The role of interferon in immunity against virus infection of Atlantic salmon

Upon virus infection, host cells recognize virus RNA by various sensors, which results in synthesis and secretion of IFN. Binding of IFN to non-infected host cells starts another signalling process, which leads to synthesis of multiple antiviral proteins. The host cells thus become protected against further viral infection.

Over the last 15 years, our group has characterized the IFNs of Atlantic salmon and are studying their function in innate and adaptive immune responses against virus. Salmon possesses a cluster of at least 11 IFN genes encoding three different IFN subtypes, IFNa, IFNb and IFNc, which are quite different in sequence and are expressed differently in various organs and cells. All three IFNs show antiviral activity in vitro, but only IFNb and IFNc induce antiviral genes systemically in the fish. Surprisingly, intramuscularly injection of salmon with a plasmid encoding IFNc led to protection of the fish against ISA-virus infection for at least 8 weeks.

Another important discovery was that injection of plasmids encoding IFNa, IFNb or IFNc potently increased the protective effect of a DNA vaccine against ISA-virus. This is the “proof of concept” that IFNs stimulate adaptive immunity in fish and thus function as adjuvants in vaccines. We are currently studying the adjuvant effects of IFNs in vaccines against other salmon viruses.

Funksjonen til IFN i forsvar mot virusinfeksjon.	Chia-Jung Chang vaksinerer presmolt med plasmider. Foto Børre Robertsen.	IFNa i gjeller hos laks etter stimulering med virus lignende RNA. Foto Terese Solstad.