Phosphoantigen-activated V gamma 2V delta 2 T cells antagonize IL-2-induced CD4+CD25+Foxp3+ T regulatory cells in mycobacterial infection

The immunology of tuberculosis: from bench to bedside

Tuberculosis (TB) is an international public health priority and kills almost two million people annually. TB is out of control in Africa due to increasing poverty and HIV coinfection, and drug-resistant TB threatens to destabilize TB control efforts in several regions of the world. Existing diagnostic tools and therapeutic interventions for TB are suboptimal. Thus, new vaccines, immunotherapeutic interventions and diagnostic tools are urgently required to facilitate TB control efforts. An improved understanding of the immunopathogenesis of TB can facilitate the identification of correlates of immune protection, the design of effective vaccines, the rational selection of immunotherapeutic agents, the evaluation of new drug candidates, and drive the development of new immunodiagnostic tools. Here we review the immunology of TB with a focus on aspects that are clinically and therapeutically relevant. An immunologically orientated approach to tackling TB can only succeed with concurrent efforts to alleviate poverty and reduce the global burden of HIV.

Differentiation, distribution and gammadelta T cell-driven regulation of IL-22-producing T cells in tuberculosis

Differentiation, distribution and immune regulation of human IL-22-producing T cells in infections remain unknown. Here, we demonstrated in a nonhuman primate model that M. tuberculosis infection resulted in apparent increases in numbers of T cells capable of producing IL-22 de novo without in vitro Ag stimulation, and drove distribution of these cells more dramatically in lungs than in blood and lymphoid tissues. Consistently, IL-22-producing T cells were visualized in situ in lung tuberculosis (TB) granulomas by confocal microscopy and immunohistochemistry, indicating that mature IL-22-producing T cells were present in TB granuloma. Surprisingly, phosphoantigen HMBPP activation of Vgamma2Vdelta2 T cells down-regulated the capability of T cells to produce IL-22 de novo in lymphocytes from blood, lung/BAL fluid, spleen and lymph node. Up-regulation of IFNgamma-producing Vgamma2Vdelta2 T effector cells after HMBPP stimulation coincided with the down-regulated capacity of these T cells to produce IL-22 de novo. Importantly, anti-IFNgamma neutralizing Ab treatment reversed the HMBPP-mediated down-regulation effect on IL-22-producing T cells, suggesting that Vgamma2Vdelta2 T-cell-driven IFNgamma-networking function was the mechanism underlying the HMBPP-mediated down-regulation of the capability of T cells to produce IL-22. These novel findings raise the possibility to ultimately investigate the function of IL-22 producing T cells and to target Vgamma2Vdelta2 T cells for balancing potentially hyper-activating IL-22-producing T cells in severe TB.

Gamma-delta T-cell lymphomas

Peripheral T-cell lymphomas (TCLs) are uncommon neoplasms, accounting for about 12% of all lymphoid tumors worldwide. TCLs in which gammadelta T-cell receptors are expressed (gammadelta TCLs) are extremely aggressive and rare (<1% of lymphoid neoplasms). gammadelta TCLs originate from gammadelta T cells, a small subset of peripheral T cells with direct antigen recognition capability acting at the interface between innate and adaptive immunity. Two distinct gammadelta TCL entities are recognized: hepatosplenic T-cell lymphoma (HSTL) and primary cutaneous gammadelta T-cell lymphoma (PCGD-TCL). HSTL is a well-characterized extranodal lymphoma that has a disguised onset, secondary to intrasinusoidal infiltration of the spleen, liver and bone marrow, has a rapidly progressive course that is poorly responsive to chemotherapy, and often ensues in the setting of immune system suppression. PCGD-TCL can present with prominent epidermal involvement or with a panniculitis-like clinical picture that can be complicated by a concurrent hemophagocytic syndrome; the disease shows biological and phenotypic overlap with other extranodal gammadelta TCLs that involve the respiratory or gastrointestinal tract mucosa. The regular application of phenotypic and molecular techniques is crucial for the diagnosis of gammadelta TCLs. In this Review, we discuss the clinical and biological features, the diagnostic challenges and the therapeutic perspectives of HSTL and PCGD-TCL.

Expansion, reexpansion, and recall-like expansion of Vgamma2Vdelta2 T cells in smallpox vaccination and monkeypox virus infection

Little is known about the in vivo kinetics of T-cell responses in smallpox/monkeypox. We showed that macaque Vgamma2Vdelta2 T cells underwent 3-week-long expansion after smallpox vaccine immunization and displayed simple reexpansion in association with sterile anti-monkeypox virus (anti-MPV) immunity after MPV challenge. Virus-activated Vgamma2Vdelta2 T cells exhibited gamma interferon-producing effector function after phosphoantigen stimulation. Surprisingly, like alphabeta T cells, suboptimally primed Vgamma2Vdelta2 T cells in vaccinia virus/cidofovir-covaccinated macaques mounted major recall-like expansion after MPV challenge. Finally, Vgamma2Vdelta2 T cells localized in inflamed lung tissues for potential regulation. Our studies provide the first in vivo evidence that viruses, despite their inability to produce exogenous phosphoantigen, can induce expansion, reexpansion, and recall-like expansion of Vgamma2Vdelta2 T cells and stimulate their antimicrobial cytokine response.

DR*W201/P65 tetramer visualization of epitope-specific CD4 T-cell during M. tuberculosis infection and its resting memory pool after BCG vaccination

BACKGROUND

In vivo kinetics and frequencies of epitope-specific CD4 T cells in lymphoid compartments during M. tuberculosis infection and their resting memory pool after BCG vaccination remain unknown.

METHODOLOGY/FINDINGS

Macaque DR*W201 tetramer loaded with Ag85B peptide 65 was developed to directly measure epitope-specific CD4 T cells in blood and tissues form macaques after M. tuberculosis infection or BCG vaccination via direct staining and tetramer-enriched approach. The tetramer-based enrichment approach showed that P65 epitope-specific CD4 T cells emerged at mean frequencies of approximately 500 and approximately 4500 per 10(7) PBL at days 28 and 42, respectively, and at day 63 increased further to approximately 22,000/10(7) PBL after M. tuberculosis infection. Direct tetramer staining showed that the tetramer-bound P65-specific T cells constituted about 0.2-0.3% of CD4 T cells in PBL, lymph nodes, spleens, and lungs at day 63 post-infection. 10-fold expansion of these tetramer-bound epitope-specific CD4 T cells was seen after the P65 peptide stimulation of PBL and tissue lymphocytes. The tetramer-based enrichment approach detected BCG-elicited resting memory P65-specific CD4 T cells at a mean frequency of 2,700 per 10(7) PBL.

SIGNIFICANCE

Our work represents the first elucidation of in vivo kinetics and frequencies for tetramer-bound epitope-specific CD4 T cells in the blood, lymphoid tissues and lungs over times after M. tuberculosis infection, and BCG immunization.

NSOM/QD-based direct visualization of CD3-induced and CD28-enhanced nanospatial coclustering of TCR and coreceptor in nanodomains in T cell activation

Direct molecular imaging of nano-spatial relationship between T cell receptor (TCR)/CD3 and CD4 or CD8 co-receptor before and after activation of a primary T cell has not been reported. We have recently innovated application of near-field scanning optical microscopy (NSOM) and immune-labeling quantum dots (QD) to image Ag-specific TCR response during in vivo clonal expansion, and now up-graded the NSOM/QD-based nanotechnology through dipole-polarization and dual-color imaging. Using this imaging system scanning cell-membrane molecules at a best-optical lateral resolution, we demonstrated that CD3, CD4 or CD8 molecules were distinctly distributed as single QD-bound molecules or nano-clusters equivalent to 2–4 QD fluorescence-intensity/size on cell-membrane of un-stimulated primary T cells, and ∼6–10% of CD3 were co-clustering with CD4 or CD8 as 70–110 nm nano-clusters without forming nano-domains. The ligation of TCR/CD3 on CD4 or CD8 T cells led to CD3 nanoscale co-clustering or interaction with CD4 or CD8 co-receptors forming 200–500 nm nano-domains or >500 nm micro-domains. Such nano-spatial co-clustering of CD3 and CD4 or CD3 and CD8 appeared to be an intrinsic event of TCR/CD3 ligation, not purely limited to MHC engagement, and be driven by Lck phosphorylation. Importantly, CD28 co-stimulation remarkably enhanced TCR/CD3 nanoscale co-clustering or interaction with CD4 co-receptor within nano- or micro-domains on the membrane. In contrast, CD28 co-stimulation did not enhance CD8 clustering or CD3–CD8 co-clustering in nano-domains although it increased molecular number and density of CD3 clustering in the enlarged nano-domains. These nanoscale findings provide new insights into TCR/CD3 interaction with CD4 or CD8 co-receptor in T-cell activation.

Rapid alphabeta TCR-mediated responses in gammadelta T cells transduced with cancer-specific TCR genes

Adoptive T-cell transfer of in vitro cultured T cells derived from cancer patients with naturally developed immune responses has met with some success as an immunotherapeutic approach, although only a limited number of patients showed spontaneous immune responses. To find alternative ways, such as cancer-specific T-cell receptor (TCR) gene transfer, in preparation for sufficient numbers of antigen-specific T cells is an important issue in the field of adoptive T-cell therapy. Given the inherent disadvantage of alphabeta TCR transfer to other alphabeta T cells, namely the possible formation of mixed TCR heterodimers with endogenous alpha or beta TCR, we employed gammadelta T cells as a target for retroviral transfer of cancer-specific TCR and examined whether gammadelta T cells were useful as an alternative population for TCR transfer. Although retroviral transduction to gammadelta T cells with TCR alphabeta genes alone, isolated from a MAGE-A4(143-151)-specific alphabeta CD8(+) cytotoxic T lymphocyte (CTL) clone, did not provide sufficient affinity to recognize major histocompatibility (MHC)-peptide complexes due to the lack of CD8 co-receptor, gammadelta T cells co-transduced with TCR alphabeta and CD8 alphabeta genes acquired cytotoxicity against tumor cells and produced cytokines in both alphabeta- and gammadelta-TCR-dependent manners. Furthermore, alphabeta TCR and CD8-transduced gammadelta T cells, stimulated either through alphabeta TCR or gammadelta TCR, rapidly responded to target cells compared with conventional alphabeta T cells, reminiscent of gammadelta T cells. We propose alphabeta TCR-transduced gammadelta T cells as an alternative strategy for adoptive T-cell transfer.