Interactions of antimicrobial peptide treated-Candida and Engineered Human Oral Mucosa

Objective: Our earlier research indicated that KSL-W, a synthetic decapeptide, exhibited potent fungicidal activity against various test species of Candida. The goal of this study was to understand the interactions between antimicrobial peptide KSL-W-treated Candida and the host response in the context of Candida pathogenesis. Methods: C. albicans was cultured in the presence of KSL-W at 12.5, 50 and 100 ug/ml for 24 h and used (106/cm2) to infect an engineered human oral mucosa (EHOM) tissue that has been produced using normal human oral epithelial cells and fibroblasts. At the end of each time point (12 and 24h), Candida adhesion to the tissues, and growth was evaluated. Host responses through cytokines (IL-1b, IL-6 and IL-8) and antimicrobial peptide (human b-defensin-HBD) expressions were investigated using ELISA and quantitative RT-PCR techniques. Results: We showed that, Candida that treated with KSL-W adhered significantly less to EHOM as compared to untreated Candida. Furthermore, KSL-W-treated Candida showed a significant growth reduction when put in contact with EHOM. The effect was both time- and dose-dependent. The ability of KSL-W to attenuate the virulence of Candida was confirmed by the extent of inflammatory response exhibited by the EHOM cells. Cytokine (IL-1b, IL-6 and IL-8) secretions were unchanged or decreased following tissue contact with KSL-W-treated Candida. The results suggest that the peptide-treated Candida has become less virulent as evidenced by the lack of host response (i.e., reduced production of inflammatory mediators) upon challenge. This was further confirmed by the expression profiles of endogenous antimicrobial peptides (HBD1, 2, 3 and 4) shown by gingival epithelial cells following EHOM contact with KSL-W-treated Candida. These effects were comparable to those obtained with Candida treated with amphotericin-B. Conclusion: All together, these results demonstrated that antimicrobial peptide KSL-W reduced Candida pathogenesis leading to the non-stimulation of the host innate immunity.