Effect of viral RNA mimics and ISA virus infection on expression of key genes of the Atlantic salmon interferon system

Abstract

We have studied the innate immune responses of Atlantic salmon and how this responds to stimulation and infection by the aquatic orthomyxovirus Infectious salmon anemia virus (ISAV). This work has focused on the Type I interferon (IFN) system which is critically important in the vertebrate immune response against viral infections. As a part of this work we have studied the Atlantic salmon IFN regulatory factor 7 (IRF7). In mammals IRF7 is the major regulator of IFN transcription in response to viral infections, and our results show that the salmon homolog performs similar tasks. Furthermore, we have investigated the stimulatory effect of two synthetic ligands that induce the IFN system by mimicking viral infections in the cell and compared this to the immune response against ISAV. Our results indicate that both specialized immune cells and non-immune cells induce the IFN system in response to these treatments, but we also show that ISAV is able to interfere with the host` IFN response in order to successfully replicate. Finally, our studies show that the ISAV genome encodes two genes, S7ORF1 and S8ORF2, which is involved in antagonizing the IFN response during infections.