FIG 1.

Stringent CD4i MAbs do not bind gp120 in the absence of sCD4. An ELISA was used to analyze CD4i MAb binding to gp120s from different strains and to a gp140 trimer. MAbs 17b and 21c show binding to gp120 independent of sCD4 (relaxed binding). MAbs CG10, 19e, and N12-i15 show no binding to gp120 in the absence of sCD4 (stringent binding). Only MAb 17b was cross-reactive with the clade A BG505 SOSIP trimer and its monomer, showing relaxed binding to the monomer and stringent binding to the trimer. Statistically significant differences (P < 0.05) between the “−sCD4” and “+sCD4” columns are marked with an asterisk. OD, optical density.