DNA vaccine expressing the non-structural proteins of Piscine orthoreovirus delay the kinetics of PRV infection and induces moderate protection against heart -and skeletal muscle inflammation in Atlantic salmon (Salmo salar)

Abstract Piscine orthoreovirus (PRV) causes heart- and skeletal muscle inflammation (HSMI) in farmed Atlantic salmon ( Salmo salar ). Erythrocytes are the main target cells for PRV. HSMI causes significant economic losses to the salmon aquaculture industry, and there is currently no vaccine available. PRV replicates and assembles within cytoplasmic structures called viral factories, mainly organized by the non-structural viral protein µNS. In two experimental vaccination trials in Atlantic salmon, using DNA vaccines expressing different combinations of PRV proteins, we found that expression of the non-structural proteins µNS combined with the cell attachment protein σ1 was associated with an increasing trend in lymphocyte marker gene expression in spleen, and induced moderate protective effect against HSMI.