Multiple passage of infectious salmon anaemia virus in rainbow trout, Oncorhynchus mykiss (Walbaum), did not induce increased virus load.
The infectious salmon anaemia virus (ISAV) has not been observed to cause natural disease in farmed rainbow trout, Onchorhynchus mykiss (Walbaum), but may cause high mortality in farmed Atlantic salmon, Salmo salar L. In this study, ISAV was passaged 10 times in succession by intraperitoneal injections of serum from previous passage into naïve rainbow trout. The serum viraemia was monitored by real-time qPCR. The rainbow trout in this study became infected but did not develop ISA. No clinical signs were observed in the rainbow trout in any passage, but replication of ISAV was detected from Day 4 post-infection (p.i.). Neither increased relative virus loads nor histopathological and immunohistochemical findings consistent with ISA were observed. However, the expression of interferon type I and Mx genes were slightly up-regulated in the hearts of some individual fish at day 17 p.i. Sequencing of all open reading frames in the ISAV genome of the 10th passage revealed two nucleotide mutations, one in segment 6 coding for the haemagglutinin-esterase (HE) and one in segment 1 coding for the basic polymerase 2 (PB2). The mutation in HE resulted in an amino acid substitution T/K(312) .
Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, Oslo, Norway.
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Olsen
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Braaen
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Falk
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Rimstad
D000595:Amino Acid Sequence; D000818:Animals; D005393:Fish Diseases / Q000276:immunology / Q000821:virology*; D019204:GTP-Binding Proteins / Q000235:genetics; D020869:Gene Expression Profiling; D007370:Interferon Type I / Q000235:genetics; D046829:Isavirus / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation; D064547:Myxovirus Resistance Proteins; D017686:Oncorhynchus mykiss / Q000276:immunology / Q000821:virology*; D009976:Orthomyxoviridae Infections / Q000276:immunology / Q000662:veterinary* / Q000821:virology; D016415:Sequence Alignment; D015854:Up-Regulation; D019562:Viral Load; D014779:Virus Replication / Q000502:physiology
D007370:Interferon Type I; D064547:Myxovirus Resistance Proteins; D019204:GTP-Binding Proteins