Molecular Characteristics, Expression Analysis and Antiviral Activity Against RSIV of Red Sea Bream IRF3 and IRF7

Interferon regulatory factor (IRF) 3 and IRF7 are important innate immune-related genes that induce type I interferon (IFN). In this study, PmIRF3 and PmIRF7 were identified from red sea bream (Pagrus major) infected by red sea bream iridovirus (RSIV), and expression and functional analyses were performed. PmIRF3 and PmIRF7 consisted of 465 and 436 amino acids, respectively, and contained a well-conserved IRF domain, IRF3 domain, and serine-rich domain (SRD). PmIRF3 and PmIRF7 are ubiquitously expressed in the liver and gills in normal fish, and with a high expression being recorded in kidney and spleen during RSIV infection. In P. major fin cells (PMF cells), pAcGFP-PmIRF3 and pAcGFP-PmIRF7 were localized to the cytoplasm, and overexpression of PmIRF3 and PmIRF7 using the pcDNA3.1 vector induced type I IFN. In addition, in the experiment in vitro, PMF cells overexpressed with PmIRF3 or PmIRF7 exhibited antiviral activity against RSIV and significantly reduced viral genome copies and virus titer. Therefore, PmIRF3 and PmIRF7 may have antiviral activity through the induction of type I IFN against RSIV infection of red sea bream.