Characterising mechanisms of macrophage subversion by Leishmania parasites (360G-Wellcome-099785_Z_12_Z)

This project aims to learn how Leishmania parasites can survive and prosper within macrophages. Recent metabolomics experiments have revealed that Leishmania produce and secrete large quantities of citrulline, a metabolic product of arginine deimination. Arginine is a precursor to nitric oxide, a toxic metabolite used as a key part of the antimicrobial reaction cascade within the macrophage. We hypothesise that conversion of arginine to citrulline by Leishmania parasites might be used to limit host-cell access to arginine and thus restrict its ability to create nitric oxide, thus contributing to the parasite's ability to survive. We have identified a gene in the Leishmania genome that is a candidate arginine deiminase, i.e. an enzyme capable of converting arginine to citrulline. We propose to verify thisrole by expressing the gene and assessing activity and also knocking the gene out in Leishmania to determine whether citrulline production is altered and how this affects other phenotypic traits including macrophage infectivity and survival. It is also clear that Leishmania parasites can prevent macrophages entering their activated state. We will therefore also investigate how macrophage metabolism is influenced during activation and how wild type and mutant Leishmania parasites affect these metabolic correlates to macrophage activation.