In vitro synergic antifungal effect of MUC7 12-mer with histatin-5 12-mer or miconazole.
OBJECTIVE
MUC7 12-mer (RKSYKCLHKRCR), a cationic peptide derived from human salivary MUC7 mucin, exhibits potent in vitro antifungal activity, as determined by killing assays in phosphate buffer. In this study we examined the MUC7 12-mer antifungal activity alone or in combination with other antifungal agents in LYM medium (modified RPMI 1640).


METHODS
Antifungal activities of MUC7 12-mer and other compounds against several fungal strains were first measured by MIC and minimum fungicidal concentration (MFC) tests using broth microdilution assay. The viability of Candida albicans and Cryptococcus neoformans were also determined by killing assays and time kinetics of peptide-mediated killing. Antifungal activities of MUC7 12-mer in combination with other compounds [histatin-5 (Hsn5) 12-mer: AKRHHGYKRKFH, amphotericin B or miconazole] against C. albicans and C. neoformans were determined by chequerboard assays and confirmed by killing assays. Toxicities of individual compounds were determined by haemolytic assays.


RESULTS
MICs and MFCs of MUC7 12-mer ranged from 3.13 to 6.25 mg/L for most of the strains tested, and were, in most cases, comparable to those of amphotericin B and miconazole (0.78-6.25 mg/L). ED(50) values of MUC7 12-mer and Hsn5 12-mer were 7.1 and 7.4 micro M (or 11.2 and 11.6 mg/L), respectively, for C. albicans; and 1.2 and 1.1 micro M (or 1.9 and 1.7 mg/L), respectively, for C. neoformans. The killing of C. albicans and C. neoformans was achieved after 30 and 10 min exposure to the peptides, respectively. Combinations of MUC7 12-mer and Hsn5 12-mer, and of MUC7 12-mer and miconazole have a synergic antifungal effect on C. neoformans, with a fractional inhibitory concentration index (FICI) of 0.37 and 0.25, respectively; and a slightly lower than synergic effect on C. albicans, with a FICI of 0.63 and 0.56, respectively. In addition, using human erythrocytes, the two salivary peptides showed low levels of haemolytic activity.


CONCLUSIONS
This study suggests that MUC7 12-mer and Hsn5 12-mer peptides may be suitable candidates for use in combination antifungal therapy.
Wei
Guo-Xian
GX
Department of Oral Biology, University at Buffalo, The State University of New York, Buffalo, NY 14214, USA.
Bobek
Libuse A
LA
D000935:Antifungal Agents / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects* / Q000254:growth & development; D003455:Cryptococcus neoformans / Q000187:drug effects* / Q000254:growth & development; D003470:Culture Media; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004912:Erythrocytes / Q000187:drug effects; D006461:Hemolysis / Q000187:drug effects; D054808:Histatins; D006801:Humans; D066298:In Vitro Techniques; D008825:Miconazole / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D009077:Mucins / Q000494:pharmacology*; D012471:Salivary Proteins and Peptides / Q000494:pharmacology*
D000935:Antifungal Agents; D003470:Culture Media; C068075:HTN3 protein, human; D054808:Histatins; C083238:MUC7 protein, human; D009077:Mucins; D012471:Salivary Proteins and Peptides; D008825:Miconazole