Isolation in cell culture of nodavirus from farmed Atlantic halibut Hippoglossus hippoglossus in Norway

Isolation in cell culture of nodavirus from Atlantic halibut Hippoglossus hippoglossus suffering from viral encephalopathy and retinopathy (VER) is described. The cell line SSN-1 was inoculated with tissue material from affected juveniles (60 d after first feeding). Extensive cytopathic effects (CPE) developed approximately 5 d after inoculation, and were also observed after several passages in the same cell line. Cells from infected cultures showed reactivity with an antiserum against sea bass Dicentrarchus labrax nodavirus in an indirect immunofluorescence test. Analysis of infected cells with reverse transcriptase-polymerase chain reaction (RT-PCR) resulted in a product of the predicted size using primers specific for striped jack Pseudocaranx dentex nodavirus. Electron micrographs of infected SSN-1 cells demonstrated virus particles that were approximately less than 30 nm. Challenge of Atlantic halibut larvae (4 d post-hatching) with supernatants from infected SSN-1 cells resulted in development of VER as verified by immunohistochemistry performed on larvae sampled from Day 9 after challenge. The present results show that a nodavirus from Atlantic halibut has been isolated using the SSN-1 cell line and that virus propagated in cell culture retained virulence.