The Antimicrobial Peptide LJ-hep2 from Exerting Activities against Multiple Pathogenic Bacteria and Immune Protection In Vivo.

Hepcidin is widely present in many kinds of fish and is an important innate immune factor. A variety of HAMP2-type hepcidins have strong antimicrobial activity and immunomodulatory functions and are expected to be developed as substitutes for antibiotics. In this study, the antimicrobial activity of Hepc2 from Japanese seabass () (designated as LJ-hep2) was investigated using its recombinant precursor protein (rLJ-hep2) expressed in and a chemically synthesized mature peptide (LJ-hep2). The results showed that both rLJ-hep2 and synthetic LJ-hep2 displayed broad antimicrobial spectrum with potent activity against gram-negative and gram-positive bacteria, and fungi. Especially, LJ-hep2 had stronger antimicrobial activity and exhibited potent activity against several clinically isolated multidrug-resistant bacteria, including , , , and . Moreover, LJ-hep2 exerted rapid bactericidal kinetic (killed tested bacteria within 2 h), induced significant morphological changes and promoted agglutination of , and . The activity of LJ-hep2 against , and was stable and remained active when heated for 30 min. In addition, LJ-hep2 exhibited no cytotoxicity to the mammalian cell line HEK293T and fish cell lines (EPC and ZF4). In vivo study showed that LJ-hep2 could improve the survival rate of marine medaka () by about 40% under the challenge of , indicating its immunoprotective function. Taken together, both rLJ-hep2 and LJ-hep2 have good prospects to be used as potential antimicrobial agents in aquaculture and medicine in the future.