Experimental design. A Induction of ISG transcription by VHSV isolates pathogenic (P) or non-pathogenic (NP) to sole. L15 and poly I:C-inoculated fish were negative and positive controls, respectively. B Induction of an antiviral state by poly I:C. First injection was with L15 or poly I:C. Second injection (24 h after first inoculation) was with L15 (negative control) or pathogenic or non-pathogenic VHSV isolates. Cumulative mortality was determined. In both challenges, ISG transcription was quantified and viral multiplication was also evaluated by viral genome quantification and viral titration.