In Vitro and In Vivo Evaluation of Bacillus Strains as Prophylactic Agents Against Porcine Epidemic Diarrhea Virus

Porcine epidemic diarrhea virus (PEDV), particularly the highly virulent G2b strains, has inflicted substantial economic losses on the global swine industry. This study evaluated the prophylactic effects of three <i>Bacillus</i> strains-<i>B. amyloliquefaciens</i> LN, <i>B. licheniformis</i> CK, and <i>B. velezensis</i> AC-against PEDV infection using in vitro and in vivo models. In vitro experiments with Vero cells demonstrated that <i>B. amyloliquefaciens</i> LN increased cell viability, reduced PEDV-N expression, and modulated proinflammatory cytokine responses. In vivo, piglets supplemented with <i>B. amyloliquefaciens</i> LN exhibited alleviated diarrhea symptoms, suppression of fecal viral RNA shedding to below the detection limit, and restoration of gut microbiota balance by increasing Bacteroidetes and reducing Proteobacteria abundance. Mechanistic studies indicated that the measured interferon (IFN)-related genes were not significantly influenced in this study, suggesting that the protective effects of <i>B. amyloliquefaciens</i> LN may involve the modulation of inflammatory responses and the inhibition of viral replication through reduced PEDV-N expression. This study illustrates the potential of using <i>B. amyloliquefaciens</i> LN as a feed additive to prevent PEDV infection.