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Fogang B, Lellouche L, Ceesay S, Drammeh S, Jaiteh FK, Guery MA, Landier J, Haanappel CP, Froberg J, Conway D, D'Alessandro U, Bousema T, Claessens A. Asymptomatic Plasmodium falciparum carriage at the end of the dry season is associated with subsequent infection and clinical malaria in Eastern Gambia. Malar J 2024; 23:22. [PMID: 38229097 DOI: 10.1186/s12936-024-04836-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 01/03/2024] [Indexed: 01/18/2024] Open
Abstract
BACKGROUND Chronic carriage of asymptomatic low-density Plasmodium falciparum parasitaemia in the dry season may support maintenance of acquired immunity that protects against clinical malaria. However, the relationship between chronic low-density infections and subsequent risk of clinical malaria episodes remains unclear. METHODS In a 2-years study (December 2014 to December 2016) in eastern Gambia, nine cross-sectional surveys using molecular parasite detection were performed in the dry and wet season. During the 2016 malaria transmission season, passive case detection identified episodes of clinical malaria. RESULTS Among the 5256 samples collected, 444 (8.4%) were positive for P. falciparum. A multivariate model identified village of residence, male sex, age ≥ 5 years old, anaemia, and fever as independent factors associated with P. falciparum parasite carriage. Infections did not cluster over time within the same households or recurred among neighbouring households. Asymptomatic parasite carriage at the end of dry season was associated with a higher risk of infection (Hazard Ratio, HR = 3.0, p < 0.0001) and clinical malaria (HR = 1.561, p = 0.057) during the following transmission season. Age and village of residence were additional predictors of infection and clinical malaria during the transmission season. CONCLUSION Chronic parasite carriage during the dry season is associated with an increased risk of malaria infection and clinical malaria. It is unclear whether this is due to environmental exposure or to other factors.
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Affiliation(s)
- Balotin Fogang
- LPHI, MIVEGEC, CNRS, INSERM, University of Montpellier, Montpellier, France
| | - Lionel Lellouche
- LPHI, MIVEGEC, CNRS, INSERM, University of Montpellier, Montpellier, France
| | - Sukai Ceesay
- Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Sainabou Drammeh
- Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Fatou K Jaiteh
- Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Marc-Antoine Guery
- LPHI, MIVEGEC, CNRS, INSERM, University of Montpellier, Montpellier, France
| | - Jordi Landier
- IRD, INSERM, SESSTIM, ISSPAM, Aix Marseille University, 27 Boulevard Jean Moulin, 13005, Marseille, France
| | - Cynthia P Haanappel
- Department of Medical Microbiology, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Janeri Froberg
- Department of Medical Microbiology, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - David Conway
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, UK
| | - Umberto D'Alessandro
- Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Teun Bousema
- Department of Medical Microbiology, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Antoine Claessens
- LPHI, MIVEGEC, CNRS, INSERM, University of Montpellier, Montpellier, France.
- Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine, Banjul, The Gambia.
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2
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Ahmad A, Mohammed NI, Joof F, Affara M, Jawara M, Abubakar I, Okebe J, Ceesay S, Hamid-Adiamoh M, Bradley J, Amambua-Ngwa A, Nwakanma D, D'Alessandro U. Asymptomatic Plasmodium falciparum carriage and clinical disease: a 5-year community-based longitudinal study in The Gambia. Malar J 2023; 22:82. [PMID: 36882754 PMCID: PMC9993664 DOI: 10.1186/s12936-023-04519-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 02/28/2023] [Indexed: 03/09/2023] Open
Abstract
BACKGROUND Carriers of persistent asymptomatic Plasmodium falciparum infections constitute an infectious reservoir that maintains malaria transmission. Understanding the extent of carriage and characteristics of carriers specific to endemic areas could guide use of interventions to reduce infectious reservoir. METHODS In eastern Gambia, an all-age cohort from four villages was followed up from 2012 to 2016. Each year, cross-sectional surveys were conducted at the end of the malaria transmission season (January) and just before the start of the next one (June) to determine asymptomatic P. falciparum carriage. Passive case detection was conducted during each transmission season (August to January) to determine incidence of clinical malaria. Association between carriage at the end of the season and at start of the next one and the risk factors for this were assessed. Effect of carriage before start of the season on risk of clinical malaria during the season was also examined. RESULTS A total of 1403 individuals-1154 from a semi-urban village and 249 from three rural villages were enrolled; median age was 12 years (interquartile range [IQR] 6, 30) and 12 years (IQR 7, 27) respectively. In adjusted analysis, asymptomatic P. falciparum carriage at the end of a transmission season and carriage just before start of the next one were strongly associated (adjusted odds ratio [aOR] = 19.99; 95% CI 12.57-31.77, p < 0.001). The odds of persistent carriage (i.e. infected both in January and in June) were higher in rural villages (aOR = 13.0; 95% CI 6.33-26.88, p < 0.001) and in children aged 5-15 years (aOR = 5.03; 95% CI 2.47-10.23, p = < 0.001). In the rural villages, carriage before start of the season was associated with a lower risk of clinical malaria during the season (incidence risk ratio [IRR] 0.48, 95% CI 0.27-0.81, p = 0.007). CONCLUSIONS Asymptomatic P. falciparum carriage at the end of a transmission season strongly predicted carriage just before start of the next one. Interventions that clear persistent asymptomatic infections when targeted at the subpopulation with high risk of carriage may reduce the infectious reservoir responsible for launching seasonal transmission.
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Affiliation(s)
- Abdullahi Ahmad
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia.
- Global Health Institute, University of Antwerp, Gouverneur Kinsbergencentrum, Campus Drie Eiken, Doornstraat 331, 2610, Wilrijk, Belgium.
| | - Nuredin Ibrahim Mohammed
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
| | - Fatou Joof
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
| | - Muna Affara
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
| | - Musa Jawara
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
| | - Ismaela Abubakar
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
| | - Joseph Okebe
- International Public Health Department, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Serign Ceesay
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
| | - Majidah Hamid-Adiamoh
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
| | - John Bradley
- MRC International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - Alfred Amambua-Ngwa
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
| | - Davis Nwakanma
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia.
| | - Umberto D'Alessandro
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
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3
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Kyei-Baafour E, Oppong M, Kusi KA, Frempong AF, Aculley B, Arthur FKN, Tiendrebeogo RW, Singh SK, Theisen M, Kweku M, Adu B, Hviid L, Ofori MF. Suitability of IgG responses to multiple Plasmodium falciparum antigens as markers of transmission intensity and pattern. PLoS One 2021; 16:e0249936. [PMID: 33886601 PMCID: PMC8062017 DOI: 10.1371/journal.pone.0249936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 03/27/2021] [Indexed: 12/05/2022] Open
Abstract
Detection of antibody reactivity to appropriate, specific parasite antigens may constitute a sensitive and cost-effective alternative to current tools to monitor malaria transmission across different endemicity settings. This study aimed to determine the suitability of IgG responses to a number of P. falciparum antigens as markers of transmission intensity and pattern. Antibody responses to multiple malaria antigens were determined in 905 participants aged 1–12 years from three districts with low (Keta), medium (Hohoe) and high (Krachi) transmission intensity in the Volta region of Ghana. Blood film microscopy slides and dry blood spots (DBS) were obtained for parasitaemia detection and antibody measurement, respectively. Sera were eluted from DBS and levels of IgG specific for 10 malaria antigens determined by a multiplex assay. Results were compared within and among the districts. Total IgG responses to MSPDBL1, MSPDBLLeucine, MSP2-FC27, RAMA, and PfRh2a and PfRh2b were higher in Krachi than in Hohoe and Keta. Seroprevalence of IgG specific for MSPDBLLeucine, RON4, and PfRh2b were also highest in Krachi. Responses to RALP-1, PfRh2a and PfRh2b were associated with patent but asymptomatic parasitaemia in Keta, while responses to MSPDBL1, MSPDBLLeucine, MSP2-FC27, RAMA, Rh2-2030, and PfRh2b were associated with parasite carriage in Hohoe, but not in Krachi. Using ROC analysis, only PfRh2b was found to predict patent, but asymptomatic, parasitaemia in Keta and Hohoe. Antibody breadth correlated positively with age (r = 0.29, p<0.0001) and parasitaemia (β = 3.91; CI = 1.53 to 6.29), and medium to high transmission (p<0.0001). Our findings suggest differences in malaria-specific antibody responses across the three transmission zones and that PfRh2b has potential as a marker of malaria transmission intensity and pattern. This could have implications for malaria control programs and vaccine trials.
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Affiliation(s)
- Eric Kyei-Baafour
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana
- Department of Biochemistry and Biotechnology, College of Science, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | - Mavis Oppong
- Department of Epidemiology and Biostatistics, School of Public Health, University of Health and Allied Sciences, Hohoe, Ghana
| | - Kwadwo Asamoah Kusi
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Abena Fremaah Frempong
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Belinda Aculley
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Fareed K. N. Arthur
- Department of Biochemistry and Biotechnology, College of Science, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | - Regis Wendpayangde Tiendrebeogo
- Centre for Medical Parasitology at Department of Immunology and Microbiology, University of Copenhagen, and at Department of Infectious Diseases, Rigshospitalet, Copenhagen, Denmark
| | - Susheel K. Singh
- Centre for Medical Parasitology at Department of Immunology and Microbiology, University of Copenhagen, and at Department of Infectious Diseases, Rigshospitalet, Copenhagen, Denmark
- Department for Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark
| | - Michael Theisen
- Centre for Medical Parasitology at Department of Immunology and Microbiology, University of Copenhagen, and at Department of Infectious Diseases, Rigshospitalet, Copenhagen, Denmark
- Department for Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark
| | - Margaret Kweku
- Department of Epidemiology and Biostatistics, School of Public Health, University of Health and Allied Sciences, Hohoe, Ghana
| | - Bright Adu
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Lars Hviid
- Centre for Medical Parasitology at Department of Immunology and Microbiology, University of Copenhagen, and at Department of Infectious Diseases, Rigshospitalet, Copenhagen, Denmark
| | - Michael Fokuo Ofori
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana
- * E-mail:
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4
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Ofori MF, Kploanyi EE, Mensah BA, Dickson EK, Kyei-Baafour E, Gyabaa S, Tetteh M, Koram KA, Abuaku BK, Ghansah A. Ex vivo Sensitivity Profile of Plasmodium falciparum Clinical Isolates to a Panel of Antimalarial Drugs in Ghana 13 Years After National Policy Change. Infect Drug Resist 2021; 14:267-276. [PMID: 33536768 PMCID: PMC7850388 DOI: 10.2147/idr.s295277] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 01/09/2021] [Indexed: 11/26/2022] Open
Abstract
PURPOSE Malaria continues to be a major health issue globally with almost 85% of the global burden and deaths borne by sub-Saharan Africa and India. Although the current artemisinin derived combination therapies in Ghana are still efficacious against the Plasmodium falciparum (Pf) parasite, compounding evidence of artemisinin and amodiaquine resistance establish the need for a full, up-to-date understanding and monitoring of antimalarial resistance to provide evidence for planning control strategies. MATERIALS AND METHODS The study was cross-sectional and was conducted during the peak malaria transmission seasons of 2015, 2016, and 2017 in two ecological zones of Ghana. Study participants included children aged 6 months to 14 years. Using ex vivo 4,6-diamidino-2-phenylindole (DAPI) drug sensitivity assay, 330 Pf isolates were used to investigate susceptibility to five antimalarial drugs: chloroquine (CQ), amodiaquine (AMD) dihydroartemisinin (DHA), artesunate (ART) and mefloquine (MFQ). RESULTS The pooled geometric mean IC50S (GMIC50) of the five drugs against the parasites from Cape Coast and Begoro were 15.5, 42.4, 18.9, 4.6 and 27.3nM for CQ, AMD, DHA, ART, and MFQ, respectively. The GMIC50 values for CQ (p<0.001), ART (p<0.011) and DHA (p<0.018) were significantly higher for Cape Coast isolates as compared to Begoro isolates. However, GMIC50 estimates for MFQ (p<0.022) were significantly higher for Begoro isolates. Positive correlations were found between each pair of drugs with the weakest found between MFQ and DHA (r = 0.34;p<0.001), and the strongest between ART and DHA (r =0.66; p<0.001). CONCLUSION The parasites showed reduced sensitivities to three (AMD, DHA and MFQ) out of the five drugs assessed. The study also demonstrated the continual return of chloroquine-sensitive parasites after 13 years of its withdrawal as the first-line drug for the treatment of uncomplicated malaria in Ghana. The ex vivo DAPI assay is a reliable method for assessing antimalarial drug sensitivities of Pf field isolates under field settings.
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Affiliation(s)
- Michael Fokuo Ofori
- Immunology Department, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Accra, Ghana
| | - Emma E Kploanyi
- Immunology Department, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Accra, Ghana
| | - Benedicta A Mensah
- Epidemiology Department, Noguchi Memorial Institute for Medical Research,University of Ghana, Legon, Accra, Ghana
| | - Emmanuel K Dickson
- Immunology Department, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Accra, Ghana
| | - Eric Kyei-Baafour
- Immunology Department, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Accra, Ghana
| | - Sampson Gyabaa
- Ewim Polyclinic, Ghana Health Service, Cape Coast, Ghana
| | - Mary Tetteh
- Begoro District Hospital, Ghana Health Service, Begoro, Ghana
| | - Kwadwo A Koram
- Epidemiology Department, Noguchi Memorial Institute for Medical Research,University of Ghana, Legon, Accra, Ghana
| | - Benjamin K Abuaku
- Epidemiology Department, Noguchi Memorial Institute for Medical Research,University of Ghana, Legon, Accra, Ghana
| | - Anita Ghansah
- Immunology Department, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Accra, Ghana
- Parasitology Department, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Accra, Ghana
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5
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Eldh M, Hammar U, Arnot D, Beck HP, Garcia A, Liljander A, Mercereau-Puijalon O, Migot-Nabias F, Mueller I, Ntoumi F, Ross A, Smith T, Sondén K, Vafa Homann M, Yman V, Felger I, Färnert A. Multiplicity of Asymptomatic Plasmodium falciparum Infections and Risk of Clinical Malaria: A Systematic Review and Pooled Analysis of Individual Participant Data. J Infect Dis 2020; 221:775-785. [PMID: 31585009 PMCID: PMC7026891 DOI: 10.1093/infdis/jiz510] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 10/01/2019] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND The malaria parasite Plasmodium falciparum holds an extensive genetic polymorphism. In this pooled analysis, we investigate how the multiplicity in asymptomatic P. falciparum infections-that is, the number of coinfecting clones-affects the subsequent risk of clinical malaria in populations living under different levels of transmission. METHODS A systematic search of the literature was performed to identify studies in which P. falciparum infections were genotyped in asymptomatic individuals who were followed up prospectively regarding the incidence of clinical malaria. Individual participant data were pooled from 15 studies (n = 3736 individuals). RESULTS Multiclonal asymptomatic infections were associated with a somewhat increased subsequent risk of clinical malaria in the youngest children, followed by an initial declining risk with age irrespective of transmission intensity. At approximately 5 years of age, the risk continued the gradual decline with age in high-transmission settings. However, in older children in moderate-, low-, and seasonal-transmission settings, multiclonal infections were either not significantly associated with the risk of subsequent febrile malaria or were associated with an increased risk. CONCLUSIONS The number of clones in asymptomatic P. falciparum infections is associated with different risks of subsequent clinical malaria depending on age and transmission intensity.
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Affiliation(s)
- Martina Eldh
- Division of Infectious Diseases, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
| | - Ulf Hammar
- Unit of Biostatistics, Department of Epidemiology, Institute for Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - David Arnot
- Zhejiang-Edinburgh Institute, Zhejiang University Medical School, International Campus of Zhejiang University, Haining, People's Republic of China
| | - Hans-Peter Beck
- Molecular Diagnostics, Medical Parasitology and Infection Biology, Swiss Tropical Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - André Garcia
- MERIT, IRD, Université Paris 5, Sorbonne Paris Cité, Paris, France.,Cerpage, Cotonou, Bénin
| | - Anne Liljander
- International Livestock Research Institute, Nairobi, Kenya
| | | | | | - Ivo Mueller
- Institut Pasteur, Parasites and Insect Vectors Department, Paris, France
| | - Francine Ntoumi
- Fondation Congolaise pour la Recherche Médicale and Faculty of Sciences and Technology University Marien Ngouabi Brazzaville, Republic of Congo.,Institute for Tropical Medicine, University of Tübingen, Tübingen, Germany
| | - Amanda Ross
- University of Basel, Basel, Switzerland.,Department of Epidemiology and Public Health, Swiss Tropical Institute, Basel, Switzerland
| | - Thomas Smith
- University of Basel, Basel, Switzerland.,Department of Epidemiology and Public Health, Swiss Tropical Institute, Basel, Switzerland
| | - Klara Sondén
- Division of Infectious Diseases, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden.,Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden
| | - Manijeh Vafa Homann
- Division of Infectious Diseases, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
| | - Victor Yman
- Division of Infectious Diseases, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
| | - Ingrid Felger
- Molecular Diagnostics, Medical Parasitology and Infection Biology, Swiss Tropical Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Anna Färnert
- Division of Infectious Diseases, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden.,Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden
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6
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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] [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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7
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Amoah LE, Nuvor SV, Obboh EK, Acquah FK, Asare K, Singh SK, Boampong JN, Theisen M, Williamson KC. Natural antibody responses to Plasmodium falciparum MSP3 and GLURP(R0) antigens are associated with low parasite densities in malaria patients living in the Central Region of Ghana. Parasit Vectors 2017; 10:395. [PMID: 28835262 PMCID: PMC5569498 DOI: 10.1186/s13071-017-2338-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 08/16/2017] [Indexed: 12/20/2022] Open
Abstract
Background Plasmodium falciparum genetic diversity and multiplicity of infection (MOI) are parasite features that have been suggested to influence the acquisition of protective immunity against malaria. This study sought to assess the relationship between MOI and parasite density (PD) in malaria patients living in the Central Region of Ghana and to determine whether naturally occurring antibody levels against P. falciparum GLURP (PF3D7_1035300) and MSP3 (PF3D7_1035400) antigens are associated with decreased parasite load. Methods Dried filter paper blood blots were obtained from children and adults diagnosed with uncomplicated P. falciparum malaria. Microscopy was used to estimate P. falciparum parasite density and polymerase chain reaction (PCR) amplification of the polymorphic regions of msp1 (PF3D7_0930300) and msp2 (PF3D7_0206800) was used for parasite genotyping and MOI determination. ELISA was used to measure the serum IgG concentration of R0 fragment of GLURP (GLURP(R0)) and MSP3 antibodies. Results All 115 samples were positive for P. falciparum by PCR using either the msp1 or msp2 genotyping primer sets. The most prevalent msp1 and msp2 alleles were KI and 3D7, respectively. The geometric mean (GM) for MOI determined by both msp1 and msp2 genotyping was 1.3 for the entire population and was generally higher in children than in adults. Seropositivity was estimated at 67 and 63% for GLURP(R0) and MSP3 antibodies, respectively, and antibody titers were negatively correlated with parasite density. Conclusions The negative correlation between naturally occurring GLURP(R0) and MSP3 antibody levels and parasite density observed in this study suggest that augmenting the antibody response with the GMZ2 vaccine could enhance protection in the Central Region of Ghana. Electronic supplementary material The online version of this article (doi:10.1186/s13071-017-2338-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- L E Amoah
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana.
| | - S V Nuvor
- Department of Microbiology and Immunology, School of Medical Sciences, University of Cape Coast, Cape Coast, Ghana
| | - E K Obboh
- School of Medical Sciences University of Cape Coast, Cape Coast, Ghana
| | - F K Acquah
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
| | - K Asare
- Department of Biomedical Sciences University of Cape Coast, Cape Coast, Ghana
| | - S K Singh
- Department for Congenital disorders, Statens Serum Institut, Copenhagen, Denmark.,Centre for Medical Parasitology, Department of International Health, Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark.,Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - J N Boampong
- Department of Biomedical Sciences University of Cape Coast, Cape Coast, Ghana
| | - M Theisen
- Department for Congenital disorders, Statens Serum Institut, Copenhagen, Denmark.,Centre for Medical Parasitology, Department of International Health, Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark.,Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - K C Williamson
- Loyola University Chicago, Chicago, IL, USA.,Uniform Services University of the Health Sciences, Bethesda, MD, USA
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Offeddu V, Olotu A, Osier F, Marsh K, Matuschewski K, Thathy V. High Sporozoite Antibody Titers in Conjunction with Microscopically Detectable Blood Infection Display Signatures of Protection from Clinical Malaria. Front Immunol 2017; 8:488. [PMID: 28533773 PMCID: PMC5421148 DOI: 10.3389/fimmu.2017.00488] [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: 01/08/2017] [Accepted: 04/07/2017] [Indexed: 11/18/2022] Open
Abstract
Immunoepidemiological studies typically reveal slow, age-dependent acquisition of immune responses against Plasmodium falciparum sporozoites. Naturally acquired immunity against preerythrocytic stages is considered inadequate to confer protection against clinical malaria. To explore previously unrecognized antisporozoite responses, we measured serum levels of naturally acquired antibodies to whole Plasmodium falciparum sporozoites (Pfspz) and the immunodominant (NANP)5 repeats of the major sporozoite surface protein, circumsporozoite protein, in a well-characterized Kenyan cohort. Sera were sampled at the start of the malaria transmission season, and all subjects were prospectively monitored for uncomplicated clinical malaria in the ensuing 6 months. We used Kaplan–Meier analysis and multivariable regression to investigate the association of antisporozoite immunity with incidence of clinical malaria. Although naturally acquired humoral responses against Pfspz and (NANP)5 were strongly correlated (p < 0.0001), 37% of Pfspz responders did not recognize (NANP)5. The prevalence and magnitude of antisporozoite responses increased with age, although some high Pfspz responders were identified among children. Survival analysis revealed a reduced risk of and increased time to first or only episode of clinical malaria among Pfspz or (NANP)5 responders carrying microscopically detectable Plasmodium falciparum (Pf) parasitemia at the start of the transmission season (p < 0.03). Our Cox regression interaction models indicated a potentially protective interaction between high anti-Pfspz (p = 0.002) or anti-(NANP)5 (p = 0.001) antibody levels and microscopically detectable Pf parasitemia on the risk of subsequent clinical malaria. Our findings indicate that robust antisporozoite immune responses can be naturally acquired already at an early age. A potentially protective role of high levels of anti-Pfspz antibodies against clinical episodes of uncomplicated malaria was detected, suggesting that antibody-mediated preerythrocytic immunity might indeed contribute to protection in nature.
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Affiliation(s)
- Vittoria Offeddu
- Parasitology Unit, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Ally Olotu
- Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kenya Medical Research Institute (KEMRI), Kilifi, Kenya
| | - Faith Osier
- Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kenya Medical Research Institute (KEMRI), Kilifi, Kenya
| | - Kevin Marsh
- Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kenya Medical Research Institute (KEMRI), Kilifi, Kenya.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Kai Matuschewski
- Parasitology Unit, Max Planck Institute for Infection Biology, Berlin, Germany.,Molecular Parasitology, Institute of Biology, Humboldt University, Berlin, Germany
| | - Vandana Thathy
- Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kenya Medical Research Institute (KEMRI), Kilifi, Kenya
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Adomako-Ankomah Y, Chenoweth MS, Durfee K, Doumbia S, Konate D, Doumbouya M, Keita AS, Nikolaeva D, Tullo GS, Anderson JM, Fairhurst RM, Daniels R, Volkman SK, Diakite M, Miura K, Long CA. High Plasmodium falciparum longitudinal prevalence is associated with high multiclonality and reduced clinical malaria risk in a seasonal transmission area of Mali. PLoS One 2017; 12:e0170948. [PMID: 28158202 PMCID: PMC5291380 DOI: 10.1371/journal.pone.0170948] [Citation(s) in RCA: 6] [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: 11/21/2016] [Accepted: 01/12/2017] [Indexed: 11/19/2022] Open
Abstract
The effects of persistent Plasmodium falciparum (Pf) infection and multiclonality on subsequent risk of clinical malaria have been reported, but the relationship between these 2 parameters and their relative impacts on the clinical outcome of infection are not understood. A longitudinal cohort study was conducted in a seasonal and high-transmission area of Mali, in which 500 subjects aged 1-65 years were followed for 1 year. Blood samples were collected every 2 weeks, and incident malaria cases were diagnosed and treated. Pf infection in each individual at each time point was assessed by species-specific nested-PCR, and Pf longitudinal prevalence per person (PfLP, proportion of Pf-positive samples over 1 year) was calculated. Multiclonality of Pf infection was measured using a 24-SNP DNA barcoding assay at 4 time-points (two in wet season, and two in dry season) over one year. PfLP was positively correlated with multiclonality at each time point (all r≥0.36; all P≤0.011). When host factors (e.g., age, gender), PfLP, and multiclonality (at the beginning of the transmission season) were analyzed together, only increasing age and high PfLP were associated with reduced clinical malaria occurrence or reduced number of malaria episodes (for both outcomes, P<0.001 for age, and P = 0.005 for PfLP). When age, PfLP and baseline Pf positivity were analyzed together, the effect of high PfLP remained significant even after adjusting for the other two factors (P = 0.001 for malaria occurrence and P<0.001 for number of episodes). In addition to host age and baseline Pf positivity, both of which have been reported as important modifiers of clinical malaria risk, our results demonstrate that persistent parasite carriage, but not baseline multiclonality, is associated with reduced risk of clinical disease in this population. Our study emphasizes the importance of considering repeated parasite exposure in future studies that evaluate clinical malaria risk.
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Affiliation(s)
- Yaw Adomako-Ankomah
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Matthew S. Chenoweth
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Katelyn Durfee
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
| | - Saibou Doumbia
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy, and Odontostomatology, University of Sciences, Techniques, and Technologies of Bamako, Bamako, Mali
| | - Drissa Konate
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy, and Odontostomatology, University of Sciences, Techniques, and Technologies of Bamako, Bamako, Mali
| | - Mory Doumbouya
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy, and Odontostomatology, University of Sciences, Techniques, and Technologies of Bamako, Bamako, Mali
| | - Abdoul S. Keita
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy, and Odontostomatology, University of Sciences, Techniques, and Technologies of Bamako, Bamako, Mali
| | - Daria Nikolaeva
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Gregory S. Tullo
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Jennifer M. Anderson
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Rick M. Fairhurst
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Rachel Daniels
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America
- Infectious Disease Program, The Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Sarah K. Volkman
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
- Infectious Disease Program, The Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
- School of Nursing and Health Sciences, Simmons College, Boston, Massachusetts, United States of America
| | - Mahamadou Diakite
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy, and Odontostomatology, University of Sciences, Techniques, and Technologies of Bamako, Bamako, Mali
| | - Kazutoyo Miura
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
- * E-mail:
| | - Carole A. Long
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
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Plasmodium falciparum msp2 Genotypes and Multiplicity of Infections among Children under Five Years with Uncomplicated Malaria in Kibaha, Tanzania. J Parasitol Res 2015; 2015:721201. [PMID: 26770821 PMCID: PMC4684896 DOI: 10.1155/2015/721201] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 11/17/2015] [Accepted: 11/19/2015] [Indexed: 11/19/2022] Open
Abstract
Genetic diversity of Plasmodium falciparum may pose challenges in malaria treatment and prevention through chemotherapy and vaccination. We assessed Plasmodium falciparum genetic diversity and multiplicity of infection (MOI) of P. falciparum infections and sort relationship of parasitaemia with P. falciparum msp2 genotypes as well as with the number of infecting clones. The study was carried out in Kibaha, Tanzania. Ninety-nine children under five years with uncomplicated malaria were recruited. Genetic diversity was analyzed by genotyping the msp2 gene using PCR-Restriction Fragment Length Polymorphism. Thirty-two different msp2 alleles were obtained. The msp2 3D7 allelic frequency was higher (48.1%) and more prevalent than FC27 (27.3%) (p < 0.05). Twenty-four percent of the infections were mixed alleles. The individuals with FC27 had high parasitemia compared to those with 3D7 alleles (p = 0.038). The mean MOI was low (1.4 clones, 95% CI 1.2–1.5). The P. falciparum population among children at Kibaha is composed of distinct P. falciparum clones, and parasites having 3D7 are more frequent than those with FC27 alleles. Individuals with parasite having FC27 alleles have high parasite densities suggesting that parasites with FC27 alleles may associate with severity of disease in Kibaha. Low MOI at Kibaha suggests low malaria transmission rate.
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11
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Sondén K, Doumbo S, Hammar U, Vafa Homann M, Ongoiba A, Traoré B, Bottai M, Crompton PD, Färnert A. Asymptomatic Multiclonal Plasmodium falciparum Infections Carried Through the Dry Season Predict Protection Against Subsequent Clinical Malaria. J Infect Dis 2015; 212:608-16. [PMID: 25712968 DOI: 10.1093/infdis/jiv088] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 02/06/2015] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Immunity to the antigenically diverse parasite Plasmodium falciparum is acquired gradually after repeated exposure. Studies in areas of high malaria transmission have shown that asymptomatic individuals infected with multiclonal infections are at reduced risk of febrile malaria during follow-up. METHODS We assessed the relationship between the genetic diversity of clones in P. falciparum infections that persist through the dry season and the subsequent risk of febrile malaria in 225 individuals aged 2-25 years in Mali, where the 6-month malaria and dry seasons are sharply demarcated. Polymerase chain reaction-based genotyping of the highly polymorphic merozoite surface protein 2 gene was performed on blood samples collected at 5 cross-sectional surveys. RESULTS In an age-adjusted analysis, individuals with multiclonal P. falciparum infections before the rainy season were at reduced risk of febrile malaria, compared with individuals who were uninfected (hazard ratio [HR], 0.28; 95% confidence interval [CI], .11-.69). In contrast, there was no significant association between risk of malaria and having 1 clone at baseline (HR, 0.71; 95% CI, .36-1.40). CONCLUSIONS The results suggest that persistent multiclonal infections carried through the dry season contribute to protection against subsequent febrile malaria, possibly by maintaining protective immune responses that depend on ongoing parasite infection.
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Affiliation(s)
- Klara Sondén
- Unit of Infectious Diseases, Department of Medicine Solna
| | - Safiatou Doumbo
- Mali International Center of Excellence in Research, University of Sciences, Technique, and Technology of Bamako
| | - Ulf Hammar
- Unit of Biostatistics, Department of Epidemiology, Institute for Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | | | - Aissata Ongoiba
- Unit of Biostatistics, Department of Epidemiology, Institute for Environmental Medicine, Karolinska Institutet, Stockholm, Sweden Mali International Center of Excellence in Research, University of Sciences, Technique, and Technology of Bamako
| | - Boubacar Traoré
- Mali International Center of Excellence in Research, University of Sciences, Technique, and Technology of Bamako
| | - Matteo Bottai
- Unit of Biostatistics, Department of Epidemiology, Institute for Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Peter D Crompton
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland
| | - Anna Färnert
- Unit of Infectious Diseases, Department of Medicine Solna
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12
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Lindblade KA, Steinhardt L, Samuels A, Kachur SP, Slutsker L. The silent threat: asymptomatic parasitemia and malaria transmission. Expert Rev Anti Infect Ther 2014; 11:623-39. [PMID: 23750733 DOI: 10.1586/eri.13.45] [Citation(s) in RCA: 338] [Impact Index Per Article: 33.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Scale-up of malaria control interventions has resulted in a substantial decline in global malaria morbidity and mortality. Despite this achievement, there is evidence that current interventions alone will not lead to malaria elimination in most malaria-endemic areas and additional strategies need to be considered. Use of antimalarial drugs to target the reservoir of malaria infection is an option to reduce the transmission of malaria between humans and mosquito vectors. However, a large proportion of human malaria infections are asymptomatic, requiring treatment that is not triggered by care-seeking for clinical illness. This article reviews the evidence that asymptomatic malaria infection plays an important role in malaria transmission and that interventions to target this parasite reservoir may be needed to achieve malaria elimination in both low- and high-transmission areas.
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Affiliation(s)
- Kim A Lindblade
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, 1600 Clifton Rd. NE, MS A-06, Atlanta, GA 30333, USA.
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13
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Hammami I, Garcia A, Nuel G. Evidence for overdispersion in the distribution of malaria parasites and leukocytes in thick blood smears. Malar J 2013; 12:398. [PMID: 24195469 PMCID: PMC3831262 DOI: 10.1186/1475-2875-12-398] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 10/22/2013] [Indexed: 11/24/2022] Open
Abstract
Background Microscopic examination of stained thick blood smears (TBS) is the gold standard for routine malaria diagnosis. Parasites and leukocytes are counted in a predetermined number of high power fields (HPFs). Data on parasite and leukocyte counts per HPF are of broad scientific value. However, in published studies, most of the information on parasite density (PD) is presented as summary statistics (e.g. PD per microlitre, prevalence, absolute/assumed white blood cell counts), but original data sets are not readily available. Besides, the number of parasites and the number of leukocytes per HPF are assumed to be Poisson-distributed. However, count data rarely fit the restrictive assumptions of the Poisson distribution. The violation of these assumptions commonly results in overdispersion. The objectives of this paper are to investigate and handle overdispersion in field-collected data. Methods The data comprise the records of three TBSs of 12-month-old children from a field study of Plasmodium falciparum malaria in Tori Bossito, Benin. All HPFs were examined systemically by visually scanning the film horizontally from edge to edge. The numbers of parasites and leukocytes per HPF were recorded and formed the first dataset on parasite and leukocyte counts per HPF. The full dataset is published in this study. Two sources of overdispersion in data are investigated: latent heterogeneity and spatial dependence. Unobserved heterogeneity in data is accounted for by considering more flexible models that allow for overdispersion. Of particular interest were the negative binomial model (NB) and mixture models. The dependent structure in data was modelled with hidden Markov models (HMMs). Results The Poisson assumptions are inconsistent with parasite and leukocyte distributions per HPF. Among simple parametric models, the NB model is the closest to the unknown distribution that generates the data. On the basis of model selection criteria AIC and BIC, HMMs provided a better fit to data than mixtures. Ordinary pseudo-residuals confirmed the validity of HMMs. Conclusion Failure to take overdispersion into account in parasite and leukocyte counts may entail important misleading inferences when these data are related to other explanatory variables (malariometric or environmental). Its detection is therefore essential. In addition, an alternative PD estimation method that accounts for heterogeneity and spatial dependence should be seriously considered in epidemiological studies with field-collected parasite and leukocyte data.
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Affiliation(s)
- Imen Hammami
- , Laboratoire de Mathématiques Appliquées (MAP5) UMR CNRS 8145Université Paris Descartes, Paris, France.
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14
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Rono J, Osier FHA, Olsson D, Montgomery S, Mhoja L, Rooth I, Marsh K, Färnert A. Breadth of anti-merozoite antibody responses is associated with the genetic diversity of asymptomatic Plasmodium falciparum infections and protection against clinical malaria. Clin Infect Dis 2013; 57:1409-16. [PMID: 23983244 DOI: 10.1093/cid/cit556] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Elucidating the mechanisms of naturally acquired immunity to Plasmodium falciparum infections would be highly valuable for malaria vaccine development. Asymptomatic multiclonal infections have been shown to predict protection from clinical malaria in a transmission-dependent manner, but the mechanisms underlying this are unclear. We assessed the breadth of antibody responses to several vaccine candidate merozoite antigens in relation to the infecting parasite population and clinical immunity. METHODS In a cohort study in Tanzania, 320 children aged 1-16 years who were asymptomatic at baseline were included. We genotyped P. falciparum infections by targeting the msp2 gene using polymerase chain reaction and capillary electrophoresis and measured antibodies to 7 merozoite antigens using a multiplex assay. We assessed the correlation between the number of clones and the breadth of the antibody response, and examined their effects on the risk of malaria during 40 weeks of follow-up using age-adjusted multivariate regression models. RESULTS The antibody breadth was positively correlated with the number of clones (RR [risk ratio], 1.63; 95% confidence interval [CI], 1.32-2.02). Multiclonal infections were associated with a nonsignificant reduction in the risk of malaria in the absence of antibodies (RR, 0.83; 95% CI, .29-2.34). The breadth of the antibody response was significantly associated with a reduced risk of malaria in the absence of infections (RR, 0.25; 95% CI, .09-.66). In combination, these factors were associated with a lower risk of malaria than they were individually (RR, 0.14; 95% CI, .04-.48). CONCLUSIONS These data suggest that malaria vaccines mimicking naturally acquired immunity should ideally induce antibody responses that can be boosted by natural infections.
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Affiliation(s)
- Josea Rono
- Infectious Diseases Unit, Department of Medicine, Solna, Karolinska Institutet, Stockholm, Sweden
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15
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Acquired antibodies to merozoite antigens in children from Uganda with uncomplicated or severe Plasmodium falciparum malaria. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2013; 20:1170-80. [PMID: 23740926 DOI: 10.1128/cvi.00156-13] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Malaria can present itself as an uncomplicated or severe disease. We have here studied the quantity and quality of antibody responses against merozoite antigens, as well as multiplicity of infection (MOI), in children from Uganda. We found higher levels of IgG antibodies toward erythrocyte-binding antigen EBA181, MSP2 of Plasmodium falciparum 3D7 and FC27 (MSP2-3D7/FC27), and apical membrane antigen 1 (AMA1) in patients with uncomplicated malaria by enzyme-linked immunosorbent assay (ELISA) but no differences against EBA140, EBA175, MSP1, and reticulocyte-binding protein homologues Rh2 and Rh4 or for IgM against MSP2-3D7/FC27.Patients with uncomplicated malaria were also shown to have higher antibody affinities for AMA1 by surface plasmon resonance (SPR). Decreased invasion of two clinical P. falciparum isolates in the presence of patient plasma correlated with lower initial parasitemia in the patients, in contrast to comparisons of parasitemia to ELISA values or antibody affinities, which did not show any correlations. Analysis of the heterogeneity of the infections revealed a higher MOI in patients with uncomplicated disease, with the P. falciparum K1 MSP1 (MSP1-K1) and MSP2-3D7 being the most discriminative allelic markers. Higher MOIs also correlated positively with higher antibody levels in several of the ELISAs. In conclusion, certain antibody responses and MOIs were associated with differences between uncomplicated and severe malaria. When different assays were combined, some antibodies, like those against AMA1, seemed particularly discriminative. However, only decreased invasion correlated with initial parasitemia in the patient, signaling the importance of functional assays in understanding development of immunity against malaria and in evaluating vaccine candidates.
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Hamid MMA, Mohammed SB, El Hassan IM. Genetic Diversity of Plasmodium falciparum Field Isolates in Central Sudan Inferred by PCR Genotyping of Merozoite Surface Protein 1 and 2. NORTH AMERICAN JOURNAL OF MEDICAL SCIENCES 2013; 5:95-101. [PMID: 23641369 PMCID: PMC3624726 DOI: 10.4103/1947-2714.107524] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND Characterization of Plasmodium falciparum diversity is commonly achieved by amplification of the polymorphic regions of the merozoite surface proteins 1 (MSP1) and 2 (MSP2) genes. AIMS The present study aimed to determine the allelic variants distribution of MSP1 and MSP2 and multiplicity of infection in P. falciparum field isolates from Kosti, central Sudan, an area characterized by seasonal malaria transmission. MATERIALS AND METHODS Total 121 samples (N = 121) were collected during a cross-sectional survey between March and April 2003. DNA was extracted and MSP1 and MSP2 polymorphic loci were genotyped. RESULTS The total number of alleles identified in MSP1 block 2 was 11, while 16 alleles were observed in MSP2 block 3. In MSP1, RO33 was found to be the predominant allelic type, carried alone or in combination with MAD20 and K1 types, whereas FC27 family was the most prevalent in MSP2. Sixty two percent of isolates had multiple genotypes and the overall mean multiplicity of infection was 1.93 (CI 95% 1.66-2.20). Age correlated with parasite density (P = 0.017). In addition, a positive correlation was observed between parasite densities and the number of alleles (P = 0.022). CONCLUSION Genetic diversity in P. falciparum field isolates in central Sudan was high and consisted of multiple clones.
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Affiliation(s)
- Muzamil M Abdel Hamid
- Department of Molecular Biology, Institute of Endemic Diseases, University of Khartoum, Khartoum, Sudan
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17
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Lundblom K, Murungi L, Nyaga V, Olsson D, Rono J, Osier F, Ogada E, Montgomery S, Scott JAG, Marsh K, Färnert A. Plasmodium falciparum infection patterns since birth and risk of severe malaria: a nested case-control study in children on the coast of Kenya. PLoS One 2013; 8:e56032. [PMID: 23418502 PMCID: PMC3572150 DOI: 10.1371/journal.pone.0056032] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Accepted: 01/04/2013] [Indexed: 01/27/2023] Open
Abstract
Children in malaria endemic areas acquire immunity to severe malaria faster than to mild malaria. Only a minority of children suffers from severe malaria and it is not known what determines this. The aim of this study was to establish how P. falciparum infections during the first years of life affect the risk of severe malaria. A matched case-control study was nested within a large birth cohort set up to study the immunoepidemiology of pneumococci on the Kenyan coast. Infection patterns in three-monthly blood samples in cohort children admitted to hospital with severe malaria were compared to controls matched on age, residential location and time of sampling. P. falciparum detected at least once from birth conferred an increased risk of severe malaria and particularly if multiclonal infections, as characterized by genotyping of a polymorphic antigen gene, were ever detected. The results show for the first time that children with severe malaria have more infections early in life compared to community controls. These findings provide important insights on the immunity to severe disease, knowledge essential for the development of a vaccine against severe malaria.
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Affiliation(s)
- Klara Lundblom
- Unit of Infectious Diseases, Department of Medicine Solna, Karolinska Institute, Stockholm, Sweden.
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18
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Ankarklev J, Svärd SG, Lebbad M. Allelic sequence heterozygosity in single Giardia parasites. BMC Microbiol 2012; 12:65. [PMID: 22554281 PMCID: PMC3438080 DOI: 10.1186/1471-2180-12-65] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 05/03/2012] [Indexed: 12/17/2022] Open
Abstract
Background Genetic heterogeneity has become a major inconvenience in the genotyping and molecular epidemiology of the intestinal protozoan parasite Giardia intestinalis, in particular for the major human infecting genotype, assemblage B. Sequence-based genotyping of assemblage B Giardia from patient fecal samples, where one or several of the commonly used genotyping loci (beta-giardin, triosephosphate isomerase and glutamate dehydrogenase) are implemented, is often hampered due to the presence of sequence heterogeneity in the sequencing chromatograms. This can be due to allelic sequence heterozygosity (ASH) and /or co-infections with parasites of different assemblage B sub-genotypes. Thus, two important questions have arisen; i) does ASH occur at the single cell level, and/or ii) do multiple sub-genotype infections commonly occur in patients infected with assemblage B, G. intestinalis isolates? Results We used micromanipulation in order to isolate single Giardia intestinalis, assemblage B trophozoites (GS isolate) and cysts from human patients. Molecular analysis at the tpi loci of trophozoites from the GS lineage indicated that ASH is present at the single cell level. Analyses of assemblage B Giardia cysts from clinical samples at the bg and tpi loci also indicated ASH at the single cell level. Additionally, alignment of sequence data from several different cysts that originated from the same patient yielded different sequence patterns, thus suggesting the presence of multiple sub-assemblage infections in congruence with ASH within the same patient. Conclusions Our results conclusively show that ASH does occur at the single cell level in assemblage B Giardia. Furthermore, sequence heterogeneity generated during sequence-based genotyping of assemblage B isolates may possess the complexity of single cell ASH in concurrence with co-infections of different assemblage B sub-genotypes. These findings explain the high abundance of sequence heterogeneity commonly found when performing sequence based genotyping of assemblage B Giardia, and illuminates the necessity of developing new G. intestinalis genotyping tools.
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Affiliation(s)
- Johan Ankarklev
- Department of Cell and Molecular Biology, BMC, Uppsala University, Uppsala, Sweden.
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19
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Nsango SE, Abate L, Thoma M, Pompon J, Fraiture M, Rademacher A, Berry A, Awono-Ambene PH, Levashina EA, Morlais I. Genetic clonality of Plasmodium falciparum affects the outcome of infection in Anopheles gambiae. Int J Parasitol 2012; 42:589-95. [PMID: 22554991 DOI: 10.1016/j.ijpara.2012.03.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Revised: 03/26/2012] [Accepted: 03/27/2012] [Indexed: 01/13/2023]
Abstract
Mosquito infections with natural isolates of Plasmodium falciparum are notoriously variable and pose a problem for reliable evaluation of efficiency of transmission-blocking agents for malaria control interventions. Here, we show that monoclonal P. falciparum isolates produce higher parasite loads than mixed ones. Induction of the mosquito immune responses by wounding efficiently decreases Plasmodium numbers in monoclonal infections but fails to do so in infections with two or more parasite genotypes. Our results point to the parasites genetic complexity as a potentially crucial component of mosquito-parasite interactions.
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Affiliation(s)
- Sandrine E Nsango
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale, BP 288, Yaoundé, Cameroon
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Bharti PK, Shukla MM, Sharma YD, Singh N. Genetic diversity in the block 2 region of the merozoite surface protein-1 of Plasmodium falciparum in central India. Malar J 2012; 11:78. [PMID: 22439658 PMCID: PMC3324372 DOI: 10.1186/1475-2875-11-78] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Accepted: 03/22/2012] [Indexed: 12/04/2022] Open
Abstract
Background Malaria continues to be a significant health problem in India. Several of the intended Plasmodium falciparum vaccine candidate antigens are highly polymorphic. The genetic diversity of P. falciparum merozoite surface protein-1 (MSP-1) has been extensively studied from various parts of the world. However, limited data are available from India. The aim of the present study was a molecular characterization of block 2 region of MSP-1 gene from the tribal-dominated, forested region of Madhya Pradesh. Methods DNA sequencing analysis was carried out in 71 field isolates collected between July 2005 to November 2005 and in 98 field isolates collected from July 2009 to December 2009. Alleles identified by DNA sequencing were aligned with the strain 3D7 and polymorphism analysis was done by using Edit Sequence tool (DNASTAR). Results The malaria positivity was 26% in 2005, which rose to 29% in 2009 and P. falciparum prevalence was also increased from 72% in 2005 to 81% in 2009. The overall allelic prevalence was higher in K1 (51%) followed by MAD20 (28%) and RO33 (21%) in 2005 while in 2009, RO33 was highest (40%) followed by K1 (36%) and MAD20 (24%). Conclusions The present study reports extensive genetic variations and dynamic evolution of block 2 region of MSP-1 in central India. Characterization of antigenic diversity in vaccine candidate antigens are valuable for future vaccine trials as well as understanding the population dynamics of P. falciparum parasites in this area.
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Affiliation(s)
- Praveen K Bharti
- Regional Medical Research Centre for Tribals, Garha, Jabalpur 482003, Madhya Pradesh, India
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Genetic polymorphism of merozoite surface protein-1 and merozoite surface protein-2 in Plasmodium falciparum isolates from Brazzaville, Republic of Congo. Malar J 2011; 10:276. [PMID: 21936949 PMCID: PMC3195763 DOI: 10.1186/1475-2875-10-276] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Accepted: 09/22/2011] [Indexed: 11/10/2022] Open
Abstract
Background The characterization of malaria parasite populations circulating in an area is part of site characterization, as a basis for evaluating the impact of malaria interventions on genetic diversity, parasite species, and multiplicity of infection. The present study was aimed at analysing genetic diversity of Plasmodium falciparum merozoite surface proteins 1 and 2 (MSP-1 and MSP-2) and to determine the multiplicity of infection in clinical isolates collected from children living in the Southern district of Brazzaville in the Republic of Congo. Methods A total of 125 isolates from patients with uncomplicated malaria attending Terinkyo and Madibou health centres were collected between January and June 2005 while evaluating the therapeutic efficacy of amodiaquine-artesunate combination. DNA was extracted and msp-1 and msp-2 genes were genotyped using allele-specific nested-PCR. Results Out of 468 distinct fragments detected, 15 msp-1 and 20 msp-2 genotypes were identified. For the msp-1 gene, K1 family was the predominant allelic type carried alone or in association with RO33 and Mad20 types, whereas the 3D7 family was the most prevalent in the msp-2 gene. Overall, the mean multiplicity of infection was 2.2. Out of 125 samples, 104 (83%) harboured more than one parasite genotype. There was no statistical significant difference in the multiplicity of infection by either sex or age of patients. However, a statistically significant correlation was found between parasite densities and the number of genotypes. Conclusion Polymorphism in P. falciparum clinical isolates from Brazzaville was high and mainly of multiple clones. The basis for the positive association between parasite densities and multiplicity of infection is discussed.
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Petersen I, Eastman R, Lanzer M. Drug-resistant malaria: molecular mechanisms and implications for public health. FEBS Lett 2011; 585:1551-62. [PMID: 21530510 DOI: 10.1016/j.febslet.2011.04.042] [Citation(s) in RCA: 173] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Revised: 04/15/2011] [Accepted: 04/18/2011] [Indexed: 10/18/2022]
Abstract
Resistance to antimalarial drugs has often threatened malaria elimination efforts and historically has led to the short-term resurgence of malaria incidences and deaths. With concentrated malaria eradication efforts currently underway, monitoring drug resistance in clinical settings complemented by in vitro drug susceptibility assays and analysis of resistance markers, becomes critical to the implementation of an effective antimalarial drug policy. Understanding of the factors, which lead to the development and spread of drug resistance, is necessary to design optimal prevention and treatment strategies. This review attempts to summarize the unique factors presented by malarial parasites that lead to the emergence and spread of drug resistance, and gives an overview of known resistance mechanisms to currently used antimalarial drugs.
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Affiliation(s)
- Ines Petersen
- Department of Infectious Diseases, Parasitology, Universitätsklinikum Heidelberg, Heidelberg, Germany.
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Ochola LB, Siddondo BR, Ocholla H, Nkya S, Kimani EN, Williams TN, Makale JO, Liljander A, Urban BC, Bull PC, Szestak T, Marsh K, Craig AG. Specific receptor usage in Plasmodium falciparum cytoadherence is associated with disease outcome. PLoS One 2011; 6:e14741. [PMID: 21390226 PMCID: PMC3048392 DOI: 10.1371/journal.pone.0014741] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Accepted: 01/07/2011] [Indexed: 12/22/2022] Open
Abstract
Our understanding of the basis of severe disease in malaria is incomplete. It is clear that pathology is in part related to the pro-inflammatory nature of the host response but a number of other factors are also thought to be involved, including the interaction between infected erythrocytes and endothelium. This is a complex system involving several host receptors and a major parasite-derived variant antigen (PfEMP1) expressed on the surface of the infected erythrocyte membrane. Previous studies have suggested a role for ICAM-1 in the pathology of cerebral malaria, although these have been inconclusive. In this study we have examined the cytoadherence patterns of 101 patient isolates from varying clinical syndromes to CD36 and ICAM-1, and have used variant ICAM-1 proteins to further characterise this adhesive phenotype. Our results show that increased binding to CD36 is associated with uncomplicated malaria while ICAM-1 adhesion is raised in parasites from cerebral malaria cases.
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Affiliation(s)
- Lucy B Ochola
- KEMRI/Wellcome Trust Research Programme, Centre for Geographic Medicine Research, Kilifi, Kenya.
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Liljander A, Bejon P, Mwacharo J, Kai O, Ogada E, Peshu N, Marsh K, Färnert A. Clearance of asymptomatic P. falciparum Infections Interacts with the number of clones to predict the risk of subsequent malaria in Kenyan children. PLoS One 2011; 6:e16940. [PMID: 21383984 PMCID: PMC3044709 DOI: 10.1371/journal.pone.0016940] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Accepted: 01/17/2011] [Indexed: 12/20/2022] Open
Abstract
Background Protective immunity to malaria is acquired after repeated infections in endemic areas. Asymptomatic multiclonal P. falciparum infections are common and may predict host protection. Here, we have investigated the effect of clearing asymptomatic infections on the risk of clinical malaria. Methods Malaria episodes were continuously monitored in 405 children (1–6 years) in an area of moderate transmission, coastal Kenya. Blood samples collected on four occasions were assessed by genotyping the polymorphic P. falciparum merozoite surface protein 2 using fluorescent PCR and capillary electrophoresis. Following the second survey, asymptomatic infections were cleared with a full course of dihydroartemisinin. Results Children who were parasite negative by PCR had a lower risk of subsequent malaria regardless of whether treatment had been given. Children with ≥2 clones had a reduced risk of febrile malaria compared with 1 clone after clearance of asymptomatic infections, but not if asymptomatic infections were not cleared. Multiclonal infection was associated with an increased risk of re-infection after drug treatment. However, among the children who were re-infected, multiclonal infections were associated with a shift from clinical malaria to asymptomatic parasitaemia. Conclusion The number of clones was associated with exposure as well as blood stage immunity. These effects were distinguished by clearing asymptomatic infection with anti-malarials. Exposure to multiple P. falciparum infections is associated with protective immunity, but there appears to be an additional effect in untreated multiclonal infections that offsets this protective effect.
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Affiliation(s)
- Anne Liljander
- Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
| | - Philip Bejon
- Centre for Geographical Medicine Research (Coast), Kenya Medical Research Institute, Kilifi, Kenya
- Nuffield Department of Clinical Medicine, Oxford University, John Radcliffe Hospital, Oxford, United Kingdom
| | - Jedidah Mwacharo
- Centre for Geographical Medicine Research (Coast), Kenya Medical Research Institute, Kilifi, Kenya
| | - Oscar Kai
- Centre for Geographical Medicine Research (Coast), Kenya Medical Research Institute, Kilifi, Kenya
| | - Edna Ogada
- Centre for Geographical Medicine Research (Coast), Kenya Medical Research Institute, Kilifi, Kenya
| | - Norbert Peshu
- Centre for Geographical Medicine Research (Coast), Kenya Medical Research Institute, Kilifi, Kenya
| | - Kevin Marsh
- Centre for Geographical Medicine Research (Coast), Kenya Medical Research Institute, Kilifi, Kenya
- Nuffield Department of Clinical Medicine, Oxford University, John Radcliffe Hospital, Oxford, United Kingdom
| | - Anna Färnert
- Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
- * E-mail:
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Chen DS, Barry AE, Leliwa-Sytek A, Smith TA, Peterson I, Brown SM, Migot-Nabias F, Deloron P, Kortok MM, Marsh K, Daily JP, Ndiaye D, Sarr O, Mboup S, Day KP. A molecular epidemiological study of var gene diversity to characterize the reservoir of Plasmodium falciparum in humans in Africa. PLoS One 2011; 6:e16629. [PMID: 21347415 PMCID: PMC3036650 DOI: 10.1371/journal.pone.0016629] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Accepted: 01/06/2011] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The reservoir of Plasmodium infection in humans has traditionally been defined by blood slide positivity. This study was designed to characterize the local reservoir of infection in relation to the diverse var genes that encode the major surface antigen of Plasmodium falciparum blood stages and underlie the parasite's ability to establish chronic infection and transmit from human to mosquito. METHODOLOGY/PRINCIPAL FINDINGS We investigated the molecular epidemiology of the var multigene family at local sites in Gabon, Senegal and Kenya which differ in parasite prevalence and transmission intensity. 1839 distinct var gene types were defined by sequencing DBLα domains in the three sites. Only 76 (4.1%) var types were found in more than one population indicating spatial heterogeneity in var types across the African continent. The majority of var types appeared only once in the population sample. Non-parametric statistical estimators predict in each population at minimum five to seven thousand distinct var types. Similar diversity of var types was seen in sites with different parasite prevalences. CONCLUSIONS/SIGNIFICANCE Var population genomics provides new insights into the epidemiology of P. falciparum in Africa where malaria has never been conquered. In particular, we have described the extensive reservoir of infection in local African sites and discovered a unique var population structure that can facilitate superinfection through minimal overlap in var repertoires among parasite genomes. Our findings show that var typing as a molecular surveillance system defines the extent of genetic complexity in the reservoir of infection to complement measures of malaria prevalence. The observed small scale spatial diversity of var genes suggests that var genetics could greatly inform current malaria mapping approaches and predict complex malaria population dynamics due to the import of var types to areas where no widespread pre-existing immunity in the population exists.
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Affiliation(s)
- Donald S. Chen
- Department of Medical Parasitology, New York University School of Medicine, New York, New York, United States of America
- Department of Medicine, New York University School of Medicine, New York, New York, United States of America
| | - Alyssa E. Barry
- Department of Medical Parasitology, New York University School of Medicine, New York, New York, United States of America
- Peter Medawar Building for Pathogen Research and Department of Zoology, University of Oxford, Oxford, United Kingdom
- Centre for Population Health, Burnet Institute, Melbourne, Australia
- Department of Medicine, Central and Eastern Clinical School, Monash University, Victoria, Australia
| | - Aleksandra Leliwa-Sytek
- Department of Medical Parasitology, New York University School of Medicine, New York, New York, United States of America
| | - Terry-Ann Smith
- Department of Medical Parasitology, New York University School of Medicine, New York, New York, United States of America
| | - Ingrid Peterson
- Department of Medical Parasitology, New York University School of Medicine, New York, New York, United States of America
| | - Stuart M. Brown
- Center for Health Informatics and Bioinformatics, New York University School of Medicine, New York, New York, United States of America
| | - Florence Migot-Nabias
- Institut de Recherche pour le Développement, Faculté de Pharmacie, Université Paris 5, Paris, France
| | - Philippe Deloron
- Institut de Recherche pour le Développement, Faculté de Pharmacie, Université Paris 5, Paris, France
| | - Moses M. Kortok
- Kenya Medical Research Institute, Centre for Geographic Medicine Research, Kilifi, Kenya
| | - Kevin Marsh
- Kenya Medical Research Institute, Centre for Geographic Medicine Research, Kilifi, Kenya
| | - Johanna P. Daily
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, United States of America
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Daouda Ndiaye
- Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, Dakar, Senegal
| | - Ousmane Sarr
- Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, Dakar, Senegal
| | - Souleymane Mboup
- Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, Dakar, Senegal
| | - Karen P. Day
- Department of Medical Parasitology, New York University School of Medicine, New York, New York, United States of America
- Peter Medawar Building for Pathogen Research and Department of Zoology, University of Oxford, Oxford, United Kingdom
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Liljander A, Chandramohan D, Kweku M, Olsson D, Montgomery SM, Greenwood B, Färnert A. Influences of intermittent preventive treatment and persistent multiclonal Plasmodium falciparum infections on clinical malaria risk. PLoS One 2010; 5:e13649. [PMID: 21048970 PMCID: PMC2965101 DOI: 10.1371/journal.pone.0013649] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Accepted: 09/12/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Intermittent preventive treatment (IPT) of malaria involves administration of curative doses of antimalarials at specified time points to vulnerable populations in endemic areas, regardless whether a subject is known to be infected. The effect of this new intervention on the development and maintenance of protective immunity needs further understanding. We have investigated how seasonal IPT affects the genetic diversity of Plasmodium falciparum infections and the risk of subsequent clinical malaria. MATERIAL AND METHODS The study included 2227 Ghanaian children (3-59 months) who were given sulphadoxine-pyrimethamine (SP) bimonthly, artesunate plus amodiaquine (AS+AQ) monthly or bimonthly, or placebo monthly for six months spanning the malaria transmission season. Blood samples collected at three post-interventional surveys were analysed by genotyping of the polymorphic merozoite surface protein 2 gene. Malaria morbidity and anaemia was monitored during 12 months follow-up. RESULTS Monthly IPT with AS+AQ resulted in a marked reduction in number of concurrent clones and only children parasite negative just after the intervention period developed clinical malaria during follow-up. In the placebo group, children without parasites as well as those infected with ≥2 clones had a reduced risk of subsequent malaria. The bimonthly SP or AS+AQ groups had similar number of clones as placebo after intervention; however, diversity and parasite negativity did not predict the risk of malaria. An interaction effect showed that multiclonal infections were only associated with protection in children without intermittent treatment. CONCLUSION Molecular typing revealed effects of the intervention not detected by ordinary microscopy. Effective seasonal IPT temporarily reduced the prevalence and genetic diversity of P. falciparum infections. The reduced risk of malaria in children with multiclonal infections only seen in untreated children suggests that persistence of antigenically diverse P. falciparum infections is important for the maintenance of protective malaria immunity in high transmission settings.
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Affiliation(s)
- Anne Liljander
- Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
| | - Daniel Chandramohan
- Infectious and Tropical Diseases Department, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Margaret Kweku
- Infectious and Tropical Diseases Department, London School of Hygiene and Tropical Medicine, London, United Kingdom
- Ghana Health Service, University of Ghana, Accra, Ghana
| | - Daniel Olsson
- Medical Statistics Unit, Department of Learning Informatics Management and Ethics, Karolinska Institutet, Stockholm, Sweden
| | - Scott M. Montgomery
- Clinical Epidemiology Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
- Clinical Epidemiology and Biostatistics Unit, Örebro University Hospital, Örebro, Sweden
- Department of Primary Care and Social Medicine, Charing Cross Hospital, Imperial College, London, United Kingdom
| | - Brian Greenwood
- Infectious and Tropical Diseases Department, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Anna Färnert
- Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
- * E-mail:
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Buchholz U, Kobbe R, Danquah I, Zanger P, Reither K, Abruquah HH, Grobusch MP, Ziniel P, May J, Mockenhaupt FP. Multiplicity of Plasmodium falciparum infection following intermittent preventive treatment in infants. Malar J 2010; 9:244. [PMID: 20796302 PMCID: PMC2939622 DOI: 10.1186/1475-2875-9-244] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Accepted: 08/26/2010] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND Intermittent preventive treatment in infants with sulphadoxine-pyrimethamine (IPTi-SP) reduces malaria morbidity by 20% to 33%. Potentially, however, this intervention may compromise the acquisition of immunity, including the tolerance towards multiple infections with Plasmodium falciparum. METHODS Plasmodium falciparum isolates were obtained from children participating in two Ghanaian IPTi-SP trials (Tamale, Afigya Sekyere) at 15 months of age, i.e., six months after they had received the second dose of IPTi-SP or placebo. By typing the polymorphic merozoite surface protein 1 (msp1) and msp2 genes, multiplicity of infection (MOI) was assessed in 389 isolates. A total of additional 133 samples were collected in Tamale at 3, 6, 9, and 12 months of age. Comparisons of MOI between groups were done by non-parametric statistical tests. RESULTS The number of distinguishable P. falciparum clones (MOI) ranged between one and six. Mean MOI in Tamale was stable at 2.13 - 2.17 during the first year of life, and increased to 2.57 at age 15 months (P = 0.01). At no age did MOI differ between the IPTi-SP and placebo groups (each, P ≥ 0.5). At 15 months of age, i.e., six months after the second dose, MOI was very similar for children who had received IPTi or placebo (means, 2.25 vs. 2.33; P = 0.55) as was the proportion of polyclonal infections (69.6% vs. 69.7%; P = 0.99). Adjusting for study site, current and prior malaria, parasite density, and season did not change this finding. CONCLUSIONS IPTi-SP appears to have no impact on the multiplicity of infection during infancy and thereafter. This suggests that tolerance of multiple infections, a component of protective immunity in highly endemic areas, is not affected by this intervention.
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Affiliation(s)
- Ulrike Buchholz
- Institute of Tropical Medicine and International Health, Charité - University Medicine, Berlin, Germany
| | - Robin Kobbe
- Infectious Disease Epidemiology Group, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - Ina Danquah
- Institute of Tropical Medicine and International Health, Charité - University Medicine, Berlin, Germany
| | - Philipp Zanger
- Institute of Tropical Medicine and International Health, Charité - University Medicine, Berlin, Germany
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
| | - Klaus Reither
- Institute of Tropical Medicine and International Health, Charité - University Medicine, Berlin, Germany
- Swiss Tropical and Public Health Institute, Basel, Switzerland
| | - Harry H Abruquah
- Division of Microbiology and Infectious Diseases, University Hospital, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | - Martin P Grobusch
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
- Medical Research Unit, Hôpital Albert Schweitzer, Lambaréné, Gabon
- Department of Infectious Diseases, Tropical Medicine, HIV/AIDS, Amsterdam Medical Center, University of Amsterdam, The Netherlands
| | - Peter Ziniel
- Northern Region Malaria Project, Tamale, Ghana
- Dept. of Immunology & Microbiology, Rush University, Chicago, USA
| | - Jürgen May
- Infectious Disease Epidemiology Group, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - Frank P Mockenhaupt
- Institute of Tropical Medicine and International Health, Charité - University Medicine, Berlin, Germany
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