Poster Presentation Lorne Infection and Immunity 2022

Identifying the mechanisms of action of novel invasion-blocking compounds in Plasmodium falciparum (#178)

Dawson Ling 1 2 , Madeline Dans 1 3 , Greta Weiss 1 , Zahra Razook 4 5 , Somya Mehra 4 6 , Alyssa Barry 4 5 , Brendan Crabb AC 1 2 , Hayley Bullen 1 2 , Paul Gilson 1 2
  1. Malaria Virulence and Drug Discovery Group, Burnet Institute, Melbourne, Victoria, Australia
  2. Microbiology & Immunology, The University of Melbourne, Parkville, Victoria, Australia
  3. Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
  4. Burnet Institute, Melbourne, Victoria, Australia
  5. School of Medicine, Deakin University, Waurn Ponds, Victoria, Australia
  6. School of Mathematics and Statistics, The University of Melbourne, Parkville, Victoria, Australia

Malaria is a devastating acute febrile disease caused by Plasmodium parasites that are spread to people through the bites of infected female Anopheles mosquitoes. Malaria clinical symptoms (e.g. fever, chills, nausea and vomiting) manifest during the parasite blood stage when parasites invade human red blood cells (RBCs), proliferate and reinfect RBCs. In 2020, nearly half of the world’s population was at risk of malaria and 627,000 malaria deaths were reported.1 Plasmodium falciparum is the deadliest species, accounting for almost all malaria deaths in 2021.1 In recent years, parasites’ emerging resistance against all frontline antimalarials contribute to the slow decrease in malaria cases and threatens the progress of malaria eradication. This stresses the importance of new drugs blocking novel parasite mechanisms, specifically parasite invasion, an extracellular process critical for parasite proliferation. To accelerate the discovery of new antimalarials, Medicines for Malaria Venture released two open-access compound libraries, the Malaria and Pathogen Box. Our group’s recent screening of the Pathogen Box for RBC invasion inhibitors unveiled the invasion-blocking compound, MMV687794.2 Whole-genome sequencing and variant analyses of MMV687794-resistant parasites indicated mutations in an α/β-hydrolase, possibly responsible for RBC lipid remodelling for downstream parasite processes (e.g. lipid metabolism and/or signal transduction) essential for efficient invasion. These mutations have been introduced into wild-type parasites using CRISPR/Cas9 to establish that the mutations alone confer resistance to MMV687794. Likewise, an epitope tag and riboswitch are introduced into the gene, allowing for further functional biochemical and phenotypic analyses of the α/β-hydrolase via protein knockdown and localisation. If MMV687794 is shown to target the α/β-hydrolase specifically, protein crystallography of the compound-enzyme complex is achievable, which may lead to improved rational drug design and increase our understanding of parasite invasion machinery. Indirect immunofluorescence microscopy thus far suggests that the α/β-hydrolase is localised to the rhoptry, supporting the enzyme’s crucial role in invasion.

 

  1. World Health Organization. World Malaria Report 2021. Geneva: World Health Organization; 2021.
  2. Dans MG, Weiss GE, Wilson DW, Sleebs BE, Crabb BS, de Koning-Ward TF, et al. Screening the Medicines for Malaria Venture Pathogen Box for invasion and egress inhibitors of the blood stage of Plasmodium falciparum reveals several inhibitory compounds. bioRxiv. 2020:768648.