Porcine β-defensin 5 (pBD-5) exhibits potential immunomodulatory effects in porcine gut epithelial cells, B-cells, and alveolar macrophages

Antimicrobial resistance (AMR) is a global concern. β-defensins are known to possess antimicrobial and immunomodulatory properties and are being explored as potential tools to help mitigate AMR. This study investigated the effects of a linear porcine β-defensin 5 (pBD-5) on cell viability, mitochondrial activity, and gene expression in porcine B-cells, alveolar macrophages, and jejunal and colonic epithelial cells. Cells were exposed to pBD-5 for 1 and 24 hours. Additionally, the direct antimicrobial activity of pBD-5 against enterotoxigenic Escherichia coli (ETEC) F4 was assessed, as well as its impact on B-cell survival following ETEC F4 challenge. LDH release assays indicated reduced cell damage in B-cells, macrophages, and colonic epithelial cells after 24 hours. An increase in mitochondrial activity was observed in B-cells at concentrations ≥200 µM ( P <0.001). Exposure to pBD-5 was associated with reduced TNF-α mRNA expression in B-cells and alveolar macrophages and increased ZO-1 gene expression in intestinal epithelial cells ( P <0.05). However, the antimicrobial effect of pBD-5 was only evident at 80,000 µM ( P =0.0004), a concentration unlikely to be physiologically relevant. No statistically significant difference in B-cell survival was observed following ETEC F4 challenge in the presence of pBD-5 ( P =0.1656). These findings indicate that linear pBD-5 has limited direct antimicrobial activity against ETEC F4. However, pBD-5 modulated the expression of genes associated with epithelial barrier function and immune responses. Further studies are needed to confirm these effects and determine their biological relevance in vivo .