Fig. 2.

Cell fusion activities of the gB insertion mutants in relation to cell surface expression. CHO cells were transfected with plasmids expressing WT gB or each of the gB mutants capable of cell surface expression, other HSV-1 glycoproteins (gD, gH, and gL) and T7 polymerase (effector cells). CHO-nectin-1 cells were transfected with a plasmid carrying the firefly luciferase gene under control of the T7 promoter (target cells). One set of effector cells was used for CELISA (results shown also in Fig. 1), and the other set was mixed with the target cells for assessment of cell fusion activity by quantification of luciferase activity. Positions of the mutations with respect to structural domains are indicated across the top. Categorization of the mutants with respect to phenotype is indicated across the bottom: Category 1, indistinguishable from WT gB or with enhanced fusion activity; Category 2, normal levels of cell surface expression but reduced fusion activity; Category 3, normal or reduced levels of cell surface expression but no fusion activity. The results are expressed as percentage of WT gB activity, after subtraction of background values obtained in the absence of gB expression, and are means and SDs of three independent experiments.