Fig. 6

IHNV infection leads to microbiota translocation and subsequently induces an antibacterial immune response. a Fluorescence in situ hybridization experiment to detect the bacteria in the Cor, BC, and FC paraffin-sections from 4 and 28 days infected and control trout. From left to right: Cor, BC, and FC. EP, epithelium; ST, stroma; LP, lamina propria. Bacteria were stained red with Cy5-EUB338 oligoprobe, while nuclei were stained blue with DAPI. White arrowheads indicate bacteria. Scale bars, 10 μm. b Counts of positive bacteria in the Cor, BC, and FC of the control group and IHNV-infected trout at 4 and 28 DPI (n = 9). One-way ANOVA test was used to evaluate the statistical differences. c qPCR analysis of anti-bacteria genes in the Cor, BC, and FC of control and IHNV-infected trout OM at 4 and 28 DPI. Gene expression levels in IHNV-infected trout were normalized to those in the control group, which were set as 1 (n = 9). Statistical differences were evaluated by unpaired Student’s t test. Data are presented as mean ± SEM of three biological duplicates. *p < 0.05, **p < 0.01, ***p < 0.001