Biochemical characterization of salmon pancreas disease virus

Salmon pancreas disease virus (SPDV) has been shown to cause severe economi c losses in farmed Atlantic salmon (Salmo salar) and has been reported to o ccur in Europe, Scandinavia and the United States. This paper describes the biochemical characterization of SPDV in terms of its RNA and protein compo sition. SPDV was purified by precipitation from infected Chinook salmon emb ryo (CHSE-214) cell-culture supernatant and sucrose density-gradient centri fugation. Fractions containing virus were identified by an immunodot blot a ssay using an SPDV-specific MAb. Two major proteins with molecular masses o f approximately 55 and 50 kDa, putatively identified as the El and E2 alpha virus glycoproteins respectively, were detected when purified virus prepara tions were analysed by PAGE. Radiolabelling experiments indicated that SPDV infection of CHSE-214 cells did not shut-off host-cell protein synthesis, making attempts to identify virus-specific proteins unsuccessful. However, radioimmunoprecipitation assay (RIPA) experiments showed that two SPDV-spec ific MAbs reacted with a protein in the 50-55 kDa range. Northern blot hybr idization with cloned cDNA probes indicated that infected cells contained R NA species of approximately 11.4 and 4 kb, which correspond to the genomic and subgenomic RNAs specified by SPDV. The results described are consistent with SPDV being characterized as an alphavirus.