Fig. 1.

ELISAs of human anti-gp120 MAb binding to gp120 versus constrained gp120 with or without CD4. Monomeric HIV BaL gp120 (black bars), SCBaL/M9 (light gray bars), which presents a constrained gp120 structure in the absence of CD4, and FLSC (dark gray bars), which presents a single-chain gp120-CD4 complex, were captured on the substrate as described in Materials and Methods. The captured antigens were reacted with 3-fold serial concentrations of the indicated human MAbs starting at 10 μg/ml; bound antibody was detected as described in Materials and Methods. Reciprocal one-half maximum binding titers were calculated from the concentration versus absorbance curves after subtraction of background signal. As MAbs 19e and ED47 did not achieve a one-half maximum signal with either gp120 or SCBaL/M9, titers are given as >10. All assays were performed in duplicate; average values are shown. Error bars indicate highest and lowest values.