Fig. 2.

The type O FMDV 3D mutants with Asia1 3D substitutions are low-fidelity variants. (A) A mean of seventy partial P1 sequences (approximately 35,000 nucleotides per replicate) were obtained. The mean mutation frequencies (number of nucleotide mutations per 10,000 nt sequenced)±SD represent the averages of all the replicates. The same pattern of reduced mutation frequency for other polymerase mutants compared to the WT was observed for each replicate (two-tailed Mann-Whitney test, n = 3, *P<0.05, **P<0.01). (B) Replication ability and of FMDV RdRp low-fidelity mutants. BHK-21 cells were infected with the mutants O-D5N, O-A38V, O-DA, O-DAMM or FMDV WT at an MOI of 0.01. The virus harvested at different times were titrated and expressed as TCID_50. Mean values±SD are shown (repeated-measures ANOVA, n = 3; ns for all mutants compared with WT). (C and D) RNA virus mutagen sensitivity assay of viral strains. BHK-21 cells, treated with different concentrations of RNA mutagen or mock-treated, were infected at MOI of 0.01; 72 h post-infection, the infectivity in the progeny virus was determined by TCID₅₀ assay. Mean virus titers ±SD are shown (Student’s t-test, n = 4; *P<0.05, **P<0.01).