Fig. 1: Differential abundance of Prevotella following H9N2 infection.

a Establishment of H9N2 infection model; H9N2^H, 10^6.5 EID₅₀, n = 5; H9N2^M, 10^5.5 EID₅₀, n = 5; H9N2^L, 10^4.5 EID₅₀, n = 5; NC, n = 5. b Survival rates of mice across different groups post-H9N2 infection. c Body weight loss percentage in different groups following H9N2 infection. d Viral load determination in lung tissue by TCID₅₀ assay using MDCK cells; n = 3/group. e Comparison of histopathological changes; images taken at 100× and 200× magnifications. f Histopathological scoring of lung tissues; n = 3/group. g IL-6, TNF-α, and IL-1β levels in serum and lung tissue; n = 3/group. h Immunofluorescence analysis of lung tissue using H9N2-NA-FITC and DAPI; images taken at 200× and 400× magnifications. i Analysis of mean fluorescence intensity of H9N2-NA; n = 3/group. j Relative mRNA expression of occludin and ZO-1 in lung tissue; n = 3/group. k Analysis of alpha diversity of intestinal microbiota; Shannon, Chao1, Observed species, and Simpson. l 16S rRNA analysis of fecal samples shows bacterial genera’s relative abundance across groups; n = 3/group. m Correlation analysis between dominant bacterial genera and infection-related parameters, calculated using Pearson correlation coefficient. Samples for (d–m) were collected on day 6 after H9N2 infection. The data in (b–j) are representative of three independent experiments, yielding an identical pattern of results. Results are shown as means ± SD, with statistical significance determined by one-way ANOVA for three and four groups. *P < 0.05; **P < 0.01; ***P < 0.01; ****P < 0.0001.