Co-infection with Norwegian Salmonid Alphavirus (NSAV) and Infectious Pancreatic Necrosis Virus (IPNV) in Chinook Salmon Embryo Cells (CHSE-214).

Infectious pancreatic disease (IPN) and pancreas disease (PD) of salmon are viral diseases caused by Infectious Pancreatic Necrosis Virus (IPNV) (Birnaviridae) and Salmonid Alphavirus (SAV) (Togaviridae). Both IPNV- and SAV infections induce lesions in pancreas tissue/cells and are frequently detected from the same individual; hence it is possible that the viruses target the same cell types and therefore might interfere with each other during such infections. In the present study, Chinook Salmon Embryo Cells (CHSE-214) were experimentally co-infected with SAV and IPNV and infections were studied by IFAT, real-time RT- PCR and by viral end-point titration. Real-time RT-PCR was also used to examine to what extent the viruses up-regulated key transcripts (IFN and Mx) in the cellular antiviral immune response. IFAT and end-point titration indicated that SAV to some extent inhibited IPNV replication , whereas IPNV did not affect SAV infections notably. Furthermore, the experiments demonstrated that key transcripts (IFN and Mx) in the cellular antiviral immune system were affected by the infections. Interestingly, transcription of these mRNAs were up-regulated in SAV infected, but not in IPNV infected cells, which could provide a possible explanation to the observed differences in the ability to interfere with the other virus