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Llorente García I, Marsh M. A biophysical perspective on receptor-mediated virus entry with a focus on HIV. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2020; 1862:183158. [PMID: 31863725 PMCID: PMC7156917 DOI: 10.1016/j.bbamem.2019.183158] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 12/12/2019] [Accepted: 12/13/2019] [Indexed: 12/14/2022]
Abstract
As part of their entry and infection strategy, viruses interact with specific receptor molecules expressed on the surface of target cells. The efficiency and kinetics of the virus-receptor interactions required for a virus to productively infect a cell is determined by the biophysical properties of the receptors, which are in turn influenced by the receptors' plasma membrane (PM) environments. Currently, little is known about the biophysical properties of these receptor molecules or their engagement during virus binding and entry. Here we review virus-receptor interactions focusing on the human immunodeficiency virus type 1 (HIV), the etiological agent of acquired immunodeficiency syndrome (AIDS), as a model system. HIV is one of the best characterised enveloped viruses, with the identity, roles and structure of the key molecules required for infection well established. We review current knowledge of receptor-mediated HIV entry, addressing the properties of the HIV cell-surface receptors, the techniques used to measure these properties, and the macromolecular interactions and events required for virus entry. We discuss some of the key biophysical principles underlying receptor-mediated virus entry and attempt to interpret the available data in the context of biophysical mechanisms. We also highlight crucial outstanding questions and consider how new tools might be applied to advance understanding of the biophysical properties of viral receptors and the dynamic events leading to virus entry.
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Affiliation(s)
| | - Mark Marsh
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
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2
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Colin P, Zhou Z, Staropoli I, Garcia-Perez J, Gasser R, Armani-Tourret M, Benureau Y, Gonzalez N, Jin J, Connell BJ, Raymond S, Delobel P, Izopet J, Lortat-Jacob H, Alcami J, Arenzana-Seisdedos F, Brelot A, Lagane B. CCR5 structural plasticity shapes HIV-1 phenotypic properties. PLoS Pathog 2018; 14:e1007432. [PMID: 30521629 PMCID: PMC6283471 DOI: 10.1371/journal.ppat.1007432] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 10/24/2018] [Indexed: 01/20/2023] Open
Abstract
CCR5 plays immune functions and is the coreceptor for R5 HIV-1 strains. It exists in diverse conformations and oligomerization states. We interrogated the significance of the CCR5 structural diversity on HIV-1 infection. We show that envelope glycoproteins (gp120s) from different HIV-1 strains exhibit divergent binding levels to CCR5 on cell lines and primary cells, but not to CD4 or the CD4i monoclonal antibody E51. This owed to differential binding of the gp120s to different CCR5 populations, which exist in varying quantities at the cell surface and are differentially expressed between different cell types. Some, but not all, of these populations are antigenically distinct conformations of the coreceptor. The different binding levels of gp120s also correspond to differences in their capacity to bind CCR5 dimers/oligomers. Mutating the CCR5 dimerization interface changed conformation of the CCR5 homodimers and modulated differentially the binding of distinct gp120s. Env-pseudotyped viruses also use particular CCR5 conformations for entry, which may differ between different viruses and represent a subset of those binding gp120s. In particular, even if gp120s can bind both CCR5 monomers and oligomers, impairment of CCR5 oligomerization improved viral entry, suggesting that HIV-1 prefers monomers for entry. From a functional standpoint, we illustrate that the nature of the CCR5 molecules to which gp120/HIV-1 binds shapes sensitivity to inhibition by CCR5 ligands and cellular tropism. Differences exist in the CCR5 populations between T-cells and macrophages, and this is associated with differential capacity to bind gp120s and to support viral entry. In macrophages, CCR5 structural plasticity is critical for entry of blood-derived R5 isolates, which, in contrast to prototypical M-tropic strains from brain tissues, cannot benefit from enhanced affinity for CD4. Collectively, our results support a role for CCR5 heterogeneity in diversifying the phenotypic properties of HIV-1 isolates and provide new clues for development of CCR5-targeting drugs.
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Affiliation(s)
- Philippe Colin
- Viral Pathogenesis Unit, Department of Virology, Institut Pasteur, Paris, France
- INSERM Unit U1108, Institut Pasteur, Paris, France
- Paris Diderot University, Sorbonne Paris Cité, Cellule Pasteur, Rue du Docteur Roux, Paris, France
| | - Zhicheng Zhou
- Viral Pathogenesis Unit, Department of Virology, Institut Pasteur, Paris, France
- INSERM Unit U1108, Institut Pasteur, Paris, France
| | - Isabelle Staropoli
- Viral Pathogenesis Unit, Department of Virology, Institut Pasteur, Paris, France
- INSERM Unit U1108, Institut Pasteur, Paris, France
| | | | - Romain Gasser
- Centre de Physiopathologie Toulouse-Purpan (CPTP), Université de Toulouse, CNRS, Inserm, UPS, Toulouse, France
| | - Marie Armani-Tourret
- Centre de Physiopathologie Toulouse-Purpan (CPTP), Université de Toulouse, CNRS, Inserm, UPS, Toulouse, France
| | - Yann Benureau
- Viral Pathogenesis Unit, Department of Virology, Institut Pasteur, Paris, France
- INSERM Unit U1108, Institut Pasteur, Paris, France
| | - Nuria Gonzalez
- AIDS Immunopathogenesis Unit, Instituto de Salud Carlos III, Madrid, Spain
| | - Jun Jin
- Viral Pathogenesis Unit, Department of Virology, Institut Pasteur, Paris, France
- INSERM Unit U1108, Institut Pasteur, Paris, France
| | - Bridgette J. Connell
- Grenoble Alpes University, CNRS, CEA, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Stéphanie Raymond
- Centre de Physiopathologie Toulouse-Purpan (CPTP), Université de Toulouse, CNRS, Inserm, UPS, Toulouse, France
- CHU de Toulouse, Laboratoire de Virologie, Toulouse, France
| | - Pierre Delobel
- Centre de Physiopathologie Toulouse-Purpan (CPTP), Université de Toulouse, CNRS, Inserm, UPS, Toulouse, France
- CHU de Toulouse, Service des Maladies Infectieuses et Tropicales, Toulouse, France
| | - Jacques Izopet
- Centre de Physiopathologie Toulouse-Purpan (CPTP), Université de Toulouse, CNRS, Inserm, UPS, Toulouse, France
- CHU de Toulouse, Laboratoire de Virologie, Toulouse, France
| | - Hugues Lortat-Jacob
- Grenoble Alpes University, CNRS, CEA, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Jose Alcami
- AIDS Immunopathogenesis Unit, Instituto de Salud Carlos III, Madrid, Spain
| | - Fernando Arenzana-Seisdedos
- Viral Pathogenesis Unit, Department of Virology, Institut Pasteur, Paris, France
- INSERM Unit U1108, Institut Pasteur, Paris, France
| | - Anne Brelot
- Viral Pathogenesis Unit, Department of Virology, Institut Pasteur, Paris, France
- INSERM Unit U1108, Institut Pasteur, Paris, France
| | - Bernard Lagane
- Viral Pathogenesis Unit, Department of Virology, Institut Pasteur, Paris, France
- INSERM Unit U1108, Institut Pasteur, Paris, France
- Centre de Physiopathologie Toulouse-Purpan (CPTP), Université de Toulouse, CNRS, Inserm, UPS, Toulouse, France
- * E-mail:
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IL-8 decreases HIV-1 transcription in peripheral blood lymphocytes and ectocervical tissue explants. J Acquir Immune Defic Syndr 2010; 54:463-9. [PMID: 20577090 DOI: 10.1097/qai.0b013e3181e5e12c] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
IL-8 is enhanced in the peripheral blood and lymphoid tissue of HIV-infected individuals, suggesting that IL-8 is important in the pathogenesis of HIV-1 infection and progression to AIDS. Characterizing the mechanisms of IL-8 regulation of HIV-1 replication may be relevant in addressing the role of IL-8 as a therapeutic target in HIV-1 infection. We evaluated replication of primary R5-tropic HIV-1 in peripheral blood lymphocytes and ectocervical tissue explants infected in vitro in the presence of physiological concentrations of IL-8 found in the serum and genital tract secretions of HIV-infected individuals. To identify the specific stages of the viral life cycle targeted by IL-8, we performed real-time polymerase chain reaction to detect HIV-1 reverse transcription, integration, and transcription. Early during the infection, IL-8 decreased HIV-1 reverse transcription and viral integration. This effect was transient, as on day 4 after infection, we detected no differences on HIV-1 DNA or proviral DNA in peripheral blood lymphocyte. IL-8 decreased HIV-1 transcription in both lymphocytes and ectocervical tissue explants. The decrease in viral RNA expression was associated with reduced HIV-1 replication, as measured by viral p24 release in the culture supernatants. This is the first report to suggest that IL-8 decreases replication of primary R5-tropic HIV-1 by transcriptional mechanisms.
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A V3 loop-dependent gp120 element disrupted by CD4 binding stabilizes the human immunodeficiency virus envelope glycoprotein trimer. J Virol 2010; 84:3147-61. [PMID: 20089638 DOI: 10.1128/jvi.02587-09] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human immunodeficiency virus (HIV-1) entry into cells is mediated by a trimeric complex consisting of noncovalently associated gp120 (exterior) and gp41 (transmembrane) envelope glycoproteins. The binding of gp120 to receptors on the target cell alters the gp120-gp41 relationship and activates the membrane-fusing capacity of gp41. Interaction of gp120 with the primary receptor, CD4, results in the exposure of the gp120 third variable (V3) loop, which contributes to binding the CCR5 or CXCR4 chemokine receptors. We show here that insertions in the V3 stem or polar substitutions in a conserved hydrophobic patch near the V3 tip result in decreased gp120-gp41 association (in the unliganded state) and decreased chemokine receptor binding (in the CD4-bound state). Subunit association and syncytium-forming ability of the envelope glycoproteins from primary HIV-1 isolates were disrupted more by V3 changes than those of laboratory-adapted HIV-1 envelope glycoproteins. Changes in the gp120 beta2, beta19, beta20, and beta21 strands, which evidence suggests are proximal to the V3 loop in unliganded gp120, also resulted in decreased gp120-gp41 association. Thus, a gp120 element composed of the V3 loop and adjacent beta strands contributes to quaternary interactions that stabilize the unliganded trimer. CD4 binding dismantles this element, altering the gp120-gp41 relationship and rendering the hydrophobic patch in the V3 tip available for chemokine receptor binding.
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Fromme BJ, Coetsee M, Van Der Watt P, Chan MC, Sperling KM, Katz AA, Flanagan CA. High-affinity binding of southern African HIV type 1 subtype C envelope protein, gp120, to the CCR5 coreceptor. AIDS Res Hum Retroviruses 2008; 24:1527-36. [PMID: 19018669 DOI: 10.1089/aid.2008.0105] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
HIV-1 subtype C is the fastest spreading subtype worldwide and predominantly uses the CCR5 coreceptor, showing minimal transition to the X4 phenotype. This raises the possibility that envelope proteins of HIV-1 subtype C have structural features that favor interaction with CCR5. Preference for CCR5 could arise from enhanced affinity of HIV-1 subtype C for CCR5. To test this, we have characterized the interaction of gp120 envelope proteins from HIV-1 subtype C clones with CD4 and CCR5. Recombinant gp120 proteins from isolates of HIV-1 subtypes B and C were expressed, purified, and assessed in a CD4 binding assay and a CCR5 chemokine competition binding assay. All gp120 proteins bound to CD4-expressing cells, except one, 97ZA347ts, which had Arg substituted for the Cys239 in the conserved C2 loop. Reconstitution of Cys239, using site-directed mutagenesis, restored CD4 binding, while introducing Arg or Ser into position 239 of the functional Du151 gp120 protein abrogated CD4 binding. This shows that the Cys228-Cys239 disulfide bond of gp120 is required for high-affinity binding to CD4. Recombinant gp120 proteins from two HIV-1 subtype B clones bound CCR5 in the presence of CD4, while gp120 from the X4-tropic, HxB2, clone did not bind CCR5. gp120 from two functional HIV-1 subtype C clones, Du151 and MOLE1, bound CCR5 with high affinity in the presence of CD4 and Du151 showed significant CCR5 binding in the absence of CD4. A gp120 from a nonfunctional subtype C clone had lower affinity for CCR5. These results indicate that HIV-1 subtype C proteins have high affinity for CCR5 with variable dependence on CD4.
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Affiliation(s)
- Bernhard J. Fromme
- MRC/UCT Research Group for Receptor Biology, University of Cape Town, Cape Town, South Africa
| | - Marla Coetsee
- MRC/UCT Research Group for Receptor Biology, University of Cape Town, Cape Town, South Africa
| | - Pauline Van Der Watt
- MRC/UCT Research Group for Receptor Biology, University of Cape Town, Cape Town, South Africa
| | - Mei-Chi Chan
- MRC/UCT Research Group for Receptor Biology, University of Cape Town, Cape Town, South Africa
| | - Karin M. Sperling
- MRC/UCT Research Group for Receptor Biology, University of Cape Town, Cape Town, South Africa
| | - Arieh A. Katz
- MRC/UCT Research Group for Receptor Biology, University of Cape Town, Cape Town, South Africa
- Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa
- Department of Clinical Laboratory Sciences, University of Cape Town, Cape Town, South Africa
| | - Colleen A. Flanagan
- MRC/UCT Research Group for Receptor Biology, University of Cape Town, Cape Town, South Africa
- School of Physiology, University of the Witwatersrand, Parktown, South Africa
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R5X4 viruses are evolutionary, functional, and antigenic intermediates in the pathway of a simian-human immunodeficiency virus coreceptor switch. J Virol 2008; 82:7089-99. [PMID: 18480460 DOI: 10.1128/jvi.00570-08] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To examine the pathway of the coreceptor switching of CCR5-using (R5) virus to CXCR4-using (X4) virus in simian-human immunodeficiency virus SHIV(SF162P3N)-infected rhesus macaque BR24, analysis was performed on variants present at 20 weeks postinfection, the time when the signature gp120 V3 loop sequence of the X4 switch variant was first detected by PCR. Unexpectedly, circulating and tissue variants with His/Ile instead of the signature X4 V3 His/Arg insertions predominated at this time point. Phylogenetic analysis of the sequences of the C2 conserved region to the V5 variable loop of the envelope (Env) protein showed that viruses bearing HI insertions represented evolutionary intermediates between the parental SHIV(SF162P3N) and the final X4 HR switch variant. Functional analyses demonstrated that the HI variants were phenotypic intermediates as well, capable of using both CCR5 and CXCR4 for entry. However, the R5X4 intermediate virus entered CCR5-expressing target cells less efficiently than the parental R5 strain and was more sensitive to both CCR5 and CXCR4 inhibitors than either the parental R5 or the final X4 virus. It was also more sensitive than the parental R5 virus to antibody neutralization, especially to agents directed against the CD4 binding site, but not as sensitive as the late X4 virus. Significantly, the V3 loop sequence that determined CXCR4 use also conferred soluble CD4 neutralization sensitivity. Collectively, the data illustrate that, similar to human immunodeficiency virus type 1 (HIV-1) infection in individuals, the evolution from CCR5 to CXCR4 usage in BR24 transitions through an intermediate phase with reduced virus entry and coreceptor usage efficiencies. The data further support a model linking an open envelope gp120 conformation, better CD4 binding, and expansion to CXCR4 usage.
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Entry coreceptor use and fusion inhibitor T20 sensitivity of dual-tropic R5X4 HIV-1 in primary macrophage infection. J Acquir Immune Defic Syndr 2008; 47:285-92. [PMID: 18197116 DOI: 10.1097/qai.0b013e31816520f6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Macrophages are important targets for HIV-1, and R5X4 strains play a central role in pathogenesis, especially in late-stage patients who may receive the fusion inhibitor T20 (enfuvirtide). Sensitivity to T20 varies markedly among HIV-1 strains and is influenced by viral and cellular factors that affect Env/CD4/coreceptor interactions. We addressed the relation between T20 inhibition and the pathway by which R5X4 HIV-1 infects primary macrophages, which express both coreceptors. In U87/CD4/coreceptor cells, T20 sensitivity for entry through CCR5 and CXCR4 was correlated. In macrophages, the proportion of total entry mediated by each coreceptor differed among isolates. Neither pathway was uniformly more or less sensitive to T20, however, nor did the proportion of entry mediated by each coreceptor predict T20 sensitivity. T20 sensitivity for macrophage infection overall correlated modestly with that for entry through CCR5 but not through CXCR4; however, unlike U87 cells, sensitivity of entry through CCR5 and CXCR4 was not correlated. These results suggest that strain-specific factors influence R5X4 T20 sensitivity regardless of the coreceptor used, an absence of systematic differences in efficiency by which R5X4 strains use the 2 coreceptors, and that efficiency and kinetics of interactions with CCR5 are central determinants of macrophage entry even when both pathways are utilized.
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Teeravechyan S, Suphaphiphat P, Essex M, Lee TH. Relative concordance of human immunodeficiency virus oligomeric and monomeric envelope in CCR5 coreceptor usage. Virology 2008; 370:443-50. [PMID: 17936869 DOI: 10.1016/j.virol.2007.09.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2007] [Revised: 09/11/2007] [Accepted: 09/11/2007] [Indexed: 10/22/2022]
Abstract
A major difference between binding and fusion assays commonly used to study the human immunodeficiency virus (HIV) envelope is the use of monomeric envelope for the former assay and oligomeric envelope for the latter. Due to discrepancies in their readouts for some mutants, envelope regions involved in CCR5 coreceptor usage were systematically studied to determine whether the discordance is due to inherent differences between the two assays or whether it genuinely reflects functional differences at each entry step. By adding the binding inhibitor TAK-779 to delay coreceptor binding kinetics in the fusion assay, the readouts were found comparable between the assays for the mutants analysed in this study. Our finding indicates that monomeric binding reflects oligomeric envelope-CCR5 interaction, thus discordant results between binding and fusion assays do not necessarily indicate differences in coreceptor usage by oligomeric envelope and monomeric gp120.
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Affiliation(s)
- Samaporn Teeravechyan
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, 651 Huntington Avenue, Boston, MA 02115, USA
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Melikyan GB, Platt EJ, Kabat D. The role of the N-terminal segment of CCR5 in HIV-1 Env-mediated membrane fusion and the mechanism of virus adaptation to CCR5 lacking this segment. Retrovirology 2007; 4:55. [PMID: 17686153 PMCID: PMC1995219 DOI: 10.1186/1742-4690-4-55] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2007] [Accepted: 08/08/2007] [Indexed: 02/05/2023] Open
Abstract
Background HIV-1 envelope glycoprotein (Env) induces membrane fusion as a result of sequential binding to CD4 and chemokine receptors (CCR5 or CXCR4). The critical determinants of CCR5 coreceptor function are the N-terminal domain (Nt) and the second extracellular loop. However, mutations in gp120 adapt HIV-1 to grow on cells expressing the N-terminally truncated CCR5(Δ18) (Platt et al., J. Virol. 2005, 79: 4357–68). Results We have functionally characterized the adapted Env (designated Env(NYP)) using a quantitative cell-cell fusion assay. The rate of fusion with target cells expressing wild-type CCR5 and the resistance to fusion inhibitors was virtually identical for wild-type Env and Env(NYP), implying that the coreceptor affinity had not increased as a result of adaptation. In contrast, Env(NYP)-induced fusion with cells expressing CCR5(Δ18) occurred at a slower rate and was extremely sensitive to the CCR5 binding inhibitor, Sch-C. Resistance to Sch-C drastically increased after pre-incubation of Env(NYP)- and CCR5(Δ18)-expressing cells at a temperature that was not permissive to fusion. This indicates that ternary Env(NYP)-CD4-CCR5(Δ18) complexes accumulate at sub-threshold temperature and that low-affinity interactions with the truncated coreceptor are sufficient for triggering conformational changes in the gp41 of Env(NYP) but not in wild-type Env. We also demonstrated that the ability of CCR5(Δ18) to support fusion and infection mediated by wild-type Env can be partially reconstituted in the presence of a synthetic sulfated peptide corresponding to the CCR5 Nt. Pre-incubation of wild-type Env- and CCR5(Δ18)-expressing cells with the sulfated peptide at sub-threshold temperature markedly increased the efficiency of fusion. Conclusion We propose that, upon binding the Nt region of CCR5, wild-type Env acquires the ability to productively engage the extracellular loop(s) of CCR5 – an event that triggers gp41 refolding and membrane merger. The adaptive mutations in Env(NYP) enable it to more readily release its hold on gp41, even when it interacts weakly with a severely damaged coreceptor in the absence of the sulfopeptide.
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Affiliation(s)
- Gregory B Melikyan
- Institute of Human Virology, University of Maryland School of Medicine.725 W. Lombard St., Baltimore, MD 21201, USA
| | - Emily J Platt
- Department of Biochemistry and Molecular Biology, Oregon Health and Science, University, Portland, OR 97239, USA
| | - David Kabat
- Department of Biochemistry and Molecular Biology, Oregon Health and Science, University, Portland, OR 97239, USA
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Margolin DH, Saunders EH, Bronfin B, de Rosa N, Axthelm MK, Goloubeva OG, Eapen S, Gelman RS, Letvin NL. Germinal center function in the spleen during simian HIV infection in rhesus monkeys. THE JOURNAL OF IMMUNOLOGY 2006; 177:1108-19. [PMID: 16818768 DOI: 10.4049/jimmunol.177.2.1108] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Infection with HIV-1, SIV, or simian HIV is associated with abnormalities in the number, size, and structure of germinal centers (GCs). To determine whether these histopathologic abnormalities are associated with abnormalities in Ab development, we analyzed nucleotide sequences of Igs from splenic GCs of simian HIV-infected macaques. Virus-specific GCs were identified in frozen splenic tissue sections by inverse immunohistochemistry using rHIV-1 gp120 as a probe. B cells from envelope-specific GCs were isolated from these sections using laser capture microdissection. Their Igs were amplified from cDNA using nested PCR, then cloned and sequenced. Nucleotide sequences were recovered from nine multimember clonal lineages. Within each lineage, sequences had similar V-D-J or V-J junctions but differed by somatic mutations distributed throughout the variable domain. The clones were highly mutated, similar to that previously reported for HIV-1-specific human IgG Abs. The average clone had 37 mutations in the V region, for a frequency of 0.11 mutations/base. The mutational pattern was strikingly nonrandom, with somatic mutations occurring preferentially at RGYW/WRCY hotspots. Transition mutations were favored over transversions, with C-->T and G-->A replacements together accounting for almost one-third of all mutations. Analysis of replacement and silent mutations in the framework and CDRs suggests that the Igs were subjected to affinity selection. These data demonstrate that the process of Ab maturation is not seriously disrupted in GCs during the early stages of immunodeficiency virus infection, and that Env-specific Igs developing in GCs are subject to extensive somatic mutation and profound selection pressures.
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Affiliation(s)
- David H Margolin
- Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, USA
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Wang S, Pal R, Mascola JR, Chou THW, Mboudjeka I, Shen S, Liu Q, Whitney S, Keen T, Nair BC, Kalyanaraman VS, Markham P, Lu S. Polyvalent HIV-1 Env vaccine formulations delivered by the DNA priming plus protein boosting approach are effective in generating neutralizing antibodies against primary human immunodeficiency virus type 1 isolates from subtypes A, B, C, D and E. Virology 2006; 350:34-47. [PMID: 16616287 DOI: 10.1016/j.virol.2006.02.032] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2005] [Revised: 01/20/2006] [Accepted: 02/09/2006] [Indexed: 10/24/2022]
Abstract
A major challenge in developing an HIV-1 vaccine is to identify immunogens and their delivery methods that can elicit broad neutralizing antibodies against primary isolates of different genetic subtypes. Recently, we demonstrated that priming with DNA vaccines expressing primary HIV-1 envelope glycoprotein (Env) followed by recombinant Env protein boosting was successful in generating positive neutralizing antibody responses against a clade B primary HIV-1 isolate, JR-FL, that was not easily neutralized. In the current study, we examined whether the DNA priming plus recombinant protein boosting approach delivering a polyvalent primary Env formulation was able to generate neutralizing antibodies against primary HIV-1 viral isolates from various genetic subtypes. New Zealand White rabbits were first immunized with DNA vaccines expressing one, three or eight primary HIV-1 gp120 antigens delivered by a gene gun followed by recombinant gp120 protein boosting. Neutralizing antibody responses were examined by two independently executed neutralization assays: the first one was a single round infection neutralization assay against a panel of 10 primary HIV-1 isolates of subtypes A, B, C and E and the second one used the PhenoSense assay against a panel of 12 pseudovirues expressing primary HIV-1 Env antigens from subtypes A, B, C, D and E as well as 2 pseudoviruses expressing the Env antigens from MN and NL4-3 viruses. Rabbit sera immunized with the DNA priming plus protein boosting approach, but not DNA vaccine alone or Env protein alone, were capable of neutralizing 7 of 10 viruses in the first assay and 12 of 14 viruses in the second assay. More importantly, sera immunized with the polyvalent Env antigens were able to neutralize a significantly higher percentage of viruses than the sera immunized with the monovalent antigens. Our results suggest that DNA priming followed by recombinant Env protein boosting can be used to deliver polyvalent Env-antigen-based HIV-1 vaccines to elicit neutralizing antibody responses against viruses with diverse genetic sequence variations.
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Affiliation(s)
- Shixia Wang
- Laboratory of Nucleic Acid Vaccines, Department of Medicine, University of Massachusetts Medical School, 364 Plantation Street, Lazare Research Building, Worcester, MA 01605, USA
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12
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Bradley J, Gill J, Bertelli F, Letafat S, Corbau R, Hayter P, Harrison P, Tee A, Keighley W, Perros M, Ciaramella G, Sewing A, Williams C. Development and automation of a 384-well cell fusion assay to identify inhibitors of CCR5/CD4-mediated HIV virus entry. ACTA ACUST UNITED AC 2005; 9:516-24. [PMID: 15452338 DOI: 10.1177/1087057104264577] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This article describes the automation of an in vitro cell-based fusion assay for the identification of novel inhibitors of receptor mediated HIV-1 entry. The assay utilises two stable cell lines: one expressing CD4, CCR5 and an LTR-promoter/beta-galactosidase reporter construct, and the other expressing gp160 and tat. Accumulation of beta-galactosidase can only occur following fusion of these two cell lines via the gp160 and receptor mediators, as this event facilitates the transfer of the tat transcription factor between the two cell types. Although similar cell fusion systems have been described previously, they have not met the requirements for HTS due to complexity, throughput and reagent cost. The assay described in this article provides significant advantage, as (a) no transfection/infection events are required prior to the assay, reducing the potential for variability, (b) cells are mixed in solution, enhancing fusion efficiency compared to adherent cells, (c) miniaturization to low volume enables screening in 384-well plates; and (d) online cell dispensing facilitates automated screening. This assay has been employed to screen approximately 650,000 compounds in a singleton format. The data demonstrate that the assay is robust, with a Z' consistently above 0.6, which compares favourably with less complex biochemical assays.
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Affiliation(s)
- Joe Bradley
- Laboratory Automation Group, Pfizer Global Research and Development, Kent, UK
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13
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Yi Y, Shaheen F, Collman RG. Preferential use of CXCR4 by R5X4 human immunodeficiency virus type 1 isolates for infection of primary lymphocytes. J Virol 2005; 79:1480-6. [PMID: 15650174 PMCID: PMC544090 DOI: 10.1128/jvi.79.3.1480-1486.2005] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Coreceptor specificity of human immunodeficiency virus type 1 (HIV-1) strains is generally defined in vitro in cell lines expressing CCR5 or CXCR4, but lymphocytes and macrophages are the principal targets in vivo. CCR5-using (R5) variants dominate early in infection, but strains that use CXCR4 emerge later in a substantial minority of subjects. Many or most CXCR4-using variants can use both CXCR4 and CCR5 (R5X4), but the pathways that are actually used to cause infection in primary cells and in vivo are unknown. We examined several R5X4 prototype and primary isolates and found that they all were largely or completely restricted to CXCR4-mediated entry in primary lymphocytes, even though lymphocytes are permissive for CCR5-mediated entry by R5 strains. In contrast, in primary macrophages R5X4 isolates used both CCR5 and CXCR4. The R5X4 strains were also more sensitive than R5 strains to CCR5 blocking, suggesting that interactions between the R5X4 strains and CCR5 are less efficient. These results indicate that coreceptor phenotyping in transformed cells does not necessarily predict utilization in primary cells, that variability exists among HIV-1 isolates in the ability to use CCR5 expressed on lymphocytes, and that many or most strains characterized as R5X4 are functionally X4 in primary lymphocytes. Less efficient interactions between R5X4 strains and CCR5 may be responsible for the inability to use CCR5 on lymphocytes, which express relatively low CCR5 levels. Since isolates that acquire CXCR4 utilization retain the capacity to use CCR5 on macrophages despite their inability to use it on lymphocytes, these results also raise the possibility that a CCR5-mediated macrophage reservoir is required for sustained infection in vivo.
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Affiliation(s)
- Yanjie Yi
- Department of Medicine, University of Pennsylvania School of Medicine, 36th & Hamilton Walk, 522 Johnson Pavilion, Philadelphia, PA 19104-6060, USA
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14
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Alam SM, Paleos CA, Liao HX, Scearce R, Robinson J, Haynes BF. An inducible HIV type 1 gp41 HR-2 peptide-binding site on HIV type 1 envelope gp120. AIDS Res Hum Retroviruses 2004; 20:836-45. [PMID: 15320988 DOI: 10.1089/0889222041725181] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Synthetic peptides of sequences within the HIV-1 gp41 heptad repeat-regions (HR-1 and HR-2) can effectively inhibit cell fusion and viral entry. DP178 (T-20), an HR-2 peptide, acts by inhibiting the association between HR-1 and HR-2, thereby interfering with HIV-1 fusion and viral entry. HR-2 peptide binding is predicted to be an important indicator of the presence of Env gp41 fusion intermediate conformation. A stabilized HR-2/Env conjugate might be an HIV-1 vaccine candidate and have the potential for inducing antibodies against transiently exposed epitopes on HIV-1 Env. To explore the possibility of design of HR-2 stabilized-HIV-1 immunogens, we studied the ability of HIV-1 Env to bind to HR-2 peptides. Using surface plasmon resonance (SPR)-binding assays and precipitation of soluble Env gp120 proteins with HR-2 peptide DP178, we have found that there is an HR-2 peptide-binding site on soluble HIV-1 recombinant gp120. Binding of DP178 was induced by sCD4 and by the anti-gp120 human mAb A32. The induction of DP178 binding was inhibited > 80% by the HIV-1 coreceptor-binding site mAb 17b. Binding of DP178 to gp120 was also inhibited by gp120 C4 peptides with sequences that are centrally located within the HIV-1 coreceptor-binding site. Thus, in addition to interactions with the gp41 HR-1 region, the fusion inhibitor peptide DP178 binds to triggered soluble HIV-1 recombinant gp120 following its interaction with sCD4 or CD4 mimic mAb A32. This may prove to be an important consideration when designing an HIV vaccine that utilizes constrained HIV Env proteins.
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Affiliation(s)
- S Munir Alam
- Department of Medicine, Duke Center for AIDS Research, Human Vaccine Institute, Duke University School of Medicine, Durham, North Carolina 27707, USA
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15
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Liu S, Shi X, Liu C, Sun Z. Characterize dynamic conformational space of human CCR5 extracellular domain by molecular modeling and molecular dynamics simulation. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/j.theochem.2003.12.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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16
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Jeffs SA, Goriup S, Kebble B, Crane D, Bolgiano B, Sattentau Q, Jones S, Holmes H. Expression and characterisation of recombinant oligomeric envelope glycoproteins derived from primary isolates of HIV-1. Vaccine 2004; 22:1032-46. [PMID: 15161081 DOI: 10.1016/j.vaccine.2003.08.042] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2003] [Accepted: 08/18/2003] [Indexed: 11/26/2022]
Abstract
The production, purification and characterisation of recombinant gp140 oligomeric envelope glycoproteins derived from six primary isolates of HIV-1 (covering clades A, B, C, D, F and O) are described. Using a Chinese hamster ovary cell expression system, expression levels of between 0.1 and 1 mg/l cell-conditioned culture media were obtained, and purified to >95% by affinity chromatography. A, B, D, F and O clade gp 140s were found to be multimeric, bind to a panel of defined env-specific monoclonal antibodies and interact with CD4 and CXCR4, demonstrating correct folding. Their immunogenicity was confirmed by the generation of high-titre anti-gp140 antibodies in rabbits. The C clade gp140 was incorrectly folded and poorly antigenic. Despite the presence of an unmodified gp120/41 cleavage site, only the B clade gp140 showed significant processing to gp120 and gp41. Each gp140 has a specific pattern of oligomerisation, and varies in its resistance to reducing agents and salt concentration. The binding of gp140 to soluble and cell-surface CD4 and CXCR4 is related to the degree of oligomerisation. The C1 and C5 regions, CD4 binding domain and the epitope defined by the 2G12 monoclonal antibody were well exposed, but the C-terminal region of the extracellular domain of gp41 appears to be occluded by oligomerisation. These reagents have potential as immunogens for use in vaccine development.
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Affiliation(s)
- S A Jeffs
- Division of Retrovirology, NIBSC, Blanche Lane, South Mimms, Potters Bar, Herts EN6 3QG, UK.
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17
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Buge SL, Ma HL, Amara RR, Wyatt LS, Earl PL, Villinger F, Montefiori DC, Staprans SI, Xu Y, Carter E, O'Neil SP, Herndon JG, Hill E, Moss B, Robinson HL, McNicholl JM. Gp120-alum boosting of a Gag-Pol-Env DNA/MVA AIDS vaccine: poorer control of a pathogenic viral challenge. AIDS Res Hum Retroviruses 2003; 19:891-900. [PMID: 14585221 DOI: 10.1089/088922203322493067] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Envelope protein immunogens may improve DNA or live-vectored HIV vaccines by complementing antiviral cellular responses with Env antibodies. We tested this concept by administering two immunizations of alum-adjuvanted HIV-1 89.6 gp120 to macaques being primed at weeks 0 and 8 with SHIV 89.6 Gag-Pol-Env DNA and boosted at week 24 with SHIV-89.6 Gag-Pol-Env recombinant modified vaccinia Ankara (MVA). Three hundred micrograms of gp120 was delivered with the second DNA prime and the MVA booster. Eight months after vaccination, all animals were challenged intrarectally with the related, yet serologically distinct, SHIV-89.6P. The gp120 immunizations raised binding, but not neutralizing antibody for the challenge virus, and allowed testing of whether gp120 vaccines that fail to raise neutralizing antibody can improve protection. Following the second gp120 immunization, the plus-gp120 group showed >10 times higher levels of binding antibody than the minus-gp120 group. These levels fell and were overall similar in both groups at the time of challenge. Following the second challenge, both groups had similar temporal patterns and heights of binding and neutralizing antibodies. However, the plus-gp120 group had less consistent control of viremia and higher levels of plasma viral RNA for the first year postchallenge. Assays for complement-dependent enhancing antibody revealed a trend toward higher levels of activity in the plus-gp120 group. This trend did not reach significance in our animal groups of 8. We conclude that gp120 inoculations that fail to raise neutralizing antibody do not improve the efficacy of Gag-Pol-Env DNA/MVA vaccines.
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Affiliation(s)
- Suzan L Buge
- Center for Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road NE, Atlanta, GA 30333, USA
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18
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Azevedo-Pereira JM, Santos-Costa Q, Mansinho K, Moniz-Pereira J. Identification and characterization of HIV-2 strains obtained from asymptomatic patients that do not use CCR5 or CXCR4 coreceptors. Virology 2003; 313:136-46. [PMID: 12951028 DOI: 10.1016/s0042-6822(03)00343-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
In vivo, human immunodeficiency virus type 2 (HIV-2) infection reveals several unique characteristics when compared to HIV-1 infection, the most remarkable of which is the extraordinarily long asymptomatic period. Here we describe two HIV-2 primary isolates, obtained from asymptomatic individuals, which do not infect any coreceptor-expressing cell lines tested. In those cells, we show that the absence of replication is directly related to cell entry events. Furthermore, productive infection observed in peripheral blood mononuclear cells (PBMC) was not inhibited by natural ligands and monoclonal antibodies directed to CCR5 and CXCR4. Finally, viral entry efficiency and viral progeny production of these viruses are markedly impaired in PBMC, indicating a reduced replicative fitness of both viruses. In conclusion, our data suggest that in some HIV-2 asymptomatic individuals, the circulating viruses are unable to use the major coreceptors to infect PBMC. This fact should have important implications in HIV-2 pathogenesis and transmission.
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Affiliation(s)
- J M Azevedo-Pereira
- Unidade dos Retrovírus e Infecções Associadas, Centro de Patogénese Molecular, Faculdade de Farmácia, Universidade de Lisboa, 1649-019 Lisboa, Portugal.
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19
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Suphaphiphat P, Thitithanyanont A, Paca-Uccaralertkun S, Essex M, Lee TH. Effect of amino acid substitution of the V3 and bridging sheet residues in human immunodeficiency virus type 1 subtype C gp120 on CCR5 utilization. J Virol 2003; 77:3832-7. [PMID: 12610158 PMCID: PMC149532 DOI: 10.1128/jvi.77.6.3832-3837.2003] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The V3 loop and the bridging sheet domain of human immunodeficiency virus type 1 (HIV-1) subtype B envelope glycoprotein gp120 have been implicated in CCR5 coreceptor utilization. In this study, mutant envelope glycoproteins of a subtype C isolate containing substitutions in the V3 or C4 region were generated to determine which are required for efficient CCR5-dependent cell fusion and viral entry. We found that the V3 crown and C4 residues are relatively dispensable for cell-cell fusion, although some residues may be involved in the regulation of early postentry steps in viral replication. In contrast, seven highly conserved residues located in the V3 stem are critical for CCR5 utilization, which can explain the apparent paradox that the functional convergence in CCR5 usage by genetically divergent HIV-1 strains involves a variable region. The finding that C4 residues do not have a critical role may appear to contradict the current model that bridging sheet residues are involved in the gp120-CCR5 interaction. However, a plausible interpretation is that these C4 residues may have a distinct role in the binding and fusion steps of the gp120-CCR5 interaction.
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Affiliation(s)
- Pirada Suphaphiphat
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts 02115, USA
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20
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Lin G, Baribaud F, Romano J, Doms RW, Hoxie JA. Identification of gp120 binding sites on CXCR4 by using CD4-independent human immunodeficiency virus type 2 Env proteins. J Virol 2003; 77:931-42. [PMID: 12502809 PMCID: PMC140809 DOI: 10.1128/jvi.77.2.931-942.2003] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human immunodeficiency virus (HIV) and simian (SIV) immunodeficiency virus entry is mediated by binding of the viral envelope glycoprotein (Env) to CD4 and chemokine receptors, CCR5 and/or CXCR4. CD4 induces extensive conformational changes that expose and/or induce formation of a chemokine receptor binding site on gp120. CD4-independent Env's of HIV type 1 (HIV-1), HIV-2, and SIV have been identified that exhibit exposed chemokine receptor binding sites and can bind directly to CCR5 or CXCR4 in the absence of CD4. While many studies have examined determinants for gp120-CCR5 binding, analysis of gp120-CXCR4 binding has been hindered by the apparently lower affinity of this interaction for X4-tropic HIV-1 isolates. We show here that gp120 proteins from two CD4-independent HIV-2 Env's, VCP and ROD/B, bind directly to CXCR4 with an apparently high affinity. By use of CXCR4 N-terminal deletion constructs, CXCR4-CXCR2 chimeras, and human-rat CXCR4 chimeras, binding determinants were shown to reside in the amino (N) terminus, extracellular loop 2 (ECL2), and ECL3. Alanine-scanning mutagenesis of charged residues, tyrosines, and phenylalanines in extracellular CXCR4 domains implicated multiple amino acids in the N terminus (E14/E15, D20, Y21, and D22), ECL2 (D187, R188, F189, Y190, and D193), and ECL3 (D262, E268, E277, and E282) in binding, although minor differences were noted between VCP and ROD/B. However, mutations in CXCR4 that markedly reduced binding did not necessarily hinder cell-cell fusion by VCP or ROD/B, especially in the presence of CD4. These gp120 proteins will be useful in dissecting determinants for CXCR4 binding and Env triggering and in evaluating pharmacologic inhibitors of the gp120-CXCR4 interaction.
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Affiliation(s)
- George Lin
- Hematology-Oncology Division, Department of Medicine, University of Pennsylvania, Philadelphia 19104, USA
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21
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Chelli M, Alizon M. Rescue of HIV-1 receptor function through cooperation between different forms of the CCR5 chemokine receptor. J Biol Chem 2002; 277:39388-96. [PMID: 12154092 DOI: 10.1074/jbc.m205394200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Interaction of the human immunodeficiency virus (HIV-1) envelope glycoproteins with the CCR5 chemokine receptor, a G-protein-coupled receptor, triggers a membrane fusion process and virus entry. Cooperation for HIV-1 receptor activity was observed when two forms of CCR5 were coexpressed, either the wild-type (WT) receptor and a defective mutant with deletion of the amino-terminal (NT) extracellular domain or the latter deltaNT mutant and a human-mouse CCR5 chimera bearing the NT domain from human CCR5. Cooperation was most efficient when the two forms of CCR5 were in a 1:1 ratio. It was not observed between the CCR5 deltaNT mutant and a chimeric receptor (5444) in which the NT domain of CCR5 was in the context of another G-protein-coupled receptor, the HIV-1 receptor CXCR4. These results suggested that physical association between two forms of CCR5 was required for their cooperation. Coimmunoprecipitation experiments in transfected cell lysates indeed showed that the deltaNT CCR5 mutant formed oligomeric complexes with the WT CCR5 or the HMMM chimera but not with the CXCR4-derived chimera 5444. These observations suggest that the formation of CCR5 oligomers is a constitutive process independent from activation by chemokine ligands. The interaction of HIV-1 with independent subunits of CCR5 oligomers could favor the local recruitment of fusiogenic proteins and the formation of a fusion pore.
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Affiliation(s)
- Maurice Chelli
- Department of Cell Biology, Institut Cochin, INSERM U-567, CNRS Unité Mixté de Recherche 8404, Université Paris V-René Descartes, 75014 Paris, France
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22
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Affiliation(s)
- A Brelot
- INSERM, Département de Biologie Cellulaire, Institut Cochin de Génétique Moléculaire, 22 rue Méchain, 75014 Paris, France
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23
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Margolin DH, Saunders EFH, Bronfin B, de Rosa N, Axthelm MK, Alvarez X, Letvin NL. High frequency of virus-specific B lymphocytes in germinal centers of simian-human immunodeficiency virus-infected rhesus monkeys. J Virol 2002; 76:3965-73. [PMID: 11907236 PMCID: PMC136115 DOI: 10.1128/jvi.76.8.3965-3973.2002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The etiology of the lymphadenopathy and follicular hyperplasia associated with human immunodeficiency virus type 1 (HIV-1) infection has remained unclear. To determine whether the B-lymphocyte expansions characteristic of this syndrome represent polyclonal and virus-specific processes, the antigen specificity of B cells in lymphoid tissues of monkeys infected with simian-human immunodeficiency virus (SHIV) chimeras was assessed using an inverse immunohistochemical assay with biotinylated HIV-1 envelope gp120 (Env) as an antigen probe. Env-binding B cells were found aggregated in lymph node and splenic germinal centers (GCs). Most Env-binding GCs also contained an unstained population of B cells, suggesting the GCs were formed by a polyclonal (oligoclonal) process. By day 42 following infection, Env-binding B cells were present in 19% of all lymph node GCs. Env-binding cells were present in 25% of GCs even during chronic infection. This extraordinarily high frequency of Env-specific B lymphocytes suggests that the expansion of virus-specific B cells may largely account for the follicular hyperplasia in AIDS virus-infected individuals.
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Affiliation(s)
- David H Margolin
- Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA.
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24
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Power C, Johnson RT. Neuroimmune and neurovirological aspects of human immunodeficiency virus infection. Adv Virus Res 2002; 56:389-433. [PMID: 11450307 DOI: 10.1016/s0065-3527(01)56034-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Like most lentiviruses, HIV-1 causes both immune suppression and neurological disease. Neurological disease may occur at any stage of HIV infection but is most apparent with severe immune suppression. Cognitive impairment, reflected strikingly by HIV-associated dementia, has attracted intense interest since the outset of the HIV epidemic, and understanding of its pathogenesis has been spurred on by the emergence of several hypotheses outlining potential pathogenic mechanisms. The release of inflammatory molecules by HIV-infected microglia and macrophages and the concurrent neuronal damage play central roles in the conceptualization of HIV neuropathogenesis. Many inflammatory molecules appear to contribute to the pathogenic cascade and their individual roles remain undefined. At the same time, the abundance of virus in the brain and the type or strain of virus found in the brain may also be important codeterminants of neurological disease, as shown for other neurotropic viruses. Coreceptor use by HIV found in the brain appears to closely mirror what has been reported in systemic macrophages. The impact of HAART on viral genotype and phenotype found in the brain, and its relationship to clinical disease, remain uncertain. Several interesting animal models have been developed, using other lentiviruses, transgenic animals, and HIV-infected SCID mice, that may prove useful in future pathogenesis and therapeutic studies. Despite the progress in the understanding of HIV neuropathogenesis, many questions remain unanswered.
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Affiliation(s)
- C Power
- Departments of Clinical Neuroscience, Microbiology, and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
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25
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Bannert N, Craig S, Farzan M, Sogah D, Santo NV, Choe H, Sodroski J. Sialylated O-glycans and sulfated tyrosines in the NH2-terminal domain of CC chemokine receptor 5 contribute to high affinity binding of chemokines. J Exp Med 2001; 194:1661-73. [PMID: 11733580 PMCID: PMC2193526 DOI: 10.1084/jem.194.11.1661] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
The chemokine receptor CCR5 plays an important role in leukocyte chemotaxis and activation, and also acts as a coreceptor for human and simian immunodeficiency viruses (HIV-1, HIV-2, and SIV). We provide evidence that CCR5 is O-glycosylated on serine 6 in the NH2 terminus. The O-linked glycans, particularly sialic acid moieties, significantly contribute to binding of the chemokine ligands. By contrast, removal of O-linked oligosaccharide exerted little effect on HIV-1 infection. Sulfation of specific tyrosine residues in the CCR5 NH2 terminus was important for efficient beta-chemokine binding. Thus, as has been observed for the binding of selectins and their ligands, O-linked carbohydrates and tyrosine sulfates play major roles in promoting the interaction of chemokines with CCR5. The resulting flexible arrays of negative charges on the CCR5 surface may allow specific, high-affinity interactions with diverse chemokine ligands. Although this is the first example of O-linked oligosaccharides and tyrosine sulfates playing a role in chemokine binding, the high density of serines, threonines and tyrosines in the N-termini of many CC chemokine receptors suggests that these posttranslational modifications may commonly contribute to chemokine binding.
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Affiliation(s)
- N Bannert
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Boston, MA 02115, USA
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26
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Pontow S, Ratner L. Evidence for common structural determinants of human immunodeficiency virus type 1 coreceptor activity provided through functional analysis of CCR5/CXCR4 chimeric coreceptors. J Virol 2001; 75:11503-14. [PMID: 11689632 PMCID: PMC114737 DOI: 10.1128/jvi.75.23.11503-11514.2001] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) infection in vivo is dependent upon the interaction of the viral envelope glycoprotein gp120 with CC chemokine receptor 5 (CCR5) or CXC chemokine receptor 4 (CXCR4). To study the determinants of the gp120-coreceptor association, we generated a set of chimeric HIV-1 coreceptors which express all possible combinations of the four extracellular domains of CCR5 and CXCR4. Stable U87 astroglioma cell lines expressing CD4 and individual chimeric coreceptor proteins were tested against a variety of R5, X4, and R5X4 envelope glycoproteins and virus strains for their ability to support HIV-1-mediated cell fusion and infection, respectively. Each of the cell lines promoted fusion with cells expressing an HIV envelope glycoprotein, except for U87.CD4.5455, which presents the first extracellular loop (ECL1) and flanking sequences of CXCR4 in the context of CCR5. However, all of the chimeric coreceptors allowed productive infection by one or more of the viral strains tested. Viral phenotype was a predictive factor for the observed activity of the chimeric molecules; X4 and R5X4 HIV strains utilized a majority of the chimeras, while R5 strains were limited in their ability to infect cells expressing these chimeric molecules. The expression of CCR5 ECL2 within the CXCR4 backbone supported infection by an R5 primary isolate, but no chimeras bearing the N terminus of CCR5 exhibited activity with R5 strains. Remarkably, the introduction of any CXCR4 domain into the CCR5 backbone was sufficient to allow utilization by multiple X4 strains. However, critical determinants within ECL2 and/or ECL3 of CXCR4 were apparent for all X4 viruses upon replacement of these domains in CXCR4 with CCR5 sequences. Unexpectedly, chimeric coreceptor-facilitated entry was blocked in all cases by the presence of the CXCR4-specific inhibitor AMD3100. Our data provide proof that CCR5 contains elements that support usage by X4 viral strains and demonstrate that the gp120 interaction sites of CCR5 and CXCR4 are structurally related.
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Affiliation(s)
- S Pontow
- Molecular Oncology Division, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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27
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Gp120-induced Bob/GPR15 activation: a possible cause of human immunodeficiency virus enteropathy. THE AMERICAN JOURNAL OF PATHOLOGY 2001; 159:1933-9. [PMID: 11696454 PMCID: PMC1867054 DOI: 10.1016/s0002-9440(10)63040-4] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Human immunodeficiency virus (HIV)-infected patients often develop malabsorption and increased intestinal permeability with diarrhea, called HIV enteropathy, even without enteric opportunistic infections. HIV gp120-induced calcium signaling, microtubule loss, and physiological changes resembling HIV enteropathy were previously found in the HT-29 intestinal cell line. How gp120 caused these changes was unclear. We show that the HIV co-receptor Bob/GPR15, unlike CCR5 and CXCR4, is abundant at the basal surface of small intestinal epithelium. The gp120-induced effects on HT-29 cells were inhibited by anti-Bob neutralizing antibodies, the selective G protein inhibitor pertussis toxin, and the phospholipase inhibitor U73122, but not neutralizing antibodies to CXCR4. Gp120 strains that induced signaling in HT-29 cells also induced calcium fluxes in Bob-transfected Ghost (3) cells, whereas gp120 strains not activating HT-29 cells also did not activate Bob-transfected cells. Bob is the first HIV co-receptor shown to be abundantly expressed on the basolateral surface of intestinal epithelium. Although Bob is an inefficient infection-inducing co-receptor, it mediates viral strain-specific gp120-induced calcium signaling at low, physiologically reasonable gp120 concentrations, up to 10,000-fold lower gp120 concentrations than the principal co-receptors. Gp120-induced Bob activation is a plausible cause of HIV enteropathy.
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28
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Singer II, Scott S, Kawka DW, Chin J, Daugherty BL, DeMartino JA, DiSalvo J, Gould SL, Lineberger JE, Malkowitz L, Miller MD, Mitnaul L, Siciliano SJ, Staruch MJ, Williams HR, Zweerink HJ, Springer MS. CCR5, CXCR4, and CD4 are clustered and closely apposed on microvilli of human macrophages and T cells. J Virol 2001; 75:3779-90. [PMID: 11264367 PMCID: PMC114869 DOI: 10.1128/jvi.75.8.3779-3790.2001] [Citation(s) in RCA: 131] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The chemokine receptors CCR5 and CXCR4 act synergistically with CD4 in an ordered multistep mechanism to allow the binding and entry of human immunodeficiency virus type 1 (HIV-1). The efficiency of such a coordinated mechanism depends on the spatial distribution of the participating molecules on the cell surface. Immunoelectron microscopy was performed to address the subcellular localization of the chemokine receptors and CD4 at high resolution. Cells were fixed, cryoprocessed, and frozen; 80-nm cryosections were double labeled with combinations of CCR5, CXCR4, and CD4 antibodies and then stained with immunogold. Surprisingly, CCR5, CXCR4, and CD4 were found predominantly on microvilli and appeared to form homogeneous microclusters in all cell types examined, including macrophages and T cells. Further, while mixed microclusters were not observed, homogeneous microclusters of CD4 and the chemokine receptors were frequently separated by distances less than the diameter of an HIV-1 virion. Such distributions are likely to facilitate cooperative interactions with HIV-1 during virus adsorption to and penetration of human leukocytes and have significant implications for development of therapeutically useful inhibitors of the entry process. Although the mechanism underlying clustering is not understood, clusters were observed in small trans-Golgi vesicles, implying that they were organized shortly after synthesis and well before insertion into the cellular membrane. Chemokine receptors normally act as sensors, detecting concentration gradients of their ligands and thus providing directional information for cellular migration during both normal homeostasis and inflammatory responses. Localization of these sensors on the microvilli should enable more precise monitoring of their environment, improving efficiency of the chemotactic process. Moreover, since selectins, some integrins, and actin are also located on or in the microvillus, this organelle has many of the major elements required for chemotaxis.
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MESH Headings
- Animals
- CD4 Antigens/genetics
- CD4 Antigens/metabolism
- Cell Line
- Cells, Cultured
- Fluorescent Antibody Technique
- Golgi Apparatus/metabolism
- HIV Antibodies/immunology
- HIV Envelope Protein gp120/metabolism
- HIV-1/metabolism
- HIV-1/physiology
- Humans
- Macrophages/cytology
- Macrophages/metabolism
- Macrophages/ultrastructure
- Macrophages/virology
- Membrane Microdomains/metabolism
- Membrane Microdomains/ultrastructure
- Microscopy, Electron, Scanning
- Microscopy, Immunoelectron
- Microvilli/metabolism
- Microvilli/ultrastructure
- Rabbits
- Receptors, CCR2
- Receptors, CCR5/genetics
- Receptors, CCR5/metabolism
- Receptors, CXCR4/genetics
- Receptors, CXCR4/metabolism
- Receptors, Chemokine/metabolism
- Secretory Vesicles/metabolism
- T-Lymphocytes/cytology
- T-Lymphocytes/metabolism
- T-Lymphocytes/ultrastructure
- T-Lymphocytes/virology
- Thermodynamics
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Affiliation(s)
- I I Singer
- Department of Immunology and Rheumotology, Merck Research Laboratories, Rahway, New Jersey 07065, USA.
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29
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MESH Headings
- CD4 Antigens/physiology
- CD4-Positive T-Lymphocytes/virology
- Cell Adhesion Molecules
- Cell Membrane/physiology
- Dendritic Cells/virology
- Down-Regulation
- Gene Expression Regulation, Viral
- Gene Products, env/physiology
- Gene Products, nef/chemistry
- Gene Products, nef/physiology
- HIV Infections/pathology
- HIV-1/genetics
- HIV-1/physiology
- HLA Antigens/genetics
- Humans
- Lectins/physiology
- Lectins, C-Type
- Membrane Fusion
- Models, Biological
- Models, Molecular
- Protein Conformation
- Receptors, CCR5/physiology
- Receptors, CXCR4/physiology
- Receptors, Cell Surface/physiology
- Receptors, HIV/physiology
- Virus Assembly
- Virus Replication
- Virus Shedding
- nef Gene Products, Human Immunodeficiency Virus
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Affiliation(s)
- R W Doms
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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30
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Doms RW. Beyond receptor expression: the influence of receptor conformation, density, and affinity in HIV-1 infection. Virology 2000; 276:229-37. [PMID: 11040114 DOI: 10.1006/viro.2000.0612] [Citation(s) in RCA: 154] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- R W Doms
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, 19104, USA.
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31
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Hoffman TL, Canziani G, Jia L, Rucker J, Doms RW. A biosensor assay for studying ligand-membrane receptor interactions: binding of antibodies and HIV-1 Env to chemokine receptors. Proc Natl Acad Sci U S A 2000; 97:11215-20. [PMID: 11005830 PMCID: PMC17180 DOI: 10.1073/pnas.190274097] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The HIV envelope (Env) protein mediates entry into cells by binding CD4 and an appropriate coreceptor, which triggers structural changes in Env that lead to fusion between the viral and cellular membranes. The major HIV-1 coreceptors are the seven transmembrane domain chemokine receptors CCR5 and CXCR4. The type of coreceptor used by a virus strain is an important determinant of viral tropism and pathogenesis, and virus-receptor interactions can be therapeutic targets. However, Envs from many virus strains interact with CXCR4 and CCR5 with low affinity such that direct study of this important interaction is difficult if not impossible using standard cell-surface binding techniques. We have developed an approach that makes it possible to study ligand binding to membrane proteins, including Env-coreceptor interactions, using an optical biosensor. CCR5, CXCR4, and other membrane proteins were incorporated into retrovirus particles, which were purified and attached to the biosensor surface. Binding of conformationally sensitive antibodies as well as Env to these receptors was readily detected. The equilibrium dissociation constant for the interaction between an Env derived from the prototype HIV-1 strain IIIB for CXCR4 was approximately 500 nM, explaining the difficulty in measuring this interaction using standard equilibrium binding techniques. Retroviral pseudotypes represent easily produced, stable, homogenous structures that can be used to present a wide array of single and multiple membrane-spanning proteins in a native lipid environment for biosensor studies, thus avoiding the need for detergent solubilization, purification, and reconstitution. The approach should have general applicability and can be used to correlate Env-receptor binding constants to viral tropism and pathogenesis.
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Affiliation(s)
- T L Hoffman
- Departments of Pathology and Lab Medicine, Medicine, and Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA
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32
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Hu Q, Trent JO, Tomaras GD, Wang Z, Murray JL, Conolly SM, Navenot JM, Barry AP, Greenberg ML, Peiper SC. Identification of ENV determinants in V3 that influence the molecular anatomy of CCR5 utilization. J Mol Biol 2000; 302:359-75. [PMID: 10970739 DOI: 10.1006/jmbi.2000.4076] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The V3 loop of the ENV glycoprotein exerts a dominant influence on the interaction of gp120 with coreceptors. Primary env genes cloned from sequential isolates from two seroconverters revealed Pro-->Ala conversion in the conserved GPG motif of the V3 crown in seven of 17 R5 ENV. ENV containing the GPG motif in the V3 crown had fusogenic activity with chimeric receptors containing either the N terminus or loops of CCR5, whereas those with the GAG variant utilized only the former. Site-directed mutagenesis of multiple primary and prototypic R5 env genes demonstrated that the GPG motif was necessary for dual utilization of the N terminus and body of CCR5 in both gain and loss-of-function experiments. All ENV containing the GPG V3 crown showed CCR5 binding in the presence of soluble CD4, whereas it was not detected with the GAG variants. Molecular dynamic simulations of a V3 peptide predicts that the Pro-->Ala substitution results in a conformational change with loss of the crown structure. These studies demonstrate that sequences in the third hypervariable region determine the specificity of coreceptor utilization for fusion, and that a conserved motif in the crown directly influences the molecular anatomy of the interaction between gp120 and CCR5.
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Affiliation(s)
- Q Hu
- Henry Vogt Cancer Research Institute, James Graham Brown Cancer Center, Louisville, KY, 40202, USA.
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33
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Abstract
CCR5 is the major coreceptor for macrophage-tropic strains of the human immunodeficiency virus type I (HIV-1). Homozygotes for a 32-base pair (bp) deletion in the coding sequence of the receptor (CCR5Δ32) were found to be highly resistant to viral infection, and CCR5 became, therefore, one of the paradigms illustrating the influence of genetic variability onto individual susceptibility to infectious and other diseases. We investigated the functional consequences of 16 other natural CCR5 mutations described in various human populations. We found that 10 of these variants are efficiently expressed at the cell surface, bind [125I]-MIP-1β with affinities similar to wtCCR5, respond functionally to chemokines, and act as HIV-1 coreceptors. In addition to Δ32, six mutations were characterized by major alterations in their functional response to chemokines, as a consequence of intracellular trapping and poor expression at the cell surface (C101X, FS299), general or specific alteration of ligand binding affinities (C20S, C178R, A29S), or relative inability to mediate receptor activation (L55Q). A29S displayed an unusual pharmacological profile, binding and responding to MCP-2 similarly to wtCCR5, but exhibiting severely impaired binding and functional responses to MIP-1α, MIP-1β, and RANTES. In addition to Δ32, only C101X was totally unable to mediate entry of HIV-1. The fact that nonfunctional CCR5 alleles are relatively frequent in various human populations reinforces the hypothesis of a selective pressure favoring these alleles.
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34
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Abstract
Abstract
CCR5 is the major coreceptor for macrophage-tropic strains of the human immunodeficiency virus type I (HIV-1). Homozygotes for a 32-base pair (bp) deletion in the coding sequence of the receptor (CCR5Δ32) were found to be highly resistant to viral infection, and CCR5 became, therefore, one of the paradigms illustrating the influence of genetic variability onto individual susceptibility to infectious and other diseases. We investigated the functional consequences of 16 other natural CCR5 mutations described in various human populations. We found that 10 of these variants are efficiently expressed at the cell surface, bind [125I]-MIP-1β with affinities similar to wtCCR5, respond functionally to chemokines, and act as HIV-1 coreceptors. In addition to Δ32, six mutations were characterized by major alterations in their functional response to chemokines, as a consequence of intracellular trapping and poor expression at the cell surface (C101X, FS299), general or specific alteration of ligand binding affinities (C20S, C178R, A29S), or relative inability to mediate receptor activation (L55Q). A29S displayed an unusual pharmacological profile, binding and responding to MCP-2 similarly to wtCCR5, but exhibiting severely impaired binding and functional responses to MIP-1α, MIP-1β, and RANTES. In addition to Δ32, only C101X was totally unable to mediate entry of HIV-1. The fact that nonfunctional CCR5 alleles are relatively frequent in various human populations reinforces the hypothesis of a selective pressure favoring these alleles.
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35
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Vila-Coro AJ, Mellado M, Martín de Ana A, Lucas P, del Real G, Martínez-A C, Rodríguez-Frade JM. HIV-1 infection through the CCR5 receptor is blocked by receptor dimerization. Proc Natl Acad Sci U S A 2000; 97:3388-93. [PMID: 10725362 PMCID: PMC16249 DOI: 10.1073/pnas.97.7.3388] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The identification of the chemokine receptors as receptors for HIV-1 has boosted interest in these molecules, raising expectations for the development of new strategies to prevent HIV-1 infection. The discovery that chemokines block HIV-1 replication has focused attention on identifying their mechanism of action. Previous studies concluded that this inhibitory effect may be mediated by steric hindrance or by receptor down-regulation. We have identified a CCR5 receptor-specific mAb that neither competes with the chemokine for binding nor triggers signaling, as measured by Ca(2+) influx or chemotaxis. The antibody neither triggers receptor down-regulation nor interferes with the R5 JRFL viral strain gp120 binding to CCR5, but blocks HIV-1 replication in both in vitro assays using peripheral blood mononuclear cells as HIV-1 targets, as well as in vivo using human peripheral blood mononuclear cell-reconstituted SCID (severe combined immunodeficient) mice. Our evidence shows that the anti-CCR5 mAb efficiently prevents HIV-1 infection by inducing receptor dimerization. Chemokine receptor dimerization also is induced by chemokines and is required for their anti-HIV-1 activity. In addition to providing a molecular mechanism through which chemokines block HIV-1 infection, these results illustrate the prospects for developing new tools that possess HIV-1 suppressor activity, but lack the undesired inflammatory side effects of the chemokines.
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Affiliation(s)
- A J Vila-Coro
- Department of Immunology and Oncology, Centro Nacional de Biotecnologia, Universidad Autónoma de Madrid, Campus de Cantoblanco, E-28049, Madrid, Spain
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36
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HIV-1 infection through the CCR5 receptor is blocked by receptor dimerization. Proc Natl Acad Sci U S A 2000. [PMID: 10725362 PMCID: PMC16249 DOI: 10.1073/pnas.050457797] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The identification of the chemokine receptors as receptors for HIV-1 has boosted interest in these molecules, raising expectations for the development of new strategies to prevent HIV-1 infection. The discovery that chemokines block HIV-1 replication has focused attention on identifying their mechanism of action. Previous studies concluded that this inhibitory effect may be mediated by steric hindrance or by receptor down-regulation. We have identified a CCR5 receptor-specific mAb that neither competes with the chemokine for binding nor triggers signaling, as measured by Ca(2+) influx or chemotaxis. The antibody neither triggers receptor down-regulation nor interferes with the R5 JRFL viral strain gp120 binding to CCR5, but blocks HIV-1 replication in both in vitro assays using peripheral blood mononuclear cells as HIV-1 targets, as well as in vivo using human peripheral blood mononuclear cell-reconstituted SCID (severe combined immunodeficient) mice. Our evidence shows that the anti-CCR5 mAb efficiently prevents HIV-1 infection by inducing receptor dimerization. Chemokine receptor dimerization also is induced by chemokines and is required for their anti-HIV-1 activity. In addition to providing a molecular mechanism through which chemokines block HIV-1 infection, these results illustrate the prospects for developing new tools that possess HIV-1 suppressor activity, but lack the undesired inflammatory side effects of the chemokines.
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37
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Abstract
HIV vaccine development has been hampered by the inability of conventional immunogens to elicit antibodies capable of neutralizing primary isolates of the virus. Recent studies using 'fusion-competent' immunogens that capture transitional intermediate structures of the functioning envelope protein suggest that this goal may now be achievable.
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Affiliation(s)
- J H Nunberg
- Montana Biotechnology Center, The University of Montana, Missoula, MT 59812, USA
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38
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Salzwedel K, Smith ED, Dey B, Berger EA. Sequential CD4-coreceptor interactions in human immunodeficiency virus type 1 Env function: soluble CD4 activates Env for coreceptor-dependent fusion and reveals blocking activities of antibodies against cryptic conserved epitopes on gp120. J Virol 2000; 74:326-33. [PMID: 10590121 PMCID: PMC111543 DOI: 10.1128/jvi.74.1.326-333.2000] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/1999] [Accepted: 09/27/1999] [Indexed: 11/20/2022] Open
Abstract
We devised an experimental system to examine sequential events by which the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (Env) interacts with CD4 and coreceptor to induce membrane fusion. Recombinant soluble CD4 (sCD4) activated fusion between effector cells expressing Env and target cells expressing coreceptor (CCR5 or CXCR4) but lacking CD4. sCD4-activated fusion was dose dependent, occurred comparably with two- and four-domain proteins, and demonstrated Env-coreceptor specificities parallel to those reported in conventional fusion and infectivity systems. Fusion activation occurred upon sCD4 preincubation and washing of the Env-expressing effector cells but not the coreceptor-bearing target cells, thereby demonstrating that sCD4 exerts its effects by acting on Env. These findings provide direct functional evidence for a sequential two-step model of Env-receptor interactions, whereby gp120 binds first to CD4 and becomes activated for subsequent functional interaction with coreceptor, leading to membrane fusion. We used the sCD4-activated system to explore neutralization by the anti-gp120 human monoclonal antibodies 17b and 48d. These antibodies reportedly bind conserved CD4-induced epitopes involved in coreceptor interactions but neutralize HIV-1 infection only weakly. We found that 17b and 48d had minimal effects in the standard cell fusion system using target cells expressing both CD4 and coreceptor but potently blocked sCD4-activated fusion with target cells expressing coreceptor alone. Both antibodies strongly inhibited sCD4-activated fusion by Envs from genetically diverse HIV-1 isolates. Thus, the sCD4-activated system reveals conserved Env-blocking epitopes that are masked in native Env and hence not readily detected by conventional systems.
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Affiliation(s)
- K Salzwedel
- Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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39
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Blanpain C, Doranz BJ, Vakili J, Rucker J, Govaerts C, Baik SS, Lorthioir O, Migeotte I, Libert F, Baleux F, Vassart G, Doms RW, Parmentier M. Multiple charged and aromatic residues in CCR5 amino-terminal domain are involved in high affinity binding of both chemokines and HIV-1 Env protein. J Biol Chem 1999; 274:34719-27. [PMID: 10574939 DOI: 10.1074/jbc.274.49.34719] [Citation(s) in RCA: 120] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CCR5 is a functional receptor for MIP-1alpha, MIP-1beta, RANTES (regulated on activation normal T cell expressed), MCP-2, and MCP-4 and constitutes the main coreceptor for macrophage tropic human and simian immunodeficiency viruses. By using CCR5-CCR2b chimeras, we have shown previously that the second extracellular loop of CCR5 is the major determinant for chemokine binding specificity, whereas the amino-terminal domain plays a major role for human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus coreceptor function. In the present work, by using a panel of truncation and alanine-scanning mutants, we investigated the role of specific residues in the CCR5 amino-terminal domain for chemokine binding, functional response to chemokines, HIV-1 gp120 binding, and coreceptor function. Truncation of the amino-terminal domain resulted in a progressive decrease of the binding affinity for chemokines, which correlated with a similar drop in functional responsiveness. Mutants lacking residues 2-13 exhibited fairly weak responses to high concentrations (500 nM) of RANTES or MIP-1beta. Truncated mutants also exhibited a reduction in the binding affinity for R5 Env proteins and coreceptor activity. Deletion of 4 or 12 residues resulted in a 50 or 80% decrease in coreceptor function, respectively. Alanine-scanning mutagenesis identified several charged and aromatic residues (Asp-2, Tyr-3, Tyr-10, Asp-11, and Glu-18) that played an important role in both chemokine and Env high affinity binding. The overlapping binding site of chemokines and gp120 on the CCR5 amino terminus, as well as the involvement of these residues in the epitopes of monoclonal antibodies, suggests that these regions are particularly exposed at the receptor surface.
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Affiliation(s)
- C Blanpain
- IRIBHN, Université Libre de Bruxelles, Campus Erasme, 808 Route de Lennik, B-1070 Bruxelles, Belgium
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40
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Doranz BJ, Baik SS, Doms RW. Use of a gp120 binding assay to dissect the requirements and kinetics of human immunodeficiency virus fusion events. J Virol 1999; 73:10346-58. [PMID: 10559353 PMCID: PMC113090 DOI: 10.1128/jvi.73.12.10346-10358.1999] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Binding of the extracellular subunit of human immunodeficiency type 1 (HIV-1) envelope (Env) glycoprotein (gp120) to CD4 triggers the induction or exposure of a highly conserved coreceptor binding site in gp120 that helps mediate membrane fusion. Characterizing the structural features involved in gp120-coreceptor binding and the conditions under which binding occurs is important for understanding the fusion process, the evolution of pathogenic strains in vivo, the identification of novel anti-HIV compounds, and the development of HIV vaccines that utilize triggered structures of Env. Here we use the kinetics of interaction between CCR5 and gp120 to understand temporal and structural changes that occur during viral fusion. Using saturation binding and homologous competition analysis, we estimated the K(d) of interaction between CCR5 and gp120 from the macrophage tropic HIV-1 strain JRFL to be 4 nM. Unlike Env-mediated fusion, gp120 binding to CCR5 did not require divalent cations or elevated temperatures. Binding was not significantly affected by the pH of binding, G-protein coupling of CCR5, or partial gp120 deglycosylation. Oligomeric, uncleaved JRFL gp140 failed to bind CCR5 despite its ability to bind CD4 and monoclonal antibody 17b, suggesting that the uncleaved ectodomain of gp41 interferes with full exposure of the chemokine receptor binding site. Exposure of the chemokine receptor binding site on gp120 could be induced rapidly by CD4, but exposure of this site was lost upon CD4 dissociation from gp120, indicating that the conformational changes in gp120 induced by CD4 binding are fully reversible. The functional gp120-soluble CD4 complex was remarkably stable over time and temperature ranges, offering the possibility that complexes in which the highly conserved coreceptor binding site in gp120 is exposed can be used for vaccine development.
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Affiliation(s)
- B J Doranz
- Department of Pathology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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