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J Gen Virol. 2001 Dec;82(Pt 12):2869-2879. doi: 10.1099/0022-1317-82-12-2869.

Antigenic variation among isolates of infectious salmon anaemia virus correlates with genetic variation of the viral haemagglutinin gene.

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Department of Pathology and Microbiology1 and AVC Inc.2, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PEI, CanadaC1A 4P3.
Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada3.
Veterinary Pathology, Nova Scotia Department of Fisheries and Aquaculture, Truro, Nova Scotia, Canada4.
New Brunswick Department of Fisheries and Aquaculture, Fredericton, New Brunswick, Canada5.


Infectious salmon anaemia virus (ISAV), an orthomyxovirus-like virus, is an important fish pathogen in marine aquaculture. Virus neutralization of 24 ISAV isolates in the TO cell line using rabbit antisera to the whole virus and comparative sequence analysis of their haemagglutinin (HA) genes have allowed elaboration on the variation of ISAV isolates. The 24 viruses were neutralized to varying degrees, revealing two major antigenic groups, one American and one European. Sequence analysis of the HA gene also revealed two groups of viruses (genotypes) that correlated with the antigenic groupings. The two HA subtypes had nucleotide sequence identity of only < or =79.4% and amino acid sequence identity of < or =84.5% whereas, within each subtype, the sequence identities were 90.7% or higher. This grouping was also evident upon phylogenetic analysis, which revealed two distinct phylogenetic families. Between the two groups, the amino acid sequence was most variable in the C-terminal region and included deletions of 4-16 amino acids in all isolates relative to ISAV isolate RPC/NB-980 280-2. In order to view the relationships among these sequences and the HA sequences of the established orthomyxoviruses, a second phylogenetic tree was constructed which showed the ISAV sequences to be more closely related to sequences from Influenzavirus A and Influenzavirus B than to sequences from Influenzavirus C and Thogotovirus. The extensive deletions in the gene of European ISAV isolates lead us to speculate that the archetypal ISAV was probably of Canadian origin.

[Indexed for MEDLINE]

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