Molecular Characterization of Group II Interferon, IFNc, in Largemouth Bass (Micropterus salmoides) and Its Enhancement of Cell Viability Following Micropterus salmoides Rhabdovirus (MSRV) Infection

Interferons (IFNs) play vital roles in antiviral immunity, yet the functional diversity of type I IFNs in teleosts remains incompletely characterized. In this study, we identified and characterized a group II type I interferon, designated IFNc (MsIFNc), from largemouth bass (Micropterus salmoides). The cDNA sequence of MsIFNc is 660 bp in length, encoding a 184-amino-acid polypeptide containing a signal peptide and four conserved cysteines predicted to form two disulfide bonds. Phylogenetic analysis confirmed its classification within the teleost IFNc subgroup. Tissue expression profiling revealed constitutive MsIFNc transcription in all examined tissues, with the highest levels in the liver, intestine, and spleen. Moreover, MsIFNc expression was significantly upregulated in the spleen following polyinosinic–polycytidylic acid (polyI:C) stimulation. Recombinant MsIFNc (rMsIFNc) was successfully expressed in Pichia pastoris and significantly enhanced the viability of primary hepatocytes infected with Micropterus salmoides rhabdovirus (MSRV). These results demonstrate that IFNc is an important component of the immune response in largemouth bass, providing a basis for understanding the function of fish IFNc.