Tumor recognition following Vgamma9Vdelta2 T cell receptor interactions with a surface F1-ATPase-related structure and apolipoprotein A-I

gammadeltaTCR ligands and lineage commitment

Two major T lymphocyte lineages--alphabeta and gammadelta T cells--develop in the thymus from common precursors. Differentiation of both lineages requires signals coming from TCRs. Development of alphabeta T cells is driven at early stages by signaling from the pre-TCR, most likely in a ligand-independent fashion, and later--by signals delivered by alphabetaTCRs binding to their ligands--classical or non-classical MHC molecules. gammadelta lineage cells likewise require TCR signaling for their differentiation. Recent work from several groups suggests that TCR signaling not only ensures the developmental progression towards alphabeta and gammadelta lineages but that signal strength instructs lineage fate: weaker TCR signal results in alphabeta and stronger--in gammadelta lineage commitment. However, as most gammadeltaTCRs remain orphan receptors, it is still debated whether strong signals from gammadeltaTCRs in development are generated in a ligand-dependent manner (as in the case of alphabetaTCRs), ligand-independent manner (as for pre-TCR) or both. Here we summarize evidence supporting a possible role for ligands in gammadelta T cell lineage commitment and the generation of gammadelta sublineages.

Gammadelta T cell effector functions: a blend of innate programming and acquired plasticity

Gammadelta T cells have several innate cell-like features that allow their early activation following recognition of conserved stress-induced ligands. Here we review recent observations revealing the ability of gammadelta T cells to rapidly produce cytokines that regulate pathogen clearance, inflammation and tissue homeostasis in response to tissue stress. These studies provide insights into how they acquire these properties, through both developmental programming in the thymus and functional polarization in the periphery. Innate features of gammadelta T cells underlie their non-redundant role in several physiopathological contexts and are therefore being exploited in the design of new immunotherapeutic approaches.

In vivo manipulation of Vgamma9Vdelta2 T cells with zoledronate and low-dose interleukin-2 for immunotherapy of advanced breast cancer patients

The potent anti-tumour activities of gammadelta T cells have prompted the development of protocols in which gammadelta-agonists are administered to cancer patients. Encouraging results from small Phase I trials have fuelled efforts to characterize more clearly the application of this approach to unmet clinical needs such as metastatic carcinoma. To examine this approach in breast cancer, a Phase I trial was conducted in which zoledronate, a Vgamma9Vdelta2 T cell agonist, plus low-dose interleukin (IL)-2 were administered to 10 therapeutically terminal, advanced metastatic breast cancer patients. Treatment was well tolerated and promoted the effector maturation of Vgamma9Vdelta2 T cells in all patients. However, a statistically significant correlation of clinical outcome with peripheral Vgamma9Vdelta2 T cell numbers emerged, as seven patients who failed to sustain Vgamma9Vdelta2 T cells showed progressive clinical deterioration, while three patients who sustained robust peripheral Vgamma9Vdelta2 cell populations showed declining CA15-3 levels and displayed one instance of partial remission and two of stable disease, respectively. In the context of an earlier trial in prostate cancer, these data emphasize the strong linkage of Vgamma9Vdelta2 T cell status to reduced carcinoma progression, and suggest that zoledronate plus low-dose IL-2 offers a novel, safe and feasible approach to enhance this in a subset of treatment-refractory patients with advanced breast cancer.

F1-adenosine triphosphatase displays properties characteristic of an antigen presentation molecule for Vgamma9Vdelta2 T cells

Human Vgamma9Vdelta2 T lymphocytes are activated by phosphoantigens provided exogenously or produced by tumors and infected cells. Activation requires a contact between Vgamma9Vdelta2 cells and neighboring cells. We previously reported a role for cell surface F1-adenosine triphosphatase (ATPase) in T cell activation by tumors and specific interactions between Vgamma9Vdelta2 TCRs and purified F1-ATPase. 721.221 cells do not express surface F1-ATPase and do not support phosphoantigen responses unless they are rendered apoptotic by high doses of zoledronate, a treatment that promotes F1-expression as well as endogenous phosphoantigen production. By monitoring calcium flux in single cells, we show in this study that contact of T cells with F1-ATPase on polystyrene beads can partially replace the cell-cell contact stimulus during phosphoantigen responses. Triphosphoric acid 1-adenosin-5'-yl ester 3-(3-methylbut-3-enyl) ester, an adenylated derivative of isopentenyl pyrophosphate, can stably bind to F1-ATPase-coated beads and promotes TCR aggregation, lymphokine secretion, and activation of the cytolytic process provided that nucleotide pyrophosphatase activity is present. It also acts as an allosteric activator of F1-ATPase. In the absence of Vgamma9Vdelta2 cells, triphosphoric acid 1-adenosin-5'-yl ester 3-(3-methylbut-3-enyl) ester immobilized on F1-ATPase is protected from nucleotide pyrophosphatase activity, as is the antigenic activity of stimulatory target cells. Our experiments support the notion that Vgamma9Vdelta2 T cells are dedicated to the recognition of phosphoantigens on cell membranes in the form of nucleotide derivatives that can bind to F1-ATPase acting as a presentation molecule.

Vgamma2Vdelta2 T Cell Receptor recognition of prenyl pyrophosphates is dependent on all CDRs

gammadelta T cells differ from alphabeta T cells in the Ags they recognize and their functions in immunity. Although most alphabeta TCRs recognize peptides presented by MHC class I or II, human gammadelta T cells expressing Vgamma2Vdelta2 TCRs recognize nonpeptide prenyl pyrophosphates. To define the molecular basis for this recognition, the effect of mutations in the TCR CDR was assessed. Mutations in all CDR loops altered recognition and cover a large footprint. Unlike murine gammadelta TCR recognition of the MHC class Ib T22 protein, there was no CDR3delta motif required for recognition because only one residue is required. Instead, the length and sequence of CDR3gamma was key. Although a prenyl pyrophosphate-binding site was defined by Lys109 in Jgamma1.2 and Arg51 in CDR2delta, the area outlined by critical mutations is much larger. These results show that prenyl pyrophosphate recognition is primarily by germline-encoded regions of the gammadelta TCR, allowing a high proportion of Vgamma2Vdelta2 TCRs to respond. This underscores its parallels to innate immune receptors. Our results also provide strong evidence for the existence of an Ag-presenting molecule for prenyl pyrophosphates.

Human Vgamma9Vdelta2 T cells: from signals to functions

Human Vgamma9Vdelta2 T cells, a major innate-like peripheral T cell subset, are thought to play in vivo a key role in innate and adaptive immune responses to infection agents and tumors. Vgamma9Vdelta2 T cell activation is tightly regulated by a variety of activating or inhibitory receptors which are specific for constitutively expressed or stress-modulated ligands. However, the mechanisms and signal transduction pathways regulating their broad effector functions, such as cytotoxicity and cytokine responses, remain poorly understood. Here we provide an updated overview of the activation modalities of Vgamma9Vdelta2 T cells by highlighting the respective role played by T cell receptor (TCR) versus non-TCR stimuli, and focus on recent studies showing how Vgamma9Vdelta2 T cells integrate the numerous activating and inhibitory signals and translate them into a particular effector and biological function. A better understanding of these critical issues should help optimize immunotherapeutic approaches targeting Vgamma9Vdelta2 T cells.

Ligand recognition during thymic development and gammadelta T cell function specification

gammadelta T cells develop in the thymus before entering the periphery. Recent work suggests that thymic development does little to constrain gammadelta T cell antigen specificities, but instead determines their effector fate. When triggered through the T cell receptor, ligand-naïve gammadelta T cells produce IL-17, ligand-experienced cells make IFN-gamma and those that are strongly self-reactive make IL-4. Importantly, gammadelta T cells are able to make cytokines immediately upon TCR engagement. These characteristics allow gammadelta T cells to initiate an acute inflammatory response to pathogens and to host antigens revealed by injury. These advances warrant a fresh look at how gammadelta T cells may function in the immune system.

Repertoire development and the control of cytotoxic/effector function in human gammadelta T cells

T cells develop into two major populations distinguished by their T cell receptor (TCR) chains. Cells with the alphabeta TCR generally express CD4 or CD8 lineage markers and mostly fall into helper or cytotoxic/effector subsets. Cells expressing the alternate gammadelta TCR in humans generally do not express lineage markers, do not require MHC for antigen presentation, and recognize nonpeptidic antigens. We are interested in the dominant Vgamma2Vdelta2+ T cell subset in human peripheral blood and the control of effector function in this population. We review the literature on gammadelta T cell generation and repertoire selection, along with recent work on CD56 expression and defining a cytotoxic/effector lineage within the phosphoantigen-reactive Vgamma2Vdelta2 cells. A unique mechanism for MHC-independent repertoire selection is linked to the control of effector function that is vital to the role for gammadelta T cells in tumor surveillance. Better understanding of these mechanisms will improve our ability to exploit this population for tumor immunotherapy.

Identification of a panel of ten cell surface protein antigens associated with immunotargeting of leukemias and lymphomas by peripheral blood gammadelta T cells

BACKGROUND

Vgamma9Vdelta2 T lymphocytes are regarded as promising mediators of cancer immunotherapy due to their capacity to eliminate multiple experimental tumors, particularly within those of hematopoietic origin. However, Vgamma9Vdelta2 T-cell based lymphoma clinical trials have suffered from the lack of biomarkers that can be used as prognostic of therapeutic success.

DESIGN AND METHODS

We have conducted a comprehensive study of gene expression in acute lymphoblastic leukemias and non-Hodgkin's lymphomas, aimed at identifying markers of susceptibility versus resistance to Vgamma9Vdelta2 T cell-mediated cytotoxicity. We employed cDNA microarrays and quantitative real-time PCR to screen 20 leukemia and lymphoma cell lines, and 23 primary hematopoietic tumor samples. These data were analyzed using state-of-the-art bioinformatics, and gene expression patterns were correlated with susceptibility to Vgamma9Vdelta2 T cell mediated cytolysis in vitro.

RESULTS

We identified a panel of 10 genes encoding cell surface proteins that were statistically differentially expressed between "gammadelta-susceptible" and "gammadelta-resistant" hematopoietic tumors. Within this panel, 3 genes (ULBP1, TFR2 and IFITM1) were associated with increased susceptibility to Vgamma9Vdelta2 T-cell cytotoxicity, whereas the other 7 (CLEC2D, NRP2, SELL, PKD2, KCNK12, ITGA6 and SLAMF1) were enriched in resistant tumors. Furthermore, some of these candidates displayed a striking variance of expression among primary follicular lymphomas and T-cell acute lymphoblastic leukemias.

CONCLUSIONS

Our results suggest that hematopoietic tumors display a highly variable repertoire of surface proteins that can impact on Vgamma9Vdelta2 cell-mediated immunotargeting. The prognostic value of the proposed markers can now be evaluated in upcoming Vgamma9Vdelta2 T cell-based lymphoma/leukemia clinical trials.

The recognition of gammadelta TCR to protein antigen does not depend on the hydrophobic I97 residue of CDR3delta

The crystal structure analysis demonstrated that the hydrophobic amino acid residue (isolecuine/leucine/valine) at conserved position 97 of Vdelta2 TCR plays an important role in recognizing the non-peptide antigen. But its importance to protein antigen remains unclear until now. In the present study, we focus on the role of hydrophobic amino acid residue at conserved position 97 of Vdelta2 TCR in complementarity determining region (CDR)3delta-mediated binding to protein antigen. We employed CDR3delta peptide and membrane-engineered gammadelta TCR as detecting molecules with mutated 97 hydrophobic amino acid residue in CDR3delta (nominated as OT10), a Vdelta2 CDR3 sequence derived from tumor infiltrating lymphocytes in ovarian epithelial carcinoma (OEC). Binding assays revealed that OT10 peptide and membrane-engineered gammadelta TCR (gammadelta TCR transfected cells with OT10 sequence) could bind specifically ovarian tumor cell line (SKOV3). The mutant analysis indicated that any amino acid substitution at position deltaI97 could abolish the response of the transfected cells to iso-butylamine, a known non-peptide antigen of gammadelta T cells. But amino acid substitution of isoleucine at position delta97 did not change the responsiveness of gammadelta TCR transfected cell to protein antigen. Our data suggested that a mechanism other than non-peptide antigen might mediate the recognition of Vdelta2gammadelta T cells for protein antigen. This finding may provide a possibility that gammadelta TCR recognize different ligands in diversity manners.

V gamma 9V delta 2 T lymphocytes efficiently recognize and kill zoledronate-sensitized, imatinib-sensitive, and imatinib-resistant chronic myelogenous leukemia cells

Imatinib mesylate (imatinib), a competitive inhibitor of the BCR-ABL tyrosine kinase, is highly effective against chronic myelogenous leukemia (CML) cells. However, because 20-30% of patients affected by CML display either primary or secondary resistance to imatinib, intentional activation of Vgamma9Vdelta2 T cells by phosphoantigens or by agents that cause their accumulation within cells, such as zoledronate, may represent a promising strategy for the design of a novel and highly innovative immunotherapy capable to overcome imatinib resistance. In this study, we show that Vgamma9Vdelta2 T lymphocytes recognize, trogocytose, and efficiently kill imatinib-sensitive and -resistant CML cell lines pretreated with zoledronate. Vgamma9Vdelta2 T cell cytotoxicity was largely dependent on the granule exocytosis- and partly on TRAIL-mediated pathways, was TCR-mediated, and required isoprenoid biosynthesis by zoledronate-treated CML cells. Importantly, Vgamma9Vdelta2 T cells from patients with CML can be induced by zoledronate to develop antitumor activity against autologous and allogeneic zoledronate-treated leukemia cells, both in vitro and when transferred into immunodeficient mice in vivo. We conclude that intentional activation of Vgamma9Vdelta2 T cells by zoledronate may substantially increase their antileukemia activities and represent a novel strategy for CML immunotherapy.

The MHC class Ib protein ULBP1 is a nonredundant determinant of leukemia/lymphoma susceptibility to gammadelta T-cell cytotoxicity

On the path to successful immunotherapy of hematopoietic tumors, gammadelta T cells offer great promise because of their human leukocyte antigen (HLA)-unrestricted targeting of a wide variety of leukemias/lymphomas. However, the molecular mechanisms underlying lymphoma recognition by gammadelta T cells remain unclear. Here we show that the expression levels of UL16-binding protein 1 (ULBP1) determine lymphoma susceptibility to gammadelta T cell-mediated cytolysis. Consistent with this, blockade of NKG2D, the receptor for ULBP1 expressed on all Vgamma9(+) T cells, significantly inhibits lymphoma cell killing. Specific loss-of-function studies demonstrate that the role of ULBP1 is nonredundant, highlighting a thus far unique physiologic relevance for tumor recognition by gammadelta T cells. Importantly, we observed a very wide spectrum of ULBP1 expression levels in primary biopsies obtained from lymphoma and leukemia patients. We suggest this will impact on the responsiveness to gammadelta T cell-based immunotherapy, and therefore propose ULBP1 to be used as a leukemia/lymphoma biomarker in upcoming clinical trials.

Gammadelta T cells and the lymphoid stress-surveillance response

The investigation of gammadelta T cells has identified a rapid lymphoid stress-surveillance response to microbial and nonmicrobial tissue perturbation. In addition to providing local protection, this response provides an immediate source of cytokines, chemokines, and other functions that can substantially affect downstream, adaptive immunity. Recent studies have identified striking mechanisms by which gammadelta cells meet the requirements of stress surveillance. For example, high response frequencies can reflect a unique nature of antigen engagement by the T cell receptor (TCR), developmental focusing of the repertoire by selection events, or the use of nonclonotypic receptors to initiate responses. Likewise, rapid functional deployment can be facilitated by the preprogramming of gammadelta cells during development. Additionally, gammadelta cells can directly influence adaptive immunity by functioning as antigen-presenting cells. With lymphoid stress surveillance likely to underpin numerous aspects of inflammation, tumor immunology, infectious disease, and autoimmunity, this perspective considers its properties and its emerging potential for clinical manipulation.

Tandem-epitope peptide: a novel stimulator for gammadeltaT cells in tumor immunotherapy

T cells bearing the gammadeltaTCR have become the new candidate effectors in tumor immunotherapy because of their potent cytotoxicity toward various tumor cells. However, a crucial issue in using gammadeltaT cells as effectors is how to effectively expand tumor-reactive gammadeltaT cells and enhance their functions. In previously studies, we used synthesized CDR3-peptide derived from ovarian epithelial carcinoma (OEC) infiltrating gammadeltaT cells (gammadeltaTILs) as specific probe to screen a phage display peptide library and identified seven putative epitopes named EP1-EP7. All seven putative epitopes could not only bind to gammadeltaT cells, but also activate them in vitro. To enhance the activating capability of these identified gammadeltaT cell ligands, we have constructed four types of GST epitope fusion proteins containing single epitope or tandem epitopes. These GST epitope fusion proteins could not only promote the secretion of cytokines, but also enhance the proliferation and cytotoxicity of gammadeltaT cells in vitro. Significant difference between GST tandem-epitope groups and GST single-epitope group in their activating capability was observed (P<0.05). Furthermore, GST epitope fusion proteins could suppress the growth of tumor and prolong the survival of BALB/c nude mice inoculated with human OEC cell line (P<0.05). In conclusion, these results provide a novel approach for tumor immunotherapy based on gammadeltaT cells.

Antigen specificity of gammadelta T cells depends primarily on the flanking sequences of CDR3delta

The structural basis that determines the specificity of gammadelta T cell receptor (TCR) recognition remains undefined. Our previous data show that the complementary determining region of human TCRdelta (CDR3delta) is critical to ligand binding. Here we used linear and configurational approaches to examine the roles of V, N-D-N, or J regions in CDR3delta-mediated antigen recognition. Surprisingly, we found that the binding activities of CDR3delta from different gammadelta TCRs to their target tissues and ligands depend on the conserved flanking sequences (V and J) but not as much on the D region of CDR3delta fragment. We further defined the key residues in the V and J regions of CDR3delta fragments, including the cysteine residue in the V fragment and the leucine residue in the J fragment that determine their ligand binding specificity. Our results demonstrate that TCRdelta primarily uses conserved flanking regions to bind ligands. This finding may provide an explanation for the limited number of gammadelta TCR ligands that have as yet been identified.

Zoledronate facilitates large-scale ex vivo expansion of functional gammadelta T cells from cancer patients for use in adoptive immunotherapy

BACKGROUND

Human gammadelta T cells can be activated by phospho-antigens and aminobisphosphonates such as zoledronate. Because they can kill tumor cells in a major histocompatibility complex (MHC)-unrestricted manner, adoptive transfer of activated gammadelta T cells may represent a novel cancer immunotherapy. We tested whether gammadelta T cells from advanced cancer patients can be expanded by zoledronate.

METHODS

Peripheral blood mononuclear cells from healthy donors and patients with advanced non-small cell lung cancer, bone metastatic breast or prostate cancer, or lung metastatic colorectal cancer, were stimulated with zoledronate (5 microM) and interleukin (IL)-2 (1000 IU/mL) for 14 days. The phenotype and function of the expanded gammadelta T-cell populations from healthy donors and cancer patients were compared.

RESULTS

Gammadelta T cells from cancer patients and healthy donors responded to zoledronate equally well in terms of both phenotype and function. gammadelta T cells grew rapidly in vitro and expression of effector molecules, such as interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, perforin, granzyme B, FasL and TRAIL, increased over time. Cytotoxicity peaked on days 12-14, and proliferation continued up to 14 days, during which time>1x10(9) gammadelta T cells could be obtained from a starting sample of 45-70 mL peripheral blood.

DISCUSSION

Using the agent zoledronate, already widely used in the clinic, we have established that efficient large-scale ex vivo expansion of gammadelta T cells from cancer patients is possible. These cells exert potent cytotoxicity and may be used for autologous cellular immunotherapy of cancer.

DNAX accessory molecule-1 (CD226) promotes human hepatocellular carcinoma cell lysis by Vgamma9Vdelta2 T cells

Human Vgamma9Vdelta2 T lymphocytes can be activated by nonpeptidic antigens such as the mevalonate pathway-derived isopentenyl pyrophosphate or synthetic phosphoantigen such as bromohydrin pyrophosphate. They display a strong cytotoxic activity against several tumor types, including hepatocellular carcinoma (HCC). Little is known about the mechanisms underlying Vgamma9Vdelta2 T-cell recognition of tumor cells, but there is strong evidence that activating NK receptors play a role in gammadelta T-cell cytotoxicity. In this study, we showed that the two NK receptors DNAX accessory molecule-1 (DNAM-1) and CD96 were expressed by Vgamma9Vdelta2 T cells. The ligands Nectin-like-5 specific of both DNAM-1 and CD96, and also Nectin-2, an additional ligand of DNAM-1, were present on all HCC cell lines analyzed. Furthermore, we demonstrated by mAb-mediated masking experiments that cytotoxicity against HCC cells as well as IFN-gamma production in gammadelta T cells were dependent on DNAM-1. Our experiments indicated that Nectin-like-5 but not Nectin-2 was involved in DNAM-1-dependent gammadelta T-cell functions. We did not reveal a role for CD96 in the killing of HCC cells. Finally, we showed by combined mAb-mediated blockade that DNAM-1 and NKG2D could cooperate in the cell lysis of HCC.

Efficient killing of human colon cancer stem cells by gammadelta T lymphocytes

Colon cancer comprises a small population of cancer stem cells (CSC) that is responsible for tumor maintenance and resistant to cancer therapies, possibly allowing for tumor recapitulation once treatment stops. We previously demonstrated that such chemoresistance is mediated by autocrine production of IL-4 through the up-regulation of antiapoptotic proteins. Several innate and adaptive immune effector cells allow for the recognition and destruction of cancer precursors before they constitute the tumor mass. However, cellular immune-based therapies have not been experimented yet in the population of CSCs. Here, we show that the bisphosphonate zoledronate sensitizes colon CSCs to Vgamma9Vdelta2 T cell cytotoxicity. Proliferation and production of cytokines (TNF-alpha and IFN-gamma) and cytotoxic and apoptotic molecules (TRAIL and granzymes) were also induced after exposure of Vgamma9Vdelta2 T cells to sensitized targets. Vgamma9Vdelta2 T cell cytotoxicity was mediated by the granule exocytosis pathway and was highly dependent on isoprenoid production by of tumor cells. Moreover, CSCs recognition and killing was mainly TCR mediated, whereas NKG2D played a role only when tumor targets expressed several NKG2D ligands. We conclude that intentional activation of Vgamma9Vdelta2 T cells by zoledronate may substantially increase antitumor activities and represent a novel strategy for colon cancer immunotherapy.

Coupling factor 6 as a novel vasoactive and proatherogenic peptide in vascular endothelial cells

Coupling factor 6 (CF6) is composed of 76 amino acids and is present in the peripheral stalk of mitochondrial ATP synthase. The generation of CF6 is positively regulated by tumor necrosis factor alpha and shear stress via nuclear factor kappaB, and by high glucose via protein kinase C and p38 mitogen-activated protein kinase. CF6 is released outside of the cells from vascular endothelial cells, and binds to the beta-subunit of the plasma membrane-bound ATP synthase in vascular endothelial cells and leads to intracellular acidosis. CF6 produces vasoconstriction, and the biological active site resides at the C-terminal portion. CF6 suppresses prostacyclin generation via inhibition of cytosolic phospholipase A(2). CF6 also suppresses nitric oxide synthase activity via an increase in asymmetric dimethylarginine and a decrease in platelet/endothelial cell adhesion molecule-1. CF6 induces the gene and protein expression of proatherogenic molecules such as endothelin 2, urokinase type plasminogen activator receptor, estrogen receptor beta, a soluble short form of vascular endothelial growth factor receptor-1, and lectin-like oxidized low-density lipoprotein receptor-1. The plasma level of CF6 is elevated in patients with essential hypertension, diabetes mellitus, end-stage renal disease, acute myocardial infarction, and coronary heart disease. It is likely that CF6 contributes to the pathogenesis of cardiovascular diseases, but further intensive investigation is needed.

Inhibition of ATP synthase by chlorinated adenosine analogue

8-Chloroadenosine (8-Cl-Ado) is a ribonucleoside analogue that is currently in clinical trial for chronic lymphocytic leukemia. Based on the decline in cellular ATP pool following 8-Cl-Ado treatment, we hypothesized that 8-Cl-ADP and 8-Cl-ATP may interfere with ATP synthase, a key enzyme in ATP production. Mitochondrial ATP synthase is composed of two major parts; F(O) intermembrane base and F1 domain, containing alpha and beta subunits. Crystal structures of both alpha and beta subunits that bind to the substrate, ADP, are known in tight binding (alpha(dp)beta(dp)) and loose binding (alpha(tp)beta(tp)) states. Molecular docking demonstrated that 8-Cl-ADP/8-Cl-ATP occupied similar binding modes as ADP/ATP in the tight and loose binding sites of ATP synthase, respectively, suggesting that the chlorinated nucleotide metabolites may be functional substrates and inhibitors of the enzyme. The computational predictions were consistent with our whole cell biochemical results. Oligomycin, an established pharmacological inhibitor of ATP synthase, decreased both ATP and 8-Cl-ATP formation from exogenous substrates, however, did not affect pyrimidine nucleoside analogue triphosphate accumulation. Synthesis of ATP from ADP was inhibited in cells loaded with 8-Cl-ATP. These biochemical studies are in consent with the computational modeling; in the alpha(tp)beta(tp) state 8-Cl-ATP occupies similar binding as ANP, a non-hydrolyzable ATP mimic that is a known inhibitor. Similarly, in the substrate binding site (alpha(dp)beta(dp)) 8-Cl-ATP occupies a similar position as ATP mimic ADP-BeF(3)(-). Collectively, our current work suggests that 8-Cl-ADP may serve as a substrate and the 8-Cl-ATP may be an inhibitor of ATP synthase.

The NKG2D ligand ULBP4 binds to TCRgamma9/delta2 and induces cytotoxicity to tumor cells through both TCRgammadelta and NKG2D

UL16-binding proteins (ULBPs) belong to a family of ligands for NKG2D activating receptor of human natural killer (NK) cells. We previously reported that RAET1E2, a soluble isoform of the RAET1E (ULBP4), inhibits NKG2D-mediated NK cytotoxicity. In this study, we examined whether ULBP4 could be recognized by gammadeltaT cells via TCRgammadelta. Here we show that immobilized soluble ULBP4 (rULBP4) induces the proliferation of human ovarian epithelial carcinoma- or colonic carcinoma-derived Vdelta2(+) T cells in vitro. These Vdelta2(+) T cells secrete Th1 cytokines and display a strong cytolytic activity toward ULBP4-transfected targets. We also show that ULBP4 binds to a soluble chimeric protein containing TCRgamma9/delta2 and activates TCR(-) Jurkat T cells transfected with TCRgamma9/delta2. Moreover, both TCRgammadelta and NKG2D are involved in ULBP4-induced activation and cytotoxicity of gammadeltaT cells. We found that ULBP4 is expressed not only on human tumor cells, but also on Epstein-Barr virus (EBV)-infected peripheral blood cells. Taken together, our data suggest that ULBP4 functions as a ligand for both TCRgammadelta and NKG2D and may play a key role in immune surveillance of tumor development and clearance of viral infection.

Innate T cell responses in human gut

One arm of the gut-associated immune system is represented by a vast collection of T lymphocytes which participate in the subtle interplay between innate and adaptive immune mechanisms and maintain homeostasis at the main body external surface. Mounting data are providing exciting new insight into the innate-like mechanisms which enable intestinal T cells to rapidly sense local conditions and which broaden the spectrum of their functions and regulation at this strategic location. Herein we discuss how innate-like T cell recognition by unconventional T cell subsets and expression of innate NK receptors might modulate immune T cell responses in the human normal or diseased intestine.

Photoaffinity antigens for human gammadelta T cells

Vgamma2Vdelta2 T cells comprise the major subset of peripheral blood gammadelta T cells in humans and expand during infections by recognizing small nonpeptide prenyl pyrophosphates. These molecules include (E)-4-hydroxy-3-methyl-but-2-enyl-pyrophosphate (HMBPP), a microbial isoprenoid intermediate, and isopentenyl pyrophosphate, an endogenous isoprenoid intermediate. Recognition of these nonpeptide Ags is mediated by the Vgamma2Vdelta2 T cell Ag receptor. Several findings suggest that prenyl pyrophosphates are presented by an Ag-presenting molecule: contact between T cells and APC is required, the Ags do not bind the Vgamma2Vdelta2 TCR directly, and Ag recognition is abrogated by TCR mutations in CDRs distant from the putative Ag recognition site. Identification of the putative Ag-presenting molecule, however, has been hindered by the inability to achieve stable association of nonpeptide prenyl pyrophosphate Ags with the presenting molecule. In this study, we show that photoaffinity analogues of HMBPP, meta/para-benzophenone-(methylene)-prenyl pyrophosphates (m/p-BZ-(C)-C(5)-OPP), can crosslink to the surface of tumor cell lines and be presented as Ags to gammadelta T cells. Mutant tumor cell lines lacking MHC class I, MHC class II, beta(2)-microglobulin, and CD1, as well as tumor cell lines from a variety of tissues and individuals, will all crosslink to and present m-BZ-C(5)-OPP. Finally, pulsing of BZ-(C)-C(5)-OPP is inhibited by isopentenyl pyrophosphate and an inactive analog, suggesting that they bind to the same molecule. Taken together, these results suggest that nonpeptide Ags are presented by a novel-Ag-presenting molecule that is widely distributed and nonpolymorphic, but not classical MHC class I, MHC class II, or CD1.

Dysregulation of the host mevalonate pathway during early bacterial infection activates human TCR gamma delta cells

Primates, but not rodents, have T cell receptor Vgamma9-Vdelta2 T cells bridging innate and adaptive antimicrobial immunity. This T cell population is activated by prenyl pyrophosphates isolated from microbial or eukaryotic cells. Although the microbial metabolites are more active than the cellular ones, their involvement in TCR gammadelta activation during infection has not been studied. Here, we show that, during the initial phases of infections with Escherichia coli and Staphylococcus aureus, TCR gammadelta cells are activated by endogenous mevalonate metabolites. Infections with low bacteria inocula up-regulate the production and accumulation of host-derived TCR gammadelta stimulatory antigens within 1 h, which is followed by a peak of TCR gammadelta cell activation at 5 h. Infections induce the accumulation and dephosphorylation of the hydroxymethylglutaryl-coenzyme A reductase, the rate-limiting enzyme of the mevalonate pathway, resulting in increased activity of this enzyme and in increased synthesis of intermediate metabolites. Thus, primates have evolved the ability to readily respond to bacterial infection by sensing the dysregulation of the mevalonate pathway within infected cells, as a mechanism of immediate antimicrobial immunity.

Targeting solid tumors via T cell receptor complementarity-determining region 3delta in an engineered antibody

Human Vdelta2 gammadelta T lymphocytes killed multiple solid tumors, even displaying comparable therapeutic efficacy with anti-tumor chemical-cis-platinum in an adoptive experiment in both nude and SCID murine model shown in present study. We previously found that T cell receptor (TCR) gammadelta recognize tumors via complementarity-determining region 3 (CDR3), briefly named as CDR3delta. Based on characteristics of specific binding of CDR3delta to tumor targets, we developed a novel tumor-targeting antibody, whose CDR3 in heavy chain is replaced by CDR3delta sequence derived from human ovarian carcinoma (OEC) infiltrating gammadelta T cells (gammadeltaTILs). This CDR3delta-grafted antibody OT3 exhibited specific binding activities to OEC line SKOV3 both in vitro and in vivo, which included specific binding to several tumor cell lines, interacting with heat shock protein (HSP) 60 and triggering ADCC against tumors in vitro, as well as displaying tumor imaging by radioisotope 99mTc-labeled antibody OT3 in vivo. Moreover, immunotoxin OT3-DT, CDR3delta-grafted antibody OT3 chemically conjugated with diphtheria toxin (DT) showed the anti-tumor effect on the growth of several solid tumors including OEC, cervix adenocarcinoma, hepatocellular carcinoma, and rectum adenocarcinoma to various extents in nude mice. Therefore, we have found and confirmed a novel therapeutic strategy for targeting solid tumors, making use of immune recognition characteristics of gammadelta T cells.

Dual functions of a monoclonal antibody against cell surface F1F0 ATP synthase on both HUVEC and tumor cells

AIM

To generate a monoclonal antibody (McAb) against cell surface F1F0 ATP synthase (ATPase) and observe its antitumoral activity on both human umbilical vein endothelial cells (HUVEC) and tumor cells.

METHODS

Hybridoma cells secreting McAb against ATPase were produced by polyethylene glycol-mediated fusions and screened by ELISA. The specificity of McAb was demonstrated by immunofluorescence and confocal imaging, as well as flow cytometry analysis. After the blockade of surface ATPase with McAb on HUVEC and human breast adenocarcinoma MDA-MB-231 cells, an ATP determination kit and CellTiter96 AQueous Assay (MTS) assay were used to detect the effect of the antibody on extracellular ATP modification and cell proliferation. A cellular cytotoxicity assay in combination with doxorubicin, and a cell migration assay on MDA-MB-231 cells were used to determine the antitumoral activity. Finally, a HUVEC tube formation assay was used to detect the antiangiogenic effect of McAb178-5G10.

RESULTS

A monoclonal antibody (McAb178-5G10) against the beta-subunit of ATPase was generated, and its reactivity toward HUVEC and tumor cells was studied. We demonstrate that McAb178-5G10 binds to ATPase at the cell surface, where it is able to inhibit ATP synthesis. This antibody also prevents the proliferation of HUVEC and MDA-MB-231 cells. Furthermore, McAb178-5G10 enhances the tumoricidal effects of doxorubicin (P<0.05), inhibits the migration of MDA-MB- 231 in transwell assays (P<0.01), and disrupts HUVEC tube formation on Matrigel (P<0.01).

CONCLUSION

McAb178-5G10 binds preferentially to cell surface ATPase, blocks ATP synthesis, and exhibits both antiangiogenic and antitumorigenic effects.

An autonomous CDR3delta is sufficient for recognition of the nonclassical MHC class I molecules T10 and T22 by gammadelta T cells

It remains unclear whether gammadelta T cell antigen receptors (TCRs) detect antigens in a way similar to antibodies or alphabeta TCRs. Here we show that reactivity between the G8 and KN6 gammadelta TCRs and the major histocompatibility complex class Ib molecule T22 could be recapitulated, with retention of wild-type ligand affinity, in an alphabeta TCR after grafting of a G8 or KN6 complementarity-determining region 3-delta (CDR3delta) loop in place of the CDR3alpha loop of an alphabeta TCR. We also found that a shared sequence motif in CDR3delta loops of all T22-reactive gammadelta TCRs bound T22 in energetically distinct ways, and that T10(d), which bound G8 with weak affinity, was converted into a high-affinity ligand by a single point mutation. Our results demonstrate unprecedented autonomy of a single CDR3 loop in antigen recognition.

Macrophages express multiple ligands for gammadelta TCRs

As only a handful of ligands have been identified, the general nature of the ligands recognized by gammadelta T cells remains unresolved. In this study, soluble multimerized gammadelta T cell receptors (smTCRs) representing the TCRs of two gammadelta T cell subsets common in the mouse were used to detect and track their own ligands. Ligands for both subsets were found on resident peritoneal macrophages taken from untreated mice, and the expression of both was further induced by Listeria monocytogenes infection. Nevertheless, the two types of ligand differ from one another in abundance, in the kinetics of their induction following Listeria infection, and in their ability to be induced by in vitro culture with lipopolysaccharide (LPS). Surprisingly, because both are detectable on normal macrophages, these host-derived ligands are likely expressed constitutively, but are induced to higher levels of expression by stress or inflammation. In contrast to T22 and other known cell surface ligands for gammadelta T cells in mice and humans, expression of these smTCR-defined ligands does not depend on beta2-microglobulin, suggesting that they are not MHC class I or class I-like molecules.

Vgamma9Vdelta2 T cell-mediated recognition of human solid tumors. Potential for immunotherapy of hepatocellular and colorectal carcinomas

INTRODUCTION

Vgamma9Vdelta2 T lymphocytes are reported to participate in the anti-tumor immune surveillance in human. They are known to recognize phosphoantigens and molecules expressed on cells undergoing neoplasic transformation. In this study, we investigated phenotype and anti-tumor cytotoxicity of ex vivo expanded Vgamma9Vdelta2 T cells in view of adoptive immunotherapy.

MATERIALS AND METHODS

Experiments were performed with peripheral blood samples from eleven patients [six colorectal carcinoma (CRC), four hepatocellular carcinoma (HCC), one sarcoma] and sixteen healthy donors.

RESULTS/DISCUSSION

Ex vivo expansion of Vgamma9Vdelta2 T cells could be achieved by a single dose of phosphoantigen, either bromohydrin pyrophosphate or zoledronate, and supported by exogenous IL-2. After 2 weeks, expanded Vgamma9Vdelta2 T lymphocytes acquired the effector memory phenotype CD45RA(-)CD45RO(high)CD27(-). They expressed NKG2D and CD161 and the proinflammatory CXCR3 and CCR5 chemokine receptors. Vgamma9Vdelta2 T cells displayed a strong lytic activity toward a broad panel of tumor cell lines or primary cultures. Interestingly, HCC and CRC primary cells could be lysed by autologous Vgamma9Vdelta2 T cells whereas autologous normal cells were not sensitive to the lysis. mAbs blocking assays demonstrated that TCR was the most important receptor involved in the lysis of tumor cells. However, NKG2D receptor could deliver a costimulatory signal enhancing the lysis of HCC and CRC tumors expressing MICA/B. Treatment of tumor cells by the mevalonate pathway inhibitor, zoledronate, enhanced the killing of both HCC and CRC. Expansion index of Vgamma9Vdelta2 T cells was in similar levels in healthy donors or in cancer patients and total expansion was suitable for adoptive immunotherapy.

CONCLUSION

These results provide a rationale for the clinical evaluation of Vgamma9Vdelta2 T lymphocytes in HCC and CRC.

In vitro expansion of gamma delta T cells with anti-myeloma cell activity by Phosphostim and IL-2 in patients with multiple myeloma

T-cell-mediated immunotherapy is a promising therapeutic option for multiple myeloma (MM). Gamma-delta T cells (gammadelta T cells) recognize phosphoantigens and display strong anti-tumour cytotoxicity. The synthetic agonist Phosphostim (bromohydrin pyrophosphate, BrHPP) has been shown to selectively activate Vgamma9Vdelta2 T cells. This study aimed to evaluate the expansion capacity and anti-myeloma cell cytotoxicity of circulating gammadelta T cells from MM patients at different time points throughout the disease, using Phosphostim and interleukin 2 (IL-2). Circulating gammadelta T cell counts in patients with newly diagnosed MM or in relapse did not differ from those in healthy donors. A 14-d culture of peripheral blood mononuclear cells with Phosphostim and IL-2 triggered a 100-fold expansion of gammadelta T cells in 78% of newly diagnosed patients. Gammadelta T cells harvested at the time of haematopoietic progenitor collection or in relapsing patients expanded less efficiently. Expanded gammadelta T cells killed 13/14 myeloma cell lines as well as primary myeloma cells, but not normal CD34 cells. Their killing efficiency was not affected by 2-d IL-2 starvation. This study demonstrated the ability of Phosphostim and IL-2 to expand gammadelta T cells from MM patients, and the efficient and stable killing of human myeloma cells by gd T cells.

Targeting therapy for breast carcinoma by ATP synthase inhibitor aurovertin B

Targeting of tumor tissues is one of the most powerful approaches to accelerate the efficiency of anticancer treatments. The investigation of effective targets, including proteins specifically and abundantly expressed in abnormal regions, has been one of the most important research topics in cancer therapy. In this study, we performed a proteomic analysis on human breast carcinoma tissues to investigate the tumor-specific protein expression in breast carcinoma. Our study showed that ATP synthase was up-regulated in tumor tissues and was present on the plasma membrane of breast cancer cells. Furthermore, we treated the breast cancer cells with ATP synthase inhibitors and examined the inhibitory efficiency. Aurovertin B, an ATP synthase inhibitor, has strong inhibition on the proliferation of several breast cancer cell lines, but little influence on the normal cell line MCF-10A. Aurovertin B inhibits proliferation of breast cancer cells by inducing apoptosis and arresting cell cycle at the G0/G1 phase. This study showed aurovertin B can be used as an antitumorigenic agent and may be exploited in cancer chemotherapy.

Nucleotide- and nucleoside-converting ectoenzymes: Important modulators of purinergic signalling cascade

The involvement of extracellular nucleotides and adenosine in an array of cell-specific responses has long been known and appreciated, but the integrative view of purinergic signalling as a multistep coordinated cascade has emerged recently. Current models of nucleotide turnover include: (i) transient release of nanomolar concentrations of ATP and ADP; (ii) triggering of signalling events via a series of ligand-gated (P2X) and metabotropic (P2Y) receptors; (iii) nucleotide breakdown by membrane-bound and soluble nucleotidases, including the enzymes of ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase) family, ecto-nucleotide pyrophosphatase/phosphodiesterase (E-NPP) family, ecto-5'-nucleotidase/CD73, and alkaline phosphatases; (iv) interaction of the resulting adenosine with own nucleoside-selective receptors; and finally, (v) extracellular adenosine inactivation via adenosine deaminase and purine nucleoside phosphorylase reactions and/or nucleoside uptake by the cells. In contrast to traditional paradigms that focus on purine-inactivating mechanisms, it has now become clear that "classical" intracellular ATP-regenerating enzymes, adenylate kinase, nucleoside diphosphate (NDP) kinase and ATP synthase can also be co-expressed on the cell surface. Furthermore, data on the ability of various cells to retain micromolar ATP levels in their pericellular space, as well as to release other related compounds (adenosine, UTP, dinucleotide polyphosphates and nucleotide sugars) gain another important insight into our understanding of mechanisms regulating a signalling cascade. This review summarizes recent advances in this rapidly evolving field, with particular emphasis on the nucleotide-releasing and purine-converting pathways in the vasculature.

The structure and function of mitochondrial F1F0-ATP synthases

We review recent advances in understanding of the structure of the F(1)F(0)-ATP synthase of the mitochondrial inner membrane (mtATPase). A significant achievement has been the determination of the structure of the principal peripheral or stator stalk components bringing us closer to achieving the Holy Grail of a complete 3D structure for the complex. A major focus of the field in recent years has been to understand the physiological significance of dimers or other oligomer forms of mtATPase recoverable from membranes and their relationship to the structure of the cristae of the inner mitochondrial membrane. In addition, the association of mtATPase with other membrane proteins has been described and suggests that further levels of functional organization need to be considered. Many reports in recent years have concerned the location and function of ATP synthase complexes or its component subunits on the external surface of the plasma membrane. We consider whether the evidence supports complete complexes being located on the cell surface, the biogenesis of such complexes, and aspects of function especially related to the structure of mtATPase.

Ecto-F1-ATPase and MHC-class I close association on cell membranes

Subunits of the mitochondrial ATP synthase complex are expressed on the surface of tumors, bind the TCR of human Vgamma9/Vdelta2 lymphocytes and promote their cytotoxicity. Present experiments show that detection of the complex (called ecto-F1-ATPase) at the cell surface by immunofluorescence correlates with low MHC-class I antigen expression. Strikingly, the alpha and beta chains of ecto-F1-ATPase are detected in membrane protein precipitates from immunofluorescence-negative cells, suggesting that ATPase epitopes are masked. Removal of beta2-microglobulin by mild acid treatment so that most surface MHC-I molecules become free heavy chains reveals F1-ATPase epitopes on MHC-I+ cell lines. Ecto-F1-ATPase is detected by immunofluorescence on primary fibroblasts which express moderate levels of MHC-I antigens. Up-regulation of MHC-I on these cells following IFN-gamma and/or TNF-alpha treatment induces a dose-dependent disappearance of F1-ATPase epitopes. Finally, biotinylated F1-ATPase cell surface components co-immunoprecipitate with MHC-I molecules confirming the association of both complexes on Raji cells. Confocal microscopy analysis of MHC-I and ecto-F1-ATPase beta chain expression on HepG2 cells shows a co-localization of both complexes in punctate membrane domains. This demonstrates that the TCR target F1-ATPase is in close contact with MHC-I antigens which are known to control Vgamma9/Vdelta2 T cell activity through binding to natural killer inhibitory receptors.

Innate immune functions of human gammadelta T cells

gammadelta T cells expressing the Vgamma9Vdelta2 T cell receptor (TCR) account for 1-10% of CD3(+) peripheral blood T lymphocytes. Vgamma9Vdelta2 T cells use their TCR as a pattern recognition receptor to sense the presence of infection through specific recognition of intermediates of the microbial non-mevalonate pathway of isoprenoid biosynthesis. Such phosphoantigens rapidly and selectively activate human gammadelta T cells to produce proinflammatory cytokines, notably interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha). In addition, human gammadelta T cells express certain Toll-like receptors (TLR) and directly respond to the corresponding ligands. We have demonstrated expression of TLR3 in Vgamma9Vdelta2 T cells and striking costimulatory effects of the ligand polyinosinic-polycytidylic acid (polyI:C) on TCR-stimulated IFN-gamma production. Gene expression studies by microarray analysis identified additional genes that were up-regulated by combined TCR- and TLR3 stimulation. We discuss these findings in the context of the suspected role of human Vgamma9Vdelta2 T cells as a link between innate and adaptive immune responses.

Bisphosphonates in cancer therapy

Bisphosphonates are the standard of care in the treatment of malignant bone diseases, because of their ability to inhibit osteoclast-mediated bone destruction. We review here preclinical evidence that bisphosphonates also exert direct antitumour effects and antiangiogenic properties. Furthermore, we describe new insights on how bisphosphonates may act synergistically in combination with antineoplastic drugs or gammadelta T cells to exhibit antitumour activity. These findings reveal new exciting possibilities to fully exploit the antitumour potential of bisphosphonates in the clinical practice.

Lysis of a broad range of epithelial tumour cells by human gamma delta T cells: involvement of NKG2D ligands and T-cell receptor- versus NKG2D-dependent recognition

Human gammadelta T cells expressing a V gamma 9V delta 2 T-cell receptor (TCR) kill various tumour cells including autologous tumours. In addition to TCR-dependent recognition, activation of NKG2D-positive gammadelta T cells by tumour cell-expressed NKG2D ligands can also trigger cytotoxic effector function. In this study, we investigated the involvement of TCR versus NKG2D in tumour cell recognition as a prerequisite to identify tumour types suitable for gammadelta T-cell-based immunotherapy. We have characterized epithelial tumour cells of different origin with respect to cell surface expression of the known NKG2D ligands MHC class I-chain-related antigens (MIC) A/B and UL16-binding proteins (ULBP), and susceptibility to gammadelta T-cell killing. Most tumour cells expressed comparable levels of MICA and MICB as well as ULBP with the exception of ULBP-1 which was absent or only weakly expressed. Most epithelial tumours were susceptible to allogeneic gammadelta T-cell lysis and in the case of an established ovarian carcinoma to autologous gammadelta T-cell killing. Lysis of resistant cells was enhanced by pre-treatment of tumour cells with aminobisphosphonates or pre-activation of gammadelta T cells with phosphoantigens. A potential involvement of TCR and/or NKG2D was investigated by antibody blockade. These experiments revealed three patterns of inhibition, i.e. preferential inhibition by anti-TCR antibody, preferential inhibition by anti-NKG2D antibody, or additive blockade by anti-TCR plus anti-NKG2D antibodies. Our results indicate for the first time that the NKG2D pathway is involved in the lysis of different melanomas, pancreatic adenocarcinomas, squamous cell carcinomas of the head and neck, and lung carcinoma.

Germ-line and rearranged Tcrd transcription distinguish bona fide NK cells and NK-like gammadelta T cells

NK cells and gammadelta T cells are distinct subsets of lymphocytes that contextually share multiple phenotypic and functional characteristics. However, the acquisition and the extent of these similarities remain poorly understood. Here, using T cell receptor delta locus-histone 2B-enhanced GFP (Tcrd-H2BEGFP) reporter mice, we show that germ-line transcription of Tcrd occurs in all maturing NK cells. We also describe a population of mouse NK-like cells that are indistinguishable from "bona fide" NK cells using standard protocols. Requirements for V(D)J recombination and a functional thymus, along with very low-level expression of surface TCRgammadelta but high intracellular CD3, define these cells as gammadelta T cells. "NK-like gammadelta T cells" are CD127+, have a memory-activated phenotype, express multiple NK cell receptors and readily produce interferon-gamma in response to IL-12/IL-18 stimulation. The close phenotypic resemblance between NK cells and NK-like gammadelta T cells is a source of experimental ambiguity in studies bridging NK and T cell biology, such as those on thymic NK cell development. Instead, it ascribes chronic TCRgammadelta engagement as a means of acquiring NK-like function.

Human gamma delta T cells: candidates for the development of immunotherapeutic strategies

A numerically small subset of human T lymphocytes expresses a gamma delta T cell receptor (TCR). These gamma delta T cells share certain effector functions with alpha beta T cells as well as with NK cells and NKT cells. The major peripheral blood gamma delta T cell subset in healthy adults expresses a Vgamma9Vdelta2 TCR, which recognizes small phosphorylated metabolites referred to as phosphoantigens. Vdelta1 gamma delta T cells mainly occur in the intestine. They recognize the stress-induced MICA/B and CD1c. Furthermore, gamma delta T cells express a variety of NK cell and pattern-recognition receptors which are responsible for the "fine-tuning" of effector functions. In recent years, gamma delta T cells start to emerge as a rewarding target for immunotherapeutic strategies against viral infections and cancer. A better understanding of factors that modulate gamma gamma delta T cell function will further eluminate the potential of these cells.

Identification and isolation of Brucella suis virulence genes involved in resistance to the human innate immune system

Brucella strains are facultative intracellular pathogens that induce chronic diseases in humans and animals. This observation implies that Brucella subverts innate and specific immune responses of the host to develop its full virulence. Deciphering the genes involved in the subversion of the immune system is of primary importance for understanding the virulence of the bacteria, for understanding the pathogenic consequences of infection, and for designing an efficient vaccine. We have developed an in vitro system involving human macrophages infected by Brucella suis and activated syngeneic gamma9delta2 T lymphocytes. Under these conditions, multiplication of B. suis inside macrophages is only slightly reduced. To identify the genes responsible for this reduced sensitivity, we screened a library of 2,000 clones of transposon-mutated B. suis. For rapid and quantitative analysis of the multiplication of the bacteria, we describe a simple method based on Alamar blue reduction, which is compatible with screening a large library. By comparing multiplication inside macrophages alone and multiplication inside macrophages with activated gamma9delta2 T cells, we identified four genes of B. suis that were necessary to resist to the action of the gamma9delta2 T cells. The putative functions of these genes are discussed in order to propose possible explanations for understanding their exact role in the subversion of innate immunity.

Large scale expansion of gamma 9 delta 2 T lymphocytes: Innacell gamma delta cell therapy product

gamma9delta2 T lymphocytes are non-conventional lymphocytes presenting a direct cytotoxic effect against a broad range of tumour targets. These cells also secrete inflammatory cytokines that can boost the other components of the immune system. In contrast to conventional CD8(+) T cells, the cytotoxic effect of gamma9delta2 T lymphocytes does not depend on the expression of major histocompatibility complex molecules by target tumour cells. INNACELL gammadeltatrade mark is a cell therapy product obtained by ex vivo amplification of mononuclear cells. The stimulation is achieved by a specific synthetic agonist of gamma9delta2 T lymphocytes, bromohydrin pyrophosphate (BrHPP). After a single stimulation with BrHPP, gamma9delta2 T lymphocytes are expanded for 2 weeks in a closed system in culture medium with interleukin-2 (IL-2). On day 15, cells are washed and harvested in 4% human serum albumin. In this manufacturing process, the total cell population is expanded by approximately 10-fold and gamma9delta2 T lymphocytes undergo a specific 1000-fold expansion, corresponding to a gamma9delta2 T lymphocyte enrichment of more than 70% at the end of the culture. This manufacturing process is much simpler than most current cellular therapy approaches using conventional CD8(+) T-cell lines or clones: there is no final or initial separation, no purification step and no use of feeder cells; the specific T-cell receptor-mediated signal provided by BrHPP is sufficient to trigger the IL-2-dependent expansion of the gamma9delta2 subset, which then becomes predominant in the cell culture in large amounts.

Targeting human {gamma}delta} T cells with zoledronate and interleukin-2 for immunotherapy of hormone-refractory prostate cancer

The increasing evidence that gammadelta T cells have potent antitumor activity suggests their value in immunotherapy, particularly in areas of unmet need such as metastatic carcinoma. To this end, we initiated a phase I clinical trial in metastatic hormone-refractory prostate cancer to examine the feasibility and consequences of using the gammadelta T-cell agonist zoledronate, either alone or in combination with low-dose interleukin 2 (IL-2), to activate peripheral blood gammadelta cells. Nine patients were enlisted to each arm. Neither treatment showed appreciable toxicity. Most patients were treated with zoledronate + IL-2, but conversely only two treated with zoledronate displayed a significant long-term shift of peripheral gammadelta cells toward an activated effector-memory-like state (T(EM)), producing IFN-gamma and perforin. These patients also maintained serum levels of tumor necrosis factor-related apoptosis inducing ligand (TRAIL), consistent with a parallel microarray analysis showing that TRAIL is produced by gammadelta cells activated via the T-cell receptor and IL-2. Moreover, the numbers of T(EM) gammadelta cells showed a statistically significant correlation with declining prostate-specific antigen levels and objective clinical outcomes that comprised three instances of partial remission and five of stable disease. By contrast, most patients treated only with zoledronate failed to sustain either gammadelta cell numbers or serum TRAIL, and showed progressive clinical deterioration. Thus, zoledronate + IL-2 represents a novel, safe, and feasible approach to induce immunologic and clinical responses in patients with metastatic carcinomas, potentially providing a substantially increased window for specific approaches to be administered. Moreover, gammadelta cell phenotypes and possibly serum TRAIL may constitute novel biomarkers of prognosis upon therapy with zoledronate + IL-2 in metastatic carcinoma.