FIG. 5.

Contribution of binding antibodies to the CD4 binding site within serum samples of rabbits immunized with the Q461d1^S or Q461e2^R Envs. Rabbit serum samples from Q461d1^S-immunized animals (A) or Q461e2^R-immunized animals (B) at a 1:10 dilution were preincubated with magnetic beads coated with BSA (squares), wild-type SF162 gp120 (triangles), or SF162gp120 containing mutations in the CD4 binding site (circles). The beads were removed, and the depleted plasmas were tested for their ability to bind to wild-type SF162 gp120 (closed symbols) or CD4 binding site mutant gp120 (open symbols). The absorbance at 450 nm is shown on the y axis, with the serum dilution on the x axis.