Cells and parasite cultures.

T. cruzi epimastigotes (CL strain clone 14) were maintained in the exponential growth phase by subculturing every 48 h in LIT medium at 28°C (41). The Chinese hamster ovary cell line (CHO-K₁) was cultivated in RPMI 1640 medium supplemented with 10% heat-inactivated FCS, 0.15% (wt/vol) NaHCO₃, 100 U/ml penicillin, and 100 mg/ml streptomycin at 37°C in a humidified atmosphere containing 5% CO₂. Trypomastigotes were obtained by infection in CHO-K₁ cells with trypomastigotes at 37°C in the presence of 10% FCS. After 24 h, the cells were maintained at 33°C and 2% FCS (42). Trypomastigotes were collected from the extracellular medium 5 days after infection.