FIG. 3.

Enhanced binding of IgG1-201 in the presence of sCD4. Binding of IgG1-201 to SIV gp130 in the presence of increasing concentrations of sCD4. ELISA plates (96-well) were coated with recombinant SIVsmH4 gp120 (a gift from Nancy Haigwood) and incubated overnight. Plates were blocked and incubated with serial dilutions of sCD4 (AIDS Research and Reference Reagent Program, National Institute of Allergy and Infectious Diseases) for 3 h at 37°C. Unbound sCD4 was removed by washing with Tris-borate-saline solution supplemented with 0.05% Tween 20, and fixed concentrations of the gp120-specific antibodies IgG1-201 and KK45 were added for 1 h at 37°C.