The epitopes recognized by the 55 remaining mAbs were mapped using three experimental approaches: i) cross-competition against mAbs of known specificity or soluble CD4; ii) binding to gp120 mutants or gp41 constructs representing different conformational intermediates; iii) Pepscan analysis. The results of the analysis performed on the gp120-specific and gp41-specific mAbs are presented in Table 1 and Table 2 , and the data are summarized in a pie chart in Figure 6 .