FIG. 2.

Resistance properties of plaque-purified HPMPDAP^R VACV (strain Lederle). HEL cells were grown to confluence in 96-well dishes, infected with 50 PFU of each cloned virus (nine HPMPDAP^R [○] and five wild-type [•] viruses), and incubated for 3 to 4 days with serial dilutions of each test compound. At least four independent experiments were performed for each test compound. The data are presented as the EC_50,CPE for the HPMPDAP^R clones versus the EC_50,CPE for the parent VACV clones (strain Lederle). Unpaired t tests were used to compare mean EC_50,CPE values of the HPMPDAP^R and wild-type clones for each compound as described in Materials and Methods. P values of <0.01 were considered to be highly significant (**), P values of <0.05 were considered to be significant (*), and P values of >0.05 were considered to not be significant. The changes in mean EC_50,CPE values between wild-type and HPMPDAP^R strains are also shown. Low levels of resistance (change in the range of 2.5- to 7.0-fold and with a P value of <0.05) are indicated by “L,” and high levels of resistance (change of more than sevenfold and a P value of <0.05) are indicated by an “H.” “∼wt” indicates that drug sensitivity was not significantly difference from that of the wild type. The EC_50,CPE values, P values, and changes in EC_50,CPE values are summarized in Table S1 in the supplemental material.