Enabling Host Processes for Defense Against Liver Stage Malaria Infection

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Project Summary/Abstract Malaria remains a devastating disease in underdeveloped countries across the globe despite significant efforts to eradicate the infectious agents, unicellular parasites from the genus Plasmodium. Existing malaria therapies target the pathogenic parasites when their numbers are greatest, which creates selection pressure and hastens the development of drug resistant parasites. New therapeutic approaches are urgently needed. This project will exploit our recent discoveries about host liver cell factors essential for malaria to expand our understanding of parasitic infection and facilitate the development of novel therapeutic strategies that target host pathways. During the course of malaria infection, a precise sequence of events occurs first within human liver cells resulting in distinct morphological changes and aggressive Plasmodium replication as parasite numbers increase 10,000-fold. Also within the liver, dormant parasite forms termed hypnozoites can cause relapse months or even years after the initial infection. Both liver malaria forms remain elusive despite their significance to disease manifestation. Through an integrative approach that combines gene sequencing technologies and a forward genetic screen in Iiver cells, we discovered several human genes that are critical to Plasmodium parasite development. In particular, the host gene AQP3 (aquaporin-3) is essential for parasite viability and is up-regulated throughout the course of liver infection. AQP3 encodes an aquaglyceroporin that is generally associated with the host cell membrane. This proposal will explore the hypothesis that Plasmodium repurposes AQP3 for survival and that targeting host processes represents a strategic approach to prevent and treat malaria. We propose that the parasite hijacks AQP3 and incorporates it into the parasitophorous vacuole membrane, which surrounds the parasites. We predict that Plasmodium parasites use this protein to import essential components into the parasitophorous vacuole for proper growth and maturation. Therefore, targeting this host protein may provide a powerful and distinct approach to overcome drug resistant malaria. We will use the accessible cell-based P. berghei and P. falciparum liver stage models to track nutrients in parasite-infected cells as a function of AQP3 gene expression and protein localization. The mechanisms by which Plasmodium influences host gene expression will also be explored. Lastly, we will use chemical probes to specifically inhibit the host target to evaluate phenotypes and examine druggability. Together, these systems will expand our understanding of host-parasite interactions and allow us to evaluate host proteins as malaria drug targets to reduce resistance. !