FIG. 4.

Comparison of the Vero cell line that contains both pICP8SINrep/LacZ and the packaging helper plasmid (V3-45N) with the Vero cell line containing only the replicon plasmid (V3-45-21). V3-45N cells were isolated as described in Materials and Methods. V3-45-21 cells are a subclone of the original cloned V3-45 cells. β-Galactosidase assays were performed as described in Materials and Methods. (A) β-Galactosidase activity of V3-45N and V3-45-21 cell extracts 15, 24, and 48 h after infection with HSV-1 (MOI = 0.5). Extracts were made from the cells in the wells of a 24-well dish by using 250 μl of lysis buffer, and 10 μl of extract was used to assay β-galactosidase activity. The data point indicated with an asterisk (∗) was obtained by diluting the sample to obtain an OD₅₆₂ reading within the linear range and multiplying the result by the dilution factor. (B) β-Galactosidase activity of BHK cells inoculated with medium removed from V3-45N or V3-45-21 cells 15 and 24 h after infection with HSV-1. A sample of the medium (50 μl of 2 ml) was inoculated onto BHK cells in the wells of a 24-well dish. At 18 h postinfection, the BHK cells were treated with 200 μl of lysis buffer and 10 μl of extract was assayed for β-galactosidase activity.