Cystatins of parasitic organisms.

The cystatin superfamily comprises several groups of protease inhibitors. In this chapter we will focus on I25 family members, which consist predominantly of the type 2 cystatins. Recently, a wealth of information on these molecules and their activities has been described. Parasite cystatins are shown to have dual functions via interaction with both parasite and host proteases. Thereby, parasite cystatins are not only essentially involved in the regulation of physiological processes during parasite development, but also represent important pathogenicity factors. Interestingly, some studies indicate that parasite cystatins evolved exceptional immuno-modulatory properties. these capacities could be exploited to interfere with unwanted immune responses in unrelated human inflammatory diseases. We highlight the different biological roles of parasite cystatins and the anticipated future developments.