Type I interferons, as a class of multipotent cytokines, play a key role in host antiviral immune responses. In this study, a type I IFN coding gene of gibel carp, Carassius auratus gibelio, CagIFNa was cloned and sequenced. The full-length cDNA sequence of CagIFNa consists of 724 nucleotides that encode a predicted protein of 183 amino acids. CagIFNa has two highly conserved cysteine residues in the deduced protein, which is mostly conserved in the fish group I type I IFNs. CagIFNa was identified as a member of the IFNa subgroup of group I type I IFNs by phylogenetic analysis. CagIFNa transcripts were detected in all investigated tissues with higher levels in the liver, intestine, spleen and head kidney of gibel carp. Following injection with Cyprinid herpesvirus 2 (CyHV-2), CagIFNa gene expression was significantly inhibited in the spleen but delayed and then increased in head kidneys. Similarly, while CagIFNa expression was rapidly induced in gibel carp brain (GiCB) cells by poly I:C stimulation and its high induction level was delayed following CyHV-2 infection. CagIFNa overexpression in GiCB cells drastically reduced virus CPE and titer. Furthermore, several genes associated with type I IFN signaling pathway including IRF3, IRF7, IRF9, STAT1, Mx1 and PKR were induced in GiCB cells overexpressing CagIFNa upon CyHV-2 infection. These results show that CagIFNa plays a role in antiviral immune system in gibel carp.
Keywords: Antiviral activity; Carassius aurates gibelio; CyHV-2; Gibel carp; Immune response; Type I IFN.
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