51
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Barnes E, Lauer G, Walker B, Klenerman P. T cell failure in hepatitis C virus infection. Viral Immunol 2003; 15:285-93. [PMID: 12081013 DOI: 10.1089/08828240260066233] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Affiliation(s)
- Eleanor Barnes
- Nuffield Department of Medicine, University of Oxford, United Kingdom.
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52
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Nacsa J, Stanton J, Kunstman KJ, Tsai WP, Watkins DI, Wolinsky SM, Franchini G. Emergence of cytotoxic T lymphocyte escape mutants following antiretroviral treatment suspension in rhesus macaques infected with SIVmac251. Virology 2003; 305:210-8. [PMID: 12504554 DOI: 10.1006/viro.2002.1753] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Structured treatment interruption (STI) of antiretroviral drugs has been proposed as an alternative approach for managing patients infected with HIV-1. While STI is thought to spare drug-related side effects and enhance the HIV-1-specific immune response, the long-lasting clinical benefit of this approach remains uncertain, particularly in patients with long-standing HIV-1 infection. Here, we investigated the basis of unabated virological replication following different STI regimens in rhesus macaques that expressed the MHC class I Mamu-A*01 molecule treated during acute and long-standing infection with SIVmac251. An amino acid change at the anchor residue within the immunodominant Mamu-A*01-restricted Gag(181-189) CM9 epitope (T --> A) in one of six macaques with acute SIVmac251 infection and in three of four macaques with long-standing SIVmac251 infection (T --> A; T --> S; S --> C) was found in the majority of plasma virus. These amino acid changes have been shown to severely decrease binding of the corresponding peptides to the Mamu-A*01 molecule and, in the case of the T --> A change, escape from CTL. In one macaque with long-standing SIVmac251 infection, a mutation emerged that conferred resistance to one of the antiretroviral drugs (PMPA) as well. These results provide insights into the mechanism underlying the limited capacity of repeated interruption of antiretroviral therapy as an approach to restrain viral replication. In addition, these data also suggest that interruption of therapy may be less effective in chronic infection because of preexisting immune escape and that immune escape is a risk of interruption of therapy.
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Affiliation(s)
- Janos Nacsa
- National Cancer Institute, Basic Research Laboratory, 41/D804, Bethesda, Maryland 20892, USA
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53
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Zhang D, Shankar P, Xu Z, Harnisch B, Chen G, Lange C, Lee SJ, Valdez H, Lederman MM, Lieberman J. Most antiviral CD8 T cells during chronic viral infection do not express high levels of perforin and are not directly cytotoxic. Blood 2003; 101:226-35. [PMID: 12393740 DOI: 10.1182/blood-2002-03-0791] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Despite the frequency of HIV-specific CD8 T cells, most HIV-infected patients do not control viral replication without antiviral drugs. Although CD8 T cells are important in containing acute HIV and simian immunodeficiency virus (SIV) infection, CD8 T-cell functions are compromised in chronic infection. To investigate whether functional deficits are specific to HIV, the phenotypic and functional properties of HIV, Epstein-Barr virus (EBV), and cytomegalovirus (CMV)-specific CD8 T cells, labeled with HLA A2.1 or B8 tetramers, were compared in 35 HIV-infected and 9 healthy donors. Cytotoxic T lymphocytes express the cytolytic molecules perforin and granzymes, and are thought to be CD45RA(+)CD27(-). Although most HIV- specific cells are antigen experienced and express granzyme A (median, 85%), few express high levels of perforin (median, 10%) or CD45RA (median, 14%) or have down-modulated CD27 (median, 12%). Perforin expression by HIV-specific cells is not significantly different from that of EBV- or CMV-specific cells in the same donors or in healthy donors. EBV- and CMV-specific cells, like HIV-specific cells, are often not cytotoxic when tested directly ex vivo. HIV-specific T-cell expression of other phenotypic markers is similar to that of EBV- and CMV-specific CD8 T cells in healthy donors. However, CMV-specific cells (and, to a lesser extent, EBV-specific cells) in HIV-infected donors are more likely to be CD27(-), CD45RA(+), and GzmA(+). These results suggest that the chance to eradicate an infection by T-cell-mediated lysis may be undermined once an infection becomes chronic. Impaired antiviral cytotoxicity during chronic infection is not specific to HIV but likely represents the immune response to chronic antigenic exposure.
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Affiliation(s)
- Dong Zhang
- Center for Blood Research, Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA
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54
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Cohen GB, Islam SA, Noble MS, Lau C, Brander C, Altfeld MA, Rosenberg ES, Schmitz JE, Cameron TO, Kalams SA. Clonotype tracking of TCR repertoires during chronic virus infections. Virology 2002; 304:474-84. [PMID: 12504586 DOI: 10.1006/viro.2002.1743] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Human viral infections such as HIV and EBV typically evoke a strong and diverse CD8(+) T cell response. Relatively little is known about the extent to which TCR repertoire evolution occurs during viral infection or how repertoire evolution affects the efficacy of the CD8(+) T cell response. In this study we describe a general approach for tracking TCR repertoire evolution during viral infection. IFNgamma surface capture and MHC class I tetramer staining were independently used to isolate EBV-specific CD8(+) T cells from peripheral blood. Anchored RT-PCR and clonotype TCR repertoire analysis were performed immediately after isolating the cells. We find that the TCR repertoires of the IFNgamma-secreting and MHC class I tetramer staining populations were similar. In one subject a detailed analysis of the TCR repertoire during the first year of EBV infection was performed and over 600 TCR sequences targeting an EBV-immunodominant epitope were analyzed. Although some repertoire evolution occurred during the year, in general, the degree of repertoire drift was small. TCR repertoire analysis for an HIV-immunodominant epitope revealed a highly conserved amino acid motif in the Dbeta region of TCR that recognizes the epitope and suggested that T cell precursor frequency influences which epitopes are targeted early in HIV infection. This methodology, which allows one to sort antigen-specific T cells based on different functional assays and to obtain a snapshot of their TCR repertoire with relative ease, should lead to a richer understanding of the rules underlying antigen recognition and T cell evolution during viral infection.
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MESH Headings
- CD8-Positive T-Lymphocytes/immunology
- Cell Line
- Chronic Disease
- Epstein-Barr Virus Infections/immunology
- HIV Infections/immunology
- Herpesvirus 4, Human/immunology
- Humans
- Immunodominant Epitopes
- Interferon-gamma/biosynthesis
- Receptors, Antigen, T-Cell, alpha-beta/chemistry
- Receptors, Antigen, T-Cell, alpha-beta/genetics
- Receptors, Antigen, T-Cell, alpha-beta/immunology
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Affiliation(s)
- George B Cohen
- Partners AIDS Research Center and Infectious Disease Unit, Massachusetts General Hospital and Harvard Medical School, Boston 02129, USA.
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55
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Franchini G, Nacsa J, Hel Z, Tryniszewska E. Immune intervention strategies for HIV-1 infection of humans in the SIV macaque model. Vaccine 2002; 20 Suppl 4:A52-60. [PMID: 12477429 DOI: 10.1016/s0264-410x(02)00388-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Studies in the SIVmac macaque model have demonstrated that the extent of virus-specific CD4+ and CD8+ T-cell responses induced by vaccination prior to virus-challenge exposure correlate with viremia containment following establishment of infection. These findings led to the hypothesis that active immunization with vaccines able to induce virus-specific T-cell responses following the establishment of infection could also ameliorate the virological outcome. Here, we will review the relative effect of ART and vaccination during primary SIVmac infection of macaques.
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Affiliation(s)
- Genoveffa Franchini
- National Cancer Institute, Basic Research Laboratory, 41/D804, Bethesda, MD 20892-5055, USA.
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56
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D'Offizi G, Montesano C, Agrati C, Gioia C, Amicosante M, Topino S, Narciso P, Pucillo LP, Ippolito G, Poccia F. Expansion of pre-terminally differentiated CD8 T cells in chronic HIV-positive patients presenting a rapid viral rebound during structured treatment interruption. AIDS 2002; 16:2431-8. [PMID: 12461417 DOI: 10.1097/00002030-200212060-00008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE The influence of structured treatment interruption on effector/memory CD8 T cell dynamics was analysed in chronic HIV-infected patients showing a rapid or delayed viral rebound. DESIGN Structured treatment interruption consisted of at least one month of discontinuation, followed by highly active antiretroviral therapy (HAART) resumption. Two groups of HIV structured treatment interruption patients were selected on the basis of plasma viral HIV-RNA value (> 30 000 copies/ml, branched DNA): group A (n = 14), patients with a rapid viral rebound (within one month) and group B (n = 6), patients with a delayed or no viral rebound (after a minimum of 4 months). METHODS A clinical and immunological follow-up was performed at HAART suspension (t 0), one month from suspension (t 1), at HAART resumption (t 2), and 30 days from resumption (t 3). RESULTS A sustained viral rebound was observed in group A patients, showing a rapid expansion of circulating CD8 T lymphocytes. In this group, the frequencies of CD8 T cells releasing IFN-gamma after mitogen-induced or Gag-specific stimulation were highly increased after HAART discontinuation. Nevertheless, these CD8 T lymphocytes were mainly composed of pre-terminally differentiated cytotoxic T lymphocytes (CTL) expressing a CCR7 CD27 CD45RA phenotype and a reduced amount of perforin. In contrast, group B patients showed no significant changes in immunological parameters during a prolonged drug-free period. CONCLUSION These data indicate that monitoring CD8 T cell dynamics during structured treatment interruption could be clinically relevant, and new therapeutic strategies should aim qualitatively to restore CTL effector functions.
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Affiliation(s)
- Gianpiero D'Offizi
- Laboratory of Immunopathology Padiglione Del Vecchio, National Institute for Infectious Diseases Lazzaro Spallanzani, IRCCS, Via Portuense 292, 00149 Rome, Italy
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57
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Mäkitalo B, Andersson M, Areström I, Karlén K, Villinger F, Ansari A, Paulie S, Thorstensson R, Ahlborg N. ELISpot and ELISA analysis of spontaneous, mitogen-induced and antigen-specific cytokine production in cynomolgus and rhesus macaques. J Immunol Methods 2002; 270:85-97. [PMID: 12379341 DOI: 10.1016/s0022-1759(02)00274-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Evaluation of cytokine production in macaques has been hampered by a lack of availability of optimized and standardized immunoassays such as ELISA and enzyme-linked immune spot assay (ELISpot); only a limited number of macaque cytokines have been assessed by ELISpot. Using monoclonal antibodies (mAb) to human cytokines that cross-react with cynomolgus and rhesus macaque interferon-gamma (IFN-gamma), interleukin (IL)-2, IL-4, IL-5, IL-6, IL-12, IL-13 and granulocyte monocyte colony-stimulating factor, we measured macaque cytokine production by ELISA and ELISpot. Quantitation of spontaneous as well as phytohemagglutinin (PHA)-induced cytokine production in peripheral blood mononuclear cells (PBMC) from rhesus and cynomolgus macaques and humans were compared. The proportional distribution of the different cytokines, in terms of PBMC synthesizing different cytokines as well as the levels of the different cytokines produced, were similar in all species. Spontaneous- and PHA-induced cytokine productions thus appear to be similarly regulated in macaques and man. ELISpot and ELISA assays for macaque IFN-gamma were further used to measure antigen-specific immune responses of PBMC from cynomolgus macaques exposed to, or vaccinated against, simian immunodeficiency virus (SIV). The establishment of reliable immunoassays for detection of macaque cytokines is of importance for future progress of research utilizing macaques as experimental animals.
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Affiliation(s)
- Barbro Mäkitalo
- Swedish Institute for Infectious Disease Control, SE-171 82 Solna, Sweden.
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58
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Oxenius A, Sewell AK, Dawson SJ, Günthard HF, Fischer M, Gillespie GM, Rowland-Jones SL, Fagard C, Hirschel B, Phillips RE, Price DA. Functional discrepancies in HIV-specific CD8+ T-lymphocyte populations are related to plasma virus load. J Clin Immunol 2002; 22:363-74. [PMID: 12462336 DOI: 10.1023/a:1020656300027] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The potent ability of current antiretroviral drug regimens to control human immunodeficiency Virus-1 (HIV-1) replication, in conjunction with the clinical practice of structured therapeutic interruptions, provides a system in which virus levels are manipulated during a persistent infection in humans. Here, we exploit this system to examine the impact of variable plasma virus load (pVL) on the functionality of HIV-specific CD8+ T-lymphocyte populations. Using both ELISpot methodology and intracellular cytokine staining for interferon (IFN)-gamma to assess functional status, together with fluorochrome-labeled peptide-major histocompatibility complex (pMHC) class I tetramer analysis to detect the physical presence of CD8+ T lymphocytes expressing cognate T-cell receptors (TCRs), we observed that the proportion of HIV-specific CD8+ T lymphocytes capable of mounting an effector response to antigen challenge directly ex vivo is related to the kinetics of virus exposure. Specifically, (a) after prolonged suppression of pVL with antiretroviral therapy (ART), physical and functional measures of HIV-specific CD8+ T-lymphocyte frequencies approximated; and (b) the percentage of functionally responsive cells in the HIV-specific CD8+ T lymphocyte populations declined substantially when therapy was discontinued and pVL recrudesced in the same patients. These results corroborate and extend observations in animal models that describe nonresponsive CD8+ T lymphocytes in the presence of high levels of antigen load and have implications for the interpretation of quantitative data generated by methods that rely on functional readouts.
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Affiliation(s)
- Annetie Oxenius
- Nuffield Department of Clinical Medicine, University of Oxford, John Radcliffe Hospital, England.
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59
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Tryniszewska E, Nacsa J, Lewis MG, Silvera P, Montefiori D, Venzon D, Hel Z, Parks RW, Moniuszko M, Tartaglia J, Smith KA, Franchini G. Vaccination of macaques with long-standing SIVmac251 infection lowers the viral set point after cessation of antiretroviral therapy. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 169:5347-57. [PMID: 12391256 DOI: 10.4049/jimmunol.169.9.5347] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
A cohort of rhesus macaques with long-standing SIVmac251 infection (> or =5 mo) was treated with continuous antiretroviral therapy (ART). A group of eight macaques was vaccinated with or without simultaneous administration of low dose IL-2 with the highly attenuated poxvirus vector (NYVAC) vaccine candidate expressing the SIVmac structural gag-pol-env (gpe) genes and a novel chimeric fusion protein derived from the rev-tat-nef (rtn) regulatory genes. Control groups consisted of mock-vaccinated macaques or animals treated only with IL-2. Vaccination significantly expanded both virus-specific CD4(+) and CD8(+) T cell responses, and IL-2 further increased the vaccine-induced response to an immunodominant Gag epitope. Following antiretroviral treatment interruption, the viral set point was significantly lower in vaccinated than in control macaques for at least 4 consecutive mo, and viral containment was inversely correlated with vaccine-induced, virus-specific CD4(+) and CD8(+) T cell responses. These data provide the proof of concept that therapeutic vaccination before cessation of ART may be a feasible approach in the clinical management of HIV-1 infection.
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60
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Hel Z, Nacsa J, Tryniszewska E, Tsai WP, Parks RW, Montefiori DC, Felber BK, Tartaglia J, Pavlakis GN, Franchini G. Containment of simian immunodeficiency virus infection in vaccinated macaques: correlation with the magnitude of virus-specific pre- and postchallenge CD4+ and CD8+ T cell responses. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 169:4778-87. [PMID: 12391187 DOI: 10.4049/jimmunol.169.9.4778] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Macaques infected with the SIV strain SIVmac251 develop a disease closely resembling human AIDS characterized by high viremia, progressive loss of CD4(+) T cells, occurrence of opportunistic infection, cachexia, and lymphomas. We report in this study that vaccination with the genetically attenuated poxvirus vector expressing the structural Ags of SIVmac (NYVAC-SIV-gag, pol, env) in combination with priming with DNA-SIV-gag, env resulted in significant suppression of viremia within 2 mo after mucosal exposure to the highly pathogenic SIVmac251 in the majority of vaccinated macaques. The control of viremia in these macaques was long lasting and inversely correlated to the level of both pre- and postchallenge Gag-specific lymphoproliferative responses, as well as to the level of total SIV-specific CD4(+) T lymphocyte responses at the peak of acute viremia as detected by intracellular cytokine-staining assay. Viremia containment also correlated with the frequency of the immunodominant Gag(181-189)CM9 epitope-specific CD8(+) T cells present before the challenge or expanded during acute infection. These data indicate, for the first time, the importance of vaccine-induced CD4(+) Th cell responses as an immune correlate of viremia containment. The results presented in this work also further demonstrate the potential of a DNA-prime/attenuated poxvirus-boost vaccine regimen in an animal model that well mirrors human AIDS.
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MESH Headings
- Acute Disease
- Administration, Intravaginal
- Animals
- Antibodies, Viral/analysis
- Antibodies, Viral/biosynthesis
- CD4-Positive T-Lymphocytes/immunology
- CD4-Positive T-Lymphocytes/virology
- CD8-Positive T-Lymphocytes/immunology
- CD8-Positive T-Lymphocytes/virology
- Chronic Disease
- Cytotoxicity, Immunologic
- Epitopes, T-Lymphocyte/genetics
- Epitopes, T-Lymphocyte/immunology
- Gene Products, env/administration & dosage
- Gene Products, env/genetics
- Gene Products, env/immunology
- Gene Products, gag/administration & dosage
- Gene Products, gag/genetics
- Gene Products, gag/immunology
- Gene Products, pol/administration & dosage
- Gene Products, pol/genetics
- Gene Products, pol/immunology
- Genetic Vectors/administration & dosage
- Genetic Vectors/immunology
- Immunity, Mucosal
- Immunization Schedule
- Immunization, Secondary
- Immunodominant Epitopes/genetics
- Immunodominant Epitopes/immunology
- Immunologic Memory
- Injections, Intradermal
- Injections, Intramuscular
- Lymphocyte Activation
- Macaca mulatta
- Neutralization Tests
- Poxviridae/immunology
- SAIDS Vaccines/administration & dosage
- SAIDS Vaccines/genetics
- SAIDS Vaccines/immunology
- Simian Acquired Immunodeficiency Syndrome/immunology
- Simian Acquired Immunodeficiency Syndrome/prevention & control
- Simian Acquired Immunodeficiency Syndrome/virology
- Simian Immunodeficiency Virus/immunology
- T-Lymphocytes, Cytotoxic/immunology
- T-Lymphocytes, Cytotoxic/virology
- Vaccines, DNA/administration & dosage
- Vaccines, DNA/immunology
- Viremia/immunology
- Viremia/prevention & control
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Affiliation(s)
- Zdenek Hel
- Basic Research Laboratory, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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61
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What's the Matter with HIV-directed Killer T Cells? J Theor Biol 2002. [DOI: 10.1006/jtbi.2002.3103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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62
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Vogel TU, Horton H, Fuller DH, Carter DK, Vielhuber K, O'Connor DH, Shipley T, Fuller J, Sutter G, Erfle V, Wilson N, Picker LJ, Watkins DI. Differences between T cell epitopes recognized after immunization and after infection. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 169:4511-21. [PMID: 12370388 DOI: 10.4049/jimmunol.169.8.4511] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Evidence suggests that cellular immune responses play a crucial role in the control of HIV and SIV replication in infected individuals. Several vaccine strategies have therefore targeted these CD8(+) and CD4(+) responses. Whether vaccination induces the same repertoire of responses seen after infection is, however, a key unanswered question in HIV vaccine development. We therefore compared the epitope specificity induced by vaccination to that present postchallenge in the peripheral blood. Intracellular cytokine staining of PBMC stimulated with overlapping 15/20-mer peptides spanning the proteins of SIV were measured after DNA/modified vaccinia Ankara vaccination of eight rhesus macaques. Lymphocytes from 8 animals recognized a total of 39 CD8 epitopes and 41 CD4 epitopes encoded by the vaccine. T cell responses were again monitored after challenge with SIVmac239 to investigate the evolution of these responses. Only 57% of all CD8(+) T cell responses and 19% of all CD4(+) T cell responses present after vaccination were recalled after infection as measured in the peripheral blood. Interestingly, 29 new CD8 epitopes and 5 new CD4 epitopes were recognized by PBMC in the acute phase. These new epitopes were not detected after vaccination, and only some of them were maintained in the chronic phase (33% of CD8 and no CD4 responses). Additionally, 24 new CD8 epitopes and 7 new CD4 epitopes were recognized by PBMC in the chronic phase of infection. The repertoire of the immune response detected in the peripheral blood after immunization substantially differed from the immune response detected in the peripheral blood after infection.
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MESH Headings
- Administration, Rectal
- Amino Acid Sequence
- Animals
- Base Sequence
- CD4-Positive T-Lymphocytes/immunology
- CD4-Positive T-Lymphocytes/metabolism
- CD4-Positive T-Lymphocytes/virology
- CD8-Positive T-Lymphocytes/immunology
- CD8-Positive T-Lymphocytes/metabolism
- CD8-Positive T-Lymphocytes/virology
- Cell Line, Transformed
- Epitopes, T-Lymphocyte/analysis
- Epitopes, T-Lymphocyte/genetics
- Epitopes, T-Lymphocyte/immunology
- Immunity, Cellular/genetics
- Immunization, Secondary
- Injections, Intradermal
- Leukocytes, Mononuclear/immunology
- Leukocytes, Mononuclear/virology
- Lymphoid Tissue/immunology
- Lymphoid Tissue/metabolism
- Lymphoid Tissue/virology
- Macaca mulatta
- Molecular Sequence Data
- Peptide Fragments/analysis
- Peptide Fragments/genetics
- Peptide Fragments/immunology
- Peptide Mapping
- SAIDS Vaccines/administration & dosage
- SAIDS Vaccines/genetics
- SAIDS Vaccines/immunology
- Simian Acquired Immunodeficiency Syndrome/immunology
- Simian Immunodeficiency Virus/immunology
- Vaccines, Synthetic/administration & dosage
- Vaccines, Synthetic/genetics
- Vaccines, Synthetic/immunology
- Vaccinia virus/genetics
- Vaccinia virus/immunology
- Viral Proteins/analysis
- Viral Proteins/genetics
- Viral Proteins/immunology
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Affiliation(s)
- Thorsten U Vogel
- Wisconsin National Primate Research Center, University of Wisconsin, 1220 Capital Court, Madison, WI 53715, USA
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63
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Wedemeyer H, He XS, Nascimbeni M, Davis AR, Greenberg HB, Hoofnagle JH, Liang TJ, Alter H, Rehermann B. Impaired effector function of hepatitis C virus-specific CD8+ T cells in chronic hepatitis C virus infection. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 169:3447-58. [PMID: 12218168 DOI: 10.4049/jimmunol.169.6.3447] [Citation(s) in RCA: 513] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The cellular immune response contributes to clearance of hepatitis C virus (HCV) and persists for decades after recovery from infection. The immunological basis for the inefficiency of the cellular immune response in chronically infected persons is not known. Here, we used four HLA-A2 tetramers, specific for two HCV core and two HCV NS3 epitopes, to investigate at the single-cell level effector function and phenotype of HCV-specific CD8+ T cells in 20 chronically infected and 12 long-term recovered patients. Overall, HCV-specific, tetramer+ T cells were more frequently found in PBMCs of chronically infected patients than in those of recovered patients. However, when compared with HCV-tetramer+ T cells of recovered patients, they displayed an impaired proliferative capacity. As a result of the impaired proliferative capacity, HCV-specific T cell lines derived from chronically infected patients displayed less peptide-specific cytotoxicity than those from recovered patients. In addition, proliferation and ex vivo IFN-gamma production of HCV-tetramer+ cells, but not influenza-virus-specific T cells, were defective in chronically infected patients and could not be restored by in vitro stimulation with peptide and IL-2. At least three distinct phenotypes of HCV-specific CD8+ T cells were identified and associated with certain functional characteristics. In addition, impairment of proliferative, cytokine, and cytotoxic effector functions of tetramer+ T cells in viremic patients was associated with weak ex vivo HCV-specific CD4+ T cell responses. Thus, the defective functions of HCV-specific CD8+ T cells might contribute to viral persistence in chronically infected patients, and knowledge on their reversibility may facilitate the development of immunotherapeutic vaccines.
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Affiliation(s)
- Heiner Wedemeyer
- Liver Diseases Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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64
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Abstract
Fifteen years after the first, definitive reports of HIV-1-specific, CD8+ T cells [147,148], there is ample evidence for the importance of these cells in control of HIV-1 infection. As much is known of their role in the natural history of HIV-1 infection and their cellular and molecular mechanisms of reactivity than of T-cell responses to any other human virus. Indeed, HIV-1-related research has led the scientific field in revealing many new, fundamental principles of cellular immunity in the last 15 years. From these data, there are multiple, posited mechanisms for loss of CD8+ T-cell control of HIV-1 infection. These include both intrinsic defects in T-cell function and loss of T-cell recognition of HIV-1 because of its extraordinary genetic diversity and disruption of antigen presentation. Efforts have begun on devising approaches to reverse these immune defects in infected individuals and develop vaccines that induce T-cell immunity for protection from infection. Combination antiretroviral drug regimens now provide exceptional, long-lasting control of HIV-1 infection, even though they do not restore anti-HIV-1 T-cell immunity fully in persons with chronic HIV-1 infection. Very encouraging results show that such treatment can maintain normal T-cell reactivity specific for this virus in some persons with early HIV-1 infection. Unfortunately, the antiviral treatment does not cure the host of this persistent, latent virus. This has led to new strategies for immunotherapeutic intervention to enhance the level and breadth of the T-cell repertoire specific for the host's residual virus in persons with chronic HIV-1 infection. Although the principles of immunotherapy stem from early in the last century, modern era approaches are integrating highly sophisticated, molecular and cell biology reagents and methods for control of HIV-1 infection. The most promising immunotherapies are autologous virus activated in vivo by STI or administered in autologous DC that have been engineered ex vivo. There are also compelling rationales supported by animal models and early clinical trials for use of cytokines and chemokines as recombinant proteins or DNA to augment anti-HIV-1 T-cell reactivity and trafficking of T cells and APC to tissue sites of infection. For prevention of HIV-1 infection, the discouragingly poor results of vaccine development in the late 1980s and early 1990s have led to very encouraging, recent studies in monkeys that show partially protective and possibly sterilizing immunity. Finally, clinical trials of new-generation DNA and live vector vaccines already have indications of improved induction of HIV-1-specific T-cell responses. Knowledge of HIV-1-specific T-cell immunity and its role in protection from HIV-1 infection and disease must continue to expand until the goal of complete control of HIV-1 infection is accomplished.
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Affiliation(s)
- Paolo Piazza
- Department of Infectious Diseases and Microbiology, University of Pittsburgh Graduate School of Public Health, 425 Parran Hall, Pittsburgh, PA 15261, USA.
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65
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Lieberman J, Manjunath N, Shankar P. Avoiding the kiss of death: how HIV and other chronic viruses survive. Curr Opin Immunol 2002; 14:478-86. [PMID: 12088683 DOI: 10.1016/s0952-7915(02)00366-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Virus-specific CD8 T cells during chronic infection often exceed in numbers virus-replicating infected cells. Why then do antiviral CD8 T cells not do a better job of controlling infection? Although viral strategies for immune evasion are well known, this review will focus on changes in the CD8 T cell that interfere with cytolytic function. Most antiviral CD8 T cells in chronic infection do not express perforin, a molecule that is required for cytolysis. IL-2 and other costimulatory signals can restore cytotoxicity that has been impaired, suggesting a role for CD4 T cell anergy. The chance to eradicate an infection by T cell mediated lysis is undermined after an infection becomes established, in part because the effector immune response is impaired in the setting of chronic antigen.
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Affiliation(s)
- Judy Lieberman
- Center for Blood Research and Department of Pediatrics, Harvard Medical School, 800 Huntington Avenue, Boston, MA 02115, USA.
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66
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Horton H, Vogel TU, Carter DK, Vielhuber K, Fuller DH, Shipley T, Fuller JT, Kunstman KJ, Sutter G, Montefiori DC, Erfle V, Desrosiers RC, Wilson N, Picker LJ, Wolinsky SM, Wang C, Allison DB, Watkins DI. Immunization of rhesus macaques with a DNA prime/modified vaccinia virus Ankara boost regimen induces broad simian immunodeficiency virus (SIV)-specific T-cell responses and reduces initial viral replication but does not prevent disease progression following challenge with pathogenic SIVmac239. J Virol 2002; 76:7187-202. [PMID: 12072518 PMCID: PMC136301 DOI: 10.1128/jvi.76.14.7187-7202.2002] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Producing a prophylactic vaccine for human immunodeficiency virus (HIV) has proven to be a challenge. Most biological isolates of HIV are difficult to neutralize, so that conventional subunit-based antibody-inducing vaccines are unlikely to be very effective. In the rhesus macaque model, some protection was afforded by DNA/recombinant viral vector vaccines. However, these studies used as the challenge virus SHIV-89.6P, which is neutralizable, making it difficult to determine whether the observed protection was due to cellular immunity, humoral immunity, or a combination of both. In this study, we used a DNA prime/modified vaccinia virus Ankara boost regimen to immunize rhesus macaques against nearly all simian immunodeficiency virus (SIV) proteins. These animals were challenged intrarectally with pathogenic molecularly cloned SIVmac239, which is resistant to neutralization. The immunization regimen resulted in the induction of virus-specific CD8(+) and CD4(+) responses in all vaccinees. Although anamnestic neutralizing antibody responses against laboratory-adapted SIVmac251 developed after the challenge, no neutralizing antibodies against SIVmac239 were detectable. Vaccinated animals had significantly reduced peak viremia compared with controls (P < 0.01). However, despite the induction of virus-specific cellular immune responses and reduced peak viral loads, most animals still suffered from gradual CD4 depletion and progressed to disease.
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Affiliation(s)
- Helen Horton
- Wisconsin Regional Primate Research Center, University of Wisconsin, Madison, Wisconsin 53715, USA
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67
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Affiliation(s)
- T M Allen
- Wisconsin Regional Primate Research Center, Madison, Wisconsin, USA.
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68
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Kostense S, Vandenberghe K, Joling J, Van Baarle D, Nanlohy N, Manting E, Miedema F. Persistent numbers of tetramer+ CD8(+) T cells, but loss of interferon-gamma+ HIV-specific T cells during progression to AIDS. Blood 2002; 99:2505-11. [PMID: 11895786 DOI: 10.1182/blood.v99.7.2505] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although CD8(+) T cells initially suppress human immunodeficiency virus (HIV) replication, cytotoxic T-cell precursor frequencies eventually decline and fail to prevent disease progression. In a longitudinal study including 16 individuals infected with HIV-1, we studied both the number and function of HIV-specific CD8(+) T cells by comparing HLA-peptide tetramer staining and peptide-induced interferon-gamma (IFN-gamma) production. Numbers of IFN-gamma-producing T cells declined during progression to acquired immunodeficiency syndrome (AIDS), whereas the number of tetramer+ T cells in many individuals persisted at high frequencies. Loss of IFN-gamma-producing T cells correlated with declining CD4(+) T-cell counts, consistent with the need of CD4(+) T-cell help in maintaining adequate CD8(+) T-cell function. These data indicate that the loss of HIV-specific CD8(+) T-cell activity is not due to physical depletion, but is mainly due to progressively impaired function of HIV-specific CD8(+) T cells.
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Affiliation(s)
- Stefan Kostense
- Department of Clinical Viro-Immunology, CLB/Sanquin Blood Supply Foundation, University of Amsterdam, Plesmanlaan 125, 1066 CX Amsterdam, The Netherlands
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69
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Ansari AA, Mayne AE, Sundstrom JB, Bostik P, Grimm B, Altman JD, Villinger F. Administration of recombinant rhesus interleukin-12 during acute simian immunodeficiency virus (SIV) infection leads to decreased viral loads associated with prolonged survival in SIVmac251-infected rhesus macaques. J Virol 2002; 76:1731-43. [PMID: 11799168 PMCID: PMC135900 DOI: 10.1128/jvi.76.4.1731-1743.2002] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ability of recombinant rhesus interleukin-12 (rMamu-IL-12) administration during acute simian immunodeficiency virus SIVmac251 infection to influence the quality of the antiviral immune responses was assessed in rhesus macaques. Group I (n = 4) was the virus-only control group. Group II and III received a conditioning regimen of rMamu-IL-12 (10 and 20 microg/kg, respectively, subcutaneously [s.c.]) on days -2 and 0. Thereafter, group II received 2 microg of IL-12 per kg and group III received 10 microg/kg s.c. twice a week for 8 weeks. On day 0 all animals were infected with SIVmac251 intravenously. While all four group I animals and three of four group II animals died by 8 and 10 months post infection (p.i.), all four group III animals remained alive for >20 months p.i. The higher IL-12 dose led to lower plasma viral loads and markedly lower peripheral blood mononuclear cell and lymph node proviral DNA loads. During the acute viremia phase, the high-IL-12-dose monkeys showed an increase in CD3(-) CD8 alpha/alpha(+) and CD3(+) CD8 alpha/alpha(+) cells and, unlike the control and low-IL-12-dose animals, did not demonstrate an increase in CD4(+) CD45RA(+) CD62L(+) naive cells. The high-IL-12-dose animals also demonstrated that both CD8 alpha/alpha(+) and CD8 alpha/beta(+) cells produced antiviral factors early p.i., whereas only CD8 alpha/beta(+) cells retained this function late p.i. Long-term survival correlated with sustained high levels of SIV gag/pol and SIV env cytotoxic T lymphocytes and retention of high memory responses against nominal antigens. This is the first study to demonstrate the capacity of IL-12 to significantly protect macaques from SIV-induced disease, and it provides a useful model to more precisely identify correlates of virus-specific disease-protective responses.
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Affiliation(s)
- A A Ansari
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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70
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McKay PF, Schmitz JE, Barouch DH, Kuroda MJ, Lifton MA, Nickerson CE, Gorgone DA, Letvin NL. Vaccine protection against functional CTL abnormalities in simian human immunodeficiency virus-infected rhesus monkeys. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 168:332-7. [PMID: 11751978 DOI: 10.4049/jimmunol.168.1.332] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Accumulating evidence suggests that HIV-specific CD8(+) CTL are dysfunctional in HIV-infected individuals with progressive clinical disease. In the present studies, cytokine production by virus-specific CTL was assessed in the rhesus monkey model for AIDS to determine its contribution to the functional impairment of CTL. CTL from monkeys infected with nonpathogenic isolates of simian and simian-human immunodeficiency virus expressed high levels of IFN-gamma, TNF-alpha, and IL-2 after in vitro exposure to a nonspecific mitogen or the optimal peptide representing a dominant virus-specific CTL epitope. However, similarly performed studies assessing these capabilities in CTL from monkeys infected with pathogenic immunodeficiency virus isolates demonstrated a significant dysfunction in the ability of the CTL to produce IL-2 and TNF-alpha. Importantly, CTL from vaccinated monkeys that effectively controlled the replication of a highly pathogenic simian-human immunodeficiency virus isolate following challenge demonstrated a preserved capacity to produce these cytokines. These experiments suggest that defects in cytokine production may contribute to CTL dysfunction in chronic HIV or SIV infection. Moreover, an AIDS vaccine that confers protection against clinical disease evolution in this experimental model also preserves the functional capacity of these CTL to produce both IL-2 and TNF-alpha.
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Affiliation(s)
- Paul F McKay
- Division of Viral Pathogenesis, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, USA
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71
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Hel Z, Nacsa J, Kelsall B, Tsai WP, Letvin N, Parks RW, Tryniszewska E, Picker L, Lewis MG, Edghill-Smith Y, Moniuszko M, Pal R, Stevceva L, Altman JD, Allen TM, Watkins D, Torres JV, Berzofsky JA, Belyakov IM, Strober W, Franchini G. Impairment of Gag-specific CD8(+) T-cell function in mucosal and systemic compartments of simian immunodeficiency virus mac251- and simian-human immunodeficiency virus KU2-infected macaques. J Virol 2001; 75:11483-95. [PMID: 11689630 PMCID: PMC114735 DOI: 10.1128/jvi.75.23.11483-11495.2001] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2000] [Accepted: 08/08/2001] [Indexed: 11/20/2022] Open
Abstract
The identification of several simian immunodeficiency virus mac251 (SIV(mac251)) cytotoxic T-lymphocyte epitopes recognized by CD8(+) T cells of infected rhesus macaques carrying the Mamu-A*01 molecule and the use of peptide-major histocompatibility complex tetrameric complexes enable the study of the frequency, breadth, functionality, and distribution of virus-specific CD8(+) T cells in the body. To begin to address these issues, we have performed a pilot study to measure the virus-specific CD8(+) and CD4(+) T-cell response in the blood, lymph nodes, spleen, and gastrointestinal lymphoid tissues of eight Mamu-A*01-positive macaques, six of those infected with SIV(mac251) and two infected with the pathogenic simian-human immunodeficiency virus KU2. We focused on the analysis of the response to peptide p11C, C-M (Gag 181), since it was predominant in most tissues of all macaques. Five macaques restricted viral replication effectively, whereas the remaining three failed to control viremia and experienced a progressive loss of CD4(+) T cells. The frequency of the Gag 181 (p11C, C-->M) immunodominant response varied among different tissues of the same animal and in the same tissues from different animals. We found that the functionality of this virus-specific CD8(+) T-cell population could not be assumed based on the ability to specifically bind to the Gag 181 tetramer, particularly in the mucosal tissues of some of the macaques infected by SIV(mac251) that were progressing to disease. Overall, the functionality of CD8(+) tetramer-binding T cells in tissues assessed by either measurement of cytolytic activity or the ability of these cells to produce gamma interferon or tumor necrosis factor alpha was low and was even lower in the mucosal tissue than in blood or spleen of some SIV(mac251)-infected animals that failed to control viremia. The data obtained in this pilot study lead to the hypothesis that disease progression may be associated with loss of virus-specific CD8(+) T-cell function.
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Affiliation(s)
- Z Hel
- Basic Research Laboratory, Bethesda, Maryland 20892, USA
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72
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Eo SK, Kumaraguru U, Rouse BT. Plasmid DNA encoding CCR7 ligands compensate for dysfunctional CD8+ T cell responses by effects on dendritic cells. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2001; 167:3592-9. [PMID: 11564771 DOI: 10.4049/jimmunol.167.7.3592] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Lymphotoxin alpha-deficient (LTalpha-/-) mice, which lack lymph nodes and possess a disorganized spleen, develop dysfunctional CD8+ T cells upon HSV infection and readily succumb to herpes encephalitis. Such mice do develop apparently normal peptide-specific CD8+ T cell responses, as measured by MHC class I tetramer staining, but the majority of cells fail to become cytotoxic or express peptide-induced IFN-gamma production. In the present study, we demonstrate that functional defects of CD8+ T cells in LTalpha-/- mice can be largely rectified by the administration of plasmid DNA encoding CCR7 ligands before HSV infection. Treated mutant mice developed increased peptide-specific cytotoxic responses, enhanced numbers of CD8+ T cells capable of producing IFN-gamma, as well as improved resistance to HSV challenge. The corrective effect of chemokine treatment appeared to result from improved dendritic cell-mediated Ag presentation. Thus, a major consequence of the treatment was an increase in splenic dendritic cell number in CCR7 ligand-treated LTalpha-/- mice with such splenocyte populations showing improved APC activity in vitro. Our results document that functional defects of CD8+ T cells can be corrected, and indicate the value of plasmid vector encoding appropriate chemokines to achieve such immunotherapy.
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MESH Headings
- Animals
- Cells, Cultured
- Chemokine CCL19
- Chemokine CCL21
- Chemokines, CC/genetics
- Cytotoxicity Tests, Immunologic
- Dendritic Cells/immunology
- Encephalitis, Herpes Simplex/immunology
- Encephalitis, Herpes Simplex/pathology
- Encephalitis, Herpes Simplex/therapy
- Female
- Genetic Therapy
- Genetic Vectors
- Interferon-gamma/biosynthesis
- Lymphocyte Activation
- Lymphotoxin-alpha/genetics
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Plasmids
- Receptors, CCR7
- Receptors, Chemokine/agonists
- Spleen/immunology
- Spleen/pathology
- T-Lymphocytes, Cytotoxic/immunology
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Affiliation(s)
- S K Eo
- Laboratory of Viral Immunology, Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA
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73
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Lucas M, Karrer U, Lucas A, Klenerman P. Viral escape mechanisms--escapology taught by viruses. Int J Exp Pathol 2001; 82:269-86. [PMID: 11703537 PMCID: PMC2517780 DOI: 10.1046/j.1365-2613.2001.00204.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2001] [Accepted: 07/24/2001] [Indexed: 01/12/2023] Open
Abstract
Viruses have 'studied' immunology over millions of years of coevolution with their hosts. During this ongoing education they have developed countless mechanisms to escape from the host's immune system. To illustrate the most common strategies of viral immune escape we have focused on two murine models of persistent infection, lymphocytic choriomeningitis virus (LCMV) and murine cytomegalovirus (MCMV). LCMV is a fast replicating small RNA virus with a genome prone to mutations. Therefore, LCMV escapes from the immune system mainly by two strategies: 'speed' and 'shape change'. At the opposite extreme, MCMV is a large, complex DNA virus with a more rigid genome and thus the strategies used by LCMV are no option. However, MCMV has the coding capacity for additional genes which interfere specifically with the immune response of the host. These escape strategies have been described as 'camouflage' and 'sabotage'. Using these simple concepts we describe the spectrum of viral escapology, giving credit not only to the researchers who uncovered this fascinating area of immunology but also to the viruses themselves, who still have a few lessons to teach.
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Affiliation(s)
- M Lucas
- Nuffield Department of Medicine, John Radcliffe Hospital, Oxford, UK.
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74
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Lieberman J, Shankar P, Manjunath N, Andersson J. Dressed to kill? A review of why antiviral CD8 T lymphocytes fail to prevent progressive immunodeficiency in HIV-1 infection. Blood 2001; 98:1667-77. [PMID: 11535496 DOI: 10.1182/blood.v98.6.1667] [Citation(s) in RCA: 178] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
CD8 T cells play an important role in protection and control of HIV-1 by direct cytolysis of infected cells and by suppression of viral replication by secreted factors. However, although HIV-1-infected individuals have a high frequency of HIV-1-specific CD8 T cells, viral reservoirs persist and progressive immunodeficiency generally ensues in the absence of continuous potent antiviral drugs. Freshly isolated HIV-specific CD8 T cells are often unable to lyse HIV-1-infected cells. Maturation into competent cytotoxic T lymphocytes may be blocked during the initial encounter with antigen because of defects in antigen presentation by interdigitating dendritic cells or HIV-infected macrophages. The molecular basis for impaired function is multifactorial, due to incomplete T-cell signaling and activation (in part related to CD3zeta and CD28 down-modulation), reduced perforin expression, and inefficient trafficking of HIV-specific CD8 T cells to lymphoid sites of infection. CD8 T-cell dysfunction can partially be corrected in vitro with short-term exposure to interleukin 2, suggesting that impaired HIV-specific CD4 T helper function may play a significant causal or exacerbating role. Functional defects are qualitatively different and more severe with advanced disease, when interferon gamma production also becomes compromised.
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Affiliation(s)
- J Lieberman
- Center for Blood Research, Harvard Medical School, Boston, MA 02115, USA.
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