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Amen A, Yoo R, Fabra-García A, Bolscher J, Stone WJR, Bally I, Dergan-Dylon S, Kucharska I, de Jong RM, de Bruijni M, Bousema T, King CR, MacGill RS, Sauerwein RW, Julien JP, Poignard P, Jore MM. Target-agnostic identification of human antibodies to Plasmodium falciparum sexual forms reveals cross stage recognition of glutamate-rich repeats. bioRxiv 2024:2023.11.03.565335. [PMID: 37961136 PMCID: PMC10635103 DOI: 10.1101/2023.11.03.565335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Circulating sexual stages of Plasmodium falciparum (Pf) can be transmitted from humans to mosquitoes, thereby furthering the spread of malaria in the population. It is well established that antibodies (Abs) can efficiently block parasite transmission. In search for naturally acquired Ab targets on sexual stages, we established an efficient method for target-agnostic single B cell activation followed by high-throughput selection of human monoclonal antibodies (mAbs) reactive to sexual stages of Pf in the form of gamete and gametocyte extract. We isolated mAbs reactive against a range of Pf proteins including well-established targets Pfs48/45 and Pfs230. One mAb, B1E11K, was cross-reactive to various proteins containing glutamate-rich repetitive elements expressed at different stages of the parasite life cycle. A crystal structure of two B1E11K Fab domains in complex with its main antigen, RESA, expressed on asexual blood stages, showed binding of B1E11K to a repeating epitope motif in a head-to-head conformation engaging in affinity-matured homotypic interactions. Thus, this mode of recognition of Pf proteins, previously described only for PfCSP, extends to other repeats expressed across various stages. The findings augment our understanding of immune-pathogen interactions to repeating elements of the Plasmodium parasite proteome and underscore the potential of the novel mAb identification method used to provide new insights into the natural humoral immune response against Pf . Impact Statement A naturally acquired human monoclonal antibody recognizes proteins expressed at different stages of the Plasmodium falciparum lifecycle through affinity-matured homotypic interactions with glutamate-rich repeats.
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Miglianico M, Bolscher JM, Vos MW, Koolen KJM, de Bruijni M, Rajagopal DS, Chen E, Kiczun M, Gray D, Campo B, Sauerwein RW, Dechering KJ. Assessment of the drugability of initial malaria infection through miniaturized sporozoite assays and high-throughput screening. Commun Biol 2023; 6:216. [PMID: 36823266 PMCID: PMC9950425 DOI: 10.1038/s42003-023-04599-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Accepted: 02/15/2023] [Indexed: 02/25/2023] Open
Abstract
The sporozoite stages of malaria parasites are the primary cause of infection of the vertebrate host and are targeted by (experimental) vaccines. Yet, little is known about their susceptibility to chemical intervention. Phenotypic high-throughput screens have not been feasible due to a lack of in vitro systems. Here we tested 78 marketed and experimental antimalarial compounds in miniaturized assays addressing sporozoite viability, gliding motility, hepatocyte traversal, and intrahepatocytic schizogony. None potently interfered with sporozoite viability or motility but ten compounds acted at the level of schizogony with IC50s < 100 nM. To identify compounds directly targeting sporozoites, we screened 81,000 compounds from the Global Health Diversity and reFRAME libraries in a sporozoite viability assay using a parasite expressing a luciferase reporter driven by the circumsporozoite promoter. The ionophore gramicidin emerged as the single hit from this screening campaign. Its effect on sporozoite viability translated into reduced gliding motility and an inability of sporozoites to invade human primary hepatocytes and develop into hepatic schizonts. While providing proof of concept for a small molecule sporontocidal mode of action, our combined data indicate that liver schizogony is more accessible to chemical intervention by (candidate) antimalarials.
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Affiliation(s)
| | | | | | | | | | | | - Emily Chen
- Calibr, a division of The Scripps Research Institute, La Jolla, California, United States of America
| | - Michael Kiczun
- Drug Discovery Unit, University of Dundee, Dundee, United Kingdom
| | - David Gray
- Drug Discovery Unit, University of Dundee, Dundee, United Kingdom
| | - Brice Campo
- Medicines for Malaria Venture, Geneva, Switzerland
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Ivanochko D, Fabra-García A, Teelen K, van de Vegte-Bolmer M, van Gemert GJ, Newton J, Semesi A, de Bruijni M, Bolscher J, Ramjith J, Szabat M, Vogt S, Kraft L, Duncan S, Lee SM, Kamya MR, Feeney ME, Jagannathan P, Greenhouse B, Sauerwein RW, Richter King C, MacGill RS, Bousema T, Jore MM, Julien JP. Potent transmission-blocking monoclonal antibodies from naturally exposed individuals target a conserved epitope on Plasmodium falciparum Pfs230. Immunity 2023; 56:420-432.e7. [PMID: 36792575 PMCID: PMC9942874 DOI: 10.1016/j.immuni.2023.01.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 11/04/2022] [Accepted: 01/12/2023] [Indexed: 02/16/2023]
Abstract
Pfs230 is essential for Plasmodium falciparum transmission to mosquitoes and is the protein targeted by the most advanced malaria-transmission-blocking vaccine candidate. Prior understanding of functional epitopes on Pfs230 is based on two monoclonal antibodies (mAbs) with moderate transmission-reducing activity (TRA), elicited from subunit immunization. Here, we screened the B cell repertoire of two naturally exposed individuals possessing serum TRA and identified five potent mAbs from sixteen Pfs230 domain-1-specific mAbs. Structures of three potent and three low-activity antibodies bound to Pfs230 domain 1 revealed four distinct epitopes. Highly potent mAbs from natural infection recognized a common conformational epitope that is highly conserved across P. falciparum field isolates, while antibodies with negligible TRA derived from natural infection or immunization recognized three distinct sites. Our study provides molecular blueprints describing P. falciparum TRA, informed by contrasting potent and non-functional epitopes elicited by natural exposure and vaccination.
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Affiliation(s)
- Danton Ivanochko
- Program in Molecular Medicine, the Hospital for Sick Children Research Institute, Toronto, ON, Canada
| | | | - Karina Teelen
- Department of Medical Microbiology, Radboudumc, Nijmegen, the Netherlands
| | | | | | - Jocelyn Newton
- Program in Molecular Medicine, the Hospital for Sick Children Research Institute, Toronto, ON, Canada
| | - Anthony Semesi
- Program in Molecular Medicine, the Hospital for Sick Children Research Institute, Toronto, ON, Canada
| | | | | | - Jordache Ramjith
- Radboud Institute for Health Sciences, Department for Health Evidence, Biostatistics Section, Radboudumc, Nijmegen, the Netherlands
| | | | | | - Lucas Kraft
- AbCellera Biologics Inc., Vancouver, BC, Canada
| | | | - Shwu-Maan Lee
- PATH's Malaria Vaccine Initiative, Washington, DC 20001, USA
| | - Moses R Kamya
- Infectious Disease Research Collaboration, Kampala, Uganda
| | - Margaret E Feeney
- Department of Medicine, University of California, San Francisco, San Francisco, CA, USA; Department of Pediatrics, University of California, San Francisco, San Francisco, CA, USA
| | - Prasanna Jagannathan
- Department of Microbiology and Immunology, Stanford University, Stanford, CA, USA
| | - Bryan Greenhouse
- Department of Medicine, University of California, San Francisco, San Francisco, CA, USA
| | | | - C Richter King
- PATH's Malaria Vaccine Initiative, Washington, DC 20001, USA
| | | | - Teun Bousema
- Department of Medical Microbiology, Radboudumc, Nijmegen, the Netherlands.
| | - Matthijs M Jore
- Department of Medical Microbiology, Radboudumc, Nijmegen, the Netherlands.
| | - Jean-Philippe Julien
- Program in Molecular Medicine, the Hospital for Sick Children Research Institute, Toronto, ON, Canada; Departments of Biochemistry and Immunology, University of Toronto, Toronto, ON, Canada.
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