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Mbugi EV, den Hartog G, Veenemans J, Chilongola JO, Verhoef H, Savelkoul HFJ. Nutrient Deficiencies and Potential Alteration in Plasma Levels of Naturally Acquired Malaria-Specific Antibody Responses in Tanzanian Children. Front Nutr 2022; 9:872710. [PMID: 35782946 PMCID: PMC9247637 DOI: 10.3389/fnut.2022.872710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 05/02/2022] [Indexed: 11/17/2022] Open
Abstract
Immunoglobulin G (IgG) subclasses have been suggested to confer naturally acquired immunity to Plasmodium falciparum malaria. Cytophilic IgG1 and IgG3 with their potential for opsonization, phagocytosis, and antibody-dependent cellular inhibition in association with monocytes have been suggested to have a critical role in malaria. The potential for production of antibodies is influenced by micronutrient status. This study aimed at exploring the effect of micronutrients, particularly zinc status, on the profiles of IgG subclasses in 304 Tanzanian children aged ≤ 5 years. An enzyme-linked immunosorbent assay was performed using whole asexual blood stage malaria antigens to determine plasma malaria-specific antibody titers. This baseline cross-sectional study was done from 2005 – 2010 prior to the larger randomized control trial of the Micronutrient and Child Health (MACH) Study. Plasma concentrations of zinc and magnesium were measured by inductively coupled plasma atomic emission spectrometry and results correlated with plasma IgG subclass levels. The findings reveal zinc deficiency to possibly influence the production of IgM, total IgG, and several IgG subclasses in a malaria status-dependent manner. Among IgG subclasses, IgG3 and partly IgG2 displayed a remarkable association with zinc deficiency, particularly IgG3 which was predominant in children with malaria. Nevertheless, zinc, magnesium, and malaria status did not influence the association between IgG3 and IgG4. The study leads to the conclusion that, under conditions of micronutrient deficiency and malaria status, an imbalance in IgG subclass production may occur leading to predominantly higher levels of IgG3 and IgG2 that may not confer sufficient protection from infection. The profile of both cytophilic and non-cytophilic IgG subclasses has been shown to be variably influenced by zinc status; the effects vary with age at least in under-fives. These results provide insight for inclusion of micronutrients, particularly precise amounts of zinc, in future malaria interventional programs in endemic areas.
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Affiliation(s)
- Erasto V. Mbugi
- Cell Biology and Immunology Group, Department of Animal Sciences, Wageningen University, Wageningen, Netherlands
- Department of Medical Biochemistry and Molecular Biology, Kilimanjaro Christian Medical University College, Moshi, Tanzania
- *Correspondence: Erasto V. Mbugi ;
| | - Gerco den Hartog
- Cell Biology and Immunology Group, Department of Animal Sciences, Wageningen University, Wageningen, Netherlands
| | - Jacobien Veenemans
- Cell Biology and Immunology Group, Department of Animal Sciences, Wageningen University, Wageningen, Netherlands
| | - Jaffu O. Chilongola
- Department of Biochemistry, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - Hans Verhoef
- Cell Biology and Immunology Group, Department of Animal Sciences, Wageningen University, Wageningen, Netherlands
- Nutrition and Public Health Intervention Research Unit, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Huub F. J. Savelkoul
- Cell Biology and Immunology Group, Department of Animal Sciences, Wageningen University, Wageningen, Netherlands
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Blank A, Fürle K, Jäschke A, Mikus G, Lehmann M, Hüsing J, Heiss K, Giese T, Carter D, Böhnlein E, Lanzer M, Haefeli WE, Bujard H. Immunization with full-length Plasmodium falciparum merozoite surface protein 1 is safe and elicits functional cytophilic antibodies in a randomized first-in-human trial. NPJ Vaccines 2020; 5:10. [PMID: 32025341 PMCID: PMC6994672 DOI: 10.1038/s41541-020-0160-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 01/14/2020] [Indexed: 12/20/2022] Open
Abstract
A vaccine remains a priority in the global fight against malaria. Here, we report on a single-center, randomized, double-blind, placebo and adjuvant-controlled, dose escalation phase 1a safety and immunogenicity clinical trial of full-length Plasmodium falciparum merozoite surface protein 1 (MSP1) in combination with GLA-SE adjuvant. Thirty-two healthy volunteers were vaccinated at least three times with MSP1 plus adjuvant, adjuvant alone, or placebo (24:4:4) to evaluate the safety and immunogenicity. MSP1 was safe, well tolerated and immunogenic, with all vaccinees sero-converting independent of the dose. The MSP1-specific IgG and IgM titers persisted above levels found in malaria semi-immune humans for at least 6 months after the last immunization. The antibodies were variant- and strain-transcending and stimulated respiratory activity in granulocytes. Furthermore, full-length MSP1 induced memory T-cells. Our findings encourage challenge studies as the next step to evaluate the efficacy of full-length MSP1 as a vaccine candidate against falciparum malaria (EudraCT 2016-002463-33).
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Affiliation(s)
- Antje Blank
- Klinische Pharmakologie und Pharmakoepidemiologie, Universitätsklinikum Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Kristin Fürle
- Center of Infectious Diseases, Parasitology, Universitätsklinikum Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
| | - Anja Jäschke
- Center of Infectious Diseases, Parasitology, Universitätsklinikum Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
| | - Gerd Mikus
- Klinische Pharmakologie und Pharmakoepidemiologie, Universitätsklinikum Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Monika Lehmann
- Koordinierungszentrum für Klinische Studien (KKS), Universitätsklinikum Heidelberg, Im Neuenheimer Feld 130.3, 69120 Heidelberg, Germany
| | - Johannes Hüsing
- Koordinierungszentrum für Klinische Studien (KKS), Universitätsklinikum Heidelberg, Im Neuenheimer Feld 130.3, 69120 Heidelberg, Germany
| | - Kirsten Heiss
- PEPperPRINT GmbH, Rischerstrasse 12, 69123 Heidelberg, Germany
| | - Thomas Giese
- Institut für Immunologie, Universitätsklinikum Heidelberg und Deutsches Zentrum für Infektionsforschung (DZIF) Standort Heidelberg, Im Neuenheimer Feld 305, 69120 Heidelberg, Germany
| | - Darrick Carter
- PAI Life Sciences, 1616 Eastlake Ave E, Suite 550, Seattle, WA 98102 USA
| | - Ernst Böhnlein
- Sumaya Biotech GmbH & Co. KG, Im Neuenheimer Feld 582, 69120 Heidelberg, Germany
| | - Michael Lanzer
- Center of Infectious Diseases, Parasitology, Universitätsklinikum Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
| | - Walter E. Haefeli
- Klinische Pharmakologie und Pharmakoepidemiologie, Universitätsklinikum Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Hermann Bujard
- Sumaya Biotech GmbH & Co. KG, Im Neuenheimer Feld 582, 69120 Heidelberg, Germany
- Zentrum für Molekulare Biologie Heidelberg, Universität Heidelberg, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
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Kwenti TE, Kukwah TA, Kwenti TDB, Nyassa BR, Dilonga MH, Enow-Orock G, Tendongfor N, Anong ND, Wanji S, Njunda LA, Nkuo-Akenji T. Comparative analysis of IgG and IgG subclasses against Plasmodium falciparum MSP-1 19 in children from five contrasting bioecological zones of Cameroon. Malar J 2019; 18:16. [PMID: 30670064 PMCID: PMC6341684 DOI: 10.1186/s12936-019-2654-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 01/16/2019] [Indexed: 12/03/2022] Open
Abstract
Background Studies reporting the natural immune responses against malaria in children from different geographical settings in endemic areas are not readily available. This study was aimed at comparing the immune responses against Plasmodium falciparum MSP-119 antigen in children from five contrasting bioecological zones in Cameroon. Methods In a cross-sectional survey, children between 2 and 15 years, were enrolled from five ecological strata including the south Cameroonian equatorial forest, sudano-sahelian, high inland plateau, high western plateau, and the coastal strata. The children were screened for clinical malaria (defined by malaria parasitaemia ≥ 5000 parasites/µl plus axillary temperature ≥ 37.5 °C). Their antibody responses were measured against P. falciparum MSP-119 antigen using standard ELISA technique. Results In all, 415 children comprising 217 (52.3%) males participated. Total IgG and IgG1–IgG4 titres were observed to increase with age in all the strata except in the sudano-sahelian and high inland plateau strata. Total IgG and IgG1–IgG4 titres were significantly higher in the coastal strata and lowest in the high inland plateau (for IgG1 and IgG2) and sudano-sahelian strata (for IgG3 and IgG4). Titres of the cytophilic antibodies (IgG1 and IgG3) were significantly higher than the non-cytophilic antibodies (IgG2 and IgG4) in all the strata except in the sudano-sahelian and high inland plateau strata. Total IgG and IgG subclass titres were significantly higher in children positive for clinical malaria compared to negative children in all study sites except in the high western plateau and coastal (for IgG1 and IgG3), and the sudano-sahelian strata (for all antibodies). Furthermore, a significant positive correlation was observed between parasite density and IgG2 or IgG4 titres in all study sites except in the south Cameroonian equatorial forest and sudano-sahelian strata. Conclusions This study showed that antibody responses against MSP-119 vary considerably in children from the different bioecological strata in Cameroon and could be linked to the differential exposure to malaria in the different strata. Furthermore, the rate of antibody acquisition was not observed to increase in an age-dependent manner in low transmission settings. Electronic supplementary material The online version of this article (10.1186/s12936-019-2654-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Tebit Emmanuel Kwenti
- Department of Medical Laboratory Sciences, Faculty of Health Science, University of Buea, P.O. Box 23, Buea, Southwest Region, Cameroon. .,Regional Hospital of Buea, P.O. Box 32, Buea, Southwest Region, Cameroon. .,Department of Public Health and Hygiene, Faculty of Health Science, University of Buea, P.O. Box 23, Buea, Southwest Region, Cameroon. .,Department of Microbiology and Parasitology, Faculty of Science, University of Buea, P.O. Box 63, Buea, Southwest Region, Cameroon.
| | - Tufon Anthony Kukwah
- Regional Hospital of Buea, P.O. Box 32, Buea, Southwest Region, Cameroon.,Department of Microbiology and Parasitology, Faculty of Science, University of Buea, P.O. Box 63, Buea, Southwest Region, Cameroon
| | - Tayong Dizzle Bita Kwenti
- Department of Microbiology and Parasitology, Faculty of Science, University of Buea, P.O. Box 63, Buea, Southwest Region, Cameroon
| | - Babila Raymond Nyassa
- Department of Microbiology and Parasitology, Faculty of Science, University of Buea, P.O. Box 63, Buea, Southwest Region, Cameroon
| | - Meriki Henry Dilonga
- Regional Hospital of Buea, P.O. Box 32, Buea, Southwest Region, Cameroon.,Department of Microbiology and Parasitology, Faculty of Science, University of Buea, P.O. Box 63, Buea, Southwest Region, Cameroon
| | - George Enow-Orock
- Regional Hospital of Buea, P.O. Box 32, Buea, Southwest Region, Cameroon.,Department of Biomedical Science, Faculty of Health Science, University of Buea, P.O Box 23, Buea, Southwest Region, Cameroon
| | - Nicholas Tendongfor
- Department of Public Health and Hygiene, Faculty of Health Science, University of Buea, P.O. Box 23, Buea, Southwest Region, Cameroon.,Department of Microbiology and Parasitology, Faculty of Science, University of Buea, P.O. Box 63, Buea, Southwest Region, Cameroon
| | - Nota Damian Anong
- Department of Biological Science, Faculty of Science, University of Bamenda, Bamenda, North West Region, Cameroon
| | - Samuel Wanji
- Parasites and Vector Biology Research Unit, Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Longdoh Anna Njunda
- Department of Medical Laboratory Sciences, Faculty of Health Science, University of Buea, P.O. Box 23, Buea, Southwest Region, Cameroon
| | - Theresa Nkuo-Akenji
- Department of Biological Science, Faculty of Science, University of Bamenda, Bamenda, North West Region, Cameroon
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Kwenti TE, Moye AL, Wiylanyuy AB, Njunda LA, Nkuo-Akenji T. Variation in the immune responses against Plasmodium falciparum merozoite surface protein-1 and apical membrane antigen-1 in children residing in the different epidemiological strata of malaria in Cameroon. Malar J 2017; 16:453. [PMID: 29121929 PMCID: PMC5679504 DOI: 10.1186/s12936-017-2105-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Accepted: 11/02/2017] [Indexed: 11/12/2022] Open
Abstract
Background Studies to assess the immune responses against malaria in Cameroonian children are limited. The purpose of this study was to assess the immune responses against Plasmodium falciparum merozoite surface protein-1 (MSP-119) and apical membrane antigen-1 (AMA-1) in children residing in the different epidemiological strata of malaria in Cameroon. Methods In a cross-sectional survey performed between April and July 2015, 602 children between 2 and 15 years (mean ± SD = 5.7 ± 3.7), comprising 319 (53%) males were enrolled from five epidemiological strata of malaria in Cameroon including: the sudano-sahelian (SS) strata, the high inland plateau (HIP) strata, the south Cameroonian equatorial forest (SCEF) strata, the high western plateau (HWP) strata, and the coastal (C) strata. The children were screened for clinical malaria (defined by malaria parasitaemia ≥ 5000 parasites/µl plus axillary temperature ≥ 37.5 °C). Their antibody responses were measured against P. falciparum MSP-119 and AMA-1 vaccine candidate antigens using standard ELISA technique. Results A majority of the participants were IgG responders 72.1% (95% CI 68.3–75.6). The proportion of responders was higher in females (p = 0.002) and in children aged 10 years and above (p = 0.005). The proportion of responders was highest in Limbe (C strata) and lowest in Ngaoundere (HIP strata) (p < 0.0001). Similarly, the mean IgG antibody levels were higher in children aged 10 years and above (p < 0.0001) and in Limbe (p = 0.001). The IgG antibody levels against AMA-1 were higher in females (p = 0.028), meanwhile no gender disparity was observed with MSP-1. Furthermore the risk of clinical malaria (p < 0.0001) and the mean parasite density (p = 0.035) were higher in IgG non-responders. Conclusion A high proportion of IgG responders was observed in this study, suggesting a high degree exposure of the target population to malaria parasites. The immune responses varied considerably across the different strata: the highest levels observed in the C strata and the lowest in the HIP strata. Furthermore, malaria transmission in Cameroon could be categorized into two major groups based on the serological reaction of the children: the southern (comprising C and SCEF strata) and northern (comprising HWP, HIP and SS strata) groups. These findings may have significant implications in the design of future trials for evaluating malaria vaccine candidates in Cameroon.
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Affiliation(s)
- Tebit Emmanuel Kwenti
- Department of Microbiology and Parasitology, University of Buea, P.B. 63, Buea, Cameroon. .,Department of Medical Laboratory Sciences, University of Buea, P.B. 63, Buea, Cameroon.
| | | | | | - Longdoh Anna Njunda
- Department of Microbiology and Parasitology, University of Buea, P.B. 63, Buea, Cameroon
| | - Theresa Nkuo-Akenji
- Department of Microbiology and Parasitology, University of Buea, P.B. 63, Buea, Cameroon
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Hill DL, Schofield L, Wilson DW. IgG opsonization of merozoites: multiple immune mechanisms for malaria vaccine development. Int J Parasitol 2017; 47:585-595. [PMID: 28668325 DOI: 10.1016/j.ijpara.2017.05.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 04/12/2017] [Accepted: 05/12/2017] [Indexed: 02/07/2023]
Abstract
Global eradication of the human-infecting malaria parasite Plasmodium falciparum, the major cause of malaria mortality, is unlikely to be achieved without an effective vaccine. However, our limited understanding of how protective immune responses target malaria parasites in humans, and how to best elicit these immune responses through vaccination, has hampered vaccine development. The red blood cell invading stage of the parasite lifecycle (merozoite) displays antigens that are attractive vaccine candidates as they are accessible to antibodies and raise high antibody titres in naturally immune individuals. The number of merozoite antigens that elicit an immune response, and their structural and functional diversity, has led to a large number of lead antigens being pursued as vaccine candidates. Despite being seemingly spoilt for choice in terms of vaccine candidates, there is still a lack of consensus on exactly how merozoite antibodies reduce parasitemia and malaria disease. In this review we describe the various immune mechanisms that can result from IgG opsonization of merozoites, and highlight recent developments that support a role for these functional antibodies in naturally acquired and vaccine-induced immunity.
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Affiliation(s)
- Danika L Hill
- Babraham Institute, Babraham Research Campus, Cambridge, United Kingdom; The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia; Department of Medical Biology, University of Melbourne, Parkville, Australia.
| | - Louis Schofield
- Australian Institute of Tropical Health and Medicine, James Cook University, Townsville, Australia
| | - Danny W Wilson
- Research Centre for Infectious Diseases, School of Biological Sciences, University of Adelaide, Adelaide, Australia; Burnet Institute, 85 Commercial Road, Melbourne 3004, Victoria, Australia.
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Plasmodium falciparum infection and age influence parasite growth inhibition mediated by IgG in Beninese infants. Acta Trop 2016; 159:111-9. [PMID: 27001144 DOI: 10.1016/j.actatropica.2016.03.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 02/10/2016] [Accepted: 03/17/2016] [Indexed: 11/22/2022]
Abstract
Antibodies that impede the invasion of Plasmodium falciparum (P. falciparum) merozoites into erythrocytes play a critical role in anti-malarial immunity. The Growth Inhibition Assay (GIA) is an in vitro measure of the functional capacity of such antibodies to limit erythrocyte invasion and/or parasite growth. Up to now, it is unclear whether growth-inhibitory activity correlates with protection from clinical disease and there are inconsistent results from studies performed with GIA. Studies that have focused on the relationship between IgGs and their in vitro parasite Growth Inhibition Activity (GIAc) in infants aged less than two years old are rare. Here, we used clinical and parasitological data to precisely define symptomatic or asymptomatic infection with P. falciparum in groups of infants followed-up actively for 18 months post-natally. We quantified the levels of IgG1 and IgG3 directed to a panel of candidate P. falciparum vaccine antigens (AMA-1, MSP1, 2, 3 and GLURP) using ELISA and the functional activity of IgG was quantified using GIA. Data were then correlated with individuals' infection status. At 18 months of age, infants harbouring infections at the time of blood sampling had an average 19% less GIAc than those not infected (p=0.004, multivariate linear regression). GIAc decreased from 12 to 18 months of age (p=0.003, Wilcoxon matched pairs test). Antibody levels quantified at 18 months in infants were strongly correlated with their exposure to malarial infection, however GIAc was not correlated with malaria infectious status (asymptomatic and symptomatic groups). In conclusion, both infection status at blood draw and age influence parasite growth inhibition mediated by IgG in the GIA. Both factors must be taken into account when correlations between GIAc and anti-malarial protection or vaccine efficacy have to be made.
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Ord RL, Rodriguez M, Lobo CA. Malaria invasion ligand RH5 and its prime candidacy in blood-stage malaria vaccine design. Hum Vaccin Immunother 2016; 11:1465-73. [PMID: 25844685 DOI: 10.1080/21645515.2015.1026496] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
With drug resistance to available therapeutics continuing to develop against Plasmodium falciparum malaria, the development of an effective vaccine candidate remains a major research goal. Successful interruption of invasion of parasites into erythrocytes during the blood stage of infection will prevent the severe clinical symptoms and complications associated with malaria. Previously studied blood stage antigens have highlighted the hurdles that are inherent to this life-cycle stage, namely that highly immunogenic antigens are also globally diverse, resulting in protection only against the vaccine strain, or that naturally acquired immunity to blood stage antigens do not always correlate with actual protection. The blood stage antigen reticulocyte binding homolog RH5 is essential for parasite viability, has globally limited diversity, and is associated with protection from disease. Here we summarize available information on this invasion ligand and recent findings that highlight its candidacy for inclusion in a blood-stage malaria vaccine.
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Affiliation(s)
- Rosalynn L Ord
- a Blood-Borne Parasites; Lindsley Kimball Research Institute; New York Blood Center ; New York , NY , USA
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Serology describes a profile of declining malaria transmission in Farafenni, The Gambia. Malar J 2015; 14:416. [PMID: 26492873 PMCID: PMC4618886 DOI: 10.1186/s12936-015-0939-1] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 10/09/2015] [Indexed: 11/23/2022] Open
Abstract
Background Malaria morbidity and mortality has declined in recent years in a number of settings. The ability to describe changes in malaria transmission associated with these declines is important in terms of assessing the potential effects of control interventions, and for monitoring and evaluation purposes. Methods Data from five cross-sectional surveys conducted in Farafenni and surrounding villages on the north bank of River Gambia between 1988 and 2011 were compiled. Antibody responses to MSP-119 were measured in samples from all surveys, data were normalized and expressed as seroprevalence and seroconversion rates (SCR) using different mathematical models. Results Results showed declines in serological metrics with seroprevalence in children aged one to 5 years dropping from 19 % (95 % CI 15–23 %) in 1988 to 1 % (0–2 %) in 2011 (p value for trend in proportions < 0.001) and the SCR dropping from 0.069 year−1 (0.059–0.080) to 0.022 year−1 (0.017–0.028; p = 0.004). The serological data were consistent with previously described drops in both parasite prevalence in children aged 1–5 years (62 %, 57–66 %, in 1988 to 2 %, 0–4 %, in 2011; p < 0.001), and all-cause under five mortality rates (37 per 1000 person-years, 34–41, in 1990 to 17, 15–19, in 2006; p = 0.059). Conclusions This analysis shows accurate reconstruction of historical malaria transmission patterns in the Farafenni area using anti-malarial antibody responses. Demonstrating congruence between serological measures, and conventional clinical and parasitological measures suggests broader utility for serology in monitoring and evaluation of malaria transmission. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0939-1) contains supplementary material, which is available to authorized users.
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Diversity and population structure of Plasmodium falciparum in Thailand based on the spatial and temporal haplotype patterns of the C-terminal 19-kDa domain of merozoite surface protein-1. Malar J 2014; 13:54. [PMID: 24521474 PMCID: PMC3931489 DOI: 10.1186/1475-2875-13-54] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 01/27/2014] [Indexed: 11/21/2022] Open
Abstract
Background The 19-kDa C-terminal region of the merozoite surface protein-1 of the human malaria parasite Plasmodium falciparum (PfMSP-119) constitutes the major component on the surface of merozoites and is considered as one of the leading candidates for asexual blood stage vaccines. Because the protein exhibits a level of sequence variation that may compromise the effectiveness of a vaccine, the global sequence diversity of PfMSP-119 has been subjected to extensive research, especially in malaria endemic areas. In Thailand, PfMSP-119 sequences have been derived from a single parasite population in Tak province, located along the Thailand-Myanmar border, since 1995. However, the extent of sequence variation and the spatiotemporal patterns of the MSP-119 haplotypes along the Thai borders with Laos and Cambodia are unknown. Methods Sixty-three isolates of P. falciparum from five geographically isolated populations along the Thai borders with Myanmar, Laos and Cambodia in three transmission seasons between 2002 and 2008 were collected and culture-adapted. The msp-1 gene block 17 was sequenced and analysed for the allelic diversity, frequency and distribution patterns of PfMSP-119 haplotypes in individual populations. The PfMSP-119 haplotype patterns were then compared between parasite populations to infer the population structure and genetic differentiation of the malaria parasite. Results Five conserved polymorphic positions, which accounted for five distinct haplotypes, of PfMSP-119 were identified. Differences in the prevalence of PfMSP-119 haplotypes were detected in different geographical regions, with the highest levels of genetic diversity being found in the Kanchanaburi and Ranong provinces along the Thailand-Myanmar border and Trat province located at the Thailand-Cambodia border. Despite this variability, the distribution patterns of individual PfMSP-119 haplotypes seemed to be very similar across the country and over the three malarial transmission seasons, suggesting that gene flow may operate between parasite populations circulating in Thailand and the three neighboring countries. Conclusion The major MSP-119 haplotypes of P. falciparum populations in all endemic populations during three transmission seasons in Thailand were identified, providing basic information on the common haplotypes of MSP-119 that is of use for malaria vaccine development and inferring the population structure of P. falciparum populations in Thailand.
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Patel SD, Ahouidi AD, Bei AK, Dieye TN, Mboup S, Harrison SC, Duraisingh MT. Plasmodium falciparum merozoite surface antigen, PfRH5, elicits detectable levels of invasion-inhibiting antibodies in humans. J Infect Dis 2013; 208:1679-87. [PMID: 23904294 DOI: 10.1093/infdis/jit385] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Plasmodium falciparum is an intracellular protozoan parasite that infects erythrocytes and hepatocytes. The blood stage of its life cycle causes substantial morbidity and mortality associated with millions of infections each year, motivating an intensive search for potential components of a multi-subunit vaccine. In this study, we present data showing that antibodies from natural infections can recognize a recombinant form of the relatively conserved merozoite surface antigen, PfRH5. Furthermore, we performed invasion inhibition assays on clinical isolates and laboratory strains of P. falciparum in the presence of affinity purified antibodies to RH5 and show that these antibodies can inhibit invasion in vitro.
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Detecting Foci of Malaria Transmission with School Surveys: A Pilot Study in the Gambia. PLoS One 2013; 8:e67108. [PMID: 23826205 PMCID: PMC3694932 DOI: 10.1371/journal.pone.0067108] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Accepted: 05/16/2013] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND In areas of declining malaria transmission such as in The Gambia, the identification of malaria infected individuals becomes increasingly harder. School surveys may be used to identify foci of malaria transmission in the community. METHODS The survey was carried out in May-June 2011, before the beginning of the malaria transmission season. Thirty two schools in the Upper River Region of The Gambia were selected with probability proportional to size; in each school approximately 100 children were randomly chosen for inclusion in the study. Each child had a finger prick blood sample collected for the determination of antimalarial antibodies by ELISA, malaria infection by microscopy and PCR, and for haemoglobin measurement. In addition, a simple questionnaire on socio-demographic variables and the use of insecticide-treated bed nets was completed. The cut-off for positivity for antimalarial antibodies was obtained using finite mixture models. The clustered nature of the data was taken into account in the analyses. RESULTS A total of 3,277 children were included in the survey. The mean age was 10 years (SD = 2.7) [range 4-21], with males and females evenly distributed. The prevalence of malaria infection as determined by PCR was 13.6% (426/3124) [95% CI = 12.2-16.3] with marked variation between schools (range 3-25%, p<0.001), while the seroprevalence was 7.8% (234/2994) [95%CI = 6.4-9.8] for MSP119, 11.6% (364/2997) [95%CI = 9.4-14.5] for MSP2, and 20.0% (593/2973) [95% CI = 16.5-23.2) for AMA1. The prevalence of all the three antimalarial antibodies positive was 2.7% (79/2920). CONCLUSIONS This survey shows that malaria prevalence and seroprevalence before the transmission season were highly heterogeneous.
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Faber BW, Younis S, Remarque EJ, Rodriguez Garcia R, Riasat V, Walraven V, van der Werff N, van der Eijk M, Cavanagh DR, Holder AA, Thomas AW, Kocken CHM. Diversity covering AMA1-MSP119 fusion proteins as malaria vaccines. Infect Immun 2013; 81:1479-90. [PMID: 23429538 PMCID: PMC3648017 DOI: 10.1128/iai.01267-12] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 02/13/2013] [Indexed: 11/20/2022] Open
Abstract
To overcome polymorphism in the malaria vaccine candidate Plasmodium falciparum apical membrane antigen 1 (PfAMA1), fusion protein chimeras comprised of three diversity-covering (DiCo) PfAMA1 molecules (D1, D2, and D3) and two allelic variants of the C-terminal 19-kDa region of merozoite surface protein 1 (MSP119) (variants M1 and M2) were generated. A mixture of fusion proteins (D1M1/D2M2D3) and the D1M1D2M2D3 fusion were compared to a single-unit mixture (D1/D2/D3/M1) in an immunological study in groups of rabbits. Following immunization, titers of antibodies (Abs) against four naturally occurring PfAMA1 alleles were high for all groups, as were growth inhibition assay (GIA) levels against two antigenically distinct laboratory parasite strains. Fusion of AMA1 to MSP119 did not suppress levels of antibodies against the AMA1 component. In addition, the breadth of antibody responses was unaffected. Anti-AMA1 antibodies were largely responsible for parasite growth inhibition, as shown in reversal-of-inhibition experiments by adding competing AMA1 antigen. For all groups, titration of the MSP119 antigen into the GIA led to only a small decrease in parasite inhibition, although titers of antibodies against MSP119 were increased 15-fold for the groups immunized with fusion proteins. GIA with affinity-purified anti-MSP119 antibodies showed that the 50% inhibitory concentrations of the anti-MSP119 antibody preparations were in the same order of magnitude for all animals tested, leading to the conclusion that fusing MSP119 to PfAMA1 leads to a small but significant increase in functional antibody levels. This study shows that combination of multiple vaccine candidates in fusion proteins may lead to improved characteristics of the vaccine.
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Affiliation(s)
- Bart W. Faber
- Biomedical Primate Research Centre, Department of Parasitology, Rijswijk, The Netherlands
| | - Sumera Younis
- Biomedical Primate Research Centre, Department of Parasitology, Rijswijk, The Netherlands
| | - Edmond J. Remarque
- Biomedical Primate Research Centre, Department of Parasitology, Rijswijk, The Netherlands
| | | | - Vanessa Riasat
- Biomedical Primate Research Centre, Department of Parasitology, Rijswijk, The Netherlands
| | - Vanessa Walraven
- Biomedical Primate Research Centre, Department of Parasitology, Rijswijk, The Netherlands
| | - Nicole van der Werff
- Biomedical Primate Research Centre, Department of Parasitology, Rijswijk, The Netherlands
| | - Marjolein van der Eijk
- Biomedical Primate Research Centre, Department of Parasitology, Rijswijk, The Netherlands
| | - David R. Cavanagh
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Anthony A. Holder
- Division of Parasitology, MRC National Institute for Medical Research, London, United Kingdom
| | - Alan W. Thomas
- Biomedical Primate Research Centre, Department of Parasitology, Rijswijk, The Netherlands
| | - Clemens H. M. Kocken
- Biomedical Primate Research Centre, Department of Parasitology, Rijswijk, The Netherlands
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Duncan CJA, Hill AVS, Ellis RD. Can growth inhibition assays (GIA) predict blood-stage malaria vaccine efficacy? Hum Vaccin Immunother 2012; 8:706-14. [PMID: 22508415 DOI: 10.4161/hv.19712] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
An effective vaccine against P. falciparum malaria remains a global health priority. Blood-stage vaccines are an important component of this effort, with some indications of recent progress. However only a fraction of potential blood-stage antigens have been tested, highlighting a critical need for efficient down-selection strategies. Functional in vitro assays such as the growth/invasion inhibition assays (GIA) are widely used, but it is unclear whether GIA activity correlates with protection or predicts vaccine efficacy. While preliminary data in controlled human malaria infection (CHMI) studies indicate a possible association between in vitro and in vivo parasite growth rates, there have been conflicting results of immunoepidemiology studies, where associations with exposure rather than protection have been observed. In addition, GIA-interfering antibodies in vaccinated individuals from endemic regions may limit assay sensitivity in heavily malaria-exposed populations. More work is needed to establish the utility of GIA for blood-stage vaccine development.
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14
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Plasmodium falciparum line-dependent association of in vitro growth-inhibitory activity and risk of malaria. Infect Immun 2012; 80:1900-8. [PMID: 22392930 DOI: 10.1128/iai.06190-11] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Plasmodium falciparum's ability to invade erythrocytes is essential for its survival within the human host. Immune mechanisms that impair this ability are therefore expected to contribute to immunity against the parasite. Plasma of humans who are naturally exposed to malaria has been shown to have growth-inhibitory activity (GIA) in vitro. However, the importance of GIA in relation to protection from malaria has been unclear. In a case-control study nested within a longitudinally followed population in Tanzania, plasma samples collected at baseline from 171 individuals (55 cases and 116 age-matched controls) were assayed for GIA using three P. falciparum lines (3D7, K1, and W2mef) chosen based on their erythrocyte invasion phenotypes. Distribution of GIA differed between the lines, with most samples inhibiting the growth of 3D7 and K1 and enhancing the growth of W2mef. GIA to 3D7 was associated with a reduced risk of malaria within 40 weeks of follow-up (odds ratio, 0.45; 95% confidence interval [CI], 0.21 to 0.96; P = 0.04), whereas GIA to K1 and W2mef was not. These results show that GIA, as well as its association with protection from malaria, is dependent on the P. falciparum line and can be explained by differences in erythrocyte invasion phenotypes between parasite lines. Our study contributes knowledge on the biological importance of growth inhibition and the potential influence of P. falciparum erythrocyte invasion phenotypic differences on its relationship to protective immunity against malaria.
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15
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Adame-Gallegos JR, Shi J, McIntosh RS, Pleass RJ. The generation and evaluation of two panels of epitope-matched mouse IgG1, IgG2a, IgG2b and IgG3 antibodies specific for Plasmodium falciparum and Plasmodium yoelii merozoite surface protein 1-19 (MSP1(19)). Exp Parasitol 2012; 130:384-93. [PMID: 22343045 PMCID: PMC3336205 DOI: 10.1016/j.exppara.2012.02.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2011] [Revised: 01/28/2012] [Accepted: 02/02/2012] [Indexed: 11/28/2022]
Abstract
Murine immunoglobulin G (IgG) plays an important role in mediating protective immune responses to malaria. We still know relatively little about which IgG subclasses protect against this disease in mouse models, although IgG2a and IgG2b are considered to be the most potent and dominate in successful passive transfer experiments in rodent malarias. To explore the mechanism(s) by which the different mouse IgG subclasses may mediate a protective effect, we generated mouse IgG1, IgG2a, IgG2b and IgG3 specific for the C-terminal 19-kDa region of Plasmodium falciparum merozoite surface protein 1 (PfMSP119), and to the homologous antigen from Plasmodium yoelii (P. yoelii), both major targets of protective immune responses. This panel of eight IgGs bound antigen with an affinity comparable to that seen for their epitope-matched parental monoclonal antibodies (mAbs) from which they were derived, although for reasons of yield, we were only able to explore the function of mouse IgG1 recognizing PfMSP119 in detail, both in vitro and in vivo. Murine IgG1 was as effective as the parental human IgG from which it was derived at inducing NADPH-mediated oxidative bursts and degranulation from neutrophils. Despite showing efficacy in in vitro functional assays with neutrophils, the mouse IgG1 failed to protect against parasite challenge in vivo. The lack of protection afforded by MSP119-specific IgG1 against parasite challenge in wild type mice suggests that this Ab class does not play a major role in the control of infection with mouse malaria in the Plasmodium berghei transgenic model.
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Affiliation(s)
- Jaime R Adame-Gallegos
- Lab C4, Institute of Genetics, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK.
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16
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Revisiting the effect of acute P. falciparum malaria on Epstein-Barr virus: host balance in the setting of reduced malaria endemicity. PLoS One 2012; 7:e31142. [PMID: 22347443 PMCID: PMC3275582 DOI: 10.1371/journal.pone.0031142] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 01/03/2012] [Indexed: 01/08/2023] Open
Abstract
Burkitt's lymphoma (BL), an EBV-associated tumour, occurs at high incidence in populations where malaria is holoendemic. Previous studies in one such population suggested that acute P.falciparum infection impairs EBV-specific T-cell surveillance, allowing expansion of EBV infected B-cells from which BL derives. We re-examined the situation in the same area, The Gambia, after a reduction in malaria endemicity. Cellular immune responses to EBV were measured in children with uncomplicated malaria before (day 0) and after treatment (day 28), comparing EBV genome loads in blood and EBV-specific CD8+ T-cell numbers (assayed by MHC Class I tetramers and IFNγ ELISPOTS) with those seen in age- and sex-matched healthy controls. No significant changes were seen in EBV genome loads, percentage of EBV-specific CD8+ T-cells and IFNγ producing T-cells in acute versus convalescent samples, nor any difference versus controls. Regression assays performed also no longer detected any impairment of EBV-specific T-cell surveillance. Acute uncomplicated malaria infection no longer alters EBV-specific immune responses in children in The Gambia. Given the recent decline in malaria incidence in that country, we hypothesise that gross disturbance of the EBV-host balance may be a specific effect of acute malaria only in children with a history of chronic/recurrent malaria challenge.
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Chimeric parasites as tools to study Plasmodium immunology and assess malaria vaccines. Methods Mol Biol 2012; 923:465-79. [PMID: 22990798 DOI: 10.1007/978-1-62703-026-7_32] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The study of pathogen immunity relies upon being able to track antigen specific immune responses and assess their protective capacity. To study immunity to Plasmodium antigens, chimeric rodent or human malaria parasites that express proteins from other Plasmodium species or unrelated species have been developed. Different types of chimeric parasites have been used to address a range of specific questions. Parasites expressing model T cell epitopes have been used to monitor cellular immune responses to the preerythrocytic and blood stages of malaria. Other parasites have been used to assess the functional significance of immune responses targeting particular proteins. Finally, a number of rodent malaria parasites that express vaccine-candidate antigens from P. falciparum and P. vivax have been used in functional assays of vaccine-induced antibody responses. Here, I review the experimental contributions that have been made using these parasites, and discuss the potential of these approaches to continue advancing our understanding of malaria immunology and vaccine research.
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Khan F, Legler PM, Mease RM, Duncan EH, Bergmann-Leitner ES, Angov E. Histidine affinity tags affect MSP1(42) structural stability and immunodominance in mice. Biotechnol J 2011; 7:133-47. [PMID: 22076863 DOI: 10.1002/biot.201100331] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Revised: 09/23/2011] [Accepted: 11/07/2011] [Indexed: 11/10/2022]
Abstract
Inclusion of affinity tags has greatly facilitated process development for protein antigens, primarily for their recovery from complex mixtures. Although generally viewed as supportive of product development, affinity tags may have unintended consequences on protein solubility, susceptibility to aggregation, and immunogenicity. Merozoite surface protein 1 (MSP1), an erythrocytic stage protein of Plasmodium falciparum and a candidate malaria vaccine, was used to evaluate the impact of a metal ion affinity-tag on both protein structure and the induction of immunity. To this end, codon harmonized gene sequences from the P. falciparum MSP1(42) of FVO and 3D7 parasites were cloned and purified with and without a histidine (His) tag. We report on the influence of His-affinity tags on protein expression levels, solubility, secondary structure, thermal denaturation, aggregation and the impact on humoral and cellular immune responses in mice. While the overall immunogenicity induced by His-tagged MSP1(42) proteins is greater, the fine specificity of the humoral and cellular immune responses is altered relative to anti-parasitic antibody activity and the breadth of T-cell responses. Thus, the usefulness of protein tags may be outweighed by their potential impact on structure and function, stressing the need for caution in their use. See accompanying commentary by Randolph DOI: 10.1002/biot.201100459.
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Affiliation(s)
- Farhat Khan
- Walter Reed Army Institute of Research, Military Malaria Research Program, Malaria Vaccine Branch, Silver Spring, MD, USA
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19
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Plasmodium falciparum 19-kilodalton merozoite surface protein 1 (MSP1)-specific antibodies that interfere with parasite growth in vitro can inhibit MSP1 processing, merozoite invasion, and intracellular parasite development. Infect Immun 2011; 80:1280-7. [PMID: 22202121 DOI: 10.1128/iai.05887-11] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Merozoite surface protein 1 (MSP1) is a target for malaria vaccine development. Antibodies to the 19-kDa carboxy-terminal region referred to as MSP1(19) inhibit erythrocyte invasion and parasite growth, with some MSP1-specific antibodies shown to inhibit the proteolytic processing of MSP1 that occurs at invasion. We investigated a series of antibodies purified from rabbits immunized with MSP1(19) and AMA1 recombinant proteins for their ability to inhibit parasite growth, initially looking at MSP1 processing. Although significant inhibition of processing was mediated by several of the antibody samples, there was no clear relationship with overall growth inhibition by the same antibodies. However, no antibody samples inhibited processing but not invasion, suggesting that inhibition of MSP1 processing contributes to but is not the only mechanism of antibody-mediated inhibition of invasion and growth. Examining other mechanisms by which MSP1-specific antibodies inhibit parasite growth, we show that MSP1(19)-specific antibodies are taken up into invaded erythrocytes, where they persist for significant periods and result in delayed intracellular parasite development. This delay may result from antibody interference with coalescence of MSP1(19)-containing vesicles with the food vacuole. Antibodies raised against a modified recombinant MSP1(19) sequence were more efficient at delaying intracellular growth than those to the wild-type protein. We propose that antibodies specific for MSP1(19) can mediate inhibition of parasite growth by at least three mechanisms: inhibition of MSP1 processing, direct inhibition of invasion, and inhibition of parasite development following invasion. The balance between mechanisms may be modulated by modifying the immunogen used to induce the antibodies.
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20
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Antibodies to Plasmodium falciparum erythrocyte-binding antigen-175 are associated with protection from clinical malaria. Pediatr Infect Dis J 2011; 30:1037-42. [PMID: 21817955 PMCID: PMC3222715 DOI: 10.1097/inf.0b013e31822d1451] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Antibodies to blood-stage Plasmodium falciparum antigens have been associated with protection against clinical malaria in some studies but not others. Many of these studies have not assessed whether high-titer antibodies are associated with protection and have not adjusted for differences in malaria exposure. METHODS The presence of high-titer antibodies to apical membrane antigen-1, erythrocyte-binding antigen-175 (EBA-175), and merozoite surface protein-1₁₉ (MSP-1₁₉) was assessed in 87 children living in a malaria holoendemic area of Kenya. The children were prospectively assessed during 1 year for clinical malaria. RESULTS In unadjusted analyses, high-titer antibodies to MSP-1₁₉, but not EBA-175 or apical membrane antigen-1, were associated with protection from clinical malaria. However, after adjustment for exposure, only high-titer antibodies to EBA-175 were associated with protection from clinical malaria (hazard ratio, 0.48; 95% confidence interval [CI], 0.24, 0.95; P = 0.03), and with reduced episodes of clinical malaria (incidence rate ratio, 0.50; 95% CI, 0.31, 0.81; P = 0.005). A trend toward increased protection from clinical malaria in children was seen with antibodies to both EBA-175 and MSP-1₁₉ (hazard ratio, 0.26; 95% CI, 0.03, 1.94; P = 0.18). CONCLUSIONS High-titer antibodies to EBA-175 are associated with protection from clinical malaria in children in a malaria holoendemic area of Kenya. Accurate estimates of antibody-associated protection from clinical malaria require adjustment for malaria exposure.
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21
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Wilson DW, Fowkes FJI, Gilson PR, Elliott SR, Tavul L, Michon P, Dabod E, Siba PM, Mueller I, Crabb BS, Beeson JG. Quantifying the importance of MSP1-19 as a target of growth-inhibitory and protective antibodies against Plasmodium falciparum in humans. PLoS One 2011; 6:e27705. [PMID: 22110733 PMCID: PMC3217002 DOI: 10.1371/journal.pone.0027705] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 10/23/2011] [Indexed: 12/13/2022] Open
Abstract
Background Antibodies targeting blood stage antigens are important in protection against malaria, but the key targets and mechanisms of immunity are not well understood. Merozoite surface protein 1 (MSP1) is an abundant and essential protein. The C-terminal 19 kDa region (MSP1-19) is regarded as a promising vaccine candidate and may also be an important target of immunity. Methodology/Findings Growth inhibitory antibodies against asexual-stage parasites and IgG to recombinant MSP1-19 were measured in plasma samples from a longitudinal cohort of 206 children in Papua New Guinea. Differential inhibition by samples of mutant P. falciparum lines that expressed either the P. falciparum or P. chabaudi form of MSP1-19 were used to quantify MSP1-19 specific growth-inhibitory antibodies. The great majority of children had detectable IgG to MSP1-19, and high levels of IgG were significantly associated with a reduced risk of symptomatic P. falciparum malaria during the 6-month follow-up period. However, there was little evidence of PfMSP1-19 specific growth inhibition by plasma samples from children. Similar results were found when testing non-dialysed or dialysed plasma, or purified antibodies, or when measuring growth inhibition in flow cytometry or microscopy-based assays. Rabbit antisera generated by immunization with recombinant MSP1-19 demonstrated strong MSP1-19 specific growth-inhibitory activity, which appeared to be due to much higher antibody levels than human samples; antibody avidity was similar between rabbit antisera and human plasma. Conclusions/Significance These data suggest that MSP1-19 is not a major target of growth inhibitory antibodies and that the protective effects of antibodies to MSP1-19 are not due to growth inhibitory activity, but may instead be mediated by other mechanisms. Alternatively, antibodies to MSP1-19 may act as a marker of protective immunity.
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Affiliation(s)
- Danny W. Wilson
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- University of Melbourne, Melbourne, Australia
| | - Freya J. I. Fowkes
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Australia
| | - Paul R. Gilson
- Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Australia
- Monash University, Clayton, Australia
| | - Salenna R. Elliott
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Australia
| | - Livingstone Tavul
- Papua New Guinea Institute of Medical Research (PNGIMR), Goroka, Papua New Guinea
| | - Pascal Michon
- Papua New Guinea Institute of Medical Research (PNGIMR), Goroka, Papua New Guinea
- Faculty of Health Sciences, Divine Word University, Madang, Papua New Guinea
| | - Elija Dabod
- Papua New Guinea Institute of Medical Research (PNGIMR), Goroka, Papua New Guinea
| | - Peter M. Siba
- Papua New Guinea Institute of Medical Research (PNGIMR), Goroka, Papua New Guinea
| | - Ivo Mueller
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Papua New Guinea Institute of Medical Research (PNGIMR), Goroka, Papua New Guinea
- Barcelona Centre for International Health Research (CRESIB), Barcelona, Spain
| | - Brendan S. Crabb
- University of Melbourne, Melbourne, Australia
- Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Australia
| | - James G. Beeson
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Australia
- * E-mail:
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Bejon P, Cook J, Bergmann-Leitner E, Olotu A, Lusingu J, Mwacharo J, Vekemans J, Njuguna P, Leach A, Lievens M, Dutta S, von Seidlein L, Savarese B, Villafana T, Lemnge MM, Cohen J, Marsh K, Corran PH, Angov E, Riley EM, Drakeley CJ. Effect of the pre-erythrocytic candidate malaria vaccine RTS,S/AS01E on blood stage immunity in young children. J Infect Dis 2011; 204:9-18. [PMID: 21628653 PMCID: PMC3105039 DOI: 10.1093/infdis/jir222] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Accepted: 01/20/2011] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND RTS,S/AS01(E) is the lead candidate malaria vaccine and confers pre-erythrocytic immunity. Vaccination may therefore impact acquired immunity to blood-stage malaria parasites after natural infection. METHODS We measured, by enzyme-linked immunosorbent assay, antibodies to 4 Plasmodium falciparum merozoite antigens (AMA-1, MSP-1(42), EBA-175, and MSP-3) and by growth inhibitory activity (GIA) using 2 parasite clones (FV0 and 3D7) at 4 times on 860 children who were randomized to receive with RTS,S/AS01(E) or a control vaccine. RESULTS Antibody concentrations to AMA-1, EBA-175, and MSP-1(42) decreased with age during the first year of life, then increased to 32 months of age. Anti-MSP-3 antibody concentrations gradually increased, and GIA gradually decreased up to 32 months. Vaccination with RTS,S/AS01(E) resulted in modest reductions in AMA-1, EBA-175, MSP-1(42), and MSP-3 antibody concentrations and no significant change in GIA. Increasing anti-merozoite antibody concentrations and GIA were prospectively associated with increased risk of clinical malaria. CONCLUSIONS Vaccination with RTS,S/AS01E reduces exposure to blood-stage parasites and, thus, reduces anti-merozoite antigen antibody concentrations. However, in this study, these antibodies were not correlates of clinical immunity to malaria. Instead, heterogeneous exposure led to confounded, positive associations between increasing antibody concentration and increasing risk of clinical malaria.
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Affiliation(s)
- Philip Bejon
- Kenya Medical Research Institute, Centre for Geographic Medicine Research, Kilifi, Kenya.
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Miura K, Zhou H, Diouf A, Tullo G, Moretz SE, Aebig JA, Fay MP, Miller LH, Doumbo OK, Sagara I, Dicko A, Long CA, Ellis RD. Immunological responses against Plasmodium falciparum Apical Membrane Antigen 1 vaccines vary depending on the population immunized. Vaccine 2011; 29:2255-61. [PMID: 21277408 DOI: 10.1016/j.vaccine.2011.01.043] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Revised: 12/27/2010] [Accepted: 01/16/2011] [Indexed: 11/24/2022]
Abstract
Clinical development of malaria vaccines progresses from trials in malaria naïve adults to malaria exposed adults followed by malaria exposed children. It is not well known whether immune responses in non-target populations are predictive of those in target populations, particularly in African children. Therefore humoral responses in three different populations (U.S. adults, Malian adults and Malian children) were compared in this study. They were immunized with 80 μg of Apical Membrane Antigen 1 (AMA1)/alhydrogel on days 0 and 28. Sera were collected on days 0 and 42; antibody levels were determined by ELISA and the functionality of antibodies was evaluated by Growth Inhibition Assay. After immunization, there was no significant difference in antibody levels between the Malian children and the Malian adults, but U.S. adults showed lower antibody levels. Vaccination did not significantly change growth-inhibitory activity in Malian adults, but inhibition increased significantly in both U.S. adults and Malian children. Vaccine-induced inhibitory activity was reversed by pre-incubation with AMA1 protein, but pre-existing infection-induced inhibition was not. This study shows that humoral responses elicited by the AMA1 vaccine varied depending on the population, most likely reflecting different levels of previous malaria exposure. Thus predicting immune responses from non-target populations is not desirable.
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Affiliation(s)
- Kazutoyo Miura
- Malaria Vaccine Development Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA.
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Ngoundou-Landji J, Nwuba RI, Anumudu CI, Odaibo AB, Matondo Maya WD, Awobode HO, Okafor CM, Morenikeji OA, Asinobi A, Nwagwu M, Holder AA, Ntoumi F. Fine specificity of anti-MSP119 antibodies and multiplicity of Plasmodium falciparum merozoite surface protein 1 types in individuals in Nigeria with sub-microscopic infection. Malar J 2010; 9:287. [PMID: 20955565 PMCID: PMC2965716 DOI: 10.1186/1475-2875-9-287] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2010] [Accepted: 10/18/2010] [Indexed: 12/03/2022] Open
Abstract
Background The absence of antibodies specific for the 19 kDa C-terminal domain of merozoite surface protein 1 (MSP119) has been associated with high-density malaria parasitaemia in African populations. The hypothesis that a high prevalence and/or level of anti-MSP119 antibodies that may inhibit erythrocyte invasion would be present in apparently healthy individuals who harbour a sub-microscopic malaria infection was tested in this study. Methods Plasma samples were collected from residents in a region in Nigeria hyperendemic for malaria, who had no detectable parasitaemia by microscopy. Using a competition-based enzyme-linked-immunosorbent assay with two invasion-inhibitory monoclonal antibodies (mAbs) 12.10 and 12.8, the levels and prevalence of specific antibodies were measured. The minimum multiplicity of infection was determined using PCR. The prevalence of anaemia was also measured. Results Plasma samples from 85% of individuals contained antibodies that bound to MSP119. The inhibition of mAb 12.10 binding was strongly correlated with the prevalence (Spearman correlation test, p < 0.0001) and mean titre of anti-MSP119 antibodies (Spearman correlation test, p < 0.001) in the samples. Comparing samples from individuals with multiple infection (group M) and single infection (Group S), group M contained a higher (p = 0.04) prevalence of anti-MSP119 antibodies that competed with mAb 12.10. Using a logistic regression model, it was found that the presence of antibodies competitive with mAb 12.10 was affected negatively by anaemia (p = 0.0016) and positively by the carriage of multiple parasite genotypes (p = 0.04). Conclusions In the search for correlates of protection against malaria, which will be essential to evaluate clinical trials of malaria vaccines based on MSP1, this study examines some potential assays and the factors that need to taken into account during their evaluation, using samples from individuals naturally exposed to malaria infection.
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25
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Wilson DW, Crabb BS, Beeson JG. Development of fluorescent Plasmodium falciparum for in vitro growth inhibition assays. Malar J 2010; 9:152. [PMID: 20525251 PMCID: PMC2891815 DOI: 10.1186/1475-2875-9-152] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Accepted: 06/03/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Plasmodium falciparum in vitro growth inhibition assays are widely used to evaluate and quantify the functional activity of acquired and vaccine-induced antibodies and the anti-malarial activity of known drugs and novel compounds. However, several constraints have limited the use of these assays in large-scale population studies, vaccine trials and compound screening for drug discovery and development. METHODS The D10 P. falciparum line was transfected to express green fluorescent protein (GFP). In vitro growth inhibition assays were performed over one or two cycles of P. falciparum asexual replication using inhibitory polyclonal antibodies raised in rabbits, an inhibitory monoclonal antibody, human serum samples, and anti-malarials. Parasitaemia was evaluated by microscopy and flow cytometry. RESULTS Transfected parasites expressed GFP throughout all asexual stages and were clearly detectable by flow cytometry and fluorescence microscopy. Measurement of parasite growth inhibition was the same when determined by detection of GFP fluorescence or staining with ethidium bromide. There was no difference in the inhibitory activity of samples when tested against the transfected parasites compared to the parental line. The level of fluorescence of GFP-expressing parasites increased throughout the course of asexual development. Among ring-stages, GFP-fluorescent parasites were readily separated from uninfected erythrocytes by flow cytometry, whereas this was less clear using ethidium bromide staining. Inhibition by serum and antibody samples was consistently higher when tested over two cycles of growth compared to one, and when using a 1 in 10 sample dilution compared to 1 in 20, but there was no difference detected when using a different starting parasitaemia to set-up growth assays. Flow cytometry based measurements of parasitaemia proved more reproducible than microscopy counts. CONCLUSIONS Flow cytometry based assays using GFP-fluorescent parasites proved sensitive and highly reproducible for quantifying the growth-inhibitory activity of antibodies and anti-malarials, with superior reproducibility to light microscopy, and are suitable for high-throughput applications.
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Affiliation(s)
- Danny W Wilson
- Infection and Immunity Division, the Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria, 3050, Australia
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Satoguina J, Walther B, Drakeley C, Nwakanma D, Oriero EC, Correa S, Corran P, Conway DJ, Walther M. Comparison of surveillance methods applied to a situation of low malaria prevalence at rural sites in The Gambia and Guinea Bissau. Malar J 2009; 8:274. [PMID: 19954532 PMCID: PMC2791766 DOI: 10.1186/1475-2875-8-274] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Accepted: 12/02/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Health record-based observations from several parts of Africa indicate a major decline in malaria, but up-to-date information on parasite prevalence in West-Africa is sparse. This study aims to provide parasite prevalence data from three sites in the Gambia and Guinea Bissau, respectively, and compares the usefulness of PCR, rapid diagnostic tests (RDT), serology and slide-microscopy for surveillance. METHODS Cross-sectional surveys in 12 villages at three rural sites were carried out in the Gambia and Guinea Bissau in January/February 2008, shortly following the annual transmission season. RESULTS A surprisingly low microscopically detectable parasite prevalence was detected in the Gambia (Farafenni: 10.9%, CI95%: 8.7-13.1%; Basse: 9.0%, CI95%: 7.2-10.8%), and Guinea Bissau (Caio: 4%, CI95%: 2.6-5.4%), with low parasite densities (geometric mean: 104 parasites/microl, CI95%: 76-143/microl). In comparison, PCR detected a more than three times higher proportion of parasite carriers, indicating its usefulness to sensitively identify foci where malaria declines, whereas the RDT had very low sensitivity. Estimates of force of infection using age sero-conversion rates were equivalent to an EIR of approximately 1 infectious bite/person/year, significantly less than previous estimates. The sero-prevalence profiles suggest a gradual decline of malaria transmission, confirming their usefulness in providing information on longer term trends of transmission. A greater variability in parasite prevalence among villages within a site than between sites was observed with all methods. The fact that serology equally captured the inter-village variability, indicates that the observed heterogeneity represents a stable pattern. CONCLUSION PCR and serology may be used as complementary tools to survey malaria in areas of declining malaria prevalence such as the Gambia and Guinea Bissau.
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Affiliation(s)
- Judith Satoguina
- Medical Research Council Laboratories, Fajara, PO Box 273 Banjul, The Gambia.
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Okafor CMF, Anumudu CI, Omosun YO, Uthaipibull C, Ayede I, Awobode HO, Odaibo AB, Langhorne J, Holder AA, Nwuba RI, Troye-Blomberg M. Cellular responses to modified Plasmodium falciparum MSP119 antigens in individuals previously exposed to natural malaria infection. Malar J 2009; 8:263. [PMID: 19930613 PMCID: PMC2785830 DOI: 10.1186/1475-2875-8-263] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Accepted: 11/23/2009] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND MSP1 processing-inhibitory antibodies bind to epitopes on the 19 kDa C-terminal region of the Plasmodium falciparum merozoite surface protein 1 (MSP1(19)), inhibiting erythrocyte invasion. Blocking antibodies also bind to this antigen but prevent inhibitory antibodies binding, allowing invasion to proceed. Recombinant MSP1(19) had been modified previously to allow inhibitory but not blocking antibodies to continue to bind. Immunization with these modified proteins, therefore, has the potential to induce more effective protective antibodies. However, it was unclear whether the modification of MSP1(19) would affect critical T-cell responses to epitopes in this antigen. METHODS The cellular responses to wild-type MSP1(19) and a panel of modified MSP1(19) antigens were measured using an in-vitro assay for two groups of individuals: the first were malaria-naïve and the second had been naturally exposed to Plasmodium falciparum infection. The cellular responses to the modified proteins were examined using cells from malaria-exposed infants and adults. RESULTS Interestingly, stimulation indices (SI) for responses induced by some of the modified proteins were at least two-fold higher than those elicited by the wild-type MSP1(19). A protein with four amino acid substitutions (Glu27-->Tyr, Leu31-->Arg, Tyr34-->Ser and Glu43-->Leu) had the highest stimulation index (SI up to 360) and induced large responses in 64% of the samples that had significant cellular responses to the modified proteins. CONCLUSION This study suggests that specific MSP1(19) variants that have been engineered to improve their antigenicity for inhibitory antibodies, retain T-cell epitopes and the ability to induce cellular responses. These proteins are candidates for the development of MSP1-based malaria vaccines.
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Affiliation(s)
- Christian MF Okafor
- Cellular Parasitology Programme, Department of Zoology University of Ibadan, Ibadan, Nigeria
- College of Art and Sciences, Northwest University, 5520, 108th Ave. NE, Kirkland WA 98033, USA
| | - Chiaka I Anumudu
- Cellular Parasitology Programme, Department of Zoology University of Ibadan, Ibadan, Nigeria
| | - Yusuf O Omosun
- Cellular Parasitology Programme, Department of Zoology University of Ibadan, Ibadan, Nigeria
- Department of Biotechnology, Bells University of Technology, Sango-Otta, Nigeria
| | - Chairat Uthaipibull
- Division of Parasitology, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
- Protein-Ligand Engineering and Molecular Biology Laboratory, National Center for Genetic Engineering and Biotechnology (BIOTEC), Thailand Science Park, Pathumthani, Thailand
| | - Idowu Ayede
- Oni Memorial Children's Hospital, Ring Road, Ibadan, Nigeria
| | - Henrietta O Awobode
- Cellular Parasitology Programme, Department of Zoology University of Ibadan, Ibadan, Nigeria
| | - Alex B Odaibo
- Cellular Parasitology Programme, Department of Zoology University of Ibadan, Ibadan, Nigeria
| | - Jean Langhorne
- Division of Parasitology, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
| | - Anthony A Holder
- Division of Parasitology, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
| | - Roseangela I Nwuba
- Cellular Parasitology Programme, Department of Zoology University of Ibadan, Ibadan, Nigeria
| | - Marita Troye-Blomberg
- Department of Immunology, Wenner-Gren Institute, Arrhenius Laboratories, Stockholm University, Stockholm, Sweden
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Plasmodium falciparum merozoite surface protein 1 (MSP-1)-MSP-3 chimeric protein: immunogenicity determined with human-compatible adjuvants and induction of protective immune response. Infect Immun 2009; 78:872-83. [PMID: 19933832 DOI: 10.1128/iai.00427-09] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A chimeric gene, MSP-Fu(24), was constructed by genetically coupling immunodominant, conserved regions of the two leading malaria vaccine candidates, Plasmodium falciparum merozoite surface protein 1 (C-terminal 19-kDa region [PfMSP-1(19)]) and merozoite surface protein 3 (11-kDa conserved region [PfMSP-3(11)]). The recombinant MSP-Fu(24) protein was produced in Escherichia coli cells and purified to homogeneity by a two-step purification process with a yield of approximately 30 mg/liter. Analyses of conformational properties of MSP-Fu(24) using PfMSP-1(19)-specific monoclonal antibody showed that the conformational epitopes of PfMSP-1(19) that may be critical for the generation of the antiparasitic immune response remained intact in the fusion protein. Recombinant MSP-Fu(24) was highly immunogenic in mice and in rabbits when formulated with two different human-compatible adjuvants and induced an immune response against both PfMSP-1(19) and PfMSP-3(11). Purified anti-MSP-Fu(24) antibodies showed invasion inhibition of P. falciparum 3D7 and FCR parasites, and this effect was found to be dependent on antibodies specific for the PfMSP-1(19) component. The protective potential of MSP-Fu(24) was demonstrated by in vitro parasite growth inhibition using an antibody-dependent cell inhibition (ADCI) assay with anti-MSP-Fu(24) antibodies. Overall, the antiparasitic activity was mediated by a combination of growth-inhibitory antibodies generated by both the PfMSP-1(19) and PfMSP-3(11) components of the MSP-Fu(24) protein. The antiparasitic activities elicited by anti-MSP-Fu(24) antibodies were comparable to those elicited by antibodies generated with immunization with a physical mixture of two component antigens, PfMSP-1(19) and PfMSP-3(11). The fusion protein induces a protective immune response with human-compatible adjuvants and may form a part of a multicomponent malaria vaccine.
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In vitro growth-inhibitory activity and malaria risk in a cohort study in mali. Infect Immun 2009; 78:737-45. [PMID: 19917712 DOI: 10.1128/iai.00960-09] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Immunity to the asexual blood stage of Plasmodium falciparum is complex and likely involves several effector mechanisms. Antibodies are thought to play a critical role in malaria immunity, and a corresponding in vitro correlate of antibody-mediated immunity has long been sought to facilitate malaria vaccine development. The growth inhibition assay (GIA) measures the capacity of antibodies to limit red blood cell (RBC) invasion and/or growth of P. falciparum in vitro. In humans, naturally acquired and vaccine-induced P. falciparum-specific antibodies have growth-inhibitory activity, but it is unclear if growth-inhibitory activity correlates with protection from clinical disease. In a longitudinal study in Mali, purified IgGs, obtained from plasmas collected before the malaria season from 220 individuals aged 2 to 10 and 18 to 25 years, were assayed for growth-inhibitory activity. Malaria episodes were recorded by passive surveillance over the subsequent 6-month malaria season. Logistic regression showed that greater age (odds ratio [OR], 0.78; 95% confidence interval [95% CI], 0.63 to 0.95; P = 0.02) and growth-inhibitory activity (OR, 0.50; 95% CI, 0.30 to 0.85; P = 0.01) were significantly associated with decreased malaria risk in children. A growth-inhibitory activity level of 40% was determined to be the optimal cutoff for discriminating malaria-immune and susceptible individuals in this cohort, with a sensitivity of 97.0%, but a low specificity of 24.3%, which limited the assay's ability to accurately predict protective immunity and to serve as an in vitro correlate of antibody-mediated immunity. These data suggest that antibodies which block merozoite invasion of RBC and/or inhibit the intra-RBC growth of the parasite contribute to but are not sufficient for the acquisition of malaria immunity.
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Growth-inhibitory antibodies are not necessary for protective immunity to malaria infection. Infect Immun 2009; 78:680-7. [PMID: 19917716 DOI: 10.1128/iai.00939-09] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The absence of a validated surrogate marker for the immune state has complicated the design of a subunit vaccine against asexual stages of Plasmodium falciparum. In particular, it is not known whether the capacity to induce antibodies that inhibit parasite growth in vitro is an important criterion for selection of P. falciparum proteins to be assessed in human vaccine trials. We examined this issue in the Plasmodium yoelii rodent malaria model using the 19-kDa C-terminal fragment of merozoite surface protein 1 (MSP1(19)). To examine the relationship between inhibitory antibodies in immunized mice and the immune state, as indicated by resistance to a blood-stage challenge, we used an allelic replacement strategy to generate a transgenic P. falciparum line that expresses MSP1(19) from P. yoelii. We show that MSP1(19) is functionally conserved across these two divergent Plasmodium species, and replacing PfMSP1(19) with PyMSP1(19) has no detectable effect on parasite growth in vitro. By comparing growth rates of this transgenic line with a matched transgenic line that expresses the endogenous PfMSP1(19), we developed an assay to measure the specific growth-inhibitory activity directed exclusively to the PyMSP1(19) protein in the sera from vaccinated animals. To validate this assay, sera from rabbits immunized with recombinant PyMSP1(19) were tested and showed specific inhibitory activity in a concentration-dependent manner. In mice that were immunized with recombinant PyMSP1(19), the levels of PyMSP1(19)-specific inhibitory activity did not correlate with the total antibody levels measured by enzyme-linked immunosorbent assay. Furthermore, they did not correlate with resistance to subsequent blood-stage infection, and some mice with complete protection showed no detectable inhibitory activity in their prechallenge sera. These data indicated that growth-inhibitory activity measured in vitro was not a reliable predictor of immune status in vivo, and the reliance on this criterion to select vaccine candidates for human clinical trials may be misplaced. The transgenic lines further offer useful tools for comparing the efficacy of MSP1(19)-based vaccines that utilize different immunization regimens and antigen formulations.
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Kinyanjui SM, Bejon P, Osier FH, Bull PC, Marsh K. What you see is not what you get: implications of the brevity of antibody responses to malaria antigens and transmission heterogeneity in longitudinal studies of malaria immunity. Malar J 2009; 8:242. [PMID: 19860926 PMCID: PMC2773787 DOI: 10.1186/1475-2875-8-242] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Accepted: 10/28/2009] [Indexed: 11/18/2022] Open
Abstract
Background A major handicap in developing a malaria vaccine is the difficulty in pinpointing the immune responses that protect against malaria. The protective efficacy of natural or vaccine-induced immune responses against malaria is normally assessed by relating the level of the responses in an individual at the beginning of a follow-up period and the individual's experience of malaria infection or disease during the follow-up. This approach has identified a number of important responses against malaria, but their protective efficacies vary considerably between studies. Hypothesis It is likely that apart from differences in study methodologies, differences in exposure among study subjects within each study and brevity of antibody responses to malaria antigen are important sources of the variation in protective efficacy of anti-malaria immune responses mentioned above. Since malaria immunity is not complete, anyone in an area of stable malaria transmission who does not become asymptomatically or symptomatically infected during follow-up subsequent to treatment is most likely unexposed rather than immune. Testing the hypothesis It is proposed that individuals involved in a longitudinal study of malaria immunity should be treated for malaria prior to the start of the study and only those who present with at least an asymptomatic infection during the follow-up should be included in the analysis. In addition, it is proposed that more closely repeated serological survey should be carried out during follow-up in order to get a better picture of an individual's serological status. Implications of the hypothesis Failure to distinguish between individuals who do not get a clinical episode during follow-up because they were unexposed and those who are genuinely immune undermines our ability to assign a protective role to immune responses against malaria. The brevity of antibodies responses makes it difficult to assign the true serological status of an individual at any given time, i.e. those positive at a survey may be negative by the time they encounter the next infection.
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Affiliation(s)
- Samson M Kinyanjui
- Kenyan Medical Research Institute (KEMRI), Centre for Geographic Medicine Research (Coast), PO Box 230, Kilifi 80108, Kenya.
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Courtin D, Oesterholt M, Huismans H, Kusi K, Milet J, Badaut C, Gaye O, Roeffen W, Remarque EJ, Sauerwein R, Garcia A, Luty AJF. The quantity and quality of African children's IgG responses to merozoite surface antigens reflect protection against Plasmodium falciparum malaria. PLoS One 2009; 4:e7590. [PMID: 19859562 PMCID: PMC2763201 DOI: 10.1371/journal.pone.0007590] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2009] [Accepted: 10/01/2009] [Indexed: 11/20/2022] Open
Abstract
Background Antibodies, particularly cytophilic IgG subclasses, with specificity for asexual blood stage antigens of Plasmodium falciparum, are thought to play an important role in acquired immunity to malaria. Evaluating such responses in longitudinal sero-epidemiological field studies, allied to increasing knowledge of the immunological mechanisms associated with anti-malarial protection, will help in the development of malaria vaccines. Methods and Findings We conducted a 1-year follow-up study of 305 Senegalese children and identified those resistant or susceptible to malaria. In retrospective analyses we then compared post-follow-up IgG responses to six asexual-stage candidate malaria vaccine antigens in groups of individuals with clearly defined clinical and parasitological histories of infection with P. falciparum. In age-adjusted analyses, children resistant to malaria as well as to high-density parasitemia, had significantly higher IgG1 responses to GLURP and IgG3 responses to MSP2 than their susceptible counterparts. Among those resistant to malaria, high anti-MSP1 IgG1 levels were associated with protection against high-density parasitemia. To assess functional attributes, we used an in vitro parasite growth inhibition assay with purified IgG. Samples from individuals with high levels of IgG directed to MSP1, MSP2 and AMA1 gave the strongest parasite growth inhibition, but a marked age-related decline was observed in these effects. Conclusion Our data are consistent with the idea that protection against P. falciparum malaria in children depends on acquisition of a constellation of appropriate, functionally active IgG subclass responses directed to multiple asexual stage antigens. Our results suggest at least two distinct mechanisms via which antibodies may exert protective effects. Although declining with age, the growth inhibitory effects of purified IgG measurable in vitro reflected levels of anti-AMA1, -MSP1 and -MSP2, but not of anti-GLURP IgG. The latter could act on parasite growth via indirect parasiticidal pathways.
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Affiliation(s)
- David Courtin
- Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
- Unité de Recherche (UR) 010 « Santé de la mère et de l'enfant en milieu tropical », Institut de Recherche pour le Développement, Université Paris Descartes, Paris, France
| | - Mayke Oesterholt
- Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Harm Huismans
- Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Kwadwo Kusi
- Department of Parasitology, Biomedical Primate Research Centre, Rijswijk, The Netherlands
| | - Jacqueline Milet
- Unité de Recherche (UR) 010 « Santé de la mère et de l'enfant en milieu tropical », Institut de Recherche pour le Développement, Université Paris Descartes, Paris, France
| | - Cyril Badaut
- Unité de Recherche (UR) 010 « Santé de la mère et de l'enfant en milieu tropical », Institut de Recherche pour le Développement, Université Paris Descartes, Paris, France
| | - Oumar Gaye
- Laboratoire de Parasitologie et de Mycologie, Département de Biologie et d'Explorations fonctionnelles, Faculté de Médecine, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Will Roeffen
- Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Edmond J. Remarque
- Department of Parasitology, Biomedical Primate Research Centre, Rijswijk, The Netherlands
| | - Robert Sauerwein
- Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - André Garcia
- Unité de Recherche (UR) 010 « Santé de la mère et de l'enfant en milieu tropical », Institut de Recherche pour le Développement, Université Paris Descartes, Paris, France
| | - Adrian J. F. Luty
- Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
- * E-mail:
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Abstract
Naturally acquired immunity to malaria requires repeat infections yet does not engender sterile immunity or long-lasting protective immunologic memory. This renders infants and young children the most susceptible to malaria-induced morbidity and mortality, and the ultimate target for a malaria vaccine. The prevailing paradigm is that infants initially garner protection due to transplacentally transferred anti-malarial antibodies and other intrinsic factors such as foetal haemoglobin. As these wane infants have an insufficient immune repertoire to prevent genetically diverse Plasmodium infections and an inability to control malaria-induced immunopathology. This Review discusses humoral, cell-mediated and innate immune responses to malaria and how each contributes to protection – focusing on how deficiencies in infant and paediatric immune responses might influence malaria vaccine efficacy in this population. In addition, burgeoning evidence suggests a role for inhibitory receptors that limit immunopathology and guide the development of long-lived immunity. Precisely how age or malaria infections influence the function of these regulators is unknown. Therefore the possibility that infants may not have the immune-dexterity to balance effective parasite clearance with timely immune-regulation leading to protective immunologic memory is considered. And thus, malaria vaccines tested in adults and older children may not be predictive for trials conducted in infants.
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Affiliation(s)
- A M Moormann
- Case Western Reserve University, Center for Global Health and Diseases, 2103 Cornell Road, WRB 4-130, Cleveland, OH 44106-7286, USA.
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Cao Y, Zhang D, Pan W. Construction of transgenic Plasmodium berghei as a model for evaluation of blood-stage vaccine candidate of Plasmodium falciparum chimeric protein 2.9. PLoS One 2009; 4:e6894. [PMID: 19727400 PMCID: PMC2731880 DOI: 10.1371/journal.pone.0006894] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2009] [Accepted: 07/14/2009] [Indexed: 11/25/2022] Open
Abstract
Background The function of the 19 kDa C-terminal region of the merozoite surface protein 1 (MSP1-19) expressed by Plasmodium has been demonstrated to be conserved across distantly related Plasmodium species. The green fluorescent protein (GFP) is a reporter protein that has been widely used because it can be easily detected in living organisms by fluorescence microscopy and flow cytometry. Methodology and Results In this study, we used gene targeting to generate transgenic P. berghei (Pb) parasites (designated as PfMSP1-19Pb) that express the MSP1-19 of P. falciparum (Pf) and the GFP reporter protein simultaneously. The replacement of the PbMSP1-19 locus by PfMSP1-19 was verified by PCR and Southern analysis. The expression of the chimeric PbfMSP-1 and the GFP was verified by Western blot and fluorescence microscopy, respectively. Moreover, GFP-expressing transgenic parasites in blood stages can be readily differentiated from other blood cells using flow cytometry. A comparion of growth rates between wild-type and the PfMSP1-19Pb transgenic parasite indicated that the replacement of the MSP1-19 region and the expression of the GFP protein were not deleterious to the transgenic parasites. We used this transgenic mouse parasite as a murine model to evaluate the protective efficacy in vivo of specific IgG elicited by a PfCP-2.9 malaria vaccine that contains the PfMSP1-19. The BALB/c mice passively transferred with purified rabbit IgG to the PfCP-2.9 survived a lethal challenge of the PfMSP1-19Pb transgenic murine parasites, but not the wild-type P. berghei whereas the control mice passively transferred with purified IgG obtained from adjuvant only-immunized rabbits were vulnerable to both transgenic and wild-type infections. Conclusions We generated a transgenic P. berghei line that expresses PfMSP1-19 and the GFP reporter gene simultaneously. The availability of this parasite line provides a murine model to evaluate the protective efficacy in vivo of anti-MSP1-19 antibodies, including, potentially, those elicited by the PfCP-2.9 malaria vaccine in human volunteers.
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Affiliation(s)
- Yi Cao
- Department of Pathogen Biology, Second Military Medical University, Shanghai, China
| | - Dongmei Zhang
- Department of Pathogen Biology, Second Military Medical University, Shanghai, China
| | - Weiqing Pan
- Department of Pathogen Biology, Second Military Medical University, Shanghai, China
- * E-mail:
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The carboxy-terminus of merozoite surface protein 1: structure, specific antibodies and immunity to malaria. Parasitology 2009; 136:1445-56. [PMID: 19627632 DOI: 10.1017/s0031182009990515] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
SUMMARYOver the last 30 years, evidence has been gathered suggesting that merozoite surface protein 1 (MSP1) is a target of protective immunity against malaria. In a variety of experimental approaches usingin vitromethodology, animal models and sero-epidemiological techniques, the importance of antibody against MSP1 has been established but we are still finding out what are the mechanisms involved. Now that clinical trials of MSP1 vaccines are underway and the early results have been disappointing, it is increasingly clear that we need to know more about the mechanisms of immunity, because a better understanding will highlight the limitations of our current assays and identify the improvements required. Understanding the structure of MSP1 will help us design and engineer better antigens that are more effective than the first generation of vaccine candidates. This review is focused on the carboxy-terminus of MSP1.
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Inhibitory antibodies specific for the 19-kilodalton fragment of merozoite surface protein 1 do not correlate with delayed appearance of infection with Plasmodium falciparum in semi-immune individuals in Vietnam. Infect Immun 2009; 77:4510-7. [PMID: 19620342 DOI: 10.1128/iai.00360-09] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Inhibitory antibodies specific for the 19-kDa fragment of merozoite surface protein 1 (MSP1(19)) are a significant component of inhibitory responses in individuals immune to malaria. Nevertheless, conflicting results have been obtained in determining whether this antibody specificity correlates with protection in residents of areas where malaria is endemic. In this study, we examined sera collected from a population of semi-immune individuals living in an area of Vietnam with meso-endemicity during a 6-month period. We used two Plasmodium falciparum parasite lines that express either endogenous MSP1(19) or the homologous region from Plasmodium yoelii to measure the MSP1(19)-specific inhibitory activity. We showed that (i) the level of MSP1(19)-specific inhibitory antibodies was not associated with a delay in P. falciparum infection, (ii) MSP1(19)-specific inhibitory antibodies declined significantly during the convalescent period after infection, and (iii) there was no significant correlation between the MSP1(19)-specific inhibitory antibodies and the total antibodies measured by enzyme-linked immunosorbent assay. These results have implications for understanding naturally acquired immunity to malaria and for the development and evaluation of MSP1(19)-based vaccines.
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Coppel RL. Vaccinating with the genome: a Sisyphean task? Trends Parasitol 2009; 25:205-12. [PMID: 19359219 DOI: 10.1016/j.pt.2009.02.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2008] [Revised: 01/27/2009] [Accepted: 02/09/2009] [Indexed: 11/24/2022]
Abstract
Human trials of subunit vaccines against the asexual blood stage of malaria are yielding disappointing results, supporting the premise that a single recombinant protein will not be particularly efficacious and that additional proteins must be added. The genome sequence of Plasmodium falciparum offers a large number of additional candidates, but which should be chosen? Various criteria have been suggested to rank the additional candidates, but in the absence of even a partially effective asexual-stage vaccine, the criteria remain unvalidated. These issues are discussed here, together with some suggestions as to how the development of an asexual-stage vaccine could be progressed.
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Affiliation(s)
- Ross L Coppel
- Department of Microbiology, Monash University, Clayton, Victoria 3800, Australia.
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Ogutu BR, Apollo OJ, McKinney D, Okoth W, Siangla J, Dubovsky F, Tucker K, Waitumbi JN, Diggs C, Wittes J, Malkin E, Leach A, Soisson LA, Milman JB, Otieno L, Holland CA, Polhemus M, Remich SA, Ockenhouse CF, Cohen J, Ballou WR, Martin SK, Angov E, Stewart VA, Lyon JA, Heppner DG, Withers MR. Blood stage malaria vaccine eliciting high antigen-specific antibody concentrations confers no protection to young children in Western Kenya. PLoS One 2009; 4:e4708. [PMID: 19262754 PMCID: PMC2650803 DOI: 10.1371/journal.pone.0004708] [Citation(s) in RCA: 224] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Accepted: 01/05/2009] [Indexed: 11/19/2022] Open
Abstract
Objective The antigen, falciparum malaria protein 1 (FMP1), represents the 42-kDa C-terminal fragment of merozoite surface protein-1 (MSP-1) of the 3D7 clone of P. falciparum. Formulated with AS02 (a proprietary Adjuvant System), it constitutes the FMP1/AS02 candidate malaria vaccine. We evaluated this vaccine's safety, immunogenicity, and efficacy in African children. Methods A randomised, double-blind, Phase IIb, comparator-controlled trial.The trial was conducted in 13 field stations of one mile radii within Kombewa Division, Nyanza Province, Western Kenya, an area of holoendemic transmission of P. falciparum. We enrolled 400 children aged 12–47 months in general good health.Children were randomised in a 1∶1 fashion to receive either FMP1/AS02 (50 µg) or Rabipur® rabies vaccine. Vaccinations were administered on a 0, 1, and 2 month schedule. The primary study endpoint was time to first clinical episode of P. falciparum malaria (temperature ≥37.5°C with asexual parasitaemia of ≥50,000 parasites/µL of blood) occurring between 14 days and six months after a third dose. Case detection was both active and passive. Safety and immunogenicity were evaluated for eight months after first immunisations; vaccine efficacy (VE) was measured over a six-month period following third vaccinations. Results 374 of 400 children received all three doses and completed six months of follow-up. FMP1/AS02 had a good safety profile and was well-tolerated but more reactogenic than the comparator. Geometric mean anti-MSP-142 antibody concentrations increased from1.3 µg/mL to 27.3 µg/mL in the FMP1/AS02 recipients, but were unchanged in controls. 97 children in the FMP1/AS02 group and 98 controls had a primary endpoint episode. Overall VE was 5.1% (95% CI: −26% to +28%; p-value = 0.7). Conclusions FMP1/AS02 is not a promising candidate for further development as a monovalent malaria vaccine. Future MSP-142 vaccine development should focus on other formulations and antigen constructs. Trial Registration Clinicaltrials.gov NCT00223990
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Affiliation(s)
- Bernhards R Ogutu
- US Army Medical Research Unit-Kenya and the Centre for Clinical Research, Kenya Medical Research Institute, Nairobi, Kenya.
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Omosun YO, Adoro S, Anumudu CI, Odaibo AB, Uthiapibull C, Holder AA, Nwagwu M, Nwuba RI. Antibody specificities of children living in a malaria endemic area to inhibitory and blocking epitopes on MSP-1 19 of Plasmodium falciparum. Acta Trop 2009; 109:208-12. [PMID: 19081386 DOI: 10.1016/j.actatropica.2008.11.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2007] [Revised: 08/21/2008] [Accepted: 11/14/2008] [Indexed: 11/18/2022]
Abstract
Merozoite surface protein-1(19) (MSP-1(19)) specific antibodies which include processing inhibitory, blocking and neutral antibodies have been identified in individuals exposed to Plasmodium falciparum. Here we intend to look at the effect of single and multiple amino acid substitutions of MSP-1(19) on the recognition by polyclonal antibodies from children living in Igbo-Ora, Nigeria. This would provide us with information on the possibility of eliciting mainly processing inhibitory antibodies with a recombinant MSP-1(19) vaccine. Blood was collected from children in the rainy season and binding of anti-MSP-1(19) antibodies to modified mutants of MSP-1(19) was analysed by ELISA. The MSP-1(19) mutant proteins with single substitutions at positions 22 (Leu-->Arg), 43 (Glu-->Leu) and 53 (Asn-->Arg) and the MSP-1(19) mutant protein with multiple substitutions at positions 27+31+34+43 (Glu-->Tyr, Leu-->Arg, Tyr-->Ser, Glu-->Leu); which had inhibitory epitopes; had the highest recognition. Children recognised both sets of mutants with different age groups having different recognition levels. The percentage of malaria positive individuals (32-80%) with antibodies that bound to the mutants MSP-1(19) containing epitopes that recognise only processing inhibitory and not blocking antibodies, were significantly different from those with antibodies that did not bind to these mutants (21-28%). The amino acid substitutions that abolished the binding of blocking antibodies without affecting the binding of inhibitory antibodies are of particular interest in the design of MSP-1(19) based malaria vaccines. Although these MSP-1(19) mutants have not been found in natural population, their recognition by polyclonal antibodies from humans naturally infected with malaria is very promising for the future use of MSP-1(19) mutants in the design of a malaria vaccine.
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Affiliation(s)
- Y O Omosun
- Cellular Parasitology Programme, Department of Zoology, University of Ibadan, Ibadan, Oyo State, Nigeria.
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Reed ZH, Kieny MP, Engers H, Friede M, Chang S, Longacre S, Malhotra P, Pan W, Long C. Comparison of immunogenicity of five MSP1-based malaria vaccine candidate antigens in rabbits. Vaccine 2009; 27:1651-60. [DOI: 10.1016/j.vaccine.2008.10.093] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2006] [Revised: 10/21/2008] [Accepted: 10/27/2008] [Indexed: 10/21/2022]
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Murhandarwati E, Black C, Wang L, Weisman S, Koning‐Ward T, Baird J, Tjitra E, Richie T, Crabb B, Coppel R. Acquisition of Invasion‐Inhibitory Antibodies Specific for the 19‐kDa Fragment of Merozoite Surface Protein 1 in a Transmigrant Population Requires Multiple Infections. J Infect Dis 2008; 198:1212-8. [DOI: 10.1086/591943] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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Ghumra A, Semblat JP, McIntosh RS, Raza A, Rasmussen IB, Braathen R, Johansen FE, Sandlie I, Mongini PK, Rowe JA, Pleass RJ. Identification of residues in the Cmu4 domain of polymeric IgM essential for interaction with Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1). THE JOURNAL OF IMMUNOLOGY 2008; 181:1988-2000. [PMID: 18641336 DOI: 10.4049/jimmunol.181.3.1988] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The binding of nonspecific human IgM to the surface of infected erythrocytes is important in rosetting, a major virulence factor in the pathogenesis of severe malaria due to Plasmodium falciparum, and IgM binding has also been implicated in placental malaria. Herein we have identified the IgM-binding parasite ligand from a virulent P. falciparum strain as PfEMP1 (TM284var1 variant), and localized the region within this PfEMP1 variant that binds IgM (DBL4beta domain). We have used this parasite IgM-binding protein to investigate the interaction with human IgM. Interaction studies with domain-swapped Abs, IgM mutants, and anti-IgM mAbs showed that PfEMP1 binds to the Fc portion of the human IgM H chain and requires the IgM Cmu4 domain. Polymerization of IgM was shown to be crucial for the interaction because PfEMP1 binding did not occur with mutant monomeric IgM molecules. These results with PfEMP1 protein have physiological relevance because infected erythrocytes from strain TM284 and four other IgM-binding P. falciparum strains showed analogous results to those seen with the DBL4beta domain. Detailed investigation of the PfEMP1 binding site on IgM showed that some of the critical amino acids in the IgM Cmu4 domain are equivalent to those regions of IgG and IgA recognized by Fc-binding proteins from bacteria, suggesting that this region of Ig molecules may be of major functional significance in host-microbe interactions. We have therefore shown that PfEMP1 is an Fc-binding protein of malaria parasites specific for polymeric human IgM, and that it shows functional similarities with Fc-binding proteins from pathogenic bacteria.
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Affiliation(s)
- Ashfaq Ghumra
- Institute of Genetics, Queens Medical Centre, University of Nottingham, Nottingham, England, United Kingdom
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Dodoo D, Aikins A, Kusi KA, Lamptey H, Remarque E, Milligan P, Bosomprah S, Chilengi R, Osei YD, Akanmori BD, Theisen M. Cohort study of the association of antibody levels to AMA1, MSP119, MSP3 and GLURP with protection from clinical malaria in Ghanaian children. Malar J 2008; 7:142. [PMID: 18664257 PMCID: PMC2529305 DOI: 10.1186/1475-2875-7-142] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2008] [Accepted: 07/29/2008] [Indexed: 11/24/2022] Open
Abstract
Background Antigen-specific antibody-mediated immune responses play an important role in natural protection against clinical malaria, but conflicting estimates of this association have emerged from immuno-epidemiological studies in different geographical settings. This study was aimed at assessing in a standardized manner the relationship between the antibody responses to four malaria vaccine candidate antigens and protection from clinical malaria, in a cohort of Ghanaian children. Methods Standardized ELISA protocols were used to measure isotype and IgG subclass levels to Apical Membrane Antigen 1 (AMA1), Merozoite Surface Protein 1–19 (MSP119), Merozoite Surface Protein 3 (MSP3) and Glutamate Rich Protein (GLURP) antigens in plasma samples from 352 Ghanaian children, aged three to 10 years with subsequent malaria surveillance for nine months. This is one of a series of studies in different epidemiological settings using the same standardized ELISA protocols to permit comparisons of results from different laboratories. Results The incidence rate of malaria was 0.35 episodes per child per year. Isotype and IgG subclasses for all antigens investigated increased with age, while the risk of malaria decreased with age. After adjusting for age, higher levels of IgG to GLURP, MSP119, MSP3 and IgM to MSP119, MSP3 and AMA1 were associated with decreased malaria incidence. Of the IgG subclasses, only IgG1 to MSP119 was associated with reduced incidence of clinical malaria. A previous study in the same location failed to find an association of antibodies to MSP119 with clinical malaria. The disagreement may be due to differences in reagents, ELISA and analytical procedures used in the two studies. When IgG, IgM and IgG subclass levels for all four antigens were included in a combined model, only IgG1 [(0.80 (0.67–0.97), p = 0.018)] and IgM [(0.48 (0.32–0.72), p < 0.001)] to MSP119 were independently associated with protection from malaria. Conclusion Using standardized procedures, the study has confirmed the importance of antibodies to MSP119 in reducing the risk of clinical malaria in Ghanaian children, thus substantiating its potential as a malaria vaccine candidate.
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Affiliation(s)
- Daniel Dodoo
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana.
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Breadth and magnitude of antibody responses to multiple Plasmodium falciparum merozoite antigens are associated with protection from clinical malaria. Infect Immun 2008; 76:2240-8. [PMID: 18316390 DOI: 10.1128/iai.01585-07] [Citation(s) in RCA: 300] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Individuals living in areas where malaria is endemic are repeatedly exposed to many different malaria parasite antigens. Studies on naturally acquired antibody-mediated immunity to clinical malaria have largely focused on the presence of responses to individual antigens and their associations with decreased morbidity. We hypothesized that the breadth (number of important targets to which antibodies were made) and magnitude (antibody level measured in a random serum sample) of the antibody response were important predictors of protection from clinical malaria. We analyzed naturally acquired antibodies to five leading Plasmodium falciparum merozoite-stage vaccine candidate antigens, and schizont extract, in Kenyan children monitored for uncomplicated malaria for 6 months (n = 119). Serum antibody levels to apical membrane antigen 1 (AMA1) and merozoite surface protein antigens (MSP-1 block 2, MSP-2, and MSP-3) were inversely related to the probability of developing malaria, but levels to MSP-1(19) and erythrocyte binding antigen (EBA-175) were not. The risk of malaria was also inversely associated with increasing breadth of antibody specificities, with none of the children who simultaneously had high antibody levels to five or more antigens experiencing a clinical episode (17/119; 15%; P = 0.0006). Particular combinations of antibodies (AMA1, MSP-2, and MSP-3) were more strongly predictive of protection than others. The results were validated in a larger, separate case-control study whose end point was malaria severe enough to warrant hospital admission (n = 387). These findings suggest that under natural exposure, immunity to malaria may result from high titers antibodies to multiple antigenic targets and support the idea of testing combination blood-stage vaccines optimized to induce similar antibody profiles.
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Eisen DP, Wang L, Jouin H, Murhandarwati EEH, Black CG, Mercereau-Puijalon O, Coppel RL. Antibodies elicited in adults by a primary Plasmodium falciparum blood-stage infection recognize different epitopes compared with immune individuals. Malar J 2007; 6:86. [PMID: 17605823 PMCID: PMC1924525 DOI: 10.1186/1475-2875-6-86] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Accepted: 07/02/2007] [Indexed: 11/22/2022] Open
Abstract
Background Asexual stage antibody responses following initial Plasmodium falciparum infections in previously healthy adults may inform vaccine development, yet these have not been as intensively studied as they have in populations from malaria-endemic areas. Methods Serum samples were collected over a six-month period from twenty travellers having returned with falciparum malaria. Fourteen of these were malaria-naïve and six had a past history of one to two episodes of malaria. Antibodies to seven asexual stage P. falciparum antigens were measured by ELISA. Invasion inhibitory antibody responses to the 19kDa fragment of merozoite surface protein 1 (MSP119) were determined. Results Short-lived antibody responses were found in the majority of the subjects. While MSP119 antibodies were most common, MSP1 block 2 antibodies were significantly less frequent and recognized conserved domains. Antibodies to MSP2 cross-reacted to the dimorphic allelic families and anti-MSP2 isotypes were not IgG3 skewed as shown previously. MSP119 invasion inhibiting antibodies were present in 9/20 patients. A past history of malaria did not influence the frequency of these short-lived, functional antibodies (p = 0.2, 2-tailed Fisher's exact test). Conclusion Adults infected with P. falciparum for the first time, develop relatively short-lived immune responses that, in the case of MSP119, are functional. Antibodies to the polymorphic antigens studied were particularly directed to allelic family specific, non-repetitive and conserved determinants and were not IgG subclass skewed. These responses are substantially different to those found in malaria immune individuals.
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Affiliation(s)
- Damon P Eisen
- Clinical Centre for Research Excellence in Infectious Diseases, Victorian Infectious Diseases Service, Royal Melbourne Hospital, Grattan St, Parkville, Victoria, 3050, Australia
- Malaria and Scabies Unit, Queensland Institute of Medical Research, Herston, Queensland, 4029, Australia
| | - Lina Wang
- Department of Microbiology, Monash University, Clayton, Victoria, 3800, Australia
| | - Helene Jouin
- Unite d'Immunologie Moléculaire des Parasites, Institut Pasteur, Paris, France
| | | | - Casilda G Black
- Department of Microbiology, Monash University, Clayton, Victoria, 3800, Australia
| | | | - Ross L Coppel
- Department of Microbiology, Monash University, Clayton, Victoria, 3800, Australia
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Babon JJ, Morgan WD, Kelly G, Eccleston JF, Feeney J, Holder AA. Structural studies on Plasmodium vivax merozoite surface protein-1. Mol Biochem Parasitol 2007; 153:31-40. [PMID: 17343930 DOI: 10.1016/j.molbiopara.2007.01.015] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2006] [Revised: 01/17/2007] [Accepted: 01/17/2007] [Indexed: 11/28/2022]
Abstract
Plasmodium vivax infection is the second most common cause of malaria throughout the world. Like other Plasmodium species, P. vivax has a large protein complex, MSP-1, located on the merozoite surface. The C-terminal MSP-1 sub-unit, MSP-1(42), is cleaved during red blood cell invasion, causing the majority of the complex to be shed and leaving only a small 15kDa sub-unit, MSP-1(19), on the merozite surface. MSP-1(19) is considered a strong vaccine candidate. We have determined the solution structure of MSP-1(19) from P. vivax using nuclear magnetic resonance (NMR) and show that, like in other Plasmodium species, it consists of two EGF-like domains that are oriented head-to-tail. The protein has a flat, disk-like shape with a highly charged surface. When MSP-1(19) is part of the larger MSP-1(42) precursor it exists as an independent domain with no stable contacts to the rest of the sub-unit. Gel filtration and analytical ultracentrifugation experiments indicate that P. vivax MSP-1(42) exists as a dimer in solution. MSP-1(19) itself is a monomer, however, 35 amino-acids immediately upstream of its N-terminus are sufficient to cause dimerization. Our data suggest that if MSP-1(42) exists as a dimer in vivo, secondary processing would cause the dissociation of two tightly linked MSP-1(19) proteins on the merozoite surface just prior to invasion.
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Affiliation(s)
- Jeffrey J Babon
- Division of Parasitology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom.
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Lusingu JPA, Jensen ATR, Vestergaard LS, Minja DT, Dalgaard MB, Gesase S, Mmbando BP, Kitua AY, Lemnge MM, Cavanagh D, Hviid L, Theander TG. Levels of plasma immunoglobulin G with specificity against the cysteine-rich interdomain regions of a semiconserved Plasmodium falciparum erythrocyte membrane protein 1, VAR4, predict protection against malarial anemia and febrile episodes. Infect Immun 2006; 74:2867-75. [PMID: 16622225 PMCID: PMC1459698 DOI: 10.1128/iai.74.5.2867-2875.2006] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antibodies to variant surface antigen have been implicated as mediators of malaria immunity in studies measuring immunoglobulin G (IgG) binding to infected erythrocytes. Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is an important target for these antibodies, but no study has directly linked the presence of PfEMP1 antibodies in children to protection. We measured plasma IgG levels to the cysteine-rich interdomain region 1alpha (CIDR1alpha) of VAR4 (VAR4-CIDR1alpha), a member of a semiconserved PfEMP1 subfamily, by enzyme-linked immunosorbent assay in 561 Tanzanian individuals, who were monitored clinically for 7 months. The participants resided in Mkokola (a high-transmission village where malaria is holoendemic) or Kwamasimba (a moderate-transmission village). For comparison, plasma IgG levels to two merozoite surface protein 1 (MSP1) constructs, MSP1-19 and MSP1 block 2, and a control CIDR1 domain were measured. VAR4-CIDR1alpha antibodies were acquired at an earlier age in Mkokola than in Kwamasimba, but after the age of 10 years the levels were comparable in the two villages. After controlling for age and other covariates, the risk of having anemia at enrollment was reduced in VAR4-CIDR1alpha responders for Mkokola (adjusted odds ratio [AOR], 0.49; 95% confidence interval [CI], 0.29 to 0.88; P = 0.016) and Kwamasimba (AOR, 0.33; 95% CI, 0.16 to 0.68; P = 0.003) villages. The risk of developing malaria fever was reduced among individuals with a measurable VAR4-CIDR1alpha response from Mkokola village (AOR, 0.51; 95% CI, 0.29 to 0.89; P = 0.018) but not in Kwamasimba. Antibody levels to the MSP1 constructs and the control CIDR1alpha domain were not associated with morbidity protection. These data strengthen the concept of developing vaccines based on PfEMP1.
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Affiliation(s)
- John P A Lusingu
- Centre for Medical Parasitology, Institute for Medical Microbiology and Immunology, University of Copenhagen, Denmark.
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Abstract
That humans in endemic areas become immune to malaria offers encouragement to the idea of developing protective vaccines. However natural immunity is relatively inefficient, being bought at the cost of substantial childhood mortality, and current vaccines are only partially protective. Understanding potential targets and mechanisms of protective immunity is important in the development and evaluation of future vaccines. Some of the problems in identifying such targets and mechanisms in humans naturally exposed to malaria may stem from conceptual and methodological issues related to defining who in a population is susceptible, problems in defining immune responsiveness at single time points and issues related to antigenic polymorphism, as well as the failure of many current approaches to examine functional aspects of the immune response. Protective immune responses may be directed to the pre erythrocytic parasite, to the free merozoite of the blood stage parasite or to new antigens induced on the infected red cell surface. Tackling the methodological issues of defining protection and immune response, together with studies that combine functional assays with new approaches such as allelic exchange and gene knock out offer opportunities for better defining key targets and mechanisms.
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Affiliation(s)
- K Marsh
- KEMRI Centre for Geographic Medicine Research Coast (CGMRC), PO Box 230, Kilifi, Kenya.
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Sachdeva S, Mohmmed A, Dasaradhi PVN, Crabb BS, Katyal A, Malhotra P, Chauhan VS. Immunogenicity and protective efficacy of Escherichia coli expressed Plasmodium falciparum merozoite surface protein-1(42) using human compatible adjuvants. Vaccine 2005; 24:2007-16. [PMID: 16377036 DOI: 10.1016/j.vaccine.2005.11.041] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2005] [Revised: 11/14/2005] [Accepted: 11/15/2005] [Indexed: 11/16/2022]
Abstract
The C-terminal 42-kDa fragment of the merozoite surface protein-1 of Plasmodium falciparum (PfMSP-1(42)) was expressed as a recombinant protein in Escherichia coli and purified to near homogeneity. We tested the immunogenicity of recombinant PfMSP-1(42) in three clinically acceptable adjuvants (Montanide ISA 720, alum and MF59) in mice and in rabbits. High antibody responses were obtained with two adjuvant formulations with IgGl being the predominant immunoglobulin isotype. Significant T-cell proliferation responses were also observed. Competitive enzyme linked immunosorbant assay (ELISA) showed the presence of both invasion and processing inhibitory antibodies in sera obtained from the immunized rabbits. Passive immunizations of mice with anti-PfMSP-1(42) IgG purified from the rabbit-sera were found to be protective against a parasite challenge with P. berghei/P. falciparum chimeric line (Pb-PfM19) that expresses Plasmodium falciparum MSP-1(19). These findings may be useful for the development of a malaria vaccine based on Plasmodium falciparum MSP-1(42).
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Affiliation(s)
- Suraksha Sachdeva
- International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India
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