Expression differences of interferon regulatory factor 3 and non-specific cytotoxic cell receptor protein-1 in grass carp (Ctenopharyngodon idella) after challenges with two genotypes of grass carp reovirus, and analysis of antiviral signaling pathways

Grass carp reovirus (GCRV), with high genetic diversity, seriously affects grass carp farming. Meanwhile, interferon regulatory factor 3 (IRF3) and non-specific cytotoxic cell receptor protein-1 (NCCRP-1) play crucial roles in immunity system of fish. In this paper, we took IRF3 and NCCRP-1 as molecular markers in order to explore the differences in immune responses of grass carp infected with different GCRV strains, which is helpful in better understanding of the GCRV pathogenesity. Accordingly, we analyzed the expression differences of IRF3 and NCCRP-1 in grass carp after challenges with GCRV GD108 (genotype III) and GCRV 096 (genotype I) by qRT-PCR. We found IRF3 and NCCRP-1 was up-regulated in all tested tissues after challenges of GCRV GD108 and GCRV 096. However, the expression levels of IRF3 and NCCRP-1 depended on the GCRV strain, and the up-regulation changes were qualitatively similar but quantitatively different after challenges of GCRV GD108 and GCRV 096, that is, NCCRP-1 was up-regulated more, earlier, and more broadly than IRF3 after GCRV challenge. Besides, the NCCRP-1 was more rapidly up-regulated to a greater extent after challenges with GCRV 096 than GCRV GD108. In order to clarify whether the antiviral immune response and development of grass carp hemorrhage in grass carp differed depending on GCRV genotypes needs more investigation. Moreover, we speculated that the GCRV-induced signaling pathways in grass carp were enriched with measles- and influenza A-induced signaling pathways, and found 13 types of new genes in the GCRV-induced signaling pathway.