Genomewide Analysis and Biological Characterization of Cathelicidins with Potent Antimicrobial Activity and Low Cytotoxicity from Three Bat Species

Abstract

Cathelicidins are potent antimicrobial peptides with broad spectrum antimicrobial activity in many vertebrates and an important component of the innate immune system. However, our understanding of the genetic variations and biological characteristics of bat cathelicidins is limited. In this study, we performed genome-level analysis of the antimicrobial peptide cathelicidins from seven bat species in the six families, listed 19 cathelicidin-like sequences, and showed that the number of functional cathelicidin genes differed among bat species. Based on the identified biochemical characteristics of bat cathelicidins, three cathelicidins, HA-CATH (from Hipposideros armiger), ML-CATH (from Myotis lucifugus), and PD-CATH (from Phyllostomus discolor), with clear antimicrobial signatures were chemically synthesized and evaluated antimicrobial activity. HA-CATH showed narrow-spectrum antibacterial activity against a panel of 12 reference bacteria, comprising 6 Gram-negative and 6 Gram-positive strains. However, ML-CATH and PD-CATH showed potent antibacterial activity against a broad spectrum of Gram-negative and Gram-positive bacteria with minimum inhibitory concentration (MIC) of 1 and 3 μg/mL, respectively, against Staphylococcus aureus. ML-CATH and PD-CATH also showed antifungal activities against Candida albicans and Cryptococcus cuniculi with MIC of 5 to 40 μg/mL, respectively, and 80% inhibition of the metabolism of Mucor hiemalis hyphae at 80 μg/mL, while displaying minimal cytotoxicity to HaCaT cells. Taken together, although the spectrum and efficacy of bat cathelicidins were species-dependent, the antimicrobial activity of ML-CATH and PD-CATH was comparable to that of other highly active cathelicidins in vertebrates while having negligible cytotoxicity to mammalian cells. ML-CATH and PD-CATH can be exploited as promising candidates for the development of antimicrobial therapeutics.

Effective Healing of Staphylococcus aureus-Infected Wounds in Pig Cathelicidin Protegrin-1-Overexpressing Transgenic Mice

“…The plates were incubated for 6 h at 37 • C with shaking. The cell viability count was determined using a Microbial Viability Kit-WST, according to the manufacturer's protocol (M439, Dojindo, Kumamoto, Japan) and as described previously [56]. Coloring reagent (10 µL) was then added to the wells and incubated for 2 h. The absorbance was read at 450 nm using a spectrophotometer (xMark™ spectrophotometer, Bio-Rad, Hercules, CA, USA).…”

The evolution of antimicrobial peptides in Chiroptera

“…An emerging consensus posits immune tolerance as a widespread evolutionary trait acquired by chiropterans, but most studies have focused on the adaptive immune response and its implications in the inflammatory response ( 33 , 34 ). Despite its relevance in the defense against pathogens, studies pertaining to the evolution of the innate immune system and AMPs, specifically, are scarce ( 25 , 35 ). AMPs are key actors in the innate response, yet rampant loss has been previously reported in bats ( 34 ).…”