Antibody engineering for increased potency, breadth and half-life

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

Some of the most potent antibodies against HIV-1 that are the focus of engineering efforts are VRC01class antibodies, which target the CD4bs using a VH1-2 Ã 02 derived heavy chain to mimic CD4 recognition of gp120 [8, 15, 16, 46, 53, 54 && ]. A structurebased approach was taken to improve NIH45-46 [46] , a more potent clonal variant of VRC01 [15] . Structural and mutagenesis studies demonstrated that a four-residue insertion within the NIH45-46 CDRH3 loop accounted for its increased potency [55] . Although VRC01-like bNAbs effectively mimic CD4 [48] , both VRC01 and NIH45-46 fail to fill a hydrophobic pocket within gp120 to mimic the burying of a hydrophobic CD4 residue, Phe43 CD4 . Mutants were created by substituting the Phe43 CD4equivalent residue in NIH45-46, Gly54 NIH45-46 , and improved potencies were found for Trp, Phe, Tyr and His substitutions [55] . The most promising mutant, NIH45-46 G54W , showed an overall 10-fold increase in neutralization potency and neutralized some NIH45-46 resistant strains [55] . Residue 54 is a Trp in some VRC01-related bNAbs that are less potent than VRC01 or NIH45-46, for example VRC03 [48] , demonstrating that a Gly-to-Trp substitution at position 54 is a possible somatic mutation in this bNAb lineage, but that maximal increased potency from this substitution requires other features of a VRC01like bNAb, most likely the CDRH3 loop insertion.