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McLean FE, Azasi Y, Sutherland C, Toboh E, Ansong D, Agbenyega T, Awandare G, Rowe JA. Detection of naturally acquired, strain-transcending antibodies against rosetting Plasmodium falciparum strains in humans. Infect Immun 2024:e0001524. [PMID: 38842304 DOI: 10.1128/iai.00015-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Accepted: 04/29/2024] [Indexed: 06/07/2024] Open
Abstract
Strain-transcending antibodies against virulence-associated subsets of P. falciparum-infected erythrocyte surface antigens could protect children from severe malaria. However, the evidence supporting the existence of such antibodies is incomplete and inconsistent. One subset of surface antigens associated with severe malaria, rosette-mediating Plasmodium falciparum Erythrocyte Membrane Protein one (PfEMP1) variants, cause infected erythrocytes to bind to uninfected erythrocytes to form clusters of cells (rosettes) that contribute to microvascular obstruction and pathology. Here, we tested plasma from 80 individuals living in malaria-endemic regions for IgG recognition of the surface of four P. falciparum rosetting strains using flow cytometry. Broadly reactive plasma samples were then used in antibody elution experiments in which intact IgG was eluted from the surface of infected erythrocytes and transferred to heterologous rosetting strains to look for strain-transcending antibodies. We found that seroprevalence (percentage of positive plasma samples) against allopatric rosetting strains was high in adults (63%-93%) but lower in children (13%-48%). Strain-transcending antibodies were present in nine out of eleven eluted antibody experiments, with six of these recognizing multiple heterologous rosetting parasite strains. One eluate had rosette-disrupting activity against heterologous strains, suggesting PfEMP1 as the likely target of the strain-transcending antibodies. Naturally acquired strain-transcending antibodies to rosetting P. falciparum strains in humans have not been directly demonstrated previously. Their existence suggests that such antibodies could play a role in clinical protection and raises the possibility that conserved epitopes recognized by strain-transcending antibodies could be targeted therapeutically by monoclonal antibodies or vaccines.
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Affiliation(s)
- Florence E McLean
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Yvonne Azasi
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Cameron Sutherland
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | | | - Daniel Ansong
- Kwame Nkrumah University of Science and Technology, School of Medical Sciences, Kumasi, Ghana
- Departments of Child Health and Medicine, Komfo Anokye Teaching Hospital, Kumasi, Ghana
- Malaria Research Centre, Agogo, Ghana
| | - Tsiri Agbenyega
- Kwame Nkrumah University of Science and Technology, School of Medical Sciences, Kumasi, Ghana
- Departments of Child Health and Medicine, Komfo Anokye Teaching Hospital, Kumasi, Ghana
- Malaria Research Centre, Agogo, Ghana
| | - Gordon Awandare
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, Legon, Ghana
| | - J Alexandra Rowe
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
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2
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Nziza N, Tran TM, DeRiso EA, Dolatshahi S, Herman JD, de Lacerda L, Junqueira C, Lieberman J, Ongoiba A, Doumbo S, Kayentao K, Traore B, Crompton PD, Alter G. Accumulation of Neutrophil Phagocytic Antibody Features Tracks With Naturally Acquired Immunity Against Malaria in Children. J Infect Dis 2023; 228:759-768. [PMID: 37150885 PMCID: PMC10503956 DOI: 10.1093/infdis/jiad115] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 04/21/2023] [Indexed: 05/09/2023] Open
Abstract
BACKGROUND Studies have demonstrated the protective role of antibodies against malaria. Young children are known to be particularly vulnerable to malaria, pointing to the evolution of naturally acquired clinical immunity over time. However, whether changes in antibody functionality track with the acquisition of naturally acquired malaria immunity remains incompletely understood. METHODS Using systems serology, we characterized sporozoite- and merozoite-specific antibody profiles of uninfected Malian children before the malaria season who differed in their ability to control parasitemia and fever following Plasmodium falciparum (Pf) infection. We then assessed the contributions of individual traits to overall clinical outcomes, focusing on the immunodominant sporozoite CSP and merozoite AMA1 and MSP1 antigens. RESULTS Humoral immunity evolved with age, with an expansion of both magnitude and functional quality, particularly within blood-stage phagocytic antibody activity. Moreover, concerning clinical outcomes postinfection, protected children had higher antibody-dependent neutrophil activity along with higher levels of MSP1-specific IgG3 and IgA and CSP-specific IgG3 and IgG4 prior to the malaria season. CONCLUSIONS These data point to the natural evolution of functional humoral immunity to Pf with age and highlight particular antibody Fc-effector profiles associated with the control of malaria in children, providing clues for the design of next-generation vaccines or therapeutics.
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Affiliation(s)
- Nadege Nziza
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard University, Cambridge, Massachusetts, USA
| | - Tuan M Tran
- Malaria Infection Biology and Immunity Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA
- Division of Infectious Diseases, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Ryan White Center for Pediatric Infectious Disease and Global Health, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Elizabeth A DeRiso
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard University, Cambridge, Massachusetts, USA
| | - Sepideh Dolatshahi
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard University, Cambridge, Massachusetts, USA
| | - Jonathan D Herman
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard University, Cambridge, Massachusetts, USA
| | - Luna de Lacerda
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, Massachusetts, USA
- Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA
- Instituto René Rachou, Fundação Oswaldo Cruz, Belo Horizonte, MG, Brazil
| | - Caroline Junqueira
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, Massachusetts, USA
- Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA
- Instituto René Rachou, Fundação Oswaldo Cruz, Belo Horizonte, MG, Brazil
| | - Judy Lieberman
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, Massachusetts, USA
- Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA
| | - Aissata Ongoiba
- Malaria Research and Training Centre, Mali International Center of Excellence in Research, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Safiatou Doumbo
- Malaria Research and Training Centre, Mali International Center of Excellence in Research, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Kassoum Kayentao
- Malaria Research and Training Centre, Mali International Center of Excellence in Research, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Boubacar Traore
- Malaria Research and Training Centre, Mali International Center of Excellence in Research, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Peter D Crompton
- Malaria Infection Biology and Immunity Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA
| | - Galit Alter
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard University, Cambridge, Massachusetts, USA
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Bandoh B, Kyei-Baafour E, Aculley B, van der Puije W, Tornyigah B, Akyea-Mensah K, Hviid L, Ngala RA, Frempong MT, Ofori MF. Influence of α2-Macroglobulin, Anti-Parasite IgM and ABO Blood Group on Rosetting in Plasmodium falciparum Clinical Isolates and Their Associations with Disease Severity in a Ghanaian Population. J Blood Med 2022; 13:151-164. [PMID: 35330697 PMCID: PMC8939864 DOI: 10.2147/jbm.s329177] [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: 08/24/2021] [Accepted: 03/07/2022] [Indexed: 11/23/2022] Open
Abstract
Purpose The severity of Plasmodium falciparum infections is associated with the ability of the infected red blood cells to cytoadhere to host vascular endothelial surfaces and to uninfected RBCs. Host blood group antigens and two serum proteins α2-macroglobulin (α2M) and IgM have been implicated in rosette formation in laboratory-adapted P. falciparum. However, there is only limited information about these phenotypes in clinical isolates. Methods This was a hospital-based study involving children under 12 years-of-age reporting to the Hohoe Municipal Hospital with different clinical presentations of malaria. Parasite isolates were grown and rosette capabilities and characteristics were investigated by fluorescence microscopy. α2M and IgM were detected by ELISA. Results Rosette formation was observed in 46.8% (75/160) of the parasite isolates from all the blood groups tested. Rosettes were more prevalent (55%) among isolates from patients with severe malaria compared to isolates from patients with uncomplicated malaria (45%). Rosette prevalence was highest (30%) among patients with blood group O (30%) and B (29%), while the mean rosette frequency was higher in isolates from patients with blood group A (28.7). Rosette formation correlated negatively with age (r = −0.09, P= 0.008). Participants with severe malaria had a lower IgM concentration (3.683±3.553) than those with uncomplicated malaria (5.256±4.294) and the difference was significant (P= 0.0228). The mean concentrations of anti-parasite IgM measured among the clinical isolates which formed rosettes was lower (4.2 ±3.930 mg/mL), than that in the non rosetting clinical isolates (4.604 ±4.159 mg/mL) but the difference was not significant (P=0.2733). There was no significant difference in plasma α2M concentration between rosetting and non rosetting isolates (P=0.442). Conclusion P. falciparum parasite rosette formation was affected by blood group type and plasma concentration of IgM. A lower IgM concentration was associated with severe malaria whilst a higher α2M concentration was associated with uncomplicated malaria.
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Affiliation(s)
- Betty Bandoh
- Department of Molecular Medicine, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Eric Kyei-Baafour
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Belinda Aculley
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana
| | - William van der Puije
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Bernard Tornyigah
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Kwadwo Akyea-Mensah
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Lars Hviid
- Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Infectious Diseases, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Robert A Ngala
- Department of Molecular Medicine, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | - Margaret T Frempong
- Department of Molecular Medicine, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | - Michael F Ofori
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana
- Correspondence: Michael F Ofori, Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Post Office Box LG581, Legon, Accra, Ghana, Tel +233 244 715975, Fax +233 302 502182, Email
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Lopez-Perez M, van der Puije W, Castberg FC, Ofori MF, Hviid L. Binding of human serum proteins to Plasmodium falciparum-infected erythrocytes and its association with malaria clinical presentation. Malar J 2020; 19:362. [PMID: 33032607 PMCID: PMC7545873 DOI: 10.1186/s12936-020-03438-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 10/01/2020] [Indexed: 11/10/2022] Open
Abstract
Background The pathogenesis of Plasmodium falciparum malaria is related to the ability of parasite‑infected erythrocytes (IEs) to adhere to the vascular endothelium (cytoadhesion/sequestration) or to surrounding uninfected erythrocytes (rosetting). Both processes are mediated by the expression of members of the clonally variant PfEMP1 parasite protein family on the surface of the IEs. Recent evidence obtained with laboratory-adapted clones indicates that P. falciparum can exploit human serum factors, such as IgM and α2-macroglobulin (α2M), to increase the avidity of PfEMP1-mediated binding to erythrocyte receptors, as well as to evade host PfEMP1-specific immune responses. It has remained unclear whether PfEMP1 variants present in field isolates share these characteristics, and whether they are associated with clinical malaria severity. These issues were investigated here. Methods Children 1–12 years reporting with P. falciparum malaria to Hohoe Municipal Hospital, Ghana were enrolled in the study. Parasites from children with uncomplicated (UM) and severe malaria (SM) were collected. Binding of α2M and IgM from non-immune individuals to erythrocytes infected by P. falciparum isolates from 34 children (UM and SM) were analysed by flow cytometry. Rosetting in the presence of IgM or α2M was also evaluated. Experimental results were analysed according to the clinical presentation of the patients. Results Clinical data from 108 children classified as UM (n = 54) and SM cases (n = 54) were analysed. Prostration, severe malaria anaemia, and hyperparasitaemia were the most frequent complications. Three children were diagnosed with cerebral malaria, and one child died. Parasite isolates from UM (n = 14) and SM (n = 20) children were analysed. Most of the field isolates bound non-immune IgM (33/34), whereas the α2M-binding was less common (23/34). Binding of both non-immune IgM and α2M was higher but not significant in IEs from children with SM than from children with UM. In combination, IgM and α2M supported rosette formation at levels similar to that observed in the presence of 10% human serum. Conclusions The results support the hypothesis that binding of non-immune IgM and/or α2M to IEs facilitates rosette formation and perhaps contributes to P. falciparum malaria severity.
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Affiliation(s)
- Mary Lopez-Perez
- Centre for Medical Parasitology, Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
| | - William van der Puije
- Department of Immunology, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana.,West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), College of Basic and Applied Sciences, University of Ghana, Legon, Ghana.,Centre for Medical Parasitology, Department of Infectious Diseases and Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark
| | - Filip C Castberg
- Centre for Medical Parasitology, Department of Infectious Diseases and Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark
| | - Michael F Ofori
- Department of Immunology, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Lars Hviid
- Centre for Medical Parasitology, Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark. .,Centre for Medical Parasitology, Department of Infectious Diseases and Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark.
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5
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Abstract
The upregulation of immune checkpoint molecules, such as programmed cell death protein 1 (PD1) and cytotoxic T lymphocyte antigen 4 (CTLA4), on immune cells occurs during acute infections, such as malaria, as well as during chronic persistent viral infections, including HIV and hepatitis B virus. These pathways are important for preventing immune-driven pathology but can also limit immune-mediated clearance of the infection. The recent success of immune checkpoint blockade in cancer therapy suggests that targeting these pathways would also be effective for preventing and treating a range of infectious diseases. Here, we review our current understanding of immune checkpoint pathways in the pathogenesis of infectious diseases and discuss the potential for therapeutically targeting these pathways in this setting.
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Affiliation(s)
- Michelle N Wykes
- QIMR Berghofer Medical Research Institute, 300 Herston Road, Herston, Brisbane, Queensland 4006, Australia
| | - Sharon R Lewin
- The Peter Doherty Institute for Infection and Immunity, The University of Melbourne and Royal Melbourne Hospital, Melbourne, Victoria 3000, Australia
- Department of Infectious Diseases, Alfred Hospital and Monash University, Melbourne, Victoria 3004, Australia
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6
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Abstract
The Plasmodium falciparum erythrocyte membrane protein 1 antigens that are inserted onto the surface of P. falciparum infected erythrocytes play a key role both in the pathology of severe malaria and as targets of naturally acquired immunity. They might be considered unlikely vaccine targets because they are extremely diverse. However, several lines of evidence suggest that underneath this molecular diversity there are a restricted set of epitopes which may act as effective targets for a vaccine against severe malaria. Here we review some of the recent developments in this area of research, focusing on work that has assessed the potential of these molecules as possible vaccine targets.
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7
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Homsy J, Dorsey G, Arinaitwe E, Wanzira H, Kakuru A, Bigira V, Muhindo M, Kamya MR, Sandison TG, Tappero JW. Protective efficacy of prolonged co-trimoxazole prophylaxis in HIV-exposed children up to age 4 years for the prevention of malaria in Uganda: a randomised controlled open-label trial. LANCET GLOBAL HEALTH 2015; 2:e727-36. [PMID: 25433628 DOI: 10.1016/s2214-109x(14)70329-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND WHO recommends daily co-trimoxazole for children born to HIV-infected mothers from 6 weeks of age until breastfeeding cessation and exclusion of HIV infection. We have previously reported on the effectiveness of continuation of co-trimoxazole prophylaxis up to age 2 years in these children. We assessed the protective efficacy and safety of prolonging co-trimoxazole prophylaxis until age 4 years in HIV-exposed children. METHODS We undertook an open-label randomised controlled trial alongside two observational cohorts in eastern Uganda, an area with high HIV prevalence, malaria transmission intensity, and antifolate resistance. We enrolled HIV-exposed infants between 6 weeks and 9 months of age and prescribed them daily co-trimoxazole until breastfeeding cessation and HIV-status confirmation. At the end of breastfeeding, children who remained HIV-uninfected were randomly assigned (1:1) to discontinue co-trimoxazole or to continue taking it up to age 2 years. At age 2 years, children who continued co-trimoxazole prophylaxis were randomly assigned (1:1) to discontinue or continue prophylaxis from age 2 years to age 4 years. The primary outcome was incidence of malaria (defined as the number of treatments for new episodes of malaria diagnosed with positive thick smear) at age 4 years. For additional comparisons, we observed 48 HIV-infected children who took continuous co-trimoxazole prophylaxis and 100 HIV-unexposed uninfected children who never received prophylaxis. We measured grade 3 and 4 serious adverse events and hospital admissions. All children were followed up to age 5 years and all analyses were by intention to treat. This study is registered with ClinicalTrials.gov, number NCT00527800. FINDINGS 203 HIV-exposed infants were enrolled between Aug 10, 2007, and March 28, 2008. After breastfeeding ended, 185 children were not infected with HIV and were randomly assigned to stop (n=87) or continue (n=98) co-trimoxazole up to age 2 years. At age 2 years, 91 HIV-exposed children who had remained on co-trimoxazole prophylaxis were randomly assigned to discontinue (n=46) or continue (n=45) co-trimoxazole from age 2 years to age 4 years. We recorded 243 malaria episodes (2·91 per person-years) in the 45 HIV-exposed children assigned to continue co-trimoxazole until age 4 years compared with 503 episodes (5·60 per person-years) in the 46 children assigned to stop co-trimoxazole at age 2 years (incidence rate ratio 0·53, 95% CI 0·39-0·71; p< 0·0001). There was no evidence of malaria incidence rebound in the year after discontinuation of co-trimoxazole in the HIV-exposed children who stopped co-trimoxazole at age 2 years, but incidence increased significantly in HIV-exposed children who stopped co-trimoxazole at age 4 years (odds ratio 1·78, 95% CI 1·19-2·66; p= 0·005). Incidence of grade 3 or 4 serious adverse events, hospital admissions, or deaths did not significantly differ between HIV-exposed, HIV-unexposed, and HIV-infected children.
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Affiliation(s)
- Jaco Homsy
- Global Health Sciences, University of California, San Francisco, CA, USA; Centers for Disease Control and Prevention, Entebbe, Uganda.
| | - Grant Dorsey
- Department of Medicine, University of California, San Francisco, CA, USA
| | | | | | - Abel Kakuru
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Victor Bigira
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Mary Muhindo
- Department of Medicine, University of California, San Francisco, CA, USA
| | - Moses R Kamya
- Department of Medicine, Makerere University Medical School, Kampala, Uganda
| | | | - Jordan W Tappero
- Centers for Disease Control and Prevention, Entebbe, Uganda; Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
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8
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Dendritic cells: The Trojan horse of malaria? Int J Parasitol 2012; 42:583-7. [DOI: 10.1016/j.ijpara.2012.03.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 02/09/2012] [Accepted: 03/01/2012] [Indexed: 11/18/2022]
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9
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Ghumra A, Semblat JP, Ataide R, Kifude C, Adams Y, Claessens A, Anong DN, Bull PC, Fennell C, Arman M, Amambua-Ngwa A, Walther M, Conway DJ, Kassambara L, Doumbo OK, Raza A, Rowe JA. Induction of strain-transcending antibodies against Group A PfEMP1 surface antigens from virulent malaria parasites. PLoS Pathog 2012; 8:e1002665. [PMID: 22532802 PMCID: PMC3330128 DOI: 10.1371/journal.ppat.1002665] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2011] [Accepted: 03/08/2012] [Indexed: 12/22/2022] Open
Abstract
Sequence diversity in pathogen antigens is an obstacle to the development of interventions against many infectious diseases. In malaria caused by Plasmodium falciparum, the PfEMP1 family of variant surface antigens encoded by var genes are adhesion molecules that play a pivotal role in malaria pathogenesis and clinical disease. PfEMP1 is a major target of protective immunity, however, development of drugs or vaccines based on PfEMP1 is problematic due to extensive sequence diversity within the PfEMP1 family. Here we identified the PfEMP1 variants transcribed by P. falciparum strains selected for a virulence-associated adhesion phenotype (IgM-positive rosetting). The parasites transcribed a subset of Group A PfEMP1 variants characterised by an unusual PfEMP1 architecture and a distinct N-terminal domain (either DBLα1.5 or DBLα1.8 type). Antibodies raised in rabbits against the N-terminal domains showed functional activity (surface reactivity with live infected erythrocytes (IEs), rosette inhibition and induction of phagocytosis of IEs) down to low concentrations (<10 µg/ml of total IgG) against homologous parasites. Furthermore, the antibodies showed broad cross-reactivity against heterologous parasite strains with the same rosetting phenotype, including clinical isolates from four sub-Saharan African countries that showed surface reactivity with either DBLα1.5 antibodies (variant HB3var6) or DBLα1.8 antibodies (variant TM284var1). These data show that parasites with a virulence-associated adhesion phenotype share IE surface epitopes that can be targeted by strain-transcending antibodies to PfEMP1. The existence of shared surface epitopes amongst functionally similar disease-associated P. falciparum parasite isolates suggests that development of therapeutic interventions to prevent severe malaria is a realistic goal. Malaria remains one of the world's most deadly diseases. Life-threatening malaria is linked to a process called rosetting, in which malaria parasite-infected red blood cells bind to uninfected red cells to form aggregates that block blood flow in vital organs such as the brain. Current efforts to develop drugs or vaccines against rosetting are hindered by variation in the parasite rosette-mediating proteins, found on the surface of infected red cells. We studied these parasite-derived surface proteins and discovered that although they are variable, they share some common features. We raised antibodies against the rosette-mediating proteins, and found that they cross-reacted with multiple rosetting parasite strains from different countries around the world, including samples collected directly from African children with severe malaria. These findings provide new insights into malaria parasite interactions with human cells, and provide proof of principle that variable parasite molecules from virulent malaria parasites can induce strain-transcending antibodies. Hence, this work provides the foundation for the development of new therapies to treat or prevent life-threatening malaria.
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Affiliation(s)
- Ashfaq Ghumra
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Jean-Philippe Semblat
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Ricardo Ataide
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Carolyne Kifude
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Yvonne Adams
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Antoine Claessens
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Damian N. Anong
- Biotechnology Unit, Faculty of Science, University of Buea, Buea, Cameroon
| | - Peter C. Bull
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Clare Fennell
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Monica Arman
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | | | - Michael Walther
- Medical Research Council Laboratories, Fajara, Banjul, The Gambia
| | - David J. Conway
- Medical Research Council Laboratories, Fajara, Banjul, The Gambia
| | - Lalla Kassambara
- Malaria Research and Training Centre, University of Bamako, Bamako, Mali
| | - Ogobara K. Doumbo
- Malaria Research and Training Centre, University of Bamako, Bamako, Mali
| | - Ahmed Raza
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - J. Alexandra Rowe
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail:
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10
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Wykes MN. Are plasmacytoid dendritic cells the misguided sentinels of malarial immunity? Trends Parasitol 2012; 28:182-6. [PMID: 22365902 DOI: 10.1016/j.pt.2012.01.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 01/28/2012] [Accepted: 01/30/2012] [Indexed: 12/23/2022]
Abstract
Dendritic cells (DCs), the sentinels of immunity, reside in almost every organ of the body. These cells are responsible for initiating immune responses against infectious agents. DCs are divided into different subsets based on their biological functions, with plasmacytoid DCs (pDCs) and conventional DCs (cDCs) being two major populations. The ability of DCs to protect against malaria infection was recently questioned when pDCs were reported to be a reservoir for rodent Plasmodium spp. in the spleen. This opinion article explores how the occupation of pDCs by the parasite may corrupt immunity against malaria.
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Affiliation(s)
- Michelle N Wykes
- The Queensland Institute of Medical Research, The Bancroft Centre, 300 Herston Road, Brisbane, Queensland 4006, Australia.
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11
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Vigan-Womas I, Lokossou A, Guillotte M, Juillerat A, Bentley G, Garcia A, Mercereau-Puijalon O, Migot-Nabias F. The humoral response to Plasmodium falciparum VarO rosetting variant and its association with protection against malaria in Beninese children. Malar J 2010; 9:267. [PMID: 20923548 PMCID: PMC2959068 DOI: 10.1186/1475-2875-9-267] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Accepted: 10/05/2010] [Indexed: 11/27/2022] Open
Abstract
Background The capacity of Plasmodium falciparum-infected erythrocytes to bind uninfected erythrocytes (rosetting) is associated with severe malaria in African children. Rosetting is mediated by a subset of the variant surface antigens PfEMP1 targeted by protective antibody responses. Analysis of the response to rosette-forming parasites and their PfEMP1 adhesive domains is essential for understanding the acquisition of protection against severe malaria. To this end, the antibody response to a rosetting variant was analysed in children recruited with severe or uncomplicated malaria or asymptomatic P. falciparum infection. Methods Serum was collected from Beninese children with severe malaria, uncomplicated malaria or P. falciparum asymptomatic infection (N = 65, 37 and 52, respectively) and from immune adults (N = 30) living in the area. Infected erythrocyte surface-reactive IgG, rosette disrupting antibodies and IgG to the parasite crude extract were analysed using the single variant Palo Alto VarO-infected line. IgG, IgG1 and IgG3 to PfEMP1-varO-derived NTS-DBL1α1, CIDRγ and DBL2βC2 recombinant domains were analysed by ELISA. Antibody responses were compared in the clinical groups. Stability of the response was studied using a blood sampling collected 14 months later from asymptomatic children. Results Seroprevalence of erythrocyte surface-reactive IgG was high in adults (100%) and asymptomatic children (92.3%) but low in children with severe or uncomplicated malaria (26.1% and 37.8%, respectively). The IgG, IgG1 and IgG3 antibody responses to the varO-derived PfEMP1 domains were significantly higher in asymptomatic children than in children with clinical malaria in a multivariate analysis correcting for age and parasite density at enrolment. They were essentially stable, although levels tended to decrease with time. VarO-surface reactivity correlated positively with IgG reactivity to the rosetting domain varO-NTS-DBL1α1. None of the children sera, including those with surface-reactive antibodies possessed anti-VarO-rosetting activity, and few adults had rosette-disrupting antibodies. Conclusions Children with severe and uncomplicated malaria had similar responses. The higher prevalence and level of VarO-reactive antibodies in asymptomatic children compared to children with malaria is consistent with a protective role for anti-VarO antibodies against clinical falciparum malaria. The mechanism of such protection seems independent of rosette-disruption, suggesting that the cytophilic properties of antibodies come into play.
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Affiliation(s)
- Inès Vigan-Womas
- Institut Pasteur, Unité d'Immunologie Moléculaire des Parasites, F-75015 Paris, France
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12
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Abstract
OBJECTIVES We evaluated plasma creatinine, urea, bilirubin, lactic acid, and nitric oxide values in children with malaria to identify indices of disease severity and predictors of fatal outcomes. METHODS Children 0 to 15 years old were recruited, clinical data recorded, and blood samples collected. Plasma creatinine, urea, bilirubin, lactic acid, and nitric oxide (NO) values were determined by spectrophotometry. RESULTS Values of creatinine, urea, and bilirubin were normal in all the groups except for urea in some groups (55.30 +/- 5.508 mg/dL and 60.45 +/- 15.56 mg/dL in anemia patients and those with the combined symptoms of cerebral malaria and anemia, respectively). The mean lactate values were high in severe malaria groups (0.57 +/- 0.05 g/L and 0.48 +/- 0.05 g/L in cerebral malaria and anemia patients, respectively). As for the mean NO values, they were above the normal range in all the groups, except the controls, but particularly in the severe malaria groups (68.66 +/- 7.85, 84.52 +/- 8.17, 99.57 +/- 10.48, 87.25 +/- 12.57, and 93.48 +/- 7.09 micromol/L for the control, uncomplicated malaria, anemia, cerebral malaria patients and those with the combined symptoms of cerebral malaria and anemia, respectively; P = 0.643). CONCLUSIONS In this setting, lactate and NO were indicators of poor prognosis. Though the impact of creatinine, urea, and bilirubin were not found to be significant, they can still be useful to assess improvement in severe malaria cases.
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Metenou S, Dembélé B, Konate S, Dolo H, Coulibaly SY, Coulibaly YI, Diallo AA, Soumaoro L, Coulibaly ME, Sanogo D, Doumbia SS, Wagner M, Traoré SF, Klion A, Mahanty S, Nutman TB. Patent filarial infection modulates malaria-specific type 1 cytokine responses in an IL-10-dependent manner in a filaria/malaria-coinfected population. THE JOURNAL OF IMMUNOLOGY 2009; 183:916-24. [PMID: 19561105 DOI: 10.4049/jimmunol.0900257] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The effect of filarial infections on malaria-specific immune responses was investigated in Malian villages coendemic for filariasis (Fil) and malaria. Cytokines were measured from plasma and Ag-stimulated whole blood from individuals with Wuchereria bancrofti and/or Mansonella perstans infections (Fil(+); n = 19) and those without evidence of filarial infection (Fil(-); n = 19). Plasma levels of IL-10 (geometric mean [GM], 22.8 vs 10.4) were higher in Fil(+) compared with Fil(-), whereas levels of IFN-inducible protein (IP)-10 were lower in Fil(+) (GM, 66.3 vs 110.0). Fil(+) had higher levels of spontaneously secreted IL-10 (GM, 59.3 vs 6.8 pg/ml) and lower levels of IL-2 (1.0 vs 1.2 pg/ml) than did Fil(-). Although there were no differences in levels of Staphylococcus aureus enterotoxin B-induced cytokines between the two groups, Fil(+) mounted lower IL-12p70 (GM, 1.11 vs 3.83 pg/ml; p = 0.007), IFN-gamma (GM, 5.44 vs 23.41 pg/ml; p = 0.009), and IP-10 (GM, 29.43 vs 281.7 pg/ml; p = 0.007) responses following malaria Ag (MalAg) stimulation compared with Fil(-). In contrast, Fil(+) individuals had a higher MalAg-specific IL-10 response (GM, 7318 pg/ml vs 3029 pg/ml; p = 0.006) compared with those without filarial infection. Neutralizing Ab to IL-10 (but not to TGFbeta) reversed the down-regulated MalAg-specific IFN-gamma and IP-10 (p < 0.001) responses in Fil(+). Together, these data demonstrate that filarial infections modulate the Plasmodium falciparum-specific IL-12p70/IFN-gamma secretion pathways known to play a key role in resistance to malaria and that they do so in an IL-10-dependent manner.
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Affiliation(s)
- Simon Metenou
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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14
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Oleinikov AV, Amos E, Frye IT, Rossnagle E, Mutabingwa TK, Fried M, Duffy PE. High throughput functional assays of the variant antigen PfEMP1 reveal a single domain in the 3D7 Plasmodium falciparum genome that binds ICAM1 with high affinity and is targeted by naturally acquired neutralizing antibodies. PLoS Pathog 2009; 5:e1000386. [PMID: 19381252 PMCID: PMC2663049 DOI: 10.1371/journal.ppat.1000386] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2008] [Accepted: 03/18/2009] [Indexed: 12/01/2022] Open
Abstract
Plasmodium falciparum–infected erythrocytes bind endothelial receptors to sequester in vascular beds, and binding to ICAM1 has been implicated in cerebral malaria. Binding to ICAM1 may be mediated by the variant surface antigen family PfEMP1: for example, 6 of 21 DBLβC2 domains from the IT4 strain PfEMP1 repertoire were shown to bind ICAM1, and the PfEMP1 containing these 6 domains are all classified as Group B or C type. In this study, we surveyed binding of ICAM1 to 16 DBLβC2 domains of the 3D7 strain PfEMP1 repertoire, using a high throughput Bioplex assay format. Only one DBL2βC2 domain from the Group A PfEMP1 PF11_0521 showed strong specific binding. Among these 16 domains, DBL2βC2PF11_0521 best preserved the residues previously identified as conserved in ICAM1-binding versus non-binding domains. Our analyses further highlighted the potential role of conserved residues within predominantly non-conserved flexible loops in adhesion, and, therefore, as targets for intervention. Our studies also suggest that the structural/functional DBLβC2 domain involved in ICAM1 binding includes about 80 amino acid residues upstream of the previously suggested DBLβC2 domain. DBL2βC2PF11_0521 binding to ICAM1 was inhibited by immune sera from east Africa but not by control US sera. Neutralizing antibodies were uncommon in children but common in immune adults from east Africa. Inhibition of binding was much more efficient than reversal of binding, indicating a strong interaction between DBL2βC2PF11_0521 and ICAM1. Our high throughput approach will significantly accelerate studies of PfEMP1 binding domains and protective antibody responses. Plasmodium falciparum exports the protein PfEMP1 to the surface of parasitized erythrocytes for roles in immunoevasion and adhesion. The size and structural complexity of this diverse protein family have limited earlier studies of PfEMP1 biology to low throughput and semi-quantitative approaches. We developed a high throughput quantitative assay of PfEMP1 adhesion and used it to analyze structural features of domains that bind the putative cerebral receptor ICAM1, as well as to survey the acquisition of functional antibodies in malaria-exposed children and adults. In studies of the PfEMP1 repertoire of clone 3D7 parasites, a single specific domain bound ICAM1 strongly. PfEMP1 domains that bind ICAM1 strongly have conserved features, including conserved amino acids within otherwise highly variant flexible loops of the protein. While neutralizing antibodies against the PfEMP1–ICAM1 interaction were uncommon in Tanzanian children, such antibodies were common in east African adults, possibly explaining why immune adults rarely carry ICAM1-binding parasites. This high throughput platform will significantly accelerate studies of PfEMP1 binding domains and the corresponding antibody responses involved in protective immunity.
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Templeton TJ. The varieties of gene amplification, diversification and hypervariability in the human malaria parasite, Plasmodium falciparum. Mol Biochem Parasitol 2009; 166:109-16. [PMID: 19375460 DOI: 10.1016/j.molbiopara.2009.04.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 04/05/2009] [Accepted: 04/07/2009] [Indexed: 10/20/2022]
Abstract
The human malaria parasite, Plasmodium falciparum, is able to evade host cell-mediated and humoral immunity to maintain both persistent and repeated infections. Immune evasion is in part due to a robust repertoire of proteins which participate in host-parasite interactions but also exhibit profound antigenic diversity, and in some instances switches in gene expression. The antigenic diversity occurs both at the parasite level within families of amplified proteins, and within populations of parasites in which mechanisms of recombination and gene conversion conspire to create a broad plasticity in the antigenic exposure to the host. This review will introduce the spectrum of amplified protein families in P. falciparum and focus on three sub-telomeric encoded families, RIFIN, STEVOR and Pfmc-2TM which exhibit hypervariability with respect to their antigenic diversity.
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Affiliation(s)
- Thomas J Templeton
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY 10021, USA.
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16
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Mfonkeu JBP, Gouado I, Kuate HF, Zambou O, Grau G, Combes V, Zollo PHA. Clinical presentation, haematological indices and management of children with severe and uncomplicated malaria in Douala, Cameroon. Pak J Biol Sci 2009; 11:2401-6. [PMID: 19137849 DOI: 10.3923/pjbs.2008.2401.2406] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
This study carried out from January to June 2007, was undertaken to describe the clinical presentation of childhood malaria in Douala, a meso-endemic area as far as malaria transmission is concerned. One hundred and seventy eight children were enrolled after informed consent of their parents. The sample characteristics were recorded and clinical as well as preliminary laboratory investigations were performed. Thirty eight children coming for vaccination and counselling was targeted to serve as control. According to the results obtained, cerebral malaria (CM) seems to be associated with young age, whilst Malaria anaemia (MA) was predominant among older children. Hyperpyrexia and hyperparasitaemia were high among CM patients and 11.1% of them died, however, no neurological squeal was noticed immediately after discharge on those who survived. Haemoglobin and glycaemia were low on MA and CM patients; these groups had low percentage in bed nets utilization as well. These results suggest that the clinical presentation of the disease differ with the geographic location and malaria disease features varies according to the severity. Such studies could contribute to the management of the disease.
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Affiliation(s)
- J B Pankoui Mfonkeu
- Department of Biochemistry, Faculty of Science, University of Douala, Cameroon
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17
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Wykes MN, Good MF. What really happens to dendritic cells during malaria? Nat Rev Microbiol 2008; 6:864-70. [DOI: 10.1038/nrmicro1988] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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18
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Mphande FA, Ribacke U, Kaneko O, Kironde F, Winter G, Wahlgren M. SURFIN4.1, a schizont-merozoite associated protein in the SURFIN family of Plasmodium falciparum. Malar J 2008; 7:116. [PMID: 18593471 PMCID: PMC2515329 DOI: 10.1186/1475-2875-7-116] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2007] [Accepted: 07/01/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In its effort to survive the human immune system, Plasmodium falciparum uses several parasite-derived antigens most of which are expressed at the surface of the parasitized red blood cells (pRBCs). Recently SURFINs, a new family of antigens encoded by the surf multi-gene family, has been reported. One member of the family, SURFIN4.2, was found present both at the pRBC-surface and at the merozoite apex. METHODS The presence of a second SURFIN member, SURFIN4.1 (PFD0100c, PFD0105c) is reported here. Bioinformatic tools were used to study the structure of the surf4.1 gene. To investigate the expression of surf genes PCR and real-time quantitative PCR (Rt-QPCR) were employed and Northern and Western blots were used to confirm the size of the surf4.1 gene and the SURFIN4.1 protein respectively. Localization of SURFIN4.1 was determined using immunofluorescence assays. RESULTS The surf4.1 gene was found present in one copy by Rt-QPCR in some parasites (3D7AH1, 3D7S8, 7G8) whereas six copies of the gene were identified in FCR3 and FCR3S1.2. surf4.1 was found transcribed in the late asexual stages of the parasite beginning approximately 32 hours post invasion and throughout the schizont stages with the level of transcription peaking at late schizogony. The levels of transcript correlated with the number of gene copies in FCR3 and 3D7S8. surf4.1 was found to encode a polypeptide of approximately Mw 258 kDa (SURFIN4.1) present within the parasitophorous vacuole (PV), around free merozoites as merozoite-associated material, but not at the pRBC-surface. Despite multiple surf4.1 gene copies in some parasites this was not reflected in the levels of SURFIN4.1 polypeptide. CONCLUSION SURFIN4.1 is a member of the SURFINs, present in the PV and on the released merozoite. The results suggest different SURFINs to be expressed at different locations in the parasite and at distinct time-points during the intra-erythrocytic cycle.
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Affiliation(s)
- Fingani A Mphande
- Department of Microbiology, Tumor and Cell Biology (MTC) Karolinska Institutet and Swedish Institute for Infectious Disease Control, Nobel's väg 16, Box 280, SE-171 77, Stockholm, Sweden
| | - Ulf Ribacke
- Department of Microbiology, Tumor and Cell Biology (MTC) Karolinska Institutet and Swedish Institute for Infectious Disease Control, Nobel's väg 16, Box 280, SE-171 77, Stockholm, Sweden
| | - Osamu Kaneko
- Department of Protozoology, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan
| | - Fred Kironde
- Department of Biochemistry, Makerere University, Kampala, Uganda
| | - Gerhard Winter
- Department of Microbiology, Tumor and Cell Biology (MTC) Karolinska Institutet and Swedish Institute for Infectious Disease Control, Nobel's väg 16, Box 280, SE-171 77, Stockholm, Sweden
- Department of General Practice, Flinders University, Adelaide, Australia
| | - Mats Wahlgren
- Department of Microbiology, Tumor and Cell Biology (MTC) Karolinska Institutet and Swedish Institute for Infectious Disease Control, Nobel's väg 16, Box 280, SE-171 77, Stockholm, Sweden
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19
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Bull PC, Buckee CO, Kyes S, Kortok MM, Thathy V, Guyah B, Stoute JA, Newbold CI, Marsh K. Plasmodium falciparum antigenic variation. Mapping mosaic var gene sequences onto a network of shared, highly polymorphic sequence blocks. Mol Microbiol 2008; 68:1519-34. [PMID: 18433451 PMCID: PMC2440560 DOI: 10.1111/j.1365-2958.2008.06248.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is a potentially important family of immune targets, encoded by an extremely diverse gene family called var. Understanding of the genetic organization of var genes is hampered by sequence mosaicism that results from a long history of non-homologous recombination. Here we have used software designed to analyse social networks to visualize the relationships between large collections of short var sequences tags sampled from clinical parasite isolates. In this approach, two sequences are connected if they share one or more highly polymorphic sequence blocks. The results show that the majority of analysed sequences including several var-like sequences from the chimpanzee parasite Plasmodium reichenowi can be either directly or indirectly linked together in a single unbroken network. However, the network is highly structured and contains putative subgroups of recombining sequences. The major subgroup contains the previously described group A var genes, previously proposed to be genetically distinct. Another subgroup contains sequences found to be associated with rosetting, a parasite virulence phenotype. The mosaic structure of the sequences and their division into subgroups may reflect the conflicting problems of maximizing antigenic diversity and minimizing epitope sharing between variants while maintaining their host cell binding functions.
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Affiliation(s)
- Peter C Bull
- Kenya Medical Research Institute, Centre for Geographic Medicine Research, Coast, Kilifi, Kenya.
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20
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Wykes M, Good MF. A case for whole-parasite malaria vaccines. Int J Parasitol 2007; 37:705-12. [PMID: 17408673 DOI: 10.1016/j.ijpara.2007.02.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2006] [Revised: 02/13/2007] [Accepted: 02/15/2007] [Indexed: 10/23/2022]
Abstract
Malaria causes morbidity in 300-500 million people each year and claims 2-3 millions lives annually, mostly children in sub-Saharan Africa. In 1983, the cloning of malaria antigens offered great promise for developing a viable subunit vaccine. However, an efficacious human vaccine is still not available. Immunological studies on how the host's immune system interacts with the parasite and studies on the pathogenic aspect of Plasmodium have found that several factors can impede protection by current vaccines. These findings suggest a novel approach needs to be considered.
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Affiliation(s)
- Michelle Wykes
- The Queensland Institute of Medical Research, The Bancroft Centre, Brisbane, Qld, Australia.
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21
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Joergensen L, Vestergaard LS, Turner L, Magistrado P, Lusingu JP, Lemnge M, Theander TG, Jensen ATR. 3D7-DerivedPlasmodium falciparumErythrocyte Membrane Protein 1 Is a Frequent Target of Naturally Acquired Antibodies Recognizing Protein Domains in a Particular Pattern Independent of Malaria Transmission Intensity. THE JOURNAL OF IMMUNOLOGY 2006; 178:428-35. [PMID: 17182581 DOI: 10.4049/jimmunol.178.1.428] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Protection against Plasmodium falciparum malaria is largely mediated by IgG against surface Ags such as the erythrocyte membrane protein 1 family (PfEMP1) responsible for antigenic variation and sequestration of infected erythrocytes. PfEMP1 molecules can be divided into groups A, B/A, B, C, and B/C. We have previously suggested that expression of groups A and B/A PfEMP1 is associated with severe disease and that Abs to these molecules are acquired earlier in life than Abs to PfEMP1 belonging to groups B, B/C, and C PfEMP1. In this study, we compared the acquisition of IgG to 20 rPfEMP1 domains derived from 3D7 in individuals living under markedly different malaria transmission intensity and were unable to find differences in the Ab acquisition rate to PfEMP1 of different groupings (A, B, or C) or domain type (alpha, beta, gamma, delta, epsilon, or x). Abs were acquired early in life in individuals living in the high transmission village and by the age of 2-4 years most individuals had Abs against most constructs. This level of reactivity was found at the age of 10-20 years in the medium transmission village and was never reached by individuals living under low transmission. Nevertheless, the sequence by which individuals acquired Abs to particular constructs was largely the same in the three villages. This indicates that the pattern of PfEMP1 expression by parasites transmitted at the different sites was similar, suggesting that PfEMP1 expression is nonrandom and shaped by host-parasite relationship factors operating at all transmission intensities.
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Affiliation(s)
- Louise Joergensen
- Centre for Medical Parasitology, Department of Medical Microbiology and Immunology, University of Copenhagen and Copenhagen University Hospital, Copenhagen, Denmark
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22
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Ahuja S, Pettersson F, Moll K, Jonsson C, Wahlgren M, Chen Q. Induction of cross-reactive immune responses to NTS-DBL-1alpha/x of PfEMP1 and in vivo protection on challenge with Plasmodium falciparum. Vaccine 2006; 24:6140-54. [PMID: 16837110 DOI: 10.1016/j.vaccine.2006.05.030] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2005] [Revised: 04/28/2006] [Accepted: 05/09/2006] [Indexed: 10/24/2022]
Abstract
The interactions of Plasmodium falciparum infected erythrocytes parasitized red blood cells (pRBC) with endothelial receptors and erythrocytes are mediated by multiple Duffy-binding like (DBL) and cysteine-rich interdomain region (CIDR) domains harboured in the Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1). The success of a subunit vaccine based on PfEMP1 depends on its ability to elicit cross-reactive responses to a substantial number of PfEMP1 variants. We have here evaluated serological PfEMP1 cross-reactivity by immunizing rats with phylogenetically diverse recombinant NTS-DBL-1alpha/x fusion domains from the 3D7 genome parasite emulsified in Montanide ISA 720. Cross-reactivity was elicited to these diverse DBL-1alpha/x domains as measured by ELISA and by immunoblotting. Employing a novel in vivo model of human infected erythrocyte sequestration, immunized animals were challenged with the FCR3S1.2 clone and cross-protection in terms of reduction in lung sequestration amounting to approximately 50% was demonstrated. Our results suggest that immunization with phylogenetically distant DBL-1alpha/x variants, can elicit partial cross-protection to challenge with the parasites harbouring a distant variant. These observations have implications for the design of multi-component vaccines against P. falciparum malaria.
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Affiliation(s)
- Sanjay Ahuja
- Microbiology and Tumor Biology Center (MTC), Karolinska Institute, P.O. Box 280, SE-17177 Stockholm, Sweden
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23
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Idro R, Aloyo J, Mayende L, Bitarakwate E, John CC, Kivumbi GW. Severe malaria in children in areas with low, moderate and high transmission intensity in Uganda. Trop Med Int Health 2006; 11:115-24. [PMID: 16398762 DOI: 10.1111/j.1365-3156.2005.01518.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVES Age and transmission intensity are known to influence the manifestations of severe falciparum malaria in African children. However, it is unclear how specific clinical features such as seizures, impairment of consciousness, or respiratory distress vary with the parasite load and transmission intensity. We examined how the peripheral parasite load varies with transmission intensity and how this influences the symptoms and manifestations of severe malaria in children under 5 years in three areas with different malaria transmission intensity across Uganda. METHODS We consecutively recruited 617 children with severe malaria presenting to three hospitals in areas with very low (51), moderate (367) and very high (199) transmission intensities and compared the age, admission parasite density and proportions of patients with different manifestations of severe disease. RESULTS The median age (months) was inversely proportional to transmission intensity and declined with rising transmission (26.4 in very low, 18.0 in moderate and 9.0 under very high transmission). The highest proportion of patients reporting previous malaria admissions came from the area with moderate transmission. The geometric mean parasite density (18,357, 32,508 and 95,433/microl) and the proportion of patients with seizures (13.7%, 36.8% and 45.7%, P < 0.001) from very low, moderate and very high transmission respectively, increased with rising transmission. A linear increase with transmission was also observed in the proportion of those with repeated seizures (9.8%, 13.4% and 30.2%, P < 0.001) or impaired consciousness (7.8%, 12.8% and 18.1%, P = 0.029) but not respiratory distress. The proportion of patients with severe anaemia (19.6%, 24.8% and 37.7%, P = 0.002) mirrored that of patients with seizures. CONCLUSIONS These findings suggest that heavy Plasmodium falciparum parasitaemia may be important in development of seizures, severe malarial anaemia and impaired consciousness in children under 5 years of age but may not be important in the development of respiratory distress.
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Affiliation(s)
- R Idro
- Department of Paediatrics and Child Health, Mulago Hospital/Makerere University Medical School, Kampala, Uganda.
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24
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A-Elgadir TME, Theander TG, Elghazali G, Nielsen MA, A-Elbasit IE, Adam I, Troye-Blomberg M, Elbashir MI, Giha HA. Determinants of Variant Surface Antigen Antibody Response in Severe Plasmodium falciparum Malaria in an Area of Low and Unstable Malaria Transmission. Scand J Immunol 2006; 63:232-40. [PMID: 16499577 DOI: 10.1111/j.1365-3083.2006.01732.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The variant surface antigens (VSA) of infected erythrocytes are important pathogenic markers, a set of variants (VSA(SM)), were assumed to be associated with severe malaria (SM), while SM constitutes clinically diverse forms, such as, severe malarial anemia (SMA) and cerebral malaria (CM). This study was conducted in Eastern Sudan, an area of seasonal and unstable malaria transmission. Parasites and plasma were obtained from patients with different clinical grades of malaria, and flow cytometry was used for analysis of VSA antibody (Ab) response. We found that individuals recognized a broader range of isolates had a higher level of VSA Ab against the recognized isolates (correlation coefficient, 0.727, P<0.001). Unexpectedly, at the time of malaria diagnosis, plasma from patients with CM recognized a significantly larger number of isolates than did the plasma from patients with SMA (P<0.001). Parasites obtained from patients with SMA or from children were better recognized than isolates obtained from patients with uncomplicated malaria or from adults, P<0.001, P=0.021, respectively. Taken together, the above findings suggest that the limitations in the VSA immunoglobulin G repertoire were most probably contributing to the pathogenesis of SMA but not to that of CM.
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Affiliation(s)
- T M E A-Elgadir
- Malaria Research Centre (MalRC), Department of Biochemistry; Faculty of Medicine, University of Khartoum, Khartoum, Sudan
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25
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Wykes MN, Zhou YH, Liu XQ, Good MF. Plasmodium yoelii can ablate vaccine-induced long-term protection in mice. THE JOURNAL OF IMMUNOLOGY 2005; 175:2510-6. [PMID: 16081823 DOI: 10.4049/jimmunol.175.4.2510] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Malaria is a serious cause of morbidity and mortality for people living in endemic areas, but unlike many other infections, individuals exposed to the parasite do not rapidly become resistant to subsequent infections. High titers of Ab against the 19-kDa C-terminal fragment of the merozoite surface protein-1 can mediate complete protection in model systems; however, previous studies had not determined whether this vaccine generated long-term protection. In this study, we report that functional memory cells generated by merozoite surface protein-1, per se, do not offer any protection. This is because the parasite induces deletion of vaccine-specific memory B cells as well as long-lived plasma cells including those specific for bystander immune responses. Our study demonstrates a novel mechanism by which Plasmodium ablates immunological memory of vaccines, which would leave the host immuno-compromised.
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Affiliation(s)
- Michelle N Wykes
- Molecular Immunology Laboratory, Queensland Institute of Medical Research, Brisbane, Queensland, Australia
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26
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Abstract
The erythrocytic cycle of Plasmodium falciparum presents a particularity in relation to other Plasmodium species that infect man. Mature trophozoites and schizonts are sequestered from the peripheral circulation due to adhesion of infected erythrocytes to host endothelial cells. Modifications in the surface of infected erythrocytes, termed knobs, seem to facilitate adhesion to endothelium and other erythrocytes. Adhesion provides better maturation in the microaerophilic venous atmosphere and allows the parasite to escape clearance by the spleen which recognizes the erythrocytes loss of deformability. Adhesion to the endothelium, or cytoadherence, has an important role in the pathogenicity of the disease, causing occlusion of small vessels and contributing to failure of many organs. Cytoadherence can also describe adhesion of infected erythrocytes to uninfected erythrocytes, a phenomenon widely known as rosetting. Clinical aspects of severe malaria, as well as the host receptors and parasite ligands involved in cytoadherence and rosetting, are reviewed here. The erythrocyte membrane protein 1 of P. falciparum (PfEMP1) appears to be the principal adhesive ligand of infected erythrocytes and will be discussed in more detail. Understanding the role of host receptors and parasite ligands in the development of different clinical syndromes is urgently needed to identify vaccination targets in order to decrease the mortality rates of this disease.
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Affiliation(s)
- Karin Kirchgatter
- Núcleo de Estudos em Malária, Superintendência de Controle de Endemias (SUCEN), Instituto de Medicina Tropical de São Paulo (IMTSP), Universidade de São Paulo (USP), São Paulo, SP 05403-000, Brazil.
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27
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Chen Q, Pettersson F, Vogt AM, Schmidt B, Ahuja S, Liljeström P, Wahlgren M. Immunization with PfEMP1-DBL1alpha generates antibodies that disrupt rosettes and protect against the sequestration of Plasmodium falciparum-infected erythrocytes. Vaccine 2004; 22:2701-12. [PMID: 15246600 DOI: 10.1016/j.vaccine.2004.02.015] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2003] [Revised: 01/30/2004] [Accepted: 02/03/2004] [Indexed: 10/26/2022]
Abstract
A family of parasite antigens known as Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is believed to play an important role in the binding of infected erythrocytes to host receptors in the micro-vasculature. Available data advocates the existence of a subset of very adhesive (rosetting, auto-agglutinating) and antigenic PfEMP1s implicated as virulence factors. Serum antibodies that disrupt rosettes are rarely found in children with severe malaria but are frequent in those with mild disease suggesting that they may be protective. Here we have developed a Semliki forest virus (SFV) vaccine construct with a recombinant gene (mini-var gene) encoding a mini-PfEMP1 (DBL1alpha-TM-ATS) obtained from a particularly antigenic and rosetting parasite (FCR3S1.2). The mini-PfEMP1 is presented to the host mimicking the location of the native molecule at the infected erythrocyte surface. Antibodies generated by a regimen of priming with SFV RNA particles and boosting with a recombinant protein recognize the infected erythrocyte surface (immuno-fluorescence/rosette-disruption) and prevent the sequestration of P. falciparum-infected erythrocytes in an in vivo model of severe malaria. The data prove the involvement of DBL1alpha in the adhesion of infected- and uninfected erythrocytes and the role of rosette-disruptive antibodies in preventing these cellular interactions. The work supports the use of DBL1alpha in a vaccine again severe malaria.
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Affiliation(s)
- Qijun Chen
- Microbiology and Tumorbiology Centre, Karolinska Institutet, Box 280, SE-171 77 Stockholm, Sweden.
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Mackinnon MJ, Read AF. Virulence in malaria: an evolutionary viewpoint. Philos Trans R Soc Lond B Biol Sci 2004; 359:965-86. [PMID: 15306410 PMCID: PMC1693375 DOI: 10.1098/rstb.2003.1414] [Citation(s) in RCA: 197] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Malaria parasites cause much morbidity and mortality to their human hosts. From our evolutionary perspective, this is because virulence is positively associated with parasite transmission rate. Natural selection therefore drives virulence upwards, but only to the point where the cost to transmission caused by host death begins to outweigh the transmission benefits. In this review, we summarize data from the laboratory rodent malaria model, Plasmodium chabaudi, and field data on the human malaria parasite, P. falciparum, in relation to this virulence trade-off hypothesis. The data from both species show strong positive correlations between asexual multiplication, transmission rate, infection length, morbidity and mortality, and therefore support the underlying assumptions of the hypothesis. Moreover, the P. falciparum data show that expected total lifetime transmission of the parasite is maximized in young children in whom the fitness cost of host mortality balances the fitness benefits of higher transmission rates and slower clearance rates, thus exhibiting the hypothesized virulence trade-off. This evolutionary explanation of virulence appears to accord well with the clinical and molecular explanations of pathogenesis that involve cytoadherence, red cell invasion and immune evasion, although direct evidence of the fitness advantages of these mechanisms is scarce. One implication of this evolutionary view of virulence is that parasite populations are expected to evolve new levels of virulence in response to medical interventions such as vaccines and drugs.
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Affiliation(s)
- Margaret J Mackinnon
- School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, Scotland, UK.
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29
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Cabrera G, Yone C, Tebo AE, van Aaken J, Lell B, Kremsner PG, Luty AJF. Immunoglobulin G isotype responses to variant surface antigens of Plasmodium falciparum in healthy Gabonese adults and children during and after successive malaria attacks. Infect Immun 2004; 72:284-94. [PMID: 14688107 PMCID: PMC344001 DOI: 10.1128/iai.72.1.284-294.2004] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2003] [Revised: 09/29/2003] [Accepted: 10/08/2003] [Indexed: 11/20/2022] Open
Abstract
We assessed immunoglobulin G (IgG) isotype responses with specificity for the variant surface antigens (VSA) of heterologous Plasmodium falciparum isolates by using flow cytometry and plasma from healthy Gabonese adults and from children during and after two consecutive malaria episodes. The individual isolate-specific antibody profiles differed markedly in terms of their isotype content but were similar for healthy adults and healthy uninfected children. In healthy adults, IgG3 and IgG2 responses were the highest, while in healthy children, IgG3 and IgG4 predominated. A transiently elevated IgG1 response was observed during the second of two successive malaria episodes in children, signaling P. falciparum infection-induced cross-reactive anti-VSA responses. Our findings highlight the prominence of IgG3 in the overall profile of these responses but also indicate a marked age-related increase in the prevalence of anti-VSA antibodies of the classically noncytophilic IgG2 isotype, possibly reflecting the high frequency of the histidine-131 variant of FcgammaRIIA in the Gabonese population.
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Affiliation(s)
- Gerardo Cabrera
- Department of Parasitology, Institute for Tropical Medicine, University of Tübingen, D-72074 Tübingen, Germany
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Baruch DI, Gamain B, Miller LH. DNA immunization with the cysteine-rich interdomain region 1 of the Plasmodium falciparum variant antigen elicits limited cross-reactive antibody responses. Infect Immun 2003; 71:4536-43. [PMID: 12874333 PMCID: PMC166004 DOI: 10.1128/iai.71.8.4536-4543.2003] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The variant surface antigens of Plasmodium falciparum are an important component of naturally acquired immunity and an important vaccine target. However, these proteins appear to elicit primarily variant-specific antibodies. We tested if naked DNA immunization can elicit more cross-reactive antibody responses and allow simultaneous immunization with several variant constructs. Mice immunized with plasmid DNA expressing variant cysteine-rich interdomain region 1 (CIDR1) domains of the P. falciparum erythrocyte membrane protein 1 (PfEMP1) developed antibodies that were reactive to the corresponding PfEMP1s as measured by an enzyme-linked immunosorbent assay, flow cytometry, and agglutination of parasitized erythrocytes (PEs). We observed some cross-reactive immune responses; for example, sera from mice immunized with one domain agglutinated PEs of various lines and recognized heterologous domains expressed on the surface of Chinese hamster ovary (CHO) cells. We found no significant antigenic competition when animals were immunized with a mixture of plasmids or immunized sequentially with individual constructs. Moreover, mixed or sequential immunizations resulted in greater cross-reactive agglutination responses than immunization with a single domain. Recombinant protein (Sc y179) immunization after priming with DNA (prime-boost regimen) increased antibody titers to the homologous domain substantially but seemed to diminish the cross-reactive responses somewhat. The titer of agglutinating antibodies was previously shown to correlate with protection. Surprisingly, the agglutination titers of sera from DNA immunization were high, similar to those of pooled human hyperimmune sera. These sera also appeared to give limited low-titer variant transcending agglutination. Thus, DNA immunization appears to be a very useful tool for developing variant antigen vaccines.
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Affiliation(s)
- Dror I Baruch
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Tebo AE, Kremsner PG, Luty AJ. Plasmodium falciparum: a major role for IgG3 in antibody-dependent monocyte-mediated cellular inhibition of parasite growth in vitro. Exp Parasitol 2001; 98:20-8. [PMID: 11426948 DOI: 10.1006/expr.2001.4619] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In an attempt to identify parasite antigen-specific antibody isotype(s) mediating inhibition of growth in vitro, we tested unfractionated sera and their corresponding purified antibody isotype-containing fractions in in vitro assays with asexual-stage parasites of Plasmodium falciparum in the presence or absence of monocytes. Using affinity purification techniques we fractionated individual and pooled serum samples from semi-immune Gabonese adults, to obtain samples containing either IgG1, 2, 3, and 4, IgG1, 2, and 4, or IgG3 alone, and a non-IgG fraction. Antibodies were quantified spectrophotometrically and the presence of different isotypes in individual fractions was confirmed by protein gel electrophoresis. In the absence of monocytes, we observed inhibition of parasite growth with whole serum and varying levels of either growth enhancement or inhibition with purified Ig-containing fractions. When used in a standardized assay of antibody-dependent cellular inhibition (ADCI) with a monocyte:infected erythrocyte ratio of 1:1, seven of eight serum samples inhibited growth to a mean level of 42%, and the different Ig-containing fractions displayed varying mean levels of inhibition: IgG3, 44%; IgG1--4, 22%; IgG1, 2, and 4, 10%; and non-IgG, - 10%. The results suggest that, among the different isotypes present in the serum of semi-immune individuals, parasite antigen-specific IgG3 in particular may play an important role in controlling parasitemia via an ADCI mechanism involving monocyte- derived mediators.
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Affiliation(s)
- A E Tebo
- Department of Parasitology, Institute of Tropical Medicine, University of Tübingen, Wilhelmstrasse 27, 72074 Tübingen, Germany
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Gamain B, Miller LH, Baruch DI. The surface variant antigens of Plasmodium falciparum contain cross-reactive epitopes. Proc Natl Acad Sci U S A 2001; 98:2664-9. [PMID: 11226296 PMCID: PMC30195 DOI: 10.1073/pnas.041602598] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Plasmodium falciparum parasites evade the host immune system by clonal expression of the variant antigen, P. falciparum erythrocyte membrane protein 1 (PfEMP1). Antibodies to PfEMP1 correlate with development of clinical immunity but are predominantly variant-specific. To overcome this major limitation for vaccine development, we set out to identify cross-reactive epitopes on the surface of parasitized erythrocytes (PEs). We prepared mAbs to the cysteine-rich interdomain region 1 (CIDR1) of PfEMP1 that is functionally conserved for binding to CD36. Two mAbs, targeting different regions of CIDR1, reacted with multiple P. falciparum strains expressing variant PfEMP1s. One of these mAbs, mAb 6A2-B1, recognized nine of 10 strains tested, failing to react with only one strain that does not bind CD36. Flow cytometry with Chinese hamster ovary cells expressing variant CIDR1s demonstrated that both mAbs recognized the CIDR1 of various CD36-binding PfEMP1s and are truly cross-reactive. The demonstration of cross-reactive epitopes on the PE surface provides further credence for development of effective vaccines against the variant antigen on the surface of P. falciparum-infected erythrocytes.
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Affiliation(s)
- B Gamain
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 4 Center Drive MSC 0425, Bethesda, MD 20892, USA
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Abstract
Human infections with Plasmodium falciparum may result in severe forms of malaria. The widespread and rapid development of drug resistance in P. falciparum and the resistance of the disease-transmitting mosquitoes to insecticides make it urgent to understand the molecular background of the pathogenesis of malaria to enable the development of novel approaches to combat the disease. This review focuses on the molecular mechanisms of severe malaria caused by the P. falciparum parasite. The nature of severe malaria and the deleterious effects of parasite-derived toxins and host-induced cytokines are introduced. Sequestration, brought about by cytoadherence and rosetting, is linked to severe malaria and is mediated by multiple receptors on the endothelium and red blood cells. P. falciparum erythrocyte membrane protein 1 (PfEMP1) is the ligand responsible for a majority of binding interactions, and the multiply adhesive features of this sticky molecule are presented. Antigenic variation is also a major feature of PfEMP1 and of the surface of the P. falciparum-infected erythrocyte. Possible mechanisms of P. falciparum antigenic variation in asexual stages are further discussed. We conclude this review with a perspective and suggestions of important aspects for future investigations.
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Abstract
Human infections with Plasmodium falciparum may result in severe forms of malaria. The widespread and rapid development of drug resistance in P. falciparum and the resistance of the disease-transmitting mosquitoes to insecticides make it urgent to understand the molecular background of the pathogenesis of malaria to enable the development of novel approaches to combat the disease. This review focuses on the molecular mechanisms of severe malaria caused by the P. falciparum parasite. The nature of severe malaria and the deleterious effects of parasite-derived toxins and host-induced cytokines are introduced. Sequestration, brought about by cytoadherence and rosetting, is linked to severe malaria and is mediated by multiple receptors on the endothelium and red blood cells. P. falciparum erythrocyte membrane protein 1 (PfEMP1) is the ligand responsible for a majority of binding interactions, and the multiply adhesive features of this sticky molecule are presented. Antigenic variation is also a major feature of PfEMP1 and of the surface of the P. falciparum-infected erythrocyte. Possible mechanisms of P. falciparum antigenic variation in asexual stages are further discussed. We conclude this review with a perspective and suggestions of important aspects for future investigations.
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Affiliation(s)
- Q Chen
- Microbiology and Tumour Biology Centre, Karolinska Institutet, and Swedish Institute for Infectious Disease Control, S-171 77 Stockholm, Sweden
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Barragan A, Kremsner PG, Wahlgren M, Carlson J. Blood group A antigen is a coreceptor in Plasmodium falciparum rosetting. Infect Immun 2000; 68:2971-5. [PMID: 10768996 PMCID: PMC97511 DOI: 10.1128/iai.68.5.2971-2975.2000] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The malaria parasite Plasmodium falciparum utilizes molecules present on the surface of uninfected red blood cells (RBC) for rosette formation, and a dependency on ABO antigens has been previously shown. In this study, the antirosetting effect of immune sera was related to the blood group of the infected human host. Sera from malaria-immune blood group A (or B) individuals were less prone to disrupt rosettes from clinical isolates of blood group A (or B) patients than to disrupt rosettes from isolates of blood group O patients. All fresh clinical isolates and laboratory strains exhibited distinct ABO blood group preferences, indicating that utilization of blood group antigens is a general feature of P. falciparum rosetting. Soluble A antigen strongly inhibited rosette formation when the parasite was cultivated in A RBC, while inhibition by glycosaminoglycans decreased. Furthermore, a soluble A antigen conjugate bound to the cell surface of parasitized RBC. Selective enzymatic digestion of blood group A antigen from the uninfected RBC surfaces totally abolished the preference of the parasite to form rosettes with these RBC, but rosettes could still form. Altogether, present data suggest an important role for A and B antigens as coreceptors in P. falciparum rosetting.
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Affiliation(s)
- A Barragan
- Microbiology and Tumor Biology Center, Karolinska Institutet, and Swedish Institute for Infectious Disease Control, Stockholm, Sweden
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36
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O'Connor RM, Allred DR. Selection of Babesia bovis-infected erythrocytes for adhesion to endothelial cells coselects for altered variant erythrocyte surface antigen isoforms. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 164:2037-45. [PMID: 10657656 DOI: 10.4049/jimmunol.164.4.2037] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Sequestration of Babesia bovis-infected erythrocytes (IRBCs) in the host microvasculature is thought to constitute an important mechanism of immune evasion. Since Ig is considered to be important for protection from disease, an in vitro assay of B. bovis sequestration was used to explore the ability of anti-B. bovis Ig to interfere with IRBC cytoadhesion, and to identify IRBC surface Ags acting as endothelial cell receptors. Bovine infection sera reactive with the IRBC surface inhibited and even reversed the binding of IRBCs to bovine brain capillary endothelial cells (BBECs). This activity is at least partially attributable to serum IgG. IgG isolated from inhibitory serum captured the variant erythrocyte surface ag 1 (VESA1) in surface-specific immunoprecipitations of B. bovis-IRBCs. Selection for the cytoadhesive phenotype concurrently selected for antigenic and structural changes in the VESA1 Ag. In addition, the anti-VESA1 mAb, 4D9.1G1, proved capable of effectively inhibiting and reversing binding of adhesive, mAb-reactive parasites to BBECs, and by immunoelectron microscopy localized VESA1 to the external tips of the IRBC membrane knobs. These data are consistent with a link between antigenic variation and cytoadherence in B. bovis and suggest that the VESA1 Ag acts as an endothelial cell ligand on the B. bovis-IRBC.
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MESH Headings
- Animals
- Antibodies, Monoclonal/pharmacology
- Antigen-Antibody Reactions
- Antigens, Protozoan/biosynthesis
- Antigens, Protozoan/blood
- Antigens, Protozoan/immunology
- Antigens, Protozoan/isolation & purification
- Antigens, Surface/biosynthesis
- Antigens, Surface/blood
- Antigens, Surface/immunology
- Antigens, Surface/isolation & purification
- Babesia bovis/immunology
- Binding Sites, Antibody
- Cattle
- Cell Adhesion/immunology
- Endothelium, Vascular/cytology
- Endothelium, Vascular/immunology
- Endothelium, Vascular/parasitology
- Erythrocytes/immunology
- Erythrocytes/parasitology
- Immune Sera/pharmacology
- Immunoglobulin G/pharmacology
- Phenotype
- Protein Isoforms/biosynthesis
- Rosette Formation
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Affiliation(s)
- R M O'Connor
- Department of Pathobiology, College of Veterinary Medicine, University of Florida, Gainesville, FL 32611, USA
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37
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Fernandez V, Hommel M, Chen Q, Hagblom P, Wahlgren M. Small, clonally variant antigens expressed on the surface of the Plasmodium falciparum-infected erythrocyte are encoded by the rif gene family and are the target of human immune responses. J Exp Med 1999; 190:1393-404. [PMID: 10562315 PMCID: PMC2195703 DOI: 10.1084/jem.190.10.1393] [Citation(s) in RCA: 158] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Disease severity in Plasmodium falciparum infections is a direct consequence of the parasite's efficient evasion of the defense mechanisms of the human host. To date, one parasite-derived molecule, the antigenically variant adhesin P. falciparum erythrocyte membrane protein 1 (PfEMP1), is known to be transported to the infected erythrocyte (pRBC) surface, where it mediates binding to different host receptors. Here we report that multiple additional proteins are expressed by the parasite at the pRBC surface, including a large cluster of clonally variant antigens of 30-45 kD. We have found these antigens to be identical to the rifins, predicted polypeptides encoded by the rif multigene family. These parasite products, formerly called rosettins after their identification in rosetting parasites, are prominently expressed by fresh isolates of P. falciparum. Rifins are immunogenic in natural infections and strain-specifically recognized by human immune sera in immunoprecipitation of surface-labeled pRBC extracts. Furthermore, human immune sera agglutinate pRBCs digested with trypsin at conditions such that radioiodinated PfEMP1 polypeptides are not detected but rifins are detected, suggesting the presence of epitopes in rifins targeted by agglutinating antibodies. When analyzed by two-dimensional electrophoresis, the rifins resolved into several isoforms in the pI range of 5.5-6.5, indicating molecular microheterogeneity, an additional potential novel source of antigenic diversity in P. falciparum. Prominent polypeptides of 20, 22, 76-80, 140, and 170 kD were also detected on the surfaces of pRBCs bearing in vitro-propagated or field-isolated parasites. In this report, we describe the rifins, the second family of clonally variant antigens known to be displayed by P. falciparum on the surface of the infected erythrocyte.
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Affiliation(s)
- Victor Fernandez
- Microbiology and Tumor Biology Center, Karolinska Institutet, and the Swedish Institute for Infectious Disease Control, S-17177 Stockholm, Sweden
| | - Marcel Hommel
- Department of Tropical Medicine and Infectious Diseases, Liverpool School of Tropical Medicine, Liverpool L3QA, United Kingdom
| | - Qijun Chen
- Microbiology and Tumor Biology Center, Karolinska Institutet, and the Swedish Institute for Infectious Disease Control, S-17177 Stockholm, Sweden
| | - Per Hagblom
- Microbiology and Tumor Biology Center, Karolinska Institutet, and the Swedish Institute for Infectious Disease Control, S-17177 Stockholm, Sweden
| | - Mats Wahlgren
- Microbiology and Tumor Biology Center, Karolinska Institutet, and the Swedish Institute for Infectious Disease Control, S-17177 Stockholm, Sweden
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38
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O'Connor RM, Long JA, Allred DR. Selection and recovery of minor parasite populations expressing unique infected-erythrocyte phenotypes. Mol Biochem Parasitol 1999; 100:125-9. [PMID: 10377000 DOI: 10.1016/s0166-6851(99)00027-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- R M O'Connor
- Department of Pathobiology, University of Florida, College of Veterinary Medicine, Gainesville 32611-0880, USA
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