GENOMIC CHARACTERIZATION OF THE VIRUS CAUSING INFECTIOUS SALMON ANEMIA IN ATLANTIC SALMON (SALMO-SALAR L.) - AN ORTHOMYXO-LIKE VIRUS IN A TELEOST

The genome of infectious salmon anemia virus (ISAV), which infects far med Atlantic salmon (Salmo salar L.), is characterized here, The virus has an RNA genome, as shown by using specific DNA virus metabolic inh ibitors and radioactive in vivo labeling of ISAV nucleic acid, Electro phoresis of [C-14] uridine-labeled ISAV RNA revealed that the ISAV gen ome is segmented, The genome consists of eight segments that range fro m 1.0 to 2.3 kb, with a total molecular size of approximately 14.5 kb, One ISAV-specific molecular clone, corresponding to the smallest geno me segment, was obtained by cDNA cloning of mRNA from an ISAV-infected cell culture, This clone gave a positive hybridization signal on Nort hern blots of pelleted ISAV. Pretreatment of the ISAV pellet with RNas e A resulted in the disappearance of the positive hybridization signal , demonstrating that the genome is single stranded, Reverse transcript ase PCR with primers corresponding to sequences from the molecular clo ne and target RNA from ISAV-infected and noninfected fish tissues gave specific positive reactions, Alignments of the nucleotide sequence of the molecular clone did not reveal significant homology with any othe r available sequence in databases, However, the data presented here, t ogether with morphological and replicational properties previously des cribed, indicate that ISAV has a strong resemblance to members of the Orthomyxoviridae family. This is the first thoroughly characterized or thomyxo-like virus isolated from a teleost.