Effect of ritonavir and saquinavir on Candida albicans growth rate and in vitro activity of aspartyl proteinases.

An in vitro study to evaluate the antifungal effect and activity of aspartyl proteinases of the HIV-proteinase inhibitors ritonavir and saquinavir was conducted. Ritonavir diminished the growth rate of Candida albicans as well as the activity of its secreted aspartyl proteinases (Saps) in a nitrogen-limited medium, yeast carbon base and bovine serum albumin (YCB-BSA). This inhibition occurred in a dose-dependent fashion; with 8 mg l(-1) of ritonavir a partial growth inhibition (44%) was produced. The growth rate of C. albicans in medium with saquinavir was similar to that seen in the control, and Sap activity was inhibited only at high concentrations. In conventional medium (RPMI-1640), which does not induce the production of yeast proteases, no inhibitory effect was detected with either HIV-protease inhibitor.