Affinity maturation and characterization of a human monoclonal antibody against HIV-1 gp41.
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.
Montgomery
Donna L
DL
Department of Biologics Research, Merck Research Laboratories, West Point, PA, USA. donna_montgomery@merck.com
Wang
Ying-Jie
YJ
Hrin
Renee
R
Luftig
Micah
M
Su
Bin
B
Miller
Michael D
MD
Wang
Fubao
F
Haytko
Peter
P
Huang
Lingyi
L
Vitelli
Salvatore
S
Condra
Jon
J
Liu
Xiaomei
X
Hampton
Richard
R
Carfi
Andrea
A
Pessi
Antonello
A
Bianchi
Elisabetta
E
Joyce
Joseph
J
Lloyd
Chris
C
Geleziunas
Romas
R
Bramhill
David
D
King
Vicki M
VM
Finnefrock
Adam C
AC
Strohl
William
W
An
Zhiqiang
Z
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
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