IRF1 and infection: Figure 8c indicates that Npro overexpression did decrease IRF1 transcription (P < 0.05, in comparison with control cells expressing EGFP). The IFN-λ3 promoter activity was also reduced in the Npro-overexpressed cells (Figure 8d). Western blotting showed that either infection with wtCSFV or Npro overexpression led to decreased expression of the IRF1 protein in poly(I:C) stimulated cells while the ∆Npro mutant strain did not have inhibitory effect (Figure 8e–h).