Cyprinid herpesvirus 2 (CyHV-2) ORF67 inhibits IFN expression by competitively obstructing STING phosphorylation

Cyprinid herpesvirus 2 (CyHV-2) caused hematopoietic necrosis in crucian carp (Carassius auratus) has resulted in huge economic losses to the carp aquaculture. Interferon (IFN) response serves as a crucial line of defense for fish against CyHV-2 infection; however, CyHV-2 frequently overcomes this defense, resulting in damage and even substantial mortality. The mechanism by which CyHV-2 evades the fish IFN antiviral response remains unclear. In this study, we chose the open reading frame 67 (ORF67) of CyHV-2 as the target of our research. Firstly, the results of Co-immunoprecipitation (Co-IP) assay and in vitro phosphorylation showed that the ORF67 inhibited the expression of IFN by binding to TBK1-A/B and competitively blocking STING-A/B phosphorylation. Then, we elaborated on the effect of ORF67 on the cell's antiviral function by cytopathic effect (CPE) and immunoblot analysis. In summary, this study has clarified the molecular mechanism of immune evasion by ORF67 through the inhibition of host IFN expression. This research enhances our understanding of the pathogenesis of CyHV-2 and provides theoretical references for the prevention and treatment of hematopoietic necrosis.