
 Fig . 7. Selection of potential SB239063-resistant mutants. ( A ) Long-term  in vitro  culture of BPXV in the presence of SB239063. BPXV was sequentially passaged in Vero cells in the presence of 5 μg/mL SB239063 or equivalent volume of DMSO. At each passage, the confluent monolayers of Vero cells were infected with the virus, washed 5 times with PBS before a fresh aliquot of MEM was added and incubated for 48–96 h or until the appearance of cytopathic effect in ≥50% cells. The virus released in the supernatant was termed as passage 1 (P1) and used in the second round of infection, which was termed as P2. Virus at P0, P10, P20, P30, P40, P50 and P60 was evaluated for its sensitivity to SB239063. ( B ) Relative growth of BPXV-P0, BPXV-P60-SB239063 and BPXV-P60-Control in p38-depleted cells. Confluent monolayers of WT or p38-α KO Vero cells were infected with the indicated viral variants at MOI of 0.1 for 1 h. Following washing, WT Vero cells were treated with either SB239063 (10 μg/mL) or equivalent volume of DMSO. The yields of infectious progeny virus particles at 48 hpi were determined by plaque assay. Relative growth of mutant viruses in p38-depleted cells (inhibitor-treated and p38-α KO cells) is also shown in the right panel. Error bars indicate SD. Pair-wise statistical comparisons were performed using Student’s  t -test. (*** =  P  < 0.001). Values are means ± SD and representative of the result of at least three independent experiments.