Histatin 5-Spermidine Conjugates Have Enhanced Fungicidal Activity and Efficacy as a Topical Therapeutic for Oral Candidiasis

Abstract

ABSTRACTOropharyngeal candidiasis (OPC) is caused by the opportunistic fungiCandida albicansand is prevalent in immunocompromised patients, individuals with dry mouth, or patients with prolonged antibiotic therapies that reduce oral commensal bacteria. Human salivary histatins, including histatin 5 (Hst 5), are small cationic proteins that are the major source of fungicidal activity of saliva. However, Hsts are rapidly degradedin vivo, limiting their usefulness as therapeutic agents despite their lack of toxicity. We constructed a conjugate peptide using spermidine (Spd) linked to the active fragment of Hst 5 (Hst 54–15), based upon our findings thatC. albicansspermidine transporters are required for Hst 5 uptake and fungicidal activity. We found that Hst 54–15-Spd was significantly more effective in killingC. albicansandCandida glabratathan Hst 5 alone in both planktonic and biofilm growth and that Hst 54–15-Spd retained high activity in both serum and saliva. Hst 54–15-Spd was not bactericidal against streptococcal oral commensal bacteria and had no hemolytic activity. We tested the effectiveness of Hst 54–15-Spdin vivoby topical application to tongue surfaces of immunocompromised mice with OPC. Mice treated with Hst 54–15-Spd had significant clearance of candidal tongue lesions macroscopically, which was confirmed by a 3- to 5-log fold reduction ofC. albicanscolonies recovered from tongue tissues. Hst 54–15-Spd conjugates are a new class of peptide-based drugs with high selectivity for fungi and potential as topical therapeutic agents for oral candidiasis.