Aquatic birnaviruses, such as infectious pancreatic necrosis virus (IPNV), cause serious diseases in a variety of fish species used worldwide in aquaculture and have also been isolated from a variety of healthy fish and shellfish species. These viruses exhibit a high degree of antigenic heterogeneity and variation in biological properties such as pathogenicity, host range, and temperature of replication. To better understand genetic and biological diversity among these viruses, the nucleotide and deduced amino acid sequences were determined from cDNA of the large open reading frame (ORF) of genome segment A of the 9 type strains of Serogroup A and 4 other representative strains of Serotype A1, the predominant serotype in the United States. In addition, nucleotide and deduced amino acid sequences were determined for the VP2 coding region of a variety of isolates representing 5 of the 9 serotypes. VP2 is the major outer capsid protein of aquatic birnaviruses. RT-PCR was used to amplify a 2904 bp cDNA fragment including all but a few bp of the large ORF of genome segment A or a 1611 bp fragment representing the entire VP2 coding region. Nucleotide and deduced amino acid sequences were determined from the PCR products. Pairwise comparisons were made among our data and 2 other aquatic birnavirus sequences previously published. Several hypervariable regions were identified within the large ORF. The most divergent pair of viruses exhibited a similarity of 80.1% in the deduced amino acid sequence encoded by the large ORF. Genomic relationships revealed in a phylogenetic tree constructed from comparison of the deduced amino acid sequences of the large ORF demonstrated that these viruses were clustered into several genogroups. Phylogenetic comparison of the deduced amino acid sequences of the VP2 coding region of 28 aquatic birnavirus isolates, including the type strains of all 9 serotypes, demonstrated 6 genogroups, some of which were comprised of several genotypes. The most divergent pair of viruses exhibited a similarity of 81.2% in the deduced amino acid sequence from the VP2 coding region. In contrast to previous studies of much shorter genomic sequences within the C-terminus-pVP2/NS junction coding region, these genogroups based on the entire large ORF or the VP2 coding region generally correlated with geographical origin and serological classification. Isolates from the major Canadian serotypes were more closely related to the European isolates than to isolates from the United States. KEY WORDS: Aquatic birnavirus · Infectious pancreatic necrosis virus · Genogroups · Phylogenetic relationships Resale or republication not permitted without written consent of the publisherDis Aquat Org 45: [89][90][91][92][93][94][95][96][97][98][99][100][101][102] 2001 implicated as the etiologic agents of disease in a variety of fish species important in fish farming and aquaculture worldwide. Different strains of aquatic birnaviruses infect different species of fish and cause different diseases, such as infectious pan...

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Polyclonal anti-idiotype (anti-Id) antibodies were prepared in rats against a monoclonal antibody (MAb AS-1) which defines a highly conserved neutralization epitope on virion protein 2 (VP2) of Serogroup A aquatic birnaviruses. Anti-mouse IgG cross-reactive antibodies were removed from rat sera by adsorption to an affinity column of normal mouse IgG and further punfied by subsequent adsorption to and elution from an affinity column coupled with MAb AS-1. Confirmation that these anti-Id antibodies were directed against the paratope of MAb AS-1 and molecularly mimicked the virus epitope was demonstrated in a variety of assays. Anti-Id antibodies reacted in enzyme-linked immunosorbent assay (ELISA) with both whole MAb AS-1 IgG and F(ab);, fragments, but &d not react with 2 unrelated mouse IgGs or F(ab);, fragments. Anti-Id antibodies blocked binding of virus to MAb AS-1 in a dose-dependent manner with 100% inhibition at the highest concentration. Similarly, virus inhibited anti-Id/i&otype binding by 60 %. Furthermore, anti-Id antibodies inhibited the ability of MAb AS-1 to neutralize virus in plaque reduction assays. Anti-ld antibodies induced the production of virus neutralizing antibodies in mice. Anti-Id antibodies also were used to show that the AS-1 epitope is a presumptive cell attachment site on the virus which recognizes and binds to specific cell receptors Anti-Id antibodies were shown to bind to a variety of both salmonid and non-salmonid fish cell cultures. Pretreatment of fish cell cultures with virus inhibited (28 to 50%) binding of anti-ld antibodies. Treatment of fish cell cultures with anti-Id antibodies also resulted in a decrease (98%) in the yield of progeny virus compared with replication of the virus in untreated cells or cells treated with normal rat immunoglobulin.