Comparative analysis of marine and freshwater viral haemorrhagic septicaemia virus (VHSV) isolates antagonistic activity.

•Marine and freshwater VHSV isolates interfere with ssmx promoter induction in a dose-dependent way.•The minimal MOI required to exert antagonistic activity on ssmx promoter is inversely related with isolate virulence to sole.•The antagonistic effect of the marine VHSV isolate seems to be mx promoter specific.•Viral nv RNA synthesis kinetics might be related with the differential antagonistic activity of the isolates.