Rational Design and Optimization of MCh-AMP1: A Stable α-Helical Antifungal Peptide with Enhanced Activity Against...

Candida infections, particularly those caused by Candida albicans, are a growing threat to global health, exacerbated by increasing antifungal resistance. Traditional antifungal treatments are becoming increasingly ineffective due to resistance mechanisms, highlighting the need for innovative therapeutic solutions.

In this study, we engineered MCh-AMP1-A7, a derivative of the natural antimicrobial peptide MCh-AMP1, through rational design to enhance its antifungal activity, stability, and selectivity. By modifying the alpha-helical structure, amphipathy, and cationicity of the peptide, we significantly improved its antimicrobial potency.

MCh-AMP1-A7 showed a marked reduction in minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) compared with the parent peptide. Against C. albicans ATCC 10231, the MIC decreased from 16 μg/mL for MCh-AMP1 to 8 μg/mL for MCh-AMP1-A7. Similarly, for clinical isolates of C. glabrata and the reference strain C. krusei DSM 70079, MCh-AMP1-A7 showed a 2- to 4-fold reduction in MIC values, indicating increased potency. This peptide also showed remarkable stability over a wide range of temperature (10-70°C) and pH conditions (pH 2-12), and retained significant antifungal activity even at very high pH values, where the parent peptide would lose much of its potency. Furthermore, MCh-AMP1-A7 displayed an improved in vitro selectivity profile, with a higher lower-bound therapeutic index (>14.5) compared with MCh-AMP1 (>5.9), together with reduced hemolytic activity and lower cytotoxicity against human embryonic kidney cells (HEK293). Molecular docking and molecular dynamics simulations showed that MCh-AMP1-A7 interacts effectively with fungal membranes, with high affinity (ΔG = -8.8 kcal/mol), supporting a membrane-associated mechanism of action.

This study provides compelling evidence that MCh-AMP1-A7 is a promising next-generation antifungal agent capable of overcoming the limitations of conventional therapies. The potency, stability, and improved safety profile of the engineered peptide make it a promising candidate for further antifungal development.