FIG. 4.

Comparison of sCD4 pretreatment of effector cells versus target cells. Effector cells were transfected with pG1NT7β-gal and infected with recombinant vaccinia virus encoding the designated Envs. Target cells were transfected with pGA9-CKR5 (CCR5) and infected with vP11T7gene1. The effector cells or target cells were preincubated with either 200 nM 4D sCD4 (sCD4: +) or an equivalent volume of buffer (sCD4: −). The cells were then washed twice prior to cell mixing. As a positive control, sCD4 was added at the time of cell mixing. The background values obtained with Unc, which ranged from 0.45 to 0.75, were subtracted from the values for the indicated Envs. Abbreviations are given in the legend to Fig. 1.