DISCLOSING AN IMPORTANT DEFENSE MECHANISM AGAINST VHSV IN FISH

VHSV (Viral hemorrhagic septicemia virus)  is a deadly fish virus, which causes devastating consequences in aquaculture. Even though interferon stimulated genes were suspected  for antiviral activities against VHSV , their  detailed mechanisms and pathway s  were  not described. Korean black rockfish ( Sebastes schlegelii) was used for this study, as it's an important species in offshore aquaculture in Korea . Interferon stimulated gene ,  viperin was identified in rockfish transcriptomic database. In silico analysis was performed to characterize the sequences  and  the domains that may responsible for  the suggested antiviral activities . Expression was analyzed against poly I:C by qPCR. Viperin was cloned and over expressed in FHM cells . After infection, a VHSV gene transcription was analyzed. VHSV replication was determined by a cell viability assay as well as  by TCID₅₀ method.

Bioinformatics analysis revealed availability of SAM binding motif "CNYKCGFC" . In vivo transcription analysis revealed the substantial upregulation of viperin with the presence of double standard RNA-analogue; poly I:C. Over expression of the viperin was significantly down regulating the VHSV gene expression. And the TCID₅₀ values for VHSV were significantly low in the viperin overexpressed FHM cells.

According to the results, it's obvious that viperin is a radical SAM protein which can reduce viral replication and the transcription. Viperin may strongly transcribe with the presence of viral RNA in cytosol. Previous studies suggested that VHSV  transcription and  replication is solely carried out by the viral RNA dependent RNA polymerase (RdRp). With these results, we can sugg est that  viperin inhibition of RdRp leading to strong antiviral activity against VHSV.