FIG 3.

RdRp-L123F conferred ribavirin resistance on different EV71 strains. (A) RD cell monolayers were infected at an MOI of 1 with different viral populations in the absence or presence of 2 mM ribavirin. The progeny viruses were titrated at 24 h postinfection. (B) Ratios of mean titers of progeny viruses produced in the presence of ribavirin (R+) to those produced in the absence of ribavirin (R−) indicated that RG/B4-L123F, RG/B5-L123F, and RG/C4-L123F were ribavirin resistant and generated more progeny than their parental RG/B4, RG/B5, and RG/C4 viruses, respectively. (C) Growth titer curves of RG/B4 and RG/B4-L123F in different concentrations of ribavirin. RD cells were infected at an MOI of 1, and the viral progeny were titrated at 20 h postinfection. The growth titer of ribavirin-resistant RG/B4-L123F was significantly higher than that of RG/B4 in the presence of ribavirin (*, P < 0.05; **, P < 0.001; n = 6). (D) One-step growth curves of RG/B4 and RG/B4-L123F in the absence or presence of 2 mM ribavirin (Rb). RD cells were infected at an MOI of 1 and frozen at different time points after infection, and the viral progeny were titrated by TCID₅₀ assay. The RG/B4 and RG/B4-L123F viruses grew with no significant difference in the absence of ribavirin, but the titer of RG/B4-L123F was significantly higher than that of RG/B4 at each time point after infection (*, P < 0.05; **, P < 0.001; n = 6). All experiments were carried out in triplicate, and the titration was duplicated for each experiment. Means ± SDs are shown. wt, wild type.