The effects of p-chloromercuriphenylsulfonic acid on Trypanosoma cruzi infection of mammalian host cells in vitro

Treatment of Trypanosoma cruzi blood trypomastigotes with p-chloromercuriphenylsulfonic acid (PCMS) increased the association of the parasite with either mouse resident peritoneal macrophages or rat heart myoblasts in vitro. The effect was evidenced by elevation of both the percentage of host cells with parasites and the number of flagellates per 100 cells. The effect of PCMS appeared to be largely on the process of parasite penetration rather than surface binding as it was seen at 37 degrees C but not at 4 degrees C. A short pretreatment time, 5 min, was sufficient to elicit the enhancement, suggesting that the primary effect of PCMS might be at the parasite's cell surface. The PCMS effect was reversible as the parasite returned to normal levels of association with the host cells in less than 4 h after removal of excess PCMS. That sulfhydryl groups were involved in the PCMS effect was indicated by the abilities of excess cysteine and glutathione to block it. These results suggest a role for free sulfhydryl groups on the parasite surface in the process of host cell invasion.