FIG. 3.

Fab fragment and antibody inhibition of CD4-independent syncytium formation. 293T cells expressing the ΔV1/V2 envelope glycoproteins from the ADA HIV-1 strain were cocultivated with Cf2Th cells expressing CCR5 in the presence of antibodies (A) or Fab fragments (B). IgG1b12, F105, and F91 are CD4BS antibodies, whereas 2G12 recognizes a distinct, carbohydrate-dependent gp120 epitope (25). The percentage of syncytia observed, compared with the number seen in the absence of added antibody or Fab, is reported. The experiment was performed twice with comparable results.