[Show abstract][Hide abstract] ABSTRACT: Competition for iron influences host-pathogen interactions. Pathogens secrete small iron-binding moieties, siderophores, to acquire host iron. In response, the host secretes siderophore-binding proteins, such as lipocalin 24p3, which limit siderophore-mediated iron import into bacteria. Mammals produce 2,5-dihydroxy benzoic acid, a compound that resembles a bacterial siderophore. Our data suggest that bacteria use both mammalian and bacterial siderophores. In support of this idea, supplementation with mammalian siderophore enhances bacterial growth in vitro. In addition, mice lacking the mammalian siderophore resist E. coli infection. Finally, we show that the host responds to infection by suppressing siderophore synthesis while up-regulating lipocalin 24p3 expression via TLR signaling. Thus, reciprocal regulation of 24p3 and mammalian siderophore is a protective mechanism limiting microbial access to iron.
Journal of Experimental Medicine 05/2014; 211(6). DOI:10.1084/jem.20132629 · 13.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have previously demonstrated that mycobacterial lipoproteins engage TLR2 on human CD4(+) T cells and upregulate TCR triggered-IFN-γ secretion and cell proliferation in vitro. Here we examined the role of CD4(+) T cell-expressed TLR2 in Mycobacterium tuberculosis (MTB) Ag-specific T-cell priming and in protection against MTB infection in vivo. Like their human counterparts, mouse CD4(+) T cells express TLR2 and respond to TLR2 co-stimulation in vitro. This Th1-like response was observed in the context of both polyclonal and Ag-specific TCR stimulation. To evaluate the role of T-cell TLR2 in priming of CD4(+) T cells in vivo, naïve MTB Ag85B-specific TCR transgenic CD4(+) T cells (P25 TCR-Tg) were adoptively transferred into Tlr2(-/-) recipient C57Bl/6 mice that were then immunized with Ag85B and with or without TLR2 ligand Pam3 Cys-SKKKK. TLR2 engagement during priming resulted in increased numbers of IFN-γ-secreting P25 TCR-Tg T cells one week after immunization. P25 TCR-Tg T cells stimulated in vitro via TCR and TLR2 conferred more protection than T cells stimulated via TCR alone when adoptively transferred before MTB infection. Our findings indicate that TLR2 engagement on CD4(+) T cells increases MTB Ag-specific responses and may contribute to protection against MTB infection. This article is protected by copyright. All rights reserved.
European Journal of Immunology 05/2014; 44(5). DOI:10.1002/eji.201344100 · 4.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Tuberculosis (TB) is the leading cause of mortality among those infected with human immunodeficiency virus (HIV-1) worldwide. HIV-1 load and heterogeneity are increased both locally and systemically in active TB. Mycobacterium tuberculosis (MTB) infection supports HIV-1 replication through dysregulation of host cytokines, chemokines, and their receptors. However the possibility that mycobacterial molecules released from MTB infected macrophages directly interact with CD4(+) T cells triggering HIV-1 replication has not been fully explored. We studied the direct effect of different MTB molecules on HIV-1 replication (R5-tropic strain Bal) in anti-CD3- stimulated CD4(+) T cells from healthy donors in an antigen presenting cell (APC)-free system. PIM6, a major glycolipid of the mycobacterial cell wall, induced significant increases in the percent of HIV-1 infected T cells and the viral production in culture supernatants. In spite of structural relatedness, none of the other three major MTB cell wall glycolipids had significant impact on HIV-1 replication in T cells. Increased levels of IFN-γ in culture supernatants from cells treated with PIM6 indicate that HIV-1 replication is likely dependent on enhanced T cell activation. In HEK293 cells transfected with TLR2, PIM6 was the strongest TLR2 agonist among the cell wall associated glycolipids tested. PIM6 increased the percentage of HIV infected cells and viral particles in the supernatant in a T-cell-based reporter cell line (JLTRg-R5) transfected with TLR1 and TLR2 but not in the cells transfected with the empty vector (which lack TLR2 expression) confirming that PIM6-induced HIV-1 replication depends at least partially on TLR2 signaling.
PLoS ONE 11/2013; 8(11):e80938. DOI:10.1371/journal.pone.0080938 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Intracellular pathogens, such as Mycobacterium tuberculosis, reside in the phagosomes of macrophages where antigenic processing is initiated. Mycobacterial antigen–MHC class II complexes are formed within the phagosome and are then trafficked to the cell surface. Interferon-γ (IFN-γ) and interleukin-10 (IL-10) influence the outcome of M. tuberculosis infection; however, the role of these cytokines with regard to the formation of M. tuberculosis peptide–MHC-II complexes remains unknown. We analysed the kinetics and subcellular localization of M. tuberculosis peptide–MHC-II complexes in M. tuberculosis-infected human monocyte-derived macrophages (MDMs) using autologous M. tuberculosis-specific CD4+ T cells. The MDMs were pre-treated with either IFN-γ or IL-10 and infected with M. tuberculosis. Cells were mechanically homogenized, separated on Percoll density gradients and manually fractionated. The fractions were incubated with autologous M. tuberculosis -specific CD4+ T cells. Our results demonstrated that in MDMs pre-treated with IFN-γ, M. tuberculosis peptide–MHC-II complexes were detected early mainly in the phagosomal fractions, whereas in the absence of IFN-γ, the complexes were detected in the endosomal fractions. In MDMs pre-treated with IL-10, the M. tuberculosis peptide–MHC-II complexes were retained in the endosomal fractions, and these complexes were not detected in the plasma membrane fractions. The results of immunofluorescence microscopy demonstrated the presence of Ag85B associated with HLA-DR at the cell surface only in the IFN-γ-treated MDMs, suggesting that IFN-γ may accelerate M. tuberculosis antigen processing and presentation at the cell membrane, whereas IL-10 favours the trafficking of Ag85B to vesicles that do not contain LAMP-1. Therefore, IFN-γ and IL-10 play a role in the formation and trafficking of M. tuberculosis peptide–MHC-II complexes.
[Show abstract][Hide abstract] ABSTRACT: Immune evasion is required for Mycobacterium tuberculosis to survive in the face of robust CD4(+) T cell responses. We have shown previously that M. tuberculosis cell wall glycolipids, including mannose capped lipoarabinomannan (ManLAM), directly inhibit polyclonal murine CD4(+) T cell activation by blocking ZAP-70 phosphorylation. We extended these studies to antigen-specific murine CD4(+) T cells and primary human T cells and found that ManLAM inhibited them as well. Lck and LAT phosphorylation also were inhibited by ManLAM without affecting their localization to lipid rafts. Inhibition of proximal TCR signaling was temperature sensitive, suggesting that ManLAM insertion into T cell membranes was required. Thus, M. tuberculosis ManLAM inhibits antigen-specific CD4(+) T cell activation by interfering with very early events in TCR signaling through ManLAM's insertion in T cell membranes.
[Show abstract][Hide abstract] ABSTRACT: Mtb regulates many aspects of the host immune response, including CD4+ T lymphocyte responses that are essential for protective immunity to Mtb, and Mtb effects on the immune system are paradoxical, having the capacity to inhibit (immune evasion) and to activate (adjuvant effect) immune cells. Mtb regulates CD4+ T cells indirectly (e.g., by manipulation of APC function) and directly, via integrins and TLRs expressed on T cells. We now report that previously uncharacterized Mtb protein Rv2468c/MT2543 can directly regulate human CD4+ T cell activation by delivering costimulatory signals. When combined with TCR stimulation (e.g., anti-CD3), Rv2468c functioned as a direct costimulator for CD4+ T cells, inducing IFN-γ secretion and T cell proliferation. Studies with blocking antibodies and soluble RGD motifs demonstrated that Rv2468c engaged integrin VLA-5 (α5β1) on CD4+ T cells through its FN-like RGD motif. Costimulation by Rv2468c induced phosphorylation of FAKs and Pyk2. These results reveal that by expressing molecules that mimic host protein motifs, Mtb can directly engage receptors on CD4+ T cells and regulate their function. Rv2468c-induced costimulation of CD4+ T cells could have implications for TB immune pathogenesis and Mtb adjuvant effect.
[Show abstract][Hide abstract] ABSTRACT: The success of Mycobacterium tuberculosis as a pathogen relies on its ability to regulate the host immune response. M. tuberculosis can manipulate adaptive T cell responses indirectly by modulating antigen-presenting cell (APC) function or by directly interacting with T cells. Little is known about the role of M. tuberculosis molecules in direct regulation of T cell function. Using a biochemical approach, we identified lipoproteins LprG and LpqH as major molecules in M. tuberculosis lysate responsible for costimulation of primary human CD4(+) T cells. In the absence of APCs, activation of memory CD4(+) T cells with LprG or LpqH in combination with anti-CD3 antibody induces Th1 cytokine secretion and cellular proliferation. Lipoprotein-induced T cell costimulation was inhibited by blocking antibodies to Toll-like receptor 2 (TLR2) and TLR1, indicating that human CD4(+) T cells can use TLR2/TLR1 heterodimers to directly respond to M. tuberculosis products. M. tuberculosis lipoproteins induced NF-κB activation in CD4(+) T cells in the absence of TCR co-engagement. Thus, TLR2/TLR1 engagement alone by M. tuberculosis lipoprotein triggered intracellular signaling, but upregulation of cytokine production and proliferation required co-engagement of the TCR. In conclusion, our results demonstrate that M. tuberculosis lipoproteins LprG and LpqH participate in the regulation of adaptive immunity not only by inducing cytokine secretion and costimulatory molecules in innate immune cells but also through directly regulating the activation of memory T lymphocytes.
Infection and immunity 11/2010; 79(2):663-73. DOI:10.1128/IAI.00806-10 · 4.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Knockout of lprG results in decreased virulence of Mycobacterium tuberculosis (MTB) in mice. MTB lipoprotein LprG has TLR2 agonist activity, which is thought to be dependent on its N-terminal triacylation. Unexpectedly, here we find that nonacylated LprG retains TLR2 activity. Moreover, we show LprG association with triacylated glycolipid TLR2 agonists lipoarabinomannan, lipomannan and phosphatidylinositol mannosides (which share core structures). Binding of triacylated species was specific to LprG (not LprA) and increased LprG TLR2 agonist activity; conversely, association of glycolipids with LprG enhanced their recognition by TLR2. The crystal structure of LprG in complex with phosphatidylinositol mannoside revealed a hydrophobic pocket that accommodates the three alkyl chains of the ligand. In conclusion, we demonstrate a glycolipid binding function of LprG that enhances recognition of triacylated MTB glycolipids by TLR2 and may affect glycolipid assembly or transport for bacterial cell wall biogenesis.
[Show abstract][Hide abstract] ABSTRACT: Immune evasion is required for Mycobacterium tuberculosis to survive in the face of robust adaptive CD4(+) T-cell responses. We have previously shown that M. tuberculosis can indirectly inhibit CD4(+) T cells by suppressing the major histocompatibility complex class II antigen-presenting cell function of macrophages. This study was undertaken to determine if M. tuberculosis could directly inhibit CD4(+) T-cell activation. Murine CD4(+) T cells were purified from spleens by negative immunoaffinity selection followed by flow sorting. Purified CD4(+) T cells were activated for 16 to 48 h with CD3 and CD28 monoclonal antibodies in the presence or absence of M. tuberculosis and its subcellular fractions. CD4(+) T-cell activation was measured by interleukin 2 production, proliferation, and expression of activation markers, all of which were decreased in the presence of M. tuberculosis. Fractionation identified that M. tuberculosis cell wall glycolipids, specifically, phosphatidylinositol mannoside and mannose-capped lipoarabinomannan, were potent inhibitors. Glycolipid-mediated inhibition was not dependent on Toll-like receptor signaling and could be bypassed through stimulation with phorbol 12-myristate 13-acetate and ionomycin. ZAP-70 phosphorylation was decreased in the presence of M. tuberculosis glycolipids, indicating that M. tuberculosis glycolipids directly inhibited CD4(+) T-cell activation by interfering with proximal T-cell-receptor signaling.
Infection and immunity 09/2009; 77(10):4574-83. DOI:10.1128/IAI.00222-09 · 4.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Direct regulation of T cell function by microbial ligands through Toll-like receptors (TLR) is an emerging area of T cell biology. Currently either immunomagnetic cell sorting (IMACS) or fluorescence-activated cell sorting (FACS), are utilized to isolate T-cell subsets for such studies. However, it is unknown to what extent differences in T cell purity between these isolation techniques influence T cell functional assays. We compared the purity, response to mitogen, activation requirements, and response to TLR ligands between human CD4(+) T cells isolated either by IMACS (IMACS-CD4(+)) or by IMACS followed by FACS (IMACS/FACS-CD4(+)). As expected, IMACS-CD4(+) were less pure than IMACS/FACS-CD4(+) (92.5%+/-1.4% versus 99.7%+/-0.2%, respectively). Consequently, IMACS-CD4(+) proliferated and produced cytokines in response to mitogen alone and had lower activation requirements compared to IMACS/FACS-CD4(+). In addition IMACS-CD4(+) but not IMACS/FACS-CD4(+) responses were upregulated by the TLR-4 ligand lipopolysaccharide (LPS). On the other hand, TLR-2 and TLR-5 engagement induced costimulation in both IMACS-CD4(+) and highly purified IMACS-/FACS-CD4(+). Altogether these results indicate that small differences in cell purity can significantly alter T cell responses to TLR ligands. This study stresses the importance of a stringent purification method when investigating the role of microbial ligands in T cell function.
[Show abstract][Hide abstract] ABSTRACT: Vdelta2+ T cells, the major circulating T-cell receptor-gammadelta-positive (TCR-gammadelta+) T-cell subset in healthy adults, are involved in immunity against many microbial pathogens including Mycobacterium tuberculosis. Vdelta2+ T cells recognize small phosphorylated metabolites (phosphoantigens), expand in response to whole M. tuberculosis bacilli, and complement the protective functions of CD4+ T cells. CD4+ CD25(high) Foxp3+ T cells (Tregs) comprise 5-10% of circulating T cells and are increased in patients with active tuberculosis (TB). We investigated whether, in addition to their known role in suppressing TCR-alphabeta+ lymphocytes, Tregs suppress Vdelta2+ T-cell function. We found that depletion of Tregs from peripheral blood mononuclear cells increased Vdelta2+ T-cell expansion in response to M. tuberculosis (H37Ra) in tuberculin-skin-test-positive donors. We developed a suppression assay with fluorescence-activated cell sorting-purified Tregs and Vdelta2+ T cells by coincubating the two cell types at a 1 : 1 ratio. The Tregs partially suppressed interferon-gamma secretion by Vdelta2+ T cells in response to anti-CD3 monoclonal antibody plus interleukin-2 (IL-2). In addition, Tregs downregulated the Vdelta2+ T-cell interferon-gamma responses induced by phosphoantigen (BrHPP) and IL-2. Under the latter conditions there was no TCR stimulus for Tregs and therefore IL-2 probably triggered suppressor activity. Addition of purified protein derivative (PPD) increased the suppression of Vdelta2+ T cells, suggesting that PPD activated antigen-specific Tregs. Our study provides evidence that Tregs suppress both anti-CD3 and antigen-driven Vdelta2+ T-cell activation. Antigen-specific Tregs may therefore contribute to the Vdelta2+ T-cell functional deficiencies observed in TB.
[Show abstract][Hide abstract] ABSTRACT: The pathological hallmark of the host response to Mycobacterium tuberculosis is the granuloma where T cells and macrophages interact with the extracellular matrix (ECM) to control the infection. Recruitment and retention of T cells within inflamed tissues depend on adhesion to the ECM. T cells use integrins to adhere to the ECM, and fibronectin (FN) is one of its major components. We have found that the major M. tuberculosis cell wall glycolipid, phosphatidylinositol mannoside (PIM), induces homotypic adhesion of human CD4+ T cells and T cell adhesion to immobilized FN. Treatment with EDTA and cytochalasin D prevented PIM-induced T cell adhesion. PIM-induced T cell adhesion to FN was blocked with mAbs against alpha5 integrin chain and with RGD-containing peptides. Alpha5beta1 (VLA-5) is one of two major FN receptors on T cells. PIM was found to bind directly to purified human VLA-5. Thus, PIM interacts directly with VLA-5 on CD4+ T lymphocytes, inducing activation of the integrin, and promoting adhesion to the ECM glycoprotein, FN. This is the first report of direct binding of a M. tuberculosis molecule to a receptor on human T cells resulting in a change in CD4+ T cell function.
The Journal of Immunology 10/2006; 177(5):2959-68. DOI:10.4049/jimmunol.177.5.2959 · 5.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Active tuberculosis (TB) is associated with prolonged suppression of Mycobacterium tuberculosis (MTB)-specific immune responses, but mechanisms involved are understood incompletely. We investigated a potential role for CD4+CD25+ regulatory T cells in depressed anti-MTB immunity by evaluating serially CD4 cell phenotype and interferon (IFN)-gamma production by mononuclear cells from patients with TB. At diagnosis, frequencies of CD4+CD25+ T cells were increased in blood from TB patients compared to healthy purified protein derivative (PPD)-positive controls (with a history of prior TB exposure), and remained elevated at completion of therapy (6 months). By contrast, expression of another activation marker, CD69, by CD4 T cells was increased at diagnosis, but declined rapidly to control levels with treatment. Among CD4+CD25+ T cells from TB patients at diagnosis those expressing high levels of CD25, probably representing regulatory T cells, were increased 2.9-fold when compared to control subjects, while MTB-stimulated IFN-gamma levels in whole blood supernatants were depressed. A role for CD4+CD25+ T cells in depressed IFN-gamma production during TB was substantiated in depletion experiments, where CD25+-depleted CD4 T cells produced increased amounts of IFN-gamma upon MTB stimulation compared to unseparated T cells. At follow-up, IFN-gamma production improved most significantly in blood from TB patients with high baseline frequencies of CD4+CD25+ T cells (more than threefold higher than controls for both total and CD25hi+ CD4 T cells), who also had a significant drop in frequencies of both total and 'regulatory' CD4+CD25+ T cells in response to treatment. Expansion of CD4+CD25+ regulatory T cells during active TB may play a role in depressed T cell IFN-gamma production.
[Show abstract][Hide abstract] ABSTRACT: Mycobacterium tuberculosis resides in phagosomes inside macrophages. In this study, we analyzed the kinetics and location of M. tuberculosis peptide-major histocompatibility complex class II (MHC-II) complexes in M. tuberculosis-infected human macrophages. M. tuberculosis peptide-MHC-II complexes were detected with polyclonal autologous M. tuberculosis-specific CD4+ T cells or F9A6 T hybridoma cells specific for M. tuberculosis antigen (Ag) 85B (96-111). Macrophages processed heat-killed M. tuberculosis more rapidly and efficiently than live M. tuberculosis. To determine where M. tuberculosis peptide-MHC-II complexes were formed intracellularly, macrophages incubated with heat-killed M. tuberculosis were homogenized, and subcellular compartments were separated on Percoll density gradients analyzed with T cells. In THP-1 cells, M. tuberculosis Ag 85B (96- 111)-DR1 complexes appeared initially in phagosomes, followed by MHC class II compartment (MIIC) and the plasma membrane fractions. In monocyte-derived macrophages, M. tuberculosis peptide-MHC-II complexes appeared only in MIIC fractions and subsequently on the plasma membrane. Although phagosomes from both cell types acquired lysosome-associated membrane protein 1 (LAMP-1) and MHC-II, THP-1 phagosomes that support formation of M. tuberculosis peptide-MHC-II complexes had increased levels of both LAMP-1 and MHC-II. Thus, M. tuberculosis phagosomes with high levels of MHC-II and LAMP-1 and MIIC both have the potential to form peptide-MHC-II complexes from M. tuberculosis antigens in human macrophages.
Infection and Immunity 04/2006; 74(3):1621-30. DOI:10.1128/IAI.74.3.1621-1630.2006 · 4.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Vgamma9(+)Vdelta2(+) gammadelta T cells (Vdelta 2(+) T cells) are activated by Mycobacterium tuberculosis and secrete interferon (IFN)-gamma. Vdelta 2(+) T cells recognize phosphoantigens, such as bromohydrin pyrophosphate (BrHPP), and link innate and adaptive immunity.
A whole-blood assay was developed that used IFN-gamma secretion in response to BrHPP as a measurement of Vdelta2(+) T cell function.
Peak IFN-gamma levels were detected after stimulating whole blood with BrHPP for 7-9 days. IFN- gamma production in whole blood in response to BrHPP paralleled IFN-gamma production and Vdelta2(+) T cell expansion of peripheral-blood mononuclear cells. The assay was used to evaluate Vdelta2(+) T cell function in subjects in the United States (n = 24) and Uganda (n = 178) who were or were not infected with M. tuberculosis and/or human immunodeficiency virus (HIV) type 1. When 50 micromol/L BrHPP was used, 100% of healthy subjects produced IFN-gamma. The Vdelta2(+) T cell response was independent of the tuberculin skin test response. In Uganda, Vdelta2(+) T cell responses were decreased in patients with tuberculosis (n = 73) compared with responses in household contacts (n = 105). HIV-1-positive household contacts had lower responses than did HIV-1-negative household contacts. HIV-1-positive patients with tuberculosis had the lowest V delta 2(+) T cell responses.
Tuberculosis and HIV-1 infection are associated with decreased Velta2(+) T cell function. Decreased Vdelta2(+) T cell function may contribute to increased risk for tuberculosis in HIV-1-positive patients.
The Journal of Infectious Diseases 12/2005; 192(10):1806-14. DOI:10.1086/497146 · 5.78 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mycobacterium tuberculosis survives in macrophages in the face of acquired CD4(+) T-cell immunity, which controls but does not eliminate the organism. Gamma interferon (IFN-gamma) has a central role in host defenses against M. tuberculosis by activating macrophages and regulating major histocompatibility complex class II (MHC-II) antigen (Ag) processing. M. tuberculosis interferes with IFN-gamma receptor (IFN-gamma R) signaling in macrophages, but the molecules responsible for this inhibition are poorly defined. This study determined that the 19-kDa lipoprotein from M. tuberculosis inhibits IFN-gamma-regulated HLA-DR protein and mRNA expression in human macrophages. Inhibition of HLA-DR expression was associated with decreased processing and presentation of soluble protein Ags and M. tuberculosis bacilli to MHC-II-restricted T cells. Inhibition of HLA-DR required prolonged exposure to 19-kDa lipoprotein and was blocked with a monoclonal antibody specific for Toll-like receptor 2 (TLR-2). The 19-kDa lipoprotein also inhibited IFN-gamma-induced expression of Fc gamma RI. Thus, M. tuberculosis, through 19-kDa lipoprotein activation of TLR-2, inhibits IFN-gamma R signaling in human macrophages, resulting in decreased MHC-II Ag processing and recognition by MHC-II-restricted CD4 T cells. These findings provide a mechanism for M. tuberculosis persistence in macrophages.
Infection and Immunity 09/2003; 71(8):4487-97. DOI:10.1128/IAI.71.8.4487-4497.2003 · 4.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A hallmark of M. tuberculosis infection is the ability of most (90-95%) healthy adults to control infection through acquired immunity, in which antigen specific T cells and macrophages arrest growth of M. tuberculosis bacilli and maintain control over persistent bacilli. In addition to CD4+ T cells, other T cell subsets such as, gammadelta, CD8+ and CD1-restricted T cells have roles in the immune response to M. tuberculosis. A diverse T cell response allows the host to recognize a wider range of mycobacterial antigens presented by different families of antigen-presenting molecules, and thus greater ability to detect the pathogen. Macrophages are key antigen presenting cells for T cells, and M. tuberculosis survives and persists in this central immune cell. This is likely an important factor in generating this T cell diversity. Furthermore, the slow growth and chronic nature of M. tuberculosis infection results in prolonged exposure to antigens, and hence further T cell sensitization. The effector mechanisms used by T cells to control M. tuberculosis are poorly understood. To survive in macrophages, M. tuberculosis has evolved mechanisms to block immune responses. These include modulation of phagosomes, neutralization of macrophage effector molecules, stimulating the secretion of inhibitory cytokines, and interfering with processing of antigens for T cells. The relative importance of these blocking mechanisms likely depends on the stage of M. tuberculosis infection: primary infection, persistence, reactivation or active tuberculosis. The balance of the host-pathogen interaction in M. tuberculosis infection is determined by the interaction of T cells and infected macrophages. The outcome of this interaction results either in control of M. tuberculosis infection or active disease. A better understanding of this interaction will result in improved approaches to treatment and prevention of tuberculosis.
[Show abstract][Hide abstract] ABSTRACT: Vgamma9Vdelta2+ T cells (gammadelta T cells) are activated by Mycobacterium tuberculosis and recognize mycobacterial nonpeptide phosphoantigens. The role of antigen-presenting cells in the processing and presentation of phosphoantigens to Vgamma9Vdelta2+ T cells is not understood. We analyzed the role of macrophages for activation of gammadelta T cells by a new synthetic phosphoantigen bromohydrin pyrophosphate (BrHPP) and M. tuberculosis. Macrophages greatly increased gammadelta T-cell activation by both BrHPP and M. tuberculosis. Fixation of macrophages before infection demonstrated that uptake of M. tuberculosis was required for presentation to gammadelta T cells. Antigens of M. tuberculosis remained stably associated with macrophage surface and were not removed by paraformaldehyde fixation or washing. Macrophages processed M. tuberculosis for gammadelta T cells through a brefeldin A-insensitive pathway, suggesting that transport through the endoplasmic reticulum and Golgi complex of a putative presenting molecule is not important in the early processing of M. tuberculosis antigens for gammadelta T cells. Processing of M. tuberculosis was not eliminated by chloroquine, indicating that processing of gammadelta antigens is not dependent on acidic pH in the lysosomes. Chloroquine treatment of BrHPP-pulsed macrophages increased activation of gammadelta T cells. Ammonium chloride treatment of macrophages did not increase reactivity of gammadelta T cells to BrHPP, indicating that the effect of chloroquine was independent of pH changes in endosomes. Chloroquine, by inhibiting membrane traffic, may increase association and retention of phosphoantigens with cell surface membrane molecules on macrophages.
Infection and Immunity 09/2002; 70(8):4019-27. · 4.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Vγ9Vδ2+ T cells (γδ T cells) are activated by Mycobacterium tuberculosis and recognize mycobacterial nonpeptide phosphoantigens. The role of antigen-presenting cells in the processing and presentation of phosphoantigens to Vγ9Vδ2+ T cells is not understood. We analyzed the role of macrophages for activation of γδ T cells by a new synthetic phosphoantigen bromohydrin pyrophosphate (BrHPP) and M. tuberculosis. Macrophages greatly increased γδ T-cell activation by both BrHPP and M. tuberculosis. Fixation of macrophages before infection demonstrated that uptake of M. tuberculosis was required for presentation to γδ T cells. Antigens of M. tuberculosis remained stably associated with macrophage surface and were not removed by paraformaldehyde fixation or washing. Macrophages processed M. tuberculosis for γδ T cells through a brefeldin A-insensitive pathway, suggesting that transport through the endoplasmic reticulum and Golgi complex of a putative presenting molecule is not important in the early processing of M. tuberculosis antigens for γδ T cells. Processing of M. tuberculosis was not eliminated by chloroquine, indicating that processing of γδ antigens is not dependent on acidic pH in the lysosomes. Chloroquine treatment of BrHPP-pulsed macrophages increased activation of γδ T cells. Ammonium chloride treatment of macrophages did not increase reactivity of γδ T cells to BrHPP, indicating that the effect of chloroquine was independent of pH changes in endosomes. Chloroquine, by inhibiting membrane traffic, may increase association and retention of phosphoantigens with cell surface membrane molecules on macrophages.
Infection and Immunity 08/2002; 70(8):4019-4027. DOI:10.1128/IAI.70.8.4019-4027.2002 · 4.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This review on γδ T cells in human immunodeficiency virus 1 (HIV-1) infection focuses primarily on human T cells. It is aimed at providing the tools to understand the role of γδ T cells in HIV infection.