Fitness of FMDV 3D(SSI) relative to FMDV Wt in the presence of R, FU, or a mixture of R and FU.

aGrowth-competition experiments were initiated by infecting 2×106 BHK-21 cells with 7×105 PFU of FMDV Wt and FMDV 3D(SSI) in the absence of drugs or in the presence either of 5000 µM R, 2000 µM FU or a mixture of 5000 µM R and 2000 µM FU, as indicated in the first column. Progeny virus was used to infect fresh BHK-21 cells monolayers under the same conditions. A total of 3 passages were carried out. The initial population and the populations at passages 1, 2 and 3 were sequenced and the proportion of the two competing genomes were determined by nucleotide sequencing and measurement of the areas of the relevant bands. The three R2 values given correspond to each of the three determinations. The average fitness value and standard deviation are given. Drug treatment of cells and calculation of relative fitness are described in Materials and Methods.