Comparative capture of gp120 with two defining mAbs. gp120 BaL was captured on ELISA wells using immobilized b12 mAb (A) compared with immobilized 1B6 mAb (B) and incubated with different phages as indicated. Bound phages were detected with rabbit anti-M13 polyclonal sera while detection of gp120 was accomplished using the LG4 mAb. Note that both b12 and 1B6 are efficient in capturing gp120 BaL yet distinct regarding overlap with the m2 binding epitope. The b12 epitope overlaps the CD4bs (see for example Figure 5) and does not interfere with m2 binding. The 1B6 epitope is different and distinct, competes for m2 binding and does not interfere with binding of either CD4 or b12 (see Figure 7). The experiment was carried out in duplicate.