Conformational Changes of HIV-1 gp41 Membrane Proximal Ectodomain Region Induced by Broadly Neutralizing Antibodies

The HIV-1 envelope glycoprotein (Env) mediates host cell fusion and is the primary target for HIV-1 vaccine design. The Env undergoes a series of functionally important conformational rearrangements upon engagement of its host cell receptor, CD4. As the sole target for broadly neutralizing antibodies, our understanding of these transitions plays a critical role in vaccine immunogen design. Here, we review available experimental data interrogating the HIV-1 Env conformation and detail computational efforts aimed at delineating the series of conformational changes connecting these rearrangements. These studies have provided a structural mapping of prefusion closed, open, and transition intermediate structures, the allosteric elements controlling rearrangements, and state-to-state transition dynamics. The combination of these investigations and innovations in molecular modeling set the stage for advanced studies examining rearrangements at greater spatial and temporal resolution.

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Neutralizing Antibodies Targeting HIV-1 gp41

Viruses ◽

10.3390/v12111210 ◽

2020 ◽

Vol 12 (11) ◽

pp. 1210

Author(s):

Christophe Caillat ◽

Delphine Guilligay ◽

Guidenn Sulbaran ◽

Winfried Weissenhorn

Keyword(s):

Conformational Changes ◽

Neutralizing Antibodies ◽

Somatic Mutations ◽

Heptad Repeat ◽

Broadly Neutralizing Antibodies ◽

Vaccine Research ◽

Membrane Components ◽

And Function ◽

Hiv 1

HIV-1 vaccine research has obtained an enormous boost since the discovery of many broadly neutralizing antibodies (bnAbs) targeting all accessible sites on the HIV-1 envelope glycoprotein (Env). This in turn facilitated high-resolution structures of the Env glycoprotein in complex with bnAbs. Here we focus on gp41, its highly conserved heptad repeat region 1 (HR1), the fusion peptide (FP) and the membrane-proximal external region (MPER). Notably, the broadest neutralizing antibodies target MPER. Both gp41 HR1 and MPER are only fully accessible once receptor-induced conformational changes have taken place, although some studies suggest access to MPER in the close to native Env conformation. We summarize the data on the structure and function of neutralizing antibodies targeting gp41 HR1, FP and MPER and we review their access to Env and their complex formation with gp41 HR1, MPER peptides and FP within native Env. We further discuss MPER bnAb binding to lipids and the role of somatic mutations in recognizing a bipartite epitope composed of the conserved MPER sequence and membrane components. The problematic of gp41 HR1 access and MPER bnAb auto- and polyreactivity is developed in the light of inducing such antibodies by vaccination.

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Antibodies Elicited by Multiple Envelope Glycoprotein Immunogens in Primates Neutralize Primary Human Immunodeficiency Viruses (HIV-1) Sensitized by CD4-Mimetic Compounds

Journal of Virology ◽

10.1128/jvi.03211-15 ◽

2016 ◽

Vol 90 (10) ◽

pp. 5031-5046 ◽

Cited By ~ 21

Author(s):

Navid Madani ◽

Amy M. Princiotto ◽

David Easterhoff ◽

Todd Bradley ◽

Kan Luo ◽

...

Keyword(s):

Monoclonal Antibodies ◽

Small Molecule ◽

Conformational Changes ◽

Neutralizing Antibodies ◽

Vaccine Development ◽

Protective Efficacy ◽

Effective Vaccine ◽

Broadly Neutralizing Antibodies ◽

Variable Regions ◽

Hiv 1

ABSTRACTThe human immunodeficiency virus (HIV-1) envelope glycoproteins (Env) mediate virus entry through a series of complex conformational changes triggered by binding to the receptors CD4 and CCR5/CXCR4. Broadly neutralizing antibodies that recognize conserved Env epitopes are thought to be an important component of a protective immune response. However, to date, HIV-1 Env immunogens that elicit broadly neutralizing antibodies have not been identified, creating hurdles for vaccine development. Small-molecule CD4-mimetic compounds engage the CD4-binding pocket on the gp120 exterior Env and induce Env conformations that are highly sensitive to neutralization by antibodies, including antibodies directed against the conserved Env region that interacts with CCR5/CXCR4. Here, we show that CD4-mimetic compounds sensitize primary HIV-1 to neutralization by antibodies that can be elicited in monkeys and humans within 6 months by several Env vaccine candidates, including gp120 monomers. Monoclonal antibodies directed against the gp120 V2 and V3 variable regions were isolated from the immunized monkeys and humans; these monoclonal antibodies neutralized a primary HIV-1 only when the virus was sensitized by a CD4-mimetic compound. Thus, in addition to their direct antiviral effect, CD4-mimetic compounds dramatically enhance the HIV-1-neutralizing activity of antibodies that can be elicited with currently available immunogens. Used as components of microbicides, the CD4-mimetic compounds might increase the protective efficacy of HIV-1 vaccines.IMPORTANCEPreventing HIV-1 transmission is a high priority for global health. Eliciting antibodies that can neutralize transmitted strains of HIV-1 is difficult, creating problems for the development of an effective vaccine. We found that small-molecule CD4-mimetic compounds sensitize HIV-1 to antibodies that can be elicited in vaccinated humans and monkeys. These results suggest an approach to prevent HIV-1 sexual transmission in which a virus-sensitizing microbicide is combined with a vaccine.

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Broadly Neutralizing Antibodies (BNAbs): templates for HIV-1 vaccine design

Journal of Medical Discovery ◽

10.24262/jmd.2.4.17039 ◽

2017 ◽

Vol 2 (4) ◽

Cited By ~ 1

Author(s):

Lixin Yan ◽

◽

Lihong Liu ◽

Yilin Wang ◽

Xi Huang ◽

...

Keyword(s):

Neutralizing Antibodies ◽

Vaccine Design ◽

Broadly Neutralizing Antibodies ◽

Hiv 1

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Faculty Opinions recommendation of Enhanced clearance of HIV-1-infected cells by broadly neutralizing antibodies against HIV-1 in vivo.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.726369545.793518839 ◽

2016 ◽

Author(s):

Stephen J Kent

Keyword(s):

Neutralizing Antibodies ◽

Broadly Neutralizing Antibodies ◽

Infected Cells ◽

Hiv 1

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Faculty Opinions recommendation of Elimination of HIV-1-infected cells by broadly neutralizing antibodies.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.726190699.793517949 ◽

2016 ◽

Author(s):

Boris Matija Peterlin

Keyword(s):

Neutralizing Antibodies ◽

Broadly Neutralizing Antibodies ◽

Infected Cells ◽

Hiv 1

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A glycoside analog of mammalian oligomannose formulated with a TLR4-stimulating adjuvant elicits HIV-1 cross-reactive antibodies

Scientific Reports ◽

10.1038/s41598-021-84116-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jean-François Bruxelle ◽

Tess Kirilenko ◽

Nino Trattnig ◽

Yiqiu Yang ◽

Matteo Cattin ◽

...

Keyword(s):

Transgenic Mice ◽

Envelope Protein ◽

Protein Sequence ◽

Neutralizing Antibodies ◽

Human Antibody ◽

Broadly Neutralizing Antibodies ◽

Specific Antibodies ◽

Strong Binding ◽

Hiv Envelope ◽

Hiv 1

AbstractThe occurrence of oligomannose-specific broadly neutralizing antibodies (bnAbs) has spurred efforts to develop immunogens that can elicit similar antibodies. Here, we report on the antigenicity and immunogenicity of a CRM197-conjugate of a previously reported oligomannose mimetic. Oligomannose-specific bnAbs that are less dependent on interactions with the HIV envelope protein sequence showed strong binding to the glycoconjugates, with affinities approximating those reported for their cognate epitope. The glycoconjugate is also recognized by inferred germline precursors of oligomannose-specific bnAbs, albeit with the expected low avidity, supporting its potential as an immunogen. Immunization of human-antibody transgenic mice revealed that only a TLR4-stimulating adjuvant formulation resulted in antibodies able to bind a panel of recombinant HIV trimers. These antibodies bound at relatively modest levels, possibly explaining their inability to neutralize HIV infectivity. Nevertheless, these findings contribute further to understanding conditions for eliciting HIV-cross-reactive oligomannose-specific antibodies and inform on next steps for improving on the elicited response.

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Embracing diversity: how can broadly neutralizing antibodies effectively target a diverse HIV-1 reservoir?

Current Opinion in Pharmacology ◽

10.1016/j.coph.2020.10.004 ◽

2020 ◽

Vol 54 ◽

pp. 173-178

Author(s):

Andrew Wilson ◽

Rebecca M Lynch

Keyword(s):

Neutralizing Antibodies ◽

Broadly Neutralizing Antibodies ◽

Hiv 1

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A Coreceptor-Mimetic Peptide Enhances the Potency of V3-Glycan Antibodies

Journal of Virology ◽

10.1128/jvi.01653-18 ◽

2018 ◽

Vol 93 (5) ◽

Author(s):

Ina Fetzer ◽

Meredith E. Davis-Gardner ◽

Matthew R. Gardner ◽

Barnett Alfant ◽

Jesse A. Weber ◽

...

Keyword(s):

Envelope Glycoprotein ◽

Neutralizing Antibodies ◽

Target Cells ◽

Broadly Neutralizing Antibodies ◽

Mimetic Peptide ◽

Heavy Chains ◽

Binding Domains ◽

C Terminus ◽

Gp120 Subunit ◽

Hiv 1

ABSTRACTBroadly neutralizing antibodies (bNAbs) target five major epitopes on the HIV-1 envelope glycoprotein (Env). The most potent bNAbs have median half-maximal inhibitory concentration (IC50) values in the nanomolar range, and the broadest bNAbs neutralize up to 98% of HIV-1 strains. The engineered HIV-1 entry inhibitor eCD4-Ig has greater breadth than bNAbs and similar potency. eCD4-Ig is markedly more potent than CD4-Ig due to its C-terminal coreceptor-mimetic peptide. Here we investigated whether the coreceptor-mimetic peptide mim6 improved the potency of bNAbs with different epitopes. We observed that when mim6 was appended to the C terminus of the heavy chains of bNAbs, this sulfopeptide improved the potency of all classes of bNAbs against HIV-1 isolates that are sensitive to neutralization by the sulfopeptide alone. However, mim6 did not significantly enhance neutralization of other isolates when appended to most classes of bNAbs, with one exception. Specifically, mim6 improved the potency of bNAbs of the V3-glycan class, including PGT121, PGT122, PGT128, and 10-1074, by an average of 2-fold for all HIV-1 isolates assayed. Despite this difference, 10-1074 does not induce exposure of the coreceptor-binding site, and addition of mim6 to 10-1074 did not promote shedding of the gp120 subunit of Env. Mixtures of 10-1074 and an Fc domain fused to mim6 neutralized less efficiently than a 10-1074/mim6 fusion, indicating that mim6 enhances the avidity of this fusion. Our data show that mim6 can consistently improve the potency of V3-glycan antibodies and suggest that these antibodies bind in an orientation that facilitates mim6 association with Env.IMPORTANCEHIV-1 requires both the cellular receptor CD4 and a tyrosine-sulfated coreceptor to infect its target cells. CD4-Ig is a fusion of the HIV-1-binding domains of CD4 with an antibody Fc domain. Previous studies have demonstrated that the potency of CD4-Ig is markedly increased by appending a coreceptor-mimetic sulfopeptide to its C terminus. We investigated whether this coreceptor-mimetic peptide improves the potency of broadly neutralizing antibodies (bNAbs) targeting five major epitopes on the HIV-1 envelope glycoprotein (Env). We observed that inclusion of the sulfopeptide dramatically improved the potency of all bNAb classes against isolates with more-open Env structures, typically those that utilize the coreceptor CXCR4. In contrast, the sulfopeptide improved only V3-glycan antibodies when neutralizing primary isolates, on average by 2-fold. These studies improve the potency of one class of bNAbs, show that coreceptor-mimetic sulfopeptides enhance neutralization through distinct mechanisms, and provide insight for the design of novel multispecific entry inhibitors.

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Limited evidence for a relationship between HIV-1 glycan shield features in early infection and the development of neutralization breadth

Journal of Virology ◽

10.1128/jvi.00797-21 ◽

2021 ◽

Author(s):

Yifan Li ◽

Hongjun Bai ◽

Eric Sanders-Buell ◽

Vincent Dussupt ◽

Samantha Townsley ◽

...

Keyword(s):

Neutralizing Antibodies ◽

Early Infection ◽

Broadly Neutralizing Antibodies ◽

Limited Evidence ◽

Founder Virus ◽

Vaccine Antigens ◽

Acute Hiv ◽

The Relationship ◽

Hiv 1 ◽

Reactive Antibody

Identifying if viral features present in acute HIV-1 infection predetermine the development of neutralization breadth is critical to vaccine design. Incorporating such features in vaccine antigens could initiate cross-reactive antibody responses that could sufficiently protect vaccinees from HIV-1 infection despite the uniqueness of each founder virus. To understand the relationship between Env determinants and the development of neutralization breadth, we focused on 197 individuals enrolled in two cohorts in Thailand and East Africa (RV144 and RV217) and followed since their diagnosis in acute or early HIV-1 infection. We analyzed the distribution of variable loop lengths and glycans as well as the predicted density of the glycan shield and compared these envelope features to the neutralization breadth data obtained three years after infection (n = 121). Our study revealed limited evidence for glycan shield features that associate with the development of neutralization breadth. While the glycan shield tended to be denser in participants who subsequently developed breadth, no significant relationship was found between the size of glycan holes and the development of neutralization breadth. The parallel analysis of 3,000 independent Env sequences showed no evidence of directional evolution of glycan shield features since the beginning of the epidemic. Together, our results highlight that glycan shield features in acute and early HIV-1 infection may not play a role determinant enough to dictate the development of neutralization breadth, and instead suggest that the glycan shield’s reactive properties that are associated with immune evasion may have a greater impact. IMPORTANCE A major goal of HIV-1 vaccine research is to design vaccine candidates that elicit potent broadly neutralizing antibodies (bnAbs). Different viral features have been associated with the development of broadly neutralizing antibodies, including the glycan shield on the surface of the HIV-1 Envelope (Env). Here, we analyzed data from two cohorts of individuals who were followed from early infection to several years after infection spanning multiple HIV-1 subtypes. We compared Env glycan features in HIV-1 sequences obtained in early infection to the potency and breadth of neutralizing antibodies measured one to three years after infection. We found limited evidence of glycan shield properties that associate with the development of neutralization breadth in these cohorts. These results may have important implications for antigen design in future vaccine strategies and emphasize that HIV-1 vaccines will need to rely on a complex set of properties to elicit neutralization breadth.

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