title: Affinity maturation and characterization of a human monoclonal antibody against HIV-1 gp41.
abstract: The human D5 monoclonal antibody binds to the highly conserved hydrophobic pocket on the N-terminal heptad repeat (NHR) trimer of HIV-1 gp41 and exhibits modest yet relatively broad neutralization activity. Both binding and neutralization depend on residues in the complementarity determining regions (CDRs) of the D5 IgG variable domains on heavy chain (VH) and light chain (VL). In an effort to increase neutralization activity to a wider range of HIV-1 strains, we have affinity matured the parental D5 scFv by randomizing selected residues in 5 of its 6 CDRs. The resulting scFv variants derived from four different CDR changes showed enhanced binding affinities to gp41 NHR mimetic (5-helix) which correlated to improved neutralization potencies by up to 8-fold. However, when converted to IgG1s, these D5 variants had up to a 12-fold reduction in neutralization potency over their corresponding scFvs despite their slightly enhanced in vitro binding affinities. Remarkably, D5 variant IgG1s bearing residue changes in CDRs that interact with epitope residues N-terminal to the hydrophobic pocket (such as VH CDR3 and VL CDR3) retained more neutralization potency than those containing residue changes in pocket-interacting CDRs (such as VH CDR2). These results provide compelling evidence for the existence of a steric block to an IgG that extends to the gp41 NHR hydrophobic pocket region, and can be a useful guide for developing therapeutic antibodies and vaccines circumventing this block.
authors.affiliation: Department of Biologics Research, Merck Research Laboratories, West Point, PA, USA. donna_montgomery@merck.com
authors.forename: Donna L
authors.initials: DL
authors.lastname: Montgomery
authors.forename: Ying-Jie
authors.initials: YJ
authors.lastname: Wang
authors.forename: Renee
authors.initials: R
authors.lastname: Hrin
authors.forename: Micah
authors.initials: M
authors.lastname: Luftig
authors.forename: Bin
authors.initials: B
authors.lastname: Su
authors.forename: Michael D
authors.initials: MD
authors.lastname: Miller
authors.forename: Fubao
authors.initials: F
authors.lastname: Wang
authors.forename: Peter
authors.initials: P
authors.lastname: Haytko
authors.forename: Lingyi
authors.initials: L
authors.lastname: Huang
authors.forename: Salvatore
authors.initials: S
authors.lastname: Vitelli
authors.forename: Jon
authors.initials: J
authors.lastname: Condra
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Liu
authors.forename: Richard
authors.initials: R
authors.lastname: Hampton
authors.forename: Andrea
authors.initials: A
authors.lastname: Carfi
authors.forename: Antonello
authors.initials: A
authors.lastname: Pessi
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Bianchi
authors.forename: Joseph
authors.initials: J
authors.lastname: Joyce
authors.forename: Chris
authors.initials: C
authors.lastname: Lloyd
authors.forename: Romas
authors.initials: R
authors.lastname: Geleziunas
authors.forename: David
authors.initials: D
authors.lastname: Bramhill
authors.forename: Vicki M
authors.initials: VM
authors.lastname: King
authors.forename: Adam C
authors.initials: AC
authors.lastname: Finnefrock
authors.forename: William
authors.initials: W
authors.lastname: Strohl
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: An
mesh_terms: D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology*; D057134:Antibodies, Neutralizing / Q000737:chemistry / Q000276:immunology; D000915:Antibody Affinity / Q000276:immunology*; D022801:Complementarity Determining Regions / Q000737:chemistry; D015483:HIV Antibodies / Q000737:chemistry / Q000276:immunology*; D015700:HIV Envelope Protein gp41 / Q000276:immunology*; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D007128:Immunoglobulin Fragments / Q000276:immunology*; D007074:Immunoglobulin G / Q000737:chemistry / Q000276:immunology; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D019151:Peptide Library
chemical_list: D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D022801:Complementarity Determining Regions; D015483:HIV Antibodies; D015700:HIV Envelope Protein gp41; D007128:Immunoglobulin Fragments; D007074:Immunoglobulin G; D019151:Peptide Library