1
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Nganyewo NN, Bojang F, Oriero EC, Drammeh NF, Ajibola O, Mbye H, Jawara AS, Corea S, Awandare GA, D'Alessandro U, Amenga-Etego LN, Amambua-Ngwa A. Recent increase in low complexity polygenomic infections and sialic acid-independent invasion pathways in Plasmodium falciparum from Western Gambia. Parasit Vectors 2023; 16:309. [PMID: 37653544 PMCID: PMC10472613 DOI: 10.1186/s13071-023-05929-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2023] [Accepted: 08/14/2023] [Indexed: 09/02/2023] Open
Abstract
BACKGROUND The malaria parasite Plasmodium falciparum utilizes multiple alternative receptor-ligand interactions for the invasion of human erythrocytes. While some P. falciparum clones make use of sialic acid (SA) residues on the surface of the human glycophorin receptors to invade the erythrocyte, others use alternative receptors independent of sialic acid residues. We hypothesized that over the years, intensified malaria control interventions and declining prevalence in The Gambia have resulted in a selection of parasites with a dominant invasion pathways and ligand expression profiles. METHODS Blood samples were collected from 65 malaria-infected participants with uncomplicated malaria across 3 years (2015, 2016, and 2021). Genetic diversity was determined by genotyping the merozoite surface protein 2 (msp2) polymorphic gene of P. falciparum. Erythrocyte invasion phenotypes were determined using neuraminidase, trypsin, and chymotrypsin enzymes, known to cleave different receptors from the surface of the erythrocyte. Schizont-stage transcript levels were obtained for a panel of 6 P. falciparum invasion ligand genes (eba175, eba181, Rh2b, Rh4, Rh5, and clag2) using 48 successfully cultured isolates. RESULTS Though the allelic heterozygosity of msp2 repeat region decreased as expected with reduced transmission, there was an increase in infections with more than a single msp2 allelotype from 2015 to 2021. The invasion phenotypes of these isolates were mostly SA independent with a continuous increase from 2015 to 2021. Isolates from 2021 were highly inhibited by chymotrypsin treatment compared to isolates from 2015 and 2016. Higher invasion inhibition for 2021 isolates was further obtained following erythrocyte treatment with a combination of chymotrypsin and trypsin. The transcript levels of invasion ligand genes varied across years. However, levels of clag2, a rhoptry-associated protein, were higher in 2015 and 2016 isolates than in 2021 isolates, while Rh5 levels were higher in 2021 compared to other years. CONCLUSIONS Overall, these findings suggest increasing mixed infections with an increase in the use of sialic-acid independent invasion pathways by P. falciparum clinical isolates in the Western part of Gambia.
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Affiliation(s)
- Nora Nghochuzie Nganyewo
- Medical Research Council Unit The Gambia at London, School of Hygiene and Tropical Medicine, Banjul, The Gambia
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, Accra, Ghana
| | - Fatoumata Bojang
- Medical Research Council Unit The Gambia at London, School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Eniyou Cheryll Oriero
- Medical Research Council Unit The Gambia at London, School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Ndey Fatou Drammeh
- Medical Research Council Unit The Gambia at London, School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Olumide Ajibola
- Medical Research Council Unit The Gambia at London, School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Haddijatou Mbye
- Medical Research Council Unit The Gambia at London, School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Aminata Seedy Jawara
- Medical Research Council Unit The Gambia at London, School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Simon Corea
- Medical Research Council Unit The Gambia at London, School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Gordon Akanzuwine Awandare
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, Accra, Ghana
| | - Umberto D'Alessandro
- Medical Research Council Unit The Gambia at London, School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Lucas N Amenga-Etego
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, Accra, Ghana
| | - Alfred Amambua-Ngwa
- Medical Research Council Unit The Gambia at London, School of Hygiene and Tropical Medicine, Banjul, The Gambia.
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2
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Triglia T, Scally SW, Seager BA, Pasternak M, Dagley LF, Cowman AF. Plasmepsin X activates the PCRCR complex of Plasmodium falciparum by processing PfRh5 for erythrocyte invasion. Nat Commun 2023; 14:2219. [PMID: 37072430 PMCID: PMC10113190 DOI: 10.1038/s41467-023-37890-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Accepted: 04/04/2023] [Indexed: 04/20/2023] Open
Abstract
Plasmodium falciparum causes the most severe form of malaria in humans. The protozoan parasite develops within erythrocytes to mature schizonts, that contain more than 16 merozoites, which egress and invade fresh erythrocytes. The aspartic protease plasmepsin X (PMX), processes proteins and proteases essential for merozoite egress from the schizont and invasion of the host erythrocyte, including the leading vaccine candidate PfRh5. PfRh5 is anchored to the merozoite surface through a 5-membered complex (PCRCR), consisting of Plasmodium thrombospondin-related apical merozoite protein, cysteine-rich small secreted protein, Rh5-interacting protein and cysteine-rich protective antigen. Here, we show that PCRCR is processed by PMX in micronemes to remove the N-terminal prodomain of PhRh5 and this activates the function of the complex unmasking a form that can bind basigin on the erythrocyte membrane and mediate merozoite invasion. The ability to activate PCRCR at a specific time in merozoite invasion most likely masks potential deleterious effects of its function until they are required. These results provide an important understanding of the essential role of PMX and the fine regulation of PCRCR function in P. falciparum biology.
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Affiliation(s)
- Tony Triglia
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
| | - Stephen W Scally
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Benjamin A Seager
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Michał Pasternak
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Laura F Dagley
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Alan F Cowman
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia.
- University of Melbourne, Melbourne, VIC, 3010, Australia.
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3
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De SL, Ntumngia FB, Nicholas J, Adams JH. Progress towards the development of a P. vivax vaccine. Expert Rev Vaccines 2021; 20:97-112. [PMID: 33481638 PMCID: PMC7994195 DOI: 10.1080/14760584.2021.1880898] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 01/21/2021] [Indexed: 02/07/2023]
Abstract
INTRODUCTION Plasmodium vivax causes significant public health problems in endemic regions. A vaccine to prevent disease is critical, considering the rapid spread of drug-resistant parasite strains, and the development of hypnozoites in the liver with potential for relapse. A minimally effective vaccine should prevent disease and transmission while an ideal vaccine provides sterile immunity. AREAS COVERED Despite decades of research, the complex life cycle, technical challenges and a lack of funding have hampered progress of P. vivax vaccine development. Here, we review the progress of potential P. vivax vaccine candidates from different stages of the parasite life cycle. We also highlight the challenges and important strategies for rational vaccine design. These factors can significantly increase immune effector mechanisms and improve the protective efficacy of these candidates in clinical trials to generate sustained protection over longer periods of time. EXPERT OPINION A vaccine that presents functionally-conserved epitopes from multiple antigens from various stages of the parasite life cycle is key to induce broadly neutralizing strain-transcending protective immunity to effectively disrupt parasite development and transmission.
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Affiliation(s)
- Sai Lata De
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, 3720 Spectrum Blvd, Tampa – 33612, FL
| | - Francis B. Ntumngia
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, 3720 Spectrum Blvd, Tampa – 33612, FL
| | - Justin Nicholas
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, 3720 Spectrum Blvd, Tampa – 33612, FL
| | - John H. Adams
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, 3720 Spectrum Blvd, Tampa – 33612, FL
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4
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Kepple D, Pestana K, Tomida J, Abebe A, Golassa L, Lo E. Alternative Invasion Mechanisms and Host Immune Response to Plasmodium vivax Malaria: Trends and Future Directions. Microorganisms 2020; 9:E15. [PMID: 33374596 PMCID: PMC7822457 DOI: 10.3390/microorganisms9010015] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 12/19/2020] [Accepted: 12/21/2020] [Indexed: 11/21/2022] Open
Abstract
Plasmodium vivax malaria is a neglected tropical disease, despite being more geographically widespread than any other form of malaria. The documentation of P. vivax infections in different parts of Africa where Duffy-negative individuals are predominant suggested that there are alternative pathways for P. vivax to invade human erythrocytes. Duffy-negative individuals may be just as fit as Duffy-positive individuals and are no longer resistant to P.vivax malaria. In this review, we describe the complexity of P. vivax malaria, characterize pathogenesis and candidate invasion genes of P. vivax, and host immune responses to P. vivax infections. We provide a comprehensive review on parasite ligands in several Plasmodium species that further justify candidate genes in P. vivax. We also summarize previous genomic and transcriptomic studies related to the identification of ligand and receptor proteins in P. vivax erythrocyte invasion. Finally, we identify topics that remain unclear and propose future studies that will greatly contribute to our knowledge of P. vivax.
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Affiliation(s)
- Daniel Kepple
- Biological Sciences, University of North Carolina, Charlotte, NC 28223, USA; (K.P.); (J.T.)
| | - Kareen Pestana
- Biological Sciences, University of North Carolina, Charlotte, NC 28223, USA; (K.P.); (J.T.)
| | - Junya Tomida
- Biological Sciences, University of North Carolina, Charlotte, NC 28223, USA; (K.P.); (J.T.)
| | - Abnet Abebe
- Ethiopian Public Health Institute, Addis Ababa 1000, Ethiopia;
| | - Lemu Golassa
- Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa 1000, Ethiopia;
| | - Eugenia Lo
- Biological Sciences, University of North Carolina, Charlotte, NC 28223, USA; (K.P.); (J.T.)
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5
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Gunalan K, Gao X, Yap SSL, Lai SK, Ravasio A, Ganesan S, Li HY, Preiser PR. A processing product of the Plasmodium falciparum reticulocyte binding protein RH1 shows a close association with AMA1 during junction formation. Cell Microbiol 2020; 22:e13232. [PMID: 32452132 DOI: 10.1111/cmi.13232] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Revised: 05/14/2020] [Accepted: 05/16/2020] [Indexed: 11/28/2022]
Abstract
Plasmodium falciparum responsible for the most virulent form of malaria invades human erythrocytes through multiple ligand-receptor interactions. The P. falciparum reticulocyte binding protein homologues (PfRHs) are expressed at the apical end of merozoites and form interactions with distinct erythrocyte surface receptors that are important for invasion. Here using a range of monoclonal antibodies (mAbs) against different regions of PfRH1 we have investigated the role of PfRH processing during merozoite invasion. We show that PfRH1 gets differentially processed during merozoite maturation and invasion and provide evidence that the different PfRH1 processing products have distinct functions during invasion. Using in-situ Proximity Ligation and FRET assays that allow probing of interactions at the nanometre level we show that a subset of PfRH1 products form close association with micronemal proteins Apical Membrane Antigen 1 (AMA1) in the moving junction suggesting a critical role in facilitating junction formation and active invasion. Our data provides evidence that time dependent processing of PfRH proteins is a mechanism by which the parasite is able to regulate distinct functional activities of these large processes. The identification of a specific close association with AMA1 in the junction now may also provide new avenues to target these interactions to prevent merozoite invasion.
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Affiliation(s)
- Karthigayan Gunalan
- Division of Molecular Genetics & Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.,Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA
| | - Xiaohong Gao
- Division of Molecular Genetics & Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Sally Shu Lin Yap
- Division of Molecular Genetics & Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Soak Kuan Lai
- Division of Molecular Genetics & Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Andrea Ravasio
- Division of Molecular Genetics & Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.,Institute of Biological and Medical Engineering of the Pontifical Catholic University of Chile, Chile
| | - Sundar Ganesan
- Research Technology Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Hoi Yeung Li
- Division of Molecular Genetics & Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Peter R Preiser
- Division of Molecular Genetics & Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
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6
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Favuzza P, de Lera Ruiz M, Thompson JK, Triglia T, Ngo A, Steel RWJ, Vavrek M, Christensen J, Healer J, Boyce C, Guo Z, Hu M, Khan T, Murgolo N, Zhao L, Penington JS, Reaksudsan K, Jarman K, Dietrich MH, Richardson L, Guo KY, Lopaticki S, Tham WH, Rottmann M, Papenfuss T, Robbins JA, Boddey JA, Sleebs BE, Sabroux HJ, McCauley JA, Olsen DB, Cowman AF. Dual Plasmepsin-Targeting Antimalarial Agents Disrupt Multiple Stages of the Malaria Parasite Life Cycle. Cell Host Microbe 2020; 27:642-658.e12. [PMID: 32109369 PMCID: PMC7146544 DOI: 10.1016/j.chom.2020.02.005] [Citation(s) in RCA: 81] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 12/22/2019] [Accepted: 02/11/2020] [Indexed: 01/07/2023]
Abstract
Artemisin combination therapy (ACT) is the main treatment option for malaria, which is caused by the intracellular parasite Plasmodium. However, increased resistance to ACT highlights the importance of finding new drugs. Recently, the aspartic proteases Plasmepsin IX and X (PMIX and PMX) were identified as promising drug targets. In this study, we describe dual inhibitors of PMIX and PMX, including WM382, that block multiple stages of the Plasmodium life cycle. We demonstrate that PMX is a master modulator of merozoite invasion and direct maturation of proteins required for invasion, parasite development, and egress. Oral administration of WM382 cured mice of P. berghei and prevented blood infection from the liver. In addition, WM382 was efficacious against P. falciparum asexual infection in humanized mice and prevented transmission to mosquitoes. Selection of resistant P. falciparum in vitro was not achievable. Together, these show that dual PMIX and PMX inhibitors are promising candidates for malaria treatment and prevention.
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Affiliation(s)
- Paola Favuzza
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; University of Melbourne, Melbourne, VIC 3010, Australia
| | | | - Jennifer K Thompson
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia
| | - Tony Triglia
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia
| | - Anna Ngo
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia
| | - Ryan W J Steel
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; University of Melbourne, Melbourne, VIC 3010, Australia
| | - Marissa Vavrek
- Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, USA
| | - Janni Christensen
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; University of Melbourne, Melbourne, VIC 3010, Australia
| | - Julie Healer
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; University of Melbourne, Melbourne, VIC 3010, Australia
| | | | - Zhuyan Guo
- Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, USA
| | - Mengwei Hu
- Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, USA
| | - Tanweer Khan
- Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, USA
| | - Nicholas Murgolo
- Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, USA
| | - Lianyun Zhao
- Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, USA
| | | | - Kitsanapong Reaksudsan
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; University of Melbourne, Melbourne, VIC 3010, Australia
| | - Kate Jarman
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia
| | - Melanie H Dietrich
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; University of Melbourne, Melbourne, VIC 3010, Australia
| | - Lachlan Richardson
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; University of Melbourne, Melbourne, VIC 3010, Australia
| | - Kai-Yuan Guo
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; University of Melbourne, Melbourne, VIC 3010, Australia
| | - Sash Lopaticki
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia
| | - Wai-Hong Tham
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; University of Melbourne, Melbourne, VIC 3010, Australia
| | | | - Tony Papenfuss
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; University of Melbourne, Melbourne, VIC 3010, Australia
| | | | - Justin A Boddey
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; University of Melbourne, Melbourne, VIC 3010, Australia
| | - Brad E Sleebs
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; University of Melbourne, Melbourne, VIC 3010, Australia
| | - Hélène Jousset Sabroux
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; University of Melbourne, Melbourne, VIC 3010, Australia
| | - John A McCauley
- Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, USA
| | - David B Olsen
- Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, USA.
| | - Alan F Cowman
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; University of Melbourne, Melbourne, VIC 3010, Australia.
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7
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Aniweh Y, Suurbaar J, Morang'a CM, Nyarko PB, Wright KE, Kusi KA, Ansah F, Kyei-Baafour E, Quansah E, Asante J, Thiam LG, Higgins MK, Awandare GA. Analysis of Plasmodium falciparum Rh2b deletion polymorphism across different transmission areas. Sci Rep 2020; 10:1498. [PMID: 32001728 PMCID: PMC6992740 DOI: 10.1038/s41598-020-58300-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 01/14/2020] [Indexed: 11/12/2022] Open
Abstract
Despite significant progress in controlling malaria, the disease remains a global health burden. The intricate interactions the parasite Plasmodium falciparum has with its host allows it to grow and multiply in human erythrocytes. The mechanism by which P. falciparum merozoites invade human erythrocytes is complex, involving merozoite proteins as well as erythrocyte surface proteins. Members of the P. falciparum reticulocyte binding-like protein homolog (PfRh) family of proteins play a pivotal role in merozoite invasion and hence are important targets of immune responses. Domains within the PfRh2b protein have been implicated in its ability to stimulate natural protective antibodies in patients. More specifically, a 0.58 kbp deletion, at the C-terminus has been reported in high frequencies in Senegalese and Southeast Asian parasite populations, suggesting a possible role in immune evasion. We analysed 1218 P. falciparum clinical isolates, and the results show that this deletion is present in Ghanaian parasite populations (48.5% of all isolates), with Kintampo (hyper-endemic, 53.2%), followed by Accra (Hypo-endemic, 50.3%), Cape Coast (meso-endemic, 47.9%) and Sogakope (meso-endemic, 43.15%). Further analysis of parasite genomes stored in the MalariaGEN database revealed that the deletion variant was common across transmission areas globally, with an overall frequency of about 27.1%. Interestingly, some parasite isolates possessed mixed PfRh2b deletion and full-length alleles. We further showed that levels of antibodies to the domain of PfRh2 protein were similar to antibody levels of PfRh5, indicating it is less recognized by the immune system.
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Affiliation(s)
- Yaw Aniweh
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana. .,Department of Biochemistry, Cell and Molecular Biology, College of Basic and Applied Sciences, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana.
| | - Jonathan Suurbaar
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana.,Department of Biochemistry, Cell and Molecular Biology, College of Basic and Applied Sciences, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana
| | - Collins M Morang'a
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana.,Department of Biochemistry, Cell and Molecular Biology, College of Basic and Applied Sciences, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana
| | - Prince B Nyarko
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana.,Department of Biochemistry, Cell and Molecular Biology, College of Basic and Applied Sciences, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana
| | - Katherine E Wright
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK.,Department of Life Sciences, Imperial College London, London, UK
| | - Kwadwo A Kusi
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana.,Department of Biochemistry, Cell and Molecular Biology, College of Basic and Applied Sciences, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana.,Immunology Department, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | - Felix Ansah
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana.,Department of Biochemistry, Cell and Molecular Biology, College of Basic and Applied Sciences, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana
| | - Eric Kyei-Baafour
- Immunology Department, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | - Evelyn Quansah
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana.,Department of Biochemistry, Cell and Molecular Biology, College of Basic and Applied Sciences, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana
| | - Jessica Asante
- Immunology Department, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | - Laty G Thiam
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana.,Department of Biochemistry, Cell and Molecular Biology, College of Basic and Applied Sciences, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana
| | - Matthew K Higgins
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Gordon A Awandare
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana. .,Department of Biochemistry, Cell and Molecular Biology, College of Basic and Applied Sciences, University of Ghana, P.O. Box LG54, Legon, Accra, Ghana.
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8
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Diédhiou CK, Moussa RA, Bei AK, Daniels R, Papa Mze N, Ndiaye D, Faye N, Wirth D, Amambua-Ngwa A, Mboup S, Ahouidi AD. Temporal changes in Plasmodium falciparum reticulocyte binding protein homolog 2b (PfRh2b) in Senegal and The Gambia. Malar J 2019; 18:239. [PMID: 31311552 PMCID: PMC6636118 DOI: 10.1186/s12936-019-2868-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 07/05/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The Plasmodium falciparum reticulocyte binding protein homolog 2b (PfRh2b) is an important P. falciparum merozoite ligand that mediates invasion of erythrocytes by interacting with a chymotrypsin-sensitive "receptor Z". A large deletion polymorphism is found in the c-terminal ectodomain of this protein in many countries around the world, resulting in a truncated, but expressed protein. The varying frequencies by region suggest that there could be region specific immune selection at this locus. Therefore, this study was designed to determine temporal changes in the PfRh2b deletion polymorphism in infected individuals from Thiès (Senegal) and Western Gambia (The Gambia). It was also sought to determine the selective pressures acting at this locus and whether prevalence of the deletion in isolates genotyped by a 24-SNP molecular barcode is linked to background genotype or whether there might be independent selection acting at this locus. METHODS Infected blood samples were sourced from archives of previous studies conducted between 2007 and 2013 at SLAP clinic in Thiès and from 1984 to 2013 in Western Gambia by MRC Unit at LSHTM, The Gambia. A total of 1380 samples were screened for the dimorphic alleles of the PfRh2b using semi-nested Polymerase Chain Reaction PCR. Samples from Thiès were previously barcoded. RESULTS In Thiès, a consistent trend of decreasing prevalence of the PfRh2b deletion over time was observed: from 66.54% in 2007 and to 38.1% in 2013. In contrast, in Western Gambia, the frequency of the deletion fluctuated over time; it increased between 1984 and 2005 from (58.04%) to (69.33%) and decreased to 47.47% in 2007. Between 2007 and 2012, the prevalence of this deletion increased significantly from 47.47 to 83.02% and finally declined significantly to 57.94% in 2013. Association between the presence of this deletion and age was found in Thiès, however, not in Western Gambia. For the majority of isolates, the PfRh2b alleles could be tracked with specific 24-SNP barcoded genotype, indicating a lack of independent selection at this locus. CONCLUSION PfRh2b deletion was found in the two countries with varying prevalence during the study period. However, these temporal and spatial variations could be an obstacle to the implementation of this protein as a potential vaccine candidate.
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Affiliation(s)
- Cyrille K Diédhiou
- Institute for Health Research, Epidemiological Surveillance and Training (IRESSEF), Dakar, Senegal.,Laboratory of Bacteriology and Virology, Hospital Aristide Le Dantec, 7325, Dakar, Senegal
| | - Rahama A Moussa
- Laboratory of Bacteriology and Virology, Hospital Aristide Le Dantec, 7325, Dakar, Senegal
| | - Amy K Bei
- Laboratory of Bacteriology and Virology, Hospital Aristide Le Dantec, 7325, Dakar, Senegal.,Department of Immunology & Infectious Diseases, Harvard TH Chan School of Public Health, 665 Huntington Avenue, Boston, MA, USA.,Laboratory of Parasitology Mycology, Aristide Le Dantec Hospital, Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, 5005, Dakar, Senegal
| | - Rachel Daniels
- Department of Immunology & Infectious Diseases, Harvard TH Chan School of Public Health, 665 Huntington Avenue, Boston, MA, USA
| | - Nasserdine Papa Mze
- Institute for Health Research, Epidemiological Surveillance and Training (IRESSEF), Dakar, Senegal.,Laboratory of Bacteriology and Virology, Hospital Aristide Le Dantec, 7325, Dakar, Senegal
| | - Daouda Ndiaye
- Laboratory of Parasitology Mycology, Aristide Le Dantec Hospital, Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, 5005, Dakar, Senegal
| | - Ngor Faye
- Faculty of Sciences and Technologies, University Cheikh Anta Diop, Dakar, PO Box 5005, Dakar, Senegal
| | - Dyann Wirth
- Department of Immunology & Infectious Diseases, Harvard TH Chan School of Public Health, 665 Huntington Avenue, Boston, MA, USA
| | - Alfred Amambua-Ngwa
- Medical Research Council Unit, The Gambia at LSHTM, Fajara, Banjul, The Gambia
| | - Souleymane Mboup
- Institute for Health Research, Epidemiological Surveillance and Training (IRESSEF), Dakar, Senegal
| | - Ambroise D Ahouidi
- Institute for Health Research, Epidemiological Surveillance and Training (IRESSEF), Dakar, Senegal. .,Laboratory of Bacteriology and Virology, Hospital Aristide Le Dantec, 7325, Dakar, Senegal.
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9
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Barua P, Beeson JG, Maleta K, Ashorn P, Rogerson SJ. The impact of early life exposure to Plasmodium falciparum on the development of naturally acquired immunity to malaria in young Malawian children. Malar J 2019; 18:11. [PMID: 30658632 PMCID: PMC6339377 DOI: 10.1186/s12936-019-2647-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Accepted: 01/12/2019] [Indexed: 11/23/2022] Open
Abstract
Background Antibodies targeting malaria blood-stage antigens are important targets of naturally acquired immunity, and may act as valuable biomarkers of malaria exposure. Methods Six-hundred and one young Malawian children from a randomized trial of prenatal nutrient supplementation with iron and folic acid or pre- and postnatal multiple micronutrients or lipid-based nutrient supplements were followed up weekly at home and febrile episodes were investigated for malaria from birth to 18 months of age. Antibodies were measured for 601 children against merozoite surface proteins (MSP1 19kD, MSP2), erythrocyte binding antigen 175 (EBA175), reticulocyte binding protein homologue 2 (Rh2A9), schizont extract and variant surface antigens expressed by Plasmodium falciparum-infected erythrocytes (IE) at 18 months of age. The antibody measurement data was related to concurrent malaria infection and to documented episodes of clinical malaria. Results At 18 months of age, antibodies were significantly higher among parasitaemic than aparasitaemic children. Antibody levels against MSP1 19kD, MSP2, schizont extract, and IE variant surface antigens were significantly higher in children who had documented episodes of malaria than in children who did not. Antibody levels did not differ between children with single or multiple malaria episodes before 18 months, nor between children who had malaria before 6 months of age or between 6 and 18 months. Conclusions Antibodies to merozoite and IE surface antigens increased following infection in early childhood, but neither age at first infection nor number of malaria episodes substantially affected antibody acquisition. These findings have implications for malaria surveillance during early childhood in the context of elimination. Trials registration Clinical Trials Registration: NCT01239693 (Date of registration: 11-10-2010). URL: http://www.ilins.org
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Affiliation(s)
- Priyanka Barua
- The Department of Medicine (RMH), Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, VIC, 3000, Australia.,Department of Zoology, University of Dhaka, Dhaka, 1000, Bangladesh
| | - James G Beeson
- The Department of Medicine (RMH), Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, VIC, 3000, Australia.,Burnet Institute, Melbourne, VIC, 3004, Australia.,Department of Microbiology and Central Clinical School, Monash University, Melbourne, VIC, 3800, Australia
| | - Kenneth Maleta
- School of Public Health and Family Medicine, University of Malawi, Blantyre 3, Malawi
| | - Per Ashorn
- Faculty of Medicine and Life Sciences, University of Tampere and Tampere University Hospital, 33100, Tampere, Finland.,Research and Development, Maternal, Newborn and Adolescent Health, World Health Organization, Geneva 27, 1211, Switzerland
| | - Stephen J Rogerson
- The Department of Medicine (RMH), Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, VIC, 3000, Australia.
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10
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Lim SSY, Chua KH, Nölke G, Spiegel H, Goh WL, Chow SC, Kee BP, Fischer R, Schillberg S, Othman RY. Plant-derived chimeric antibodies inhibit the invasion of human fibroblasts by Toxoplasma gondii. PeerJ 2018; 6:e5780. [PMID: 30581655 PMCID: PMC6294049 DOI: 10.7717/peerj.5780] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 09/17/2018] [Indexed: 11/25/2022] Open
Abstract
The parasite Toxoplasma gondii causes an opportunistic infection, that is, particularly severe in immunocompromised patients, infants, and neonates. Current antiparasitic drugs are teratogenic and cause hypersensitivity-based toxic side effects especially during prolonged treatment. Furthermore, the recent emergence of drug-resistant toxoplasmosis has reduced the therapeutic impact of such drugs. In an effort to develop recombinant antibodies as a therapeutic alternative, a panel of affinity-matured, T. gondii tachyzoite-specific single-chain variable fragment (scFv) antibodies was selected by phage display and bioinformatic analysis. Further affinity optimization was attempted by introducing point mutations at hotspots within light chain complementarity-determining region 2. This strategy yielded four mutated scFv sequences and a parental scFv that were used to produce five mouse-human chimeric IgGs in Nicotiana benthamiana plants, with yields of 33-72 mg/kg of plant tissue. Immunological analysis confirmed the specific binding of these plant-derived antibodies to T. gondii tachyzoites, and in vitro efficacy was demonstrated by their ability to inhibit the invasion of human fibroblasts and impair parasite infectivity. These novel recombinant antibodies could therefore be suitable for the development of plant-derived immunotherapeutic interventions against toxoplasmosis.
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Affiliation(s)
| | - Kek Heng Chua
- Department of Biomedical Science, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Greta Nölke
- Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Aachen, Germany
| | - Holger Spiegel
- Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Aachen, Germany
| | - Wai Leong Goh
- School of Science, Monash University Malaysia, Bandar Sunway, Selangor, Malaysia
| | - Sek Chuen Chow
- School of Science, Monash University Malaysia, Bandar Sunway, Selangor, Malaysia
| | - Boon Pin Kee
- Department of Biomedical Science, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Rainer Fischer
- Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Aachen, Germany
| | - Stefan Schillberg
- Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Aachen, Germany
| | - Rofina Yasmin Othman
- Institute of Biological Sciences, University of Malaya, Kuala Lumpur, Malaysia
- Centre for Research in Biotechnology for Agriculture, University of Malaya, Kuala Lumpur, Malaysia
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11
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Campino S, Marin-Menendez A, Kemp A, Cross N, Drought L, Otto TD, Benavente ED, Ravenhall M, Schwach F, Girling G, Manske M, Theron M, Gould K, Drury E, Clark TG, Kwiatkowski DP, Pance A, Rayner JC. A forward genetic screen reveals a primary role for Plasmodium falciparum Reticulocyte Binding Protein Homologue 2a and 2b in determining alternative erythrocyte invasion pathways. PLoS Pathog 2018; 14:e1007436. [PMID: 30496294 PMCID: PMC6289454 DOI: 10.1371/journal.ppat.1007436] [Citation(s) in RCA: 12] [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: 07/31/2018] [Revised: 12/11/2018] [Accepted: 10/24/2018] [Indexed: 12/14/2022] Open
Abstract
Invasion of human erythrocytes is essential for Plasmodium falciparum parasite survival and pathogenesis, and is also a complex phenotype. While some later steps in invasion appear to be invariant and essential, the earlier steps of recognition are controlled by a series of redundant, and only partially understood, receptor-ligand interactions. Reverse genetic analysis of laboratory adapted strains has identified multiple genes that when deleted can alter invasion, but how the relative contributions of each gene translate to the phenotypes of clinical isolates is far from clear. We used a forward genetic approach to identify genes responsible for variable erythrocyte invasion by phenotyping the parents and progeny of previously generated experimental genetic crosses. Linkage analysis using whole genome sequencing data revealed a single major locus was responsible for the majority of phenotypic variation in two invasion pathways. This locus contained the PfRh2a and PfRh2b genes, members of one of the major invasion ligand gene families, but not widely thought to play such a prominent role in specifying invasion phenotypes. Variation in invasion pathways was linked to significant differences in PfRh2a and PfRh2b expression between parasite lines, and their role in specifying alternative invasion was confirmed by CRISPR-Cas9-mediated genome editing. Expansion of the analysis to a large set of clinical P. falciparum isolates revealed common deletions, suggesting that variation at this locus is a major cause of invasion phenotypic variation in the endemic setting. This work has implications for blood-stage vaccine development and will help inform the design and location of future large-scale studies of invasion in clinical isolates. Plasmodium parasites cause more than 200 million cases of malaria each year. All the symptoms of malaria are caused after Plasmodium parasites invade human red blood cells. Once inside, they grow, multiply and break open the red blood cells to release new parasites. This cycle is repeated every 48 hours, rapidly amplifying the number of parasites and causing severe anemia and other complications. Plasmodium falciparum, the parasite species responsible for almost all malaria deaths, can use multiple different pathways to invade human red blood cells, but the relative importance of each is not well understood. We tested the invasion pathways used by a collection of closely related parasites and compared their genome sequences to identify the genes responsible. This analysis revealed that expression differences in two neighboring genes of the Reticulocyte Binding Homologue family are responsible for most of the variation in two invasion pathways. P. falciparum may use variation in these genes to avoid the immune system or adapt to specific blood groups, which has important implications for vaccine development against malaria.
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Affiliation(s)
- Susana Campino
- Malaria Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
- * E-mail: (SC); (JCR)
| | - Alejandro Marin-Menendez
- Malaria Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Alison Kemp
- Malaria Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Nadia Cross
- Malaria Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Laura Drought
- Malaria Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Thomas D. Otto
- Malaria Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
- Centre of Immunobiology, Institute of Infection, Immunity & Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Ernest Diez Benavente
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Matt Ravenhall
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Frank Schwach
- Malaria Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Gareth Girling
- Malaria Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Magnus Manske
- Malaria Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Michel Theron
- Malaria Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Kelda Gould
- Malaria Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Eleanor Drury
- Malaria Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Taane G. Clark
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
- Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Dominic P. Kwiatkowski
- Malaria Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Alena Pance
- Malaria Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Julian C. Rayner
- Malaria Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
- * E-mail: (SC); (JCR)
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12
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Bei AK, Ahouidi AD, Dvorin JD, Miura K, Diouf A, Ndiaye D, Premji Z, Diakite M, Mboup S, Long CA, Duraisingh MT. Functional Analysis Reveals Geographical Variation in Inhibitory Immune Responses Against a Polymorphic Malaria Antigen. J Infect Dis 2017; 216:267-275. [PMID: 28605544 PMCID: PMC5853457 DOI: 10.1093/infdis/jix280] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2017] [Accepted: 06/08/2017] [Indexed: 12/28/2022] Open
Abstract
Background Plasmodium falciparum reticulocyte-binding protein homologue 2b (PfRh2b) is an invasion ligand that is a potential blood-stage vaccine candidate antigen; however, a naturally occurring deletion within an immunogenic domain is present at high frequencies in Africa and has been associated with alternative invasion pathway usage. Standardized tools that provide antigenic specificity in in vitro assays are needed to functionally assess the neutralizing potential of humoral responses against malaria vaccine candidate antigens. Methods Transgenic parasite lines were generated to express the PfRh2b deletion. Total immunoglobulin G (IgG) from individuals residing in malaria-endemic regions in Tanzania, Senegal, and Mali were used in growth inhibition assays with transgenic parasite lines. Results While the PfRh2b deletion transgenic line showed no change in invasion pathway utilization compared to the wild-type in the absence of specific antibodies, it outgrew wild-type controls in competitive growth experiments. Inhibition differences with total IgG were observed in the different endemic sites, ranging from allele-specific inhibition to allele-independent inhibitory immune responses. Conclusions The PfRh2b deletion may allow the parasite to escape neutralizing antibody responses in some regions. This difference in geographical inhibition was revealed using transgenic methodologies, which provide valuable tools for functionally assessing neutralizing antibodies against vaccine-candidate antigens in regions with varying malaria endemicity.
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Affiliation(s)
- Amy K Bei
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
- Laboratory of Bacteriology and Virology, Le Dantec Hospital, Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, Dakar, Senegal
- Laboratory of Parasitology and Mycology, Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, Dakar, Senegal
| | - Ambroise D Ahouidi
- Laboratory of Bacteriology and Virology, Le Dantec Hospital, Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, Dakar, Senegal
| | - Jeffrey D Dvorin
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
- Division of Infectious Diseases, Boston Children's Hospital and Harvard Medical School, Massachusetts
| | - Kazutoyo Miura
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
| | - Ababacar Diouf
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
| | - Daouda Ndiaye
- Laboratory of Parasitology and Mycology, Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, Dakar, Senegal
| | - Zul Premji
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar-es-Salaam, Tanzania
- Department of Pathology, Aga Khan University Hospital, Nairobi, Kenya
| | - Mahamadou Diakite
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odontostomatology, University of Science, Techniques and Technologies of Bamako, Mali
| | - Souleymane Mboup
- Laboratory of Bacteriology and Virology, Le Dantec Hospital, Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, Dakar, Senegal
- Institut de Recherche en Santé, de Surveillance Epidemiologique et de Formations, Dakar, Senegal
| | - Carole A Long
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
| | - Manoj T Duraisingh
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
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13
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Plasmodium falciparum erythrocyte-binding antigen 175 triggers a biophysical change in the red blood cell that facilitates invasion. Proc Natl Acad Sci U S A 2017; 114:4225-4230. [PMID: 28373555 DOI: 10.1073/pnas.1620843114] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Invasion of the red blood cell (RBC) by the Plasmodium parasite defines the start of malaria disease pathogenesis. To date, experimental investigations into invasion have focused predominantly on the role of parasite adhesins or signaling pathways and the identity of binding receptors on the red cell surface. A potential role for signaling pathways within the erythrocyte, which might alter red cell biophysical properties to facilitate invasion, has largely been ignored. The parasite erythrocyte-binding antigen 175 (EBA175), a protein required for entry in most parasite strains, plays a key role by binding to glycophorin A (GPA) on the red cell surface, although the function of this binding interaction is unknown. Here, using real-time deformability cytometry and flicker spectroscopy to define biophysical properties of the erythrocyte, we show that EBA175 binding to GPA leads to an increase in the cytoskeletal tension of the red cell and a reduction in the bending modulus of the cell's membrane. We isolate the changes in the cytoskeleton and membrane and show that reduction in the bending modulus is directly correlated with parasite invasion efficiency. These data strongly imply that the malaria parasite primes the erythrocyte surface through its binding antigens, altering the biophysical nature of the target cell and thus reducing a critical energy barrier to invasion. This finding would constitute a major change in our concept of malaria parasite invasion, suggesting it is, in fact, a balance between parasite and host cell physical forces working together to facilitate entry.
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14
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The association between naturally acquired IgG subclass specific antibodies to the PfRH5 invasion complex and protection from Plasmodium falciparum malaria. Sci Rep 2016; 6:33094. [PMID: 27604417 PMCID: PMC5015043 DOI: 10.1038/srep33094] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 08/19/2016] [Indexed: 11/13/2022] Open
Abstract
Understanding the targets and mechanisms of human immunity to malaria is important for advancing the development of highly efficacious vaccines and serological tools for malaria surveillance. The PfRH5 and PfRipr proteins form a complex on the surface of P. falciparum merozoites that is essential for invasion of erythrocytes and are vaccine candidates. We determined IgG subclass responses to these proteins among malaria-exposed individuals in Papua New Guinea and their association with protection from malaria in a longitudinal cohort of children. Cytophilic subclasses, IgG1 and IgG3, were predominant with limited IgG2 and IgG4, and IgG subclass-specific responses were higher in older children and those with active infection. High IgG3 to PfRH5 and PfRipr were significantly and strongly associated with reduced risk of malaria after adjusting for potential confounding factors, whereas associations for IgG1 responses were generally weaker and not statistically significant. Results further indicated that malaria exposure leads to the co-acquisition of IgG1 and IgG3 to PfRH5 and PfRipr, as well as to other PfRH invasion ligands, PfRH2 and PfRH4. These findings suggest that IgG3 responses to PfRH5 and PfRipr may play a significant role in mediating naturally-acquired immunity and support their potential as vaccine candidates and their use as antibody biomarkers of immunity.
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15
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Aniweh Y, Gao X, Gunalan K, Preiser PR. PfRH2b specific monoclonal antibodies inhibit merozoite invasion. Mol Microbiol 2016; 102:386-404. [DOI: 10.1111/mmi.13468] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/18/2016] [Indexed: 11/28/2022]
Affiliation(s)
- Yaw Aniweh
- Division of Molecular Genetics and Cell biology, School of Biological Sciences; Nanyang Technological University; 637551 Singapore
| | - Xiaohong Gao
- Division of Molecular Genetics and Cell biology, School of Biological Sciences; Nanyang Technological University; 637551 Singapore
| | - Karthigayan Gunalan
- Division of Molecular Genetics and Cell biology, School of Biological Sciences; Nanyang Technological University; 637551 Singapore
| | - Peter R. Preiser
- Division of Molecular Genetics and Cell biology, School of Biological Sciences; Nanyang Technological University; 637551 Singapore
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16
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Beeson JG, Drew DR, Boyle MJ, Feng G, Fowkes FJI, Richards JS. Merozoite surface proteins in red blood cell invasion, immunity and vaccines against malaria. FEMS Microbiol Rev 2016; 40:343-72. [PMID: 26833236 PMCID: PMC4852283 DOI: 10.1093/femsre/fuw001] [Citation(s) in RCA: 228] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/03/2016] [Indexed: 01/11/2023] Open
Abstract
Malaria accounts for an enormous burden of disease globally, with Plasmodium falciparum accounting for the majority of malaria, and P. vivax being a second important cause, especially in Asia, the Americas and the Pacific. During infection with Plasmodium spp., the merozoite form of the parasite invades red blood cells and replicates inside them. It is during the blood-stage of infection that malaria disease occurs and, therefore, understanding merozoite invasion, host immune responses to merozoite surface antigens, and targeting merozoite surface proteins and invasion ligands by novel vaccines and therapeutics have been important areas of research. Merozoite invasion involves multiple interactions and events, and substantial processing of merozoite surface proteins occurs before, during and after invasion. The merozoite surface is highly complex, presenting a multitude of antigens to the immune system. This complexity has proved challenging to our efforts to understand merozoite invasion and malaria immunity, and to developing merozoite antigens as malaria vaccines. In recent years, there has been major progress in this field, and several merozoite surface proteins show strong potential as malaria vaccines. Our current knowledge on this topic is reviewed, highlighting recent advances and research priorities. The authors summarize current knowledge of merozoite surface proteins of malaria parasites; their function in invasion, processing of surface proteins before, during and after invasion, their importance as targets of immunity, and the current status of malaria vaccines that target merozoite surface proteins.
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Affiliation(s)
- James G Beeson
- Burnet Institute for Medical Research and Public Health, 85 Commercial Road, Melbourne, Victoria, Australia Department of Microbiology, Monash University, Clayton, Victoria, Australia Department of Medicine, University of Melbourne, Parkville, Victoria, Australia
| | - Damien R Drew
- Burnet Institute for Medical Research and Public Health, 85 Commercial Road, Melbourne, Victoria, Australia
| | - Michelle J Boyle
- Burnet Institute for Medical Research and Public Health, 85 Commercial Road, Melbourne, Victoria, Australia
| | - Gaoqian Feng
- Burnet Institute for Medical Research and Public Health, 85 Commercial Road, Melbourne, Victoria, Australia
| | - Freya J I Fowkes
- Burnet Institute for Medical Research and Public Health, 85 Commercial Road, Melbourne, Victoria, Australia Department of Epidemiology and Preventive Medicine, Monash University, Clayton, Victoria, Australia School of Population Health, University of Melbourne, Parkville, Victoria, Australia
| | - Jack S Richards
- Burnet Institute for Medical Research and Public Health, 85 Commercial Road, Melbourne, Victoria, Australia Department of Microbiology, Monash University, Clayton, Victoria, Australia Department of Medicine, University of Melbourne, Parkville, Victoria, Australia
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17
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Triggers of key calcium signals during erythrocyte invasion by Plasmodium falciparum. Nat Commun 2014; 4:2862. [PMID: 24280897 PMCID: PMC3868333 DOI: 10.1038/ncomms3862] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Accepted: 11/04/2013] [Indexed: 01/28/2023] Open
Abstract
Invasion of erythrocytes by Plasmodium falciparum merozoites is a complex multi-step process mediated by specific interactions between host receptors and parasite ligands. Reticulocyte-binding protein homologues (RHs) and erythrocyte-binding-like (EBL) proteins are discharged from specialized organelles and used in early steps of invasion. Here we show that monoclonal antibodies against PfRH1 (an RH) block merozoite invasion by specifically inhibiting calcium signalling in the parasite, whereas invasion-inhibiting monoclonal antibodies targeting EBA175 (an EBL protein) have no effect on signalling. We further show that inhibition of this calcium signalling prevents EBA175 discharge and thereby formation of the junction between parasite and host cell. Our results indicate that PfRH1 has an initial sensing as well as signal transduction role that leads to the subsequent release of EBA175. They also provide new insights on how RH-host cell interactions lead to essential downstream signalling events in the parasite, suggesting new targets for malaria intervention.
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18
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Sennang N, Rogerson S, Wahyuni S, Yusuf I, Syafruddin D. Antibody response against three Plasmodium falciparum merozoite antigens in Mamuju District, West Sulawesi Province, Indonesia. Malar J 2014; 13:381. [PMID: 25255775 PMCID: PMC4193137 DOI: 10.1186/1475-2875-13-381] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Accepted: 09/18/2014] [Indexed: 11/18/2022] Open
Abstract
Background Malaria endemicity in the archipelago of Indonesia varies substantially across regions. Following the government’s plan for a malaria elimination programme in Indonesia, baseline malaria surveys were conducted in Mamuju District, West Sulawesi Province, Indonesia to re-assess the malaria situation prior to the establishment of an evidence-based malaria elimination programme in the area. The present study aims to determine the antibody response to three merozoite antigens among the inhabitants of the district. Methods Antibodies were measured following elution from filter-paper blood spots collected during cross-sectional surveys in the dry and wet season in 2010. Enzyme-linked immunosorbent assays using three merozoite antigens, MSP2, EBA175 and PfRh2a were conducted. A positivity threshold was determined by samples from unexposed individuals and the difference in antibody level against each antigen and correlation of antibody level in different age groups and seasons were statistically analysed. Results A total of 497 subjects, 248 in dry and 249 in wet season, aged between 0.6 and 78 years were included. The prevalence of positive antibody responses to MSP2, EBA175 and PfRh2a antigens in dry season were 27.82, 27.42 and 25.81%, respectively. In wet season, the antibody prevalences were 64.26, 64.66 and 61.45%. The antibody levels to the three antigens were all higher in older age groups and also significantly higher in the wet season. The antibody levels also correlated positively with the Plasmodium falciparum infection status of the subjects. Conclusion MSP2, EBA175 and PfRh2a induce antibody responses among the subjects in Mamuju District, and the prevalence is significantly higher in wet season. The level of antibody also correlates significantly with age and malaria positivity. The overall results indicate the antigens might be used as a target for vaccines against P. falciparum infection and as markers for malaria exposure.
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Affiliation(s)
| | | | | | | | - Din Syafruddin
- Department of Parasitology, Faculty of Medicine, Hasanuddin University, Makassar 90245, South Sulawesi, Indonesia.
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19
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Bacterially expressed full-length recombinant Plasmodium falciparum RH5 protein binds erythrocytes and elicits potent strain-transcending parasite-neutralizing antibodies. Infect Immun 2013; 82:152-64. [PMID: 24126527 DOI: 10.1128/iai.00970-13] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Plasmodium falciparum reticulocyte binding-like homologous protein 5 (PfRH5) is an essential merozoite ligand that binds with its erythrocyte receptor, basigin. PfRH5 is an attractive malaria vaccine candidate, as it is expressed by a wide number of P. falciparum strains, cannot be genetically disrupted, and exhibits limited sequence polymorphisms. Viral vector-induced PfRH5 antibodies potently inhibited erythrocyte invasion. However, it has been a challenge to generate full-length recombinant PfRH5 in a bacterial-cell-based expression system. In this study, we have produced full-length recombinant PfRH5 in Escherichia coli that exhibits specific erythrocyte binding similar to that of the native PfRH5 parasite protein and also, importantly, elicits potent invasion-inhibitory antibodies against a number of P. falciparum strains. Antibasigin antibodies blocked the erythrocyte binding of both native and recombinant PfRH5, further confirming that they bind with basigin. We have thus successfully produced full-length PfRH5 as a functionally active erythrocyte binding recombinant protein with a conformational integrity that mimics that of the native parasite protein and elicits potent strain-transcending parasite-neutralizing antibodies. P. falciparum has the capability to develop immune escape mechanisms, and thus, blood-stage malaria vaccines that target multiple antigens or pathways may prove to be highly efficacious. In this regard, antibody combinations targeting PfRH5 and other key merozoite antigens produced potent additive inhibition against multiple worldwide P. falciparum strains. PfRH5 was immunogenic when immunized with other antigens, eliciting potent invasion-inhibitory antibody responses with no immune interference. Our results strongly support the development of PfRH5 as a component of a combination blood-stage malaria vaccine.
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Hans N, Singh S, Pandey AK, Reddy KS, Gaur D, Chauhan VS. Identification and characterization of a novel Plasmodium falciparum adhesin involved in erythrocyte invasion. PLoS One 2013; 8:e74790. [PMID: 24058628 PMCID: PMC3772933 DOI: 10.1371/journal.pone.0074790] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 08/05/2013] [Indexed: 11/18/2022] Open
Abstract
Malaria remains a major health problem worldwide. All clinical symptoms of malaria are attributed to the asexual blood stages of the parasite life cycle. Proteins resident in apical organelles and present on the surface of P. falciparum merozoites are considered promising candidates for the development of blood stage malaria vaccines. In the present study, we have identified and characterized a microneme associated antigen, PfMA [PlasmoDB Gene ID: PF3D7_0316000, PFC0700c]. The gene was selected by applying a set of screening criteria such as transcriptional upregulation at late schizogony, inter-species conservation and the presence of signal sequence or transmembrane domains. The gene sequence of PfMA was found to be conserved amongst various Plasmodium species. We experimentally demonstrated that the transcript for PfMA was expressed only in the late blood stages of parasite consistent with a putative role in erythrocyte invasion. PfMA was localized by immunofluorescence and immuno-electron microscopy to be in the micronemes, an apical organelle of merozoites. The functional role of the PfMA protein in erythrocyte invasion was identified as a parasite adhesin involved in direct attachment with the target erythrocyte. PfMA was demonstrated to bind erythrocytes in a sialic acid independent, chymotrypsin and trypsin resistant manner and its antibodies inhibited P. falciparum erythrocyte invasion. Invasion of erythrocytes is a complex multistep process that involves a number of redundant ligand-receptor interactions many of which still remain unknown and even uncharacterized. Our work has identified and characterized a novel P. falciparum adhesin involved in erythrocyte invasion.
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Affiliation(s)
- Nidhi Hans
- Malaria Research Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India
| | - Shailja Singh
- Malaria Research Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India
| | - Alok K. Pandey
- Malaria Research Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India
| | - K. Sony Reddy
- Malaria Research Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India
| | - Deepak Gaur
- Malaria Research Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India
| | - Virander S. Chauhan
- Malaria Research Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India
- * E-mail:
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Healer J, Thompson JK, Riglar DT, Wilson DW, Chiu YH, Miura K, Chen L, Hodder AN, Long CA, Hansen DS, Baum J, Cowman AF. Vaccination with conserved regions of erythrocyte-binding antigens induces neutralizing antibodies against multiple strains of Plasmodium falciparum. PLoS One 2013; 8:e72504. [PMID: 24039774 PMCID: PMC3769340 DOI: 10.1371/journal.pone.0072504] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 07/10/2013] [Indexed: 02/07/2023] Open
Abstract
Background A highly effective vaccine against Plasmodium falciparum malaria should induce potent, strain transcending immunity that broadly protects against the diverse population of parasites circulating globally. We aimed to identify vaccine candidates that fulfill the criteria. Methods We have measured growth inhibitory activity of antibodies raised to a range of antigens to identify those that can efficiently block merozoite invasion for geographically diverse strains of P. falciparum. Results This has shown that the conserved Region III-V, of the P. falciparum erythrocyte-binding antigen (EBA)-175 was able to induce antibodies that potently inhibit merozoite invasion across diverse parasite strains, including those reliant on invasion pathways independent of EBA-175 function. Additionally, the conserved RIII-V domain of EBA-140 also induced antibodies with strong in vitro parasite growth inhibitory activity. Conclusion We identify an alternative, highly conserved region (RIV-V) of EBA-175, present in all EBA proteins, that is the target of potent, strain transcending neutralizing antibodies, that represents a strong candidate for development as a component in a malaria vaccine.
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Affiliation(s)
- Julie Healer
- Walter & Eliza Hall Institute for Medical Research, Melbourne, Australia
| | | | - David T. Riglar
- Walter & Eliza Hall Institute for Medical Research, Melbourne, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Danny W. Wilson
- Walter & Eliza Hall Institute for Medical Research, Melbourne, Australia
| | - Yu-H.C. Chiu
- Walter & Eliza Hall Institute for Medical Research, Melbourne, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Kazutoyo Miura
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Disease, National Institutes of Health, Rockville, Maryland, United States of America
| | - Lin Chen
- Walter & Eliza Hall Institute for Medical Research, Melbourne, Australia
| | - Anthony N. Hodder
- Walter & Eliza Hall Institute for Medical Research, Melbourne, Australia
| | - Carole A. Long
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Disease, National Institutes of Health, Rockville, Maryland, United States of America
| | - Diana S. Hansen
- Walter & Eliza Hall Institute for Medical Research, Melbourne, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Jake Baum
- Walter & Eliza Hall Institute for Medical Research, Melbourne, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Alan F. Cowman
- Walter & Eliza Hall Institute for Medical Research, Melbourne, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
- * E-mail:
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Abstract
Red blood cell invasion by the malaria parasite Plasmodium falciparum relies on a complex protein network that uses low and high affinity receptor–ligand interactions. Signal transduction through the action of specific kinases is a control mechanism for the orchestration of this process. In the present study we report on the phosphorylation of the CPD (cytoplasmic domain) of P. falciparum Rh2b (reticulocyte homologue protein 2b). First, we identified Ser3233 as the sole phospho-acceptor site in the CPD for in vitro phosphorylation by parasite extract. We provide several lines of evidence that this phosphorylation is mediated by PfCK2 (P. falciparum casein kinase 2): phosphorylation is cAMP independent, utilizes ATP as well as GTP as phosphate donors, is inhibited by heparin and tetrabromocinnamic acid, and is mediated by purified PfCK2. We raised a phospho-specific antibody and showed that Ser3233 phosphorylation occurs in the parasite prior to host cell egress. We analysed the spatiotemporal aspects of this phosphorylation using immunoprecipitated endogenous Rh2b and minigenes expressing the CPD either at the plasma or rhoptry membrane. Phosphorylation of Rh2b is not spatially restricted to either the plasma or rhoptry membrane and most probably occurs before Rh2b is translocated from the rhoptry neck to the plasma membrane.
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Persson KEM, Fowkes FJI, McCallum FJ, Gicheru N, Reiling L, Richards JS, Wilson DW, Lopaticki S, Cowman AF, Marsh K, Beeson JG. Erythrocyte-binding antigens of Plasmodium falciparum are targets of human inhibitory antibodies and function to evade naturally acquired immunity. THE JOURNAL OF IMMUNOLOGY 2013; 191:785-94. [PMID: 23776178 DOI: 10.4049/jimmunol.1300444] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Abs that inhibit Plasmodium falciparum invasion of erythrocytes form an important component of human immunity against malaria, but key target Ags are largely unknown. Phenotypic variation by P. falciparum mediates the evasion of inhibitory Abs, contributing to the capacity of P. falciparum to cause repeat and chronic infections. However, Ags involved in mediating immune evasion have not been defined, and studies of the function of human Abs are limited. In this study, we used novel approaches to determine the importance of P. falciparum erythrocyte-binding Ags (EBAs), which are important invasion ligands, as targets of human invasion-inhibitory Abs and define their role in contributing to immune evasion through variation in function. We evaluated the invasion-inhibitory activity of acquired Abs from malaria-exposed children and adults from Kenya, using P. falciparum with disruption of genes encoding EBA140, EBA175, and EBA181, either individually or combined as EBA140/EBA175 or EBA175/EBA181 double knockouts. Our findings provide important new evidence that variation in the expression and function of the EBAs plays an important role in evasion of acquired Abs and that a substantial amount of phenotypic diversity results from variation in expression of different EBAs that contributes to immune evasion by P. falciparum. All three EBAs were identified as important targets of naturally acquired inhibitory Abs demonstrated by differential inhibition of parental parasites greater than EBA knockout lines. This knowledge will help to advance malaria vaccine development and suggests that multiple invasion ligands need to be targeted to overcome the capacity of P. falciparum for immune evasion.
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Affiliation(s)
- Kristina E M Persson
- Karolinska Institutet, Microbiology, Tumor and Cell Biology, 17177 Stockholm, Sweden.
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Moreno-Pérez DA, Ruíz JA, Patarroyo MA. Reticulocytes: Plasmodium vivax target cells. Biol Cell 2013; 105:251-60. [PMID: 23458497 DOI: 10.1111/boc.201200093] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 02/22/2013] [Indexed: 02/05/2023]
Abstract
Reticulocytes represent the main invasion target for Plasmodium vivax, the second most prevalent parasite species around the world causing malaria in humans. In spite of these cells' importance in research into malaria, biological knowledge related to the nature of the host has been limited, given the technical difficulties present in working with them in the laboratory. Poor reticulocyte recovery from total blood, by different techniques, has hampered continuous in vitro P. vivax cultures being developed, thereby delaying basic investigation in this parasite species. Intense research during the last few years has led to advances being made in developing methodologies orientated towards obtaining enriched reticulocytes from differing sources, thereby providing invaluable information for developing new strategies aimed at preventing infection caused by malaria. This review describes the most recent studies related to obtaining reticulocytes and discusses approaches which could contribute towards knowledge regarding molecular interactions between target cell proteins and their main infective agent, P. vivax.
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25
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Yu FD, Yang SY, Li YY, Hu W. Co-expression network with protein–protein interaction and transcription regulation in malaria parasite Plasmodium falciparum. Gene 2013; 518:7-16. [DOI: 10.1016/j.gene.2012.11.092] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Accepted: 11/27/2012] [Indexed: 12/16/2022]
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26
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Mueller I, Galinski MR, Tsuboi T, Arevalo-Herrera M, Collins WE, King CL. Natural acquisition of immunity to Plasmodium vivax: epidemiological observations and potential targets. ADVANCES IN PARASITOLOGY 2013; 81:77-131. [PMID: 23384622 DOI: 10.1016/b978-0-12-407826-0.00003-5] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Population studies show that individuals acquire immunity to Plasmodium vivax more quickly than Plasmodium falciparum irrespective of overall transmission intensity, resulting in the peak burden of P. vivax malaria in younger age groups. Similarly, actively induced P. vivax infections in malaria therapy patients resulted in faster and generally more strain-transcending acquisition of immunity than P. falciparum infections. The mechanisms behind the more rapid acquisition of immunity to P. vivax are poorly understood. Natural acquired immune responses to P. vivax target both pre-erythrocytic and blood-stage antigens and include humoral and cellular components. To date, only a few studies have investigated the association of these immune responses with protection, with most studies focussing on a few merozoite antigens (such as the Pv Duffy binding protein (PvDBP), the Pv reticulocyte binding proteins (PvRBPs), or the Pv merozoite surface proteins (PvMSP1, 3 & 9)) or the circumsporozoite protein (PvCSP). Naturally acquired transmission-blocking (TB) immunity (TBI) was also found in several populations. Although limited, these data support the premise that developing a multi-stage P. vivax vaccine may be feasible and is worth pursuing.
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Affiliation(s)
- Ivo Mueller
- Walter + Eliza Hall Institute, Infection & Immunity Division, Parkville, Victoria, Australia
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27
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Boyle MJ, Wilson DW, Beeson JG. New approaches to studying Plasmodium falciparum merozoite invasion and insights into invasion biology. Int J Parasitol 2012; 43:1-10. [PMID: 23220090 DOI: 10.1016/j.ijpara.2012.11.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Revised: 10/30/2012] [Accepted: 11/03/2012] [Indexed: 10/27/2022]
Abstract
Merozoite invasion of human red blood cells by Plasmodium falciparum is essential for blood stage asexual replication and the development of malaria disease. Despite this, many of the processes involved in invasion are poorly understood. Recent advances have been made in methods to isolate viable merozoites for studies of invasion. The application of these approaches is providing new insights into the kinetics of invasion and merozoite survival, as well as proteins and interactions involved in invasion, and will facilitate the development and testing of anti-merozoite vaccines and the identification of invasion-inhibitory compounds with potential for drug development. This review discusses these recent advances and considers potential avenues for future research.
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Affiliation(s)
- Michelle J Boyle
- The Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, Australia
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28
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Deponte M, Hoppe HC, Lee MC, Maier AG, Richard D, Rug M, Spielmann T, Przyborski JM. Wherever I may roam: Protein and membrane trafficking in P. falciparum-infected red blood cells. Mol Biochem Parasitol 2012; 186:95-116. [DOI: 10.1016/j.molbiopara.2012.09.007] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Revised: 09/21/2012] [Accepted: 09/24/2012] [Indexed: 11/27/2022]
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Gunalan K, Gao X, Yap SSL, Huang X, Preiser PR. The role of the reticulocyte-binding-like protein homologues of Plasmodium in erythrocyte sensing and invasion. Cell Microbiol 2012; 15:35-44. [PMID: 23046317 DOI: 10.1111/cmi.12038] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 09/17/2012] [Accepted: 10/01/2012] [Indexed: 11/27/2022]
Abstract
Malaria remains a serious public health problem with significant morbidity and mortality accounting for nearly 20% of all childhood deaths in Africa. The cyclical invasion, cytoadherence and destruction of the host's erythrocyte by the parasite are responsible for the observed disease pathology. The invasive form of the parasite, the merozoite, uses a complex set of interactions between parasite ligands and erythrocyte receptors that leads to the formation of a tight junction and ultimately successful erythrocyte invasion. Understanding the molecular mechanism underlying host cell recognition and invasion is crucial for the development of a targeted intervention strategy. Two parasite protein families termed reticulocyte-binding-like protein homologues (RBL) and the erythrocyte-binding-like (EBL) protein family are conserved in all Plasmodium species and have been shown to play an important role in host cell recognition and invasion. Over the last few years significant new insights have been gained in understanding the function of the RBL family and this review attempts to provide an update with a specific focus on the role of RBL in signal transduction pathways during invasion.
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Affiliation(s)
- Karthigayan Gunalan
- Division of Molecular Genetics & Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
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30
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Zuccala ES, Gout AM, Dekiwadia C, Marapana DS, Angrisano F, Turnbull L, Riglar DT, Rogers KL, Whitchurch CB, Ralph SA, Speed TP, Baum J. Subcompartmentalisation of proteins in the rhoptries correlates with ordered events of erythrocyte invasion by the blood stage malaria parasite. PLoS One 2012; 7:e46160. [PMID: 23049965 PMCID: PMC3458004 DOI: 10.1371/journal.pone.0046160] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2012] [Accepted: 08/27/2012] [Indexed: 11/18/2022] Open
Abstract
Host cell infection by apicomplexan parasites plays an essential role in lifecycle progression for these obligate intracellular pathogens. For most species, including the etiological agents of malaria and toxoplasmosis, infection requires active host-cell invasion dependent on formation of a tight junction – the organising interface between parasite and host cell during entry. Formation of this structure is not, however, shared across all Apicomplexa or indeed all parasite lifecycle stages. Here, using an in silico integrative genomic search and endogenous gene-tagging strategy, we sought to characterise proteins that function specifically during junction-dependent invasion, a class of proteins we term invasins to distinguish them from adhesins that function in species specific host-cell recognition. High-definition imaging of tagged Plasmodium falciparum invasins localised proteins to multiple cellular compartments of the blood stage merozoite. This includes several that localise to distinct subcompartments within the rhoptries. While originating from the same organelle, however, each has very different dynamics during invasion. Apical Sushi Protein and Rhoptry Neck protein 2 release early, following the junction, whilst a novel rhoptry protein PFF0645c releases only after invasion is complete. This supports the idea that organisation of proteins within a secretory organelle determines the order and destination of protein secretion and provides a localisation-based classification strategy for predicting invasin function during apicomplexan parasite invasion.
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Affiliation(s)
- Elizabeth S. Zuccala
- Infection and Immunity, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Alexander M. Gout
- Bioinformatics Divisions, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Chaitali Dekiwadia
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Danushka S. Marapana
- Infection and Immunity, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Fiona Angrisano
- Infection and Immunity, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Lynne Turnbull
- The ithree Institute, University of Technology Sydney, Sydney, New South Wales, Australia
| | - David T. Riglar
- Infection and Immunity, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Kelly L. Rogers
- Imaging Facility, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Cynthia B. Whitchurch
- The ithree Institute, University of Technology Sydney, Sydney, New South Wales, Australia
| | - Stuart A. Ralph
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Terence P. Speed
- Bioinformatics Divisions, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Jake Baum
- Infection and Immunity, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
- * E-mail:
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The Plasmodium falciparum erythrocyte invasion ligand Pfrh4 as a target of functional and protective human antibodies against malaria. PLoS One 2012; 7:e45253. [PMID: 23028883 PMCID: PMC3447948 DOI: 10.1371/journal.pone.0045253] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Accepted: 08/17/2012] [Indexed: 11/19/2022] Open
Abstract
Background Acquired antibodies are important in human immunity to malaria, but key targets remain largely unknown. Plasmodium falciparum reticulocyte-binding-homologue-4 (PfRh4) is important for invasion of human erythrocytes and may therefore be a target of protective immunity. Methods IgG and IgG subclass-specific responses against different regions of PfRh4 were determined in a longitudinal cohort of 206 children in Papua New Guinea (PNG). Human PfRh4 antibodies were tested for functional invasion-inhibitory activity, and expression of PfRh4 by P. falciparum isolates and sequence polymorphisms were determined. Results Antibodies to PfRh4 were acquired by children exposed to P. falciparum malaria, were predominantly comprised of IgG1 and IgG3 subclasses, and were associated with increasing age and active parasitemia. High levels of antibodies, particularly IgG3, were strongly predictive of protection against clinical malaria and high-density parasitemia. Human affinity-purified antibodies to the binding region of PfRh4 effectively inhibited erythrocyte invasion by P. falciparum merozoites and antibody levels in protected children were at functionally-active concentrations. Although expression of PfRh4 can vary, PfRh4 protein was expressed by most isolates derived from the cohort and showed limited sequence polymorphism. Conclusions Evidence suggests that PfRh4 is a target of antibodies that contribute to protective immunity to malaria by inhibiting erythrocyte invasion and preventing high density parasitemia. These findings advance our understanding of the targets and mechanisms of human immunity and evaluating the potential of PfRh4 as a component of candidate malaria vaccines.
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Li J, Han ET. Dissection of the Plasmodium vivax reticulocyte binding-like proteins (PvRBPs). Biochem Biophys Res Commun 2012; 426:1-6. [DOI: 10.1016/j.bbrc.2012.08.055] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 08/11/2012] [Indexed: 01/08/2023]
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Semenya AA, Tran TM, Meyer EV, Barnwell JW, Galinski MR. Two functional reticulocyte binding-like (RBL) invasion ligands of zoonotic Plasmodium knowlesi exhibit differential adhesion to monkey and human erythrocytes. Malar J 2012; 11:228. [PMID: 22770469 PMCID: PMC3464698 DOI: 10.1186/1475-2875-11-228] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 07/06/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Plasmodium knowlesi is a monkey malaria species that is becoming a serious public health concern infecting hundreds and perhaps thousands of humans in Southeast Asia. Invasion of erythrocytes by merozoites entails a cascade of molecular interactions. One step involves the adhesion of Plasmodium reticulocyte binding-like (RBL) proteins. Plasmodium knowlesi merozoites express only two RBL invasion ligands, known as Normocyte Binding Proteins (PkNBPXa and PkNBPXb). METHODS Overlapping N-terminal regions of PkNBPXa and PkNBPXb were expressed in COS7 cells and tested for surface expression and adhesion to rhesus monkey erythrocytes. Subsequent tests to study specific receptor ligand interactions included adhesion to a panel of human and non-human primate erythrocytes, enzymatic treatment, and site directed mutagenesis. RESULTS An N-terminal cysteine-rich region of PkNBPXb (PkNBPXb-II) exhibited specific adhesion to rhesus monkey erythrocytes. Mutation of four of five cysteines in PkNBPXb-II interfered with its surface expression on COS7 cells, suggesting disulphide bond conformation is critical for intracellular trafficking. Binding of PkNBPXb-II was abolished when rhesus erythrocytes were pre-treated with chymotrypsin, but not trypsin or neuraminidase. PkNBPXb-II also bound other Old World monkey species and gibbon erythrocytes. However, erythrocytes from other primate species including humans did not bind to PkNBPXb-II or native PkNBPXb. Importantly, unlike PkNBPXb, PkNBPXa bound human erythrocytes, and this binding was independent of the Duffy blood group determinant. CONCLUSIONS The data reported here begins to clarify the functional domains of the P. knowlesi RBLs. A binding domain has been identified and characterized in PkNBPXb. Notably, this study demonstrates that unlike PkNBPXb, PkNBPXa can bind to human erythrocytes, suggesting that PkNBPXa may function as a ligand to enable the invasion of P. knowlesi merozoites into human cells.
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Affiliation(s)
- Amma A Semenya
- Emory Vaccine Center and Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA
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Harvey KL, Gilson PR, Crabb BS. A model for the progression of receptor-ligand interactions during erythrocyte invasion by Plasmodium falciparum. Int J Parasitol 2012; 42:567-73. [PMID: 22710063 DOI: 10.1016/j.ijpara.2012.02.011] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Revised: 02/18/2012] [Accepted: 02/23/2012] [Indexed: 11/17/2022]
Abstract
Multiple and seemingly sequential interactions between parasite ligands and their receptors on host erythrocytes are an essential precursor to invasion by the obligate intracellular pathogen, Plasmodium falciparum. Consequently, identification and characterisation of the specific effectors that facilitate these recognition events are of special interest for the development of novel therapeutic and prophylactic solutions to malaria. There have been many recent advances regarding the identification of host-parasite receptor-ligand pairs, however the precise function and temporal aspects of these interactions are far from resolved. This review provides an update on the current details of these interactions to place them in sequence and super impose them upon the known kinetic events of invasion.
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Jackson KE, Pham JS, Kwek M, De Silva NS, Allen SM, Goodman CD, McFadden GI, Ribas de Pouplana L, Ralph SA. Dual targeting of aminoacyl-tRNA synthetases to the apicoplast and cytosol in Plasmodium falciparum. Int J Parasitol 2012; 42:177-86. [DOI: 10.1016/j.ijpara.2011.11.008] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 11/22/2011] [Accepted: 11/23/2011] [Indexed: 11/16/2022]
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Tham WH, Healer J, Cowman AF. Erythrocyte and reticulocyte binding-like proteins of Plasmodium falciparum. Trends Parasitol 2011; 28:23-30. [PMID: 22178537 DOI: 10.1016/j.pt.2011.10.002] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Revised: 10/11/2011] [Accepted: 10/11/2011] [Indexed: 11/30/2022]
Abstract
The global agenda for malaria eradication would benefit from development of a highly efficacious vaccine that protects against disease and interrupts transmission of Plasmodium falciparum. It is likely that such a vaccine will be multi-component, with antigens from different stages of the parasite life cycle. In this review, inclusion of blood stage antigens in such a vaccine is discussed. Erythrocyte binding-like (EBL) and P. falciparum reticulocyte binding-like (PfRh) proteins are reviewed with respect to their function in erythrocyte invasion, their role in eliciting antibodies contributing to protective immunity and reduction of invasion, leading subsequently to inhibition of parasite multiplication.
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Affiliation(s)
- Wai-Hong Tham
- Walter and Eliza Hall Institute of Medical Research, University of Melbourne, Parkville, VIC, Australia
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Chen L, Lopaticki S, Riglar DT, Dekiwadia C, Uboldi AD, Tham WH, O'Neill MT, Richard D, Baum J, Ralph SA, Cowman AF. An EGF-like protein forms a complex with PfRh5 and is required for invasion of human erythrocytes by Plasmodium falciparum. PLoS Pathog 2011; 7:e1002199. [PMID: 21909261 PMCID: PMC3164636 DOI: 10.1371/journal.ppat.1002199] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2010] [Accepted: 06/24/2011] [Indexed: 11/28/2022] Open
Abstract
Invasion of erythrocytes by Plasmodium falciparum involves a complex cascade of protein-protein interactions between parasite ligands and host receptors. The reticulocyte binding-like homologue (PfRh) protein family is involved in binding to and initiating entry of the invasive merozoite into erythrocytes. An important member of this family is PfRh5. Using ion-exchange chromatography, immunoprecipitation and mass spectroscopy, we have identified a novel cysteine-rich protein we have called P. falciparumRh5 interacting protein (PfRipr) (PFC1045c), which forms a complex with PfRh5 in merozoites. Mature PfRipr has a molecular weight of 123 kDa with 10 epidermal growth factor-like domains and 87 cysteine residues distributed along the protein. In mature schizont stages this protein is processed into two polypeptides that associate and form a complex with PfRh5. The PfRipr protein localises to the apical end of the merozoites in micronemes whilst PfRh5 is contained within rhoptries and both are released during invasion when they form a complex that is shed into the culture supernatant. Antibodies to PfRipr1 potently inhibit merozoite attachment and invasion into human red blood cells consistent with this complex playing an essential role in this process. The malaria parasite invades red blood cells by binding to proteins on the surface of this host cell. A family of proteins called P. falciparum reticulocyte binding-like homologue (PfRh) proteins are important for recognition of the red blood cell and activation of the invasion process. An important member of the PfRh family is PfRh5. We have identified a novel cysteine-rich protein we have called P. falciparumRh5 interacting protein (PfRipr), which forms a complex with PfRh5 in merozoites. PfRipr has 10 epidermal growth factor-like domains and is expressed in mature schizont stages where it is processed into two polypeptides that associate and form a complex with PfRh5. The PfRipr protein localises to the apical end of the merozoites in micronemes whilst PfRh5 is contained within rhoptries and both are released during invasion when they form a complex that is released into the culture supernatant. Antibodies to PfRipr1 can potently inhibit merozoite attachment and invasion into human red blood cells consistent with this complex playing an essential role in this process.
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Affiliation(s)
- Lin Chen
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Sash Lopaticki
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
| | - David T. Riglar
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Chaitali Dekiwadia
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Sciences and Biotechnology Institute, University of Melbourne, Melbourne, Australia
| | - Alex D. Uboldi
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
| | - Wai-Hong Tham
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Matthew T. O'Neill
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
| | - Dave Richard
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
| | - Jake Baum
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Stuart A. Ralph
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Sciences and Biotechnology Institute, University of Melbourne, Melbourne, Australia
| | - Alan F. Cowman
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
- * E-mail:
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Gaur D, Chitnis CE. Molecular interactions and signaling mechanisms during erythrocyte invasion by malaria parasites. Curr Opin Microbiol 2011; 14:422-8. [PMID: 21803641 DOI: 10.1016/j.mib.2011.07.018] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2011] [Revised: 07/11/2011] [Accepted: 07/12/2011] [Indexed: 01/24/2023]
Abstract
Invasion of erythrocytes by Plasmodium merozoites is a complex process that is mediated by specific molecular interactions. Here, we review recent studies on interactions between erythrocyte binding antigens (EBA) and PfRH proteins from the parasite and erythrocyte receptors involved in invasion. The timely release of these parasite ligands from internal organelles such as micronemes and rhoptries to the merozoite surface is critical for receptor-engagement leading to successful invasion. We review information on signaling mechanisms that control the regulated secretion of parasite proteins during invasion. Erythrocyte invasion involves the formation and movement of a junction between the invading merozoite and host erythrocyte. We review recent studies on the molecular composition of the junction and the molecular motor that drives movement of the junction.
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Affiliation(s)
- Deepak Gaur
- International Centre for Genetic Engineering and Biotechnology, New Delhi, India
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