Parameters affecting the inhibition of Candida albicans GDH 2023 and GRI 2773 blastospore viability by purified synthetic salivary histidine‐rich polypeptides

Purified synthetic salivary histidine‐rich polypeptides, HRPs 2, 3, 4, 5, and 6, were observed to inhibit Candida albicans blastospore viability at yeast cell concentrations ranging from 102 to greater than 106 colony forming units per ml. Among the HRPs, HRP‐4 was the best inhibitor with significant killing activity noted at a peptide concentration of 0.5 μg per ml. Antifungal potency under growth conditions was observed to be dependent upon pH. In contrast, killing did not vary throughout the pH range tested under non‐growth conditions. Electron microscopy results demonstrated HRP damage at pH 5 which appeared to be initiated at the membrane. At pH 7.4, micrographs revealed clear evidence of intracellular destruction suggesting more extensive damage at neutral as compared to acidic pH. These results suggest that within the changing realm of the oral cavity, the HRPs would be expected to be potent killers of C. albicans.