Antifungal Spectrum and Fungicidal Mechanism of an N-Terminal Peptide of Bovine Lactoferrin

The antifungal spectrum and fungicidal mechanism of an N-terminal peptide of bovine lactoferrin (lactoferricin B), an antimicrobial peptide produced by gastric pepsin digestion of bovine lactoferrin, were investigated. The susceptibility of pathogenic yeasts and dermatophytes to the peptide varied in a species-dependent and strain-dependent manner. Dematiaceous fungi and dimorphic fungi were susceptible to the peptide (range of MIC values: 0.63 to 10μg/mL). In the case of nonpigmented hyphomycetes and zygomycetes, most strains exhibited resistance to the peptide (MIC:>80XYSμg/ mL). This peptide killed Candida albicans dose dependently without inducing a change in cell wall stability against osmotic stress. The peptide at 10μg/ml immediately induced the release of K⁺ from C. albicans cells and pH increases in cell suspensions. These pharmacological activities were more potent than those for miconazole nitrate, a well-known antifungal agent that interferes with membrane synthesis and function. These in vitro findings suggest that the lactoferrin oligopeptide has potent membrane disrupting activity against this yeast and suggests that in vivo LF-B studies would be useful to further understand host defenses and to develop improved therapeutic agents against yeast infections.