scholarly journals Structure of Simian Immunodeficiency Virus Envelope Spikes Bound with CD4 and Monoclonal Antibody 36D5

2017 ◽  
Vol 91 (16) ◽  
Author(s):  
Guiqing Hu ◽  
Jun Liu ◽  
Kenneth H. Roux ◽  
Kenneth A. Taylor
Keyword(s):  
Monoclonal Antibody ◽  
Immune System ◽  
Binding Site ◽  
Simian Immunodeficiency Virus ◽  
Conformational Dynamics ◽  
V3 Loop ◽  
Coreceptor Binding ◽  
Immunodeficiency Virus ◽  
Hiv 1 ◽  
Coreceptor Binding Site

ABSTRACT The human immunodeficiency virus type 1 (HIV-1)/simian immunodeficiency virus (SIV) envelope spike (Env) mediates viral entry into host cells. The V3 loop of the gp120 component of the Env trimer contributes to the coreceptor binding site and is a target for neutralizing antibodies. We used cryo-electron tomography to visualize the binding of CD4 and the V3 loop monoclonal antibody (MAb) 36D5 to gp120 of the SIV Env trimer. Our results show that 36D5 binds gp120 at the base of the V3 loop and suggest that the antibody exerts its neutralization effect by blocking the coreceptor binding site. The antibody does this without altering the dynamics of the spike motion between closed and open states when CD4 is bound. The interaction between 36D5 and SIV gp120 is similar to the interaction between some broadly neutralizing anti-V3 loop antibodies and HIV-1 gp120. Two conformations of gp120 bound with CD4 are revealed, suggesting an intrinsic dynamic nature of the liganded Env trimer. CD4 binding substantially increases the binding of 36D5 to gp120 in the intact Env trimer, consistent with CD4-induced changes in the conformation of gp120 and the antibody binding site. Binding by MAb 36D5 does not substantially alter the proportions of the two CD4-bound conformations. The position of MAb 36D5 at the V3 base changes little between conformations, indicating that the V3 base serves as a pivot point during the transition between these two states. IMPORTANCE Glycoprotein spikes on the surfaces of SIV and HIV are the sole targets available to the immune system for antibody neutralization. Spikes evade the immune system by a combination of a thick layer of polysaccharide on the surface (the glycan shield) and movement between spike domains that masks the epitope conformation. Using SIV virions whose spikes were “decorated” with the primary cellular receptor (CD4) and an antibody (36D5) at part of the coreceptor binding site, we visualized multiple conformations trapped by the rapid freezing step, which were separated using statistical analysis. Our results show that the CD4-induced conformational dynamics of the spike enhances binding of the antibody.

scholarly journals Multiple Interactions across the Surface of the gp120 Core Structure Determine the Global Neutralization Resistance Phenotype of Human Immunodeficiency Virus Type 1

2003 ◽  
Vol 77 (14) ◽  
pp. 8061-8071 ◽  
Author(s):  
Peter Bouma ◽  
Maria Leavitt ◽  
Peng Fei Zhang ◽  
Igor A. Sidorov ◽  
Dimiter S. Dimitrov ◽  
...  
Keyword(s):  
Binding Site ◽  
V3 Loop ◽  
Functional Interactions ◽  
Coreceptor Binding ◽  
Immunodeficiency Virus ◽  
Gp120 Core ◽  
Hiv 1 ◽  
Coreceptor Binding Site ◽  
Primary Virus

ABSTRACT Resistance to neutralization is an important characteristic of primary isolates of human immunodeficiency virus type 1 (HIV-1) that relates to the potential for successful vaccination to prevent infection and use of immunotherapeutics for treatment of established infection. In order to further elucidate mechanisms responsible for neutralization resistance, we studied the molecular mechanisms that determine the resistance of the primary virus isolate of the strain HIV-1 MN to neutralization by soluble CD4 (sCD4). As is the case for the global neutralization resistance phenotype, sCD4 resistance depended upon sequences in the amino-terminal heptad repeat region of gp41 (HR1), as well as on multiple functional interactions within the envelope complex. The functional interactions that determined the resistance included interactions between the variable loop 1 and 2 (V1/V2) region and sequences in or near the CD4 binding site (CD4bs) and with the V3 loop. Additionally, the V3 loop region was found to interact functionally with sequences in the outer domain of gp120, distant from the CD4bs and coreceptor-binding site, as well as with a residue thought to be located centrally in the coreceptor-binding site. These and previous results provide the basis for a model by which functional signals that determine the neutralization resistance, high-infectivity phenotype depend upon interactions occurring across the surface of the gp120 core structure and involving variable loop structures and gp41. This model should be useful in efforts to define epitopes that may be important for primary virus neutralization.

scholarly journals Apoptosis of Bystander T Cells Induced by Human Immunodeficiency Virus Type 1 with Increased Envelope/Receptor Affinity and Coreceptor Binding Site Exposure

2004 ◽  
Vol 78 (9) ◽  
pp. 4541-4551 ◽  
Author(s):  
Geoffrey H. Holm ◽  
Chengsheng Zhang ◽  
Paul R. Gorry ◽  
Keith Peden ◽  
Dominique Schols ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
T Cells ◽  
Membrane Fusion ◽  
Binding Site ◽  
Receptor Affinity ◽  
Coreceptor Binding ◽  
Immunodeficiency Virus ◽  
Hiv 1 ◽  
Coreceptor Binding Site

ABSTRACT Apoptosis of uninfected bystander CD4+ T cells contributes to T-cell depletion during human immunodeficiency virus type 1 (HIV-1) pathogenesis. The viral and host mechanisms that lead to bystander apoptosis are not well understood. To investigate properties of the viral envelope glycoproteins (Env proteins) that influence the ability of HIV-1 to induce bystander apoptosis, we used molecularly cloned viruses that differ only in specific amino acids in Env. The ability of these strains to induce bystander apoptosis was tested in herpesvirus saimiri-immortalized primary CD4+ T cells (CD4/HVS), which resemble activated primary T cells. Changes in Env that increase affinity for CD4 or CCR5 or increase coreceptor binding site exposure enhanced the capacity of HIV-1 to induce bystander apoptosis following viral infection or exposure to nonreplicating virions. Apoptosis induced by HIV-1 virions was inhibited by CD4, CXCR4, and CCR5 antibodies or by the CXCR4 inhibitor AMD3100, but not the fusion inhibitor T20. HIV-1 virions with mutant Envs that bind CXCR4 but are defective for CD4 binding or membrane fusion induced apoptosis, whereas CXCR4 binding-defective mutants did not. These results demonstrate that HIV-1 virions induce apoptosis through a CXCR4- or CCR5-dependent pathway that does not require Env/CD4 signaling or membrane fusion and suggest that HIV-1 variants with increased envelope/receptor affinity or coreceptor binding site exposure may promote T-cell depletion in vivo by accelerating bystander cell death.

scholarly journals Relationships between CD4 Independence, Neutralization Sensitivity, and Exposure of a CD4-Induced Epitope in a Human Immunodeficiency Virus Type 1 Envelope Protein

2001 ◽  
Vol 75 (11) ◽  
pp. 5230-5239 ◽  
Author(s):  
Terri G. Edwards ◽  
Trevor L. Hoffman ◽  
Frédéric Baribaud ◽  
Stéphanie Wyss ◽  
Celia C. LaBranche ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Binding Site ◽  
Human Immunodeficiency Virus Type ◽  
Glycosylation Site ◽  
Neutralization Sensitivity ◽  
Coreceptor Binding ◽  
Immunodeficiency Virus ◽  
Hiv 1 ◽  
Coreceptor Binding Site

ABSTRACT A CD4-independent version of the X4 human immunodeficiency virus type 1 (HIV-1) HXBc2 envelope (Env) protein, termed 8x, mediates infection of CD4-negative, CXCR4-positive cells, binds directly to CXCR4 in the absence of CD4 due to constitutive exposure of a conserved coreceptor binding site in the gp120 subunit, and is more sensitive to antibody-mediated neutralization. To study the relationships between CD4 independence, neutralization sensitivity, and exposure of CD4-induced epitopes associated with the coreceptor binding site, we generated a large panel of Env mutants and chimeras between 8x and its CD4-dependent parent, HXBc2. We found that a frameshift mutation just proximal to the gp41 cytoplasmic domain in 8x Env was necessary but not sufficient for CD4 independence and led to increased exposure of the coreceptor binding site. In the presence of this altered cytoplasmic domain, single amino acid changes in either the 8x V3 (V320I) or V4/C4 (N386K) regions imparted CD4 independence, with other changes playing a modulatory role. The N386K mutation resulted in loss of an N-linked glycosylation site, but additional mutagenesis showed that it was the presence of a lysine rather than loss of the glycosylation site that contributed to CD4 independence. However, loss of the glycosylation site alone was sufficient to render Env neutralization sensitive, providing additional evidence that carbohydrate structures shield important neutralization determinants. Exposure of the CD4-induced epitope recognized by monoclonal antibody 17b and which overlaps the coreceptor binding site was highly sensitive to an R298K mutation at the base of the V3 loop and was often but not always associated with CD4 independence. Finally, while not all neutralization-sensitive Envs were CD4 independent, all CD4-independent Envs exhibited enhanced sensitivity to neutralization by HIV-1-positive human sera, indicating that the humoral immune response can exert strong selective pressure against the CD4-independent phenotype in vivo. Whether this can be used to advantage in designing more effective immunogens remains to be seen.

scholarly journals Elicitation of Cluster A and Co-Receptor Binding Site Antibodies Are Required to Eliminate HIV-1 Infected Cells

2020 ◽  
Vol 8 (5) ◽  
pp. 710 ◽  
Author(s):  
Guillaume Beaudoin-Bussières ◽  
Jérémie Prévost ◽  
Gabrielle Gendron-Lepage ◽  
Bruno Melillo ◽  
Junhua Chen ◽  
...  
Keyword(s):  
Binding Site ◽  
Envelope Glycoprotein ◽  
Antibody Dependent Cellular Cytotoxicity ◽  
Receptor Binding Site ◽  
Coreceptor Binding ◽  
Infected Cells ◽  
Cluster A ◽  
Hiv 1 ◽  
Coreceptor Binding Site

HIV-1-infected individuals raise a polyclonal antibody response targeting multiple envelope glycoprotein (Env) epitopes. Interestingly, two classes of non-neutralizing CD4-induced (CD4i) antibodies, present in the majority of HIV-1-infected individuals have been described to mediate antibody-dependent cellular cytotoxicity (ADCC) in the presence of small CD4 mimetic compounds (CD4mc). These antibodies recognize the coreceptor binding site (CoRBS) and the constant region one and two (C1C2 or inner domain cluster A) of the gp120. In combination with CD4mc they have been shown to stabilize an antibody-vulnerable Env conformation, known as State 2A. Here we evaluated the importance of these two families of Abs in ADCC responses by immunizing guinea pigs with gp120 immunogens that have been modified to elicit or not these types of antibodies. Underlying the importance of anti-CoRBS and anti-cluster A Abs in stabilizing State 2A, ADCC responses were only observed in the presence of these two types of CD4i antibodies. Altogether, our results suggest that these two families of CD4i antibodies must be taken into account when considering future strategies relying on the use of CD4mc to eliminate HIV-1-infected cells in vivo.

scholarly journals Changes in the Immunogenic Properties of Soluble gp140 Human Immunodeficiency Virus Envelope Constructs upon Partial Deletion of the Second Hypervariable Region

2003 ◽  
Vol 77 (4) ◽  
pp. 2310-2320 ◽  
Author(s):  
Indresh K. Srivastava ◽  
Keating VanDorsten ◽  
Lucia Vojtech ◽  
Susan W. Barnett ◽  
Leonidas Stamatatos
Keyword(s):  
Human Immunodeficiency Virus ◽  
Binding Site ◽  
Hypervariable Region ◽  
V3 Loop ◽  
Virus Envelope ◽  
Immunodeficiency Virus ◽  
Cd4 Binding Site ◽  
Hiv Envelope ◽  
Immunogenic Properties ◽  
Hiv 1

ABSTRACT Immunization of macaques with the soluble oligomeric gp140 form of the SF162 envelope (SF162gp140) or with an SF162gp140-derived construct lacking the central region of the V2 loop (ΔV2gp140) results in the generation of high titers of antibodies capable of neutralizing the homologous human immunodeficiency virus type 1 (HIV-1), SF162 virus (Barnett et al. J. Virol. 75 :5526-5540, 2001). However, the ΔV2gp140 immunogen is more effective than the SF162gp140 immunogen in eliciting the generation of antibodies capable of neutralizing heterologous HIV-1 isolates. This indicates that deletion of the V2 loop alters the immunogenicity of the SF162gp140 protein. The present studies were aimed at identifying the envelope regions whose immunogenicity is altered following V2 loop deletion. We report that the antibodies elicited by the SF162gp140 immunogen recognize elements of the V1, V2, and V3 loops, the CD4-binding site, and the C1 and C2 regions on the homologous SF162 gp120. With the exception of the V1 and V2 loops, the same regions are recognized on heterologous gp120 proteins. Surprisingly, although a minority of the SF162gp140-elicited antibodies target the V3 loop on the homologous gp120, the majority of the antibodies elicited by this immunogen that are capable of binding to the heterologous gp120s tested recognize their V3 loops. Deletion of the V2 loop has two effects. First, it alters the immunogenicity of the V3 and V1 loops, and second, it renders the C5 region immunogenic. Although deletion of the V2 loop does not result in an increase in the immunogenicity of the CD4-binding site per se, the relative ratio of anti-CD4-binding site to anti-V3 loop antibodies that bind to the heterologous gp120s tested is higher in sera collected from the ΔV2gp140-immunized animals than in the SF162gp140-immunized animals. Overall, our studies indicate that it is possible to alter the immunogenic structure of the HIV envelope by introducing specific modifications.

scholarly journals Heparan Sulfate Targets the HIV-1 Envelope Glycoprotein gp120 Coreceptor Binding Site

2005 ◽  
Vol 280 (22) ◽  
pp. 21353-21357 ◽  
Author(s):  
Romain R. Vivès ◽  
Anne Imberty ◽  
Quentin J. Sattentau ◽  
Hugues Lortat-Jacob
Keyword(s):  
Heparan Sulfate ◽  
Binding Site ◽  
Envelope Glycoprotein ◽  
Envelope Glycoprotein Gp120 ◽  
Coreceptor Binding ◽  
Glycoprotein Gp120 ◽  
Hiv 1 ◽  
Coreceptor Binding Site

scholarly journals The N-Terminal V3 Loop Glycan Modulates the Interaction of Clade A and B Human Immunodeficiency Virus Type 1 Envelopes with CD4 and Chemokine Receptors

2000 ◽  
Vol 74 (23) ◽  
pp. 11008-11016 ◽  
Author(s):  
Susan E. Malenbaum ◽  
David Yang ◽  
Lisa Cavacini ◽  
Marshall Posner ◽  
James Robinson ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Binding Site ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Chemokine Receptors ◽  
V3 Loop ◽  
Clade B ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT We investigated the underlying mechanism by which the highly conserved N-terminal V3 loop glycan of gp120 conferred resistance to neutralization of human immunodeficiency virus type 1 (HIV-1). We find that the presence or absence of this V3 glycan on clade A and B viruses accorded various degrees of susceptibility to neutralization by antibodies to the CD4 binding site, CD4-induced epitopes, and chemokine receptors. Our data suggest that this carbohydrate moiety on gp120 blocks access to the binding site for CD4 and modulates the chemokine receptor binding site of phenotypically diverse clade A and clade B isolates. Its presence also contributes to the masking of CD4-induced epitopes on clade B envelopes. These findings reveal a common mechanism by which diverse HIV-1 isolates escape immune recognition. Furthermore, the observation that conserved functional epitopes of HIV-1 are more exposed on V3 glycan-deficient envelope glycoproteins provides a basis for exploring the use of these envelopes as vaccine components.

scholarly journals Two Families of Env Antibodies Efficiently Engage Fc-Gamma Receptors and Eliminate HIV-1-Infected Cells

2018 ◽  
Vol 93 (3) ◽  
Author(s):  
Sai Priya Anand ◽  
Jérémie Prévost ◽  
Sophie Baril ◽  
Jonathan Richard ◽  
Halima Medjahed ◽  
...  
Keyword(s):  
Binding Site ◽  
Conformational Changes ◽  
Envelope Glycoproteins ◽  
Cellular Cytotoxicity ◽  
Fc Gamma Receptors ◽  
Coreceptor Binding ◽  
Infected Cells ◽  
Cluster A ◽  
Hiv 1 ◽  
Coreceptor Binding Site

ABSTRACTHIV-1 conceals epitopes of its envelope glycoproteins (Env) recognized by antibody (Ab)-dependent cellular cytotoxicity (ADCC)-mediating antibodies. These Abs, including anti-coreceptor binding site (CoRBS) and anti-cluster A antibodies, preferentially recognize Env in its “open” conformation. The binding of anti-CoRBS Abs has been shown to induce conformational changes that further open Env, allowing interaction of anti-cluster A antibodies. We explored the possibility that CoRBS Abs synergize with anti-cluster A Abs to engage Fc-gamma receptors to mediate ADCC. We found that binding of anti-CoRBS and anti-cluster A Abs to the same gp120 is required for interaction with soluble dimeric FcγRIIIa in enzyme-linked immunosorbent assays (ELISAs). We also found that Fc regions of both Abs are required to optimally engage FcγRIIIa and mediate robust ADCC. Taken together, our results indicate that these two families of Abs act together in a sequential and synergistic fashion to promote FcγRIIIa engagement and ADCC.IMPORTANCEThe “open” CD4-bound conformation of HIV-1 envelope glycoproteins is the primary target of antibody-dependent cellular cytotoxicity (ADCC)-mediating antibodies present in HIV-positive (HIV+) sera, such as anti-coreceptor binding site and anti-cluster A antibodies. Here we report that the binding of these two families of antibodies is required to engage FcγRIIIa and mediate ADCC.

scholarly journals Cryo-EM structure of a CD4-bound open HIV-1 envelope trimer reveals structural rearrangements of the gp120 V1V2 loop

2016 ◽  
Vol 113 (46) ◽  
pp. E7151-E7158 ◽  
Author(s):  
Haoqing Wang ◽  
Alexander A. Cohen ◽  
Rachel P. Galimidi ◽  
Harry B. Gristick ◽  
Grant J. Jensen ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Conformational Dynamics ◽  
Bound State ◽  
Structural Rearrangements ◽  
Cryo Electron Microscopy ◽  
Coreceptor Binding ◽  
Target Cell Membrane ◽  
Anti Hiv ◽  
Hiv 1 ◽  
Coreceptor Binding Site

The HIV-1 envelope (Env) glycoprotein, a trimer of gp120–gp41 heterodimers, relies on conformational flexibility to function in fusing the viral and host membranes. Fusion is achieved after gp120 binds to CD4, the HIV-1 receptor, and a coreceptor, capturing an open conformational state in which the fusion machinery on gp41 gains access to the target cell membrane. In the well-characterized closed Env conformation, the gp120 V1V2 loops interact at the apex of the Env trimer. Less is known about the structure of the open CD4-bound state, in which the V1V2 loops must rearrange and separate to allow access to the coreceptor binding site. We identified two anti–HIV-1 antibodies, the coreceptor mimicking antibody 17b and the gp120–gp41 interface-spanning antibody 8ANC195, that can be added as Fabs to a soluble native-like Env trimer to stabilize it in a CD4-bound conformation. Here, we present an 8.9-Å cryo-electron microscopy structure of a BG505 Env–sCD4–17b–8ANC195 complex, which reveals large structural rearrangements in gp120, but small changes in gp41, compared with closed Env structures. The gp120 protomers are rotated and separated in the CD4-bound structure, and the three V1V2 loops are displaced by ∼40 Å from their positions at the trimer apex in closed Env to the sides of the trimer in positions adjacent to, and interacting with, the three bound CD4s. These results are relevant to understanding CD4-induced conformational changes leading to coreceptor binding and fusion, and HIV-1 Env conformational dynamics, and describe a target structure relevant to drug design and vaccine efforts.

scholarly journals A Nucleotide Substitution in the tRNALys Primer Binding Site Dramatically Increases Replication of Recombinant Simian Immunodeficiency Virus Containing a Human Immunodeficiency Virus Type 1 Reverse Transcriptase

2002 ◽  
Vol 76 (11) ◽  
pp. 5803-5806 ◽  
Author(s):  
Kelly Soderberg ◽  
Lynn Denekamp ◽  
Sarah Nikiforow ◽  
Karen Sautter ◽  
Ronald C. Desrosiers ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Reverse Transcriptase ◽  
Binding Site ◽  
Simian Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Nucleotide Substitution ◽  
Primer Binding Site ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT A recombinant simian immunodeficiency virus (SIV) derived from strain 239 (SIVmac239) with reverse transcriptase (RT) sequences from human immunodeficiency virus type 1 (HIV-1) strain HXB2 was severely impaired for replication. Detectable p27Gag levels were not observed until day 65 and peak p27Gag levels were not reached until day 75 after transfection of CEMx174 cells with the recombinant DNA. Sequences from the latter time point did not contain amino acid substitutions in HIV-1 RT; however, a single nucleotide substitution (thymine to cytosine) was found at position eight of the SIV primer binding site. We engineered an RT/SHIV genome with the thymine-to-cytosine substitution, called RT/SHIV/TC, and observed dramatically faster replication kinetics than were observed with the parental RT/SHIV from which this variant was derived. RT/SHIV/TC provides an improved system for study of the impact of drug resistance mutations in HIV-1 RT in a relevant animal model.

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