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Published July 29, 2022 | Submitted
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Antibody recognition of CD4-induced open HIV-1 Env trimers


HIV-1 envelope (Env), a heterotrimer of gp120-gp41 subunits, mediates fusion of the viral and host cell membranes after interactions with the host receptor CD4 and a coreceptor. CD4 binding induces rearrangements in Env trimer, resulting in a CD4-induced (CD4i) open Env conformation. Structural studies of antibodies isolated from infected donors have defined antibody-Env interactions, with one class of antibodies specifically recognizing the CD4i open Env conformation. Here, we characterize a group of monoclonal antibodies isolated from HIV-1 infected donors (V2i mAbs) that display characteristics of CD4i antibodies. Binding experiments demonstrate that the V2i mAbs preferentially recognize CD4-bound open Env trimers. Structural characterizations of V2i mAb-Env-CD4 trimer complexes using single-particle cryo-electron microscopy show recognition by V2i mAbs using different angles of approach to the gp120 V1V2 domain and the β2/β3 strands on a CD4i open conformation Env with no direct interactions of the mAbs with CD4. We also characterize CG10, a CD4i antibody that was raised in mice immunized with a gp120-CD4 complex, complexed with Env trimer and CD4. CG10 exhibits similar characteristics to the V2i antibodies: i.e., recognition of the open Env conformation, but shows direct contacts to both CD4 and gp120. Structural comparisons of these and previously characterized CD4i antibody interactions with Env provide a suggested mechanism for how these antibodies are elicited during HIV-1 infection.

Additional Information

The copyright holder for this preprint is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY 4.0 International license. Zhi Yang and Kim-Marie A. Dam contributed equally to this work. Author order was determined by the two co-first authors after negotiation. We thank Jost Vielmetter at the Beckman Institute Protein Expression Center at Caltech for protein production, John Moore (Weill Cornell Medical College) for the B41 stable cell line, and James Robinson (Tulane University) for the JR-52 mAb. Cryo-EM studies were performed in the Beckman Institute Resource Center for Transmission Electron Microscopy at Caltech with assistance from Dr. S. Chen (director). We thank the Gordon and Betty Moore and Beckman Foundations for the gifts to Caltech to support the Molecular Observatory (Dr. Jens Kaiser, director) and the Stanford Synchrotron Radiation Lightsource (SSRL) beamline staff for data collection. Use of the SSRL, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under contract No. DE-AC02-c76SF00515. The SSRL Structural Molecular Biology Program is supported by the DOE Office of Biological and Environmental Research, and by the National Institutes of Health, National Institute of General Medical Sciences (P41GM103393). The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official views of NIGMS or NIH. This work was supported by grants from the National Institute of Allergy and Infectious Diseases (NIAID) HIVRAD P01 AI100148 (P.J.B.) and R01AI145655 (S.Z.P.), a Gates CAVD grant INV-002143 (P.J.B.), support from the Department of Medicine, Icahn School of Medicine at Mount Sinai (S.Z.P.), and the generous support of Dr. Peter Kraus (J.M.G.). Author contributions. Z.Y., K.A.D, J.M.G., S.Z.-P., and P.J.B. designed the research. Z.Y. and K.A.D. performed experiments and analyzed results. Z.Y., K.A.D., and P.J.B. wrote the paper with input from co-authors. Data availability. Cryo-EM maps generated in this study have been deposited in the Electron Microscopy Data Bank (EMDB) with accession codes EMD-27209, EMD-27210, EMD-27211, and EMD-27212 for V2i Fab complexes 1393A-BG505-sCD4, 1361-BG505-sCD4, 697D-BG505-sCD4, and 830A-BG505-sCD4, respectively. The cryo-EM map for CG10-B41-sCD4 complex was deposited in the EMDB under the accession code EMD-27208, and atomic model coordinates were deposited in the Protein Data Bank (PDB) under the accession code of 8D5C. The X-ray structure of CG10 Fab was deposited in the PDB under the code of 8D54. The authors have declared no competing interest.

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August 20, 2023
August 20, 2023