FIG. 2.

ATP content and adhesion-invasion capacity of T. cruzi metacyclic forms (G strain) subjected to nutritional stress. (A, B, and C) Parasites were maintained in PBS for the indicated time periods and were then analyzed with regard to the ATP content (A) and the ability to attach to (B) or to enter (C) HeLa cells. Representative results of one out of three experiments are shown. Values represent the means ± standard deviations of the results of triplicate experiments. In panels B and C, after 1 h of incubation with parasites, HeLa cells were stained with Giemsa and the numbers of attached or intracellular parasites in 250 cells were counted. (D) Giemsa-stained control and starved parasites. (E) The expression levels of the surface molecules gp90 and gp35-gp50 were determined in control (shaded) and starved (unshaded) parasites by flow cytometry, using MAb 1G7 and MAb 10D8, respectively. (F) The susceptibility of control and starved parasites to complement-mediated lysis by anti-gp90 MAb 1G7 at various concentrations was determined.