title: Evolutionary mechanisms involved in the virulence of infectious salmon anaemia virus (ISAV), a piscine orthomyxovirus.
abstract: Infectious salmon anaemia virus (ISAV) is an orthomyxovirus causing a multisystemic, emerging disease in Atlantic salmon. Here we present, for the first time, detailed sequence analyses of the full-genome sequence of a presumed avirulent isolate displaying a full-length hemagglutinin-esterase (HE) gene (HPR0), and compare this with full-genome sequences of 11 Norwegian ISAV isolates from clinically diseased fish. These analyses revealed the presence of a virulence marker right upstream of the putative cleavage site R267 in the fusion (F) protein, suggesting a Q266-->L266 substitution to be a prerequisite for virulence. To gain virulence in isolates lacking this substitution, a sequence insertion near the cleavage site seems to be required. This strongly suggests the involvement of a protease recognition pattern at the cleavage site of the fusion protein as a determinant of virulence, as seen in highly pathogenic influenza A virus H5 or H7 and the paramyxovirus Newcastle disease virus.
authors.affiliation: Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, P.O. Box 8146 Dep., N-0033 Oslo, Norway. turhan.markussen@veths.no
authors.forename: Turhan
authors.initials: T
authors.lastname: Markussen
authors.forename: Christine Monceyron
authors.initials: CM
authors.lastname: Jonassen
authors.forename: Sanela
authors.initials: S
authors.lastname: Numanovic
authors.forename: Stine
authors.initials: S
authors.lastname: Braaen
authors.forename: Monika
authors.initials: M
authors.lastname: Hjortaas
authors.forename: Hanne
authors.initials: H
authors.lastname: Nilsen
authors.forename: Siri
authors.initials: S
authors.lastname: Mjaaland
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019143:Evolution, Molecular; D005393:Fish Diseases / Q000821:virology*; D005838:Genotype; D006389:Hemagglutinins, Viral / Q000235:genetics*; D046829:Isavirus / Q000235:genetics* / Q000472:pathogenicity*; D008969:Molecular Sequence Data; D009664:Norway; D009976:Orthomyxoviridae Infections / Q000662:veterinary* / Q000821:virology; D010802:Phylogeny; D016865:Reassortant Viruses; D011995:Recombination, Genetic; D020317:Salmo salar / Q000821:virology*; D017422:Sequence Analysis, DNA; D014760:Viral Fusion Proteins / Q000235:genetics*; D014774:Virulence / Q000235:genetics
chemical_list: D006389:Hemagglutinins, Viral; D014760:Viral Fusion Proteins; C060814:hemagglutinin esterase