Probiotic Lactobacillus casei Expressing Porcine Antimicrobial Peptide PR39 Elevates Antibacterial Activity in the Gastrointestinal Tract

PR39, a 4.7-kDa proline-rich antimicrobial peptide, acts as a cationic host defense peptide. In addition to killing bacteria, PR39 mediates inflammatory reactions, including cell proliferation, migration, wound healing, and angiogenesis. Here, we examined the antibacterial effects of this peptide. The synthetic gene fragment PR39 was inserted into the secretory expression vector plasmid pPG:612 of Lactobacillus casei, yielding the recombinant strain pPG:612-PR39/L. casei 393. In vitro antibacterial tests showed that expression of the PR39 peptide in recombinant L. casei resulted in antibacterial activity against Escherichia coli and Salmonella, but had only minor antibacterial effects in Staphylococcus aureus. In addition, BALB/c mice fed the recombinant pPG:612-PR39/L. casei 393 grew better and had increased peripheral blood lymphocyte percentages, white blood cell numbers, and spleen indices compared with those of the control group. Scanning electron microscopy showed that jejunum and duodenum villus height, crypt depth, and the ratio of V/C in the intestinal villi also increased. Moreover, mice fed the recombinant strain showed significantly lower mortality rates than the control group when challenged with the enterotoxigenic E. coli K88+ (ETEC K88+). Thus, this recombinant expression system had beneficial characteristics of both Lactobacillus casei and PR39, supporting its potential as an animal feed additive.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author