Isolation of Limosilactobacillus reuteri Strain with Anti-porcine Epidemic Diarrhea Virus from Swine Feces.

Porcine epidemic diarrhea virus (PEDV) causes severe diarrhea diseases in piglets, which has brought huge economic losses to the pig industry. As the dominant Lactobacillus species in the piglet intestine, the antiviral effect of Limosilactobacillus reuteri (L. reuteri) has been reported. Nine L. reuteri strains were isolated and identified from swine feces in this study. The CCK-8 assay examined the anti-PEDV potential of their cell-free supernatant (CFS). Among the nine L. reuteri isolates examined, LRC8 had a higher inhibition rate to PEDV than the other strains. Thus, the biological properties of the LRC8 strain, such as growth ability, acid production ability, acid and bile salt tolerance, and adhesion to IPEC-J2 cells, were evaluated. Besides, the anti-PEDV activity of LRC8-CFS (LRC8 metabolites, LRM) was assessed using plaque reduction assays, indirect immunofluorescence assays, RT-qPCR, and western blotting. The mRNA relative expression levels of inflammatory factors including IL-1β, IL-6, IL-8, MCP1, and TNF-α were determined by RT-qPCR. The results showed that the LRC8 strain grew well, was resistant to acid, tolerated bile salts, and adhered strongly to IPEC-J2 cells. In addition, treatment with its CFS (LRM) dramatically downregulated the mRNA expression levels of inflammatory cytokines, and in the Vero cell culture, prophylactic, therapeutic, competitive, and direct-inhibitory actions were seen against PEDV. Finally, we explored the anti-PEDV effects of the LRC8 strain in piglets and found that the LRC8 strain effectively relieved the clinical symptoms and intestinal damage of piglets infected by PEDV. To sum up, we found a L. reuteri strain with an anti-PEDV effect.