Expression kinetics of interferon and interferon-induced genes in Atlantic salmon (Salmo salar) following infection with infectious pancreatic necrosis virus and infectious salmon anaemia virus

Infectious pancreatic necrosis virus (IPNV) and infectious salmon anaemia virus (ISAV) are economically important pathogens of the salmonid aquaculture industry. Atlantic salmon were challenged by intraperitoneal injection (i.p.) with either virus followed by time-course sampling. Cohabiting fish in the IPNV challenge were also sampled. Kidney tissue was analysed using a TaqMan® real-time PCR assay to measure the expression of a range of host immune genes in relation to the endogenous control, elongation factor 1 alpha (ELF). Host genes measured included Mx, type I and type II interferon (IFN), γIFN induced protein (γIP), interleukin-1 beta (IL-1β) and tumour necrosis factor alpha (TNF-α). Viral levels were also measured. In i.p. injected fish, both viruses greatly induced expression of Mx, γIP, type I and type II IFN by day 6 post-infection, however only ISAV caused substantial mortality. Some differences between the expression kinetics produced by both viruses were noted. Infection with ISAV increased IL-1β expression following day 6, but no effect was seen in fish infected with IPNV. Neither virus induced TNF-α expression. This study confirms the presence of both type I and type II IFN responses and their induced genes in Atlantic salmon upon infection with an orthomyxovirus and a birnavirus.