Crystal structure and size-dependent neutralization properties of HK20, a human monoclonal antibody binding to the highly conserved heptad repeat 1 of gp41.
The human monoclonal antibody (mAb) HK20 neutralizes a broad spectrum of primary HIV-1 isolates by targeting the highly conserved heptad repeat 1 (HR1) of gp41, which is transiently exposed during HIV-1 entry. Here we present the crystal structure of the HK20 Fab in complex with a gp41 mimetic 5-Helix at 2.3 Å resolution. HK20 employs its heavy chain CDR H2 and H3 loops to bind into a conserved hydrophobic HR1 pocket that is occupied by HR2 residues in the gp41 post fusion conformation. Compared to the previously described HR1-specific mAb D5, HK20 approaches its epitope with a different angle which might favor epitope access and thus contribute to its higher neutralization breadth and potency. Comparison of the neutralization activities of HK20 IgG, Fab and scFv employing both single cycle and multiple cycle neutralization assays revealed much higher potencies for the smaller Fab and scFv over IgG, implying that the target site is difficult to access for complete antibodies. Nevertheless, two thirds of sera from HIV-1 infected individuals contain significant titers of HK20-inhibiting antibodies. The breadth of neutralization of primary isolates across all clades, the higher potencies for C-clade viruses and the targeting of a distinct site as compared to the fusion inhibitor T-20 demonstrate the potential of HK20 scFv as a therapeutic tool.
Unit of Virus Host Cell Interactions, UMI 3265, Université Joseph Fourier-EMBL-CNRS, Grenoble, France.
Charles
C
Sabin
Davide
D
Corti
Victor
V
Buzon
Mike S
MS
Seaman
David
D
Lutje Hulsik
Andreas
A
Hinz
Fabrizia
F
Vanzetta
Gloria
G
Agatic
Chiara
C
Silacci
Lara
L
Mainetti
Gabriella
G
Scarlatti
Federica
F
Sallusto
Robin
R
Weiss
Antonio
A
Lanzavecchia
Winfried
W
Weissenhorn
D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000378:metabolism; D057134:Antibodies, Neutralizing / Q000276:immunology* / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D015483:HIV Antibodies / Q000276:immunology*; D015700:HIV Envelope Protein gp41 / Q000737:chemistry* / Q000502:physiology*; D015658:HIV Infections / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D015497:HIV-1 / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007128:Immunoglobulin Fragments / Q000276:immunology / Q000378:metabolism; D007074:Immunoglobulin G / Q000276:immunology / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009500:Neutralization Tests; D011487:Protein Conformation; D020349:Surface Plasmon Resonance
D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D015483:HIV Antibodies; D015700:HIV Envelope Protein gp41; D007128:Immunoglobulin Fragments; D007074:Immunoglobulin G