Discovery and Characterization of a Potent Antifungal Peptide through One-Bead, One-Compound Combinatorial Library Screening

Abstract

This work describes the discovery of a bead-bound membrane-active peptide (MAP), LBF127, that selectively binds fungal giant unilamellar vesicles (GUVs) over mammalian GUVs. LBF127 was re-synthesized in solution form and demonstrated to have antifungal activity with limited hemolytic activity and cytotoxicity against mammalian cells. Through systematic structure-activity relationship studies, including N- and C-terminal truncation, alanine-walk, and d-amino acid substitution, an optimized peptide, K-oLBF127, with higher potency, less hemolytic activity, and cytotoxicity emerged. Compared to the parent peptide, K-oLBF127 is shorter by three amino acids and has a lysine at the N-terminus to confer an additional positive charge. K-oLBF127 was found to have improved selectivity toward the fungal membrane over mammalian membranes by 2-fold compared to LBF127. Further characterizations revealed that, while K-oLBF127 exhibits a spectrum of antifungal activity similar to that of the original peptide, it has lower hemolytic activity and cytotoxicity against mammalian cells. Mice infected with Cryptococcus neoformans and treated with K-oLBF127 (16 mg/kg) for 48 h had significantly lower lung fungal burden compared to untreated animals, consistent with K-oLBF127 being active in vivo. Our study demonstrates the success of the one-bead, one-compound high-throughput strategy and sequential screening at identifying MAPs with strong antifungal activities.

Keywords: OBOC combinatorial library; antifungal activity; giant unilamellar vesicles; membrane active peptide.