FIG. 2.

Fusogenic activities of each Env with recombinant coreceptors. Target NIH 3T3 cells coexpressing coreceptors and CD4 (and containing the lacZ gene linked to the T7 promoter) as well as control cells lacking coreceptors were prepared as described in the legend for Fig. 1. Effector HeLa cells were transfected with plasmids encoding the indicated Envs and then infected with vP11T7gene1 (T7 polymerase). After overnight incubation to allow recombinant protein expression, cells were mixed and fusion was scored after 3 h. The low background values for each Env obtained with the control target cells expressing CD4 but no coreceptors were subtracted to give the data shown. Error bars indicate the sample standard deviations of the mean values obtained from duplicate samples. OD, optical density.