Effects of proteinase inhibitors on the growth and differentiation of Trypanosoma cruzi.

Three proteinase inhibitors, one peptidyl acyloxymethyl ketone (AMK), Z-Phe-Lys-CH2-OCO-(2,4,6-Me3)Ph.HCl, and two diazomethyl ketones (DMKs), Z-Phe-Phe-DMK and Z-Phe-Ala-DMK, have been studied for their effects in vitro on the four developmental stages of Trypanosoma cruzi. The three inhibitors penetrated living parasites and inhibited the major cysteine proteinase, cruzipain. The AMK was the most potent inhibitor of cruzipain itself and at 20 microM caused lysis of epimastigotes and trypomastigotes. When at lower concentrations, however, it had little effect on epimastigote growth but reduced metacyclogenesis. The DMKs had no effect against epimastigotes but inhibited differentiation to metacyclics. All three inhibitors markedly reduced infection of Vero cells by the parasite and the multiplication of the intracellular amastigotes, whereas release of trypomastigotes was almost entirely prevented. The results confirm the importance of cysteine proteinases in the life cycle of T. cruzi, and suggest that the differentiation steps are the most susceptible to cysteine proteinase inhibitors.