Abstract: This study aimed to explore the effect of gut microbiota disturbance on susceptibility to BVDV by establishing a mouse model of gut microbiota disturbance. The experiment was divided into two groups. Gut microbiota disturbance mice were treated with amphotericin-B, neomycin trisulfate salt hydrate, ampicillin, metronidazole, and vancomycin hydrochloride by gavage, while mice in control group were given an equal volume of physiological saline.After 13 consecutive days, fecal samples of mice were collected to extract bacterial DNA and 16S rRNA sequencing was performed to detect the changes in the diversity and abundance of gut microbiota in mice.The mice exploring the impact of gut microbiota disturbance on susceptibility to BVDV were divided into 2 groups. Mice in antibiotic treated and untreated groups were intraperitoneally injected with 10⁵ TCID₅₀ CP BVDV. The blood and duodenum of mice at day 7 of post-infection were collected, and viral loads were detected by qRT-PCR and Western blot. The pathological changes of duodenum were detected by hematoxylin and eosin staining (HE staining). The experiment of fecal microbiota transplantation (FMT) was divided into two groups. Mice in the experiment group were treated with FMT while mice in control group were given the same volume normal saline. Aimed to further verify the effect of restoring gut microbiota on BVDV infection. The results showed that antibiotic treatment significantly reduced the α-diversity of gut microbiota, Venn diagram analysis also showed that antibiotic treatment reduced the number of OTUs of gut microbiota. The β-diversity combined with the histogram analysis further showed that the composition of gut microbiota was significantly different between the antibiotic treated group and the untreated group. The relative abundance of Firmicutes and Bacteroidetes decreased significantly in the antibiotic treated group, while the relative abundance of Proteobacteria increased significantly. Exploring the susceptibility to BVDV showed that viral loads in blood and duodenum of mice with gut microbiota disturbance were significantly higher than that of mice with normal microbiota. The disturbance of gut microbiota increased the expression of BVDV E0 protein in duodenum of mice, and aggravated duodenal pathological damage were detected by Western blot and histopathological analysis. However, FMT treatment significantly reduced viral loads and improved duodenal pathological damage. The above results indicated that the antibiotic induced mouse model of gut microbiota disturbance was successfully constructed. On the basis of this model, it was further confirmed that the disturbance of gut microbiota increased the susceptibility to BVDV, and FMT supplementation showed the effect of inhibiting BVDV infection. These studies lay a foundation for developing probiotics for the prevention and control of BVDV infection and the screening of antiviral drugs.

Key words: bovine viral diarrhea virus, gut microbiota, mouse model, FMT