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Balam S, Miura K, Ayadi I, Konaté D, Incandela NC, Agnolon V, Guindo MA, Diakité SA, Olugbile S, Nebie I, Herrera SM, Long C, Kajava AV, Diakité M, Corradin G, Herrera S, Herrera MA. Cross-reactivity of r Pvs48/45, a recombinant Plasmodium vivax protein, with sera from Plasmodium falciparum endemic areas of Africa. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.10.588966. [PMID: 38659832 PMCID: PMC11042229 DOI: 10.1101/2024.04.10.588966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Background Ps48/45, a Plasmodium gametocyte surface protein, is a promising candidate for malaria transmission-blocking (TB) vaccine. Due to its relevance for a multispecies vaccine, we explored the cross-reactivity and TB activity of a recombinant P. vivax Ps48/45 protein (rPvs48/45) with sera from P. falciparum-exposed African donors. Methods rPvs48/45 was produced in Chinese hamster ovary cell lines and tested by ELISA for its cross-reactivity with sera from Burkina Faso, Tanzania, Mali, and Nigeria - In addition, BALB/c mice were immunized with the rPvs48/45 protein formulated in Montanide ISA-51 and inoculated with a crude extract of P. falciparum NF-54 gametocytes to evaluate the parasite-boosting effect on rPvs48/45 antibody titers. Specific anti-rPvs48/45 IgG purified from African sera was used to evaluate the ex vivo TB activity on P. falciparum, using standard mosquito membrane feeding assays (SMFA). Results rPvs48/45 protein showed cross-reactivity with sera of individuals from all four African countries, in proportions ranging from 94% (Tanzania) to 40% (Nigeria). Also, the level of cross-reactive antibodies varied significantly between countries (p<0.0001), with a higher antibody level in Mali and the lowest in Nigeria. In addition, antibody levels were higher in adults (≥ 17 years) than young children (≤ 5 years) in both Mali and Tanzania, with a higher proportion of responders in adults (90%) than in children (61%) (p<0.0001) in Mali, where male (75%) and female (80%) displayed similar antibody responses. Furthermore, immunization of mice with P. falciparum gametocytes boosted anti-Pvs48/45 antibody responses, recognizing P. falciparum gametocytes in indirect immunofluorescence antibody test. Notably, rPvs48/45 affinity-purified African IgG exhibited a TB activity of 61% against P. falciparum in SMFA. Conclusion African sera (exposed only to P. falciparum) cross-recognized the rPvs48/45 protein. This, together with the functional activity of IgG, warrants further studies for the potential development of a P. vivax and P. falciparum cross-protective TB vaccine.
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Affiliation(s)
- Saidou Balam
- International Center for Excellence in Research (ICER-Mali), University of Sciences, Techniques and Technologies of Bamako (USTTB), Bamako, Mali
| | - Kazutoyo Miura
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA
| | - Imen Ayadi
- Immunobiology Department, University of Lausanne, Lausanne, Switzerland
| | - Drissa Konaté
- International Center for Excellence in Research (ICER-Mali), University of Sciences, Techniques and Technologies of Bamako (USTTB), Bamako, Mali
| | | | - Valentina Agnolon
- Division of Immunology and Allergy, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Switzerland aaaa
| | - Merepen A Guindo
- International Center for Excellence in Research (ICER-Mali), University of Sciences, Techniques and Technologies of Bamako (USTTB), Bamako, Mali
| | - Seidina A.S. Diakité
- International Center for Excellence in Research (ICER-Mali), University of Sciences, Techniques and Technologies of Bamako (USTTB), Bamako, Mali
| | - Sope Olugbile
- Immunobiology Department, University of Lausanne, Lausanne, Switzerland
| | - Issa Nebie
- Groupe de Recherche Action Santé (GRAS), Burkina Faso, West Africa
| | | | - Carole Long
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA
| | - Andrey V. Kajava
- Montpellier Cell Biology Research Center (CRBM), University of Montpellier, CNRS, France
| | - Mahamadou Diakité
- International Center for Excellence in Research (ICER-Mali), University of Sciences, Techniques and Technologies of Bamako (USTTB), Bamako, Mali
| | | | - Socrates Herrera
- Caucaseco Scientific Research Center, Cali, Colombia
- Malaria Vaccine and Drug Development Center, Cali, Colombia
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ApiAP2 Gene-Network Regulates Gametocytogenesis in Plasmodium Parasites. Cell Microbiol 2022. [DOI: 10.1155/2022/5796578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Malaria is a mosquito-borne infectious disease, caused by unicellular Apicomplexan protozoa of the genus Plasmodium. The sexual stage of Plasmodium is one of the most fascinating aspects of the Plasmodium life cycle, yet relatively less explored until now. The production of sexually fit gametocytes through gametocytogenesis is essential to the transmission of the Plasmodium parasite into an anopheline mosquito vector. Understanding how gametocytogenesis is regulated promotes the identification of novel drug targets and also the development of transmission-blocking vaccines that would help reduce the disease burden in endemic areas. Transcriptional regulation in Plasmodium parasites is primarily controlled by a family of twenty-seven Apicomplexan Apetela 2 (ApiAP2) genes which act in a cascade to enable the parasite to progress through its asexual replication as well as gametocytogenesis. Here, we review the latest progress made on members of the ApiAP2 family characterized as key players of the transcriptional machinery of gametocytes. Further, we will highlight the transcriptional regulation network of ApiAP2 genes at each stage of gametocytogenesis.
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de Jong RM, Alkema M, Oulton T, Dumont E, Teelen K, Nakajima R, de Assis RR, Press KWD, Ngotho P, Tetteh KK, Felgner P, Marti M, Collins KA, Drakeley C, Bousema T, Stone WJ. The acquisition of humoral immune responses targeting Plasmodium falciparum sexual stages in controlled human malaria infections. Front Immunol 2022; 13:930956. [PMID: 35924245 PMCID: PMC9339717 DOI: 10.3389/fimmu.2022.930956] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 06/28/2022] [Indexed: 11/13/2022] Open
Abstract
Individuals infected with P. falciparum develop antibody responses to intra-erythrocytic gametocyte proteins and exported gametocyte proteins present on the surface of infected erythrocytes. However, there is currently limited knowledge on the immunogenicity of gametocyte antigens and the specificity of gametocyte-induced antibody responses. In this study, we assessed antibody responses in participants of two controlled human malaria infection (CHMI) studies by ELISA, multiplexed bead-based antibody assays and protein microarray. By comparing antibody responses in participants with and without gametocyte exposure, we aimed to disentangle the antibody response induced by asexual and sexual stage parasites. We showed that after a single malaria infection, a significant anti-sexual stage humoral response is induced in malaria-naïve individuals, even after exposure to relatively low gametocyte densities (up to ~1,600 gametocytes/mL). In contrast to antibody responses to well-characterised asexual blood stage antigens that were detectable by day 21 after infection, responses to sexual stage antigens (including transmission blocking vaccine candidates Pfs48/45 and Pfs230) were only apparent at 51 days after infection. We found antigens previously associated with early gametocyte or anti-gamete immunity were highly represented among responses linked with gametocyte exposure. Our data provide detailed insights on the induction and kinetics of antibody responses to gametocytes and identify novel antigens that elicit antibody responses exclusively in individuals with gametocyte exposure. Our findings provide target identification for serological assays for surveillance of the malaria infectious reservoir, and support vaccine development by describing the antibody response to leading vaccine antigens after primary infection.
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Affiliation(s)
- Roos M. de Jong
- Department of Medical Microbiology and Radboud Centre of Infectious Diseases, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Manon Alkema
- Department of Medical Microbiology and Radboud Centre of Infectious Diseases, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Tate Oulton
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Elin Dumont
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Karina Teelen
- Department of Medical Microbiology and Radboud Centre of Infectious Diseases, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Rie Nakajima
- Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, United States
| | - Rafael Ramiro de Assis
- Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, United States
| | | | - Priscilla Ngotho
- Wellcome Centre for Integrative Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Kevin K.A. Tetteh
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Phil Felgner
- Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, United States
| | - Matthias Marti
- Wellcome Centre for Integrative Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Katharine A. Collins
- Department of Medical Microbiology and Radboud Centre of Infectious Diseases, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Chris Drakeley
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Teun Bousema
- Department of Medical Microbiology and Radboud Centre of Infectious Diseases, Radboud University Medical Centre, Nijmegen, Netherlands,Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Will J.R. Stone
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom,*Correspondence: Will J.R. Stone,
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Sauerwein RW, Plieskatt J, Theisen M. 40 Years of Pfs48/45 Research as a Transmission-Blocking Vaccine Target of Plasmodium falciparum Malaria. Am J Trop Med Hyg 2022; 107:tpmd211320. [PMID: 35895389 DOI: 10.4269/ajtmh.21-1320] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 03/17/2022] [Indexed: 02/18/2024] Open
Abstract
In the early 1980s, Richard Carter was among the first researchers to identify the sexual stage-specific Pfs48/45 protein, leading to the identification of target epitopes. Carter predicted its tertiary conformation while involved in a number of studies on naturally acquired sexual stage-specific antibodies. Pfs48/45 is a cysteine-rich surface protein of sexual stages of Plasmodium falciparum that plays a critical role in male gamete fertility. Antibodies against Pfs48/45 prevent parasite development in the mosquito vector, and therefore prevent the spread of malaria in the population. Since the gene was sequenced in the early 1990s, Pfs48/45 has been considered a prime target candidate for a malaria transmission-blocking vaccine. However, major manufacturing challenges-in particular, difficulty realizing satisfactory yields of a properly folded protein for the induction of functional antibodies-delayed clinical development significantly. These challenges were met roughly 20 years later. The first clinical trial with a Pfs48/45 subunit vaccine (R0.6C) was started in the Netherlands in early 2021. The excellent contributions to the long and winding path of Pfs48/45 research by Richard Carter are well recognized and are an integrated part of his seminal contributions to unraveling Plasmodium sexual stage biology.
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Affiliation(s)
| | - Jordan Plieskatt
- Department for Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark
| | - Michael Theisen
- Department for Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark
- Centre for Medical Parasitology, Department of Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark
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Kyomuhangi I, Giorgi E. A threshold-free approach with age-dependency for estimating malaria seroprevalence. Malar J 2022; 21:1. [PMID: 34980109 PMCID: PMC8725324 DOI: 10.1186/s12936-021-04022-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 12/12/2021] [Indexed: 11/21/2022] Open
Abstract
Background In malaria serology analysis, the standard approach to obtain seroprevalence, i.e the proportion of seropositive individuals in a population, is based on a threshold which is used to classify individuals as seropositive or seronegative. The choice of this threshold is often arbitrary and is based on methods that ignore the age-dependency of the antibody distribution. Methods Using cross-sectional antibody data from the Western Kenyan Highlands, this paper introduces a novel approach that has three main advantages over the current threshold-based approach: it avoids the use of thresholds; it accounts for the age dependency of malaria antibodies; and it allows us to propagate the uncertainty from the classification of individuals into seropositive and seronegative when estimating seroprevalence. The reversible catalytic model is used as an example for illustrating how to propagate this uncertainty into the parameter estimates of the model. Results This paper finds that accounting for age-dependency leads to a better fit to the data than the standard approach which uses a single threshold across all ages. Additionally, the paper also finds that the proposed threshold-free approach is more robust against the selection of different age-groups when estimating seroprevalence. Conclusion The novel threshold-free approach presented in this paper provides a statistically principled and more objective approach to estimating malaria seroprevalence. The introduced statistical framework also provides a means to compare results across studies which may use different age ranges for the estimation of seroprevalence. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-04022-4.
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Affiliation(s)
- Irene Kyomuhangi
- CHICAS, Lancaster University, Sir John Fisher Drive, Lancaster, UK.
| | - Emanuele Giorgi
- CHICAS, Lancaster University, Sir John Fisher Drive, Lancaster, UK
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Spatial cluster analysis of Plasmodium vivax and P. malariae exposure using serological data among Haitian school children sampled between 2014 and 2016. PLoS Negl Trop Dis 2022; 16:e0010049. [PMID: 34986142 PMCID: PMC8765618 DOI: 10.1371/journal.pntd.0010049] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 01/18/2022] [Accepted: 12/03/2021] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Estimation of malaria prevalence in very low transmission settings is difficult by even the most advanced diagnostic tests. Antibodies against malaria antigens provide an indicator of active or past exposure to these parasites. The prominent malaria species within Haiti is Plasmodium falciparum, but P. vivax and P. malariae infections are also known to be endemic. METHODOLOGY/PRINCIPAL FINDINGS From 2014-2016, 28,681 Haitian children were enrolled in school-based serosurveys and were asked to provide a blood sample for detection of antibodies against multiple infectious diseases. IgG against the P. falciparum, P. vivax, and P. malariae merozoite surface protein 19kD subunit (MSP119) antigens was detected by a multiplex bead assay (MBA). A subset of samples was also tested for Plasmodium DNA by PCR assays, and for Plasmodium antigens by a multiplex antigen detection assay. Geospatial clustering of high seroprevalence areas for P. vivax and P. malariae antigens was assessed by both Ripley's K-function and Kulldorff's spatial scan statistic. Of 21,719 children enrolled in 680 schools in Haiti who provided samples to assay for IgG against PmMSP119, 278 (1.27%) were seropositive. Of 24,559 children enrolled in 788 schools providing samples for PvMSP119 serology, 113 (0.46%) were seropositive. Two significant clusters of seropositivity were identified throughout the country for P. malariae exposure, and two identified for P. vivax. No samples were found to be positive for Plasmodium DNA or antigens. CONCLUSIONS/SIGNIFICANCE From school-based surveys conducted from 2014 to 2016, very few Haitian children had evidence of exposure to P. vivax or P. malariae, with no children testing positive for active infection. Spatial scan statistics identified non-overlapping areas of the country with higher seroprevalence for these two malarias. Serological data provides useful information of exposure to very low endemic malaria species in a population that is unlikely to present to clinics with symptomatic infections.
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Muthui MK, Takashima E, Omondi BR, Kinya C, Muasya WI, Nagaoka H, Mwai KW, Orindi B, Wambua J, Bousema T, Drakeley C, Blagborough AM, Marsh K, Bejon P, Kapulu MC. Characterization of Naturally Acquired Immunity to a Panel of Antigens Expressed in Mature P. falciparum Gametocytes. Front Cell Infect Microbiol 2021; 11:774537. [PMID: 34869075 PMCID: PMC8633105 DOI: 10.3389/fcimb.2021.774537] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Accepted: 10/25/2021] [Indexed: 11/13/2022] Open
Abstract
Introduction Naturally acquired immune responses against antigens expressed on the surface of mature gametocytes develop in individuals living in malaria-endemic areas. Evidence suggests that such anti-gametocyte immunity can block the development of the parasite in the mosquito, thus playing a role in interrupting transmission. A better comprehension of naturally acquired immunity to these gametocyte antigens can aid the development of transmission-blocking vaccines and improve our understanding of the human infectious reservoir. Methods Antigens expressed on the surface of mature gametocytes that had not previously been widely studied for evidence of naturally acquired immunity were identified for protein expression alongside Pfs230-C using either the mammalian HEK293E or the wheat germ cell-free expression systems. Where there was sequence variation in the candidate antigens (3D7 vs a clinical isolate PfKE04), both variants were expressed. ELISA was used to assess antibody responses against these antigens, as well as against crude stage V gametocyte extract (GE) and AMA1 using archived plasma samples from individuals recruited to participate in malaria cohort studies. We analyzed antibody levels (estimated from optical density units using a standardized ELISA) and seroprevalence (defined as antibody levels greater than three standard deviations above the mean levels of a pool of malaria naïve sera). We described the dynamics of antibody responses to these antigens by identifying factors predictive of antibody levels using linear regression models. Results Of the 25 antigens selected, seven antigens were produced successfully as recombinant proteins, with one variant antigen, giving a total of eight proteins for evaluation. Antibodies to the candidate antigens were detectable in the study population (N = 216), with seroprevalence ranging from 37.0% (95% CI: 30.6%, 43.9%) for PSOP1 to 77.8% (95% CI: 71.6%, 83.1%) for G377 (3D7 variant). Responses to AMA1 and GE were more prevalent than those to the gametocyte proteins at 87.9% (95% CI: 82.8%, 91.9%) and 88.3% (95% CI: 83.1%, 92.4%), respectively. Additionally, both antibody levels and breadth of antibody responses were associated with age and concurrent parasitaemia. Conclusion Age and concurrent parasitaemia remain important determinants of naturally acquired immunity to gametocyte antigens. Furthermore, we identify novel candidates for transmission-blocking activity evaluation.
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Affiliation(s)
- Michelle K Muthui
- Department of Biosciences, Kenya Medical Research Institute (KEMRI)-Wellcome Trust Programme, Kilifi, Kenya
| | - Eizo Takashima
- Division of Malaria Research, Proteo-Science Center, Ehime University, Matsuyama, Japan
| | - Brian R Omondi
- Department of Biosciences, Kenya Medical Research Institute (KEMRI)-Wellcome Trust Programme, Kilifi, Kenya
| | - Christine Kinya
- Department of Biosciences, Kenya Medical Research Institute (KEMRI)-Wellcome Trust Programme, Kilifi, Kenya
| | - William I Muasya
- Department of Biosciences, Kenya Medical Research Institute (KEMRI)-Wellcome Trust Programme, Kilifi, Kenya
| | - Hikaru Nagaoka
- Division of Malaria Research, Proteo-Science Center, Ehime University, Matsuyama, Japan
| | - Kennedy W Mwai
- Department of Biosciences, Kenya Medical Research Institute (KEMRI)-Wellcome Trust Programme, Kilifi, Kenya.,School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Benedict Orindi
- Department of Biosciences, Kenya Medical Research Institute (KEMRI)-Wellcome Trust Programme, Kilifi, Kenya
| | - Juliana Wambua
- Department of Biosciences, Kenya Medical Research Institute (KEMRI)-Wellcome Trust Programme, Kilifi, Kenya
| | - Teun Bousema
- Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Chris Drakeley
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Andrew M Blagborough
- Division of Microbiology and Parasitology, Department of Pathology, Cambridge University, Tennis Court Road, Cambridge, United Kingdom
| | - Kevin Marsh
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Philip Bejon
- Department of Biosciences, Kenya Medical Research Institute (KEMRI)-Wellcome Trust Programme, Kilifi, Kenya.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Melissa C Kapulu
- Department of Biosciences, Kenya Medical Research Institute (KEMRI)-Wellcome Trust Programme, Kilifi, Kenya.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
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Ayanful-Torgby R, Sarpong E, Abagna HB, Donu D, Obboh E, Mensah BA, Adjah J, Williamson KC, Amoah LE. Persistent Plasmodium falciparum infections enhance transmission-reducing immunity development. Sci Rep 2021; 11:21380. [PMID: 34725428 PMCID: PMC8560775 DOI: 10.1038/s41598-021-00973-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 10/21/2021] [Indexed: 11/09/2022] Open
Abstract
Subclinical infections that serve as reservoir populations to drive transmission remain a hurdle to malaria control. Data on infection dynamics in a geographical area is required to strategically design and implement malaria interventions. In a longitudinal cohort, we monitored Plasmodium falciparum infection prevalence and persistence, and anti-parasite immunity to gametocyte and asexual antigens for 10 weeks. Of the 100 participants, only 11 were never infected, whilst 16 had persistent infections detected by reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR), and one participant had microscopic parasites at all visits. Over 70% of the participants were infected three or more times, and submicroscopic gametocyte prevalence was high, ≥ 48% of the parasite carriers. Naturally induced responses against recombinant Pfs48/45.6C, Pfs230proC, and EBA175RIII-V antigens were not associated with either infection status or gametocyte carriage, but the antigen-specific IgG titers inversely correlated with parasite and gametocyte densities consistent with partial immunity. Longitudinal analysis of gametocyte diversity indicated at least four distinct clones circulated throughout the study period. The high prevalence of children infected with distinct gametocyte clones coupled with marked variation in infection status at the individual level suggests ongoing transmission and should be targeted in malaria control programs.
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Affiliation(s)
- Ruth Ayanful-Torgby
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana.
| | | | - Hamza B Abagna
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
| | - Dickson Donu
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
| | | | - Benedicta A Mensah
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
| | - Joshua Adjah
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
| | - Kim C Williamson
- Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Linda E Amoah
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana.
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