Functional and transcriptome analyses identify CMPK2 as a potential antiviral factor against NNV in Siniperca chuatsi.

Nervous necrosis virus (NNV) is a major viral pathogen that causes viral nervous necrosis in a wide range of fish species and poses a serious threat to global aquaculture. However, the antiviral responses of mandarin fish (Siniperca chuatsi) to NNV infection remain poorly understood. In this study, we investigated host antiviral responses using Chinese perch brain (CPB) cell line and in vivo infection models. Transcriptome sequencing of red-spotted grouper nervous necrosis virus (RGNNV)-infected CPB cells revealed extensive transcriptional reprogramming, with numerous interferon-stimulated genes (ISGs) significantly upregulated. Comparative transcriptomic analysis across multiple teleost species identified a conserved set of ISGs induced during RGNNV infection, including CMPK2, RSAD2, DHX58, IRF3, and EPSTI1. Among these genes, CMPK2 showed strong induction in both infected CPB cells and mandarin fish brain tissues. Functional assays further demonstrated that CMPK2 overexpression significantly inhibited RGNNV replication in CPB cells and was accompanied by increased expression of several interferon-related genes. These findings provide the first functional evidence that CMPK2 restricts RGNNV infection in S. chuatsi. Our study highlights a conserved interferon-responsive antiviral module in teleost fish and identifies CMPK2 as a potential antiviral effector involved in host defense against RGNNV infection.