Antibody engineering for increased potency, breadth and half-life

Sievers, Stuart A.; Scharf, Louise; West, Anthony P.; Bjorkman, Pamela J.

A follow-up study [56 & ] used structure-based design to reduce available routes of HIV-1 escape from antibody pressure. Bioinformatic analysis identified gp120 sequence correlates for resistance to VRC01-class antibodies by noting that variations at highly conserved gp120 residues 279 gp120 -280 gp120 and 458 gp120 -459 gp120 (the 'NNGG' motif, named for the Asn and Gly residues at these positions) lead to resistance [53] ; these predictions were experimentally verified in vitro [53] and in HIV-1 infected humanized mice [22] . To counteract the effects of gp120 escape mutations, rational design was used to create two new mutants: 45-46m2 (S28Y LC ), which introduces contacts with an Asn276 gp120 -linked glycan, as seen in VRC01/gp120 complexes, but not NIH45-46/gp120 complexes [48, 55] , and 45-46m7 (W47 V HC ), which removes steric clashes with gp120 substitutions in the GG motif [56 & ]. 45-46m2 neutralized nearly 96% of viruses, an improvement over other CD4bs bNAbs, which typically neutralize nearly 90% of strains. In vivo experiments demonstrated that viral escapes were no longer found in the GG motif when HIV-1 infected animals were treated with 45-46m2/45-46m7, and a resulting A281T gp120 escape variant had reduced viral fitness [56 & ]. These studies demonstrate that even highly somatically mutated bNAbs are not necessarily optimal as isolated from donors, and that even if it is impossible to completely prevent HIV-1 escape from bNAbs, it might be possible to drive the evolution of viruses with reduced fitness that could be more easily combated by host defense mechanisms.