Specific infectivity of mutant FMDV populations.

aMutation frequencies are based on the analysis of 18,620 nucleotides of the mutant spectrum of R-Ap35 (14 molecular clones) and 19,950 nucleotides for R-Ap60 (15 molecular clones). For each clone the genomic region analysed comprised residues 6610 to 8020 (residue numbering is according to [93]).
bValues of virus titer and RNA molecules are the average of three determinations, and standard deviations are given. The specific infectivity was calculated as PFU/RNA molecules (ratio of values in the third to the fourth column). Procedures are detailed in Materials and Methods.