FIG. 6.

Thermostability of the dependent variant. HeLa cells were incubated with the D6/01 variant in the absence of the drug for 1 h at 4°C. After infection for 6 h in the presence or absence of the drug at the indicated temperatures, the cells were lysed and viral titers were determined by plaque assay in the presence of the compound. The drug-plating index is expressed as the ratio between the plaque titer in the presence of the drug and that in the absence of the drug.