Mutagenesis of the CD4 binding site does not alter the m2 binding site. Wild type gp120 BaL or the gp120 BaL D368R mutant were captured onto ELISA wells using mAb 1B6 or HIVIg as indicated. The captured gp120 was then detected with various anti-gp120 mAbs (as indicated). CD4 binding to captured gp120 was detected with biotinylated anti-CD4 mAb CG9. Bound phages were detected with an anti-M13 mAb. Note the 1B6 mAb which competes with m2 binding (Figure 6) does not interfere with anti-gp120 mAbs or CD4. The experiment was carried out in duplicate.