Identification of Inhibitors against P.Falciparum GAP50 and Human Complement Factor H Interaction in the Mosquito

Abstract

Malaria is an infectious disease caused by obligate intracellular parasites of the genus Plasmodium. Severe malaria cases result in more than half a million deaths every year (World Malaria Report, 2013). Mosquitoes transmit the parasite from human to human during their blood meals. With the blood meal, mosquitoes ingest female and male gametocytes present in the blood of a Plasmodium infected human. Gametocytes develop into gametes (Aly et al, 2009) that undergo fertilization inside the mosquito's gut and later result in the formation of infectious sporozoites that are transmitted during a bite. This uptake, maturation and fertilization, represents a bottleneck in the parasite's life cycle, and a prime target for transmission blocking. In the mosquito's gut, macrogametes (female gametes) bind the human complement control regulator protein, hFactor H, via PfGAP50 to avoid complement-mediated lysis (Simon et al, 2013). A potential transmission-blocking small molecule inhibitor would disrupt the PfGAP50-hFactor H interaction, exposing the parasite to the human alternate pathway of complement for destruction.The goal of this project is to characterize the PfGAP50-hFactor H interaction in vitro, and to screen the Medicines for Malaria Venture Malaria Box library for small molecule protein-protein interaction (PPI) inhibitors using a surface plasmon resonance (SPR)-based assay. Several PPI inhibitors were identified and the inhibitory affect was further validated in a concentration-dependent SPR screen. Promising hits will be further tested in mosquitos. In vitro characterization of this interaction will provide a better understanding of pathogen-host interactions at a molecular level and allow the development of specific inhibitors of PfGAP50-hFactor H interaction in the mosquito.