FIG 6.

Viral neutralization by CD4-binding site ligands. Recombinant HIV-1 expressing luciferase and bearing WT or W69 Env variants were normalized by reverse transcriptase activity. Equal amounts of viruses were incubated with serial dilutions of sCD4 (A), VRC01 (B), VRC13 (C), and VRC16 (D) for 1 h at 37°C before infecting Cf2Th-CD4-CCR5 cells. Luciferase activity in cell lysates was measured to determine the infectivity. Infectivity was normalized to 100% in the absence of the ligand. Data shown are representative of results from at least three independent experiments performed in quadruplicate.