Antifungal Activity of the Noncytotoxic Human Peptide Hepcidin 20 against Fluconazole-Resistant Candida glabrata in Human Vaginal Fluid

Vaginal infections due to Candida glabrata are difficult to eradicate, due to the scarce susceptibility to azoles of this species. Previous studies have shown that the human cationic peptide hepcidin 20 (Hep-20) exerts fungicidal activity in sodium phosphate buffer against a panel of C. glabrata clinical isolates with different susceptibility to fluconazole. In addition, the activity of the peptide was potentiated under acidic condition, suggesting a potential application in the topical treatment of vaginal infections. To investigate whether the peptide activity could be maintained in biological fluids, in this study the antifungal activity of Hep-20 was evaluated by killing assay in (i) a vaginal fluid simulant (VFS), and in (ii) a human vaginal fluid (HVF) collected from three healthy donors. The results obtained indicated that the activity of the peptide was maintained in VFS and HVF supplemented with EDTA. Interestingly, the fungicidal activity of Hep-20 was enhanced in HVF, in comparison to that observed in VFS, with a minimal fungicidal concentration of 25 μΜ for all donors. No cytotoxic effect on human cells was exerted by Hep-20 at concentrations ranging from 6.25 to 100 μΜ, as shown by XTT reduction assay and propidium iodide staining. An indirect evidence of Hep-20 stability was also obtained from co-incubation experiments of the peptide with HVF at 37°C for 90 minutes and 24 hours. Collectively, these results indicate that this peptide should be further studied as a potential novel therapeutic agent for the topical treatment of vaginal C. glabrata infections.