Natural peptidase inhibitors of trypanosomatids. (360G-Wellcome-081877_Z_06_Z)

We shall characterise the roles of two unusual classes of natural peptidase inhibitors in the trypanosomatid parasitic protozoa Leishmania major and Trypanosoma brucei. Neither inhibitor has a mammalian orthologue. The first, inhibitor of serine peptidase (ISP), is similar to bacterial ecotin. We hypothesise that the parasite ISPs inhibit host serine peptidases, thereby facilitating infection and pathogenicity. We shall generate and use ISP-deficient mutants of L. major and T. brucei to inv estigate how ISP influences host-parasite interactions (eg Leishmania with neutrophils and macrophages in vitro and in vivo: T. brucei proliferation and CNS invasion). We shall characterise the inhibitory properties of ISPs, and their expression and trafficking within the parasites, in order to identify the potential key mammalian targets enzymes and so informed insights into the roles of parasite ISPs. The second natural peptidase inhibitor is ICP (inhibitor of cysteine peptidase). Analy sis of a T. brucei ICP-deficient mutant suggests that the inhibitor modulates endogenous CP activity. By generating a CP-deficient mutant and comparing its phenotype with the ICP-deficient mutant, we shall study the contribution of cysteine peptidase (CP) activity to T. brucei infection and pathogenicity, particularly using a blood brain barrier model, and elucidate the functional role of the parasite s ICP.