Changes in microRNAs expression profile of olive flounder (Paralichthys olivaceus) in response to viral hemorrhagic septicemia virus (VHSV) infection

• Changes of microRNAs expression by VHSV infection in olive flounder were analyzed by NGS.
• A total of 372 conserved microRNAs and 47 candidate novel miRNAs were discovered.
• 63 miRNAs were differentially expressed during VHSV infection.
• Various biological pathways could be affected by VHSV through regulation of host miRNAs.

To know the effect of viral hemorrhagic septicemia virus (VHSV) infection on the cellular microRNA expression profile in olive flounder (Paralichthys olivaceus), fish were infected with VHSV, and cellular microRNAs expression was analyzed at 0 (control), 6, 12, 24, 48 and 72 h post-infection (h.p.i.) by the high-throughput sequencing. A total of 372 mature miRNAs were identified, and, among them, 63 miRNAs were differentially expressed during VHSV infection. The differentially expressed microRNAs number was greatly increased from 24 h.p.i. compared to the number at 6 and 12 h.p.i., suggesting that the alteration of microRNAs expression by VHSV infection may be related to the progression of VHSV disease. The target prediction analysis, the GO enrichment analysis, and the KEGG pathway analysis of the predicted target genes showed that various biological pathways could be affected by VHSV infection through the down-regulation or up-regulation of host miRNAs. The present results provide a basic information on the microRNAs related to VHSV infection in olive flounder. Considering broad effects of microRNAs on various biological pathways, data in this study can be used to interpret the mechanism of VHSV pathogenesis, which, vice versa, can be used to develop control measures against VHSV.