carolina, United States of America
| | - Erica E. Zeno
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, North Carolina, United States of America
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Kelsey M. Sumner
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, North Carolina, United States of America
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Elizabeth Freedman
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, North Carolina, United States of America
| | - Judith N. Mangeni
- School of Public Health, College of Health Sciences, Moi University, Eldoret, Kenya
| | - Lucy Abel
- Academic Model Providing Access to Healthcare, Moi Teaching and Referral Hospital, Eldoret, Kenya
| | - Andrew A. Obala
- School of Medicine, College of Health Sciences, Moi University, Eldoret, Kenya
| | - Wendy Prudhomme-O’Meara
- Duke Global Health Institute, Duke University, Durham, North Carolina, United States of America
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, North Carolina, United States of America
- School of Public Health, College of Health Sciences, Moi University, Eldoret, Kenya
| | - Steve M. Taylor
- Duke Global Health Institute, Duke University, Durham, North Carolina, United States of America
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, North Carolina, United States of America
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina, United States of America
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Valletta JJ, Addy JW, Reid AJ, Ndungu FM, Bediako Y, Mwacharo J, Mohammed KS, Musyoki J, Ngoi JM, Wambua J, Otieno E, Berriman M, Bejon P, Marsh K, Langhorne J, Newbold CI, Recker M. Individual-level variations in malaria susceptibility and acquisition of clinical protection. Wellcome Open Res 2022; 6:22. [PMID: 35310901 PMCID: PMC8914138 DOI: 10.12688/wellcomeopenres.16524.3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/22/2022] [Indexed: 11/29/2022] Open
Abstract
After decades of research, our understanding of when and why individuals infected with
Plasmodium falciparum develop clinical malaria is still limited. Correlates of immune protection are often sought through prospective cohort studies, where measured host factors are correlated against the incidence of clinical disease over a set period of time. However, robustly inferring individual-level protection from these population-level findings has proved difficult due to small effect sizes and high levels of variance underlying such data. In order to better understand the nature of these inter-individual variations, we analysed the long-term malaria epidemiology of children ≤12 years old growing up under seasonal exposure to the parasite in the sub-location of Junju, Kenya. Despite the cohort’s limited geographic expanse (ca. 3km x 10km), our data reveal a high degree of spatial and temporal variability in malaria prevalence and incidence rates, causing individuals to experience varying levels of exposure to the parasite at different times during their life. Analysing individual-level infection histories further reveal an unexpectedly high variability in the rate at which children experience clinical malaria episodes. Besides exposure to the parasite, measured as disease prevalence in the surrounding area, we find that the birth time of year has an independent effect on the individual’s risk of experiencing a clinical episode. Furthermore, our analyses reveal that those children with a history of an above average number of episodes are more likely to experience further episodes during the upcoming transmission season. These findings are indicative of phenotypic differences in the rates by which children acquire clinical protection to malaria and offer important insights into the natural variability underlying malaria epidemiology.
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Affiliation(s)
- John Joseph Valletta
- School of Mathematics and Statistics, University of St. Andrews, St. Andrews, UK
| | - John W.G. Addy
- Malaria Immunology Laboratory, Francis Crick Institute, London, UK
| | - Adam J. Reid
- Parasite Genomics, Wellcome Trust Sanger Institute, Hinxton, UK
| | | | - Yaw Bediako
- Malaria Immunology Laboratory, Francis Crick Institute, London, UK
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, Accra, Ghana
| | | | | | | | - Joyce Mwongeli Ngoi
- KEMRI/Wellcome Trust Research Programme, Kilifi, Kenya
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, Accra, Ghana
| | - Joshua Wambua
- KEMRI/Wellcome Trust Research Programme, Kilifi, Kenya
| | - Edward Otieno
- KEMRI/Wellcome Trust Research Programme, Kilifi, Kenya
| | - Matt Berriman
- Parasite Genomics, Wellcome Trust Sanger Institute, Hinxton, UK
| | - Philip Bejon
- KEMRI/Wellcome Trust Research Programme, Kilifi, Kenya
| | - Kevin Marsh
- Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| | - Jean Langhorne
- Malaria Immunology Laboratory, Francis Crick Institute, London, UK
| | - Chris I. Newbold
- Parasite Genomics, Wellcome Trust Sanger Institute, Hinxton, UK
- MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| | - Mario Recker
- Centre for Ecology and Conservation, University of Exeter, Penryn, UK
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Nwaneli EI, Nri-ezedi CA, Okeke KN, Edokwe ES, Echendu ST, Iloh KK. Congenital cerebral malaria: a masquerader in a neonate. Malar J 2022; 21:34. [PMID: 35123479 PMCID: PMC8817602 DOI: 10.1186/s12936-022-04056-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 01/19/2022] [Indexed: 11/13/2022] Open
Abstract
Background Congenital malaria, which is caused by vertical transmission of malaria parasites, is a potentially fatal condition. Despite Africa’s high malaria burden, congenital malaria is not routinely screened for, and thus may go undiagnosed. Malaria, if not treated promptly, can quickly progress to severe forms and result in death. Severe congenital malaria is believed to be uncommon in neonates due to maternal antibodies, fetal haemoglobin, and the placenta’s sieving effect. The majority of reported cases were classified as having severe anaemia. Following a thorough review of the literature, only one case of congenital cerebral malaria (CCM) has been reported, and it was misdiagnosed. Case presentation A 5-day-old Nigerian neonate born to an apparently healthy mother initially displayed characteristics consistent with neonatal sepsis and severe neonatal hyperbilirubinaemia. He quickly developed characteristics consistent with meningitis. Surprisingly, the peripheral blood film revealed evidence of malaria parasites, which was immediately confirmed by Giemsa-stained thick and thin blood film microscopy for malaria. The patient was diagnosed with congenital cerebral malaria. The medication was modified to parenteral artesunate followed by oral artemisinin combination therapy. The neonate recovered fully and had no neurological deficits on follow up. Conclusion Because CCM and infant meningitis have similar clinical presentations, CCM could be misdiagnosed and lead to death if there isn’t a high index of suspicion.
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4
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Kimingi HW, Kinyua AW, Achieng NA, Wambui KM, Mwangi S, Nguti R, Kivisi CA, Jensen ATR, Bejon P, Kapulu MC, Abdi AI, Kinyanjui SM. Breadth of Antibodies to Plasmodium falciparum Variant Surface Antigens Is Associated With Immunity in a Controlled Human Malaria Infection Study. Front Immunol 2022; 13:894770. [PMID: 35711446 PMCID: PMC9195513 DOI: 10.3389/fimmu.2022.894770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Accepted: 04/27/2022] [Indexed: 11/05/2022] Open
Abstract
Background Plasmodium falciparum variant surface antigens (VSAs) contribute to malaria pathogenesis by mediating cytoadhesion of infected red blood cells to the microvasculature endothelium. In this study, we investigated the association between anti-VSA antibodies and clinical outcome in a controlled human malaria infection (CHMI) study. Method We used flow cytometry and ELISA to measure levels of IgG antibodies to VSAs of five heterologous and one homologous P. falciparum parasite isolates, and to two PfEMP1 DBLβ domains in blood samples collected a day before the challenge and 14 days after infection. We also measured the ability of an individual's plasma to inhibit the interaction between PfEMP1 and ICAM1 using competition ELISA. We then assessed the association between the antibody levels, function, and CHMI defined clinical outcome during a 21-day follow-up period post infection using Cox proportional hazards regression. Results Antibody levels to the individual isolate VSAs, or to two ICAM1-binding DBLβ domains of PfEMP1, were not associated with a significantly reduced risk of developing parasitemia or of meeting treatment criteria after the challenge after adjusting for exposure. However, anti-VSA antibody breadth (i.e., cumulative response to all the isolates) was a significant predictor of reduced risk of requiring treatment [HR 0.23 (0.10-0.50) p= 0.0002]. Conclusion The breadth of IgG antibodies to VSAs, but not to individual isolate VSAs, is associated with protection in CHMI.
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Affiliation(s)
- Hannah W. Kimingi
- Kenya Medical Research Institute (KEMRI) Wellcome Trust Research Programme, Kilifi, Kenya
- Department of Biological Sciences, Pwani University, Kilifi, Kenya
| | - Ann W. Kinyua
- Kenya Medical Research Institute (KEMRI) Wellcome Trust Research Programme, Kilifi, Kenya
| | - Nicole A. Achieng
- Kenya Medical Research Institute (KEMRI) Wellcome Trust Research Programme, Kilifi, Kenya
| | - Kennedy M. Wambui
- Kenya Medical Research Institute (KEMRI) Wellcome Trust Research Programme, Kilifi, Kenya
- School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Shaban Mwangi
- Kenya Medical Research Institute (KEMRI) Wellcome Trust Research Programme, Kilifi, Kenya
| | - Roselyne Nguti
- Kenya Medical Research Institute (KEMRI) Wellcome Trust Research Programme, Kilifi, Kenya
- Department of Biological Sciences, Pwani University, Kilifi, Kenya
| | - Cheryl A. Kivisi
- Department of Biological Sciences, Pwani University, Kilifi, Kenya
- Pwani University Bioscience Research Centre, Pwani University, Kilifi, Kenya
| | - Anja T. R. Jensen
- Centre for Medical Parasitology, Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Philip Bejon
- Kenya Medical Research Institute (KEMRI) Wellcome Trust Research Programme, Kilifi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University Oxford, Oxford, United Kingdom
| | - Melisa C. Kapulu
- Kenya Medical Research Institute (KEMRI) Wellcome Trust Research Programme, Kilifi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University Oxford, Oxford, United Kingdom
| | - Abdirahman I. Abdi
- Kenya Medical Research Institute (KEMRI) Wellcome Trust Research Programme, Kilifi, Kenya
- Pwani University Bioscience Research Centre, Pwani University, Kilifi, Kenya
| | - Samson M. Kinyanjui
- Kenya Medical Research Institute (KEMRI) Wellcome Trust Research Programme, Kilifi, Kenya
- Pwani University Bioscience Research Centre, Pwani University, Kilifi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University Oxford, Oxford, United Kingdom
- School of Business Studies, Strathmore University, Nairobi, Kenya
- *Correspondence: Samson M. Kinyanjui,
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5
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Valletta JJ, Addy JW, Reid AJ, Ndungu FM, Bediako Y, Mwacharo J, Said K, Musyoki J, Ngoi JM, Wambua J, Otieno E, Berriman M, Bejon P, Marsh K, Langhorne J, Newbold CI, Recker M. Individual-level variations in malaria susceptibility and acquisition of clinical protection. Wellcome Open Res 2021; 6:22. [DOI: 10.12688/wellcomeopenres.16524.2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/06/2021] [Indexed: 11/20/2022] Open
Abstract
After decades of research, our understanding of when and why individuals infected with Plasmodium falciparum develop clinical malaria is still limited. Correlates of immune protection are often sought through prospective cohort studies, where measured host factors are correlated against the incidence of clinical disease over a set period of time. However, robustly inferring individual-level protection from these population-level findings has proved difficult due to small effect sizes and high levels of variance underlying such data. In order to better understand the nature of these inter-individual variations, we analysed the long-term malaria epidemiology of children ≤12 years old growing up under seasonal exposure to the parasite in the sub-location of Junju, Kenya. Despite the cohort’s limited geographic expanse (ca. 3km x 10km), our data reveal a high degree of spatial and temporal variability in malaria prevalence and incidence rates, causing individuals to experience varying levels of exposure to the parasite at different times during their life. Analysing individual-level infection histories further reveal an unexpectedly high variability in the rate at which children experience clinical malaria episodes. Besides exposure to the parasite, measured as disease prevalence in the surrounding area, we find that the birth time of year has an independent effect on the individual’s risk of experiencing a clinical episode. Furthermore, our analyses reveal that those children with a history of an above average number of episodes are more likely to experience further episodes during the upcoming transmission season. These findings are indicative of phenotypic differences in the rates by which children acquire clinical protection to malaria and offer important insights into the natural variability underlying malaria epidemiology.
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6
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Songsaigath S, Makiuchi T, Putaporntip C, Pattanawong U, Kuamsab N, Tachibana H, Jongwutiwes S. Immunoglobulin G responses to variant forms of Plasmodium vivax merozoite surface protein 9 upon natural infection in Thailand. Sci Rep 2021; 11:3201. [PMID: 33547377 PMCID: PMC7864938 DOI: 10.1038/s41598-021-82928-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 01/25/2021] [Indexed: 11/30/2022] Open
Abstract
Merozoite surface protein 9 (MSP9) constitutes a ligand complex involved in erythrocyte invasion by malarial merozoites and is a promising vaccine target. Plasmodium vivax MSP9 (PvMSP9) is immunogenic upon natural malaria exposure. To address whether sequence diversity in PvMSP9 among field isolates could affect natural antibody responses, the recombinant proteins representing two variants each for the N- and the C-terminal domains of PvMSP-9 were used as antigens to assess antibody reactivity among 246 P. vivax-infected patients’ sera from Tak and Ubon Ratchathani Provinces in Thailand. Results revealed that the seropositivity rates of IgG antibodies to the N-terminal antigens were higher than those to the C-terminal antigens (87.80% vs. 67.48%). Most seropositive sera were reactive to both variants, suggesting the presence of common epitopes. Variant-specific antibodies to the N- and the C-terminal antigens were detected in 15.85% and 16.70% of serum samples, respectively. These seropositivity rates were not significant difference between provinces. The seropositivity rates, levels and avidity of anti-PvMSP9 antibodies exhibited positive trends towards increasing malaria episodes. The IgG isotype responses to the N- and the C-terminal antigens were mainly IgG1 and IgG3. The profile of IgG responses may have implications for development of PvMSP9-based vaccine.
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Affiliation(s)
- Sunisa Songsaigath
- Department of Infectious Diseases, Tokai University School of Medicine, Isehara, Kanagawa, Japan.,Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.,Inter-Department Program of Biomedical Sciences, Faculty of Graduate School, Chulalongkorn University, Bangkok, Thailand
| | - Takashi Makiuchi
- Department of Infectious Diseases, Tokai University School of Medicine, Isehara, Kanagawa, Japan
| | - Chaturong Putaporntip
- Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Urassaya Pattanawong
- Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Napaporn Kuamsab
- Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Hiroshi Tachibana
- Department of Infectious Diseases, Tokai University School of Medicine, Isehara, Kanagawa, Japan.
| | - Somchai Jongwutiwes
- Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
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7
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Valletta JJ, Addy JW, Reid AJ, Ndungu FM, Bediako Y, Mwacharo J, Said K, Musyoki J, Ngoi JM, Wambua J, Otieno E, Berriman M, Bejon P, Marsh K, Langhorne J, Newbold CI, Recker M. Individual-level variations in malaria susceptibility and acquisition of clinical protection. Wellcome Open Res 2021; 6:22. [DOI: 10.12688/wellcomeopenres.16524.1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/26/2021] [Indexed: 11/20/2022] Open
Abstract
After decades of research, our understanding of when and why individuals infected with Plasmodium falciparum develop clinical malaria is still limited. Correlates of immune protection are often sought through prospective cohort studies, where measured host factors are correlated against the incidence of clinical disease over a set period of time. However, robustly inferring individual-level protection from these population-level findings has proved difficult due to small effect sizes and high levels of variance underlying such data. In order to better understand the nature of these inter-individual variations, we analysed the long-term malaria epidemiology of children ≤12 years old growing up under seasonal exposure to the parasite in the sub-location of Junju, Kenya. Despite the cohort’s limited geographic expanse (ca. 3km x 10km), our data reveal a high degree of spatial and temporal variability in malaria prevalence and incidence rates, causing individuals to experience varying levels of exposure to the parasite at different times during their life. Analysing individual-level infection histories further reveal an unexpectedly high variability in the rate at which children experience clinical malaria episodes. Besides exposure to the parasite, measured as disease prevalence in the surrounding area, we find that the birth time of year has an independent effect on the individual’s risk of experiencing a clinical episode. Furthermore, our analyses reveal that those children with a history of an above average number of episodes are more likely to experience further episodes during the upcoming transmission season. These findings are indicative of phenotypic differences in the rates by which children acquire clinical protection to malaria and offer important insights into the natural variability underlying malaria epidemiology.
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8
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Nyarko PB, Claessens A. Understanding Host-Pathogen-Vector Interactions with Chronic Asymptomatic Malaria Infections. Trends Parasitol 2020; 37:195-204. [PMID: 33127332 DOI: 10.1016/j.pt.2020.09.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 09/28/2020] [Accepted: 09/30/2020] [Indexed: 01/06/2023]
Abstract
The last malaria parasite standing will display effective adaptations to selective forces. While substantial progress has been made in reducing malaria mortality, eradication will require elimination of all Plasmodium parasites, including those in asymptomatic infections. These typically chronic, low-density infections are difficult to detect, yet can persist for months. We argue that asymptomatic infection is the parasite's best asset for survival but it can be exploited if studied as a new model for host-pathogen-vector interactions. Regular sampling from cohorts of asymptomatic individuals can provide a means to investigate continuous parasite development within its natural host. State-of-the-art techniques can now be applied to such infections. This approach may reveal key molecular drivers of chronic infections - a critical step for malaria eradication.
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Affiliation(s)
- Prince B Nyarko
- Laboratory of Pathogen-Host Interaction (LPHI), CNRS, University of Montpellier, France
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9
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Zhang X, Alexander N, Leonardi I, Mason C, Kirkman LA, Deitsch KW. Rapid antigen diversification through mitotic recombination in the human malaria parasite Plasmodium falciparum. PLoS Biol 2019; 17:e3000271. [PMID: 31083650 PMCID: PMC6532940 DOI: 10.1371/journal.pbio.3000271] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 05/23/2019] [Accepted: 04/30/2019] [Indexed: 11/18/2022] Open
Abstract
Malaria parasites possess the remarkable ability to maintain chronic infections that fail to elicit a protective immune response, characteristics that have stymied vaccine development and cause people living in endemic regions to remain at risk of malaria despite previous exposure to the disease. These traits stem from the tremendous antigenic diversity displayed by parasites circulating in the field. For Plasmodium falciparum, the most virulent of the human malaria parasites, this diversity is exemplified by the variant gene family called var, which encodes the major surface antigen displayed on infected red blood cells (RBCs). This gene family exhibits virtually limitless diversity when var gene repertoires from different parasite isolates are compared. Previous studies indicated that this remarkable genome plasticity results from extensive ectopic recombination between var genes during mitotic replication; however, the molecular mechanisms that direct this process to antigen-encoding loci while the rest of the genome remains relatively stable were not determined. Using targeted DNA double-strand breaks (DSBs) and long-read whole-genome sequencing, we show that a single break within an antigen-encoding region of the genome can result in a cascade of recombination events leading to the generation of multiple chimeric var genes, a process that can greatly accelerate the generation of diversity within this family. We also found that recombinations did not occur randomly, but rather high-probability, specific recombination products were observed repeatedly. These results provide a molecular basis for previously described structured rearrangements that drive diversification of this highly polymorphic gene family.
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Affiliation(s)
- Xu Zhang
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America
| | - Noah Alexander
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York, United States of America
| | - Irina Leonardi
- Jill Roberts Center for Inflammatory Bowel Disease, Weill Cornell Medical College, New York, New York, United States of America
| | - Christopher Mason
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York, United States of America
- HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medical College, New York, New York, United States of America
- Feil Family Brain and Mind Research Institute, Weill Cornell Medical College, New York, New York, United States of America
- WorldQuant Initiative for Quantitative Prediction, Weill Cornell Medical College, New York, New York, United States of America
| | - Laura A. Kirkman
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America
- Department of Internal Medicine, Division of Infectious Diseases, Weill Cornell Medical College, New York, New York, United States of America
| | - Kirk W. Deitsch
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America
- * E-mail:
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10
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Antwi-Baffour S, Kyeremeh R, Buabeng D, Adjei JK, Aryeh C, Kpentey G, Seidu MA. Correlation of malaria parasitaemia with peripheral blood monocyte to lymphocyte ratio as indicator of susceptibility to severe malaria in Ghanaian children. Malar J 2018; 17:419. [PMID: 30419923 PMCID: PMC6233557 DOI: 10.1186/s12936-018-2569-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 11/03/2018] [Indexed: 11/10/2022] Open
Abstract
Background Even though malaria is generally on the decline due extensive control and elimination efforts, it still remains a public health problem for over 40% of the world’s population. During the course of malaria infection, parasites and red blood cells come under oxidative stress and there is host immune response in an attempt to protect the red blood cells. The frequency of monocytes and lymphocytes in peripheral blood might, therefore, be expected to reflect the state of an individual’s immune response to the infection. Circulating monocytes and lymphocytes could therefore serve as an index in relation to malaria parasitaemia. The purpose of this study was to determine whether the relative count of monocytes to lymphocytes in peripheral blood (M:L ratio) can predict parasitaemia and, therefore, the severity of malaria infection. Methods Two millilitre of venous blood sample were taken from participants by venisection into anticoagulant tubes. Thick and thin blood films were made and stained with Giemsa and examined for malaria parasites. Whole blood specimen were analysed for full blood count using ABX Pentra 60 C+ automated haematological analyzer. Data was entered into Microsoft Word and analysed using Statistical Package for Social Sciences (SPSS, Version 20.0) and Graphpad prism. Spearman’s correlation was used to determine correlation between occurrences of clinical malaria and the monocytes and lymphocytes ratio. Statistical significance was taken as p ≤ 0.05 with 95% confidence interval. Results The study comprised of 1629 (m = 896; f = 733) children up to 5 years presenting with clinical malaria as cases and 445 (m = 257; f = 188) apparently healthy children as controls. The results indicated that there was a significant positive correlation between the monocytes to lymphocytes ratio and the presence of parasites (p = 0.04) and the level of parasitaemia within the age group of 0–3 years (p = 0.02) and 4–5 years (p = 0.03). Conclusions The monocyte to lymphocyte ratio obtained correlated positively with the presence of malaria as well as the level of parasitaemia. The outcome of this work implies that monocyte to lymphocyte ratio can be used to predict the level of parasitaemia and together with other factors, the development of severe malaria.
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Affiliation(s)
- Samuel Antwi-Baffour
- Department of Medical Laboratory Sciences, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, P. O. Box KB 143, Korle-Bu, Accra, Ghana.
| | - Ransford Kyeremeh
- Department of Medical Laboratory Sciences, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, P. O. Box KB 143, Korle-Bu, Accra, Ghana.,Central Laboratories, Korle-bu Teaching Hospital, Korle-bu, Accra, Ghana
| | - Dorcas Buabeng
- Department of Medical Laboratory Sciences, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, P. O. Box KB 143, Korle-Bu, Accra, Ghana.,Department of Haematology, Wa Regional Hospital, Wa, Ghana
| | - Jonathan Kofi Adjei
- Department of Medical Laboratory Sciences, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, P. O. Box KB 143, Korle-Bu, Accra, Ghana.,Department of Haematology, Sunyani Regional Hospital, Sunyani, Ghana
| | - Claudia Aryeh
- Department of Medical Laboratory Sciences, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, P. O. Box KB 143, Korle-Bu, Accra, Ghana
| | - George Kpentey
- Central Laboratories, Korle-bu Teaching Hospital, Korle-bu, Accra, Ghana
| | - Mahmood Abdulai Seidu
- Department of Medical Laboratory Sciences, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, P. O. Box KB 143, Korle-Bu, Accra, Ghana.,Department of Haematology, Wa Regional Hospital, Wa, Ghana
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Abrard S, Cousin B, Fleury C, Fouquet O, Beydon L. Cardiopulmonary Bypass and Malaria Relapse. J Cardiothorac Vasc Anesth 2018; 32:2282-2285. [DOI: 10.1053/j.jvca.2017.12.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Indexed: 11/11/2022]
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12
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Fried M, Kurtis JD, Swihart B, Morrison R, Pond-Tor S, Barry A, Sidibe Y, Keita S, Mahamar A, Andemel N, Attaher O, Dembele AB, Cisse KB, Diarra BS, Kanoute MB, Narum DL, Dicko A, Duffy PE. Antibody levels to recombinant VAR2CSA domains vary with Plasmodium falciparum parasitaemia, gestational age, and gravidity, but do not predict pregnancy outcomes. Malar J 2018. [PMID: 29523137 PMCID: PMC5845157 DOI: 10.1186/s12936-018-2258-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Background Maternal malaria is a tropical scourge associated with poor pregnancy outcomes. Women become resistant to Plasmodium falciparum pregnancy malaria as they acquire antibodies to the variant surface antigen VAR2CSA, a leading vaccine candidate. Because malaria infection may increase VAR2CSA antibody levels and thereby confound analyses of immune protection, gravidity-dependent changes in antibody levels during and after infection, and the effect of VAR2CSA antibodies on pregnancy outcomes were evaluated. Methods Pregnant women enrolled in a longitudinal cohort study of mother-infant pairs in Ouelessebougou, Mali provided plasma samples at enrollment, gestational week 30–32, and delivery. Antibody levels to VAR2CSA domains were measured using a multiplex bead-based assay. Results Antibody levels to VAR2CSA were higher in multigravidae than primigravidae. Malaria infection was associated with increased antibody levels to VAR2CSA domains. In primigravidae but not in secundigravidae or multigravidae, antibodies levels sharply declined after an infection. A relationship between any VAR2CSA antibody specificity and protection from adverse pregnancy outcomes was not detected. Conclusions During malaria infection, primigravidae acquire short-lived antibodies. The lack of an association between VAR2CSA domain antibody reactivity and improved pregnancy outcomes suggests that the recombinant proteins may not present native epitopes targeted by protective antibodies. Electronic supplementary material The online version of this article (10.1186/s12936-018-2258-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Michal Fried
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD, USA.
| | - Jonathan D Kurtis
- Center for International Health Research, Rhode Island Hospital, Brown University Medical School, Providence, RI, USA
| | - Bruce Swihart
- Biostatistics Research Branch, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD, USA
| | - Robert Morrison
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD, USA
| | - Sunthorn Pond-Tor
- Center for International Health Research, Rhode Island Hospital, Brown University Medical School, Providence, RI, USA
| | - Amadou Barry
- Malaria Research & Training Center, Faculty of Medicine, Pharmacy and Dentistry, University of Sciences Techniques and Technologies of Bamako, P.O Box 1805, Bamako, Mali
| | - Youssoufa Sidibe
- Malaria Research & Training Center, Faculty of Medicine, Pharmacy and Dentistry, University of Sciences Techniques and Technologies of Bamako, P.O Box 1805, Bamako, Mali
| | - Sekouba Keita
- Malaria Research & Training Center, Faculty of Medicine, Pharmacy and Dentistry, University of Sciences Techniques and Technologies of Bamako, P.O Box 1805, Bamako, Mali
| | - Almahamoudou Mahamar
- Malaria Research & Training Center, Faculty of Medicine, Pharmacy and Dentistry, University of Sciences Techniques and Technologies of Bamako, P.O Box 1805, Bamako, Mali
| | - Naissem Andemel
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD, USA
| | - Oumar Attaher
- Malaria Research & Training Center, Faculty of Medicine, Pharmacy and Dentistry, University of Sciences Techniques and Technologies of Bamako, P.O Box 1805, Bamako, Mali
| | - Adama B Dembele
- Malaria Research & Training Center, Faculty of Medicine, Pharmacy and Dentistry, University of Sciences Techniques and Technologies of Bamako, P.O Box 1805, Bamako, Mali
| | - Kadidia B Cisse
- Malaria Research & Training Center, Faculty of Medicine, Pharmacy and Dentistry, University of Sciences Techniques and Technologies of Bamako, P.O Box 1805, Bamako, Mali
| | - Bacary S Diarra
- Malaria Research & Training Center, Faculty of Medicine, Pharmacy and Dentistry, University of Sciences Techniques and Technologies of Bamako, P.O Box 1805, Bamako, Mali
| | - Moussa B Kanoute
- Malaria Research & Training Center, Faculty of Medicine, Pharmacy and Dentistry, University of Sciences Techniques and Technologies of Bamako, P.O Box 1805, Bamako, Mali
| | - David L Narum
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD, USA
| | - Alassane Dicko
- Malaria Research & Training Center, Faculty of Medicine, Pharmacy and Dentistry, University of Sciences Techniques and Technologies of Bamako, P.O Box 1805, Bamako, Mali
| | - Patrick E Duffy
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD, USA
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Quintana MDP, Ch'ng JH, Moll K, Zandian A, Nilsson P, Idris ZM, Saiwaew S, Qundos U, Wahlgren M. Antibodies in children with malaria to PfEMP1, RIFIN and SURFIN expressed at the Plasmodium falciparum parasitized red blood cell surface. Sci Rep 2018; 8:3262. [PMID: 29459776 PMCID: PMC5818650 DOI: 10.1038/s41598-018-21026-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 01/12/2018] [Indexed: 01/21/2023] Open
Abstract
Naturally acquired antibodies to proteins expressed on the Plasmodium falciparum parasitized red blood cell (pRBC) surface steer the course of a malaria infection by reducing sequestration and stimulating phagocytosis of pRBC. Here we have studied a selection of proteins representing three different parasite gene families employing a well-characterized parasite with a severe malaria phenotype (FCR3S1.2). The presence of naturally acquired antibodies, impact on rosetting rate, surface reactivity and opsonization for phagocytosis in relation to different blood groups of the ABO system were assessed in a set of sera from children with mild or complicated malaria from an endemic area. We show that the naturally acquired immune responses, developed during malaria natural infection, have limited access to the pRBCs inside a blood group A rosette. The data also indicate that SURFIN4.2 may have a function at the pRBC surface, particularly during rosette formation, this role however needs to be further validated. Our results also indicate epitopes differentially recognized by rosette-disrupting antibodies on a peptide array. Antibodies towards parasite-derived proteins such as PfEMP1, RIFIN and SURFIN in combination with host factors, essentially the ABO blood group of a malaria patient, are suggested to determine the outcome of a malaria infection.
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Affiliation(s)
- Maria Del Pilar Quintana
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden.
| | - Jun-Hong Ch'ng
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden.,Department of Microbiology and Immunology, National University of Singapore, Singapore, Singapore
| | - Kirsten Moll
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Arash Zandian
- Affinity Proteomics, Science for Life Laboratory, School of Biotechnology, KTH-Royal Institutet of Technology, Stockholm, Sweden
| | - Peter Nilsson
- Affinity Proteomics, Science for Life Laboratory, School of Biotechnology, KTH-Royal Institutet of Technology, Stockholm, Sweden
| | - Zulkarnain Md Idris
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden.,Department of Parasitology and Medical Entomology, Faculty of Medicine, Universiti Kebangsaan, Malaysia Medical Centre, Kuala Lumpur, Malaysia
| | - Somporn Saiwaew
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Ulrika Qundos
- Affinity Proteomics, Science for Life Laboratory, School of Biotechnology, KTH-Royal Institutet of Technology, Stockholm, Sweden
| | - Mats Wahlgren
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden.
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Amoah LE, Acquah FK, Ayanful-Torgby R, Oppong A, Abankwa J, Obboh EK, Singh SK, Theisen M. Dynamics of anti-MSP3 and Pfs230 antibody responses and multiplicity of infection in asymptomatic children from southern Ghana. Parasit Vectors 2018; 11:13. [PMID: 29304870 PMCID: PMC5755320 DOI: 10.1186/s13071-017-2607-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 12/25/2017] [Indexed: 11/25/2022] Open
Abstract
Background During a Plasmodium infection, exposure of human host immune cells to both the asexual and the sexual stages of the parasite elicit immune responses. These responses may be protective and prevent the development of high parasitaemia and its associated clinical symptoms, or block the transmission of malaria to an uninfected person. This study aimed at examining the dynamics of naturally acquired immune responses against the asexual and sexual forms of Plasmodium falciparum as well as assessing differences in the multiplicity of infection (MOI) in asymptomatic Ghanaian children living in two communities with varying malaria transmission intensities. Methods School children aged between 6 and 12 years were recruited from Obom, a high malaria prevalence setting and Abura, a low malaria prevalence setting and enrolled in monthly multiple cross sectional surveys between February and May 2015. Filter paper blood blots (DBS) as well as thick and thin blood smears were made from finger-pricked blood at each visit. Plasmodium falciparum parasite prevalence was determined by microscopy and PCR. Serum eluted from the DBS were used to assess anti-Pfs230 (sexual stage) and anti-MSP3 (asexual stage) antibody levels using indirect ELISA and DNA extracted from the DBS used to assess MOI. Results Malaria parasite point prevalence and MOI throughout the study was higher in Obom than Abura. The trend of parasite prevalence estimated by microscopy was similar to that determined by PCR in Obom but not in Abura. The trend of MSP3 antibody seroprevalence followed that of PCR-estimated parasite prevalence in Obom, while in Abura the trend of Pfs230 antibody seroprevalence followed that of PCR-estimated parasite prevalence. Conclusions Microscopy can more accurately predict changes in parasite prevalence in high transmission settings than low transmission settings. In high transmission settings, P. falciparum parasite prevalence can predict antibody seroprevalence to MSP3, whilst in low transmission settings, seroprevalence against Pfs230 may be a useful predictor of parasite prevalence. Electronic supplementary material The online version of this article (10.1186/s13071-017-2607-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Linda E Amoah
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana.
| | - Festus K Acquah
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
| | - Ruth Ayanful-Torgby
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
| | - Akua Oppong
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
| | - Joana Abankwa
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
| | - Evans K Obboh
- School of Medical Sciences, University of Cape Coast, Cape Coast, Ghana
| | - Susheel K Singh
- Department for Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark.,Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark
| | - Michael Theisen
- Department for Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark.,Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark
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15
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Schieck E, Poole EJ, Rippert A, Peshu J, Sasi P, Borrmann S, Bull PC. Plasmodium falciparum variant erythrocyte surface antigens: a pilot study of antibody acquisition in recurrent natural infections. Malar J 2017; 16:450. [PMID: 29115961 PMCID: PMC5678811 DOI: 10.1186/s12936-017-2097-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 10/28/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND During intra-erythrocytic replication Plasmodium falciparum escapes the human host immune system by switching expression of variant surface antigens (VSA). Piecemeal acquisition of variant specific antibody responses to these antigens as a result of exposure to multiple re-infections has been proposed to play a role in acquisition of naturally acquired immunity. METHODS Immunofluorescence was used to explore the dynamics of anti-VSA IgG responses generated by children to (i) primary malaria episodes and (ii) recurrent P. falciparum infections. RESULTS Consistent with previous studies on anti-VSA responses, sera from each child taken at the time of recovery from their respective primary infection tended to recognize their own secondary parasites poorly. Additionally, compared to patients with reinfections by parasites of new merozoite surface protein 2 (MSP2) genotypes, baseline sera sampled from patients with persistent infections (recrudescence) tended to have higher recognition of heterologous parasites. This is consistent with the prediction that anti-VSA IgG responses may play a role in promoting chronic asymptomatic infections. CONCLUSIONS This pilot study validates the utility of recurrent natural malaria infections as a functional readout for examining the incremental acquisition of immunity to malaria.
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Affiliation(s)
- Elise Schieck
- Kenya Medical Research Institute/Wellcome Trust Research Programme, Center for Geographic Medicine Research-Coast, P. O. Box 428, Kilifi, 80108, Kenya. .,Institute of Hygiene, University of Heidelberg School of Medicine, 69120, Heidelberg, Germany. .,International Livestock Research Institute, Old Naivasha Road, P.O. Box 30709, Nairobi, 00100, Kenya.
| | - E Jane Poole
- International Livestock Research Institute, Old Naivasha Road, Nairobi, Kenya
| | - Anja Rippert
- Institute of Hygiene, University of Heidelberg School of Medicine, 69120, Heidelberg, Germany.,Department of Infectious Diseases, Molecular Virology, University Hospital Heidelberg, Heidelberg, Germany
| | - Judy Peshu
- Kenya Medical Research Institute/Wellcome Trust Research Programme, Center for Geographic Medicine Research-Coast, P. O. Box 428, Kilifi, 80108, Kenya
| | - Philip Sasi
- Department of Clinical Pharmacology, School of Medicine, Muhimbili University of Health and Allied Sciences, P.O. Box 65010, Dar es Salaam, Tanzania
| | - Steffen Borrmann
- Kenya Medical Research Institute/Wellcome Trust Research Programme, Center for Geographic Medicine Research-Coast, P. O. Box 428, Kilifi, 80108, Kenya.,German Center for Infection Research (DZIF), Wilhelmstraße 27, 72074, Tübingen, Germany.,Institute for Tropical Medicine, University of Tübingen, Tübingen, Germany
| | - Peter C Bull
- Kenya Medical Research Institute/Wellcome Trust Research Programme, Center for Geographic Medicine Research-Coast, P. O. Box 428, Kilifi, 80108, Kenya.,Nuffield Department of Medicine, Centre for Tropical Medicine, Oxford University, Oxford, OX3 7LJ, UK.,Department of Pathology, Cambridge University, Tennis Court Road, Cambridge, CB2 1QP, UK
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16
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Stephens JK, Kyei-Baafour E, Dickson EK, Ofori JK, Ofori MF, Wilson ML, Quakyi IA, Akanmori BD. Effect of IPTp on Plasmodium falciparum antibody levels among pregnant women and their babies in a sub-urban coastal area in Ghana. Malar J 2017; 16:224. [PMID: 28549426 PMCID: PMC5446726 DOI: 10.1186/s12936-017-1857-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Accepted: 05/12/2017] [Indexed: 12/31/2022] Open
Abstract
Background Women exposed to Plasmodium infection develop antibodies and become semi-immune. This immunity is suppressed during pregnancy making both the pregnant woman and the foetus vulnerable to the adverse effects of malaria, particularly by Plasmodium falciparum. Intermittent preventive treatment of malaria in pregnancy (IPTp) with Sulfadoxine–pyrimethamine (SP) tablets is one of the current interventions to mitigate the effects of malaria on both the pregnant woman and the unborn child. The extent to which IPTp may interfere with the acquisition of protective immunity against pregnancy-associated malaria (PAM) is undefined in Ghana. Methods Three-hundred-and-twenty pregnant women were randomly enrolled at the antenatal clinic (ANC) in Madina, Accra. Venous blood samples were obtained at first ANC registration and at 4-week intervals (post-IPTp administration). Placental and cord blood samples were obtained at delivery and the infants were followed monthly for 6 months after birth. Anti-IgG and IgM antibodies against a crude antigen preparation and the glutamate-rich protein (GLURP) of P. falciparum were quantified by the enzyme-linked immunosorbent assay (ELISA). Results There was a general decline in the trend of mean concentrations of all the antibodies from enrolment to delivery. The levels of antibodies in cord blood and placenta were well correlated. Children did not show clinical signs of malaria at 6 months after birth. Conclusions IgG against both crude antigen and GLURP were present in placenta and cord blood and it is therefore concluded that there is a trend of declining antibody from enrolment to delivery and IPTp-SP may have reduced malaria exposure, however, this does not impact on the transfer of antibodies to the foetus in utero. The levels of maternal and cord blood antibodies at delivery showed no adverse implications on malaria among the children at 6 months. However, the quantum and quality of the antibody transferred needs further investigation to ensure that the infants are protected from severe episodes of malaria.
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Affiliation(s)
- Judith K Stephens
- Biological, Environmental and Occupational and Health Sciences Department, School of Public Health, College of Health Sciences, University of Ghana, P. O. Box LG 13, Legon, Accra, Ghana.
| | - Eric Kyei-Baafour
- Immunology Department Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, P. O. Box LG 581, Legon, Accra, Ghana
| | - Emmanuel K Dickson
- Immunology Department Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, P. O. Box LG 581, Legon, Accra, Ghana
| | - Jones K Ofori
- Biological, Environmental and Occupational and Health Sciences Department, School of Public Health, College of Health Sciences, University of Ghana, P. O. Box LG 13, Legon, Accra, Ghana
| | - Michael F Ofori
- Immunology Department Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, P. O. Box LG 581, Legon, Accra, Ghana
| | - Mark L Wilson
- Department of Epidemiology, School of Public Health, The University of Michigan, 109 Observatory Street, Ann Arbor, MI, 48109-2029, USA
| | - Isabella A Quakyi
- Biological, Environmental and Occupational and Health Sciences Department, School of Public Health, College of Health Sciences, University of Ghana, P. O. Box LG 13, Legon, Accra, Ghana
| | - Bartholomew D Akanmori
- Immunology Department Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, P. O. Box LG 581, Legon, Accra, Ghana.,Vaccine Research and Development, Immunization and Vaccines Development Cluster, Office of the Regional Director, WHO Regional Office for Africa, P. O. Box 06, Djoue, Brazzaville, Congo
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Bruske EI, Dimonte S, Enderes C, Tschan S, Flötenmeyer M, Koch I, Berger J, Kremsner P, Frank M. In Vitro Variant Surface Antigen Expression in Plasmodium falciparum Parasites from a Semi-Immune Individual Is Not Correlated with Var Gene Transcription. PLoS One 2016; 11:e0166135. [PMID: 27907004 PMCID: PMC5132323 DOI: 10.1371/journal.pone.0166135] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 10/24/2016] [Indexed: 12/17/2022] Open
Abstract
Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is considered to be the main variant surface antigen (VSA) of Plasmodium falciparum and is mainly localized on electron-dense knobs in the membrane of the infected erythrocyte. Switches in PfEMP1 expression provide the basis for antigenic variation and are thought to be critical for parasite persistence during chronic infections. Recently, strain transcending anti-PfEMP1 immunity has been shown to develop early in life, challenging the role of PfEMP1 in antigenic variation during chronic infections. In this work we investigate how P. falciparum achieves persistence during a chronic asymptomatic infection. The infected individual (MOA) was parasitemic for 42 days and multilocus var gene genotyping showed persistence of the same parasite population throughout the infection. Parasites from the beginning of the infection were adapted to tissue culture and cloned by limiting dilution. Flow cytometry using convalescent serum detected a variable surface recognition signal on isogenic clonal parasites. Quantitative real-time PCR with a field isolate specific var gene primer set showed that the surface recognition signal was not correlated with transcription of individual var genes. Strain transcending anti-PfEMP1 immunity of the convalescent serum was demonstrated with CD36 selected and PfEMP1 knock-down NF54 clones. In contrast, knock-down of PfEMP1 did not have an effect on the antibody recognition signal in MOA clones. Trypsinisation of the membrane surface proteins abolished the surface recognition signal and immune electron microscopy revealed that antibodies from the convalescent serum bound to membrane areas without knobs and with knobs. Together the data indicate that PfEMP1 is not the main variable surface antigen during a chronic infection and suggest a role for trypsin sensitive non-PfEMP1 VSAs for parasite persistence in chronic infections.
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Affiliation(s)
- Ellen Inga Bruske
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
| | - Sandra Dimonte
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
| | - Corinna Enderes
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
| | - Serena Tschan
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
| | | | - Iris Koch
- Max Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Jürgen Berger
- Max Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Peter Kremsner
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
- CERMEL (Centre de Recherche Médicale de Lambaréné), Lambaréné, Gabon
| | - Matthias Frank
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
- CERMEL (Centre de Recherche Médicale de Lambaréné), Lambaréné, Gabon
- * E-mail:
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Carlos BC, Fotoran WL, Menezes MJ, Cabral FJ, Bastos MF, Costa FT, Sousa-Neto JA, Ribolla PE, Wunderlich G, Ferreira MU. Expressed var gene repertoire and variant surface antigen diversity in a shrinking Plasmodium falciparum population. Exp Parasitol 2016; 170:90-99. [DOI: 10.1016/j.exppara.2016.09.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 09/01/2016] [Accepted: 09/20/2016] [Indexed: 10/21/2022]
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Relationship between Antibody Levels, IgG Binding to Plasmodium falciparum-Infected Erythrocytes, and Disease Outcome in Hospitalized Urban Malaria Patients from Dakar, Sénégal. BIOMED RESEARCH INTERNATIONAL 2016; 2016:5381956. [PMID: 27563669 PMCID: PMC4987455 DOI: 10.1155/2016/5381956] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Revised: 05/06/2016] [Accepted: 05/24/2016] [Indexed: 11/17/2022]
Abstract
Background. Management of clinical malaria requires the development of reliable diagnostic methods and efficient biomarkers for follow-up of patients. Protection is partly based on IgG responses to parasite antigens exposed at the surface of infected erythrocytes (iRBCs). These IgG responses appeared low during clinical infection, particularly in severe disease. Methods. We analyzed the IgG binding capacity to the surface of live erythrocytes infected by knob positive FCR3 strain. Sera from 69 cerebral malaria (CM) and 72 mild malaria (MM) cases were analyzed by ELISA for IgG responses to five antigens from iRBC and by flow cytometry for IgG binding as expressed in labeling index ratio (LIR). The relationship between IgG levels, LIR, parasitemia, age, and the clinical outcomes was evaluated. Results. We found a significant decrease of LIR in adult CM fatal cases compared to surviving patients (p = 0.019). In MM, LIRs were correlated to IgG anti-iRBC and anti-PfEMP3/5 levels. In CM, no correlation was found between LIR, IgG levels, and parasitemia. Conclusion. The IgG binding assay was able to discriminate outcome of cerebral malaria cases and it deserves further development as a potential functional-associated assay for symptomatic malaria analysis.
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Quintana MDP, Angeletti D, Moll K, Chen Q, Wahlgren M. Phagocytosis-inducing antibodies to Plasmodium falciparum upon immunization with a recombinant PfEMP1 NTS-DBL1α domain. Malar J 2016; 15:416. [PMID: 27531359 PMCID: PMC4987995 DOI: 10.1186/s12936-016-1459-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 07/29/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Individuals living in endemic areas gradually acquire natural immunity to clinical malaria, largely dependent on antibodies against parasite antigens. There are many studies indicating that the variant antigen PfEMP1 at the surface of the parasitized red blood cell (pRBC) is one of the major targets of the immune response. It is believed that antibodies against PfEMP1 confer protection by blocking sequestration (rosetting and cytoadherence), inducing antibody-dependent cellular-inhibitory effect and opsonizing pRBCs for phagocytosis. METHODS A recombinant NTS-DBL1α domain from a rosette-mediating PfEMP1 was expressed in Escherichia coli. The resulting protein was purified and used for immunization to generate polyclonal (goat) and monoclonal (mouse) antibodies. The antibodies' ability to opsonize and induce phagocytosis in vitro was tested and contrasted with the presence of opsonizing antibodies naturally acquired during Plasmodium falciparum infection. RESULTS All antibodies recognized the recombinant antigen and the surface of live pRBCs, however, their capacity to opsonize the pRBCs for phagocytosis varied. The monoclonal antibodies isotyped as IgG2b did not induce phagocytosis, while those isotyped as IgG2a were in general very effective, inducing phagocytosis with similar levels as those naturally acquired during P. falciparum infection. These monoclonal antibodies displayed different patterns, some of them showing a concentration-dependent activity while others showed a prozone-like effect. The goat polyclonal antibodies were not able to induce phagocytosis. CONCLUSION Immunization with an NTS-DBL1-α domain of PfEMP1 generates antibodies that not only have a biological role in rosette disruption but also effectively induce opsonization for phagocytosis of pRBCs with similar activity to naturally acquired antibodies from immune individuals living in a malaria endemic area. Some of the antibodies with high opsonizing activity were not able to disrupt rosettes, indicating that epitopes of the NTS-DBL1-α other than those involved in rosetting are exposed on the pRBC surface and are able to induce functional antibodies. The ability to induce phagocytosis largely depended on the antibody isotype and on the ability to recognize the surface of the pRBC regardless of the rosette-disrupting capacity.
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Affiliation(s)
- Maria Del Pilar Quintana
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden.,Escuela de Medicina y Ciencias de la Salud, Facultad de Ciencias Naturales y Matemáticas, Universidad del Rosario, Bogotá, Colombia
| | - Davide Angeletti
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Kirsten Moll
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Qijun Chen
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden.,Key Laboratory of Zoonosis, Jilin University, Changchun, People's Republic of China.,Institute of Pathogen Biology, Chinese Academy of Medical Sciences, Beijing, People's Republic of China
| | - Mats Wahlgren
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden.
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Kudella PW, Moll K, Wahlgren M, Wixforth A, Westerhausen C. ARAM: an automated image analysis software to determine rosetting parameters and parasitaemia in Plasmodium samples. Malar J 2016; 15:223. [PMID: 27090910 PMCID: PMC4835829 DOI: 10.1186/s12936-016-1243-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Accepted: 03/30/2016] [Indexed: 11/14/2022] Open
Abstract
Background Rosetting is associated with severe malaria and a primary cause of death in Plasmodium falciparum infections. Detailed understanding of this adhesive phenomenon may enable the development of new therapies interfering with rosette formation. For this, it is crucial to determine parameters such as rosetting and parasitaemia of laboratory strains or patient isolates, a bottleneck in malaria research due to the time consuming and error prone manual analysis of specimens. Here, the automated, free, stand-alone analysis software automated rosetting analyzer for micrographs (ARAM) to determine rosetting rate, rosette size distribution as well as parasitaemia with a convenient graphical user interface is presented. Methods Automated rosetting analyzer for micrographs is an executable with two operation modes for automated identification of objects on images. The default mode detects red blood cells and fluorescently labelled parasitized red blood cells by combining an intensity-gradient with a threshold filter. The second mode determines object location and size distribution from a single contrast method. The obtained results are compared with standardized manual analysis. Automated rosetting analyzer for micrographs calculates statistical confidence probabilities for rosetting rate and parasitaemia. Results Automated rosetting analyzer for micrographs analyses 25 cell objects per second reliably delivering identical results compared to manual analysis. For the first time rosette size distribution is determined in a precise and quantitative manner employing ARAM in combination with established inhibition tests. Additionally ARAM measures the essential observables parasitaemia, rosetting rate and size as well as location of all detected objects and provides confidence intervals for the determined observables. No other existing software solution offers this range of function. The second, non-malaria specific, analysis mode of ARAM offers the functionality to detect arbitrary objects. Conclusions Automated rosetting analyzer for micrographs has the capability to push malaria research to a more quantitative and statistically significant level with increased reliability due to operator independence. As an installation file for Windows © 7, 8.1 and 10 is available for free, ARAM offers a novel open and easy-to-use platform for the malaria community to elucidate rosetting. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1243-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | - Kirsten Moll
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Box 280, 171 77, Stockholm, Sweden
| | - Mats Wahlgren
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Box 280, 171 77, Stockholm, Sweden
| | - Achim Wixforth
- Experimental Physics I, University of Augsburg, Universitätsstraße 1, Augsburg, Germany.,Nanosystems Initiative Munich, Schellingstraße 4, Munich, Germany
| | - Christoph Westerhausen
- Experimental Physics I, University of Augsburg, Universitätsstraße 1, Augsburg, Germany. .,Nanosystems Initiative Munich, Schellingstraße 4, Munich, Germany.
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Dinko B, Pradel G. Immune evasion by <i>Plasmodium falciparum</i> parasites: converting a host protection mechanism for the parasite′s benefit. ACTA ACUST UNITED AC 2016. [DOI: 10.4236/aid.2016.62011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Kaddumukasa M, Lwanira C, Lugaajju A, Katabira E, Persson KEM, Wahlgren M, Kironde F. Parasite Specific Antibody Increase Induced by an Episode of Acute P. falciparum Uncomplicated Malaria. PLoS One 2015; 10:e0124297. [PMID: 25906165 PMCID: PMC4408068 DOI: 10.1371/journal.pone.0124297] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 03/11/2015] [Indexed: 11/30/2022] Open
Abstract
Introduction There is no approved vaccine for malaria, and precisely how human antibody responses to malaria parasite components and potential vaccine molecules are developed and maintained remains poorly defined. In this study, antibody anamnestic or memory response elicited by a single episode of P. falciparum infection was investigated. Methods This study involved 362 malaria patients aged between 6 months to 60 years, of whom 19% were early-diagnosed people living with HIV/AIDS (PLWHA). On the day malaria was diagnosed and 42 days later, blood specimens were collected. Parasite density, CD4+ cells, and antibodies specific to synthetic peptides representing antigenic regions of the P. falciparum proteins GLURP, MSP3 and HRPII were measured. Results On the day of malaria diagnosis, Immunoglobulin (IgG) antibodies against GLURP, MSP3 and HRP II peptides were present in the blood of 75%, 41% and 60% of patients, respectively. 42 days later, the majority of patients had boosted their serum IgG antibody more than 1.2 fold. The increase in level of IgG antibody against the peptides was not affected by parasite density at diagnosis. The median CD4+ cell counts of PLWHAs and HIV negative individuals were not statistically different, and median post-infection increases in anti-peptide IgG were similar in both groups of patients. Conclusion In the majority (70%) of individuals, an infection of P. falciparum elicits at least 20% increase in level of anti-parasite IgG. This boost in anti-P. falciparum IgG is not affected by parasite density on the day of malaria diagnosis, or by HIV status.
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Affiliation(s)
- Mark Kaddumukasa
- Department of Medicine, College of Health Sciences, Makerere University, Kampala, Uganda
| | | | - Allan Lugaajju
- College of Health Sciences, Makerere University, Kampala, Uganda
| | - Elly Katabira
- Department of Medicine, College of Health Sciences, Makerere University, Kampala, Uganda
| | - Kristina E M Persson
- Department of Microbiology, Tumour and Cell Biology, Karolinska Institutet, Stockholm, Sweden; Department of Laboratory Medicine, Lund University, Stockholm, Sweden
| | - Mats Wahlgren
- Department of Microbiology, Tumour and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Fred Kironde
- College of Health Sciences, Makerere University, Kampala, Uganda; Habib Medical School, IUIU, Kampala, Uganda
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Hviid L, Barfod L, Fowkes FJI. Trying to remember: immunological B cell memory to malaria. Trends Parasitol 2015; 31:89-94. [PMID: 25596801 DOI: 10.1016/j.pt.2014.12.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 12/16/2014] [Accepted: 12/17/2014] [Indexed: 11/17/2022]
Abstract
In areas with stable transmission of Plasmodium falciparum parasites, even partially-protective immunity to malaria is acquired only after years of exposure and several infections. It has long been speculated that malaria parasites are directly able to undermine the establishment and maintenance of immunological memory, and that the often transient antibody responses to this parasite are evidence of such a dysfunction. We propose that long-lived antibody responses may not always be a prerequisite for protection, and that antibody longevity varies in an exposure- and age-dependent manner.
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Affiliation(s)
- Lars Hviid
- Centre for Medical Parasitology at Institute for Medical Microbiology and Immunology, University of Copenhagen and Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark.
| | - Lea Barfod
- Centre for Medical Parasitology at Institute for Medical Microbiology and Immunology, University of Copenhagen and Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - Freya J I Fowkes
- Macfarlane Burnet Institute of Medical Research, Melbourne, Victoria, Australia; Centre for Epidemiology and Biostatistics, University of Melbourne, Australia; Department of Epidemiology and Preventive Medicine and Department of Infectious Diseases, Monash University, Melbourne, Australia
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25
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Albrecht L, Angeletti D, Moll K, Blomqvist K, Valentini D, D'Alexandri FL, Maurer M, Wahlgren M. B-cell epitopes in NTS-DBL1α of PfEMP1 recognized by human antibodies in Rosetting Plasmodium falciparum. PLoS One 2014; 9:e113248. [PMID: 25438249 PMCID: PMC4249881 DOI: 10.1371/journal.pone.0113248] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 10/21/2014] [Indexed: 11/20/2022] Open
Abstract
Plasmodium falciparum is the most lethal of the human malaria parasites. The virulence is associated with the capacity of the infected red blood cell (iRBC) to sequester inside the deep microvasculature where it may cause obstruction of the blood-flow when binding is excessive. Rosetting, the adherence of the iRBC to uninfected erythrocytes, has been found associated with severe malaria and found to be mediated by the NTS-DBL1α-domain of Plasmodium falciparum Erythrocyte Membrane Protein 1 (PfEMP1). Here we show that the reactivity of plasma of Cameroonian children with the surface of the FCR3S1.2-iRBC correlated with the capacity to disrupt rosettes and with the antibody reactivity with a recombinant PfEMP1 (NTS-DBL1α of IT4var60) expressed by parasite FCR3S1.2. The plasma-reactivity in a microarray, consisting of 96 overlapping 15-mer long peptides covering the NTS-DBL1α domain from IT4var60 sequence, was compared with their capacity to disrupt rosettes and we identified five peptides where the reactivity were correlated. Three of the peptides were localized in subdomain-1 and 2. The other two peptide-sequences were localized in the NTS-domain and in subdomain-3. Further, principal component analysis and orthogonal partial least square analysis generated a model that supported these findings. In conclusion, human antibody reactivity with short linear-peptides of NTS-DBL1α of PfEMP1 suggests subdomains 1 and 2 to hold anti-rosetting epitopes recognized by anti-rosetting antibodies. The data suggest rosetting to be mediated by the variable areas of PfEMP1 but also to involve structurally relatively conserved areas of the molecule that may induce biologically active antibodies.
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Affiliation(s)
- Letusa Albrecht
- Department of Microbiology, Tumor- and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
- * E-mail: (MW); (LA)
| | - Davide Angeletti
- Department of Microbiology, Tumor- and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Kirsten Moll
- Department of Microbiology, Tumor- and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Karin Blomqvist
- Department of Microbiology, Tumor- and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Davide Valentini
- Therapeutic Immunology (TIM), Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
- CAST, Karolinska University Hospital, Huddinge, Sweden
| | | | - Markus Maurer
- Therapeutic Immunology (TIM), Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
- CAST, Karolinska University Hospital, Huddinge, Sweden
| | - Mats Wahlgren
- Department of Microbiology, Tumor- and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
- * E-mail: (MW); (LA)
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Ampomah P, Stevenson L, Ofori MF, Barfod L, Hviid L. Kinetics of B cell responses to Plasmodium falciparum erythrocyte membrane protein 1 in Ghanaian women naturally exposed to malaria parasites. THE JOURNAL OF IMMUNOLOGY 2014; 192:5236-44. [PMID: 24760153 DOI: 10.4049/jimmunol.1400325] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Naturally acquired protective immunity to Plasmodium falciparum malaria takes years to develop. It relies mainly on Abs, particularly IgG specific for Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) proteins on the infected erythrocyte surface. It is only partially understood why acquisition of clinical protection takes years to develop, but it probably involves a range of immune-evasive parasite features, not least of which are PfEMP1 polymorphism and clonal variation. Parasite-induced subversion of immunological memory and expansion of "atypical" memory B cells may also contribute. In this first, to our knowledge, longitudinal study of its kind, we measured B cell subset composition, as well as PfEMP1-specific Ab levels and memory B cell frequencies, in Ghanaian women followed from early pregnancy up to 1 y after delivery. Cell phenotypes and Ag-specific B cell function were assessed three times during and after pregnancy. Levels of IgG specific for pregnancy-restricted, VAR2CSA-type PfEMP1 increased markedly during pregnancy and declined after delivery, whereas IgG levels specific for two PfEMP1 proteins not restricted to pregnancy did not. Changes in VAR2CSA-specific memory B cell frequencies showed typical primary memory induction among primigravidae and recall expansion among multigravidae, followed by contraction postpartum in all. No systematic changes in the frequencies of memory B cells specific for the two other PfEMP1 proteins were identified. The B cell subset analysis confirmed earlier reports of high atypical memory B cell frequencies among residents of P. falciparum-endemic areas, and indicated an additional effect of pregnancy. Our study provides new knowledge regarding immunity to P. falciparum malaria and underpins efforts to develop PfEMP1-based vaccines against this disease.
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Affiliation(s)
- Paulina Ampomah
- Centre for Medical Parasitology, University of Copenhagen and Copenhagen University Hospital (Rigshospitalet), 2100 Copenhagen Ø, Denmark; and
| | - Liz Stevenson
- Centre for Medical Parasitology, University of Copenhagen and Copenhagen University Hospital (Rigshospitalet), 2100 Copenhagen Ø, Denmark; and
| | - Michael F Ofori
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
| | - Lea Barfod
- Centre for Medical Parasitology, University of Copenhagen and Copenhagen University Hospital (Rigshospitalet), 2100 Copenhagen Ø, Denmark; and
| | - Lars Hviid
- Centre for Medical Parasitology, University of Copenhagen and Copenhagen University Hospital (Rigshospitalet), 2100 Copenhagen Ø, Denmark; and
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Chan JA, Fowkes FJI, Beeson JG. Surface antigens of Plasmodium falciparum-infected erythrocytes as immune targets and malaria vaccine candidates. Cell Mol Life Sci 2014; 71:3633-57. [PMID: 24691798 PMCID: PMC4160571 DOI: 10.1007/s00018-014-1614-3] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 03/04/2014] [Accepted: 03/17/2014] [Indexed: 12/19/2022]
Abstract
Understanding the targets and mechanisms of human immunity to malaria caused by Plasmodium falciparum is crucial for advancing effective vaccines and developing tools for measuring immunity and exposure in populations. Acquired immunity to malaria predominantly targets the blood stage of infection when merozoites of Plasmodium spp. infect erythrocytes and replicate within them. During the intra-erythrocytic development of P. falciparum, numerous parasite-derived antigens are expressed on the surface of infected erythrocytes (IEs). These antigens enable P. falciparum-IEs to adhere in the vasculature and accumulate in multiple organs, which is a key process in the pathogenesis of disease. IE surface antigens, often referred to as variant surface antigens, are important targets of acquired protective immunity and include PfEMP1, RIFIN, STEVOR and SURFIN. These antigens are highly polymorphic and encoded by multigene families, which generate substantial antigenic diversity to mediate immune evasion. The most important immune target appears to be PfEMP1, which is a major ligand for vascular adhesion and sequestration of IEs. Studies are beginning to identify specific variants of PfEMP1 linked to disease pathogenesis that may be suitable for vaccine development, but overcoming antigenic diversity in PfEMP1 remains a major challenge. Much less is known about other surface antigens, or antigens on the surface of gametocyte-IEs, the effector mechanisms that mediate immunity, and how immunity is acquired and maintained over time; these are important topics for future research.
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Nhabomba AJ, Guinovart C, Jiménez A, Manaca MN, Quintó L, Cisteró P, Aguilar R, Barbosa A, Rodríguez MH, Bassat Q, Aponte JJ, Mayor A, Chitnis CE, Alonso PL, Dobaño C. Impact of age of first exposure to Plasmodium falciparum on antibody responses to malaria in children: a randomized, controlled trial in Mozambique. Malar J 2014; 13:121. [PMID: 24674654 PMCID: PMC3986595 DOI: 10.1186/1475-2875-13-121] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 03/22/2014] [Indexed: 12/03/2022] Open
Abstract
Background The impact of the age of first Plasmodium falciparum infection on the rate of acquisition of immunity to malaria and on the immune correlates of protection has proven difficult to elucidate. A randomized, double-blind, placebo-controlled trial using monthly chemoprophylaxis with sulphadoxine-pyrimethamine plus artesunate was conducted to modify the age of first P. falciparum erythrocytic exposure in infancy and assess antibodies and malaria risk over two years. Methods Participants (n = 349) were enrolled at birth to one of three groups: late exposure, early exposure and control group, and were followed up for malaria morbidity and immunological analyses at birth, 2.5, 5.5, 10.5, 15 and 24 months of age. Total IgG, IgG subclasses and IgM responses to MSP-119, AMA-1, and EBA-175 were measured by ELISA, and IgG against variant antigens on the surface of infected erythrocytes by flow cytometry. Factors affecting antibody responses in relation to chemoprophylaxis and malaria incidence were evaluated. Results Generally, antibody responses did not vary significantly between exposure groups except for levels of IgM to EBA-175, and seropositivity of IgG1 and IgG3 to MSP-119. Previous and current malaria infections were strongly associated with increased IgG against MSP-119, EBA-175 and AMA-1 (p < 0.0001). After adjusting for exposure, only higher levels of anti-EBA-175 IgG were significantly associated with reduced clinical malaria incidence (IRR 0.67, p = 0.0178). Conclusions Overall, the age of first P. falciparum infection did not influence the magnitude and breadth of IgG responses, but previous exposure was critical for antibody acquisition. IgG responses to EBA-175 were the strongest correlate of protection against clinical malaria. Trial registration ClinicalTrials.gov: NCT00231452.
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B-cell responses to pregnancy-restricted and -unrestricted Plasmodium falciparum erythrocyte membrane protein 1 antigens in Ghanaian women naturally exposed to malaria parasites. Infect Immun 2014; 82:1860-71. [PMID: 24566620 DOI: 10.1128/iai.01514-13] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Protective immunity to Plasmodium falciparum malaria acquired after natural exposure is largely antibody mediated. IgG-specific P. falciparum EMP1 (PfEMP1) proteins on the infected erythrocyte surface are particularly important. The transient antibody responses and the slowly acquired protective immunity probably reflect the clonal antigenic variation and allelic polymorphism of PfEMP1. However, it is likely that other immune-evasive mechanisms are also involved, such as interference with formation and maintenance of immunological memory. We measured PfEMP1-specific antibody levels by enzyme-linked immunosorbent assay (ELISA) and memory B-cell frequencies by enzyme-linked immunosorbent spot (ELISPOT) assay in a cohort of P. falciparum-exposed nonpregnant Ghanaian women. The antigens used were a VAR2CSA-type PfEMP1 (IT4VAR04) with expression restricted to parasites infecting the placenta, as well as two commonly recognized PfEMP1 proteins (HB3VAR06 and IT4VAR60) implicated in rosetting and not pregnancy restricted. This enabled, for the first time, a direct comparison in the same individuals of immune responses specific for a clinically important parasite antigen expressed only during well-defined periods (pregnancy) to responses specific for comparable antigens expressed independent of pregnancy. Our data indicate that PfEMP1-specific B-cell memory is adequately acquired even when antigen exposure is infrequent (e.g., VAR2CSA-type PfEMP1). Furthermore, immunological memory specific for VAR2CSA-type PfEMP1 can be maintained for many years without antigen reexposure and after circulating antigen-specific IgG has disappeared. The study provides evidence that natural exposure to P. falciparum leads to formation of durable B-cell immunity to clinically important PfEMP1 antigens. This has encouraging implications for current efforts to develop PfEMP1-based vaccines.
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Adukpo S, Kusi KA, Ofori MF, Tetteh JKA, Amoako-Sakyi D, Goka BQ, Adjei GO, Edoh DA, Akanmori BD, Gyan BA, Dodoo D. High plasma levels of soluble intercellular adhesion molecule (ICAM)-1 are associated with cerebral malaria. PLoS One 2013; 8:e84181. [PMID: 24386348 PMCID: PMC3873986 DOI: 10.1371/journal.pone.0084181] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Accepted: 11/12/2013] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND Cerebral malaria (CM) is responsible for most of the malaria-related deaths in children in sub-Saharan Africa. Although, not well understood, the pathogenesis of CM involves parasite and host factors which contribute to parasite sequestration through cytoadherence to the vascular endothelium. Cytoadherence to brain microvasculature is believed to involve host endothelial receptor, CD54 or intercellular adhesion molecule (ICAM)-1, while other receptors such as CD36 are generally involved in cytoadherence of parasites in other organs. We therefore investigated the contributions of host ICAM-1 expression and levels of antibodies against ICAM-1 binding variant surface antigen (VSA) on parasites to the development of CM. METHODOLOGY/PRINCIPAL FINDINGS Paediatric malaria patients, 0.5 to 13 years were recruited and grouped into CM and uncomplicated malaria (UM) patients, based on well defined criteria. Standardized ELISA protocol was used to measure soluble ICAM-1 (sICAM-1) levels from acute plasma samples. Levels of IgG to CD36- or ICAM-1-binding VSA were measured by flow cytometry during acute and convalescent states. Wilcoxon sign rank-test analysis to compare groups revealed association between sICAM-1 levels and CM (p<0.0037). Median levels of antibodies to CD36-binding VSA were comparable in the two groups at the time of admission and 7 days after treatment was initiated (p>0.05). Median levels of antibodies to CD36-binding VSAs were also comparable between acute and convalescent samples within any patient group. Median levels of antibodies to ICAM-1-binding VSAs were however significantly lower at admission time than during recovery in both groups. CONCLUSIONS/SIGNIFICANCE High levels of sICAM-1 were associated with CM, and the sICAM-1 levels may reflect expression levels of the membrane bound form. Anti-VSA antibody levels to ICAM-binding parasites was more strongly associated with both UM and CM than antibodies to CD36 binding parasites. Thus, increasing host sICAM-1 levels were associated with CM whilst antibodies to parasite expressing non-ICAM-1-binding VSAs were not.
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Affiliation(s)
- Selorme Adukpo
- Immunology Department, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Accra, Ghana
- Department of Animal Biology and Conservation Science, University of Ghana, Legon, Accra, Ghana
- * E-mail:
| | - Kwadwo A. Kusi
- Immunology Department, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Accra, Ghana
| | - Michael F. Ofori
- Immunology Department, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Accra, Ghana
| | - John K. A. Tetteh
- Immunology Department, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Accra, Ghana
| | - Daniel Amoako-Sakyi
- Immunology Department, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Accra, Ghana
| | - Bamenla Q. Goka
- Department of Child Health, University of Ghana Medical School, College of Health Sciences, University of Ghana, Legon, Accra, Ghana
| | - George O. Adjei
- Department of Child Health, University of Ghana Medical School, College of Health Sciences, University of Ghana, Legon, Accra, Ghana
| | - Dominic A. Edoh
- Department of Animal Biology and Conservation Science, University of Ghana, Legon, Accra, Ghana
| | - Bartholomew D. Akanmori
- Immunology Department, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Accra, Ghana
| | - Ben A. Gyan
- Immunology Department, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Accra, Ghana
| | - Daniel Dodoo
- Immunology Department, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Accra, Ghana
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Abstract
The within-host dynamics of an infection with the malaria parasite Plasmodium falciparum are the result of a complex interplay between the host immune system and parasite. Continual variation of the P. falciparum erythrocyte membrane protein (PfEMP1) antigens displayed on the surface of infected red blood cells enables the parasite to evade the immune system and prolong infection. Despite the importance of antigenic variation in generating the dynamics of infection, our understanding of the mechanisms by which antigenic variation generates long-term chronic infections is still limited. We developed a model to examine the role of cross-reactivity in generating infection dynamics that are comparable to those of experimental infections. The hybrid computational model we developed is attuned to the biology of malaria by mixing discrete replication events, which mimics the synchrony of parasite replication and invasion, with continuous interaction with the immune system. Using simulations, we evaluated the dynamics of a single malaria infection over time. We then examined three major mechanisms by which the dynamics of a malaria infection can be structured: cross-reactivity of the immune response to PfEMP1, differences in parasite clearance rates, and heterogeneity in the rate at which antigens switch. The results of our simulations demonstrate that cross-reactive immune responses play a primary role in generating the dynamics observed in experimentally untreated infections and in lengthening the period of infection. Importantly, we also find that it is the primary response to the initially expressed PfEMP1, or small subset thereof, that structures the cascading cross-immune dynamics and allows for elongation of the infection.
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Warimwe GM, Recker M, Kiragu EW, Buckee CO, Wambua J, Musyoki JN, Marsh K, Bull PC. Plasmodium falciparum var gene expression homogeneity as a marker of the host-parasite relationship under different levels of naturally acquired immunity to malaria. PLoS One 2013; 8:e70467. [PMID: 23922996 PMCID: PMC3726600 DOI: 10.1371/journal.pone.0070467] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 06/19/2013] [Indexed: 11/19/2022] Open
Abstract
Acquired immunity to Plasmodium falciparum infection causes a change from frequent, sometimes life-threatening, malaria in young children to asymptomatic, chronic infections in older children and adults. Little is known about how this transition occurs but antibodies to the extremely diverse PfEMP1 parasite antigens are thought to play a role. PfEMP1 is encoded by a family of 60 var genes that undergo clonal antigenic variation, potentially creating an antigenically heterogeneous infecting population of parasites within the host. Previous theoretical work suggests that antibodies to PfEMP1 may play a role in "orchestrating" their expression within infections leading to sequential, homogeneous expression of var genes, and prolonged infection chronicity. Here, using a cloning and sequencing approach we compare the var expression homogeneity (VEH) between isolates from children with asymptomatic and clinical infections. We show that asymptomatic infections have higher VEH than clinical infections and a broader host antibody response. We discuss this in relation to the potential role of host antibodies in promoting chronicity of infection and parasite survival through the low transmission season.
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Affiliation(s)
- George M. Warimwe
- Pathogen, Vector and Human Biology Department, Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Mario Recker
- Department of Zoology, University of Oxford, Oxford, United Kingdom
| | - Esther W. Kiragu
- Pathogen, Vector and Human Biology Department, Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Caroline O. Buckee
- Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, United States of America
| | - Juliana Wambua
- Pathogen, Vector and Human Biology Department, Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Jennifer N. Musyoki
- Pathogen, Vector and Human Biology Department, Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Kevin Marsh
- Pathogen, Vector and Human Biology Department, Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
- Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom
| | - Peter C. Bull
- Pathogen, Vector and Human Biology Department, Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
- Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom
- * E-mail:
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Portugal S, Pierce SK, Crompton PD. Young lives lost as B cells falter: what we are learning about antibody responses in malaria. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2013; 190:3039-46. [PMID: 23526829 PMCID: PMC3608210 DOI: 10.4049/jimmunol.1203067] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Plasmodium falciparum malaria remains a major public health threat for which there is no licensed vaccine. Abs play a key role in malaria immunity, but Ab-mediated protection is only acquired after years of repeated infections, leaving children in endemic areas vulnerable to severe malaria and death. Many P. falciparum Ags are extraordinarily diverse and clonally variant, which likely contribute to the inefficient acquisition of protective Abs. However, mounting evidence suggests that there is more to the story and that infection-induced dysregulation of B cell function also plays a role. We herein review progress toward understanding the B cell biology of P. falciparum infection, focusing on what has been learned from population-based studies in malaria-endemic areas. We suggest ways in which advances in immunology and genomics-based technology can further improve our understanding of the B cell response in malaria and perhaps illuminate new pathways to the development of effective vaccines.
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Affiliation(s)
- Silvia Portugal
- Laboratory of Immunogenetics, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA
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Tartz S, Deschermeier C, Retzlaff S, Heussler V, Sebo P, Fleischer B, Jacobs T. Plasmodium berghei sporozoite challenge of vaccinated BALB/c mice leads to the induction of humoral immunity and improved function of CD8(+) memory T cells. Eur J Immunol 2013; 43:693-704. [PMID: 23229763 DOI: 10.1002/eji.201142262] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Revised: 11/29/2012] [Accepted: 12/05/2012] [Indexed: 11/06/2022]
Abstract
Protection against malaria can be achieved by induction of a strong CD8(+) T-cell response against the Plasmodium circumsporozoite protein (CSP), but most subunit vaccines suffer from insufficient memory responses. In the present study, we analyzed the impact of postimmunization sporozoite challenge on the development of long-lasting immunity. BALB/c mice were immunized by a heterologous prime/boost regimen against Plasmodium berghei CSP that induces a strong CD8(+) T-cell response and sterile protection, which is short-lived. Here, we show that protective immunity is prolonged by a sporozoite challenge after immunization. Repeated challenges induced sporozoite-specific antibodies that showed protective capacity. The numbers of CSP-specific CD8(+) T cells were not substantially enhanced by sporozoite infections; however, CSP-specific memory CD8(+) T cells of challenged mice displayed a higher cytotoxic activity than memory T cells of immunized-only mice. CD4(+) T cells contributed to protection as well; but CD8(+) memory T cells were found to be the central mediator of sterile protection. Based on these data, we suggest that prolonged protective immunity observed after immunization and infection is composed of different antiparasitic mechanisms including CD8(+) effector-memory T cells with increased cytotoxic activity as well as CD4(+) memory T cells and neutralizing antibodies.
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Affiliation(s)
- Susanne Tartz
- Department of Immunology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
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Blomqvist K, Albrecht L, Quintana MDP, Angeletti D, Joannin N, Chêne A, Moll K, Wahlgren M. A sequence in subdomain 2 of DBL1α of Plasmodium falciparum erythrocyte membrane protein 1 induces strain transcending antibodies. PLoS One 2013; 8:e52679. [PMID: 23335956 PMCID: PMC3546040 DOI: 10.1371/journal.pone.0052679] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2012] [Accepted: 11/19/2012] [Indexed: 11/18/2022] Open
Abstract
Immunity to severe malaria is the first level of immunity acquired to Plasmodium falciparum. Antibodies to the variant antigen PfEMP1 (P. falciparum erythrocyte membrane protein 1) present at the surface of the parasitized red blood cell (pRBC) confer protection by blocking microvascular sequestration. Here we have generated antibodies to peptide sequences of subdomain 2 of PfEMP1-DBL1α previously identified to be associated with severe or mild malaria. A set of sera generated to the amino acid sequence KLQTLTLHQVREYWWALNRKEVWKA, containing the motif ALNRKE, stained the live pRBC. 50% of parasites tested (7/14) were positive both in flow cytometry and immunofluorescence assays with live pRBCs including both laboratory strains and in vitro adapted clinical isolates. Antibodies that reacted selectively with the sequence REYWWALNRKEVWKA in a 15-mer peptide array of DBL1α-domains were also found to react with the pRBC surface. By utilizing a peptide array to map the binding properties of the elicited anti-DBL1α antibodies, the amino acids WxxNRx were found essential for antibody binding. Complementary experiments using 135 degenerate RDSM peptide sequences obtained from 93 Ugandan patient-isolates showed that antibody binding occurred when the amino acids WxLNRKE/D were present in the peptide. The data suggests that the ALNRKE sequence motif, associated with severe malaria, induces strain-transcending antibodies that react with the pRBC surface.
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Affiliation(s)
- Karin Blomqvist
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Letusa Albrecht
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Maria del Pilar Quintana
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
- Escuela de Medicina y Ciencias de la Salud, Facultad de Ciencias Naturales y Matemáticas, Universidad del Rosario, Bogotá, Colombia
| | - Davide Angeletti
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Nicolas Joannin
- Bioinformatics Center, Institute for Chemical Research, Kyoto University, Kyoto, Japan
| | - Arnaud Chêne
- Biologie des interactions Hôte-Parasite, Institut Pasteur, Paris, France
| | - Kirsten Moll
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Mats Wahlgren
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
- * E-mail:
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Doritchamou J, Bertin G, Moussiliou A, Bigey P, Viwami F, Ezinmegnon S, Fievet N, Massougbodji A, Deloron P, Tuikue Ndam N. First-trimester Plasmodium falciparum infections display a typical "placental" phenotype. J Infect Dis 2012; 206:1911-9. [PMID: 23045626 DOI: 10.1093/infdis/jis629] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Plasmodium falciparum-infected erythrocytes (IEs) adhere to host cell receptors, allowing parasites to sequester into deep vascular beds of various organs. This defining phenomenon of malaria pathogenesis is key to the severe clinical complications associated with cerebral and placental malaria. The principal ligand associated with the binding to chondroitin sulfate A (CSA) that allows placental sequestration of IEs is a P. falciparum erythrocyte membrane protein 1 (PfEMP1) family member encoded by the var2csa gene. METHODS Here, we investigated the transcription pattern of var genes by real-time polymerase chain reaction, the expression of VAR2CSA, protein by flow cytometry, and the CSA-binding ability of IEs collected at different stages of pregnancy using a static-based Petri dish assay. RESULTS Through comparison with the profiles of isolates from nonpregnant hosts, we report several lines of evidence showing that parasites infecting women during pregnancy preferentially express VAR2CSA protein, and that selection for the capacity to adhere to CSA via VAR2CSA expression occurs early in pregnancy. CONCLUSIONS Our data suggest that the placental tropism of P. falciparum is already established in the first trimester of pregnancy, with consequent implications for the development of the pathology associated with placental malaria.
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Affiliation(s)
- Justin Doritchamou
- PRES Sorbonne Paris Cité, Faculté de Pharmacie, Université Paris Descartes, Paris, France
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Eckhoff P. P. falciparum infection durations and infectiousness are shaped by antigenic variation and innate and adaptive host immunity in a mathematical model. PLoS One 2012; 7:e44950. [PMID: 23028698 PMCID: PMC3446976 DOI: 10.1371/journal.pone.0044950] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Accepted: 08/14/2012] [Indexed: 11/29/2022] Open
Abstract
Many questions remain about P. falciparum within-host dynamics, immunity, and transmission–issues that may affect public health campaign planning. These gaps in knowledge concern the distribution of durations of malaria infections, determination of peak parasitemia during acute infection, the relationships among gametocytes and immune responses and infectiousness to mosquitoes, and the effect of antigenic structure on reinfection outcomes. The present model of intra-host dynamics of P. falciparum implements detailed representations of parasite and immune dynamics, with structures based on minimal extrapolations from first-principles biology in its foundations. The model is designed to quickly and readily accommodate gains in mechanistic understanding and to evaluate effects of alternative biological hypothesis through in silico experiments. Simulations follow the parasite from the liver-stage through the detailed asexual cycle to clearance while tracking gametocyte populations. The modeled immune system includes innate inflammatory and specific antibody responses to a repertoire of antigens. The mechanistic focus provides clear explanations for the structure of the distribution of infection durations through the interaction of antigenic variation and innate and adaptive immunity. Infectiousness to mosquitoes appears to be determined not only by the density of gametocytes but also by the level of inflammatory cytokines, which harmonizes an extensive series of study results. Finally, pre-existing immunity can either decrease or increase the duration of infections upon reinfection, depending on the degree of overlap in antigenic repertoires and the strength of the pre-existing immunity.
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Affiliation(s)
- Philip Eckhoff
- Intellectual Ventures, Bellevue, Washington, United States of America.
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Milner DA, Vareta J, Valim C, Montgomery J, Daniels RF, Volkman SK, Neafsey DE, Park DJ, Schaffner SF, Mahesh NC, Barnes KG, Rosen DM, Lukens AK, Van-Tyne D, Wiegand RC, Sabeti PC, Seydel KB, Glover SJ, Kamiza S, Molyneux ME, Taylor TE, Wirth DF. Human cerebral malaria and Plasmodium falciparum genotypes in Malawi. Malar J 2012; 11:35. [PMID: 22314206 PMCID: PMC3295736 DOI: 10.1186/1475-2875-11-35] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Accepted: 02/07/2012] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Cerebral malaria, a severe form of Plasmodium falciparum infection, is an important cause of mortality in sub-Saharan African children. A Taqman 24 Single Nucleotide Polymorphisms (SNP) molecular barcode assay was developed for use in laboratory parasites which estimates genotype number and identifies the predominant genotype. METHODS The 24 SNP assay was used to determine predominant genotypes in blood and tissues from autopsy and clinical patients with cerebral malaria. RESULTS Single genotypes were shared between the peripheral blood, the brain, and other tissues of cerebral malaria patients, while malaria-infected patients who died of non-malarial causes had mixed genetic signatures in tissues examined. Children with retinopathy-positive cerebral malaria had significantly less complex infections than those without retinopathy (OR = 3.7, 95% CI [1.51-9.10]).The complexity of infections significantly decreased over the malaria season in retinopathy-positive patients compared to retinopathy-negative patients. CONCLUSIONS Cerebral malaria patients harbour a single or small set of predominant parasites; patients with incidental parasitaemia sustain infections involving diverse genotypes. Limited diversity in the peripheral blood of cerebral malaria patients and correlation with tissues supports peripheral blood samples as appropriate for genome-wide association studies of parasite determinants of pathogenicity.
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Affiliation(s)
- Danny A Milner
- Department of Pathology, Brigham and Women's Hospital, 75 Francis Street, Amory 3, Boston, MA 02115, USA
- The Blantyre Malaria Project, University of Malawi College of Medicine, Blantyre, Malawi
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
| | - Jimmy Vareta
- The Blantyre Malaria Project, University of Malawi College of Medicine, Blantyre, Malawi
| | - Clarissa Valim
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
| | - Jacqui Montgomery
- College of Medicine, Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
- Liverpool School of Tropical Medicine, University of Liverpool, Liverpool, UK
| | - Rachel F Daniels
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
- Broad Institute, Cambridge, MA 02142, USA
| | - Sarah K Volkman
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
- Department of Nursing, School for Health Sciences, Simmons College, Boston, MA 02115, USA
| | | | | | | | - Nira C Mahesh
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
| | - Kayla G Barnes
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
| | - David M Rosen
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
| | - Amanda K Lukens
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
| | - Daria Van-Tyne
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
| | | | - Pardis C Sabeti
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
- Broad Institute, Cambridge, MA 02142, USA
- Center for Systems Biology, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Karl B Seydel
- The Blantyre Malaria Project, University of Malawi College of Medicine, Blantyre, Malawi
- College of Osteopathic Medicine, Michigan State University, East Lansing, MI 48824, USA
| | - Simon J Glover
- College of Medicine, University of Malawi, Blantyre, Malawi
| | - Steve Kamiza
- College of Medicine, University of Malawi, Blantyre, Malawi
| | - Malcolm E Molyneux
- College of Medicine, Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
- Liverpool School of Tropical Medicine, University of Liverpool, Liverpool, UK
- College of Medicine, University of Malawi, Blantyre, Malawi
| | - Terrie E Taylor
- The Blantyre Malaria Project, University of Malawi College of Medicine, Blantyre, Malawi
- College of Osteopathic Medicine, Michigan State University, East Lansing, MI 48824, USA
| | - Dyann F Wirth
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
- Broad Institute, Cambridge, MA 02142, USA
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Koram KA. Antibodies to Plasmodium falciparum antigens and the risk of clinical malaria in endemic populations. Expert Rev Anti Infect Ther 2011; 9:987-91. [PMID: 22029518 DOI: 10.1586/eri.11.128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
As the research for the development of a malaria vaccine becomes increasingly important, a thorough understanding of the protection afforded by antibodies against parasite antigens is essential. The factors affecting the protective ability of antibodies elicited by highly immunogenic malaria parasite antigens and their interaction have been investigated in a study of Ugandan children by Greenhouse and colleagues. Their interesting finding of the effect of prior exposure on the protection provided against symptomatic malaria and the importance of the results in the immuno-epidemiological studies are discussed in this article.
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Affiliation(s)
- Kwadwo A Koram
- Department of Epidemiology, Noguchi Memorial Institute for Medical Research, University of Ghana, PO Box LG581, Legon, Ghana.
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Kwansa-Bentum B, Ayi I, Suzuki T, Otchere J, Kumagai T, Anyan WK, Osei JHN, Asahi H, Ofori MF, Akao N, Wilson MD, Boakye DA, Ohta N. Plasmodium falciparum isolates from southern Ghana exhibit polymorphisms in the SERCA-type PfATPase6 though sensitive to artesunate in vitro. Malar J 2011; 10:187. [PMID: 21745377 PMCID: PMC3146903 DOI: 10.1186/1475-2875-10-187] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Accepted: 07/11/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In 2005, Ghana replaced chloroquine with artemisinin-based combination therapy as the first-line treatment for uncomplicated malaria. The aim of this work was to determine for the first time, polymorphisms in the putative pfATPase6 and pftctp, pfmdr1, pfcrt genes in Ghanaian isolates, particularly at a time when there is no report on artemisinin resistance in malaria parasites from Ghana. The sensitivity of parasite isolates to anti-malaria drugs were also evaluated for a possible association with polymorphisms in these genes. METHODS The prevalence of point mutations in the above Plasmodium falciparum genes were assessed from filter-paper blood blot samples by DNA sequencing. In vitro drug sensitivity test was carried out on some of the blood samples from volunteers visiting hospitals/clinics in southern Ghana using a modified version of the standard WHO Mark III micro-test. RESULTS All successfully tested parasite isolates were sensitive to artesunate; while 19.4%, 29.0% and 51.6% were resistant to quinine, amodiaquine and chloroquine respectively. The geometric mean of IC50 value for artesunate was 0.73 nM (95% CI, 0.38-1.08), amodiaquine 30.69 nM (95% CI, 14.18-47.20) and chloroquine 58.73 nM (95% CI, 38.08-79.38). Twenty point mutations were observed in pfATPase6 gene, with no L263E and S769N. All mutations found were low in frequency, except D639G which was observed in about half of the isolates but was not associated with artesunate response (p = 0.42). The pftctp gene is highly conserved as no mutation was observed, while CVIET which is chloroquine-resistant genotype at codon 72-76 of the pfcrt gene was identified in about half of the isolates; this was consistent with chloroquine IC50 values (p = 0.001). Mutations were present in pfmdr1 gene but were not associated with artemisinin response (p = 1.00). CONCLUSION The pfATPase6 gene is highly polymorphic with D639G appearing to be fixed in Ghanaian isolates. These may just be spontaneous mutations as all parasite isolates that were tested displayed satisfactory in vitro response to artesunate. However, there is no improvement in susceptibility of the parasites to chloroquine five years after its proscription.
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Affiliation(s)
- Bethel Kwansa-Bentum
- Section of Environmental Parasitology, Department of International Health Development, Tokyo Medical and Dental University, 5-45 Yushima 1-chome, Bunkyo-ku, Tokyo, Japan.
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Severins M, Klinkenberg D, Heesterbeek H. How selection forces dictate the variant surface antigens used by malaria parasites. J R Soc Interface 2011; 9:246-60. [PMID: 21733875 DOI: 10.1098/rsif.2011.0239] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Red blood cells infected by the malaria parasite Plasmodium falciparum express variant surface antigens (VSAs) that evade host immunity and allow the parasites to persist in the human population. There exist many different VSAs and the differential expression of these VSAs is associated with the virulence (damage to the host) of the parasites. The aim of this study is to unravel the differences in the effect key selection forces have on parasites expressing different VSAs such that we can better understand how VSAs enable the parasites to adapt to changes in their environment (like control measures) and how this may impact the virulence of the circulating parasites. To this end, we have built an individual-based model that captures the main selective forces on malaria parasites, namely parasite competition, host immunity, host death and mosquito abundance at both the within- and between-host levels. VSAs are defined by the net growth rates they infer to the parasites and the model keeps track of the expression of, and antibody build-up against, each VSA in all hosts. Our results show an ordered acquisition of VSA-specific antibodies with host age, which causes a dichotomy between the more virulent VSAs that reach high parasitaemias but are restricted to young relatively non-immune hosts, and less virulent VSAs that do not reach such high parasitaemias but can infect a wider range of hosts. The outcome of a change in the parasite's environment in terms of parasite virulence depends on the exact balance between the selection forces, which sets the limiting factor for parasite survival. Parasites will evolve towards expressing more virulent VSAs when the limiting factor for parasite survival is the within-host parasite growth and the parasites are able to minimize this limitation by expressing more virulent VSAs.
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Affiliation(s)
- Maite Severins
- Theoretical Epidemiology, University of Utrecht, Yalelaan 7, 3584 CL Utrecht, The Netherlands.
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Quelhas D, Jiménez A, Quintó L, Serra-Casas E, Mayor A, Cisteró P, Puyol L, Wilson DW, Richards JS, Nhampossa T, Macete E, Aide P, Mandomando I, Sanz S, Aponte JJ, Alonso PL, Beeson JG, Menéndez C, Dobaño C. IgG against Plasmodium falciparum variant surface antigens and growth inhibitory antibodies in Mozambican children receiving intermittent preventive treatment with sulfadoxine-pyrimethamine. Immunobiology 2011; 216:793-802. [DOI: 10.1016/j.imbio.2010.12.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Revised: 12/17/2010] [Accepted: 12/19/2010] [Indexed: 10/18/2022]
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Dodoo D, Atuguba F, Bosomprah S, Ansah NA, Ansah P, Lamptey H, Egyir B, Oduro AR, Gyan B, Hodgson A, Koram KA. Antibody levels to multiple malaria vaccine candidate antigens in relation to clinical malaria episodes in children in the Kasena-Nankana district of Northern Ghana. Malar J 2011; 10:108. [PMID: 21529376 PMCID: PMC3101166 DOI: 10.1186/1475-2875-10-108] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Accepted: 05/01/2011] [Indexed: 11/20/2022] Open
Abstract
Background Considering the natural history of malaria of continued susceptibility to infection and episodes of illness that decline in frequency and severity over time, studies which attempt to relate immune response to protection must be longitudinal and have clearly specified definitions of immune status. Putative vaccines are expected to protect against infection, mild or severe disease or reduce transmission, but so far it has not been easy to clearly establish what constitutes protective immunity or how this develops naturally, especially among the affected target groups. The present study was done in under six year old children to identify malaria antigens which induce antibodies that correlate with protection from Plasmodium falciparum malaria. Methods In this longitudinal study, the multiplex assay was used to measure IgG antibody levels to 10 malaria antigens (GLURP R0, GLURP R2, MSP3 FVO, AMA1 FVO, AMA1 LR32, AMA1 3D7, MSP1 3D7, MSP1 FVO, LSA-1and EBA175RII) in 325 children aged 1 to 6 years in the Kassena Nankana district of northern Ghana. The antigen specific antibody levels were then related to the risk of clinical malaria over the ensuing year using a negative binomial regression model. Results IgG levels generally increased with age. The risk of clinical malaria decreased with increasing antibody levels. Except for FMPOII-LSA, (p = 0.05), higher IgG levels were associated with reduced risk of clinical malaria (defined as axillary temperature ≥37.5°C and parasitaemia of ≥5000 parasites/ul blood) in a univariate analysis, upon correcting for the confounding effect of age. However, in a combined multiple regression analysis, only IgG levels to MSP1-3D7 (Incidence rate ratio = 0.84, [95% C.I.= 0.73, 0.97, P = 0.02]) and AMA1 3D7 (IRR = 0.84 [95% C.I.= 0.74, 0.96, P = 0.01]) were associated with a reduced risk of clinical malaria over one year of morbidity surveillance. Conclusion The data from this study support the view that a multivalent vaccine involving different antigens is most likely to be more effective than a monovalent one. Functional assays, like the parasite growth inhibition assay will be necessary to confirm if these associations reflect functional roles of antibodies to MSP1-3D7 and AMA1-3D7 in this population.
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Affiliation(s)
- Daniel Dodoo
- Department of Immunology, Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana.
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var gene transcription and PfEMP1 expression in the rosetting and cytoadhesive Plasmodium falciparum clone FCR3S1.2. Malar J 2011; 10:17. [PMID: 21266056 PMCID: PMC3036667 DOI: 10.1186/1475-2875-10-17] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Accepted: 01/25/2011] [Indexed: 11/10/2022] Open
Abstract
Background The pathogenicity of Plasmodium falciparum is in part due to the ability of the parasitized red blood cell (pRBC) to adhere to intra-vascular host cell receptors and serum-proteins. Binding of the pRBC is mediated by Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1), a large multi-variant molecule encoded by a family of ≈60 var genes. Methods The study of var gene transcription in the parasite clone FCR3S1.2 was performed by semi-quantitative PCR and quantitative PCR (qPCR). The expression of the major PfEMP1 in FCR3S1.2 pRBC was analysed with polyclonal sera in rosette disruption assays and immunofluorecence. Results Transcripts from var1 (FCR3S1.2var1; IT4var21) and other var genes were detected by semi-quantitative PCR but results from qPCR showed that one var gene transcript dominated over the others (FCR3S1.2var2; IT4var60). Antibodies raised in rats to the recombinant NTS-DBL1α of var2 produced in E. coli completely and dose-dependently disrupted rosettes (≈95% at a dilution of 1/5). The sera reacted with the Maurer's clefts in trophozoite stages (IFA) and to the infected erythrocyte surface (FACS) indicating that FCR3S1.2var2 encodes the dominant PfEMP1 expressed in this parasite. Conclusion The major transcript in the rosetting model parasite FCR3S1.2 is FCR3S1.2var2 (IT4var60). The results suggest that this gene encodes the PfEMP1-species responsible for the rosetting phenotype of this parasite. The activity of previously raised antibodies to the NTS-DBL1α of FCR3S1.2var1 is likely due to cross-reactivity with NTS-DBL1α of the var2 encoded PfEMP1.
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Kheliouen N, Viwami F, Lalya F, Tuikue-Ndam N, Moukoko ECE, Rogier C, Deloron P, Aubouy A. Plasmodium falciparum parasites causing cerebral malaria share variant surface antigens, but are they specific? Malar J 2010; 9:220. [PMID: 20663188 PMCID: PMC2921079 DOI: 10.1186/1475-2875-9-220] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Accepted: 07/27/2010] [Indexed: 11/29/2022] Open
Abstract
Background Variant surface antigens (VSA) expressed on the surface of Plasmodium falciparum-infected red blood cells constitute a key for parasite sequestration and immune evasion. In distinct malaria pathologies, such as placental malaria, specific antibody response against VSA provides protection. This study investigated the antibody response specifically directed against VSA expressed by parasites isolated from individuals presenting a given type of clinical presentation. Methods Plasma and isolates were obtained from four groups of Beninese subjects: healthy adults, patients presenting uncomplicated malaria (UM), cerebral malaria (CM), or pregnancy-associated malaria (PAM). The reactivity of plasma samples from each clinical group was measured by flow cytometry against parasites isolated from individuals from each clinical group. Results Antibody responses against VSAUM were predominant in CM, UM and HA plasmas. When analysed according to age in all plasma groups, anti-VSACM and -VSAUM antibody levels were similar until six years of age. In older groups (6-18 and >19 years of age), VSAUM antibody levels were higher than VSACM antibody levels (P = .01, P = .0008, respectively). Mean MFI values, measured in all plasmas groups except the PAM plasmas, remained low for anti-VSAPAM antibodies and did not vary with age. One month after infection the level of anti-VSA antibodies able to recognize heterologous VSACM variants was increased in CM patients. In UM patients, antibody levels directed against heterologous VSAUM were similar, both during the infection and one month later. Conclusions In conclusion, this study suggests the existence of serologically distinct VSACM and VSAUM. CM isolates were shown to share common epitopes. Specific antibody response to VSAUM was predominant, suggesting a relative low diversity of VSAUM in the study area.
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Affiliation(s)
- Nabila Kheliouen
- Institut de Recherche pour le Développement (IRD) UMR216, Mother and Child faced with tropical infections Unit, Paris, 75006, France
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Akpogheneta OJ, Dunyo S, Pinder M, Conway DJ. Boosting antibody responses to Plasmodium falciparum merozoite antigens in children with highly seasonal exposure to infection. Parasite Immunol 2010; 32:296-304. [PMID: 20398230 PMCID: PMC2848980 DOI: 10.1111/j.1365-3024.2009.01193.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Longitudinal cohort studies are important to describe the dynamics of naturally acquired antibody response profiles to defined Plasmodium falciparum malaria antigens relative to clinical malaria episodes. In children under 7 years of age in The Gambia, serum IgG responses were measured to P. falciparum merozoite antigens AMA1, EBA175, MSP1(19), MSP2 and crude schizont extract, over a 10-month period. Persistence of antibody responses was measured in 152 children during the dry season when there was virtually no malaria transmission, and 103 children were monitored for new episodes of clinical malaria during the subsequent wet season when transmission occurred. Children who experienced clinical malaria had lower antibody levels at the start of the study than those who remained free from malaria. Associations between dry season antibody persistence and subsequent wet season antibody levels suggested robust immunological memory responses. Mean antibody levels to all antigens were elevated by the end of the wet season in children who experienced clinical malaria; each of these children had a boosted antibody response to at least one antigen. In all children, antibody avidities were lower against MSP2 than other antigens, a difference that did not change throughout the study period or in relation to clinical malaria episodes.
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Immune selection and within-host competition can structure the repertoire of variant surface antigens in Plasmodium falciparum--a mathematical model. PLoS One 2010; 5:e9778. [PMID: 20339540 PMCID: PMC2842302 DOI: 10.1371/journal.pone.0009778] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Accepted: 02/19/2010] [Indexed: 11/19/2022] Open
Abstract
Background The evolutionary mechanisms structuring the expression pattern of variant surface antigen (VSA) families that allow pathogens to evade immune responses and establish chronic and repeated infections pose major challenges to theoretical research. In Plasmodium falciparum, the best-studied VSA family is erythrocyte membrane protein 1 (PfEMP1). Each parasite genome encodes about 60 PfEMP1 variants, which are important virulence factors and major targets of host antibody responses. Transcriptional switching is the basis of clonal PfEMP1 variation and immune evasion. A relatively conserved subset of PfEMP1 variants tends to dominate in non-immune patients and in patients with severe malaria, while more diverse subsets relate to uncomplicated infection and higher levels of pre-existing protective immunity. Methodology/Principal Findings Here, we use the available molecular and serological evidence regarding VSAs, in particular PfEMP1, to formulate a mathematical model of the evolutionary mechanisms shaping VSA organization and expression patterns. The model integrates the transmission dynamics between hosts and the competitive interactions within hosts, based on the hypothesis that the VSAs can be organized into so-called dominance blocks, which characterize their competitive potential. The model reproduces immunological trends observed in field data, and predicts an evolutionary stable balance between inter-clonally conserved dominance blocks that are highly competitive within-host and diverse blocks that are favoured by immune selection at the population level. Conclusions/Significance The application of a monotonic dominance profile to VSAs encoded by a gene family generates two opposing selective forces and, consequently, two distinct clusters of genes emerge in adaptation to naïve and partially immune hosts, respectively.
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Van Geertruyden JP, Van Eijk E, Yosaatmadja F, Kasongo W, Mulenga M, D'Alessandro U, Rogerson S. The relationship of Plasmodium falciparum humeral immunity with HIV-1 immunosuppression and treatment efficacy in Zambia. Malar J 2009; 8:258. [PMID: 19922664 PMCID: PMC2784793 DOI: 10.1186/1475-2875-8-258] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Accepted: 11/18/2009] [Indexed: 11/19/2022] Open
Abstract
Background HIV-1 infection affects malaria humeral immunity during pregnancy, but data for non-pregnant adults are lacking. This study reports the impact of HIV-1 infection and other variables on the level of malaria humeral immunity in adults with clinical malaria and whether humeral immune suppression was a risk factor for treatment failure. Methods Sera of 224 HIV-1 infected and 115 uninfected adults were compared for IgG to merozoite antigens AMA-1 and MSP2 (3D7 and FC27 types) determined by ELISA, and for IgG to the Variant Surface Antigens (VSA) of three different parasite line E8B, A4 and HCD6 determined by flow cytometry. Results Compared to HIV-1 uninfected adults, AMA-1 IgG was lower in HIV-1 infected (P = 0.02) and associated with low CD4 count AMA-1 IgG (P = 0.003). Low IgG to all three merozoite antigens was associated with less anemia (P = 0.03). High parasite load was associated with low MSP2 IgG 3D7 and FC27 types (P = 0.02 and P = 0.08). Antibody levels to VSA did not differ between HIV-1 infected and uninfected adults. However, low VSA IgGs were associated with high parasite load (P ≤ 0.002 for each parasite line) and with treatment failure (P ≤ 0.04 for each parasite line). Conclusion HIV-1 affects humeral responses to AMA-1, but seems to marginally or not affect humeral responses to other merozoite antigens and VSAs. The latter were important for controlling parasite density and predict treatment outcome.
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Wellems TE, Hayton K, Fairhurst RM. The impact of malaria parasitism: from corpuscles to communities. J Clin Invest 2009; 119:2496-505. [PMID: 19729847 DOI: 10.1172/jci38307] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Malaria continues to exert a tremendous health burden on human populations, reflecting astonishingly successful adaptations of the causative Plasmodium parasites. We discuss here how this burden has driven the natural selection of numerous polymorphisms in the genes encoding hemoglobin and other erythrocyte proteins and some effectors of immunity. Plasmodium falciparum, the most deadly parasite species in humans, displays a vigorous system of antigen variation to counter host defenses and families of functionally redundant ligands to invade human cells. Advances in genetics and genomics are providing fresh insights into the nature of these evolutionary adaptations, processes of parasite transmission and infection, and the difficult challenges of malaria control.
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Affiliation(s)
- Thomas E Wellems
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland 20892-8132, USA.
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Abstract
Naturally acquired immunity to falciparum malaria protects millions of people routinely exposed to Plasmodium falciparum infection from severe disease and death. There is no clear concept about how this protection works. There is no general agreement about the rate of onset of acquired immunity or what constitutes the key determinants of protection; much less is there a consensus regarding the mechanism(s) of protection. This review summarizes what is understood about naturally acquired and experimentally induced immunity against malaria with the help of evolving insights provided by biotechnology and places these insights in the context of historical, clinical, and epidemiological observations. We advocate that naturally acquired immunity should be appreciated as being virtually 100% effective against severe disease and death among heavily exposed adults. Even the immunity that occurs in exposed infants may exceed 90% effectiveness. The induction of an adult-like immune status among high-risk infants in sub-Saharan Africa would greatly diminish disease and death caused by P. falciparum. The mechanism of naturally acquired immunity that occurs among adults living in areas of hyper- to holoendemicity should be understood with a view toward duplicating such protection in infants and young children in areas of endemicity.
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Affiliation(s)
- Denise L Doolan
- Queensland Institute of Medical Research, The Bancroft Centre, Post Office Royal Brisbane Hospital, Brisbane, Queensland 4029, Australia.
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