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de Jong GM, Yap XZ, Walk J, Dik WA, McCall MBB, van Genderen PJJ, van Hellemond JJ, Verbon A, Sauerwein RW. Baseline TGF-β correlates with protection after immunization with Plasmodium falciparum sporozoites in the Controlled Human Malaria Infection model. Immunol Lett 2023; 258:20-23. [PMID: 37075916 DOI: 10.1016/j.imlet.2023.04.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 03/31/2023] [Accepted: 04/15/2023] [Indexed: 04/21/2023]
Abstract
BACKGROUND Here we assessed a possible relationship between baseline TGF-β concentrations and acquisition of sterile immunity after Plasmodium falciparum sporozoite immunization. METHODS TGF-β concentrations were determined in samples of 65 malaria-naive volunteers in 4 studies either prior to and after challenge infection, or prior to and after first immunizing infection under chemoprophylaxis with P. falciparum sporozoites. RESULTS High baseline TGF-β concentrations were associated with rapid acquisition of sterile protection (p=0.028). CONCLUSION Baseline TGF-β concentrations predict the efficiency of acquisition of sterile immunity following sporozoite immunisation and may represent a steady-state regulatory mechanism to keep in check immune systems with a low threshold for activation.
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Affiliation(s)
- G M de Jong
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, 6500HB, The Netherlands
| | - X Z Yap
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, 6500HB, The Netherlands
| | - J Walk
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, 6500HB, The Netherlands
| | - W A Dik
- Department of Immunology, Laboratory Medical Immunology, Erasmus MC University Medical Center, Rotterdam, 3015GD, the Netherlands
| | - M B B McCall
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, 6500HB, The Netherlands
| | - P J J van Genderen
- Department of Medical Microbiology & Infectious Diseases, Erasmus MC University Medical Center, Rotterdam, 3015 GD, The Netherlands
| | - J J van Hellemond
- Department of Medical Microbiology & Infectious Diseases, Erasmus MC University Medical Center, Rotterdam, 3015 GD, The Netherlands
| | - A Verbon
- Department of Medical Microbiology & Infectious Diseases, Erasmus MC University Medical Center, Rotterdam, 3015 GD, The Netherlands
| | - R W Sauerwein
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, 6500HB, The Netherlands.
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2
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Fabra-García A, Yang AS, Behet MC, Yap XZ, van Waardenburg Y, Kaviraj S, Lanke K, van Gemert GJ, Jore MM, Bousema T, Sauerwein RW. Human antibodies against non-circumsporozoite proteins block Plasmodium falciparum parasite development in hepatocytes. JCI Insight 2022; 7:153524. [PMID: 35167490 PMCID: PMC8986077 DOI: 10.1172/jci.insight.153524] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Accepted: 02/09/2022] [Indexed: 12/02/2022] Open
Abstract
Sporozoite-based approaches currently represent the most effective vaccine strategies for induction of sterile protection against Plasmodium falciparum (Pf) malaria. Clinical development of subunit vaccines is almost exclusively centered on the circum-sporozoite protein (CSP), an abundantly expressed protein on the sporozoite membrane. Anti-CSP antibodies are able to block sporozoite invasion and development in human hepatocytes and subsequently prevent clinical malaria. Here, we have investigated whether sporozoite-induced human antibodies with specificities different from CSP can reduce Pf-liver stage development. IgG preparations were obtained from 12 volunteers inoculated with a protective immunization regime of whole sporozoites under chloroquine prophylaxis. These IgGs were depleted for CSP specificity by affinity chromatography. Recovered non-CSP antibodies were tested for sporozoite membrane binding and for functional inhibition of sporozoite invasion of a human hepatoma cell line and hepatocytes both in vitro and in vivo. Postimmunization IgGs depleted for CS specificity of 9 of 12 donors recognized sporozoite surface antigens. Samples from 5 of 12 donors functionally reduced parasite-liver cell invasion or development using the hepatoma cell line HC-04 and FRG-huHep mice containing human liver cells. The combined data provide clear evidence that non-CSP proteins, as yet undefined, do represent antibody targets for functional immunity against Pf parasites responsible for malaria.
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Affiliation(s)
- Amanda Fabra-García
- Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Annie Sp Yang
- Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Marije C Behet
- Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Xi Zen Yap
- Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Youri van Waardenburg
- Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, Netherlands
| | | | - Kjerstin Lanke
- Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Geert-Jan van Gemert
- Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Matthijs M Jore
- Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Teun Bousema
- Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Robert W Sauerwein
- Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, Netherlands
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3
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McCall MBB, Yap XZ, Bousema T. Optimizing RTS,S Vaccination Strategies: Give It Your Best Parting Shot. J Infect Dis 2020; 222:1581-1584. [DOI: 10.1093/infdis/jiaa423] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 07/09/2020] [Indexed: 11/14/2022] Open
Affiliation(s)
- Matthew B B McCall
- Department of Medical Microbiology, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands
- Institut für Tropenmedizin, Universität Tübingen, Tübingen, Germany
| | - Xi Zen Yap
- Department of Medical Microbiology, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands
| | - Teun Bousema
- Department of Medical Microbiology, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands
- Department of Immunology and Infection, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
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4
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Achan J, Reuling IJ, Yap XZ, Dabira E, Ahmad A, Cox M, Nwakanma D, Tetteh K, Wu L, Bastiaens GJH, Abebe Y, Manoj A, Kaur H, Miura K, Long C, Billingsley PF, Sim BKL, Hoffman SL, Drakeley C, Bousema T, D’Alessandro U. Serologic Markers of Previous Malaria Exposure and Functional Antibodies Inhibiting Parasite Growth Are Associated With Parasite Kinetics Following a Plasmodium falciparum Controlled Human Infection. Clin Infect Dis 2020; 70:2544-2552. [PMID: 31402382 PMCID: PMC7286377 DOI: 10.1093/cid/ciz740] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Accepted: 08/01/2019] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND We assessed the impact of exposure to Plasmodium falciparum on parasite kinetics, clinical symptoms, and functional immunity after controlled human malaria infection (CHMI) in 2 cohorts with different levels of previous malarial exposure. METHODS Nine adult males with high (sero-high) and 10 with low (sero-low) previous exposure received 3200 P. falciparum sporozoites (PfSPZ) of PfSPZ Challenge by direct venous inoculation and were followed for 35 days for parasitemia by thick blood smear (TBS) and quantitative polymerase chain reaction. Endpoints were time to parasitemia, adverse events, and immune responses. RESULTS Ten of 10 (100%) volunteers in the sero-low and 7 of 9 (77.8%) in the sero-high group developed parasitemia detected by TBS in the first 28 days (P = .125). The median time to parasitemia was significantly shorter in the sero-low group than the sero-high group (9 days [interquartile range {IQR} 7.5-11.0] vs 11.0 days [IQR 7.5-18.0], respectively; log-rank test, P = .005). Antibody recognition of sporozoites was significantly higher in the sero-high (median, 17.93 [IQR 12.95-24] arbitrary units [AU]) than the sero-low volunteers (median, 10.54 [IQR, 8.36-12.12] AU) (P = .006). Growth inhibitory activity was significantly higher in the sero-high (median, 21.8% [IQR, 8.15%-29.65%]) than in the sero-low group (median, 8.3% [IQR, 5.6%-10.23%]) (P = .025). CONCLUSIONS CHMI was safe and well tolerated in this population. Individuals with serological evidence of higher malaria exposure were able to better control infection and had higher parasite growth inhibitory activity. CLINICAL TRIALS REGISTRATION NCT03496454.
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Affiliation(s)
- Jane Achan
- Disease Control and Elimination Theme, Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Isaie J Reuling
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Xi Zen Yap
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Edgard Dabira
- Disease Control and Elimination Theme, Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Abdullahi Ahmad
- Disease Control and Elimination Theme, Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Momodou Cox
- Disease Control and Elimination Theme, Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Davis Nwakanma
- Disease Control and Elimination Theme, Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Kevin Tetteh
- Department of Immunology and Infection, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, United Kingdom
| | - Lindsey Wu
- Department of Immunology and Infection, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, United Kingdom
| | - Guido J H Bastiaens
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | | | | | - Harparkash Kaur
- Department of Immunology and Infection, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, United Kingdom
| | - Kazutoyo Miura
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland
| | - Carole Long
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland
| | | | | | | | - Chris Drakeley
- Department of Immunology and Infection, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, United Kingdom
| | - Teun Bousema
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Umberto D’Alessandro
- Disease Control and Elimination Theme, Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, Banjul, The Gambia
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5
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Yap XZ, McCall MBB, Sauerwein RW. Fast and fierce versus slow and smooth: Heterogeneity in immune responses to Plasmodium in the controlled human malaria infection model. Immunol Rev 2020; 293:253-269. [PMID: 31605396 PMCID: PMC6973142 DOI: 10.1111/imr.12811] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 09/11/2019] [Accepted: 09/13/2019] [Indexed: 12/19/2022]
Abstract
Controlled human malaria infection (CHMI) is an established model in clinical malaria research. Upon exposure to Plasmodium falciparum parasites, malaria-naive volunteers differ in dynamics and composition of their immune profiles and subsequent capacity to generate protective immunity. CHMI volunteers are either inflammatory responders who have prominent cellular IFN-γ production primarily driven by adaptive T cells, or tempered responders who skew toward antibody-mediated humoral immunity. When exposed to consecutive CHMIs under antimalarial chemoprophylaxis, individuals who can control parasitemia after a single immunization (fast responders) are more likely to be protected against a subsequent challenge infection. Fast responders tend to be inflammatory responders who can rapidly induce long-lived IFN-γ+ T cell responses. Slow responders or even non-responders can also be protected, but via a more diverse range of responses that take a longer time to reach full protective efficacy, in part due to their tempered phenotype. The latter group can be identified at baseline before CHMI by higher expression of inhibitory ligands CTLA-4 and TIM-3 on CD4+ T cells. Delineating heterogeneity in human immune responses to P. falciparum will facilitate rational design and strategy towards effective malaria vaccines.
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Affiliation(s)
- Xi Zen Yap
- Department of Medical MicrobiologyRadboud University Medical CenterNijmegenThe Netherlands
- Radboud Center for Infectious DiseasesRadboud University Medical CenterNijmegenThe Netherlands
| | - Matthew B. B. McCall
- Department of Medical MicrobiologyRadboud University Medical CenterNijmegenThe Netherlands
- Radboud Center for Infectious DiseasesRadboud University Medical CenterNijmegenThe Netherlands
| | - Robert W. Sauerwein
- Department of Medical MicrobiologyRadboud University Medical CenterNijmegenThe Netherlands
- Radboud Center for Infectious DiseasesRadboud University Medical CenterNijmegenThe Netherlands
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6
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Abstract
Humoral immunity is a critical effector arm for protection against malaria but develops only slowly after repeated infections. T cell-mediated regulatory dynamics affect the development of antibody responses to Plasmodium parasites. Here, we hypothesize that T follicular helper cell (TFH) polarization generated by repeated Plasmodium asexual blood-stage infections delays the onset of protective humoral responses. IFN-γ production promotes polarization toward TFH1 and increased generation of regulatory follicular helper cells (TFR). Delineating the mechanisms that drive TH1 polarization will provide clues for appropriate induction of lasting, protective immunity against malaria.
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Affiliation(s)
- Xi Zen Yap
- Department of Medical Microbiology, RadboudUMC Centre for Infectious Diseases, Nijmegen, Netherlands
| | - Lucie S P Hustin
- Department of Medical Microbiology, RadboudUMC Centre for Infectious Diseases, Nijmegen, Netherlands.,Institut Curie, PSL Research University, CNRS UMR168, Paris, France
| | - Robert W Sauerwein
- Department of Medical Microbiology, RadboudUMC Centre for Infectious Diseases, Nijmegen, Netherlands
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7
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Abstract
Malaria remains a serious threat to global health. Sustained malaria control and, eventually, eradication will only be achieved with a broadly effective malaria vaccine. Yet a fundamental lack of knowledge about how antimalarial immunity is acquired has hindered vaccine development efforts to date. Understanding how malaria-causing parasites modulate the host immune system, specifically dendritic cells (DCs), key initiators of adaptive and vaccine antigen-based immune responses, is vital for effective vaccine design. This review comprehensively summarizes how exposure to Plasmodium spp. impacts human DC function in vivo and in vitro. We have highlighted the heterogeneity of the data observed in these studies, compared and critiqued the models used to generate our current understanding of DC function in malaria, and examined the mechanisms by which Plasmodium spp. mediate these effects. This review highlights potential research directions which could lead to improved efficacy of existing vaccines, and outlines novel targets for next-generation vaccine strategies to target malaria.
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Affiliation(s)
- Xi Zen Yap
- Burnet Institute, Melbourne, VIC, Australia.,Department of Medicine, Dentistry, and Health Sciences, The University of Melbourne, Parkville, VIC, Australia
| | - Rachel J Lundie
- Burnet Institute, Melbourne, VIC, Australia.,Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - James G Beeson
- Burnet Institute, Melbourne, VIC, Australia.,Department of Medicine, Dentistry, and Health Sciences, The University of Melbourne, Parkville, VIC, Australia.,Department of Microbiology and Central Clinical School, Monash University, Clayton, VIC, Australia
| | - Meredith O'Keeffe
- Burnet Institute, Melbourne, VIC, Australia.,Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
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8
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Yap XZ, Lundie RJ, Feng G, Pooley J, Beeson JG, O'Keeffe M. Different Life Cycle Stages of Plasmodium falciparum Induce Contrasting Responses in Dendritic Cells. Front Immunol 2019; 10:32. [PMID: 30766530 PMCID: PMC6365426 DOI: 10.3389/fimmu.2019.00032] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 01/08/2019] [Indexed: 12/02/2022] Open
Abstract
Dendritic cells are key linkers of innate and adaptive immunity. Efficient dendritic cell activation is central to the acquisition of immunity and the efficacy of vaccines. Understanding how dendritic cells are affected by Plasmodium falciparum blood-stage parasites will help to understand how immunity is acquired and maintained, and how vaccine responses may be impacted by malaria infection or exposure. This study investigates the response of dendritic cells to two different life stages of the malaria parasite, parasitized red blood cells and merozoites, using a murine model. We demonstrate that the dendritic cell responses to merozoites are robust whereas dendritic cell activation, particularly CD40 and pro-inflammatory cytokine expression, is compromised in the presence of freshly isolated parasitized red blood cells. The mechanism of dendritic cell suppression by parasitized red blood cells is host red cell membrane-independent. Furthermore, we show that cryopreserved parasitized red blood cells have a substantially reduced capacity for dendritic cell activation.
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Affiliation(s)
- Xi Zen Yap
- Burnet Institute, Melbourne, VIC, Australia.,Department of Medicine, The University of Melbourne, Parkville, VIC, Australia
| | - Rachel J Lundie
- Department of Biochemistry and Molecular Biology and Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Gaoqian Feng
- Burnet Institute, Melbourne, VIC, Australia.,Department of Medicine, The University of Melbourne, Parkville, VIC, Australia
| | - Joanne Pooley
- Department of Biochemistry and Molecular Biology and Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - James G Beeson
- Burnet Institute, Melbourne, VIC, Australia.,Department of Medicine, The University of Melbourne, Parkville, VIC, Australia.,Department of Microbiology, Monash University, Clayton, VIC, Australia.,Central Clinical School, Monash University, Melbourne, VIC, Australia
| | - Meredith O'Keeffe
- Burnet Institute, Melbourne, VIC, Australia.,Department of Biochemistry and Molecular Biology and Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
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9
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Reuling IJ, de Jong GM, Yap XZ, Asghar M, Walk J, van de Schans LA, Koelewijn R, Färnert A, de Mast Q, van der Ven AJ, Bousema T, van Hellemond JJ, van Genderen PJJ, Sauerwein RW. Liver Injury in Uncomplicated Malaria is an Overlooked Phenomenon: An Observational Study. EBioMedicine 2018; 36:131-139. [PMID: 30243492 PMCID: PMC6197763 DOI: 10.1016/j.ebiom.2018.09.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 08/29/2018] [Accepted: 09/11/2018] [Indexed: 11/16/2022] Open
Affiliation(s)
- Isaie J Reuling
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, the Netherlands.
| | - Gerdie M de Jong
- Harbour Hospital, Institute for Tropical Diseases, Rotterdam, the Netherlands; Department of Medical Microbiology and Infectious Diseases, Erasmus MC University Medical Center, Rotterdam, the Netherlands
| | - Xi Zen Yap
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Muhammad Asghar
- Division of Infectious Diseases, Department of Medicine Solna, Karolinska Institute, Stockholm, Sweden
| | - Jona Walk
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Lisanne A van de Schans
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Rob Koelewijn
- Department of Medical Microbiology and Infectious Diseases, Erasmus MC University Medical Center, Rotterdam, the Netherlands
| | - Anna Färnert
- Division of Infectious Diseases, Department of Medicine Solna, Karolinska Institute, Stockholm, Sweden
| | - Quirijn de Mast
- Department of Internal Medicine, Radboud university medical center, Nijmegen, the Netherlands
| | - Andre J van der Ven
- Department of Internal Medicine, Radboud university medical center, Nijmegen, the Netherlands
| | - Teun Bousema
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Jaap J van Hellemond
- Department of Medical Microbiology and Infectious Diseases, Erasmus MC University Medical Center, Rotterdam, the Netherlands
| | - Perry J J van Genderen
- Harbour Hospital, Institute for Tropical Diseases, Rotterdam, the Netherlands; Department of Medical Microbiology and Infectious Diseases, Erasmus MC University Medical Center, Rotterdam, the Netherlands
| | - Robert W Sauerwein
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, the Netherlands.
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10
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Mugyenyi CK, Elliott SR, Yap XZ, Feng G, Boeuf P, Fegan G, Osier FFH, Fowkes FJI, Avril M, Williams TN, Marsh K, Beeson JG. Declining Malaria Transmission Differentially Impacts the Maintenance of Humoral Immunity to Plasmodium falciparum in Children. J Infect Dis 2017; 216:887-898. [PMID: 28973483 DOI: 10.1093/infdis/jix370] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Accepted: 07/31/2017] [Indexed: 12/13/2022] Open
Abstract
Background We investigated the poorly understood impact of declining malaria transmission on maintenance of antibodies to Plasmodium falciparum merozoite antigens and infected erythrocytes (IEs), including functional immunity. Methods In a 3-year longitudinal cohort of 300 Kenyan children, antibodies to different AMA1 and MSP2 alleles of merozoites, IE surface antigens, and antibody functional activities were quantified. Results Over a period in which malaria transmission declined markedly, AMA1 and MSP2 antibodies decreased substantially; estimated half-lives of antibody duration were 0.8 year and 1-3 years, respectively. However, 69%-74% of children maintained their seropositivity to AMA1 alleles and 42%-52% to MSP2 alleles. Levels and prevalence of antimerozoite antibodies were consistently associated with increasing age and concurrent parasitemia. Antibodies promoting opsonic phagocytosis of merozoites declined rapidly (half-life, 0.15 years). In contrast, complement-fixing antibodies to merozoites did not decline and antibodies to IE surface antigens expressing virulent phenotypes were much better maintained (half-life, 4-10 years). Conclusions A decline in malaria transmission is associated with reduction in naturally acquired immunity. However, loss of immunity is not universal; some key functional responses and antibodies to IEs were better maintained and these may continue to provide some protection. Findings have implications for malaria surveillance and control measures and informing vaccine development.
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Affiliation(s)
- Cleopatra K Mugyenyi
- Kenya Medical Research Institute (KEMRI), Centre for Geographic Medicine, Coast, KEMRI-Wellcome Trust Research Programme, Kilifi.,Burnet Institute, Melbourne
| | | | - Xi Zen Yap
- Burnet Institute, Melbourne.,Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Victoria, Australia
| | | | - Philippe Boeuf
- Burnet Institute, Melbourne.,Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Victoria, Australia
| | - Gregory Fegan
- Kenya Medical Research Institute (KEMRI), Centre for Geographic Medicine, Coast, KEMRI-Wellcome Trust Research Programme, Kilifi
| | - Faith F H Osier
- Kenya Medical Research Institute (KEMRI), Centre for Geographic Medicine, Coast, KEMRI-Wellcome Trust Research Programme, Kilifi.,Burnet Institute, Melbourne.,Department of Infectious Diseases, Parasitology, Universitätsklinikum Heidelberg, Germany
| | - Freya J I Fowkes
- Burnet Institute, Melbourne.,Department of Epidemiology and Preventive Medicine, Monash University.,Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Victoria, Australia
| | - Marion Avril
- Centre for Infectious Disease Research, Seattle, Washington
| | - Thomas N Williams
- Kenya Medical Research Institute (KEMRI), Centre for Geographic Medicine, Coast, KEMRI-Wellcome Trust Research Programme, Kilifi.,Imperial College, London, United Kingdom
| | - Kevin Marsh
- Kenya Medical Research Institute (KEMRI), Centre for Geographic Medicine, Coast, KEMRI-Wellcome Trust Research Programme, Kilifi
| | - James G Beeson
- Burnet Institute, Melbourne.,Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Victoria, Australia.,Central Clinical School and Department of Microbiology, Monash University, Melbourne, Victoria, Australia
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