title: Murine Antibody Responses to Cleaved Soluble HIV-1 Envelope Trimers Are Highly Restricted in Specificity.
abstract: Generating neutralizing antibodies (nAbs) is a major goal of many current HIV-1 vaccine efforts. To be of practical value, these nAbs must be both potent and cross-reactive in order to be capable of preventing the transmission of the highly diverse and generally neutralization resistant (Tier-2) HIV-1 strains that are in circulation. The HIV-1 envelope glycoprotein (Env) spike is the only target for nAbs. To explore whether Tier-2 nAbs can be induced by Env proteins, we immunized conventional mice with soluble BG505 SOSIP.664 trimers that mimic the native Env spike. Here, we report that it is extremely difficult for murine B cells to recognize the Env epitopes necessary for inducing Tier-2 nAbs. Thus, while trimer-immunized mice raised Env-binding IgG Abs and had high-quality T follicular helper (Tfh) cell and germinal center (GC) responses, they did not make BG505.T332N nAbs. Epitope mapping studies showed that Ab responses in mice were specific to areas near the base of the soluble trimer. These areas are not well shielded by glycans and likely are occluded on virions, which is consistent with the lack of BG505.T332N nAbs. These data inform immunogen design and suggest that it is useful to obscure nonneutralizing epitopes presented on the base of soluble Env trimers and that the glycan shield of well-formed HIV Env trimers is virtually impenetrable for murine B cell receptors (BCRs).
  
  
  OBJECTIVE
  Human HIV vaccine efficacy trials have not generated meaningful neutralizing antibodies to circulating HIV strains. One possible hindrance has been the lack of immunogens that properly mimic the native conformation of the HIV envelope trimer protein. Here, we tested the first generation of soluble, native-like envelope trimer immunogens in a conventional mouse model. We attempted to generate neutralizing antibodies to neutralization-resistant circulating HIV strains. Various vaccine strategies failed to induce neutralizing antibodies to a neutralization-resistant HIV strain. Further analysis revealed that mouse antibodies targeted areas near the bottom of the soluble envelope trimers. These areas are not easily accessible on the HIV virion due to occlusion by the viral membrane and may have resulted from an absence of glycan shielding. Our results suggest that obscuring the bottom of soluble envelope trimers is a useful strategy to reduce antibody responses to epitopes that are not useful for virus neutralization.
authors.affiliation: Division of Vaccine Discovery, La Jolla Institute for Allergy and Immunology, La Jolla, California, USA Center for HIV-1/AIDS Vaccine Immunology and Immunogen Discovery (CHAVI-ID), La Jolla, California, USA.
authors.forename: Joyce K
authors.initials: JK
authors.lastname: Hu
authors.affiliation: Division of Vaccine Discovery, La Jolla Institute for Allergy and Immunology, La Jolla, California, USA Center for HIV-1/AIDS Vaccine Immunology and Immunogen Discovery (CHAVI-ID), La Jolla, California, USA.
authors.forename: Jordan C
authors.initials: JC
authors.lastname: Crampton
authors.affiliation: Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, USA.
authors.forename: Albert
authors.initials: A
authors.lastname: Cupo
authors.affiliation: Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Ketas
authors.affiliation: Department of Medical Microbiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Marit J
authors.initials: MJ
authors.lastname: van Gils
authors.affiliation: Department of Medical Microbiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Kwinten
authors.initials: K
authors.lastname: Sliepen
authors.affiliation: Department of Medical Microbiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Steven W
authors.initials: SW
authors.lastname: de Taeye
authors.affiliation: Center for HIV-1/AIDS Vaccine Immunology and Immunogen Discovery (CHAVI-ID), La Jolla, California, USA Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, USA Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard University, Boston, Massachusetts, USA.
authors.forename: Devin
authors.initials: D
authors.lastname: Sok
authors.affiliation: Center for HIV-1/AIDS Vaccine Immunology and Immunogen Discovery (CHAVI-ID), La Jolla, California, USA Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California, USA.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Ozorowski
authors.affiliation: Division of Vaccine Discovery, La Jolla Institute for Allergy and Immunology, La Jolla, California, USA Center for HIV-1/AIDS Vaccine Immunology and Immunogen Discovery (CHAVI-ID), La Jolla, California, USA.
authors.forename: Isaiah
authors.initials: I
authors.lastname: Deresa
authors.affiliation: Department of Molecular Biology, The Scripps Research Institute, La Jolla, California, USA.
authors.forename: Robyn
authors.initials: R
authors.lastname: Stanfield
authors.affiliation: Center for HIV-1/AIDS Vaccine Immunology and Immunogen Discovery (CHAVI-ID), La Jolla, California, USA Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California, USA.
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Ward
authors.affiliation: Center for HIV-1/AIDS Vaccine Immunology and Immunogen Discovery (CHAVI-ID), La Jolla, California, USA Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, USA Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard University, Boston, Massachusetts, USA.
authors.forename: Dennis R
authors.initials: DR
authors.lastname: Burton
authors.affiliation: Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, USA.
authors.forename: Per Johan
authors.initials: PJ
authors.lastname: Klasse
authors.affiliation: Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, USA Department of Medical Microbiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Rogier W
authors.initials: RW
authors.lastname: Sanders
authors.affiliation: Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Moore
authors.affiliation: Division of Vaccine Discovery, La Jolla Institute for Allergy and Immunology, La Jolla, California, USA Center for HIV-1/AIDS Vaccine Immunology and Immunogen Discovery (CHAVI-ID), La Jolla, California, USA shane@lji.org.
authors.forename: Shane
authors.initials: S
authors.lastname: Crotty
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing / Q000096:biosynthesis* / Q000737:chemistry; D000918:Antibody Specificity; D000956:Antigens, Viral / Q000737:chemistry* / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology; D018604:Epitope Mapping; D000939:Epitopes / Q000737:chemistry / Q000276:immunology; D015870:Gene Expression; D057809:HEK293 Cells; D015483:HIV Antibodies / Q000096:biosynthesis* / Q000737:chemistry; D015658:HIV Infections / Q000276:immunology / Q000517:prevention & control* / Q000821:virology; D015497:HIV-1 / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D006801:Humans; D007114:Immunization; D007074:Immunoglobulin G / Q000096:biosynthesis* / Q000737:chemistry; D051379:Mice; D008958:Models, Molecular; D011485:Protein Binding; D015202:Protein Engineering; D055503:Protein Multimerization; D011947:Receptors, Antigen, B-Cell / Q000737:chemistry / Q000276:immunology; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D012995:Solubility; D054299:env Gene Products, Human Immunodeficiency Virus / Q000008:administration & dosage / Q000737:chemistry / Q000235:genetics / Q000276:immunology*
chemical_list: D057134:Antibodies, Neutralizing; D000956:Antigens, Viral; D000939:Epitopes; D015483:HIV Antibodies; D007074:Immunoglobulin G; D011947:Receptors, Antigen, B-Cell; D011994:Recombinant Proteins; D054299:env Gene Products, Human Immunodeficiency Virus