Atlantic salmon type I interferons: Protection against virus infection in vivo and function as adjuvants in a virus DNA vaccine.

Abstract

Fish farming has been considered the importance resource for supplying food for the global requirement. Norway by far is the country that produces the most salmon in the world, and virus disease is one of the major problems that causes the economic loss in fish farming. For combating the diseases, the vaccine has been developed. In Norway, traditional vaccines based on inactivated virus are available against IPN, PD, and ISA, but do not appear to give adequate protection. IPN and vaccine based on recombinant VP2 are the only commercial available subunit vaccine in Norway that provides high and long-lasting protection. There is thus a clear need to develop effective vaccines against these and other virus diseases of Atlantic salmon. To develop improved vaccines and other prophylactic methods, it is important to increase the understanding of the interaction of viruses with the immune system of Atlantic salmon. Three salmon interferon subtypes IFNa, IFNb and IFNc which all induce the expression of antiviral genes in salmon cells that provide antiviral activity against virus infection. Therefore, in the first part of our work, we have studied if the intramuscular injection of IFN-I expressed plasmid DNA can induce antiviral activity in salmon pre-smolt and provide protection against virus infection. Our work has shown that IFNc but not IFNb and IFNa plasmid induce a strong antiviral activity and protection against ISAV and SAV3. Besides, IFN-I plays an important role in modulating adaptive immune response in mammals, therefore, in the second part of our work, we have studied if type I IFNs might be used as adjuvants in fish DNA vaccines. We have chosen ISAV HE DNA vaccine as the model that co-injected with salmon IFN-I plasmid, and the results of our work show a strong adjuvant effect of all three interferons. Our result is the first time illustrated the adjuvant effect of IFN-I in fish that could be useful for vaccine development.