FIG. 4.

Inhibitory effect of gp30 and recombinant gp82 on host cell invasion of gp82-deficient T. cruzi isolates. Metacyclic forms of isolates 569 and 588 were added to HeLa cells that had been left unincubated or had been preincubated for 15 min with 60 μg of native gp30 per ml (A) or with 80 μg of J18 per ml (B), the recombinant protein containing the entire gp82 sequence. After 1 h at 37°C, the intracellular parasites in a total of at least 500 Giemsa-stained cells were counted. A reference value of 100% was ascribed to the control without the T. cruzi protein. Values are the means and SD of three experiments performed in duplicate. (C) HeLa cells were preincubted with purified gp30 or J18 at the indicated concentrations before the addition of metacyclic forms of T. cruzi isolate 569. Representative results of a set of experiments are shown. Values are the means and SD of triplicate determinations. (D) SDS-PAGE gel containing the extract of T. cruzi isolate 569 (Ext), purified gp30, and molecular size markers (M), stained with Coomassie blue.