title: Persistent infections with infectious pancreatic necrosis virus (IPNV) of different virulence in Atlantic salmon, Salmo salar L.
abstract: Infectious pancreatic necrosis virus (IPNV) is a prevalent pathogen in fish worldwide. The virus causes substantial mortality in Atlantic salmon juveniles and smolts when transferred to sea water and persistent infection in surviving fish after disease outbreaks. Here, we have investigated the occurrence of the virus as well as the innate immune marker Mx in the head kidney (HK) of Atlantic salmon throughout an experimental challenge covering both a fresh and a seawater phase. The fish were challenged with a high (HV) and low virulence (LV) IPNV. Both isolates caused mortality due to reactivation of the virus after transfer to sea water. In the freshwater phase, higher levels of virus transcripts were detected in the HK of fish infected with LV IPNV compared to HV, suggesting that the HV isolate is able to limit its own replication to a level where the innate immune system is not alerted. Further, ex vivoHK leucocytes derived from fish infected with the two isolates were stimulated with CpG DNA. Significantly, higher IFN levels were found in the LV compared to the HV group in the freshwater phase. This suggests that the viruses attenuate the antiviral host immune response at different levels which may contribute to the observed differences in disease outcome.
authors.affiliation: Nofima, Tromsø, Norway.
authors.forename: K
authors.initials: K
authors.lastname: Julin
authors.affiliation: Nofima, Tromsø, Norway.
authors.forename: L-H
authors.initials: LH
authors.lastname: Johansen
authors.affiliation: Nofima, Tromsø, Norway.
authors.forename: A-I
authors.initials: AI
authors.lastname: Sommer
authors.affiliation: Norwegian College of Fisheries Science, UiT The Arctic University of Norway, Tromsø, Norway.
authors.forename: J B
authors.initials: JB
authors.lastname: Jørgensen
mesh_terms: D000818:Animals; D018175:Birnaviridae Infections / Q000382:microbiology / Q000401:mortality / Q000662:veterinary*; D005393:Fish Diseases / Q000382:microbiology* / Q000401:mortality; D054884:Host-Pathogen Interactions / Q000276:immunology*; D018061:Infectious pancreatic necrosis virus / Q000472:pathogenicity*; D008969:Molecular Sequence Data; D064547:Myxovirus Resistance Proteins / Q000378:metabolism; D020317:Salmo salar / Q000382:microbiology*
chemical_list: D064547:Myxovirus Resistance Proteins
keywords: Mx; infectious pancreatic necrosis virus; innate immunity; persistence; salmon; virulence