The porcine-derived compound Bacillus alleviates piglet infection with porcine epidemic diarrhea virus by reshaping the intestinal barrier and microbial balance.

Porcine epidemic diarrhea virus (PEDV) causes severe intestinal injury and high mortality in suckling piglets, resulting in massive economic losses worldwide. Due to the continuous emergence of variant strains, traditional vaccines cannot provide complete protection. Bacillus-based probiotics have become promising alternative agents due to their safety, stability, and multi-functional biological activities. This study aimed to investigate the protective effects and underlying mechanisms of porcine-derived compound Bacillus against PEDV infection in vitro and in vivo. In IPEC-J2 cells, culture supernatant of porcine-derived compound Bacillus significantly inhibited PEDV replication, upregulated antiviral proteins (ISG15, PKR, OAS1), and modulated cytokine secretion by increasing anti-inflammatory IL-4 and decreasing pro-inflammatory TNF-α. In PEDV-challenged piglets, oral administration of porcine-derived compound Bacillus effectively alleviated clinical symptoms, reduced diarrhea scores and mortality, decreased viral shedding and tissue viral load, repaired jejunal mucosal structure, and restored intestinal barrier integrity by upregulating tight junction proteins (Claudin-1, Occludin, ZO-1). Meanwhile, compound Bacillus enhanced intestinal IgA levels and reshaped gut microbial homeostasis disrupted by PEDV infection. Collectively, porcine-derived compound Bacillus protects piglets against PEDV through synergistic mechanisms including direct antiviral activity, immune regulation, intestinal barrier reinforcement, and microbiota modulation. This study provides a scientific basis for developing porcine-derived compound Bacillus as a green biological agent for PEDV control.