Complexes of Fabs with a mimetic of the HIV-1 gp41 trimeric coiled-coil.

A series of mini-antibodies (monovalent and bivalent Fabs) targeting the conserved internal trimeric coiled-coil of the N-heptad repeat (N-HR) of HIV-1 gp41 has been previously constructed and reported. Crystal structures of two closely related monovalent Fabs, one (Fab 8066) broadly neutralizing across a wide panel of HIV-1 subtype B and C viruses, and the other (Fab 8062) non-neutralizing, representing the extremes of this series, were previously solved as complexes with 5-Helix, a gp41 pre-hairpin intermediate mimetic. Binding of these Fabs to covalently stabilized chimeric trimers of N-peptides of HIV-1 gp41 (named (CCIZN36)3 or 3-H) has now been investigated using X-ray crystallography, cryo-electron microscopy, and a variety of biophysical methods. Crystal structures of the complexes between 3-H and Fab 8066 and Fab 8062 were determined at 2.8 and 3.0 Å resolution, respectively. Although the structures of the complexes with the neutralizing Fab 8066 and its non-neutralizing counterpart Fab 8062 were generally similar, small differences between them could be correlated with the biological properties of these antibodies. The conformations of the corresponding CDRs of each antibody in the complexes with 3-H and 5-Helix are very similar. The adaptation to a different target upon complex formation is predominantly achieved by changes in the structure of the trimer of N-HR helices, as well as by adjustment of the orientation of the Fab molecule relative to the N-HR in the complex, via rigid-body movement. The structural data presented here indicate that binding of three Fabs 8062 with high affinity requires more significant changes in the structure of the N-HR trimer compared to binding of Fab 8066. A comparative analysis of the structures of Fabs complexed to different gp41 intermediate mimetics allows further evaluation of biological relevance for generation of neutralizing antibodies, as well as provides novel structural insights into immunogen design.

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Neutralizing antibodies induced by first-generation gp41-stabilized HIV-1 envelope trimers and nanoparticles

10.1101/2020.12.02.408328 ◽

2020 ◽

Author(s):

Sonu Kumar ◽

Xiaohe Lin ◽

Timothy Ngo ◽

Benjamin Shapero ◽

Cindy Sou ◽

...

Keyword(s):

Cell Sorting ◽

Neutralizing Antibodies ◽

First Generation ◽

Heptad Repeat ◽

X Ray ◽

X Ray Crystallography ◽

Clade C ◽

Next Generation Sequencing Ngs ◽

Generation Sequencing ◽

Hiv 1

ABSTRACTAntigen-specific B-cell sorting and next-generation sequencing (NGS) were combined to isolate HIV-1 neutralizing antibodies (NAbs) from mice and rabbits immunized with BG505 trimers and nanoparticles. Three mouse NAbs potently neutralize BG505.T332N and recognize a glycan epitope centered at the C3/V4 region, as revealed by electron microscopy (EM), x-ray crystallography, and epitope mapping. Three potent NAbs were sorted from rabbit B cells that target glycan holes on the BG505 envelope glycoprotein (Env) and account for a significant portion of autologous NAb response. We then determined a 3.4Å-resolution crystal structure for the clade C transmitted/founder Du172.17 Env with a redesigned heptad repeat 1 (HR1) bend. This clade C Env, as a soluble trimer and attached to a ferritin nanoparticle, along with a clade A Q482-d12 Env trimer, elicited distinct NAb responses in rabbits. Our study demonstrates that nanoparticles presenting gp41-stabilized trimers can induce potent NAb responses in mice and rabbits with Env-dependent breadth.TEASERMouse and rabbit NAbs elicited by gp41-stabilized trimers and nanoparticles neutralize autologous HIV-1 by targeting different epitopes

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Antibody elicited against the gp41 N-heptad repeat (NHR) coiled-coil can neutralize HIV-1 with modest potency but non-neutralizing antibodies also bind to NHR mimetics

Virology ◽

10.1016/j.virol.2008.04.005 ◽

2008 ◽

Vol 377 (1) ◽

pp. 170-183 ◽

Cited By ~ 37

Author(s):

Josh D. Nelson ◽

Heather Kinkead ◽

Florence M. Brunel ◽

Dan Leaman ◽

Richard Jensen ◽

...

Keyword(s):

Neutralizing Antibodies ◽

Coiled Coil ◽

Heptad Repeat ◽

Hiv 1

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Faculty Opinions recommendation of Sequential immunization with a subtype B HIV-1 envelope quasispecies partially mimics the in vivo development of neutralizing antibodies.

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

10.3410/f.9568956.11583060 ◽

2011 ◽

Author(s):

Eric Hunter ◽

Cynthia Derdeyn

Keyword(s):

Neutralizing Antibodies ◽

Subtype B ◽

Hiv 1

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Faculty Opinions recommendation of Sequential immunization with a subtype B HIV-1 envelope quasispecies partially mimics the in vivo development of neutralizing antibodies.

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

10.3410/f.9568956.10230054 ◽

2011 ◽

Author(s):

Luigi Buonaguro ◽

Maria Tagliamonte

Keyword(s):

Neutralizing Antibodies ◽

Subtype B ◽

Hiv 1

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Structural insights into the conformational plasticity of the full-length trimeric HIV-1 envelope glycoprotein precursor

10.1101/288472 ◽

2018 ◽

Author(s):

Shijian Zhang ◽

Wei Li Wang ◽

Shuobing Chen ◽

Maolin Lu ◽

Eden P. Go ◽

...

Keyword(s):

Viral Entry ◽

Envelope Glycoprotein ◽

Structural Data ◽

Full Length ◽

Heptad Repeat ◽

Structural Basis ◽

Glycoprotein Precursor ◽

Helix Bundle ◽

Conformational Plasticity ◽

Hiv 1

SummaryThe human immunodeficiency virus (HIV-1) envelope glycoprotein (Env) trimer mediates viral entry into cells and is the major target for the host antibody response. In infected cells, the mature Env [(gp120/gp41)3] is produced by cleavage of a trimeric gp160 precursor. Proteolytic cleavage decreases Env conformational flexibility, allowing the mature Env to resist antibody binding to conserved elements. The conformational plasticity of the Env precursor skews the humoral immune response towards the elicitation of ineffectual antibodies, contributing to HIV-1 persistence in the infected host. The structural basis for the plasticity of the Env precursor remains elusive. Here we use cryo-electron microscopy to visualize two coexisting conformational states of the full-length Env precursor at nominal resolutions of 5.5 and 8.0 Å. The State-P2 conformation features a three-helix bundle of the gp41 heptad repeat region in the core, but has disordered membrane-interactive regions. State-P1 trimers lack the three-helix bundle and instead retain ordered transmembrane and membrane-proximal external regions embracing a central cavity. Our structural data shed light on the unusual plasticity of the Env precursor and provide new clues to Env immunogen discovery.

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Removal of a Single N-Linked Glycan in Human Immunodeficiency Virus Type 1 gp120 Results in an Enhanced Ability To Induce Neutralizing Antibody Responses

Journal of Virology ◽

10.1128/jvi.01691-07 ◽

2007 ◽

Vol 82 (2) ◽

pp. 638-651 ◽

Cited By ~ 127

Author(s):

Yun Li ◽

Bradley Cleveland ◽

Igor Klots ◽

Bruce Travis ◽

Barbra A. Richardson ◽

...

Keyword(s):

Human Immunodeficiency Virus ◽

Neutralizing Antibodies ◽

Neutralizing Antibody ◽

Pronounced Increase ◽

Enhanced Sensitivity ◽

Subtype B ◽

Immunodeficiency Virus ◽

Hiv 1

ABSTRACT Glycans on human immunodeficiency virus (HIV) envelope protein play an important role in infection and evasion from host immune responses. To examine the role of specific glycans, we introduced single or multiple mutations into potential N-linked glycosylation sites in hypervariable regions (V1 to V3) of the env gene of HIV type 1 (HIV-1) 89.6. Three mutants tested showed enhanced sensitivity to soluble CD4. Mutant N7 (N197Q) in the carboxy-terminal stem of the V2 loop showed the most pronounced increase in sensitivity to broadly neutralizing antibodies (NtAbs), including those targeting the CD4-binding site (IgG1b12) and the V3 loop (447-52D). This mutant is also sensitive to CD4-induced NtAb 17b in the absence of CD4. Unlike the wild-type (WT) Env, mutant N7 mediates CD4-independent infection in U87-CXCR4 cells. To study the immunogenicity of mutant Env, we immunized pig-tailed macaques with recombinant vaccinia viruses, one expressing SIVmac239 Gag-Pol and the other expressing HIV-1 89.6 Env gp160 in WT or mutant forms. Animals were boosted 14 to 16 months later with simian immunodeficiency virus gag DNA and the cognate gp140 protein before intrarectal challenge with SHIV89.6P-MN. Day-of-challenge sera from animals immunized with mutant N7 Env had significantly higher and broader neutralizing activities than sera from WT Env-immunized animals. Neutralizing activity was observed against SHIV89.6, SHIV89.6P-MN, HIV-1 SF162, and a panel of subtype B primary isolates. Compared to control animals, immunized animals showed significant reduction of plasma viral load and increased survival after challenge, which correlated with prechallenge NtAb titers. These results indicate the potential advantages for glycan modification in vaccine design, although the role of specific glycans requires further examination.

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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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Probing the Structure of the HIV-1 Envelope Trimer Using Aspartate Scanning Mutagenesis

Journal of Virology ◽

10.1128/jvi.01426-20 ◽

2020 ◽

Vol 94 (21) ◽

Cited By ~ 1

Author(s):

Raksha Das ◽

Rohini Datta ◽

Raghavan Varadarajan

Keyword(s):

Cell Surface ◽

Viral Entry ◽

Fusion Peptide ◽

Heptad Repeat ◽

Subtype B ◽

Clade C ◽

Viral Surface ◽

Virion Surface ◽

Peptide Region ◽

Hiv 1

ABSTRACT HIV-1 envelope (Env) glycoprotein gp160 exists as a trimer of heterodimers on the viral surface. In most structures of the soluble ectodomain of trimeric HIV-1 envelope glycoprotein, the regions from 512 to 517 of the fusion peptide and from 547 to 568 of the N-heptad repeat are disordered. We used aspartate scanning mutagenesis of subtype B strain JRFL Env as an alternate method to probe residue burial in the context of cleaved, cell surface-expressed Env, as buried residues should be intolerant to substitution with Asp. The data are inconsistent with a fully disordered 547 to 568 stretch, as residues 548, 549, 550, 555, 556, 559, 562, and 566 to 569 are all sensitive to Asp substitution. In the fusion peptide region, residues 513 and 515 were also sensitive to Asp substitution, suggesting that the fusion peptide may not be fully exposed in native Env. gp41 is metastable in the context of native trimer. Introduction of Asp at residues that are exposed in the prefusion state but buried in the postfusion state is expected to destabilize the postfusion state and any intermediate states where the residue is buried. We therefore performed soluble CD4 (sCD4)-induced gp120 shedding experiments to identify Asp mutants at residues 551, 554 to 559, 561 to 567, and 569 that could prevent gp120 shedding. We also observed similar mutational effects on shedding for equivalent mutants in the context of clade C Env from isolate 4-2J.41. These substitutions can potentially be used to stabilize native-like trimer derivatives that are used as HIV-1 vaccine immunogens. IMPORTANCE In most crystal structures of the soluble ectodomain of the HIV-1 Env trimer, some residues in the fusion and N-heptad repeat regions are disordered. Whether this is true in the context of native, functional Env on the virion surface is not known. This knowledge may be useful for stabilizing Env in its prefusion conformation and will also help to improve understanding of the viral entry process. Burial of the charged residue Asp in a protein structure is highly destabilizing. We therefore used Asp scanning mutagenesis to probe the burial of apparently disordered residues in native Env and to examine the effect of mutations in these regions on Env stability and conformation as probed by antibody binding to cell surface-expressed Env, CD4-induced shedding of HIV-1 gp120, and viral infectivity studies. Mutations that prevent shedding can potentially be used to stabilize native-like Env constructs for use as vaccine immunogens.

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Topological analysis of the gp41 MPER on lipid bilayers relevant to the metastable HIV-1 envelope prefusion state

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1912427116 ◽

2019 ◽

Vol 116 (45) ◽

pp. 22556-22566 ◽

Cited By ~ 5

Author(s):

Yi Wang ◽

Pavanjeet Kaur ◽

Zhen-Yu J. Sun ◽

Mostafa A. Elbahnasawy ◽

Zahra Hayati ◽

...

Keyword(s):

Lipid Bilayers ◽

Neutralizing Antibodies ◽

Structural Changes ◽

Transmembrane Domain ◽

Topological Analysis ◽

Heptad Repeat ◽

Structural Topology ◽

Paramagnetic Resonance ◽

Viral Membrane ◽

Hiv 1

The membrane proximal external region (MPER) of HIV-1 envelope glycoprotein (gp) 41 is an attractive vaccine target for elicitation of broadly neutralizing antibodies (bNAbs) by vaccination. However, current details regarding the quaternary structural organization of the MPER within the native prefusion trimer [(gp120/41)3] are elusive and even contradictory, hindering rational MPER immunogen design. To better understand the structural topology of the MPER on the lipid bilayer, the adjacent transmembrane domain (TMD) was appended (MPER-TMD) and studied. Membrane insertion of the MPER-TMD was sensitive both to the TMD sequence and cytoplasmic residues. Antigen binding of MPER-specific bNAbs, in particular 10E8 and DH511.2_K3, was significantly impacted by the presence of the TMD. Furthermore, MPER-TMD assembly into 10-nm diameter nanodiscs revealed a heterogeneous membrane array comprised largely of monomers and dimers, as enumerated by bNAb Fab binding using single-particle electron microscopy analysis, arguing against preferential trimeric association of native MPER and TMD protein segments. Moreover, introduction of isoleucine mutations in the C-terminal heptad repeat to induce an extended MPER α-helical bundle structure yielded an antigenicity profile of cell surface-arrayed Env variants inconsistent with that found in the native prefusion state. In line with these observations, electron paramagnetic resonance analysis suggested that 10E8 inhibits viral membrane fusion by lifting the MPER N-terminal region out of the viral membrane, mandating the exposure of residues that would be occluded by MPER trimerization. Collectively, our data suggest that the MPER is not a stable trimer, but rather a dynamic segment adapted for structural changes accompanying fusion.

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