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Biology subjects

Yeoh, L. M.

Publications and source records attributed to Yeoh, L. M..

3 recordsLinked to original sources

PfK13-associated artemisinin resistance slows drug activation and enhances antioxidant defence, which can be overcome with sulforaphane.

Artemisinin resistance is globally prevalent, including in Africa, raising concerns and highlighting the need to better understand the cellular mechanisms behind this resistance. In Plasmodium falciparum, artemisinin resistance is primarily attributed to mutations in the PfKelch13 (PfK13) gene. In this study, we performed proteomic analysis on a range of sensitive and artemisinin-resistant parasites (both laboratory-generated and field isolates), revealing specific dysregulation of PfK13 protein abundance. Reduced PfK13 levels were linked to impaired hemoglobin digestion, decreased free heme levels, and consequently, decreased artemisinin activation. Artemisinin resistant parasites also exhibited elevated thiol levels, indicating a more reduced cellular state. Targeting the parasite redox capacity with sulforaphane potentiated artemisinin activity in vitro and in an in vivo rodent Plasmodium berghei model, offering a potential strategy to overcome resistance. Our findings provide critical insights into the molecular mechanisms of artemisinin resistance and suggest novel therapeutic interventions to restore drug sensitivity. One Sentence Summary: PfK13 mutations drive artemisinin resistance in Plasmodium parasites by enhancing antioxidant defences, which can be targeted by redox modulators such as sulforaphane.

microbiology↗

Potent AMA1-specific human monoclonal antibody against P. vivax Pre-erythrocytic and Blood Stages

New therapeutics are necessary for preventing Plasmodium vivax malaria due to easy transmissibility and dormancy in the liver that increases the clinical burden due to recurrent relapse. We isolated 12 Pv Apical Membrane Antigen 1 (PvAMA1) specific human monoclonal antibodies from Peripheral Blood Mononuclear Cells of a Pv-exposed individual. PvAMA1 is essential for sporozoite and merozoite invasion, making it a unique therapeutic target. HumAb 826827 blocked the invasion of human erythrocytes using Pv clinical isolates and inhibited sporozoite invasion of human hepatocytes in vitro (IC50 of 0.3 - 3.7 {micro}g/mL). It also significantly reduced liver infection of chimeric FRG-humHep mice in vivo. The crystal structure of rPvAMA1 bound to 826827 shows that 826827 partially occupies the highly conserved hydrophobic groove in PvAMA1 that binds its known receptor, RON2. We have isolated a potent humAb that is isolate-transcendent, blocks both pre-erythrocytic and blood stage infection, and could be a new therapy for Pv.

immunology↗

Malaria parasite resistance to azithromycin is not readily transmitted by mosquitoes

Antimalarials are now used in combination with partner drugs to stem parasite drug resistance. Partners are often older, safe, cheap drugs, but resistance is already circulating for many, which raises the risk of selecting for multidrug resistance. If the partner drug(s) could be refractory to the spread of resistance, better resistance control could be implemented. We tested whether resistance to the antibiotic azithromycin, which kills malaria parasites by perturbing prokaryote-like protein synthesis in the apicoplast (relict plastid), had fitness costs to the spread of parasites via mosquitoes where parasites are not under drug pressure. Azithromycin resistance mutations in both rodent and human malaria parasites had a negative impact on the ability of resistant parasites to transmit from one vertebrate host to another via mosquitoes. Azithromycin resistance will therefore be less likely to spread geographically, making it an attractive option as a perennial partner compound to protect appropriate frontline antimalarials.

molecular biology↗