Identification and functional characterization of interferon c (IFNc) in orange-spotted grouper (Epinephelus coioides) involved in antiviral response to SGIV and RGNNV infections.

The orange-spotted grouper (Epinephelus coioides) is highly susceptible to viral pathogens such as Singapore grouper iridovirus (SGIV) and red-spotted grouper nervous necrosis virus (RGNNV), resulting in significant economic losses in aquaculture. Type I interferons (IFNs) are pivotal antiviral cytokines in vertebrates, but their functions, particularly their antiviral effects against SGIV and RGNNV infections, remain incompletely understood. Here, we cloned and characterized the orange-spotted grouper ifnc gene (named Ec-ifnc), which encodes a 188 amino acids protein and clusters into a distinct teleost IFNc clade. Ec-ifnc was constitutively expressed across organs/tissues and was significantly upregulated following SGIV, RGNNV, or poly(I:C) stimulation. Functional assays demonstrated that treatment of recombinant Ec-IFNc in grouper spleen (GS) cells activated JAK-STAT signaling by promoting phosphorylation of STAT1a and STAT2. Consequently, Ec-IFNc effectively led to robust induction of interferon-stimulated genes (ISGs) and inhibited viral replication in SGIV- and RGNNV-infected cells. These findings suggested that orange-spotted grouper IFNc plays a critical role in host antiviral defense, and thus provides a clue for systematically elucidating the regulatory networks of the antiviral response in perciform fishes.