miRNAs are small non-coding RNA that instrumental in host immune response to pathogen infection. However, studies on the involvement of miRNAs in rainbow trout ( Oncorhynchus mykiss) ) antiviral response are still lacking. In this study, miRNA profiles of 48 hpi (T48SKs) compared to control (C48SKs), novel-m0065-3p and interferon regulatory factor 7 ( IRF7 ) expression, and novel-m0065-3p-IRF7 IRF7 functions were examined in rainbow trout skin following infectious hematopoietic necrosis virus (IHNV) challenge through RNA-seq, qRT-PCR, and over- expression and inhibition assays. Transcriptome analysis identified 23 up-regulated and 25 down-regulated differentially expressed miRNAs (DEMs). Enrichment analysis revealed that target genes were enriched in MAPK, RIG-I-like receptor, and Toll-like receptor signaling pathways. The DEMs (miR-205-z, novel-m0065-3p, novel-m0215-5p, novel-m0384-5p, and novel-m0397-3p) were identified, and targeted key immune-related genes. Expression patterns suggested that novel-m0065-3p and IRF7 were potential regulators in antiviral immune responses of rainbow trout. Functional analysis revealed that the overexpression of novel-m0065-3p reduced significantly IRF7 expression in liver cells, which was attenuated by the introduction of IRF7 , , whereas the opposite result was obtained by silencing novel-m0065-3p. Overexpressed novel-m0065-3p promoted liver cell proliferation and inhibited apoptosis, and co-transfection of IRF7 attenuated the effect of novel- m0065-3p. Furthermore, IRF7 overexpression inhibited significantly IHNV replication. In vivo , , the injection of agomiR-m0065-3p and antagomiR-m0065-3p changed significantly the expression of IRF7 and downstream genes. This study provided valuable information for drug-targeted diseases research and directed breeding efforts.
