Despite the substantial immune evasion protecting the mature unliganded state from humoral recognition, after several years of infection, the human immune system does generate broadly neutralizing antibodies. 35O22 and PGT122 are two of these antibodies, which neutralize 62% and 65% of HIV-1 isolates at a median IC50 of 0.033 and 0.05 μg/ml, respectively, . Here we provide additional details on 35O22 and PGT122 recognition. a, 35O22 Fab is shown in ribbon representation (purple (heavy chain) and white (light chain)). The gp120 subunit is shown in red, the gp41 subunit in rainbow (from blue N terminus to orange C terminus), and glycans in green sticks. Complementary determining regions (CDRs) are labeled, and interactive HIV-1-Env residues highlighted in semi-transparent surface representation. At the membrane-distal surface of 35O22, an extended framework 3 region (FW3) of the heavy chain (resulting from an insertion of 8 residues) interacts with strand β1 of the 7-stranded inner domain sandwich of gp120. The heavy chain-CDRs form extensive contacts with the N-linked glycan extending from residue 88gp120. In addition to glycan contacts, the CDR H3 of 35O22 interacts with the α9 helix of gp41. Helix α9 interactions are also made by the FW3 of the light chain (a complete list of contacts is provided in ). Overall, 35O22 buries 1,105 Å2 solvent surface on gp120 (including 793 Å2 with the Asn88gp120 glycan) and 594 Å2 solvent surface on gp41 (including 127 Å2 with the Asn618gp41 glycan). Despite residue 625gp41 being part of the glycan sequon “NMT”, no glycan is observed; indeed, the side-chain amide of residue 625gp41 hydrogen bonds with the side-chain oxygen of Tyr32 in the 35O22 heavy chain, and the presence of an N-linked glycan at residue 625gp41 is difficult to reconcile with 35O22 recognition. b, Same colors as a, with 35O22 Fab shown in surface representation. c, Same colors as a, with 2Fo-Fc at 1σ contour (blue density) shown around glycan 88 of gp120. Antibody 35O22 employs a novel mechanism of glycan-protein recognition, combining a protruding FW3 with CDR H1, H2 and H3 to form a “bowl” that holds glycan. FW3 and CDR H3 provide the top edges of the bowl and interact with the protein surface of gp120, whereas CDR H1 and H2 are recessed and hold/recognize glycan. This structural mechanism of recognition contrasts with the extended CDR H3-draping glycan observed with other antibodies that penetrate the glycan shield such as PG9 and PGT128. d, PGT122 interface details. Ribbon representation of PGT122 Fab in blue (heavy chain) and light blue (light chain) interacting with one gp120 subunit shown in red with glycans in green sticks. Complementary determining regions (CDRs) are labeled, and interactive HIV-1-Env residues highlighted in surface representation. Primary contacts between antibody PGT122 and N-linked glycan involve N137 and N332, with minor contact with N156. Although portions of glycan N301 can be observed in the electron density, no direct contacts with PGT122 are observed; a complete list of contacts between PGT122 and BG505 SOSIP.664 is provided in . e, Same colors as d, with PGT122 Fab shown in surface representation, f, Same colors as d, with 2Fo-Fc at 1σ contour (grey density) shown around glycan 332 of gp120. g,Comparison of bound and unbound Fab conformations. Unbound and HIV-1-Env bound Fabs were superimposed, and ribbon representations and rmsds are displayed. (Left) Unbound 35O22 Fab is colored cyan (heavy chain) and green (light chain) and bound 35O22 Fab deep purple (heavy chain) and white (light chain). (Right) Unbound PGT122 Fab is colored cyan, and bound PGT122 Fab blue (heavy chain) and light blue (light chain). Regions which showed conformational changes are highlighted with black dotted lines. We note that in the 35O22 bound conformation, density is poor and/or sparse for the Fc portion of the Fab.