RESUMEN
Infectious salmon anemia virus (ISAV) is classified in the genus Isavirus of the family Orthomyxoviridae. Although virulence variation of ISAV can be demonstrated experimentally in fish, virus strain identification is ambiguous because the correlates of pathogenicity and/or antigenicity of ISAV are not well defined. Thirteen ISAV isolates characterized for their ability to kill fish were used to search for markers of virulence on the virus surface glycoprotein genes; haemagglutinin-esterase (HE) and fusion (F) protein genes. A single amino acid change N(164)D in the putative globular head of the HE protein, and a deletion/insertion of Asunto(s)
Hemaglutininas Virales/fisiología
, Isavirus/genética
, Isavirus/patogenicidad
, Proteínas Virales de Fusión/fisiología
, Secuencias de Aminoácidos/genética
, Secuencias de Aminoácidos/fisiología
, Sustitución de Aminoácidos/genética
, Animales
, Secuencia de Bases
, Línea Celular
, Efecto Citopatogénico Viral/genética
, Evolución Molecular
, Enfermedades de los Peces/mortalidad
, Enfermedades de los Peces/virología
, Geografía
, Hemaglutininas Virales/genética
, Isavirus/clasificación
, Datos de Secuencia Molecular
, Oncorhynchus kisutch
, Oncorhynchus mykiss
, Infecciones por Orthomyxoviridae/mortalidad
, Infecciones por Orthomyxoviridae/veterinaria
, Infecciones por Orthomyxoviridae/virología
, Filogenia
, Salmo salar
, Análisis de Secuencia de ADN
, Eliminación de Secuencia
, Homología de Secuencia
, Proteínas Virales de Fusión/genética
, Virulencia
RESUMEN
The phenotypic correlates of pathogenicity for Infectious salmon anemia virus (ISAV) in salmonid fishes have not been thoroughly studied to date. In this study, a comparison was made of 13 different strains of ISAV, isolated from different geographical regions between 1997 and 2004, for their infectivity in three fish species [Atlantic salmon (Salmo salar), coho salmon (Oncorhynchus kisutch) and rainbow trout (Oncorhynchus mykiss)]. When the different virus isolates were used at an approximate inoculum dose of 10(6) TCID(50) in 0.2 ml per fish, it was found that the most virulent strains had an acute mortality phase in Atlantic salmon that started at 10-13 days post-inoculation and lasted for 9-15 days with a cumulative mortality of >/=90 %. These highly pathogenic strains also caused low mortality in rainbow trout, albeit later in infection. Viruses with a more delayed or protracted mortality phase resulting in cumulative mortalities of 50-89 % in Atlantic salmon were considered to be of intermediate pathogenicity and isolates with cumulative mortalities of =49 % were considered to be of low pathogenicity. On this basis, three of the ISAV isolates showed a high-, eight an intermediate- and two a low-pathogenicity phenotype in Atlantic salmon. Coho salmon were resistant to all ISAV isolates. These results confirmed that there is variation in pathogenicity among ISAV strains for Atlantic salmon and rainbow trout, and that other salmonid species such as coho salmon can carry highly pathogenic strains of ISAV without showing signs of disease. The identified pathogenicity phenotypes may aid in the identification of molecular markers of ISAV virulence.
Asunto(s)
Anemia/veterinaria , Enfermedades de los Peces/etiología , Enfermedades de los Peces/virología , Isavirus/patogenicidad , Infecciones por Orthomyxoviridae/veterinaria , Anemia/etiología , Anemia/virología , Animales , Isavirus/genética , Isavirus/aislamiento & purificación , Oncorhynchus kisutch/virología , Oncorhynchus mykiss/virología , Infecciones por Orthomyxoviridae/etiología , Infecciones por Orthomyxoviridae/virología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Salmo salar/virología , Especificidad de la Especie , VirulenciaRESUMEN
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.