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 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 Cytolysis by CCR5-Using Human Immunodeficiency Virus Type 1 Envelope Glycoproteins Is Dependent on Membrane Fusion and Can Be Inhibited by High Levels of CD4 Expression

2003 ◽  
Vol 77 (12) ◽  
pp. 6645-6659 ◽  
Author(s):  
Jason A. LaBonte ◽  
Navid Madani ◽  
Joseph Sodroski
Keyword(s):  
Human Immunodeficiency Virus ◽  
T Cells ◽  
Membrane Fusion ◽  
Human Immunodeficiency Virus Type ◽  
Envelope Glycoprotein ◽  
Envelope Glycoproteins ◽  
Target Cells ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT T-tropic (X4) and dualtropic (R5X4) human immunodeficiency virus type 1 (HIV-1) envelope glycoproteins kill primary and immortalized CD4+ CXCR4+ T cells by mechanisms involving membrane fusion. However, because much of HIV-1 infection in vivo is mediated by M-tropic (R5) viruses whose envelope glycoproteins use CCR5 as a coreceptor, we tested a panel of R5 and R5X4 envelope glycoproteins for their ability to lyse CCR5+ target cells. As is the case for CXCR4+ target cells, HIV-1 envelope glycoproteins expressed by single-round HIV-1 vectors killed transduced CD4+ CCR5+ cells in a membrane fusion-dependent manner. Furthermore, a CD4-independent R5 HIV-1 envelope glycoprotein was able to kill CD4-negative target cells expressing CCR5, demonstrating that CD4 is not intrinsically required for the induction of death. Interestingly, high levels of CD4 expression protected cells from lysis and syncytium formation mediated by the HIV-1 envelope glycoproteins. Immunoprecipitation experiments showed that high levels of CD4 coexpression inhibited proteolytic processing of the HIV-1 envelope glycoprotein precursor gp160. This inhibition could be overcome by decreasing the CD4 binding ability of gp120. Studies were also undertaken to investigate the ability of virion-bound HIV-1 envelope glycoproteins to kill primary CD4+ T cells. However, neither X4 nor R5X4 envelope glycoproteins on noninfectious virions caused death in primary CD4+ T cells. These results demonstrate that the interaction of CCR5 with R5 HIV-1 envelope glycoproteins capable of inducing membrane fusion leads to cell lysis; overexpression of CD4 can inhibit cell killing by limiting envelope glycoprotein processing.

scholarly journals CD4-Induced T-20 Binding to Human Immunodeficiency Virus Type 1 gp120 Blocks Interaction with the CXCR4 Coreceptor

2004 ◽  
Vol 78 (10) ◽  
pp. 5448-5457 ◽  
Author(s):  
Wen Yuan ◽  
Stewart Craig ◽  
Zhihai Si ◽  
Michael Farzan ◽  
Joseph Sodroski
Keyword(s):  
Human Immunodeficiency Virus ◽  
Membrane Fusion ◽  
Heptad Repeat ◽  
V3 Loop ◽  
Repeat Region ◽  
Coreceptor Binding ◽  
Immunodeficiency Virus ◽  
Cxcr4 Coreceptor ◽  
Hiv 1

ABSTRACT The synthetic peptide T-20, which corresponds to a sequence within the C-terminal heptad repeat region (HR2) of the human immunodeficiency virus type 1 (HIV-1) gp41 envelope glycoprotein, potently inhibits viral membrane fusion and entry. Although T-20 is thought to bind the N-terminal heptad repeat region (HR1) of gp41 and interfere with gp41 conformational changes required for membrane fusion, coreceptor specificity determined by the V3 loop of gp120 strongly influences the sensitivity of HIV-1 variants to T-20. Here, we show that T-20 binds to the gp120 glycoproteins of HIV-1 isolates that utilize CXCR4 as a coreceptor in a manner determined by the sequences of the gp120 V3 loop. T-20 binding to gp120 was enhanced in the presence of soluble CD4. Analysis of T-20 binding to gp120 mutants with variable loop deletions and the reciprocal competition of T-20 and particular anti-gp120 antibodies suggested that T-20 interacts with a gp120 region near the base of the V3 loop. Consistent with the involvement of this region in coreceptor binding, T-20 was able to block the interaction of gp120-CD4 complexes with the CXCR4 coreceptor. These results help to explain the increased sensitivity of CXCR4-specific HIV-1 isolates to the T-20 peptide. Interactions between the gp41 HR2 region and coreceptor-binding regions of gp120 may also play a role in the function of the HIV-1 envelope glycoproteins.

scholarly journals Hemofiltrate CC Chemokine 1[9-74] Causes Effective Internalization of CCR5 and Is a Potent Inhibitor of R5-Tropic Human Immunodeficiency Virus Type 1 Strains in Primary T Cells and Macrophages

2002 ◽  
Vol 46 (4) ◽  
pp. 982-990 ◽  
Author(s):  
Jan Münch ◽  
Ludger Ständker ◽  
Stefan Pöhlmann ◽  
Frédéric Baribaud ◽  
Armin Papkalla ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
T Cells ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Proteolytic Processing ◽  
Cell Surface Expression ◽  
Cc Chemokine ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Proteolytic processing of the abundant plasmatic human CC chemokine 1 (HCC-1) generates a truncated form, HCC-1[9-74], which is a potent agonist of CCR1, CCR3, and CCR5; promotes calcium influx and chemotaxis of T lymphoblasts, monocytes, and eosinophils; and inhibits infection by CCR5-tropic human immunodeficiency virus type 1 (HIV-1) isolates. In the present study we demonstrate that HCC-1[9-74] interacts with the second external loop of CCR5 and inhibits replication of CCR5-tropic HIV-1 strains in both primary T cells and monocyte-derived macrophages. Low concentrations of the chemokine, however, frequently enhanced the replication of CCR5-tropic HIV-1 isolates but not the replication of X4-tropic HIV-1 isolates. Only HCC-1[9-74] and HCC-1[10-74], but not other HCC-1 length variants, displayed potent anti-HIV-1 activities. Fluorescence-activated cell sorter analysis revealed that HCC-1[9-74] caused up to 75% down-regulation of CCR5 cell surface expression, whereas RANTES (regulated on activation, normal T-cell expressed and secreted) achieved a reduction of only about 40%. Studies performed with green fluorescent protein-tagged CCR5 confirmed that both HCC-1[9-74] and RANTES, but not full-length HCC-1, mediated specific internalization of the CCR5 HIV-1 entry cofactor. Our results demonstrate that the interaction with HCC-1[9-74] causes effective intracellular sequestration of CCR5, but they also indicate that the effect of HCC-1[9-74] on viral replication is subject to marked cell donor- and HIV-1 isolate-dependent variations.

scholarly journals Nef Induces Multiple Genes Involved in Cholesterol Synthesis and Uptake in Human Immunodeficiency Virus Type 1-Infected T Cells

2005 ◽  
Vol 79 (15) ◽  
pp. 10053-10058 ◽  
Author(s):  
Angélique B. van ′t Wout ◽  
J. Victor Swain ◽  
Michael Schindler ◽  
Ushnal Rao ◽  
Melissa S. Pathmajeyan ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
T Cells ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Cholesterol Synthesis ◽  
Cholesterol Biosynthesis ◽  
Acetate Incorporation ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Several recent reports indicate that cholesterol might play an important role in human immunodeficiency virus type 1 (HIV-1) replication. We investigated the effects of HIV-1 infection on cholesterol biosynthesis and uptake using microarrays. HIV-1 increased gene expression of cholesterol genes in both transformed T-cell lines and primary CD4+ T cells. Consistent with our microarray data, 14C-labeled mevalonate and acetate incorporation was increased in HIV-1-infected cells. Our data also demonstrate that changes in cholesterol biosynthesis and uptake are only observed in the presence of functional Nef, suggesting that increased cholesterol synthesis may contribute to Nef-mediated enhancement of virion infectivity and viral replication.

scholarly journals Interleukin 7 Increases Human Immunodeficiency Virus Type 1 LAI-Mediated Fas-Induced T-Cell Death

2005 ◽  
Vol 79 (5) ◽  
pp. 3195-3199 ◽  
Author(s):  
Jean-Daniel Lelièvre ◽  
Frédéric Petit ◽  
Damien Arnoult ◽  
Jean-Claude Ameisen ◽  
Jérôme Estaquier
Keyword(s):  
Human Immunodeficiency Virus ◽  
T Cells ◽  
Cell Death ◽  
T Cell ◽  
Hiv Infection ◽  
Cell Infection ◽  
Interleukin 7 ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Fas-mediated T-cell death is known to occur during human immunodeficiency virus (HIV) infection. In this study, we found that HIV type 1 LAI (HIV-1LAI) primes CD8+ T cells from healthy donors for apoptosis, which occurs after Fas ligation. This effect is counteracted by a broad caspase inhibitor (zVAD-fmk). Fas-mediated cell death does not depend on CD8+ T-cell infection, because it occurred in the presence of reverse transcriptase inhibitors. However, purified CD8+ T cells are sensitive to Fas only in the presence of soluble CD4. Finally, we found that interleukin 7 (IL-7) increases Fas-mediated CD4+ and CD8+ T-cell death induced by HIV-1LAI. Since high levels of IL-7 are a marker of poor prognosis during HIV infection, our data suggest that enhancement of Fas-mediated T-cell death by HIV-1LAI and IL-7 is one of the mechanisms involved in progression to AIDS.

scholarly journals Differential Transmission of Human Immunodeficiency Virus Type 1 by Distinct Subsets of Effector Dendritic Cells

2002 ◽  
Vol 76 (15) ◽  
pp. 7812-7821 ◽  
Author(s):  
Rogier W. Sanders ◽  
Esther C. de Jong ◽  
Christopher E. Baldwin ◽  
Joost H. N. Schuitemaker ◽  
Martien L. Kapsenberg ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
T Cells ◽  
Dendritic Cells ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Virus Transmission ◽  
Viral Envelope ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Dendritic cells (DC) support human immunodeficiency virus type 1 (HIV-1) transmission by capture of the virus particle in the mucosa and subsequent transport to the draining lymph node, where HIV-1 is presented to CD4+ Th cells. Virus transmission involves a high-affinity interaction between the DC-specific surface molecule DC-SIGN and the viral envelope glycoprotein gp120 and subsequent internalization of the virus, which remains infectious. The mechanism of viral transmission from DC to T cells is currently unknown. Sentinel immature DC (iDC) develop into Th1-promoting effector DC1 or Th2-promoting DC2, depending on the activation signals. We studied the ability of these effector DC subsets to support HIV-1 transmission in vitro. Compared with iDC, virus transmission is greatly upregulated for the DC1 subset, whereas DC2 cells are inactive. Increased transmission by DC1 correlates with increased expression of ICAM-1, and blocking studies confirm that ICAM-1 expression on DC is important for HIV transmission. The ICAM-1-LFA-1 interaction is known to be important for immunological cross talk between DC and T cells, and our results indicate that this cell-cell contact is exploited by HIV-1 for efficient transmission.

scholarly journals Requirement for an Intact T-Cell Actin and Tubulin Cytoskeleton for Efficient Assembly and Spread of Human Immunodeficiency Virus Type 1

2007 ◽  
Vol 81 (11) ◽  
pp. 5547-5560 ◽  
Author(s):  
Clare Jolly ◽  
Ivonne Mitar ◽  
Quentin J. Sattentau
Keyword(s):  
Human Immunodeficiency Virus ◽  
T Cells ◽  
Plasma Membrane ◽  
T Cell ◽  
Immunodeficiency Virus ◽  
Fixed Cell ◽  
Cell Spread ◽  
Hiv 1 ◽  
Cell Cell

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) infection of CD4+ T cells leads to the production of new virions that assemble at the plasma membrane. Gag and Env accumulate in the context of lipid rafts at the inner and outer leaflets of the plasma membrane, respectively, forming polarized domains from which HIV-1 buds. HIV-1 budding can result in either release of cell-free virions or direct cell-cell spread via a virological synapse (VS). The recruitment of Gag and Env to these plasma membrane caps in T cells is poorly understood but may require elements of the T-cell secretory apparatus coordinated by the cytoskeleton. Using fixed-cell immunofluorescence labeling and confocal microscopy, we observed a high percentage of HIV-1-infected T cells with polarized Env and Gag in capped, lipid raft-like assembly domains. Treatment of infected T cells with inhibitors of actin or tubulin remodeling disrupted Gag and Env compartmentalization within the polarized raft-like domains. Depolymerization of the actin cytoskeleton reduced Gag release and viral infectivity, and actin and tubulin inhibitors reduced Env incorporation into virions. Live- and fixed-cell confocal imaging and assay of de novo DNA synthesis by real-time PCR allowed quantification of HIV-1 cell-cell transfer. Inhibition of actin and tubulin remodeling in infected cells interfered with cell-cell spread across a VS and reduced new viral DNA synthesis. Based on these data, we propose that HIV-1 requires both actin and tubulin components of the T-cell cytoskeleton to direct its assembly and budding and to elaborate a functional VS.

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