Protection of RD cells from EV71-induced CPE and increased cell viability. RD cells were transfected with unmodified and 2′-modified siRNAs targeting the 5′ UTR of the EV71 genome and then infected with 0.01 MOI of EV71. (A) Morphological changes in RD cells transfected with 100 nM various siRNAs at 48 h post-infection are shown. ‘Normal’ represents non-infected normal cells. Cells treated only with LipofectamineTM 2000 (mock transfection) and cells transfected with 100 nM of scrambled siRNA (scr) and then infected with EV71 served as negative controls. Three independent experiments were performed. Bar = 100 μm. (B) The viability of RD cells at 24, 36, 48, 60, and 72 h post-infection was evaluated by MTT assays. Viability percentage values shown are means ± SD from three independent experiments, each performed in triplicate. *P < 0.05, compared with mock transfected control. #P < 0.05, compared with 50 nM of si-1, si-1OMe, si-1 F, si-2, si-2OMe, and si-2 F, respectively.