scholarly journals Neutralizing antibodies to human immunodeficiency virus type-1 gp120 induce envelope glycoprotein subunit dissociation.

1996 ◽  
Vol 183 (2) ◽  
pp. 473-484 ◽  
Author(s):  
P Poignard ◽  
T Fouts ◽  
D Naniche ◽  
J P Moore ◽  
Q J Sattentau
Keyword(s):  
Human Immunodeficiency Virus ◽  
Conformational Changes ◽  
Neutralizing Antibodies ◽  
Viral Envelope ◽  
Subunit Dissociation ◽  
Immunodeficiency Virus ◽  
Gp120 Molecule ◽  
Cd4 Binding Site ◽  
Hiv Neutralization

The spectrum of the anti-human immunodeficiency virus (HIV) neutralizing immune response has been analyzed by the production and characterization of monoclonal antibodies (mAbs) to the viral envelope glycoproteins, gp41 and gp120. Little is known, however, about the neutralization mechanism of these antibodies. Here we show that the binding of a group of neutralizing mAbs that react with regions of the gp120 molecule associated with and including the V2 and V3 loops, the C4 domain and supporting structures, induce the dissociation of gp120 from gp41 on cells infected with the T cell line-adapted HIV-1 molecular clone Hx10. Similar to soluble receptor-induced dissociation of gp120 from gp41, the antibody-induced dissociation is dose- and time-dependent. By contrast, mAbs binding to discontinuous epitopes overlapping the CD4 binding site do not induce gp120 dissociation, implying that mAb induced conformational changes in gp120 are epitope specific, and that HIV neutralization probably involves several mechanisms.

scholarly journals Cyanovirin-N Binds to gp120 To Interfere with CD4-Dependent Human Immunodeficiency Virus Type 1 Virion Binding, Fusion, and Infectivity but Does Not Affect the CD4 Binding Site on gp120 or Soluble CD4-Induced Conformational Changes in gp120

1999 ◽  
Vol 73 (5) ◽  
pp. 4360-4371 ◽  
Author(s):  
Mark T. Esser ◽  
Toshiyuki Mori ◽  
Isabelle Mondor ◽  
Quentin J. Sattentau ◽  
Barna Dey ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Conformational Changes ◽  
Target Cell ◽  
Envelope Glycoprotein ◽  
Target Cells ◽  
Immunodeficiency Virus ◽  
Cd4 Binding Site ◽  
Hiv 1 ◽  
Soluble Cd4

ABSTRACT Cyanovirin-N (CV-N), an 11-kDa protein isolated from the cyanobacterium Nostoc ellipsosporum, potently inactivates diverse strains of human immunodeficiency virus type 1 (HIV-1), HIV-2, and simian immunodeficiency virus. While it has been well established that the viral surface envelope glycoprotein gp120 is a molecular target of CV-N, the detailed mechanism of action is of further interest. We compared matched native and CV-N-treated virus preparations in a panel of assays that measure viral replication, assessing successive stages of the viral life cycle. CV-N-treated virions failed to infect cells as detected by p24 production and quantitative PCR for HIV-1 reverse transcription products, whereas treatment of the target cells did not block infection, confirming that CV-N acts at the level of the virus, not the target cell, to abort the initial infection process. Compared to native HIV-1 preparations, CV-N-treated HIV-1 virions showed impaired CD4-dependent binding to CD4+ T cells and did not mediate “fusion from without” of CD4+ target cells. CV-N also blocked HIV envelope glycoprotein Env-induced, CD4-dependent cell-cell fusion. Mapping studies with monoclonal antibodies (MAbs) to defined epitopes on the HIV-1 envelope glycoprotein indicated that CV-N binds to gp120 in a manner that does not occlude or alter the CD4 binding site or V3 loop or other domains on gp120 recognized by defined MAbs and does not interfere with soluble CD4-induced conformational changes in gp120. Binding of CV-N to soluble gp120 or virions inhibited subsequent binding of the unique neutralizing MAb 2G12, which recognizes a glycosylation-dependent epitope. However, prior binding of 2G12 MAb to gp120 did not block subsequent binding by CV-N. These results help clarify the mechanism of action of CV-N and suggest that the compound may act in part by preventing essential interactions between the envelope glycoprotein and target cell receptors. This proposed mechanism is consistent with the extensive activity profile of CV-N against numerous isolates of HIV-1 and other lentiviruses and supports the potential broad utility of this protein as a microbicide to prevent the sexual transmission of HIV.

scholarly journals Characterization of the Multiple Conformational States of Free Monomeric and Trimeric Human Immunodeficiency Virus Envelope Glycoproteins after Fixation by Cross-Linker

2006 ◽  
Vol 80 (14) ◽  
pp. 6725-6737 ◽  
Author(s):  
Wen Yuan ◽  
Jessica Bazick ◽  
Joseph Sodroski
Keyword(s):  
Human Immunodeficiency Virus ◽  
Receptor Binding ◽  
Neutralizing Antibodies ◽  
Conformational Flexibility ◽  
Envelope Glycoproteins ◽  
Conformational States ◽  
Immunodeficiency Virus ◽  
Hiv 1 ◽  
Trimeric Envelope

ABSTRACT The human immunodeficiency virus type 1 (HIV-1) gp120 exterior and gp41 transmembrane envelope glycoproteins assemble into trimers on the virus surface that represent potential targets for antibodies. Potent neutralizing antibodies bind the monomeric gp120 glycoprotein with small changes in entropy, whereas unusually large decreases in entropy accompany gp120 binding by soluble CD4 and less potent neutralizing antibodies. The high degree of conformational flexibility in the free gp120 molecule implied by these observations has been suggested to contribute to masking the trimer from antibodies that recognize the gp120 receptor-binding regions. Here we use cross-linking and recognition by antibodies to investigate the conformational states of gp120 monomers and soluble and cell surface forms of the trimeric HIV-1 envelope glycoproteins. The fraction of monomeric and trimeric envelope glycoproteins able to be recognized after fixation was inversely related to the entropic changes associated with ligand binding. In addition, fixation apparently limited the access of antibodies to the V3 loop and gp41-interactive surface of gp120 only in the context of trimeric envelope glycoproteins. The results support a model in which the unliganded monomeric and trimeric HIV-1 envelope glycoproteins sample several different conformations. Depletion of particular fixed conformations by antibodies allowed characterization of the relationships among the conformational states. Potent neutralizing antibodies recognize the greatest number of conformations and therefore can bind the virion envelope glycoproteins more rapidly and completely than weakly neutralizing antibodies. Thus, the conformational flexibility of the HIV-1 envelope glycoproteins creates thermodynamic and kinetic barriers to neutralization by antibodies directed against the receptor-binding regions of gp120.

scholarly journals Mutations in gp120 Contribute to the Resistance of Human Immunodeficiency Virus Type 1 to Membrane-Anchored C-Peptide maC46

2009 ◽  
Vol 83 (10) ◽  
pp. 4844-4853 ◽  
Author(s):  
Felix G. Hermann ◽  
Lisa Egerer ◽  
Frances Brauer ◽  
Christian Gerum ◽  
Harald Schwalbe ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Conformational Changes ◽  
Viral Envelope ◽  
Heptad Repeat ◽  
Systematic Analysis ◽  
C Peptide ◽  
Helix Bundle ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Binding of the human immunodeficiency virus (HIV) envelope glycoprotein (Env) to the cellular CD4 receptor and a chemokine coreceptor initiates a series of conformational changes in the Env subunits gp120 and gp41. Eventually, the trimeric gp41 folds into a six-helix bundle, thereby inducing fusion of the viral and cellular membranes. C peptides derived from the C-terminal heptad repeat (CHR) of gp41 are efficient entry inhibitors as they block the six-helix bundle formation. Previously, we developed a membrane-anchored C peptide (maC46) expressed from a retroviral vector that also shows high activity against virus strains resistant to enfuvirtide (T-20), an antiviral C peptide approved for clinical use. Here, we present a systematic analysis of mutations in Env that confer resistance of HIV type 1 (HIV-1) to maC46. We selected an HIV-1 BaL strain with 10-fold reduced sensitivity to maC46 (BaL_C46) by passaging virus for nearly 200 days in the presence of gradually increasing concentrations of maC46. In comparison to wild-type BaL, BaL_C46 had five mutations at highly conserved positions in Env, three in gp120, one in the N-terminal heptad-repeat (NHR), and one in the CHR of gp41. No mutations were found in the NHR domain around the GIV motif that are known to cause resistance to enfuvirtide. Instead, maC46 resistance was found to depend on complementary mutations in the NHR and CHR that considerably favor binding of the mutated NHR to the mutated CHR over binding to maC46. In addition, resistance was highly dependent on mutations in gp120 that accelerated entry. Taken together, resistance to maC46 did not develop readily and required multiple cooperating mutations at conserved positions of the viral envelope glycoproteins gp120 and gp41.

scholarly journals CD4 Binding Site Antibodies Inhibit Human Immunodeficiency Virus gp120 Envelope Glycoprotein Interaction with CCR5

2003 ◽  
Vol 77 (1) ◽  
pp. 713-718 ◽  
Author(s):  
Aarti Raja ◽  
Miro Venturi ◽  
Peter Kwong ◽  
Joseph Sodroski
Keyword(s):  
Human Immunodeficiency Virus ◽  
Binding Site ◽  
Chemokine Receptors ◽  
Neutralizing Antibodies ◽  
Natural Infection ◽  
Cell Receptor ◽  
Host Cell Receptor ◽  
Immunodeficiency Virus ◽  
Cd4 Binding Site ◽  
Hiv 1

ABSTRACT The human immunodeficiency virus type 1 (HIV-1) gp120 exterior glycoprotein is conformationally flexible. Upon binding the host cell receptor, CD4, gp120 assumes a conformation that is able to bind the chemokine receptors CCR5 or CXCR4, which act as coreceptors for the virus. CD4-binding-site (CD4BS) antibodies are neutralizing antibodies elicited during natural infection that are directed against gp120 epitopes that overlap the binding site for CD4. Recent studies (S. H. Xiang et al., J. Virol. 76:9888-9899, 2002) suggest that CD4BS antibodies recognize conformations of gp120 distinct from the CD4-bound conformation. This predicts that the binding of CD4BS antibodies will inhibit chemokine receptor binding. Here, we show that Fab fragments and complete immunoglobulin molecules of CD4BS antibodies inhibit CD4-independent gp120 binding to CCR5 and cell-cell fusion mediated by CD4-independent HIV-1 envelope glycoproteins. These results are consistent with a model in which the binding of CD4BS antibodies limits the ability of gp120 to assume a conformation required for coreceptor binding.

scholarly journals HR-2 Mutations in Human Immunodeficiency Virus Type 1 gp41 Restore Fusion Kinetics Delayed by HR-1 Mutations That Cause Clinical Resistance to Enfuvirtide

2009 ◽  
Vol 83 (7) ◽  
pp. 2989-2995 ◽  
Author(s):  
Neelanjana Ray ◽  
Leslie A. Blackburn ◽  
Robert W. Doms
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Neutralizing Antibodies ◽  
Drug Binding ◽  
Viral Envelope ◽  
Clinical Resistance ◽  
Immunodeficiency Virus

ABSTRACT Enfuvirtide (ENF) prevents the entry of human immunodeficiency virus type 1 (HIV-1) into cells by binding to the HR-1 region of the viral envelope (Env) protein gp41 subunit. Resistance to ENF arises via mutations in the drug binding site in HR-1. In addition, HR-2 mutations are commonly observed in ENF-resistant Env proteins, though their role remains unclear. We explored the mechanistic basis for clinical resistance to ENF and the role of HR-2 mutations. Using panels of ENF resistance-associated mutants for two patients, we found that mutations in HR-1 slowed the fusion kinetics and that mutations in HR-2 restored fusion rates. We assessed the differences in the rates of fusion of these mutants from a temperature-arrested state and observed similar trends, suggesting that the step of delay occurs after coreceptor engagement. Sensitivity to neutralizing antibodies was unchanged by the HR-1 and HR-2 mutants in each panel. Since this result was in contrast to those of a previous in vitro analysis where enhanced sensitivity to neutralization was demonstrated for heterologous Envs with ENF resistance-associated HR-1 changes, we examined the context dependence of HR-1 and HR-2 mutations by transferring the mutations seen in one patient into the Env context of another. These studies revealed that some, but not all, HR-1 mutations, when placed out of context (i.e., in a patient Env where they did not originally arise), enhance sensitivity to neutralizing antibodies. However, in most cases, HR-1 mutations in ENF-treated patients evolve in a manner that preserves pretreatment neutralization sensitivity so as to evade the pressures of the immune system.

scholarly journals Mechanism of Human Immunodeficiency Virus Type 1 Resistance to Monoclonal Antibody b12 That Effectively Targets the Site of CD4 Attachment

2009 ◽  
Vol 83 (21) ◽  
pp. 10892-10907 ◽  
Author(s):  
Xueling Wu ◽  
Tongqing Zhou ◽  
Sijy O'Dell ◽  
Richard T. Wyatt ◽  
Peter D. Kwong ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Binding Site ◽  
Contact Surface ◽  
Neutralizing Antibodies ◽  
Viral Envelope ◽  
Contact Sites ◽  
Immunodeficiency Virus ◽  
Cd4 Binding Site ◽  
Hiv 1

ABSTRACT The region of the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein gp120 that engages its primary cellular receptor CD4 forms a site of vulnerability to neutralizing antibodies. The monoclonal antibody b12 exploits the conservation and accessibility of the CD4-binding site to neutralize many, though not all, HIV-1 isolates. To understand the basis of viral resistance to b12, we used the atomic-level definition of b12-gp120 contact sites to study a panel of diverse circulating viruses. A combination of sequence analysis, computational modeling, and site-directed mutagenesis was used to determine the influence of amino acid variants on binding and neutralization by b12. We found that several substitutions within the dominant b12 contact surface, called the CD4-binding loop, mediated b12 resistance, and that these substitutions resided just proximal to the known CD4 contact surface. Hence, viruses varied in key b12 contact residues that are proximal to, but not part of, the CD4 contact surface. This explained how viral isolates were able to evade b12 neutralization while maintaining functional binding to CD4. In addition, some viruses were resistant to b12 despite minimal sequence variation at b12 contact sites. Such neutralization resistance usually could be reversed by alterations at residues thought to influence the quaternary configuration of the viral envelope spike. To design immunogens that elicit neutralizing antibodies directed to the CD4-binding site, researchers need to address the antigenic variation within this region of gp120 and the restricted access to the CD4-binding site imposed by the native configuration of the trimeric viral envelope spike.

scholarly journals Characterization of Simian-Human Immunodeficiency Virus Envelope Glycoprotein Epitopes Recognized by Neutralizing Antibodies from Infected Monkeys

1998 ◽  
Vol 72 (10) ◽  
pp. 8437-8445 ◽  
Author(s):  
Bijan Etemad-Moghadam ◽  
Gunilla B. Karlsson ◽  
Matilda Halloran ◽  
Ying Sun ◽  
Dominik Schenten ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Antibody Response ◽  
Envelope Glycoprotein ◽  
Neutralizing Antibodies ◽  
Neutralizing Antibody ◽  
Virus Envelope ◽  
Immunodeficiency Virus ◽  
Variable Loops

ABSTRACT We characterized human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein epitopes recognized by neutralizing antibodies from monkeys recently infected by molecularly cloned simian-human immunodeficiency virus (SHIV) variants. The early neutralizing antibody response in each infected animal was directed mainly against a single epitope. This primary neutralizing epitope, however, differed among individual monkeys infected by identical viruses. Two such neutralization epitopes were determined by sequences in the V2 and V3 loops of the gp120 envelope glycoprotein, while a third neutralization epitope, apparently discontinuous, was determined by both V2 and V3 sequences. These results indicate that the early neutralizing antibody response in SHIV-infected monkeys is monospecific and directed against epitopes composed of the gp120 V2 and V3 variable loops.

scholarly journals Quaternary Interaction of the HIV-1 Envelope Trimer with CD4 and Neutralizing Antibodies

Viruses ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1405
Author(s):  
Qingbo Liu ◽  
Peng Zhang ◽  
Paolo Lusso
Keyword(s):  
Binding Site ◽  
Conformational Changes ◽  
Neutralizing Antibodies ◽  
Current Knowledge ◽  
Viral Envelope ◽  
Host Cells ◽  
Initial Contact ◽  
Cd4 Receptor ◽  
Cd4 Binding Site ◽  
Hiv 1

The entry of HIV-1 into host cells is initiated by the interaction of the viral envelope (Env) spike with the CD4 receptor. During this process, the spike undergoes a series of conformational changes that eventually lead to the exposure of the fusion peptide located at the N-terminus of the transmembrane glycoprotein, gp41. Recent structural and functional studies have provided important insights into the interaction of Env with CD4 at various stages. However, a fine elucidation of the earliest events of CD4 contact and its immediate effect on the Env conformation remains a challenge for investigation. Here, we summarize the discovery of the quaternary nature of the CD4-binding site in the HIV-1 Env and the role of quaternary contact in the functional interaction with the CD4 receptor. We propose two models for this initial contact based on the current knowledge and discuss how a better understanding of the quaternary interaction may lead to improved immunogens and antibodies targeting the CD4-binding site.

scholarly journals C-terminal tail of human immunodeficiency virus gp41: functionally rich and structurally enigmatic

2013 ◽  
Vol 94 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Jonathan D. Steckbeck ◽  
Anne-Sophie Kuhlmann ◽  
Ronald C. Montelaro
Keyword(s):  
Human Immunodeficiency Virus ◽  
Neutralizing Antibodies ◽  
Viral Envelope ◽  
Type I ◽  
Virion Incorporation ◽  
Immunodeficiency Virus ◽  
Aids Vaccines ◽  
Env Protein ◽  
Immunodeficiency Syndrome ◽  
And Function

The human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS) pandemic is amongst the most important current worldwide public health threats. While much research has been focused on AIDS vaccines that target the surface viral envelope (Env) protein, including gp120 and the gp41 ectodomain, the C-terminal tail (CTT) of gp41 has received relatively little attention. Despite early studies highlighting the immunogenicity of a particular CTT sequence, the CTT has been classically portrayed as a type I membrane protein limited to functioning in Env trafficking and virion incorporation. Recent studies demonstrate, however, that the Env CTT has other important functions. The CTT has been shown to additionally modulate Env ectodomain structure on the cell and virion surface, affect Env reactivity and viral sensitivity to conformation-dependent neutralizing antibodies, and alter cell–cell and virus–cell fusogenicity of Env. This review provides an overview of the Env structure and function with a particular emphasis on the CTT and recent studies that highlight its functionally rich nature.

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