VZV mutant lacking the IDE binding domain of gE shows reduced fusogenicity by membrane fusion assay.

(A) Melanoma cells expressing T7 polymerase were infected with VZV ROka, ROka68D32-71, and the cells were incubated with HeLa cells containing the β–galactosidase gene driven by the T7 promoter or a control GFP plasmid for 20 hr. The cells were lysed, incubated with chlorophenol red-β-D-galactopyranoside, and β–galactosidase activity was measured using a spectrophotometer at OD570 nm. The experiment was also performed at 16 hr and 24 hr and similar results were obtained. Vertical lines indicate standard deviations. (B) Human melanoma cells expressing T7 polymerase were infected with the same MOI of ROka-GFP or ROka68D32-71-GFP, and cells were co-incubated with HeLa cells containing the β–galactosidase gene driven by the T7 promoter for 16 hrs. The cells were lysed, incubated with chlorophenol red-β-D-galactopyranoside, and β–galactosidase activity was measured using a spectrophotometer at OD570 nm. The experiment was performed twice with similar results. (P<0.001 for ROka-GFP vs. ROka68D32-71-GFP, Student t test). Vertical lines indicate standard deviations.