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Parkyn Schneider M, Looker O, Rebelo M, Khoury DS, Dixon MWA, Oeuvray C, Crabb BS, McCarthy J, Gilson PR. The delayed bloodstream clearance of Plasmodium falciparum parasites after M5717 treatment is attributable to the inability to modify their red blood cell hosts. Front Cell Infect Microbiol 2023; 13:1211613. [PMID: 37457953 PMCID: PMC10340534 DOI: 10.3389/fcimb.2023.1211613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 06/14/2023] [Indexed: 07/18/2023] Open
Abstract
M5717 is a promising antimalarial drug under development that acts against multiple stages of the life cycle of Plasmodium parasites by inhibiting the translation elongation factor 2 (PfeEF2), thereby preventing protein synthesis. The parasite clearance profile after drug treatment in preclinical studies in mice, and clinical trials in humans showed a notable delayed clearance phenotype whereby parasite infected red blood cells (iRBCs) persisted in the bloodstream for a significant period before eventual clearance. In a normal P. falciparum infection iRBCs sequester in the deep circulation by cytoadherence, allowing them to avoid surveillance and clearance in the spleen. We found that M5717 blocks parasite modification of their host red blood cells (RBCs) by preventing synthesis of new exported proteins, rather than by directly blocking the export of these proteins into the RBC compartment. Using in vitro models, we demonstrated that M5717 treated ring/trophozoite stage iRBCs became less rigid, and cytoadhered less well compared to untreated iRBCs. This indicates that in vivo persistence of M5717 treated iRBCs in the bloodstream is likely due to reduced cytoadherence and splenic clearance.
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Affiliation(s)
| | | | - Maria Rebelo
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
| | - David S. Khoury
- Kirby Institute, University of New South Wales, Sydney, NSW, Australia
| | | | | | - Brendan S. Crabb
- Burnet Institute, Melbourne, VIC, Australia
- University of Melbourne, Melbourne, VIC, Australia
- Monash University, Melbourne, VIC, Australia
| | | | - Paul R. Gilson
- Burnet Institute, Melbourne, VIC, Australia
- University of Melbourne, Melbourne, VIC, Australia
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Shao J. Labeling Strategies for Surface-Exposed Protein Visualization and Determination in Plasmodium falciparum Malaria. Front Cell Infect Microbiol 2022; 12:914297. [PMID: 35755836 PMCID: PMC9226428 DOI: 10.3389/fcimb.2022.914297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 05/11/2022] [Indexed: 11/13/2022] Open
Affiliation(s)
- Jinfeng Shao
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, United States
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Epigenetics of malaria parasite nutrient uptake, but why? Trends Parasitol 2022; 38:618-628. [PMID: 35641406 PMCID: PMC9283302 DOI: 10.1016/j.pt.2022.05.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Revised: 05/01/2022] [Accepted: 05/10/2022] [Indexed: 11/23/2022]
Abstract
The conserved plasmodial surface anion channel (PSAC) mediates nutrient uptake by bloodstream malaria parasites and is an antimalarial target. This pathogen-associated channel is linked to the clag multigene family, which is variably expanded in Plasmodium spp. Member genes are under complex epigenetic regulation, with the clag3 genes of the human P. falciparum pathogen exhibiting monoallelic transcription and mutually exclusive surface exposure on infected erythrocytes. While other multigene families use monoallelic expression to evade host immunity, the reasons of epigenetic control of clag genes are unclear. I consider existing models and their implications for nutrient acquisition and immune evasion. Understanding the reasons for epigenetic regulation of PSAC-mediated nutrient uptake will help clarify host-pathogen interactions and guide development of therapies resistant to allele switching.
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