Quantification of IFN-β and IL-1β gene expression in PBMC after FPV, FPV NS GD or FPV NS VN infection. The cytokines IFN-β (A) and IL-1β (B) mRNA gene expression profile of PBMC were analyzed by quantitative RT-PCR. The results are expressed as means ± SD from three experiments. Statistical significant difference (p < 0.05) is indicated with letters. Different letters indicate a statistical difference between groups and the same letter means that no statistical difference was observed.