Designed amiRNAs and target sites selection using luciferase assay. Five amiRNAs were designed via online tools of Invitrogen Company (A). Transfection efficiency assay via GFP monitoring after co-transfected with plasmids expressing amiRNAs that fused to GFP coding gene and psiCHECK2-GP5 or -M. Images were taken with an inverted fluorescence microscope in bright (left) or fluorescence (right) light of the same field. Magnification, 40× (upper) or 100 × (bottom) (B). Inhibition of Renilla luciferase expression by amiRNAs that targeting PRRSV GP5 or M protein coding sequences were measured by duel luciferase assay at 48 hours post-cotransfection. The Renilla luciferase data has been normalized to firefly luciferase data. Normalized Renilla luciferase expression in the psiCHECK2 only transfection was set at 100%. Data are mean ± SD, n = 3~4, *p < 0.05 vs. psiCHECK alone transfected cells group (C, D).