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Arora G, Chuang YM, Sinnis P, Dimopoulos G, Fikrig E. Malaria: influence of Anopheles mosquito saliva on Plasmodium infection. Trends Immunol 2023; 44:256-265. [PMID: 36964020 PMCID: PMC10074230 DOI: 10.1016/j.it.2023.02.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 02/13/2023] [Accepted: 02/14/2023] [Indexed: 03/26/2023]
Abstract
Malaria is caused by Plasmodium protozoa that are transmitted by anopheline mosquitoes. Plasmodium sporozoites are released with saliva when an infected female mosquito takes a blood meal on a vertebrate host. Sporozoites deposited into the skin must enter a blood vessel to start their journey towards the liver. After migration out of the mosquito, sporozoites are associated with, or in proximity to, many components of vector saliva in the skin. Recent work has elucidated how Anopheles saliva, and components of saliva, can influence host-pathogen interactions during the early stage of Plasmodium infection in the skin. Here, we discuss how components of Anopheles saliva can modulate local host responses and affect Plasmodium infectivity. We hypothesize that therapeutic strategies targeting mosquito salivary proteins can play a role in controlling malaria and other vector-borne diseases.
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Affiliation(s)
- Gunjan Arora
- Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, 06520, USA
| | - Yu-Min Chuang
- Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, 06520, USA
| | - Photini Sinnis
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA
| | - George Dimopoulos
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA
| | - Erol Fikrig
- Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, 06520, USA.
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Kearney EA, Agius PA, Chaumeau V, Cutts JC, Simpson JA, Fowkes FJI. Anopheles salivary antigens as serological biomarkers of vector exposure and malaria transmission: A systematic review with multilevel modelling. eLife 2021; 10:e73080. [PMID: 34939933 PMCID: PMC8860437 DOI: 10.7554/elife.73080] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 12/21/2021] [Indexed: 12/25/2022] Open
Abstract
Background Entomological surveillance for malaria is inherently resource-intensive and produces crude population-level measures of vector exposure which are insensitive in low-transmission settings. Antibodies against Anopheles salivary proteins measured at the individual level may serve as proxy biomarkers for vector exposure and malaria transmission, but their relationship is yet to be quantified. Methods A systematic review of studies measuring antibodies against Anopheles salivary antigens (PROSPERO: CRD42020185449). Multilevel modelling (to account for multiple study-specific observations [level 1], nested within study [level 2], and study nested within country [level 3]) estimated associations between seroprevalence with Anopheles human biting rate (HBR) and malaria transmission measures. Results From 3981 studies identified in literature searches, 42 studies across 16 countries were included contributing 393 study-specific observations of anti-Anopheles salivary antibodies determined in 42,764 samples. A positive association between HBR (log transformed) and seroprevalence was found; overall a twofold (100% relative) increase in HBR was associated with a 23% increase in odds of seropositivity (OR: 1.23, 95% CI: 1.10-1.37; p<0.001). The association between HBR and Anopheles salivary antibodies was strongest with concordant, rather than discordant, Anopheles species. Seroprevalence was also significantly positively associated with established epidemiological measures of malaria transmission: entomological inoculation rate, Plasmodium spp. prevalence, and malarial endemicity class. Conclusions Anopheles salivary antibody biomarkers can serve as a proxy measure for HBR and malaria transmission, and could monitor malaria receptivity of a population to sustain malaria transmission. Validation of Anopheles species-specific biomarkers is important given the global heterogeneity in the distribution of Anopheles species. Salivary biomarkers have the potential to transform surveillance by replacing impractical, inaccurate entomological investigations, especially in areas progressing towards malaria elimination. Funding Australian National Health and Medical Research Council, Wellcome Trust.
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Affiliation(s)
- Ellen A Kearney
- The McFarlane Burnet Institute of Medical Research and Public HealthMelbourneAustralia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of MelbourneMelbourneAustralia
| | - Paul A Agius
- The McFarlane Burnet Institute of Medical Research and Public HealthMelbourneAustralia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of MelbourneMelbourneAustralia
- Department of Epidemiology and Preventive Medicine, Monash UniversityMelbourneAustralia
| | - Victor Chaumeau
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol UniversityMae SotThailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of OxfordOxfordUnited Kingdom
| | - Julia C Cutts
- The McFarlane Burnet Institute of Medical Research and Public HealthMelbourneAustralia
- Department of Medicine at the Doherty Institute, The University of MelbourneMelbourneAustralia
| | - Julie A Simpson
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of MelbourneMelbourneAustralia
| | - Freya JI Fowkes
- The McFarlane Burnet Institute of Medical Research and Public HealthMelbourneAustralia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of MelbourneMelbourneAustralia
- Department of Epidemiology and Preventive Medicine, Monash UniversityMelbourneAustralia
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3
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Influence of Host-Related Factors and Exposure to Mosquito Bites on the Dynamics of Antibody Response to Plasmodium falciparum Antigens. Trop Med Infect Dis 2021; 6:tropicalmed6040185. [PMID: 34698307 PMCID: PMC8544703 DOI: 10.3390/tropicalmed6040185] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 09/30/2021] [Accepted: 10/11/2021] [Indexed: 11/24/2022] Open
Abstract
Humoral immunity to Plasmodium falciparum is acquired after repeated infections, and can lead to clinical protection. This study aimed to evaluate how human-, parasite-, and environment-related determinants can modulate the dynamics of IgG responses to Plasmodium falciparum after an infection. Individuals (n = 68, average age = 8.2 years) with uncomplicated malaria were treated with ACT and followed up for 42 days. IgG responses to P. falciparum merozoite antigens (PfMSP1, PfMSP3, PfAMA1, PfGLURP-R0), to whole schizont extract (PfSchz), and to Anopheles gSG6-P1 and Aedes Nterm–34 kDa salivary peptides were measured. Regression analyses were used to identify factors that influence the dynamics of IgG response to P. falciparum antigen between D0 and D42, including demographic and biological factors and the level of exposure to mosquito bites. The dynamics of IgG response to P. falciparum differed according to the antigen. According to multivariate analysis, IgG responses to PfSchz and to PfGLURP-R0 appear to be affected by exposure to Aedes saliva and are associated with age, parasite density, and anti-Plasmodium pre-existing immune response at study inclusion. The present work shows that human exposure to Aedes saliva may contribute, in addition to other factors, to the regulation of anti-Plasmodium immune responses during a natural infection.
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Isebe TI, Bargul JL, Gichuki BM, Njunge JM, Tuju J, Rono MK. Molecular characterization of Plasmodium falciparum PHISTb proteins as potential targets of naturally-acquired immunity against malaria. Wellcome Open Res 2021. [DOI: 10.12688/wellcomeopenres.15919.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Background: Plasmodium falciparum causes the deadliest form of malaria in humans. Upon infection, the host’s infected red blood cells (iRBCs) are remodelled by exported parasite proteins to provide a niche for parasite development and maturation. Methods: Here we analysed the role of three PHISTb proteins Pf3D7_0532400, Pf3D7_1401600, and Pf3D7_1102500 by expressing recombinant proteins and evaluated antibody responses against these proteins using immune sera from malaria-exposed individuals from Kenya and The Gambia in Africa. Results: Children and adults from malaria-endemic regions recognized the three PHISTb proteins. Responses against PHISTb proteins varied with malaria transmission intensity in three different geographical sites in Kenya (Siaya and Takaungu) and The Gambia (Sukuta). Antibody responses against PHISTb antigens Pf3D7_1102500 and Pf3D7_1401600 were higher in Sukuta, a low transmission region in Gambia, compared to Siaya, a high transmission region in western Kenya, unlike Pf3D7_0532400. Anti-PHIST responses indicate negative correlation between antibody levels and malaria transmission intensity for Pf3D7_1102500 and Pf3D7_1401600. We report a correlation in antibody responses between schizont and gametocyte extract, but this is not statistically significant (cor=0.102, p=0.2851, CI=95%) and, Pf3D7_0532400 (cor=0.11, p=0.249, CI=95%) and Pf3D7_1401600 (cor=0.02, p=0.7968, CI=95%). We report a negative correlation in antibody responses between schizont and Pf3D7_1102500 (cor=-0.008, p=0.9348, CI=95%). There is a correlation between gametocyte extract and Pf3D7_1401600 (cor=-0.0402, p=0.6735, CI=95%), Pf3D7_1102500 (cor=0.0758, p=0.4271, CI=95%) and Pf3D7_0532400 (cor=0.155, p=0.1028, CI=95%). Acquisition of anti-PHIST antibodies correlates with exposure to malaria for Pf3D7_0532400 (p=0.009) but not Pf3D7_1102500 and Pf3D7_1401600 (p=0.507 and p=0.15, respectively, CI=95%). Children aged below 2 years had the lowest antibody levels which do not correlate with age differences. Conclusions: Collectively, these findings provide evidence of natural immunity against PHISTb antigens that varies with level of malaria exposure and underscore their potential as possible serological markers to P. falciparum infection aimed at contributing to malaria control through vaccine development.
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Isebe TI, Bargul JL, Gichuki BM, Njunge JM, Tuju J, Rono MK. Molecular characterization of Plasmodium falciparum PHISTb proteins as potential targets of naturally-acquired immunity against malaria. Wellcome Open Res 2020. [DOI: 10.12688/wellcomeopenres.15919.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Background: Plasmodium falciparum causes the deadliest form of malaria in humans. Upon infection, the host’s infected red blood cells (iRBCs) are remodelled by exported parasite proteins in order to provide a niche for parasite development and maturation. Methods: Here we analysed the role of three PHISTb proteins Pf3D7_0532400, Pf3D7_1401600, and Pf3D7_1102500 by expressing recombinant proteins and evaluated antibody responses against these proteins using immune sera from malaria-exposed individuals from Kenya and The Gambia in Africa. Results: Our findings show that children and adults from malaria-endemic regions recognized the three PHISTb proteins. Responses against the PHISTb proteins varied with malaria transmission intensity in three different geographical sites in Kenya (Siaya and Takaungu) and The Gambia (Sukuta). Antibody responses against PHISTb antigens Pf3D7_1102500 and Pf3D7_1401600 were higher in Sukuta, a low transmission region in the Gambia, as compared to Siaya, a high transmission region in western Kenya, unlike Pf3D7_0532400. Anti-PHIST responses show a negative correlation between antibody levels and malaria transmission intensity for two PHIST antigens, Pf3D7_1102500 and Pf3D7_1401600. However, we report a correlation in antibody responses between schizont extract and Pf3D7_0532400 (p=0.00582). Acquisition of anti-PHIST antibodies was correlated with exposure to malaria for PHISTb protein Pf3D7_0532400 (p=0.009) but not the other PHIST antigens Pf3D7_1102500 and Pf3D7_1401600 (p=0.507 and p=0.15, respectively, CI=95%). Children aged below 2 years had the lowest antibody levels, but the responses do not correlate with age differences. Conclusions: Collectively, these findings provide evidence of natural immunity against PHISTb antigens that varies with level of malaria exposure and underscore potential for these parasite antigens as possible serological markers to P. falciparum infection aimed at contributing to malaria control through vaccine development.
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Aka KG, Traoré DF, Sagna AB, Zoh DD, Assi SB, Tchiekoi BN, Adja AM, Remoue F, Poinsignon A. Pattern of antibody responses to Plasmodium falciparum antigens in individuals differentially exposed to Anopheles bites. Malar J 2020; 19:83. [PMID: 32085710 PMCID: PMC7033907 DOI: 10.1186/s12936-020-03160-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Accepted: 02/12/2020] [Indexed: 11/16/2022] Open
Abstract
Background In malaria-endemic areas, human populations are frequently exposed to immunomodulatory salivary components injected during mosquito blood feeding. The consequences on pathogen-specific immune responses are not well known. This study evaluated and compared the humoral responses specific to merozoite stage vaccine candidates of Plasmodium falciparum, in children differentially exposed to Anopheles bites in a natural setting. Methods The cross-sectional study was carried out in Bouaké (Côte d’Ivoire) where entomological data and blood samples from children (0–14 years) were collected in two sites with similar malaria prevalence. Antibody (IgG, IgG1, IgG3) responses to PfAMA1 and PfMSP1 were evaluated by ELISA. Univariate and multivariate analysis were performed to assess the relationship between the immune responses to P. falciparum antigens and exposure to Anopheles bites in the total cohort and in each site, separately. The individual level of exposure to Anopheles bites was evaluated by quantifying specific IgG response to the Anopheles gSG6-P1 salivary peptide, which represents a proxy of Anopheles exposure. Results The anti-Plasmodium humoral responses were different according to the level of exposure of children, with those highly exposed to Anopheles presenting significantly lower antibody responses to PfMSP1 in total population (IgG and IgG3) and in Petessou village (IgG, IgG1, IgG3). No significant difference was seen for PfAMA1 antigen between children differently exposed to Anopheles. In Dar-es-Salam, a neighbourhood where a high Culex density was reported, children presented very low antibody levels specific to both antigens, and no difference according to the exposure to Anopheles bites was found. Conclusion These findings may suggest that immunomodulatory components of Anopheles saliva, in addition to other factors, may participate to the modulation of the humoral response specific to Plasmodium merozoite stage antigens. This epidemiological observation may form a starting point for additional work to decipher the role of mosquito saliva on the modulation of the anti-Plasmodium acquired immunity and clinical protection in combining both field and ex vivo immunological studies.
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Affiliation(s)
- Kakou G Aka
- Institut Pierre Richet, Institut National de Santé Publique, Bouaké, Côte d'Ivoire. .,MIVEGEC, University of Montpellier, CNRS, IRD, Montpellier, France.
| | - Dipomin F Traoré
- Institut Pierre Richet, Institut National de Santé Publique, Bouaké, Côte d'Ivoire.,MIVEGEC, University of Montpellier, CNRS, IRD, Montpellier, France.,UFR Sciences de la Nature, Université Nangui Abrogoua, Abidjan, Côte d'Ivoire
| | - André B Sagna
- Institut Pierre Richet, Institut National de Santé Publique, Bouaké, Côte d'Ivoire.,MIVEGEC, University of Montpellier, CNRS, IRD, Montpellier, France
| | - Dounin D Zoh
- Institut Pierre Richet, Institut National de Santé Publique, Bouaké, Côte d'Ivoire.,UFR Biosciences, Université Félix Houphouët Boigny, Abidjan, Côte d'Ivoire
| | - Serge B Assi
- Institut Pierre Richet, Institut National de Santé Publique, Bouaké, Côte d'Ivoire
| | | | - Akré M Adja
- Institut Pierre Richet, Institut National de Santé Publique, Bouaké, Côte d'Ivoire.,UFR Biosciences, Université Félix Houphouët Boigny, Abidjan, Côte d'Ivoire
| | - Franck Remoue
- Institut Pierre Richet, Institut National de Santé Publique, Bouaké, Côte d'Ivoire.,MIVEGEC, University of Montpellier, CNRS, IRD, Montpellier, France
| | - Anne Poinsignon
- Institut Pierre Richet, Institut National de Santé Publique, Bouaké, Côte d'Ivoire.,MIVEGEC, University of Montpellier, CNRS, IRD, Montpellier, France
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Acquisition of natural humoral immunity to P. falciparum in early life in Benin: impact of clinical, environmental and host factors. Sci Rep 2016; 6:33961. [PMID: 27670685 PMCID: PMC5037375 DOI: 10.1038/srep33961] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Accepted: 08/04/2016] [Indexed: 01/01/2023] Open
Abstract
To our knowledge, effects of age, placental malaria infection, infections during follow-up, nutritional habits, sickle-cell trait and individual exposure to Anopheles bites were never explored together in a study focusing on the acquisition of malaria antibody responses among infants living in endemic areas.Five hundred and sixty-seven Beninese infants were weekly followed-up from birth to 18 months of age. Immunoglobulin G (IgG), IgG1 and IgG3 specific for 5 malaria antigens were measured every 3 months. A linear mixed model was used to analyze the effect of each variable on the acquisition of antimalarial antibodies in 6-to18-month old infants in univariate and multivariate analyses. Placental malaria, nutrition intakes and sickle-cell trait did not influence the infant antibody levels to P. falciparum antigens. In contrary, age, malaria antibody levels at birth, previous and present malaria infections as well as exposure to Anopheles bites were significantly associated with the natural acquisition of malaria antibodies in 6-to18-month old Beninese infants. This study highlighted inescapable factors to consider simultaneously in an immuno-epidemiological study or a vaccine trial in early life.
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8
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McDowell MA. Vector-transmitted disease vaccines: targeting salivary proteins in transmission (SPIT). Trends Parasitol 2015; 31:363-72. [PMID: 26003330 DOI: 10.1016/j.pt.2015.04.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 04/20/2015] [Accepted: 04/27/2015] [Indexed: 12/25/2022]
Abstract
More than half the population of the world is at risk for morbidity and mortality from vector-transmitted diseases, and emerging vector-transmitted infections are threatening new populations. Rising insecticide resistance and lack of efficacious vaccines highlight the need for novel control measures. One such approach is targeting the vector-host interface by incorporating vector salivary proteins in anti-pathogen vaccines. Debate remains about whether vector saliva exposure exacerbates or protects against more severe clinical manifestations, induces immunity through natural exposure or extends to all vector species and associated pathogens. Nevertheless, exploiting this unique biology holds promise as a viable strategy for the development of vaccines against vector-transmitted diseases.
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Affiliation(s)
- Mary Ann McDowell
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.
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9
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Ondigo BN, Hodges JS, Ireland KF, Magak NG, Lanar DE, Dutta S, Narum DL, Park GS, Ofulla AV, John CC. Estimation of recent and long-term malaria transmission in a population by antibody testing to multiple Plasmodium falciparum antigens. J Infect Dis 2014; 210:1123-32. [PMID: 24737801 DOI: 10.1093/infdis/jiu225] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Tools that estimate recent and long-term malaria transmission in a population would be highly useful for malaria elimination programs. METHODS The prevalence of antibodies to 11 Plasmodium falciparum antigens was assessed by cytometric bead assay or enzyme-linked immunosorbent assay in 1000 people in a highland area of Kenya over 14 months, during a period of interrupted malaria transmission. RESULTS Antibodies differed by antigen in acquisition with age: rapid (>80% antibody positive by age 20 years, 5 antigens), moderate (>40% positive by age 20 years, 3 antigens), or slow (<40% positive by age 20 years, 3 antigens). Antibody seroreversion rates in the 14 months between samples decreased with age rapidly (7 antigens), slowly (3 antigens), or remained high at all ages (schizont extract). Estimated antibody half-lives in individuals >10 years of age were long (40 to >80 years) for 5 antigens, moderate (5-20 years) for 3 antigens, and short (<1 year) for 3 antigens. CONCLUSIONS Antibodies to P. falciparum antigens in malaria-endemic areas vary by age, antigen, and time since last exposure to P. falciparum. Multiplex P. falciparum antibody testing could provide estimates of long-term and recent malaria transmission and potentially of a population's susceptibility to future clinical malaria.
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Affiliation(s)
- Bartholomew N Ondigo
- Department of Biomedical Science and Technology, Maseno University Center for Global Health Research, Kenya Medical Research Institute, Kisumu
| | - James S Hodges
- Division of Biostatistics, School of Public Health, University of Minnesota
| | | | | | - David E Lanar
- Center for Global Health Research, Kenya Medical Research Institute, Kisumu
| | - Sheetij Dutta
- Center for Global Health Research, Kenya Medical Research Institute, Kisumu
| | - David L Narum
- Malaria Vaccine Branch, Walter Reed Army Institute for Research, Silver Spring
| | - Gregory S Park
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institute of Health, Rockville, Maryland
| | - Ayub V Ofulla
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institute of Health, Rockville, Maryland
| | - Chandy C John
- Department of Pediatrics, University of Minnesota Medical School Center for Global Health Research, Kenya Medical Research Institute, Kisumu
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Pinkevych M, Petravic J, Chelimo K, Vulule J, Kazura JW, Moormann AM, Davenport MP. Decreased growth rate of P. falciparum blood stage parasitemia with age in a holoendemic population. J Infect Dis 2013; 209:1136-43. [PMID: 24265441 DOI: 10.1093/infdis/jit613] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
In malaria holoendemic settings, decreased parasitemia and clinical disease is associated with age and cumulative exposure. The relative contribution of acquired immunity against various stages of the parasite life cycle is not well understood. In particular, it is not known whether changes in infection dynamics can be best explained by decreasing rates of infection, or by decreased growth rates of parasites in blood. Here, we analyze the dynamics of Plasmodium falciparum infection after treatment in a cohort of 197 healthy study participants of different ages. We use both polymerase chain reaction (PCR) and microscopy detection of parasitemia in order to understand parasite growth rates and infection rates over time. The more sensitive PCR assay detects parasites earlier than microscopy, and demonstrates a higher overall prevalence of infection than microscopy alone. The delay between PCR and microscopy detection is significantly longer in adults compared with children, consistent with slower parasite growth with age. We estimated the parasite multiplication rate from delay to PCR and microscopy detections of parasitemia. We find that both the delay between PCR and microscopy infection as well as the differing reinfection dynamics in different age groups are best explained by a slowing of parasite growth with age.
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Affiliation(s)
- Mykola Pinkevych
- Centre for Vascular Research, University of New South Wales, Sydney, New South Wales, Australia
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11
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Sagna AB, Gaayeb L, Sarr JB, Senghor S, Poinsignon A, Boutouaba-Combe S, Schacht AM, Hermann E, Faye N, Remoue F, Riveau G. Plasmodium falciparum infection during dry season: IgG responses to Anopheles gambiae salivary gSG6-P1 peptide as sensitive biomarker for malaria risk in Northern Senegal. Malar J 2013; 12:301. [PMID: 23988032 PMCID: PMC3766161 DOI: 10.1186/1475-2875-12-301] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 08/27/2013] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND The Northern part of Senegal is characterized by a low and seasonal transmission of malaria. However, some Plasmodium falciparum infections and malaria clinical cases are reported during the dry season. This study aims to assess the relationship between IgG antibody (Ab) responses to gSG6-P1 mosquito salivary peptide and the prevalence of P. falciparum infection in children during the dry season in the Senegal River Valley. The positive association of the Ab response to gSG6-P1, as biomarker of human exposure to Anopheles vector bite, and P. falciparum infectious status (uninfected, infected-asymptomatic or infected-symptomatic) will allow considering this biomarker as a potential indicator of P. falciparum infection risk during the dry season. METHODS Microscopic examination of thick blood smears was performed in 371 and 310 children at the start (January) and at the end (June) of the dry season, respectively, in order to assess the prevalence of P. falciparum infection. Collected sera were used to evaluate IgG response to gSG6-P1 by ELISA. Association between parasitological and clinical data (infected-asymptomatic or infected-symptomatic) and the anti-gSG6-P1 IgG levels were evaluated during this period. RESULTS The prevalence of P. falciparum infection was very low to moderate according to the studied period and was higher in January (23.5%) compared to June (3.5%). Specific IgG response was also different between uninfected children and asymptomatic carriers of the parasite. Children with P. falciparum infection in the dry season showed higher IgG Ab levels to gSG6-P1 than uninfected children. CONCLUSIONS The results strengthen the hypothesis that malaria transmission is maintained during the dry season in an area of low and seasonal transmission. The measurement of IgG responses to gSG6-P1 salivary peptide could be a pertinent indicator of human malaria reservoir or infection risk in this particular epidemiological context. This promising immunological marker could be useful for the evaluation of the risk of P. falciparum exposure observed during dry season and, by consequences, could be used for the survey of potential pre-elimination situation.
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Affiliation(s)
- André B Sagna
- Centre de Recherche Biomédicale Espoir Pour La Santé, 269 Route de la corniche, Sor, BP: 226, Saint-Louis, Sénégal
- Département de Biologie Animale, Laboratoire de parasitologie générale, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Lobna Gaayeb
- Centre de Recherche Biomédicale Espoir Pour La Santé, 269 Route de la corniche, Sor, BP: 226, Saint-Louis, Sénégal
- CIIL, Inserm U1019, CNRS UMR 8204, Université Lille Nord de France, Institut Pasteur de Lille, 1 rue du Pr. Calmette, 59019 Lille cedex, France
| | - Jean B Sarr
- Centre de Recherche Biomédicale Espoir Pour La Santé, 269 Route de la corniche, Sor, BP: 226, Saint-Louis, Sénégal
- Institut de Recherche pour le Développement, UMR 224 MIVEGEC, 911 avenue Agropolis, BP: 64501F-34394 Montpellier, France
| | - Simon Senghor
- Centre de Recherche Biomédicale Espoir Pour La Santé, 269 Route de la corniche, Sor, BP: 226, Saint-Louis, Sénégal
| | - Anne Poinsignon
- Institut de Recherche pour le Développement, UMR 224 MIVEGEC, 911 avenue Agropolis, BP: 64501F-34394 Montpellier, France
| | - Samy Boutouaba-Combe
- Centre de Recherche Biomédicale Espoir Pour La Santé, 269 Route de la corniche, Sor, BP: 226, Saint-Louis, Sénégal
| | - Anne-Marie Schacht
- Centre de Recherche Biomédicale Espoir Pour La Santé, 269 Route de la corniche, Sor, BP: 226, Saint-Louis, Sénégal
- CIIL, Inserm U1019, CNRS UMR 8204, Université Lille Nord de France, Institut Pasteur de Lille, 1 rue du Pr. Calmette, 59019 Lille cedex, France
| | - Emmanuel Hermann
- CIIL, Inserm U1019, CNRS UMR 8204, Université Lille Nord de France, Institut Pasteur de Lille, 1 rue du Pr. Calmette, 59019 Lille cedex, France
| | - Ngor Faye
- Département de Biologie Animale, Laboratoire de parasitologie générale, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Franck Remoue
- Institut de Recherche pour le Développement, UMR 224 MIVEGEC, 911 avenue Agropolis, BP: 64501F-34394 Montpellier, France
- Centre de Recherche Entomologique de Cotonou, BP: 4414, Cotonou RP 01, Bénin
| | - Gilles Riveau
- Centre de Recherche Biomédicale Espoir Pour La Santé, 269 Route de la corniche, Sor, BP: 226, Saint-Louis, Sénégal
- CIIL, Inserm U1019, CNRS UMR 8204, Université Lille Nord de France, Institut Pasteur de Lille, 1 rue du Pr. Calmette, 59019 Lille cedex, France
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Sagna AB, Sarr JB, Gaayeb L, Drame PM, Ndiath MO, Senghor S, Sow CS, Poinsignon A, Seck M, Hermann E, Schacht AM, Faye N, Sokhna C, Remoue F, Riveau G. gSG6-P1 salivary biomarker discriminates micro-geographical heterogeneity of human exposure to Anopheles bites in low and seasonal malaria areas. Parasit Vectors 2013; 6:68. [PMID: 23497646 PMCID: PMC3631127 DOI: 10.1186/1756-3305-6-68] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 03/08/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Over the past decade, a sharp decline of malaria burden has been observed in several countries. Consequently, the conventional entomological methods have become insufficiently sensitive and probably under-estimate micro-geographical heterogeneity of exposure and subsequent risk of malaria transmission. In this study, we investigated whether the human antibody (Ab) response to Anopheles salivary gSG6-P1 peptide, known as a biomarker of Anopheles exposure, could be a sensitive and reliable tool for discriminating human exposure to Anopheles bites in area of low and seasonal malaria transmission. METHODS A multi-disciplinary survey was performed in Northern Senegal where An. gambiae s.l. is the main malaria vector. Human IgG Ab response to gSG6-P1 salivary peptide was compared according to the season and villages in children from five villages in the middle Senegal River valley, known as a low malaria transmission area. RESULTS IgG levels to gSG6-P1 varied considerably according to the villages, discriminating the heterogeneity of Anopheles exposure between villages. Significant increase of IgG levels to gSG6-P1 was observed during the peak of exposure to Anopheles bites, and decreased immediately after the end of the exposure season. In addition, differences in the season-dependent specific IgG levels between villages were observed after the implementation of Long-Lasting Insecticidal Nets by The National Malaria Control Program in this area. CONCLUSION The gSG6-P1 salivary peptide seems to be a reliable tool to discriminate the micro-geographical heterogeneity of human exposure to Anopheles bites in areas of very low and seasonal malaria transmission. A biomarker such as this could also be used to monitor and evaluate the possible heterogeneous effectiveness of operational vector control programs in low-exposure areas.
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Affiliation(s)
- André Barembaye Sagna
- Centre de Recherche Biomédicale (CRB) Espoir Pour La Santé, 269 Route de la corniche, Sor - BP: 226, Saint-Louis, Sénégal.
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13
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Pinkevych M, Petravic J, Chelimo K, Kazura JW, Moormann AM, Davenport MP. The dynamics of naturally acquired immunity to Plasmodium falciparum infection. PLoS Comput Biol 2012; 8:e1002729. [PMID: 23093922 PMCID: PMC3475668 DOI: 10.1371/journal.pcbi.1002729] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 08/21/2012] [Indexed: 11/18/2022] Open
Abstract
Severe malaria occurs predominantly in young children and immunity to clinical disease is associated with cumulative exposure in holoendemic settings. The relative contribution of immunity against various stages of the parasite life cycle that results in controlling infection and limiting disease is not well understood. Here we analyse the dynamics of Plasmodium falciparum malaria infection after treatment in a cohort of 197 healthy study participants of different ages in order to model naturally acquired immunity. We find that both delayed time-to-infection and reductions in asymptomatic parasitaemias in older age groups can be explained by immunity that reduces the growth of blood stage as opposed to liver stage parasites. We found that this mechanism would require at least two components – a rapidly acting strain-specific component, as well as a slowly acquired cross-reactive or general immunity to all strains. Analysis and modelling of malaria infection dynamics and naturally acquired immunity with age provides important insights into what mechanisms of immune control may be harnessed by malaria vaccine strategists. Human malaria infections resulting in serious complications and death occur predominantly in young children, and resistance is gradually acquired with repeated exposure. Malaria parasites have two major stages within the human host during its life cycle: an initial liver stage, and the subsequent blood stage, where parasites replicate in and destroy red blood cells. The mechanisms of acquired resistance to severe malaria may involve immunity to both the liver and blood stage parasites. However the relative contribution of each type of immunity is not yet understood. To gain novel insight, we have analysed data from a malaria exposed cohort from western Kenya. We used mathematical modeling to understand what form of immunity is consistent with the observed rates of reinfection in adults and children seen in the field study data. We found that the reinfection pattern can be completely explained by blood stage immunity. Moreover, the blood stage immunity must consist of rapidly-induced strain-specific immunity that clears individual infections, and general immunity that accumulates slowly and decreases the average parasite growth rate with age. Understanding the dynamics of naturally acquired immunity and infection provides important insights for effective vaccine development.
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Affiliation(s)
- Mykola Pinkevych
- Centre for Vascular Research, University of New South Wales, Sydney, New South Wales, Australia
| | - Janka Petravic
- Centre for Vascular Research, University of New South Wales, Sydney, New South Wales, Australia
| | | | - James W. Kazura
- Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Ann M. Moormann
- University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Miles P. Davenport
- Centre for Vascular Research, University of New South Wales, Sydney, New South Wales, Australia
- * E-mail:
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14
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Kynast-Wolf G, Wakilzadeh W, Coulibaly B, Schnitzler P, Traoré C, Becher H, Müller O. ITN protection, MSP1 antibody levels and malaria episodes in young children of rural Burkina Faso. Acta Trop 2012; 123:117-22. [PMID: 22569564 DOI: 10.1016/j.actatropica.2012.04.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 03/29/2012] [Accepted: 04/22/2012] [Indexed: 10/28/2022]
Abstract
Malaria blood-stage vaccines are in an early phase of clinical development with MSP1 being a major antigen candidate. There are limited data on the protective efficacy of antibodies against subunits of MSP1 in the malaria endemic areas of sub-Saharan Africa. This prospective cohort study was nested into a large insecticide-treated mosquito net (ITN) trial during which neonates were individually randomised to ITN protection from birth vs. protection from month six onwards in rural Burkina Faso. A sub sample of 120 children from three villages was followed for 10 months with six measurements of MSP1(42) antibodies (ELISA based on recombinant 42kDa fragment) and daily assessment of malaria episodes. Time to the next malaria episode was determined in relation to MSP1(42) antibody titres. MSP1(42) antibody titres were dependent on age, season, ITN-group, number of previous malaria episodes and parasitaemia. There were no significant differences in time until the next malaria episode in children with low compared to children with high MSP1(42) antibody titres at any point in time (101 vs. 97 days in May, p=0.6; 58 vs. 84 days in September, p=0.3; 144 vs. 161 days in March, p=0.5). The findings of this study support the short-lived nature of the humoral immune response in infants of malaria endemic areas. The study provides no evidence for antibodies against a subunit of MSP1 being protective against new malaria episodes in infants.
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Affiliation(s)
- Gisela Kynast-Wolf
- Institute of Public Health, Ruprecht-Karls-University Heidelberg, Germany.
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15
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Sarr JB, Samb B, Sagna AB, Fortin S, Doucoure S, Sow C, Senghor S, Gaayeb L, Guindo S, Schacht AM, Rogerie F, Hermann E, Dia I, Konate L, Riveau G, Remoue F. Differential acquisition of human antibody responses to Plasmodium falciparum according to intensity of exposure to Anopheles bites. Trans R Soc Trop Med Hyg 2012; 106:460-7. [PMID: 22721883 DOI: 10.1016/j.trstmh.2012.05.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Revised: 05/17/2012] [Accepted: 05/17/2012] [Indexed: 11/16/2022] Open
Abstract
Malaria immunity is modulated by many environmental and epidemiological factors. This study evaluates the influence of a hitherto unstudied environmental-epidemiological factor, namely the impact of human exposure to Anopheles bites on the isotype profile of acquired antibody responses to Plasmodium falciparum. In two Senegalese villages where the intensity of exposure to Anopheles bites was markedly different (high and low exposure), specific IgG1 and IgG3 responses to P. falciparum whole schizont extract (WSE) and circumsporozoite protein (CSP) were evaluated at the peak of Anopheles exposure (September) and later (December) in a cohort of 120 children aged 3-8 years. Multivariate analysis showed a significantly lower IgG1 response against P. falciparum WSE and CSP in children highly exposed to Anopheles bites (Gankette) compared to those who were weakly exposed (Mboula). In contrast, in both villages, parasitemia and increasing age were strongly associated with higher IgG1 and IgG3 levels. We hypothesize that high exposure to Anopheles bites could inhibit IgG1-dependent responsiveness to P. falciparum known to induce protective immune responses against malaria. The impact of mosquito saliva on the regulation of specific protective immunity may need to be taken into account in epidemiological studies and trials for malaria vaccines.
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Affiliation(s)
- Jean Biram Sarr
- Unité de recherche mixte MIVEGEC (IRD 224-CNRS 5290-UM1-UM2), Montpellier, France.
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16
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Sarr JB, Orlandi-Pradines E, Fortin S, Sow C, Cornelie S, Rogerie F, Guindo S, Konate L, Fusaï T, Riveau G, Rogier C, Remoue F. Assessment of exposure to Plasmodium falciparum transmission in a low endemicity area by using multiplex fluorescent microsphere-based serological assays. Parasit Vectors 2011; 4:212. [PMID: 22059951 PMCID: PMC3223141 DOI: 10.1186/1756-3305-4-212] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Accepted: 11/07/2011] [Indexed: 11/30/2022] Open
Abstract
Background The evaluation of malaria transmission intensity is a crucial indicator for estimating the burden of malarial disease. In this respect, entomological and parasitological methods present limitations, especially in low transmission areas. The present study used a sensitive multiplex assay to assess the exposure to Plasmodium falciparum infection in children living in an area of low endemicity. In three Senegalese villages, specific antibody (IgG) responses to 13 pre-erythrocytic P. falciparum peptides derived from Lsa1, Lsa3, Glurp, Salsa, Trap, Starp, Csp and Pf11.1 proteins were simultaneously evaluated before (June), at the peak (September) and after (December) the period of malaria transmission, in children aged from 1 to 8 years. Results Compared to other antigens, a high percentage of seropositivity and specific antibody levels were detected with Glurp, Salsa1, Lsa3NR2, and Lsa1J antigens. The seropositivity increased with age for all tested antigens. Specific IgG levels to Glurp, Salsa1, Lsa3NR2, and Lsa1J were significantly higher in P. falciparum infected children compared to non-infected and this increase is significantly correlated with parasite density. Conclusion The multiplex assay represents a useful technology for a serological assessment of rapid variations in malaria transmission intensity, especially in a context of low parasite rates. The use of such combined serological markers (i.e. Glurp, Lsa1, Lsa3, and Salsa) could offer the opportunity to examine these variations over time, and to evaluate the efficacy of integrated malaria control strategies.
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Boulanger D, Sarr JB, Fillol F, Sokhna C, Cisse B, Schacht AM, Trape JF, Riveau G, Simondon F, Greenwood B, Remoué F. Immunological consequences of intermittent preventive treatment against malaria in Senegalese preschool children. Malar J 2010; 9:363. [PMID: 21167018 PMCID: PMC3012051 DOI: 10.1186/1475-2875-9-363] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Accepted: 12/17/2010] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Intermittent preventive treatment in children (IPTc) is a promising strategy to control malaria morbidity. A significant concern is whether IPTc increases children's susceptibility to subsequent malaria infection by altering their anti-Plasmodium acquired immunity. METHODS To investigate this concern, IgG antibody (Ab) responses to Plasmodium falciparum schizont extract were measured in Senegalese children (6 months-5 years old) who had received three rounds of IPTc with artesunate + sulphadoxine-pyrimethamine (or placebo) at monthly intervals eight months earlier. Potential confounding factors, such as asexual malaria parasitaemia and nutritional status were also evaluated. RESULTS Firstly, a bivariate analysis showed that children who had received IPTc had lower anti-Plasmodium IgG Ab levels than the non-treated controls. When epidemiological parameters were incorporated into a multivariate regression, gender, nutritional status and haemoglobin concentration did not have any significant influence. In contrast, parasitaemia, past malaria morbidity and increasing age were strongly associated with a higher specific IgG response. CONCLUSIONS The intensity of the contacts with P. falciparum seems to represent the main factor influencing anti-schizont IgG responses. Previous IPTc does not seem to interfere with this parasite-dependent acquired humoral response eight months after the last drug administration.
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Affiliation(s)
- Denis Boulanger
- Unité Mixte de Recherche 145, Institut de Recherche pour le Développement and Université Montpellier 1, 911 avenue Agropolis, BP64501, 34394 Montpellier, France.
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Fillol F, Sarr JB, Boulanger D, Cisse B, Sokhna C, Riveau G, Simondon KB, Remoué F. Impact of child malnutrition on the specific anti-Plasmodium falciparum antibody response. Malar J 2009; 8:116. [PMID: 19490641 PMCID: PMC2700128 DOI: 10.1186/1475-2875-8-116] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2009] [Accepted: 06/02/2009] [Indexed: 11/18/2022] Open
Abstract
Background In sub-Saharan Africa, preschool children represent the population most vulnerable to malaria and malnutrition. It is widely recognized that malnutrition compromises the immune function, resulting in higher risk of infection. However, very few studies have investigated the relationship between malaria, malnutrition and specific immunity. In the present study, the anti-Plasmodium falciparum IgG antibody (Ab) response was evaluated in children according to the type of malnutrition. Methods Anthropometric assessment and blood sample collection were carried out during a cross-sectional survey including rural Senegalese preschool children. This cross-sectional survey was conducted in July 2003 at the onset of the rainy season. Malnutrition was defined as stunting (height-for-age <-2 z-scores) or wasting (weight-for-height <-2 z-scores). The analysis was performed on all malnourished children in July (n = 161, either stunted, n = 142 or wasted, n = 19), pair-matched to well-nourished controls. The IgG Ab response to P. falciparum whole extracts (schizont antigens) was assessed by ELISA in sera of the included children. Results Both the prevalence of anti-malarial immune responders and specific IgG Ab levels were significantly lower in malnourished children than in controls. Depending on the type of malnutrition, wasted children and stunted children presented a lower specific IgG Ab response than their respective controls, but this difference was significant only in stunted children (P = 0.026). This down-regulation of the specific Ab response seemed to be explained by severely stunted children (HAZ ≤ -2.5) compared to their controls (P = 0.03), while no significant difference was observed in mildly stunted children (-2.5 < HAZ <-2.0). The influence of child malnutrition on the specific anti-P. falciparum Ab response appeared to be independent of the intensity of infection. Conclusion Child malnutrition, and particularly stunting, may down-regulate the anti-P. falciparum Ab response, both in terms of prevalence of immune responders and specific IgG Ab levels. This study provides further evidence for the influence of malnutrition on the specific anti-malarial immune response and points to the importance of taking into account child malnutrition in malaria epidemiological studies and vaccine trials.
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Affiliation(s)
- Florie Fillol
- Institut de Recherche pour le Développement, Unité Mixte de Recherche 145, Montpellier, France.
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Kelly-Hope LA, McKenzie FE. The multiplicity of malaria transmission: a review of entomological inoculation rate measurements and methods across sub-Saharan Africa. Malar J 2009; 8:19. [PMID: 19166589 PMCID: PMC2656515 DOI: 10.1186/1475-2875-8-19] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Accepted: 01/23/2009] [Indexed: 11/21/2022] Open
Abstract
Plasmodium falciparum malaria is a serious tropical disease that causes more than one million deaths each year, most of them in Africa. It is transmitted by a range of Anopheles mosquitoes and the risk of disease varies greatly across the continent. The "entomological inoculation rate" is the commonly-used measure of the intensity of malaria transmission, yet the methods used are currently not standardized, nor do they take the ecological, demographic, and socioeconomic differences across populations into account. To better understand the multiplicity of malaria transmission, this study examines the distribution of transmission intensity across sub-Saharan Africa, reviews the range of methods used, and explores ecological parameters in selected locations. It builds on an extensive geo-referenced database and uses geographical information systems to highlight transmission patterns, knowledge gaps, trends and changes in methodologies over time, and key differences between land use, population density, climate, and the main mosquito species. The aim is to improve the methods of measuring malaria transmission, to help develop the way forward so that we can better assess the impact of the large-scale intervention programmes, and rapid demographic and environmental change taking place across Africa.
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Affiliation(s)
- Louise A Kelly-Hope
- Vector Group, Liverpool School of Tropical Medicine, Liverpool, UK
- Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, MD, USA
| | - F Ellis McKenzie
- Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, MD, USA
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Antibody-mediated growth inhibition of Plasmodium falciparum: relationship to age and protection from parasitemia in Kenyan children and adults. PLoS One 2008; 3:e3557. [PMID: 18958285 PMCID: PMC2570335 DOI: 10.1371/journal.pone.0003557] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2008] [Accepted: 10/09/2008] [Indexed: 12/01/2022] Open
Abstract
Background Antibodies that impair Plasmodium falciparum merozoite invasion and intraerythrocytic development are one of several mechanisms that mediate naturally acquired immunity to malaria. Attempts to correlate anti-malaria antibodies with risk of infection and morbidity have yielded inconsistent results. Growth inhibition assays (GIA) offer a convenient method to quantify functional antibody activity against blood stage malaria. Methods A treatment-time-to-infection study was conducted over 12-weeks in a malaria holoendemic area of Kenya. Plasma collected from healthy individuals (98 children and 99 adults) before artemether-lumefantrine treatment was tested by GIA in three separate laboratories. Results Median GIA levels varied with P. falciparum line (D10, 8.8%; 3D7, 34.9%; FVO, 51.4% inhibition). The magnitude of growth inhibition decreased with age in all P. falciparum lines tested with the highest median levels among children <4 years compared to adults (e.g. 3D7, 45.4% vs. 30.0% respectively, p = 0.0003). Time-to-infection measured by weekly blood smears was significantly associated with level of GIA controlling for age. Upper quartile inhibition activity was associated with less risk of infection compared to individuals with lower levels (e.g. 3D7, hazard ratio = 1.535, 95% CI = 1.012–2.329; p = 0.0438). Various GIA methodologies had little effect on measured parasite growth inhibition. Conclusion Plasma antibody-mediated growth inhibition of blood stage P. falciparum decreases with age in residents of a malaria holoendemic area. Growth inhibition assay may be a useful surrogate of protection against infection when outcome is controlled for age.
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