Antiviral activity of salmonid gamma interferon against infectious pancreatic necrosis virus and salmonid alphavirus and its dependency on type I interferon

Baojian Sun, Ingrid Skjaeveland, Tina Svingerud, Jun Zou, Jorunn Jorgensen, Borre Robertsen

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We investigated the antiviral activity and gene induction properties of interferon gamma (IFN-gamma) compared to type I IFN (IFNa1) in Atlantic salmon. IFN-gamma protected salmon cells against infectious pancreatic necrosis virus (IPNV)-induced cytopathic effect (CPE), reduced virus titers, and inhibited the synthesis of the viral structural protein VP3. Moreover, IFN-gamma showed potent antiviral activity against salmonid alphavirus 3 (SAV3) measured as a reduction in virus nsP1 transcripts. IFN-gamma (a type II IFN) had less specific antiviral activity against IPNV than IFNa1, showing a half-maximal effective concentration of 1.6 ng/ml versus 31 pg/ml determined in the CPE reduction assay. Compared to IFNa1, IFN-gamma was a more effective inducer of the antiviral protein GBP, several interferon regulatory transcription factors (IRFs), and the chemokine IP-10. The antiviral activity of IFN-gamma may also in part be ascribed to upregulation of Mx, ISG15, and viperin. These are typical type I IFN-induced genes in mammals and were also more strongly induced by IFNa1 than by IFN-gamma in salmon cells. Fish and mammalian IFN-gamma thus show strikingly similar gene induction properties. Interestingly, the antiviral activity of IFN-gamma against IPNV and SAV3 and its ability to induce Mx and ISG15 markedly decreased in the presence of neutralizing antiserum against IFNa1. In contrast, antiIFNa1 had no effect on the induction of IRF-1 and IP-10 by IFN-gamma. This suggests that the antiviral activity of IFN-gamma is partially dependent on IFNa induction. However, because antiIFNa1 could not abolish the IFN-gamma-mediated induction of Mx and ISG15 completely, IFN-gamma may possibly also induce such genes directly.

Original languageEnglish
Pages (from-to)9188-9198
Number of pages11
JournalJournal of Virology
Issue number17
Publication statusPublished - Sep 2011


  • double-stranded-RNA
  • trout oncorhynchus-mykiss
  • Atlantic salmon
  • anemia-virus
  • IFN-gamma
  • expression analysis
  • binding protein
  • teleost fish
  • MX proteins
  • kinase PKR

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