FIG. 2.

Dose-response comparison of 4D (sCD4-369) and 2D (sCD4-183) sCD4 for activation of cell fusion. Effector cells were transfected with pG1NT7β-gal and infected with vCB-28 (JR-FL Env). Target cells were transfected with pGA9-CKR5 (encoding CCR5) and infected with vP11T7gene1. At the time of cell mixing, the indicated concentrations were added for each sCD4 construct. The low background value (0.83) obtained in assays using effector cells infected with vCB-16 (Unc Env) was subtracted to give the values shown. Abbreviations are given in the legend to Fig. 1.