Alterations of Suckling Piglet Jejunal Microbiota Due to Infection With Porcine Epidemic Diarrhea Virus and Protection Against Infection by Lactobacillus salivarius

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.

Hypericum japonicum extract inhibited porcine epidemic diarrhea virus in vitro and in vivo

Porcine epidemic diarrhea virus (PEDV) infection causes lethal watery diarrhea and high mortality in neonatal piglets, leading to huge economic losses in the global swine industry. Currently, the existing commercial vaccines cannot fully control PEDV, so it is urgent to develop effective antiviral agents to complement vaccine therapy. In the present study, we investigated the antiviral effect of Hypericum japonicum extract (HJ) against PEDV in vivo and in vitro. In in vitro assays, HJ could directly inactivate PEDV strains; moreover, it inhibited the proliferation of PEDV strains in Vero or IPI-FX cells at its non-cytotoxic concentrations. Time of addition assays revealed that HJ mainly inhibited PEDV at the later stages of the viral life cycle. In in vivo, compared with the model group, HJ could reduce the viral titers in the intestines of infected piglets, and improve their intestinal pathological, indicating that HJ could protect the newborn piglets from highly pathogenic PEDV variant infection. Furthermore, this effect may be related to the fact that HJ can not only directly inhibit viruses, but also regulate the structure of intestinal microbiota. In conclusion, our results indicate that Hypericum japonicum could inhibit PEDV replication in vitro and in vivo and might possess the potential to develop as the anti-PEDV drug.

Difference analysis of intestinal microbiota and metabolites in piglets of different breeds exposed to porcine epidemic diarrhea virus infection

The gut microbial composition of the Luchuan (LC) piglet, one of China’s native breeds, has rarely been studied, especially when compared to other breeds. This study developed a porcine epidemic diarrhea virus (PEDV) infection model in LC and Largewhite (LW) piglets, and analyzed the patterns and differences of intestinal microbial communities and metabolites in piglets of these two breeds after infection. The diarrhea score, survival time, and distribution of viral antigens in the intestine of piglets infected with PEDV differed among breeds, with the jejunal immunohistochemistry score of LW piglets being significantly higher than that of LC piglets (P < 0.001). The results of 16S rRNA sequencing showed differences in microbial diversity and community composition in the intestine of piglets with different breeds between PEDV infection piglets and the healthy controls. There were differences in the species and number of dominant phyla and dominant genera in the same intestinal segment. The relative abundance of Shigella in the jejunum of LC piglets after PEDV infection was significantly lower than that of LW piglets (P < 0.05). The key microorganisms differed in the microbiota were Streptococcus alactolyticus, Roseburia faecis, Lactobacillus iners, Streptococcus equi, and Lactobacillus mucosae (P < 0.05). The non-targeted metabolite analysis revealed that intestinal metabolites showed great differences among the different breeds related to infection. Spearman correlation analysis was conducted to examine any links between the microbiota and metabolites. The metabolites in the intestine of different breeds related to infection were mainly involved in arginine biosynthesis, synaptic vesicle cycle, nicotinic acid and nicotinamide metabolism and mTOR signaling pathway, with significantly positive or negative correlations (P < 0.05) between the various microorganisms. This study provides a theoretical foundation for investigating the application of core microorganisms in the gut of piglets of different breeds in the digestive tracts of those infected with PEDV, and helps to tackle the antimicrobial resistance problem further.