FIG 4.

Effects of soluble CD4 on the binding of anti-gp120 MAbs to virus particles in solution. (A) Alexa-647 labeled MAb b12 (6.6 μg/ml) was tested for binding to virions treated for 90 min at 37°C with sCD4 concentrations ranging between 0 and 100 μg/ml. (B) Alexa 647-labeled MAb 17b (5.5 μg/ml) was tested under the same conditions. The relative fraction of MAb that adopts a lower diffusion coefficient (∼8 μm²/s) as a result of virion binding (see Materials and Methods) is shown. All experiments were repeated three times, and average values are shown. Error bars indicate standard deviations.