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Piédrola I, Martínez S, Gradillas A, Villaseñor A, Alonso-Herranz V, Sánchez-Vera I, Escudero E, Martín-Antoniano IA, Varona JF, Ruiz A, Castellano JM, Muñoz Ú, Sádaba MC. Deficiency in the production of antibodies to lipids correlates with increased lipid metabolism in severe COVID-19 patients. Front Immunol 2023; 14:1188786. [PMID: 37426663 PMCID: PMC10327431 DOI: 10.3389/fimmu.2023.1188786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 05/26/2023] [Indexed: 07/11/2023] Open
Abstract
Background Antibodies to lipids are part of the first line of defense against microorganisms and regulate the pro/anti-inflammatory balance. Viruses modulate cellular lipid metabolism to enhance their replication, and some of these metabolites are proinflammatory. We hypothesized that antibodies to lipids would play a main role of in the defense against SARS-CoV-2 and thus, they would also avoid the hyperinflammation, a main problem in severe condition patients. Methods Serum samples from COVID-19 patients with mild and severe course, and control group were included. IgG and IgM to different glycerophospholipids and sphingolipids were analyzed using a high-sensitive ELISA developed in our laboratory. A lipidomic approach for studying lipid metabolism was performed using ultra-high performance liquid chromatography coupled to electrospray ionization and quadrupole time-of-flight mass spectrometry (UHPLC-ESI-QTOF-MS). Results Mild and severe COVID-19 patients had higher levels of IgM to glycerophosphocholines than control group. Mild COVID-19 patients showed higher levels of IgM to glycerophosphoinositol, glycerophosphoserine and sulfatides than control group and mild cases. 82.5% of mild COVID-19 patients showed IgM to glycerophosphoinositol or glycerophosphocholines plus sulfatides or glycerophosphoserines. Only 35% of severe cases and 27.5% of control group were positive for IgM to these lipids. Lipidomic analysis identify a total of 196 lipids, including 172 glycerophospholipids and 24 sphingomyelins. Increased levels of lipid subclasses belonging to lysoglycerophospholipids, ether and/or vinyl-ether-linked glycerophospholipids, and sphingomyelins were observed in severe COVID-19 patients, when compared with those of mild cases and control group. Conclusion Antibodies to lipids are essential for defense against SARS-CoV-2. Patients with low levels of anti-lipid antibodies have an elevated inflammatory response mediated by lysoglycerophospholipids. These findings provide novel prognostic biomarkers and therapeutic targets.
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Affiliation(s)
- Ignacio Piédrola
- Instituto de Medicina Molecular Aplicada (IMMA), Facultad de Medicina, Universidad San Pablo-CEU, CEU Universities, Boadilla del Monte, Madrid, Spain
| | - Sara Martínez
- Centro de Metabolómica y Bioanálisis (CEMBIO), Facultad de Farmacia, Universidad San Pablo-CEU, CEU Universities, Boadilla del Monte, Madrid, Spain
| | - Ana Gradillas
- Centro de Metabolómica y Bioanálisis (CEMBIO), Facultad de Farmacia, Universidad San Pablo-CEU, CEU Universities, Boadilla del Monte, Madrid, Spain
| | - Alma Villaseñor
- Instituto de Medicina Molecular Aplicada (IMMA), Facultad de Medicina, Universidad San Pablo-CEU, CEU Universities, Boadilla del Monte, Madrid, Spain
- Centro de Metabolómica y Bioanálisis (CEMBIO), Facultad de Farmacia, Universidad San Pablo-CEU, CEU Universities, Boadilla del Monte, Madrid, Spain
| | - Vanesa Alonso-Herranz
- Centro de Metabolómica y Bioanálisis (CEMBIO), Facultad de Farmacia, Universidad San Pablo-CEU, CEU Universities, Boadilla del Monte, Madrid, Spain
| | - Isabel Sánchez-Vera
- Instituto de Medicina Molecular Aplicada (IMMA), Facultad de Medicina, Universidad San Pablo-CEU, CEU Universities, Boadilla del Monte, Madrid, Spain
| | - Esther Escudero
- Instituto de Medicina Molecular Aplicada (IMMA), Facultad de Medicina, Universidad San Pablo-CEU, CEU Universities, Boadilla del Monte, Madrid, Spain
| | - Isabel A. Martín-Antoniano
- Instituto de Medicina Molecular Aplicada (IMMA), Facultad de Medicina, Universidad San Pablo-CEU, CEU Universities, Boadilla del Monte, Madrid, Spain
- Genetic and Molecular Epidemiology Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | - Jose Felipe Varona
- Servicio de Medicina Interna, Hospital Universitario Hospitales de Madrid (HM), Boadilla del Monte, Madrid, Spain
| | - Andrés Ruiz
- Servicio de Medicina Interna, Hospital Universitario Hospitales de Madrid (HM), Boadilla del Monte, Madrid, Spain
| | - Jose María Castellano
- Servicio de Medicina Interna, Hospital Universitario Hospitales de Madrid (HM), Boadilla del Monte, Madrid, Spain
| | - Úrsula Muñoz
- Instituto de Medicina Molecular Aplicada (IMMA), Facultad de Medicina, Universidad San Pablo-CEU, CEU Universities, Boadilla del Monte, Madrid, Spain
| | - María C. Sádaba
- Instituto de Medicina Molecular Aplicada (IMMA), Facultad de Medicina, Universidad San Pablo-CEU, CEU Universities, Boadilla del Monte, Madrid, Spain
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Global Increases in Human Immunodeficiency Virus Neutralization Sensitivity Due to Alterations in the Membrane-Proximal External Region of the Envelope Glycoprotein Can Be Minimized by Distant State 1-Stabilizing Changes. J Virol 2022; 96:e0187821. [PMID: 35289647 DOI: 10.1128/jvi.01878-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Binding to the receptor, CD4, drives the pretriggered, "closed" (State-1) conformation of the human immunodeficiency virus (HIV-1) envelope glycoprotein (Env) trimer ([gp120/gp41]3) into more "open" conformations. HIV-1 Env on the viral membrane is maintained in a State-1 conformation that resists binding and neutralization by commonly elicited antibodies. Premature triggering of Env before the virus engages a target cell typically leads to increased susceptibility to spontaneous inactivation or ligand-induced neutralization. Here, we showed that single amino acid substitutions in the gp41 membrane-proximal external region (MPER) of a primary HIV-1 strain resulted in viral phenotypes indicative of premature triggering of Env to downstream conformations. Specifically, the MPER changes reduced viral infectivity and globally increased virus sensitivity to poorly neutralizing antibodies, soluble CD4, a CD4-mimetic compound, and exposure to cold. In contrast, the MPER mutants exhibited decreased sensitivity to the State 1-preferring inhibitor, BMS-806, and to the PGT151 broadly neutralizing antibody. Depletion of cholesterol from virus particles did not produce the same State 1-destabilizing phenotypes as MPER alterations. Notably, State 1-stabilizing changes in Env distant from the MPER could minimize the phenotypic effects of MPER alteration but did not affect virus sensitivity to cholesterol depletion. Thus, membrane-proximal gp41 elements contribute to the maintenance of the pretriggered Env conformation. The conformationally disruptive effects of MPER changes can be minimized by distant State 1-stabilizing Env modifications, a strategy that may be useful in preserving the native pretriggered state of Env. IMPORTANCE The pretriggered shape of the human immunodeficiency virus (HIV-1) envelope glycoprotein (Env) is a major target for antibodies that can neutralize many strains of the virus. An effective HIV-1 vaccine may need to raise these types of antibodies, but this goal has proven difficult. One reason is that the pretriggered shape of Env is unstable and dependent on interactions near the viral membrane. Here, we showed that the membrane-proximal external region (MPER) of Env plays an important role in maintaining Env in a pretriggered shape. Alterations in the MPER resulted in global changes in Env conformation that disrupted its pretriggered shape. We also found that these disruptive effects of MPER changes could be minimized by distant Env modifications that stabilized the pretriggered shape. These modifications may be useful for preserving the native shape of Env for structural and vaccine studies.
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Topological analysis of the gp41 MPER on lipid bilayers relevant to the metastable HIV-1 envelope prefusion state. Proc Natl Acad Sci U S A 2019; 116:22556-22566. [PMID: 31624123 DOI: 10.1073/pnas.1912427116] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The membrane proximal external region (MPER) of HIV-1 envelope glycoprotein (gp) 41 is an attractive vaccine target for elicitation of broadly neutralizing antibodies (bNAbs) by vaccination. However, current details regarding the quaternary structural organization of the MPER within the native prefusion trimer [(gp120/41)3] are elusive and even contradictory, hindering rational MPER immunogen design. To better understand the structural topology of the MPER on the lipid bilayer, the adjacent transmembrane domain (TMD) was appended (MPER-TMD) and studied. Membrane insertion of the MPER-TMD was sensitive both to the TMD sequence and cytoplasmic residues. Antigen binding of MPER-specific bNAbs, in particular 10E8 and DH511.2_K3, was significantly impacted by the presence of the TMD. Furthermore, MPER-TMD assembly into 10-nm diameter nanodiscs revealed a heterogeneous membrane array comprised largely of monomers and dimers, as enumerated by bNAb Fab binding using single-particle electron microscopy analysis, arguing against preferential trimeric association of native MPER and TMD protein segments. Moreover, introduction of isoleucine mutations in the C-terminal heptad repeat to induce an extended MPER α-helical bundle structure yielded an antigenicity profile of cell surface-arrayed Env variants inconsistent with that found in the native prefusion state. In line with these observations, electron paramagnetic resonance analysis suggested that 10E8 inhibits viral membrane fusion by lifting the MPER N-terminal region out of the viral membrane, mandating the exposure of residues that would be occluded by MPER trimerization. Collectively, our data suggest that the MPER is not a stable trimer, but rather a dynamic segment adapted for structural changes accompanying fusion.
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Stern Z, Stylianou DC, Kostrikis LG. The development of inovirus-associated vector vaccines using phage-display technologies. Expert Rev Vaccines 2019; 18:913-920. [PMID: 31373843 PMCID: PMC7103683 DOI: 10.1080/14760584.2019.1651649] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 07/31/2019] [Indexed: 01/25/2023]
Abstract
Introduction: Inovirus-associated vectors (IAVs) are derived from bacterial filamentous viruses (phages). As vaccine carriers, they have elicited both cellular and humoral responses against a variety of pathogens causing infectious diseases and other non-infectious diseases. By displaying specific antigen epitopes or proteins on their coat proteins, IAVs have merited much study, as their unique abilities are exploited for widespread vaccine development. Areas covered: The architectural traits of filamentous viruses and their derivatives, IAVs, facilitate the display of specific antigenic peptides which induce antibody production to prevent or curtail infection. Inoviruses provide a foundation for cost-efficient large-scale specific phage display. In this paper, the development of different applications of inovirus-based phage display vaccines across a broad range of pathogens and hosts is reviewed. The references cited in this review were selected from established databases based on the authors' knowledge of the study subject. Expert commentary: The importance of phage-display technology has been recently highlighted by the Nobel Prize in Chemistry 2018 awarded to George P. Smith and Sir Gregory P. Winter. Furthermore, the symbiotic nature of filamentous viruses infecting intestinal F+E. coli strains offers an attractive platform for the development of novel vaccines that stimulate mucosal immunity.
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Affiliation(s)
- Zachariah Stern
- Department of Biological Sciences, University of Cyprus, Nicosia, Cyprus
| | - Dora C. Stylianou
- Department of Biological Sciences, University of Cyprus, Nicosia, Cyprus
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Rujas E, Caaveiro JMM, Insausti S, García-Porras M, Tsumoto K, Nieva JL. Peripheral Membrane Interactions Boost the Engagement by an Anti-HIV-1 Broadly Neutralizing Antibody. J Biol Chem 2017; 292:5571-5583. [PMID: 28213514 DOI: 10.1074/jbc.m117.775429] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 02/16/2017] [Indexed: 12/16/2022] Open
Abstract
The 4E10 antibody displays an extreme breadth of HIV-1 neutralization and therefore constitutes a suitable model system for structure-guided vaccine design and immunotherapeutics against AIDS. In this regard, the relevance of autoreactivity with membrane lipids for the biological function of this antibody is still a subject of controversy. To address this dispute, herein we have compared the membrane partitioning ability of the 4E10 antibody and several of its variants, which were mutated at the region of the paratope surface in contact with the membrane interface. We first employed a physical separation approach (vesicle flotation) and subsequently carried out quantitative fluorescence measurements in an intact system (spectroscopic titration), using 4E10 Fab labeled with a polarity-sensitive fluorescent probe. Moreover, recognition of epitope peptide in membrane was demonstrated by photo-cross-linking assays using a Fab that incorporated the genetically encoded unnatural amino acid p-benzoylphenylalanine. The experimental data ruled out that the proposed stereospecific recognition of viral lipids was necessary for the function of the antibody. In contrast, our data suggest that nonspecific electrostatic interactions between basic residues of 4E10 and acidic phospholipids in the membranes contribute to the observed biological function. Moreover, the energetics of membrane partitioning indicated that 4E10 behaves as a peripheral membrane protein, tightening the binding to the ligand epitope inserted in the viral membrane. The implications of these findings for the natural production and biological function of this antibody are discussed.
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Affiliation(s)
- Edurne Rujas
- From the Biofisika Institute (Consejo Superior de Investigaciones Científicas, UPV/EHU), and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), 48080 Bilbao, Spain and.,the Department of Bioengineering, Graduate School of Engineering, University of Tokyo, Tokyo, 113-8656, Japan
| | - José M M Caaveiro
- the Department of Bioengineering, Graduate School of Engineering, University of Tokyo, Tokyo, 113-8656, Japan
| | - Sara Insausti
- From the Biofisika Institute (Consejo Superior de Investigaciones Científicas, UPV/EHU), and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), 48080 Bilbao, Spain and
| | - Miguel García-Porras
- From the Biofisika Institute (Consejo Superior de Investigaciones Científicas, UPV/EHU), and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), 48080 Bilbao, Spain and
| | - Kouhei Tsumoto
- the Department of Bioengineering, Graduate School of Engineering, University of Tokyo, Tokyo, 113-8656, Japan
| | - José L Nieva
- From the Biofisika Institute (Consejo Superior de Investigaciones Científicas, UPV/EHU), and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), 48080 Bilbao, Spain and
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Generation of Long-Lived Bone Marrow Plasma Cells Secreting Antibodies Specific for the HIV-1 gp41 Membrane-Proximal External Region in the Absence of Polyreactivity. J Virol 2016; 90:8875-90. [PMID: 27466419 PMCID: PMC5021391 DOI: 10.1128/jvi.01089-16] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 07/18/2016] [Indexed: 12/28/2022] Open
Abstract
UNLABELLED An effective preventive vaccine is highly sought after in order to stem the current HIV-1 pandemic. Both conservation of contiguous gp41 membrane-proximal external region (MPER) amino acid sequences across HIV-1 clades and the ability of anti-MPER broadly neutralizing antibodies (BNAbs) to block viral hemifusion/fusion establish the MPER as a prime vaccination target. In earlier studies, we described the development of an MPER vaccine formulation that takes advantage of liposomes to array the MPER on a lipid bilayer surface, paralleling its native configuration on the virus membrane while also incorporating molecular adjuvant and CD4 T cell epitope cargo. Here we demonstrate that several immunizations with MPER/liposomes induce high levels of bone marrow long-lived plasma cell (LLPC) antibody production. Single-cell immunoglobulin gene retrieval analysis shows that these plasma cells are derived from a germ line repertoire of B cells with a diverse representation of immunoglobulin genes, exhibiting antigen-driven positive selection. Characterization of LLPC recombinant monoclonal antibodies (rMAbs) indicates that antigen recognition is achieved through convergence on a common epitopic focus by utilizing various complementarity-determining region H3 (CDRH3) lengths. Importantly, the vast majority of rMAbs produced from these cells lack polyreactivity yet manifest antigen specificity in the context of lipids, shaping MPER-specific paratopes through selective pressure. Taken together, these findings demonstrate that the MPER is a vaccine target with minimal risk of generating off-target autoimmunity. IMPORTANCE A useful vaccine must generate desired long-term, antigen-specific antibody responses devoid of polyreactivity or autoreactivity. The common polyreactive features of some HIV-1 BNAbs have raised concern about elicitation of anti-MPER antibodies. Utilizing single-LLPC repertoire analysis and biophysical characterization of anti-MPER rMAbs, we show that their fine specificities require a structural fitness of the antibody combining site involving heavy and light chain variable domains shaped by somatic hypermutation and affinity maturation of B cells in the germinal center. Perhaps more importantly, our results demonstrate that the majority of MPER-specific antibodies are not inherently polyspecific and/or autoreactive, suggesting that polyreactivity of MPER-specific antibodies is separable from their antigen specificity.
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Hassapis KA, Stylianou DC, Kostrikis LG. Architectural insight into inovirus-associated vectors (IAVs) and development of IAV-based vaccines inducing humoral and cellular responses: implications in HIV-1 vaccines. Viruses 2014; 6:5047-76. [PMID: 25525909 PMCID: PMC4276942 DOI: 10.3390/v6125047] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 12/08/2014] [Accepted: 12/09/2014] [Indexed: 12/21/2022] Open
Abstract
Inovirus-associated vectors (IAVs) are engineered, non-lytic, filamentous bacteriophages that are assembled primarily from thousands of copies of the major coat protein gp8 and just five copies of each of the four minor coat proteins gp3, gp6, gp7 and gp9. Inovirus display studies have shown that the architecture of inoviruses makes all coat proteins of the inoviral particle accessible to the outside. This particular feature of IAVs allows foreign antigenic peptides to be displayed on the outer surface of the virion fused to its coat proteins and for more than two decades has been exploited in many applications including antibody or peptide display libraries, drug design, and vaccine development against infectious and non-infectious diseases. As vaccine carriers, IAVs have been shown to elicit both a cellular and humoral response against various pathogens through the display of antibody epitopes on their coat proteins. Despite their high immunogenicity, the goal of developing an effective vaccine against HIV-1 has not yet materialized. One possible limitation of previous efforts was the use of broadly neutralizing antibodies, which exhibited autoreactivity properties. In the past five years, however, new, more potent broadly neutralizing antibodies that do not exhibit autoreactivity properties have been isolated from HIV-1 infected individuals, suggesting that vaccination strategies aimed at producing such broadly neutralizing antibodies may confer protection against infection. The utilization of these new, broadly neutralizing antibodies in combination with the architectural traits of IAVs have driven the current developments in the design of an inovirus-based vaccine against HIV-1. This article reviews the applications of IAVs in vaccine development, with particular emphasis on the design of inoviral-based vaccines against HIV-1.
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Affiliation(s)
- Kyriakos A Hassapis
- Department of Biological Sciences, University of Cyprus, 75 Kallipoleos Avenue, 1678 Nicosia, Cyprus.
| | - Dora C Stylianou
- Department of Biological Sciences, University of Cyprus, 75 Kallipoleos Avenue, 1678 Nicosia, Cyprus.
| | - Leondios G Kostrikis
- Department of Biological Sciences, University of Cyprus, 75 Kallipoleos Avenue, 1678 Nicosia, Cyprus.
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Garg H, Viard M, Jacobs A, Blumenthal R. Targeting HIV-1 gp41-induced fusion and pathogenesis for anti-viral therapy. Curr Top Med Chem 2012; 11:2947-58. [PMID: 22044225 DOI: 10.2174/156802611798808479] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Revised: 02/28/2011] [Accepted: 12/01/2011] [Indexed: 11/22/2022]
Abstract
HIV gp41 is a metastable protein whose native conformation is maintained in the form of a heterodimer with gp120. The non-covalently associated gp41/gp120 complex forms a trimer on the virus surface. As gp120 engages with HIV's receptor, CD4, and coreceptor, CXCR4 or CCR5, gp41 undergoes several conformational changes resulting in fusion between the viral and cellular membranes. Several lipophilic and amphiphilic domains have been shown to be critical in that process. While the obvious function of gp41 in viral entry is well-established its role in cellular membrane fusion and the link with pathogenesis are only now beginning to appear. Recent targeting of gp41 via fusion inhibitors has revealed an important role of this protein not only in viral entry but also in bystander apoptosis and HIV pathogenesis. Studies by our group and others have shown that the phenomenon of gp41-mediated hemifusion initiates apoptosis in bystander cells and correlates with virus pathogenesis. More interestingly, recent clinical evidence suggests that gp41 mutants arising after Enfuvirtide therapy are associated with CD4 cell increase and immunological benefits. This has in turn been correlated to a decrease in bystander apoptosis in our in vitro as well as in vivo assays. Although a great deal of work has been done to unravel HIV-1 gp41-mediated fusion mechanisms, the factors that regulate gp41-mediated fusion versus hemifusion and the mechanism by which hemifusion initiates bystander apoptosis are not fully understood. Further insight into these issues will open new avenues for drug development making gp41 a critical anti-HIV target both for neutralization and virus attenuation.
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Affiliation(s)
- Himanshu Garg
- Center of Excellence for Infectious Disease, Department of Biomedical Sciences, Texas Tech University Health Sciences Center, El Paso, TX 79905, USA
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An anti-phosphoinositide-specific monoclonal antibody that neutralizes HIV-1 infection of human monocyte-derived macrophages. Virology 2012; 430:110-9. [PMID: 22633000 DOI: 10.1016/j.virol.2012.04.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Revised: 04/12/2012] [Accepted: 04/24/2012] [Indexed: 11/20/2022]
Abstract
HIV-1 entry into cells requires the interaction of both HIV-1 envelope proteins and membrane lipids. We investigated the mechanism of neutralization of HIV-1 infection of primary monocyte-derived macrophages (MDM) by a murine monoclonal antibody (mAb) WR321. WR321 specifically binds phosphatidylinositol-4-phosphate and phosphatidylinositol-4,5-bisphosphate. These phosphoinositides are present not only on the inner surface of the plasma membranes of cells but also on the surface of virions. HIV-1 acquires these lipids during the budding process. Pre-incubation of WR321 with the virus but not with MDM neutralized HIV-1 infection of MDM. Our results demonstrate that WR321 was internalized only when it was bound to HIV-1. WR321 did not prevent the entry of HIV-1 into MDM. However, once WR321 was internalized along with HIV-1 the mAb acted intracellulary to prevent the release of virions from MDM and also triggered the release of β-chemokines.
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Sagar M, Akiyama H, Etemad B, Ramirez N, Freitas I, Gummuluru S. Transmembrane domain membrane proximal external region but not surface unit-directed broadly neutralizing HIV-1 antibodies can restrict dendritic cell-mediated HIV-1 trans-infection. J Infect Dis 2012; 205:1248-57. [PMID: 22396600 DOI: 10.1093/infdis/jis183] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Although broadly neutralizing antibodies (bNAbs) have been shown to block a diverse array of cell-free human immunodeficiency type 1 (HIV-1) infections, it remains unclear whether these antibodies exhibit similar potency against mature dendritic cell (mDC)-mediated HIV-1 trans-infection. METHODS Sensitivity to bNAbs targeting HIV-1 envelope surface unit gp120 (VRCO1, PG16, b12, and 2G12) and transmembrane domain gp41 (4E10 and 2F5) was examined for both cell-free and mDC-mediated infections of TZM-bl and CD4(+) T cells. RESULTS Compared with cell-free infection, mDC-mediated infection was significantly less susceptible to gp120-directed bNAbs for the majority of virus isolates. A b12 antigen-binding fragment blocked both cell-free and mDC-mediated infection with equal efficiency. In contrast, cell-free and mDC-associated viruses were equally sensitive to gp41-directed bNAbs. Anti-gp41 bNAbs bound to the surface of mDCs and localized at the mDC-T cell synaptic junctions in the absence of virus. CONCLUSIONS Anti-gp41 bNAbs have the potential to inhibit mDC-mediated HIV-1 infection because they bind plasma membranes prior to the formation of an infectious synapse, positioning them to neutralize subsequent virus transfer. As opposed to gp120-directed antibodies, anti-gp41 bNAbs might prevent HIV-1 infection if transmission or spread at the initial site of invasion occurs from a DC-associated source.
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Affiliation(s)
- Manish Sagar
- Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Cambridge, MA 02139, USA.
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11
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Binding of anti-membrane-proximal gp41 monoclonal antibodies to CD4-liganded and -unliganded human immunodeficiency virus type 1 and simian immunodeficiency virus virions. J Virol 2011; 86:1820-31. [PMID: 22090143 DOI: 10.1128/jvi.05489-11] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The broadly neutralizing monoclonal antibodies (MAbs) 4E10, 2F5, and Z13e1 target membrane-proximal external region (MPER) epitopes of HIV-1 gp41 in a manner that remains controversial. The requirements for initial lipid bilayer binding and/or CD4 ligation have been proposed. To further investigate these issues, we probed for binding of these MAbs to human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV) virions with protein A-conjugated gold (PAG) nanoparticles using negative-stain electron microscopy. We found moderate levels of PAG associated with unliganded HIV-1 and SIV virions incubated with the three MAbs. Significantly higher levels of PAG were associated with CD4-liganded HIV-1 (epitope-positive) but not SIV (epitope-negative) virions. A chimeric SIV virion displaying the HIV-1 4E10 epitope also showed significantly higher PAG association after CD4 ligation and incubation with 4E10. MAbs accumulated rapidly on CD4-liganded virions and slowly on unliganded virions, although both reached similar levels in time. Anti-MPER epitope-specific binding was stable to washout. Virions incubated with an irrelevant MAb or CD4-only (no MAb) showed negligible PAG association, as did a vesicle-rich fraction devoid of virions. Preincubation with Fab 4E10 inhibited both specific and nonspecific 4E10 IgG binding. Our data provide evidence for moderate association of anti-MPER MAbs to viral surfaces but not lipid vesicles, even in the absence of cognate epitopes. Significantly greater MAb interaction occurs in epitope-positive virions following long incubation or CD4 ligation. These findings are consistent with a two-stage binding model where these anti-MPER MAbs bind first to the viral lipid bilayer and then to the MPER epitopes following spontaneous or induced exposure.
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Hardy GJ, Lam Y, Stewart SM, Anasti K, Alam SM, Zauscher S. Screening the interactions between HIV-1 neutralizing antibodies and model lipid surfaces. J Immunol Methods 2011; 376:13-9. [PMID: 22033342 DOI: 10.1016/j.jim.2011.10.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Revised: 09/20/2011] [Accepted: 10/11/2011] [Indexed: 10/16/2022]
Abstract
Our work is motivated by the observation that rare, broadly neutralizing antibodies (NAbs), 4E10 and 2F5, associate with HIV-1 lipids as part of a required first step in neutralization before binding to membrane-proximal antigens. Subsequently, induction of these types of NAbs may be limited by immunologic tolerance due to autoreactivity with host cell membranes. Despite the significance of this lipid reactivity there is little experimental evidence detailing NAb-membrane interactions. Simple and efficient screening assays are needed to select antibodies that have similar lipid reactivity as known NAbs. To this end we have developed a surface plasmon resonance (SPR) spectroscopy based assay that monitors antibody binding to thiol self-assembled monolayers (SAMs) that replicate salient lipid surface chemistries and NAb binding to lipid surfaces. Specifically, we probed the relative importance of charge and hydrophobicity on antibody-surface interactions. We found that NAb binding to hydrophobic thiol surfaces was significantly greater than that of control monoclonal antibodies (mAbs). Furthermore, we confirmed the importance of charge-mediated antibody surface interactions, originally suggested by results from mAb interactions with conventional lipid vesicle/bilayer surfaces. Our approach, using self-assembled thiol monolayers that replicate the binding behavior of NAbs on lipid surfaces, thus provides an efficient and useful tool to screen interactions of mAbs and lipid-reactive NAbs.
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Affiliation(s)
- Gregory J Hardy
- Mechanical Engineering and Materials Science, Duke University, Durham, NC, USA
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Kim M, Sun ZYJ, Rand KD, Shi X, Song L, Cheng Y, Fahmy AF, Majumdar S, Ofek G, Yang Y, Kwong PD, Wang JH, Engen JR, Wagner G, Reinherz EL. Antibody mechanics on a membrane-bound HIV segment essential for GP41-targeted viral neutralization. Nat Struct Mol Biol 2011; 18:1235-43. [PMID: 22002224 PMCID: PMC3253551 DOI: 10.1038/nsmb.2154] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Accepted: 08/09/2011] [Indexed: 11/08/2022]
Abstract
Broadly neutralizing antibodies such as 2F5 are directed against the membrane-proximal external region (MPER) of HIV-1 GP41 and recognize well-defined linear core sequences. These epitopes can be engrafted onto protein scaffolds to serve as immunogens with high structural fidelity. Although antibodies that bind to this core GP41 epitope can be elicited, they lack neutralizing activity. To understand this paradox, we used biophysical methods to investigate the binding of human 2F5 to the MPER in a membrane environment, where it resides in vivo. Recognition is stepwise, through a paratope more extensive than core binding site contacts alone, and dynamic rearrangement through an apparent scoop-like movement of heavy chain complementarity-determining region 3 (CDRH3) is essential for MPER extraction from the viral membrane. Core-epitope recognition on the virus requires the induction of conformational changes in both the MPER and the paratope. Hence, target neutralization through this lipid-embedded viral segment places stringent requirements on the plasticity of the antibody combining site.
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Affiliation(s)
- Mikyung Kim
- Laboratory of Immunobiology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA
- Department of Medicine, Harvard Medical School, Boston, MA 02115, USA
| | - Zhen-Yu J. Sun
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Kasper D. Rand
- Department of Chemistry & Chemical Biology and The Barnett Institute of Chemical & Biological Analysis, Northeastern University, Boston, MA 02115, USA
| | - Xiaomeng Shi
- Department of Chemistry & Chemical Biology and The Barnett Institute of Chemical & Biological Analysis, Northeastern University, Boston, MA 02115, USA
| | - Likai Song
- Department of Medicine, Harvard Medical School, Boston, MA 02115, USA
- Cancer Vaccine Center, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA
- National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA
| | - Yuxing Cheng
- Laboratory of Immunobiology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA
- PhD Program in Biological Sciences in Public Health, Harvard School of Public Health, Boston, MA 02115, USA
| | - Amr F. Fahmy
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Shreoshi Majumdar
- Laboratory of Immunobiology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Gilad Ofek
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Yongping Yang
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Peter D. Kwong
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jia-huai Wang
- Laboratory of Immunobiology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA
- Department of Medicine, Harvard Medical School, Boston, MA 02115, USA
- Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA
| | - John R. Engen
- Department of Chemistry & Chemical Biology and The Barnett Institute of Chemical & Biological Analysis, Northeastern University, Boston, MA 02115, USA
| | - Gerhard Wagner
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Ellis L. Reinherz
- Laboratory of Immunobiology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA
- Department of Medicine, Harvard Medical School, Boston, MA 02115, USA
- Cancer Vaccine Center, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA
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Maeso R, Huarte N, Julien JP, Kunert R, Pai EF, Nieva JL. Interaction of anti-HIV type 1 antibody 2F5 with phospholipid bilayers and its relevance for the mechanism of virus neutralization. AIDS Res Hum Retroviruses 2011; 27:863-76. [PMID: 21142698 DOI: 10.1089/aid.2010.0265] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Broadly neutralizing monoclonal antibody (MAb) 2F5 targets a linear epitope within the highly conserved membrane proximal external region (MPER) of the HIV-1 envelope protein gp41 integral subunit. Prospective vaccine developments warrant efforts currently underway to unveil the mechanistic and structural basis of its mode of action. One open question relates to the putative role that membrane phospholipids might play in the neutralization process. In this work, we establish experimental conditions that allow monitoring 2F5 insertion into lipid bilayers. Then, we compare the abilities of 2F5-based MAb, Fabs, and 2F5-specific antibodies recovered from immunized rabbits to directly penetrate into lipid bilayers and block the lytic activity of MPER-derived peptides. Antibody insertion induced membrane perturbation, which was blocked on interacting with the peptide epitope, thereby suggesting that such phenomenon was primarily mediated by the epitope-binding site. The long, hydrophobic complementarity-determining region (CDR)-H3 loop contributed little to this effect. In contrast, the CDR-H3 loop was required for blocking the lytic activity of MPER-based peptides and viral neutralization. Thus, our results suggest that core epitope binding plus association with lipid bilayers are not in conjunction sufficient to support viral neutralization by 2F5. Moreover, they support a role for the CDR-H3 loop in establishing secondary interactions with lipids and/or gp41 that would block the membrane-perturbing activity of MPER during fusion.
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Affiliation(s)
- Rubén Maeso
- Biophysics Unit (CSIC-UPV/EHU) and Biochemistry and Molecular Biology Department, University of the Basque Country, Bilbao, Spain
| | - Nerea Huarte
- Biophysics Unit (CSIC-UPV/EHU) and Biochemistry and Molecular Biology Department, University of the Basque Country, Bilbao, Spain
| | | | - Renate Kunert
- Institute of Applied Microbiology, University of Agriculture, Vienna, Austria
| | - Emil F. Pai
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- Department of Medical Biophysics and Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Campbell Family Cancer Research Institute, Ontario Cancer Institute/Princess Margaret Hospital, Toronto, Ontario, Canada
| | - José L. Nieva
- Biophysics Unit (CSIC-UPV/EHU) and Biochemistry and Molecular Biology Department, University of the Basque Country, Bilbao, Spain
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Antigen-specific enhancement of natural human IgG antibodies to phosphatidylcholine, phosphatidylglycerol, phosphatidylinositol-4-phosphate, cholesterol, and lipid A by a liposomal vaccine containing lipid A. Vaccine 2011; 29:5137-44. [PMID: 21624414 DOI: 10.1016/j.vaccine.2011.05.042] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Revised: 05/06/2011] [Accepted: 05/13/2011] [Indexed: 01/23/2023]
Abstract
Natural IgG antibodies (NA) to lipids are ubiquitously distributed in sera of healthy humans and are believed to serve beneficial functions. Although NA to lipids generally exhibit germ line or near germ line binding specificities, the antibodies commonly increase transiently in the acute phases of most, if not all, infectious diseases and may serve as a first line of defense. In order to determine whether similar anti-lipid antibodies can be induced by a vaccine in humans, we examined stored sera obtained from volunteers who had previously received a candidate vaccine to Plasmodium falciparum. The vaccine had consisted of liposomes that contained both the recombinant protein antigen and also contained monophosphoryl lipid A (MPLA) as an adjuvant. All of the pre-immune sera contained NA to one or more of the liposomal lipids in the vaccine: dimyristol phosphatidylcholine (DMPC), dimyristoyl phosphatidylglycerol (DMPG), cholesterol, and MPLA. After initial immunization, followed by a boost, increased levels of IgG antibodies to all of the liposomal lipids, especially DMPG and MPLA, were observed by ELISA. Antibodies to phosphatidylinositol-4-phosphate (PIP) above the normal pre-immune NA to PIP were also observed. Although PIP was not present in the immunizing liposomes, based on the adsorption of anti-PIP antibodies by DMPG the anti-PIP antibodies were thought to represent cross-reacting anti-DMPG antibodies. The immune response was apparently antigen-specific in that NA to unrelated lipids, other than PIP, that were not present in the liposomes, galactosyl ceramide and ganglioside GM1, were not increased by the immunization. We conclude that antibodies to DMPC, DMPG, PIP, cholesterol, and MPLA can be induced in humans by immunization with liposomes containing MPLA.
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Peachman KK, Wieczorek L, Matyas GR, Polonis VR, Alving CR, Rao M. The importance of antibody isotype in HIV-1 virus capture assay and in TZM-bl neutralization. Viral Immunol 2011; 23:627-32. [PMID: 21142448 DOI: 10.1089/vim.2010.0061] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The binding of murine IgM mAbs to five different clades of HIV-1 was examined using a modified ELISA-based virus capture assay. Two murine multispecific IgM mAbs that exhibit both lipid and gp41 epitope specificities, and one murine IgM mAb that exhibits lipid-binding specificity, were utilized. The binding of the IgG and the IgM isotypes of human mAb 2F5 to clades A through AE were also evaluated. The binding of 2F5 to HIV-1 was dependent upon the antibody isotype. Monoclonal IgM antibodies bound significantly lower amounts of HIV-1 than the corresponding IgG isotype. Although murine IgM mAbs bound HIV-1 to varying degrees in the virus capture assay, they failed to neutralize HIV-1 in a TZM-bl pseudovirus assay. In contrast, 2F5-IgM mAb bound certain HIV-1 isolates, and also neutralized them, although not as efficiently as the 2F5-IgG isotype. Studies on the relationship between virus binding and neutralization in a TZM-bl pseudovirus assay indicated that in most cases, mAbs that exhibited neutralization also bound the virus.
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Affiliation(s)
- Kristina K Peachman
- Henry M. Jackson Foundation for the Advancement of Military Medicine, Rockville, Maryland, USA
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17
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Abstract
OBJECTIVES 2F5 and 4E10 are two broadly neutralizing monoclonal antibodies (mAbs) targeting the membrane proximal external region (MPER) of HIV-1 gp41 envelope protein. This region, which contacts the viral membrane, is highly conserved and has been regarded as a promising target for vaccine development. We aimed to clarify the basis of 2F5 and 4E10 molecular interactions with epitope cores in MPER and lipid bilayers. DESIGN Microscopy-based approaches were used to infer and quantify the effects of both mAbs on membranes, in the presence and absence of the epitope cores. Supported lipid bilayers (SLBs), with and without phase separation, were used as membrane models. Fluorescent-labeled and nonlabeled MPER-derived peptides containing both 2F5 and 4E10 epitopes were used. METHODS mAbs 2F5 and 4E10 membrane interactions, in the presence or absence of MPER-derived peptides, were evaluated by combined atomic force and confocal microscopies. RESULTS Both mAbs form lipid-segregated aggregates on SLBs and do not induce other significant membrane perturbations. Furthermore, the affinity of MPER toward membranes is differently affected by both mAbs and correlates with the mAbs-epitope core lipid interactions. 2F5 is able to dock the MPER peptide on the membrane, whereas 4E10 extracts the MPER from the lipid bilayer. CONCLUSION The results reveal the molecular details underneath 2F5/4E10 membrane-epitope binding and a model is proposed to explain the differential mAbs neutralization efficacies, which relates to the exposure of the epitopes in the lipid bilayers and the role of the lipids in mAb-epitope binding.
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18
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Nonneutralizing HIV-1 gp41 envelope cluster II human monoclonal antibodies show polyreactivity for binding to phospholipids and protein autoantigens. J Virol 2010; 85:1340-7. [PMID: 21106741 DOI: 10.1128/jvi.01680-10] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
HIV-1 gp41 envelope antibodies, which are frequently induced in HIV-1-infected individuals, are predominantly nonneutralizing. The rare and difficult-to-induce neutralizing antibodies (2F5 and 4E10) that target gp41 membrane-proximal epitopes (MPER) are polyspecific and require lipid binding for HIV-1 neutralization. These results raise the questions of how prevalent polyreactivity is among gp41 antibodies and how the binding properties of gp41-nonneutralizing antibodies differ from those of antibodies that are broadly neutralizing. In this study, we have characterized a panel of human gp41 antibodies with binding specificities within the immunodominant cluster I (gp41 amino acids [aa] 579 to 613) or cluster II (gp41 aa 644 to 667) for reactivity to autoantigens, to the gp140 protein, and with MPER peptide-lipid conjugates. We report that while none of the gp41 cluster I antibodies studied were polyspecific, all three gp41 cluster II antibodies bound either to lipids or autoantigens, thus showing the propensity of cluster II antibodies to manifest polyreactivity. All cluster II gp41 monoclonal antibodies (MAbs), including those that were lipid reactive, failed to bind to gp41 MPER peptide-lipid complexes. Cluster II antibodies bound strongly with nanomolar binding affinity (dissociation constant [K(d)]) to oligomeric gp140 proteins, and thus, they recognize conformational epitopes on gp41 that are distinct from those of neutralizing gp41 antibodies. These results demonstrate that lipid-reactive gp41 cluster II antibodies are nonneutralizing due to their inability to bind to the relevant neutralizing epitopes on gp41.
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19
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The effect of sCD4 on the binding and accessibility of HIV-1 gp41 MPER epitopes to human monoclonal antibodies. Virology 2010; 408:213-23. [PMID: 20961591 DOI: 10.1016/j.virol.2010.09.029] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Revised: 07/13/2010] [Accepted: 09/23/2010] [Indexed: 11/23/2022]
Abstract
Two human monoclonal anti-HIV-1 antibodies, 2F5 and 4E10, were utilized to investigate the accessibility and conservation of gp41 MPER epitopes on five different clades of HIV-1 in the absence and presence of sCD4. The binding of human monoclonal antibodies (mAbs) to HIV-1 was dependent upon the virus clade. Soluble CD4 significantly increased the accessibility of gp41 MPER-binding epitopes on several isolates that previously showed little or no binding with 2F5 and 4E10 mAbs as determined by a modified ELISA-based virus capture assay and surface plasmon resonance. Studies on the relationship between virus binding and neutralization in a TZM-bl pseudovirus assay indicated that in most cases, mAbs that exhibited neutralization also bound the virus. However, neither binding per se nor the total envelope content per virion was a predictor of neutralization. The hidden or conformational gp41 MPER epitopes unmasked by sCD4 may provide additional targets for vaccine design.
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20
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Mohr EL, Xiang J, McLinden JH, Kaufman TM, Chang Q, Montefiori DC, Klinzman D, Stapleton JT. GB virus type C envelope protein E2 elicits antibodies that react with a cellular antigen on HIV-1 particles and neutralize diverse HIV-1 isolates. THE JOURNAL OF IMMUNOLOGY 2010; 185:4496-505. [PMID: 20826757 DOI: 10.4049/jimmunol.1001980] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Broadly neutralizing Abs to HIV-1 are well described; however, identification of Ags that elicit these Abs has proven difficult. Persistent infection with GB virus type C (GBV-C) is associated with prolonged survival in HIV-1-infected individuals, and among those without HIV-1 viremia, the presence of Ab to GBV-C glycoprotein E2 is also associated with survival. GBV-C E2 protein inhibits HIV-1 entry, and an antigenic peptide within E2 interferes with gp41-induced membrane perturbations in vitro, suggesting the possibility of structural mimicry between GBV-C E2 protein and HIV-1 particles. Naturally occurring human and experimentally induced GBV-C E2 Abs were examined for their ability to neutralize infectious HIV-1 particles and HIV-1-enveloped pseudovirus particles. All GBV-C E2 Abs neutralized diverse isolates of HIV-1 with the exception of rabbit anti-peptide Abs raised against a synthetic GBV-C E2 peptide. Rabbit anti-GBV-C E2 Abs neutralized HIV-1-pseudotyped retrovirus particles but not HIV-1-pseudotyped vesicular stomatitis virus particles, and E2 Abs immune-precipitated HIV-1 gag particles containing the vesicular stomatitis virus type G envelope, HIV-1 envelope, GBV-C envelope, or no viral envelope. The Abs did not neutralize or immune-precipitate mumps or yellow fever viruses. Rabbit GBV-C E2 Abs inhibited HIV attachment to cells but did not inhibit entry following attachment. Taken together, these data indicate that the GBV-C E2 protein has a structural motif that elicits Abs that cross-react with a cellular Ag present on retrovirus particles, independent of HIV-1 envelope glycoproteins. The data provide evidence that a heterologous viral protein can induce HIV-1-neutralizing Abs.
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Affiliation(s)
- Emma L Mohr
- Division of Infectious Diseases, Department of Internal Medicine, Iowa City Veterans Affairs Medical Center, Iowa City, IA 52242, USA
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21
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Leaman DP, Kinkead H, Zwick MB. In-solution virus capture assay helps deconstruct heterogeneous antibody recognition of human immunodeficiency virus type 1. J Virol 2010; 84:3382-95. [PMID: 20089658 PMCID: PMC2838137 DOI: 10.1128/jvi.02363-09] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Accepted: 01/06/2010] [Indexed: 01/27/2023] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (Env) on whole virions is heterogeneous, so molecular analysis of Env with monoclonal antibodies (MAbs) is challenging. Virus capture assays (VCAs) involving immobilized MAbs are typically used, but these assays suffer from immobilization artifacts and do not provide binding constants. Furthermore, we show here that certain HIV-1 neutralizing MAbs, including 2G12, 4E10, 2F5, Z13e1, and D5, will capture virion particles completely devoid of Env. We modified the VCA such that MAbs and virions are incubated in solution, and unbound MAbs are removed prior to the capture step. This modification nearly eliminated evidence of Env-independent binding by MAbs to virions and allowed determination of apparent affinity constants in solution. Three important qualitative observations were further revealed. First, neutralizing MAbs 2F5, 4E10, and Z13e1 against the membrane-proximal external region (MPER) of HIV-1 gp41 were found to capture virions efficiently only if a significant amount of uncleaved gp160 or synthetic MPER peptide was present. Second, we show how non-native forms of Env vary by Env genotype and that Env from HIV-1(JR-FL) is more homogeneously trimeric than that from HIV-1(JR-CSF). Third, we determined that Env containing all or parts of gp41, including uncleaved gp160, binds spontaneously to free virions. This exogenous Env is an indiscriminate molecular "bridge" between Env-specific Ab and virions and can affect VCA analyses, particularly using pseudotyped virions. Heterogeneity in Env from endogenous and exogenous sources might also subvert humoral immunity to HIV-1, so in-solution VCAs may help to dissect this heterogeneity for vaccine design purposes.
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Affiliation(s)
- Daniel P. Leaman
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California 92037
| | - Heather Kinkead
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California 92037
| | - Michael B. Zwick
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California 92037
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Apellaniz B, García-Sáez AJ, Huarte N, Kunert R, Vorauer-Uhl K, Katinger H, Schwille P, Nieva JL. Confocal microscopy of giant vesicles supports the absence of HIV-1 neutralizing 2F5 antibody reactivity to plasma membrane phospholipids. FEBS Lett 2010; 584:1591-6. [DOI: 10.1016/j.febslet.2010.03.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Revised: 03/12/2010] [Accepted: 03/12/2010] [Indexed: 11/26/2022]
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Ablation of the complementarity-determining region H3 apex of the anti-HIV-1 broadly neutralizing antibody 2F5 abrogates neutralizing capacity without affecting core epitope binding. J Virol 2010; 84:4136-47. [PMID: 20147404 DOI: 10.1128/jvi.02357-09] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The identification and characterization of broadly neutralizing antibodies (bnAbs) against HIV-1 has formed a major research focus, with the ultimate goal to help in the design of an effective AIDS vaccine. One of these bnAbs, 2F5, has been extensively characterized, and residues at the apex of its unusually long complementarity-determining region (CDR) H3 loop have been shown to be crucial for neutralization. Structural studies, however, have revealed that the (100)TLFGVPI(100F) apex residues of the CDR H3 loop do not interact directly with residues of its core gp41 epitope. In an attempt to gain better insight into the functional role of this element, we have recombinantly expressed native 2F5 Fab and two mutants in which either the apical Phe100B(H) residue was changed to an alanine or the CDR H3 residues (100)TLFGVPI(100F) were replaced by a Ser-Gly dipeptide linker. Isothermal titration calorimetry (ITC) and competitive-binding enzyme-linked immunosorbent assays (ELISAs) rendered strikingly similar affinity constants (K(d) [dissociation constant] of approximately 20 nM) for linear peptide epitope binding by 2F5 Fabs, independent of the presence or absence of the apex residues. Ablation of the CDR H3 apex residues, however, abolished the cell-cell fusion inhibition and pseudovirus neutralization capacities of 2F5 Fab. We report competitive ELISA data that suggest a role of 2F5 CDR H3 apex residues in mediating weak hydrophobic interactions with residues located at the C terminus of the gp41 membrane proximal external region and/or membrane components in the context of core epitope binding. The present data therefore imply an extended 2F5 paratope that includes weak secondary interactions that are crucial for neutralization of Env-mediated fusion.
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Relationship between antibody 2F5 neutralization of HIV-1 and hydrophobicity of its heavy chain third complementarity-determining region. J Virol 2009; 84:2955-62. [PMID: 20042512 DOI: 10.1128/jvi.02257-09] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The membrane-proximal external region (MPER) of the HIV-1 gp41 transmembrane glycoprotein is the target of the broadly neutralizing antibody 2F5. Prior studies have suggested a two-component mechanism for 2F5-mediated neutralization involving both structure-specific recognition of a gp41 protein epitope and nonspecific interaction with the viral lipid membrane. Here, we mutationally alter a hydrophobic patch on the third complementarity-determining region of the heavy chain (CDR H3) of the 2F5 antibody and assess the abilities of altered 2F5 variants to bind gp41 and to neutralize diverse strains of HIV-1. CDR H3 alterations had little effect on the affinity of 2F5 variants for a peptide corresponding to its gp41 epitope. In contrast, strong effects and a high degree of correlation (P < 0.0001) were found between virus neutralization and CDR H3 hydrophobicity, as defined by predicted free energies of transfer from water to a lipid bilayer interface or to octanol. The effect of CDR H3 hydrophobicity on neutralization was independent of isolate sensitivity to 2F5, and CDR H3 variants with tryptophan substitutions were able to neutralize HIV-1 approximately 10-fold more potently than unmodified 2F5. A threshold was observed for increased hydrophobicity of the 2F5 CDR H3 loop beyond which effects on 2F5-mediated neutralization leveled off. Together, the results provide a more complete understanding of the 2F5 mechanism of HIV-1 neutralization and indicate ways to enhance the potency of MPER-directed antibodies.
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25
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de la Arada I, Julien JP, de la Torre BG, Huarte N, Andreu D, Pai EF, Arrondo JLR, Nieva JL. Structural constraints imposed by the conserved fusion peptide on the HIV-1 gp41 epitope recognized by the broadly neutralizing antibody 2F5. J Phys Chem B 2009; 113:13626-37. [PMID: 19754136 DOI: 10.1021/jp905965h] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The HIV-1 gp41 epitope recognized by the broadly neutralizing 2F5 antibody has focused much attention as a suitable target in the design of peptide immunogens. Peptides mimicking the linear 2F5 epitope (2F5ep) are however intrinsically disordered, while the structural constraints existing in the cognate gp41 native structure recognized by the antibody are presently unknown. In recent reports, we have shown that core residues of the amino-terminal fusion peptide (FP) increase MAb2F5 affinity. Here, we have inferred the sequence-specific structural constraints imposed by the FP residues on the 2F5 epitope from the comparison of two hybrid peptides: HybK3, which connects through a flexible tether residues derived from 2F5ep and FP sequences, and scrHybK3, combining 2F5ep and an FP sequence with the conserved core scrambled. Circular dichroism, conventional and two-dimensional correlation infrared spectroscopy, and X-ray diffraction studies revealed specific structural features that were dependent on the exact FP sequence, namely, (i) the production with moderate low polarity of an intermediate folded structure enriched in beta-turns and alpha-helix; (ii) the existence in this intermediate of a thermotropic conformational transition taking place at ca. 18-20 degrees C, consistent with the conversion of 3(10)-helices into beta-turn conformers; and (iii) the presence of a C-terminal alpha-helix in crystals of Fab'-peptide complexes. Those features support the existence of native-like tertiary interactions between FP and 2F5 epitope residues, which might be important to recreate when developing an effective AIDS peptide vaccine.
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Affiliation(s)
- Igor de la Arada
- Biophysics Unit (CSIC-UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain
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26
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Autoreactivity in an HIV-1 broadly reactive neutralizing antibody variable region heavy chain induces immunologic tolerance. Proc Natl Acad Sci U S A 2009; 107:181-6. [PMID: 20018688 DOI: 10.1073/pnas.0912914107] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
We previously reported that some of the rare broadly reactive, HIV-1 neutralizing antibodies are polyreactive, leading to the hypothesis that induction of these types of neutralizing antibody may be limited by immunologic tolerance. However, the notion that such antibodies are sufficiently autoreactive to trigger B cell tolerance is controversial. To test directly whether rare neutralizing HIV-1 antibodies can activate immunologic tolerance mechanisms, we generated a knock-in mouse in which the Ig heavy chain (HC) variable region rearrangement (V(H)DJ(H)) from the polyreactive and broadly neutralizing human monoclonal antibody 2F5 was targeted into the mouse Igh locus. In vitro, this insertion resulted in chimeric human/mouse 2F5 antibodies that were functionally similar to the human 2F5 antibody, including comparable reactivity to human and murine self-antigens. In vivo, the 2F5 V(H)DJ(H) insertion supported development of large- and small pre-B cells that expressed the chimeric human/mouse Igmu chain but not the production of immature B cells expressing membrane IgM. The developmental arrest exhibited in 2F5 V(H)DJ(H) knock-in mice is characteristic of other knock-in strains that express the Ig HC variable region of autoreactive antibodies and is consistent with the loss of immature B cells bearing 2F5 chimeric antibodies to central tolerance mechanisms. Moreover, homozygous 2F5 V(H)DJ(H) knock-in mice support reduced numbers of residual splenic B cells with low surface IgM density, severely diminished serum IgM levels, but normal to elevated quantities of serum IgGs that did not react with autoantigens. These features are consistent with elimination of 2F5 HC autoreactivity by additional negative selection mechanism(s) in the periphery.
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27
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Crystallographic definition of the epitope promiscuity of the broadly neutralizing anti-human immunodeficiency virus type 1 antibody 2F5: vaccine design implications. J Virol 2009; 83:11862-75. [PMID: 19740978 DOI: 10.1128/jvi.01604-09] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The quest to create a human immunodeficiency virus type 1 (HIV-1) vaccine capable of eliciting broadly neutralizing antibodies against Env has been challenging. Among other problems, one difficulty in creating a potent immunogen resides in the substantial overall sequence variability of the HIV envelope protein. The membrane-proximal region (MPER) of gp41 is a particularly conserved tryptophan-rich region spanning residues 659 to 683, which is recognized by three broadly neutralizing monoclonal antibodies (bnMAbs), 2F5, Z13, and 4E10. In this study, we first describe the variability of residues in the gp41 MPER and report on the invariant nature of 15 out of 25 amino acids comprising this region. Subsequently, we evaluate the ability of the bnMAb 2F5 to recognize 31 varying sequences of the gp41 MPER at a molecular level. In 19 cases, resulting crystal structures show the various MPER peptides bound to the 2F5 Fab'. A variety of amino acid substitutions outside the 664DKW666 core epitope are tolerated. However, changes at the 664DKW666 motif itself are restricted to those residues that preserve the aspartate's negative charge, the hydrophobic alkyl-pi stacking arrangement between the beta-turn lysine and tryptophan, and the positive charge of the former. We also characterize a possible molecular mechanism of 2F5 escape by sequence variability at position 667, which is often observed in HIV-1 clade C isolates. Based on our results, we propose a somewhat more flexible molecular model of epitope recognition by bnMAb 2F5, which could guide future attempts at designing small-molecule MPER-like vaccines capable of eliciting 2F5-like antibodies.
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Alving CR, Beck Z, Karasavva N, Matyas GR, Rao M. HIV-1, lipid rafts, and antibodies to liposomes: implications for anti-viral-neutralizing antibodies (Review). Mol Membr Biol 2009; 23:453-65. [PMID: 17127618 DOI: 10.1080/09687860600935348] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The human immunodeficiency virus type 1 (HIV-1) is an enveloped virus with a lipid bilayer that contains several glycoproteins that are anchored in, or closely associated with, the membrane surface. The envelope proteins have complex interactions with the lipids both on the host cells and on the target cells. The processes of budding from host cells and entry into target cells occur at sites on the plasma membrane, known as lipid rafts, that represent specialized regions that are rich in cholesterol and sphingolipids. Although the envelope glycoproteins are antigenic molecules that potentially might be used for development of broadly neutralizing antibodies in a vaccine to HIV-1, the development of such antibodies that have broad specificities against primary field isolates of virus has been largely thwarted to date by the ability of the envelope proteins to evade the immune system through various mechanisms. In this review, the interactions of HIV-1 with membrane lipids are summarized. Liposomes are commonly used as models for understanding interactions of proteins with membrane lipids; and liposomes have also been used both as carriers for vaccines, and as antigens for induction of antibodies to liposomal lipids. The possibility is proposed that liposomal lipids, or liposome-protein combinations, could be useful as antigens for inducing broadly neutralizing antibodies to HIV-1.
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Affiliation(s)
- Carl R Alving
- Department of Vaccine Production and Delivery, Division of Retrovirology, US Military HIV Research Program, Walter Reed Army Institute of Research, Rockville, MD 20850, USA.
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29
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Hinz A, Schoehn G, Quendler H, Hulsik DL, Stiegler G, Katinger H, Seaman MS, Montefiori D, Weissenhorn W. Characterization of a trimeric MPER containing HIV-1 gp41 antigen. Virology 2009; 390:221-7. [PMID: 19539967 DOI: 10.1016/j.virol.2009.05.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 03/17/2009] [Accepted: 05/15/2009] [Indexed: 01/08/2023]
Abstract
The membrane-proximal external region (MPER) of gp41 is considered as a prime target for the induction of neutralizing antibodies, since it contains the epitopes for three broadly neutralizing antibodies (2F5, 4E10 and Z13). Here we present a novel gp41 construct (HA-gp41) comprising gp41 HR2 and MPER fused to two triple-stranded coiled-coil domains at both ends. HA-gp41 is trimeric, has a high helical content in solution and forms rod-like structures as revealed by negative staining electron microscopy. Immunization of rabbits with HA-gp41 induced antibodies directed against MPER, which failed to exert significant neutralization capacity against envelopes from primary isolates. Thus trimerisation of MPER regions does not suffice to induce a potent neutralizing antibody response specific for conserved regions within gp41.
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Affiliation(s)
- Andreas Hinz
- Unit for Virus Host Cell Interaction, UMI 3265 UJF-EMBL-CNRS, 6 rue Jules Horowitz, 38042 Grenoble cedex 9, France
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30
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Veiga AS, Pattenden LK, Fletcher JM, Castanho MARB, Aguilar MI. Interactions of HIV-1 antibodies 2F5 and 4E10 with a gp41 epitope prebound to host and viral membrane model systems. Chembiochem 2009; 10:1032-44. [PMID: 19283693 DOI: 10.1002/cbic.200800609] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Two HIV-1 recognition domains for the human monoclonal antibodies (MAb) 2F5, which recognises the core sequence ELDKWA, and 4E10, which recognises the core sequence NWFNIT, serve as promising models for immunogens in vaccine development against HIV-1. However, the failure of these recognition domains to generate broadly reactive neutralizing antibodies, and the putative membrane-binding properties of the antibodies raised to these recognition domains, suggest that additional features or recognition motifs are required to form an efficient immunogen, which could possibly include the membrane components. In this study we used an extended peptide epitope sequence derived from the gp41 native sequence (H-NEQELLELDKWASLWNWFNITNWLWYIK-NH), which contains the two recognition domains for 2F5 and 4E10, to examine the role of model cell (POPC) and viral (POPC/cholesterol/sphingomyelin) membranes in the recognition of these two antibodies. By using a surface plasmon resonance biosensor, the binding of 2F5 and 4E10 to membranes was compared and contrasted in the presence and absence of prebound peptide epitope. The recognition of the peptide epitope by each MAb was found to be distinct; 2F5 exhibited strong and almost irreversible binding to both membranes in the presence of the peptide, but bound weakly in the absence of the peptide epitope. In contrast, 4E10 exhibited strong membrane binding in the presence or absence of the peptide epitope, and the binding was essentially irreversible in the presence of the peptide epitope. Overall, these results demonstrate that both 2F5 and 4E10 can bind to membranes prior to epitope recognition, but that high-affinity recognition of gp41-derived epitope sequences by 2F5 and 4E10 occurs in a membrane context. Moreover, 4E10 might utilise the membrane to access and bind to gp41; such membrane properties of 2F5 and 4E10 could be exploited in immunogen design.
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Affiliation(s)
- Ana S Veiga
- Instituto de Medicina Molecular, Lisboa, Portugal
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31
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Martinez V, Diemert M, Braibant M, Potard V, Charuel J, Barin F, Costagliola D, Caumes E, Clauvel J, Autran B, Musset L. Anticardiolipin Antibodies in HIV Infection Are Independently Associated with Antibodies to the Membrane Proximal External Region of gp41 and with Cell‐Associated HIV DNA and Immune Activation. Clin Infect Dis 2009; 48:123-32. [DOI: 10.1086/595013] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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32
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Julien JP, Bryson S, Nieva JL, Pai EF. Structural details of HIV-1 recognition by the broadly neutralizing monoclonal antibody 2F5: epitope conformation, antigen-recognition loop mobility, and anion-binding site. J Mol Biol 2008; 384:377-92. [PMID: 18824005 DOI: 10.1016/j.jmb.2008.09.024] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2008] [Revised: 09/05/2008] [Accepted: 09/08/2008] [Indexed: 11/25/2022]
Abstract
2F5 is a monoclonal antibody with potent and broadly neutralizing activity against HIV-1. It targets the membrane-proximal external region (MPER) of the gp41 subunit of the envelope glycoprotein and interferes with the process of fusion between viral and host cell membranes. This study presents eight 2F5 F(ab)' crystal structures in complex with various gp41 peptide epitopes. These structures reveal several key features of this antibody-antigen interaction. (1) Whenever free of contacts caused by crystal artifacts, the extended complementarity-determining region H3 loop is mobile; this is true for ligand-free and epitope-bound forms. (2) The interaction between the antibody and the gp41 ELDKWA epitope core is absolutely critical, and there are also close and specific contacts with residues located N-terminal to the epitope core. (3) Residues located at the C-terminus of the gp41 ELDKWA core do not interact as tightly with the antibody. However, in the presence of a larger peptide containing the gp41 fusion peptide segment, these residues adopt a conformation consistent with the start of an alpha-helix. (4) At high sulfate concentrations, the electron density maps of 2F5 F(ab)'-peptide complexes contain a peak that may mark a binding site for phosphate groups of negatively charged lipid headgroups. The refined atomic-level details of 2F5 paratope-epitope interactions revealed here should contribute to a better understanding of the mechanism of 2F5-based virus neutralization, in general, and prove important for the design of potential vaccine candidates intended to elicit 2F5-like antibody production.
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Affiliation(s)
- Jean-Philippe Julien
- Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8
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33
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Coûtant J, Yu H, Clément M, Alfsen A, Toma F, Curmi PA, Bomsel M. Both lipid environment and pH are critical for determining physiological solution structure of 3‐D‐conserved epitopes of the HIV‐1 gp41‐MPER peptide P1. FASEB J 2008; 22:4338-51. [DOI: 10.1096/fj.08-113142] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Jérôme Coûtant
- Structure Activité des Biomolécules Normales et PathologiquesINSERM/UEVE U829 Université d'EvryEvryFrance
| | - Huifeng Yu
- Entrée Muqueuse du VIH et Immunite Muqueuse, Departement de Biologie CellulaireInstitut Cochin, Université Paris Descartes, CNRS UMR 8104ParisFrance
- INSERM U567ParisFrance
| | - Marie‐Jeanne Clément
- Structure Activité des Biomolécules Normales et PathologiquesINSERM/UEVE U829 Université d'EvryEvryFrance
| | - Annette Alfsen
- Entrée Muqueuse du VIH et Immunite Muqueuse, Departement de Biologie CellulaireInstitut Cochin, Université Paris Descartes, CNRS UMR 8104ParisFrance
- INSERM U567ParisFrance
| | - Flavio Toma
- Structure Activité des Biomolécules Normales et PathologiquesINSERM/UEVE U829 Université d'EvryEvryFrance
| | - Patrick A. Curmi
- Structure Activité des Biomolécules Normales et PathologiquesINSERM/UEVE U829 Université d'EvryEvryFrance
| | - Morgane Bomsel
- Entrée Muqueuse du VIH et Immunite Muqueuse, Departement de Biologie CellulaireInstitut Cochin, Université Paris Descartes, CNRS UMR 8104ParisFrance
- INSERM U567ParisFrance
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34
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White JM, Delos SE, Brecher M, Schornberg K. Structures and mechanisms of viral membrane fusion proteins: multiple variations on a common theme. Crit Rev Biochem Mol Biol 2008; 43:189-219. [PMID: 18568847 DOI: 10.1080/10409230802058320] [Citation(s) in RCA: 665] [Impact Index Per Article: 41.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Recent work has identified three distinct classes of viral membrane fusion proteins based on structural criteria. In addition, there are at least four distinct mechanisms by which viral fusion proteins can be triggered to undergo fusion-inducing conformational changes. Viral fusion proteins also contain different types of fusion peptides and vary in their reliance on accessory proteins. These differing features combine to yield a rich diversity of fusion proteins. Yet despite this staggering diversity, all characterized viral fusion proteins convert from a fusion-competent state (dimers or trimers, depending on the class) to a membrane-embedded homotrimeric prehairpin, and then to a trimer-of-hairpins that brings the fusion peptide, attached to the target membrane, and the transmembrane domain, attached to the viral membrane, into close proximity thereby facilitating the union of viral and target membranes. During these conformational conversions, the fusion proteins induce membranes to progress through stages of close apposition, hemifusion, and then the formation of small, and finally large, fusion pores. Clearly, highly divergent proteins have converged on the same overall strategy to mediate fusion, an essential step in the life cycle of every enveloped virus.
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Affiliation(s)
- Judith M White
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia 22908-0732, USA.
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35
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The broadly neutralizing anti-human immunodeficiency virus type 1 4E10 monoclonal antibody is better adapted to membrane-bound epitope recognition and blocking than 2F5. J Virol 2008; 82:8986-96. [PMID: 18596094 DOI: 10.1128/jvi.00846-08] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The broadly neutralizing 2F5 and 4E10 monoclonal antibodies (MAbs) recognize epitopes within the membrane-proximal external region (MPER) that connects the human immunodeficiency virus type 1 (HIV-1) envelope gp41 ectodomain with the transmembrane anchor. By adopting different conformations that stably insert into the virion external membrane interface, such as helical structures, a conserved aromatic-rich sequence within the MPER is thought to participate in HIV-1-cell fusion. Recent experimental evidence suggests that the neutralizing activity of 2F5 and 4E10 might correlate with the MAbs' capacity to recognize epitopes inserted into the viral membrane, thereby impairing MPER fusogenic activity. To gain new insights into the molecular mechanism underlying viral neutralization by these antibodies, we have compared the capacities of 2F5 and 4E10 to block the membrane-disorganizing activity of MPER peptides inserted into the surface bilayer of solution-diffusing unilamellar vesicles. Both MAbs inhibited leakage of vesicular aqueous contents (membrane permeabilization) and intervesicular lipid mixing (membrane fusion) promoted by MPER-derived peptides. Thus, our data support the idea that antibody binding to a membrane-inserted epitope may interfere with the function of the MPER during gp41-induced fusion. Antibody insertion into a cholesterol-containing, uncharged virion-like membrane is mediated by specific epitope recognition, and moreover, partitioning-coupled folding into a helix reduces the efficiency of 2F5 MAb binding to its epitope in the membrane. We conclude that the capacity to interfere with the membrane activity of conserved MPER sequences is best correlated with the broad neutralization of the 4E10 MAb.
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36
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The membrane-proximal external region of the human immunodeficiency virus type 1 envelope: dominant site of antibody neutralization and target for vaccine design. Microbiol Mol Biol Rev 2008; 72:54-84, table of contents. [PMID: 18322034 DOI: 10.1128/mmbr.00020-07] [Citation(s) in RCA: 202] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Enormous efforts have been made to produce a protective vaccine against human immunodeficiency virus type 1; there has been little success. However, the identification of broadly neutralizing antibodies against epitopes on the highly conserved membrane-proximal external region (MPER) of the gp41 envelope protein has delineated this region as an attractive vaccine target. Furthermore, emerging structural information on the MPER has provided vaccine designers with new insights for building relevant immunogens. This review describes the current state of the field regarding (i) the structure and function of the gp41 MPER; (ii) the structure and binding mechanisms of the broadly neutralizing antibodies 2F5, 4E10, and Z13; and (iii) the development of an MPER-targeting vaccine. In addition, emerging approaches to vaccine design are presented.
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37
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Cross-reactive human immunodeficiency virus type 1-neutralizing human monoclonal antibody that recognizes a novel conformational epitope on gp41 and lacks reactivity against self-antigens. J Virol 2008; 82:6869-79. [PMID: 18480433 DOI: 10.1128/jvi.00033-08] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Broadly cross-reactive human immunodeficiency virus (HIV)-neutralizing antibodies are infrequently elicited in infected humans. The two best-characterized gp41-specific cross-reactive neutralizing human monoclonal antibodies, 4E10 and 2F5, target linear epitopes in the membrane-proximal external region (MPER) and bind to cardiolipin and several other autoantigens. It has been hypothesized that, because of such reactivity to self-antigens, elicitation of 2F5 and 4E10 and similar antibodies by vaccine immunogens based on the MPER could be affected by tolerance mechanisms. Here, we report the identification and characterization of a novel anti-gp41 monoclonal antibody, designated m44, which neutralized most of the 22 HIV type 1 (HIV-1) primary isolates from different clades tested in assays based on infection of peripheral blood mononuclear cells by replication-competent virus but did not bind to cardiolipin and phosphatidylserine in an enzyme-linked immunosorbent assay and a Biacore assay nor to any protein or DNA autoantigens tested in Luminex assays. m44 bound to membrane-associated HIV-1 envelope glycoproteins (Envs), to recombinant Envs lacking the transmembrane domain and cytoplasmic tail (gp140s), and to gp41 structures containing five-helix bundles and six-helix bundles, but not to N-heptad repeat trimers, suggesting that the C-heptad repeat is involved in m44 binding. In contrast to 2F5, 4E10, and Z13, m44 did not bind to any significant degree to denatured gp140 and linear peptides derived from gp41, suggesting a conformational nature of the epitope. This is the first report of a gp41-specific cross-reactive HIV-1-neutralizing human antibody that does not have detectable reactivity to autoantigens. Its novel conserved conformational epitope on gp41 could be helpful in the design of vaccine immunogens and as a target for therapeutics.
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38
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Penn-Nicholson A, Han DP, Kim SJ, Park H, Ansari R, Montefiori DC, Cho MW. Assessment of antibody responses against gp41 in HIV-1-infected patients using soluble gp41 fusion proteins and peptides derived from M group consensus envelope. Virology 2008; 372:442-56. [PMID: 18068750 PMCID: PMC2293309 DOI: 10.1016/j.virol.2007.11.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2007] [Revised: 10/29/2007] [Accepted: 11/08/2007] [Indexed: 11/18/2022]
Abstract
Human immunodeficiency virus type 1 (HIV-1) transmembrane glycoprotein gp41 is targeted by broadly-reactive neutralizing antibodies 2F5 and 4E10, making it an attractive target for vaccine development. To better assess immunogenic properties of gp41, we generated five soluble glutathione S-transferase fusion proteins encompassing C-terminal 30, 64, 100, 142, or 172 (full-length) amino acids of gp41 ectodomain from M group consensus envelope sequence. Antibody responses in HIV-1-infected patients were evaluated using these proteins and overlapping peptides. We found (i) antibody responses against different regions of gp41 varied tremendously among individual patients, (ii) patients with stronger antibody responses against membrane-proximal external region exhibit broader and more potent neutralizing activity, and (iii) several patients mounted antibodies against epitopes that are near, or overlap with, those targeted by 2F5 or 4E10. These soluble gp41 fusion proteins could be an important source of antigens for future vaccine development efforts.
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Affiliation(s)
- Adam Penn-Nicholson
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
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39
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Lorizate M, Huarte N, Sáez-Cirión A, Nieva JL. Interfacial pre-transmembrane domains in viral proteins promoting membrane fusion and fission. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:1624-39. [PMID: 18222166 PMCID: PMC7094410 DOI: 10.1016/j.bbamem.2007.12.018] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2007] [Revised: 12/17/2007] [Accepted: 12/20/2007] [Indexed: 12/02/2022]
Abstract
Membrane fusion and fission underlie two limiting steps of enveloped virus replication cycle: access to the interior of the host-cell (entry) and dissemination of viral progeny after replication (budding), respectively. These dynamic processes proceed mediated by specialized proteins that disrupt and bend the lipid bilayer organization transiently and locally. We introduced Wimley–White membrane-water partitioning free energies of the amino acids as an algorithm for predicting functional domains that may transmit protein conformational energy into membranes. It was found that many viral products possess unusually extended, aromatic-rich pre-transmembrane stretches predicted to stably reside at the membrane interface. Here, we review structure–function studies, as well as data reported on the interaction of representative peptides with model membranes, all of which sustain a functional role for these domains in viral fusion and fission. Since pre-transmembrane sequences also constitute antigenic determinants in a membrane-bound state, we also describe some recent results on their recognition and blocking at membrane interface by neutralizing antibodies.
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Affiliation(s)
| | | | | | - José L. Nieva
- Corresponding author. Unidad de Biofísica, Universidad del País Vasco, Aptdo. 644, 48080 Bilbao, Spain. Tel.: +34 94 6013353; fax: +34 94 6013360.
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40
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Lipid A and liposomes containing lipid A as antigens and adjuvants. Vaccine 2007; 26:3036-45. [PMID: 18226433 DOI: 10.1016/j.vaccine.2007.12.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2007] [Revised: 11/30/2007] [Accepted: 12/01/2007] [Indexed: 11/23/2022]
Abstract
Lipid A derived from Gram-negative bacterial lipopolysaccharide is a potent adjuvant and antigen. Incorporation of lipid A into liposomes renders the liposomes themselves immunogenic, resulting in generation of specific antibodies that recognize either the individual liposomal lipids, or the unique pattern presented by the combination of lipids. Using liposomes containing lipid A, numerous polyclonal antisera and monoclonal antibodies have been produced against phospholipids, cholesterol, glycosphingolipids, and lipid A. Many of these antibodies have binding characteristics that are apparently similar to natural antibodies that are normally present in all human sera, and also antibodies that arise in response to various infections. Such antibodies probably represent a bridge between innate and adaptive immunity. The possible utility of liposomes containing lipid A as a constituent of certain types of novel vaccines was suggested by the observation that murine monoclonal antibodies to liposomal phosphatidylinositol-4-phosphate neutralized primary isolates of two different clades of HIV-1 in a human peripheral blood mononuclear cell neutralization assay.
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41
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Alam SM, McAdams M, Boren D, Rak M, Scearce RM, Gao F, Camacho ZT, Gewirth D, Kelsoe G, Chen P, Haynes BF. The role of antibody polyspecificity and lipid reactivity in binding of broadly neutralizing anti-HIV-1 envelope human monoclonal antibodies 2F5 and 4E10 to glycoprotein 41 membrane proximal envelope epitopes. THE JOURNAL OF IMMUNOLOGY 2007; 178:4424-35. [PMID: 17372000 PMCID: PMC2262928 DOI: 10.4049/jimmunol.178.7.4424] [Citation(s) in RCA: 207] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Two neutralizing human mAbs, 2F5 and 4E10, that react with the HIV-1 envelope gp41 membrane proximal region are also polyspecific autoantibodies that bind to anionic phospholipids. To determine the autoantibody nature of these Abs, we have compared their reactivities with human anti-cardiolipin mAbs derived from a primary antiphospholipid syndrome patient. To define the role of lipid polyreactivity in binding of 2F5 and 4E10 mAbs to HIV-1 envelope membrane proximal epitopes, we determined the kinetics of binding of mAbs 2F5 and 4E10 to their nominal gp41 epitopes vs liposome-gp41 peptide conjugates. Both anti-HIV-1 mAbs 2F5 and 4E10 bound to cardiolipin with K(d) values similar to those of autoimmune anti-cardiolipin Abs, IS4 and IS6. Binding kinetics studies revealed that mAb 2F5 and 4E10 binding to their respective gp41 peptide-lipid conjugates could best be defined by a two-step (encounter-docking) conformational change model. In contrast, binding of 2F5 and 4E10 mAbs to linear peptide epitopes followed a simple Langmuir model. A mouse mAb, 13H11, that cross-blocks mAb 2F5 binding to the gp41 epitope did not cross-react with lipids nor did it neutralize HIV-1 viruses. Taken together, these data demonstrate the similarity of 2F5 and 4E10 mAbs to known anti-cardiolipin Abs and support the model that mAb 2F5 and 4E10 binding to HIV-1 involves both viral lipid membrane and gp41 membrane proximal epitopes.
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Affiliation(s)
- S. Munir Alam
- Department of Medicine, Duke University School of Medicine, Durham, NC 27710
- Address correspondence and reprint requests to Dr. Barton F. Haynes, Duke Human Vaccine Institute, Box 3258, Duke University, RP1 Circuit Drive, Room 107, Durham, NC 27710; E-mail address: or Dr. S. Munir Alam, Duke Human Vaccine Institute, Box 3258, Duke University, RP1 Circuit Drive, Room 107, Durham, NC 27710; E-mail address:
| | - Mildred McAdams
- Department of Medicine, Duke University School of Medicine, Durham, NC 27710
| | - David Boren
- Department of Medicine, Duke University School of Medicine, Durham, NC 27710
| | - Michael Rak
- Department of Medicine, Duke University School of Medicine, Durham, NC 27710
| | - Richard M. Scearce
- Department of Medicine, Duke University School of Medicine, Durham, NC 27710
| | - Feng Gao
- Department of Medicine, Duke University School of Medicine, Durham, NC 27710
| | - Zenaido T. Camacho
- Department of Medicine, Duke University School of Medicine, Durham, NC 27710
| | - Daniel Gewirth
- Department of Medicine, Duke University School of Medicine, Durham, NC 27710
| | - Garnett Kelsoe
- Department of Medicine, Duke University School of Medicine, Durham, NC 27710
| | - Pojen Chen
- Department of Medicine, University of California, Los Angeles, CA 90095
| | - Barton F. Haynes
- Department of Medicine, Duke University School of Medicine, Durham, NC 27710
- Address correspondence and reprint requests to Dr. Barton F. Haynes, Duke Human Vaccine Institute, Box 3258, Duke University, RP1 Circuit Drive, Room 107, Durham, NC 27710; E-mail address: or Dr. S. Munir Alam, Duke Human Vaccine Institute, Box 3258, Duke University, RP1 Circuit Drive, Room 107, Durham, NC 27710; E-mail address:
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42
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Brown BK, Karasavvas N, Beck Z, Matyas GR, Birx DL, Polonis VR, Alving CR. Monoclonal antibodies to phosphatidylinositol phosphate neutralize human immunodeficiency virus type 1: role of phosphate-binding subsites. J Virol 2006; 81:2087-91. [PMID: 17151131 PMCID: PMC1797582 DOI: 10.1128/jvi.02011-06] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Both a murine monoclonal antibody to phosphatidylinositol phosphate (PIP) and a human monoclonal antibody (4E10) that is known to have broadly neutralizing capabilities against primary isolates of human immunodeficiency virus type 1 (HIV-1) bound to PIP, as determined by enzyme-linked immunosorbent assay. Each of the antibodies had antigen subsite binding specificities in aqueous medium for small phosphate-containing molecules and for inositol. The anti-PIP monoclonal antibody inhibited infection by two HIV-1 primary isolates in neutralization assays employing primary human peripheral blood mononuclear cells. The data suggest that PIP or related lipids having free phosphates could serve as targets for the neutralization of HIV-1.
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Affiliation(s)
- Bruce K Brown
- Henry M. Jackson Foundation, 13 Taft Court, Rockville, Maryland 20850, USA
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