Interaction between the IFN I system and the infection with the non-pathogenic (NP) VHSV isolate. The quantification of ISG transcription (A–C) and viral RNA (D) were evaluated in head kidney from poly I:C-stimulated and non-stimulated animals inoculated with the NP VHSV isolate, and expressed as relative fold change with respect to the negative control group (L15 + L15). Poly I:C-inoculated animals were used as the positive control. Second inoculation was 24 h after the first inoculation. Bars indicate mean ± standard deviation (SD) obtained from three different samples. Different letters denote significant differences (p < 0.05) between groups at each sampling time and within the same group throughout the time. ND Non-detected relative fold change respect to the negative control group (L15 + L15, not represented in the graphic).