Protection of the oral mucosa by salivary histatin-5 against Candida albicans in an ex vivo murine model of oral infection.

The oral cavity is a primary target for opportunistic infections, particularly oral candidiasis caused by Candida albicans. A commensal fungus commonly colonizing mucosal surfaces, under conditions of immune dysfunction, C. albicans can become a pathogen causing recurrent infections. Yet, the role of host oral innate immunity in the development of candidiasis is not fully elucidated. Specifically, the host salivary antimicrobial peptide histatin-5 (Hst-5) has been proposed to play a protective role in the oral cavity against C. albicans. However, investigations demonstrating its efficacy on oral tissue have been lacking. To this end, in this study, an ex vivo murine model of oral infection was developed. Viable C. albicans counts and histopathological analyses demonstrated a significant protective effect for Hst-5 on mouse oral tissue against C. albicans. More importantly, host saliva exerted a comparable anticandidal effect. However, this effect was neutralized upon treatment of saliva with proteases and C. albicans, previously shown to degrade Hst-5, indicating that Hst-5 is likely the salivary component responsible for the observed protection. Combined, the findings from this study demonstrate for the first time the efficacy of salivary Hst-5 in protecting host oral tissue against C. albicans infection, thereby affirming the therapeutic potential of this natural host peptide.