Growth kinetics of rD72G and rD72N mutant viruses. BHK-21 cells were infected and harvested at different times post infection. (A) Single-step growth curves obtained by titration of virus present at each time. Samples were taken in triplicates and standard deviations are shown in the graphic. (B) RNA production curves were obtained by real time RT-PCR assay from Trizol resuspended monolayers. The mean viral load generated by real time RT-PCR is expressed as log10 vRNA copies/ml of virus transport medium. Samples were taken in triplicates and standard deviations are shown in the graphic. (◆) FMDV Asia1/YS/CHA/05,(■) rD72G and (▴) rD72N.