Characterisation of a cysteine protease expressed by Eimeria tenella and identification of its post-traductionnal regulator

Session Poster : Invasion and motilitySession Poster : Invasion and motility; Cysteine proteases of the papain family are major virulent factors expressed by protozoa. They have been involved in many steps of parasites life cycle like cell invasion, intracellular replication, gametocyte formation and parasite differentiation. Their multiple roles in key steps of parasites biology make them attractive new therapeutic targets. Using BlastP, we identified 5 genes encoding for cysteine proteases in the genome of E. tenella. We named them Eimeripain, EtCPL, EtCPC1, EtCPC2 and EtCPC3 encoding respectively for one cathepsin B, one cathepsin L, and three cathepsin C. Complementary approaches of molecular biology and biochemistry revealed that most of these proteases are highly expressed and active in the unsporulated oocysts, suggesting a role in sporulation and/or gametogenesis. Eimeripain is the only activity that persists throughout the life cycle. We show that a specific inhibitor of Human cathepsin B, CA074-ME, inhibits Eimeripain and affects the capacity of sporozoites to invade MDBK cells. These data suggest that Eimeripain plays a central and pleiotropic role in Eimeria life cycle. Cysteine protease inhibitors from the Chagasin family are proteins expressed by protozoa that specifically bind to and inhibit cysteine cathepsins. As such, they participate to parasite pathogenesis. We identified a cysteine protease inhibitor, Eimestatine, expressed by E. tenella, which specifically inhibits the activity of Eimeripain in biochemical assays. Preliminary data suggest that Eimestatine forms a complex at each life stage, which may indicate a tight regulation of Eimeripain throughout the infectious process.