Rational Design of Novel Brevinin Analogues with Broad Antimicrobial Spectrum and Less Cytotoxicity

Antimicrobial peptides (AMPs) are promising therapeutic alternatives to conventional antibiotics for the treatment of drug-resistant bacterial infections. However, the application of AMPs is limited because of moderate antimicrobial activity, high toxicity and high manufacturing costs. Conformation, net charge and amphipathicity are considered key factors in AMPs. In order to generate short AMPs with enhanced therapeutic efficacy, six peptides were designed based on the active motifs of natural AMPs followed by evaluating their biological activity, stability and cytotoxicity. Brevinin-OSd, OSe and OSf exhibited broad-spectrum antibacterial effects, especially OSf, which presented the highest therapeutic index for the tested bacteria. Also, these peptides displayed good stability. The results from CLSM, SEM and TEM studies, indicated that brevinin-OS, OSd, OSe and OSf possessed rapid bactericidal ability by disturbing membrane permeability and causing release of cytoplasm. In addition, OSd, OSe and OSf dramatically decreased the mortality of MRSA acutely-infected waxworms. Taken together, these data suggested that a balance between positive charge, degrees of α-helicity and hydrophobicity, is necessary for maintaining antimicrobial activity, and these data successfully contributed to the design of short AMPs with significant bactericidal activity and cell selectivity.