FIG. 1.

Cyclosporine inhibition of C. parvum growth in in vitro cultures. The following experiments are shown. (i) C. parvum oocysts were added to Caco-2 cell monolayers for 3 h in the presence of cyclosporine (0.1 to 50 μM), unexcysted oocysts were washed out, and the parasites were cultured for a further 48 h in the presence of the drug, for a total of 51 h (51 hr). (ii) Oocysts were added to the monolayers for 3 h in the presence of the drug, the drug and unexcysted oocysts were removed by washing, and the parasites were cultured for a further 48 h without the drug (3 hr). (iii) Oocysts were added to the monolayers for 3 h without the drug, unexcysted oocysts were removed, and the parasites were cultured for 48 h with the drug (48 hr). Parasite numbers were estimated from the IFA, using the polyclonal antibody in one experiment and, in the second, MAb 1D8. Drug activity was calculated as percent inhibition of growth, and the results represent two separate experiments. The error bars indicate standard deviations. (A) Bar graphs were plotted with Microsoft Excel software. The cyclosporine used in this experiment was from Sigma. (B) Values for percent inhibition for a 51 h incubation plotted in a linear graph, with 50% inhibition shown by the dashed line. All assays were plotted similarly to determine IC₅₀s. (C) Oocysts were excysted in the presence of cyclosporine for 1 h, the drug was removed, and the parasites were added to Caco-2 cells and cultured for 48 h without the drug. Fifty-percent inhibition is shown by the dashed line.