Crypotastatin, an ICP of Cryptosporidium parvum, may play a role in invasion of host cells [54], the overexpression of chagasin in T. cruzi reduces the infection rate in vitro and in vivo, and a chagasin null mutant had a lower differentiation rate due to changes in activity of parasite cell surface cysteine proteases [26], [27], [55]. Here, CTSB is linked to infection.