Synthetic Phosphoantigens Enhance Human Vγ9Vδ2 T Lymphocytes Killing of Non-Hodgkin’s B Lymphoma

γδ T cells in hematological malignancies: mechanisms and therapeutic strategies

γδ T cells are a unique subset of lymphocytes with both innate and adaptive features. They recognize and eradicate various hematological malignancies through different mechanisms, employing factors including γδ TCR, NKR, NKG2D, TRAIL, and perforin/granzyme. They also modulate other immune cells to enhance their antitumor activity. Moreover, γδ T cells have potent antiviral functions after hematopoietic stem cell transplantation (HSCT), which may improve the outcome of patients with hematological malignancies. In this review, we summarize the current knowledge on γδ T cell biology and function in hematological malignancies and HSCT complications. We also discuss the challenges and limitations of the clinical application of γδ T cells, such as their low frequency in peripheral blood and heterogeneity among different subsets. We then highlight some promising strategies for γδ T cell-based therapy, such as using agonist antibodies, cell engagers, or genetic modification technology. Furthermore, we review the recent clinical trials evaluating the safety and efficacy of γδ T-cell therapy in different hematological malignancies. In conclusion, γδ T cells represent a promising immunotherapeutic tool for hematological malignancies that deserves further exploration.

Adoptive Cell Therapy for T-Cell Malignancies

T-cell malignancies are often aggressive and associated with poor prognoses. Adoptive cell therapy has recently shown promise as a new line of therapy for patients with hematological malignancies. However, there are currently challenges in applying adoptive cell therapy to T-cell malignancies. Various approaches have been examined in preclinical and clinical studies to overcome these obstacles. This review aims to provide an overview of the recent progress on adoptive cell therapy for T-cell malignancies. The benefits and drawbacks of different types of adoptive cell therapy are discussed. The potential advantages and current applications of innate immune cell-based adoptive cell therapy for T cell malignancies are emphasized.

The Diverse Roles of γδ T Cells in Cancer: From Rapid Immunity to Aggressive Lymphoma

γδ T cells are unique players in shaping immune responses, lying at the intersection between innate and adaptive immunity. Unlike conventional αβ T cells, γδ T cells largely populate non-lymphoid peripheral tissues, demonstrating tissue specificity, and they respond to ligands in an MHC-independent manner. γδ T cells display rapid activation and effector functions, with a capacity for cytotoxic anti-tumour responses and production of inflammatory cytokines such as IFN-γ or IL-17. Their rapid cytotoxic nature makes them attractive cells for use in anti-cancer immunotherapies. However, upon transformation, γδ T cells can give rise to highly aggressive lymphomas. These rare malignancies often display poor patient survival, and no curative therapies exist. In this review, we discuss the diverse roles of γδ T cells in immune surveillance and response, with a particular focus on cancer immunity. We summarise the intriguing dichotomy between pro- and anti-tumour functions of γδ T cells in solid and haematological cancers, highlighting the key subsets involved. Finally, we discuss potential drivers of γδ T-cell transformation, summarising the main γδ T-cell lymphoma/leukaemia entities, their clinical features, recent advances in mapping their molecular and genomic landscapes, current treatment strategies and potential future targeting options.

Boosting γδ T cell-mediated antibody-dependent cellular cytotoxicity by PD-1 blockade in follicular lymphoma

Follicular lymphoma (FL) is a common non Hodgkin's lymphoma subtype in which immune escape mechanisms are implicated in resistance to chemo-immunotherapy. Although molecular studies point to qualitative and quantitative deregulation of immune checkpoints, in depth cellular analysis of FL immune escape is lacking. Here, by functional assays and in silico analyses we show that a subset of FL patients displays a 'high' immune escape phenotype. These FL cases are characterized by abundant infiltration of PD1⁺ CD16⁺ TCRVγ9Vδ2 γδ T lymphocytes. In a 3D co-culture assay (MALC), γδ T cells mediate both direct and indirect (ADCC in the presence of anti-CD20 mAbs) cytolytic activity against FL cell aggregates. Importantly, PD-1, which is expressed by most FL-infiltrating γδ T lymphocytes with ADCC capacity, impairs these functions. In conclusion, we identify a PD1-regulated γδ T cell cytolytic immune component in FL. Our data provide a treatment rational by PD-1 blockade aimed at boosting γδ T cell anti-tumor functions in FL.

Cytokine-mediated activation of human ex vivo-expanded Vγ9Vδ2 T cells

Vγ9Vδ2 T cells, the major subset of the human peripheral blood γδ T-cell, respond to microbial infection and stressed cells through the recognition of phosphoantigens. In contrast to the growing knowledge of antigen-mediated activation mechanisms, the antigen-independent and cytokine-mediated activation mechanisms of Vγ9Vδ2 T cells are poorly understood. Here, we show that interleukin (IL) -12 and IL-18 synergize to activate human ex vivo-expanded Vγ9Vδ2 T cells. Vγ9Vδ2 T cells treated with IL-12 and IL-18 enhanced effector functions, including the expression of IFN-γ and granzyme B, and cytotoxicity. These enhanced effector responses following IL-12 and IL-18 treatment were associated with homotypic aggregation, enhanced expression of ICAM-1 and decreased expression of the B- and T-lymphocyte attenuator (BTLA), a co-inhibitory receptor. IL-12 and IL-18 also induced the antigen-independent proliferation of Vγ9Vδ2 T cells. Increased expression of IκBζ, IL-12Rβ2 and IL-18Rα following IL-12 and IL-18 stimulation resulted in sustained activation of STAT4 and NF-κB. The enhanced production of IFN-γ and cytotoxic activity are critical for cancer immunotherapy using Vγ9Vδ2 T cells. Thus, the combined treatment of ex vivo-expanded Vγ9Vδ2 T cells with IL-12 and IL-18 may serve as a new strategy for the therapeutic activation of these cells.

Decitabine Inhibits Gamma Delta T Cell Cytotoxicity by Promoting KIR2DL2/3 Expression

Gamma delta (γδ) T cells, which possess potent cytotoxicity against a wide range of cancer cells, have become a potential avenue for adoptive immunotherapy. Decitabine (DAC) has been reported to enhance the immunogenicity of tumor cells, thereby reinstating endogenous immune recognition and tumor lysis. However, DAC has also been demonstrated to have direct effects on immune cells. In this study, we report that DAC inhibits γδ T cell proliferation. In addition, DAC increases the number of KIR2DL2/3-positive γδ T cells, which are less cytotoxic than the KIR2DL2/3-negative γδ T cells. We found that DAC upregulated KIR2DL2/3 expression in KIR2DL2/3-negative γδ T cells by inhibiting KIR2DL2/3 promoter methylation, which enhances the binding of KIR2DL2/3 promoter to Sp-1 and activates KIR2DL2/3 gene expression. Our data demonstrated that DAC can inhibit the function of human γδ T cells at both cellular and molecular levels, which confirms and extrapolates the results of previous studies showing that DAC can negatively regulate the function of NK cells and αβ T cells of the immune system.

A bispecific nanobody approach to leverage the potent and widely applicable tumor cytolytic capacity of Vγ9Vδ2-T cells

Though Vγ9Vδ2-T cells constitute only a small fraction of the total T cell population in human peripheral blood, they play a vital role in tumor defense and are therefore of major interest to explore for cancer immunotherapy. Vγ9Vδ2-T cell-based cancer immunotherapeutic approaches developed so far have been generally well tolerated and were able to induce significant clinical responses. However, overall results were inconsistent, possibly due to the fact that these strategies induced systemic activation of Vγ9Vδ2-T cells without preferential accumulation and targeted activation in the tumor. Here we show that a novel bispecific nanobody-based construct targeting both Vγ9Vδ2-T cells and EGFR induced potent Vγ9Vδ2-T cell activation and subsequent tumor cell lysis both in vitro and in an in vivo mouse xenograft model. Tumor cell lysis was independent of KRAS and BRAF tumor mutation status and common Vγ9Vδ2-T cell receptor sequence variations. In combination with the conserved monomorphic nature of the Vγ9Vδ2-TCR and the facile replacement of the tumor-specific nanobody, this immunotherapeutic approach can be applied to a large group of cancer patients.

Prevention of Vγ9Vδ2 T Cell Activation by a Vγ9Vδ2 TCR Nanobody

Vγ9Vδ2 T cell activation plays an important role in antitumor and antimicrobial immune responses. However, there are conditions in which Vγ9Vδ2 T cell activation can be considered inappropriate for the host. Patients treated with aminobisphosphonates for hypercalcemia or metastatic bone disease often present with a debilitating acute phase response as a result of Vγ9Vδ2 T cell activation. To date, no agents are available that can clinically inhibit Vγ9Vδ2 T cell activation. In this study, we describe the identification of a single domain Ab fragment directed to the TCR of Vγ9Vδ2 T cells with neutralizing properties. This variable domain of an H chain-only Ab (VHH or nanobody) significantly inhibited both phosphoantigen-dependent and -independent activation of Vγ9Vδ2 T cells and, importantly, strongly reduced the production of inflammatory cytokines upon stimulation with aminobisphosphonate-treated cells. Additionally, in silico modeling suggests that the neutralizing VHH binds the same residues on the Vγ9Vδ2 TCR as the Vγ9Vδ2 T cell Ag-presenting transmembrane protein butyrophilin 3A1, providing information on critical residues involved in this interaction. The neutralizing Vγ9Vδ2 TCR VHH identified in this study might provide a novel approach to inhibit the unintentional Vγ9Vδ2 T cell activation as a consequence of aminobisphosphonate administration.

Highly specific and potently activating Vγ9Vδ2-T cell specific nanobodies for diagnostic and therapeutic applications

Vγ9Vδ2-T cells constitute the predominant subset of γδ-T cells in human peripheral blood and have been shown to play an important role in antimicrobial and antitumor immune responses. Several efforts have been initiated to exploit these cells for cancer immunotherapy, e.g. by using phosphoantigens, adoptive cell transfer, and by a bispecific monoclonal antibody based approach. Here, we report the generation of a novel set of Vγ9Vδ2-T cell specific VHH (or nanobody). VHH have several advantages compared to conventional antibodies related to their small size, stability, ease of generating multispecific molecules and low immunogenicity. With high specificity and affinity, the anti-Vγ9Vδ2-T cell receptor VHHs are shown to be useful for FACS, MACS and immunocytochemistry. In addition, some VHH were found to specifically activate Vγ9Vδ2-T cells. Besides being of possible immunotherapeutic value, these single domain antibodies will be of great value in the further study of this important immune effector cell subset.

Programmed death 1 and B and T lymphocyte attenuator immunoreceptors and their association with malignant T-lymphoproliferative disorders: brief review

Malignant T-cell lymphoproliferative diseases are relatively rare. T cells are activated through the T-cell receptor with the aid of costimulating molecules that can be either excitatory or inhibitory. Such pathways have been also implicated in mechanisms of malignant T-cell lymphoproliferative diseases' persistence and relapse by circumventing immune responses. To date, three major immunoinhibitory molecules have been recognized, namely programmed cell death-1 (PD-1), B and T lymphocyte attenuator (BTLA) and cytotoxic T lymphocyte antigen 4 (CTLA-4). Although CTLA-4 is considered the 'gatekeeper' of immune tolerance, PD-1 negatively regulates immune responses broadly, whereas BTLA activation has been shown to inhibit CD8+ cancer-specific T cells. Both PD-1 and BTLA downregulate proximal T-cell receptor signalling cascade and are involved in immune evasion of leukaemias and lymphomas, even after allogeneic stem cell transplantation. These immunoregulatory molecules can have seemingly a synergistic effect on weakening the immune response of patients with haematological malignancies, and their manipulation represents a very active field of preclinical as well as clinical interest.

Human farnesyl pyrophosphate synthase inhibition by nitrogen bisphosphonates: a 3D-QSAR study

We report the results of a comparative molecular field analysis and comparative molecular similarity index analysis of the human farnesyl pyrophosphate synthase (FPPS) inhibition by nitrogen bisphosphonates (NBPs) taking into account their time-dependent inhibition efficacies. The 3D-QSAR models obtained provide steric, electrostatic and hydrophobic contour maps consistent with the interactions into the active site of human FPPS observed in available crystallographic structures. Furthermore, the 3D-QSAR models obtained provide accurately IC50 values of the NBPs of the training set. The predictive ability of these 3D-QSAR models was found to rely on the choice of biologically active conformations of the target molecules and on a careful examination of the protonation status of the NBPs in the training set. The best models obtained can be useful to predict biological values of a high number of NBPs that have been used for the treatment of different diseases as potential inhibitors of the activity of the FPPS enzyme.

What lessons can be learned from γδ T cell-based cancer immunotherapy trials?

During the last several years, research has produced a significant amount of knowledge concerning the characteristics of human γδ T lymphocytes. Findings regarding the immune functions of these cells, particularly their natural killer cell-like lytic activity against tumor cells, have raised expectations for the therapeutic applications of these cells for cancer. Pharmaceutical companies have produced selective agonists for these lymphocytes, and several teams have launched clinical trials of γδ T cell-based cancer therapies. The findings from these studies include hematological malignancies (follicular lymphoma, multiple myeloma, acute and chronic myeloid leukemia), as well as solid tumors (renal cell, breast and prostate carcinomas), consisting of samples from more than 250 patients from Europe, Japan and the United States. The results of these pioneering studies are now available, and this short review summarizes the lessons learned and the role of γδ T cell-based strategies in the current landscape of cancer immunotherapies.

The gene expression profile of phosphoantigen-specific human γδ T lymphocytes is a blend of αβ T-cell and NK-cell signatures

Global transcriptional technologies have revolutionised the study of lymphoid cell populations, but human γδ T lymphocytes specific for phosphoantigens remain far less deeply characterised by these methods despite the great therapeutic potential of these cells. Here we analyse the transcriptome of circulating TCRVγ(+) γδ T cells isolated from healthy individuals, and their relation with those from other lymphoid cell subsets. We report that the gene signature of phosphoantigen-specific TCRVγ(+) γδ T cells is a hybrid of those from αβ T and NK cells, with more 'NK-cell' genes than αβ T cells have and more 'T-cell' genes than NK cells. The expression profile of TCRVγ(+) γδ T cells stimulated with phosphoantigen recapitulates their immediate physiological functions: Th1 cytokine, chemokine and cytotoxic activities reflect their high mitotic activity at later time points and do not indicate antigen-presenting functions. Finally, such hallmarks make the transcriptome of γδ T cells, whether resting or clonally expanding, clearly distinctive from that of NK/T or peripheral T-cell lymphomas of the γδ subtype.

Bromohydrin pyrophosphate-stimulated Vgamma9delta2 T cells expanded ex vivo from patients with poor-prognosis neuroblastoma lyse autologous primary tumor cells

Gamma/delta T cells (Vgamma9delta2) contribute to innate immunity and exert natural cytotoxicity against a variety of tumors. Using a synthetic phosphoantigen (Bromohydrin Pyrophosphate, BrHPP), we amplified Vgamma9delta2 T cells in vitro from neuroblastoma patients. In the presence of BrHPP and low doses of IL-2, robust proliferation of Vgamma9delta2 T cells was obtained from peripheral blood mononuclear cells (PBMC) harvested at diagnosis. Moderate proliferation was observed from PBMC harvested after stem cell transplantation, whereas modest levels of Vgamma9delta2 T cells were obtained from PBMC harvested after induction therapy. Proliferation was observed after a single in vitro stimulation with BrHPP. After 21 days in culture, Vgamma9delta2 T cells represented more than 80% of cultured cells (a 50-fold expansion from baseline). Moreover, BrHPP-amplified Vgamma9delta2 T cells from patients-expressed activation markers and were able to lyse allogeneic and autologous neuroblasts. This cytotoxic activity was gammadelta T-cell receptor-dependent. Clinical trials using BrHPP are warranted in patients with poor-prognosis neuroblastoma, either to expand patient-derived Vgamma9delta2 T cells ex vivo or by direct administration to in vivo to boost the pool of resident Vgamma9delta2 T cells in vivo.

Histamine modulates γδ-T lymphocyte migration and cytotoxicity, via Gi and Gs protein-coupled signalling pathways

BACKGROUND AND PURPOSE

The biogenic amine, histamine plays a pathophysiological regulatory role in cellular processes of a variety of immune cells. This work analyses the actions of histamine on γδ-T lymphocytes, isolated from human peripheral blood, which are critically involved in immunological surveillance of tumours.

EXPERIMENTAL APPROACH

We have analysed effects of histamine on the intracellular calcium, actin reorganization, migratory response and the interaction of human γδ T cells with tumour cells such as the A2058 human melanoma cell line, the human Burkitt's Non-Hodgkin lymphoma cell line Raji, the T-lymphoblastic lymphoma cell line Jurkat and the natural killer cell-sensitive erythroleukaemia cell line, K562.

KEY RESULTS

γδ T lymphocytes express mRNA for different histamine receptor subtypes. In human peripheral blood γδ T cells, histamine stimulated Pertussis toxin-sensitive intracellular calcium increase, actin polymerization and chemotaxis. However, histamine inhibited the spontaneous cytolytic activity of γδ T cells towards several tumour cell lines in a cholera toxin-sensitive manner. A histamine H(4) receptor antagonist abolished the histamine induced γδ T cell migratory response. A histamine H(2) receptor agonist inhibited γδ T cell-mediated cytotoxicity.

CONCLUSIONS AND IMPLICATIONS

Histamine activated signalling pathways typical of chemotaxis (G(i) protein-dependent actin reorganization, increase of intracellular calcium) and induced migratory responses in γδ T lymphocytes, via the H(4) receptor, whereas it down-regulated γδ T cell mediated cytotoxicity through H(2) receptors and G(s) protein-coupled signalling. Our data suggest that histamine activated γδ T cells could modulate immunological surveillance of tumour tissue.

Adoptively transferred ex vivo expanded gammadelta-T cells mediate in vivo antitumor activity in preclinical mouse models of breast cancer

In contrast to antigen-specific alphabeta-T cells (adaptive immune system), gammadelta-T cells can recognize and lyse malignantly transformed cells almost immediately upon encounter in a manner that does not require the recognition of tumor-specific antigens (innate immune system). Given the well-documented capacity of gammadelta-T cells to innately kill a variety of malignant cells, efforts are now actively underway to exploit the antitumor properties of gammadelta-T cells for clinical purposes. Here, we present for the first time preclinical in vivo mouse models of gammadelta-T cell-based immunotherapy directed against breast cancer. These studies were explicitly designed to approximate clinical situations in which adoptively transferred gammadelta-T cells would be employed therapeutically against breast cancer. Using radioisotope-labeled gammadelta-T cells, we first show that adoptively transferred gammadelta-T cells localize to breast tumors in a mouse model (4T1 mammary adenocarcinoma) of human breast cancer. Moreover, by using an antibody directed against the gammadelta-T cell receptor (TCR), we determined that localization of adoptively transferred gammadelta-T cells to tumor is a TCR-dependant process. Additionally, biodistribution studies revealed that adoptively transferred gammadelta-T cells traffic differently in tumor-bearing mice compared to healthy mice with fewer gammadelta-T cells localizing into the spleens of tumor-bearing mice. Finally, in both syngeneic (4T1) and xenogeneic (2Lmp) models of breast cancer, we demonstrate that adoptively transferred gammadelta-T cells are both effective against breast cancer and are otherwise well-tolerated by treated animals. These findings provide a strong preclinical rationale for using ex vivo expanded adoptively transferred gammadelta-T cells as a form of cell-based immunotherapy for the treatment of breast cancer. Additionally, these studies establish that clinically applicable methods for radiolabeling gammadelta-T cells allows for the tracking of adoptively transferred gammadelta-T cells in tumor-bearing hosts.

Antitumor activity of gammadelta T cells reactive against cytomegalovirus-infected cells in a mouse xenograft tumor model

gammadelta T cells recognize stress-induced autoantigens and contribute to immunity against infections and cancer. Our previous study revealed that Vdelta2-negative ((neg)) gammadelta T lymphocytes isolated from transplant recipients infected by cytomegalovirus (CMV) killed both CMV-infected cells and HT29 colon cancer cells in vitro. To investigate the antitumor effects of Vdelta2(neg) clones in vivo, we generated hypodermal HT29 tumors in immunodeficient mice. Concomitant injections of Vdelta2(neg)clones, in contrast to Vdelta2(+) cells, prevented the development of HT29 tumors. Vdelta2(neg) clones expressed chemokine C-C motif receptor 3 (CCR3) and migrated in vitro in response to chemokines secreted by HT29 cells, among which were the CCR3 ligands macrophage inflammatory protein-1delta and monocyte chemoattractant protein-4. More importantly, a systemic i.p. treatment with Vdelta2(neg) clones delayed the growth of HT29 s.c. tumors. The effect of in vivo gammadelta T-cell passive immunotherapy on tumor growth could be reverted by addition of a blocking anti-CCR3 antibody. gammadelta T-cell passive immunotherapy was dependent on the cytotoxic activity of the gammadelta effectors toward their targets because Vdelta2(neg) clones were not able to inhibit the growth of A431 hypodermal tumors. Our findings suggest that CMV-specific Vdelta2(neg) cells could target in vivo cancer cells, making them an attractive candidate for antitumor immunotherapy.

Phase-I study of Innacell gammadelta, an autologous cell-therapy product highly enriched in gamma9delta2 T lymphocytes, in combination with IL-2, in patients with metastatic renal cell carcinoma

PURPOSE

gamma9delta2 T lymphocytes have been shown to be directly cytotoxic against renal carcinoma cells. Lymphocytes T gammadelta can be selectively expanded in vivo with BrHPP (IPH1101, Phosphostim) and interleukin 2 (IL-2). A phase I Study was conducted in patients with metastatic renal cell carcinoma (mRCC) to determine the maximum-tolerated dose and safety of Innacell gammadelta, an autologous cell-therapy product based on gamma9delta2 T lymphocytes, in patients with mRCC.

EXPERIMENTAL DESIGN

A 1-h intravenous infusion of gamma9delta2 T lymphocytes was administered alone during treatment cycle 1 and combined with a low dose of subcutaneous interleukin-2 (IL-2, 2 MIU/m2 from Day 1 to Day 7) in the two subsequent cycles (at 3-week intervals). The dose of gamma9delta2 T lymphocytes was escalated from 1 up to 8 x 10(9) cells.

RESULTS

Ten patients underwent a total of 27 treatment cycles. Immunomonitoring data demonstrate that gamma9delta2 T lymphocytes are initially cleared from the blood to reappear at the end of IL-2 administration. Dose-limiting toxicity occurred in one patient at the dose of 8 x 10(9) cells (disseminated intravascular coagulation). Other treatment-related adverse events (AEs) included mainly gastrointestinal disorders and flu-like symptoms (fatigue, pyrexia, rigors). Hypotension and tachycardia also occurred, especially with co-administered IL-2. Six patients showed stabilized disease. Time to progression was 25.7 weeks.

CONCLUSION

The data collected in ten patients with mRCC indicate that repeated infusions of Innacell gammadelta at different dose levels (up to 8 x 10(9) total cells), either alone or with IL-2 is well tolerated. These results are in favor of the therapeutic value of cell therapy with Innacell gammadelta for the treatment of cancers.

Failure to restore the Vgamma2-Jgamma1.2 repertoire in HIV-infected men receiving highly active antiretroviral therapy (HAART)

Gammadelta (gammadelta) T cells expressing the Vgamma2-Jgamma1.2Vdelta2 (Vgamma9-JPVdelta2, alternate nomenclature) T cell receptor (TCR) constitute the major peripheral blood population of gammadelta T cells in adult humans and are specifically depleted during human immunodeficiency virus (HIV) disease. Vgamma2-Jgamma1.2Vdelta2 T cells provide a convenient model for assessing the impact of antiretroviral therapy on cell populations that are not susceptible to direct infection because they do not express CD4 and depletion occurs by indirect mechanisms. We obtained longitudinal PBMC samples from 16 HIV-infected individuals who enrolled in the Multicenter AIDS Cohort Study (MACS) and were starting highly active antiretroviral therapy (HAART). Vgamma2-Jgamma1.2Vdelta2 T cells were depleted in these individuals as a result of HIV infection. Despite evidence for clinical benefits of HAART, the Vgamma2-Jgamma1.2Vdelta2 T cell repertoire did not recover after HAART initiation irrespective of treatment duration. These studies highlight important defects among cell subsets lost due to indirect effects of HIV.

Impacts of HIV infection on Vgamma2Vdelta2 T cell phenotype and function: a mechanism for reduced tumor immunity in AIDS

HIV infection causes rapid and lasting defects in the population of Vgamma2Vdelta2 T cells. To fully describe the impact of HIV, we examined PBMC samples from HIV+ patients receiving highly active antiretroviral therapy, who had displayed prolonged viral control and CD4 counts above 300 cells/mm3. We observed lower frequencies of CD27-/CD45RA- Vgamma2Vdelta2 cells in HIV+ individuals when compared with controls, coupled with an increased proportion of CD45RA+ cells. These changes were common among 24 HIV+ patients and were not related to CD4 cell count or viral RNA burden. Vgamma2 cells from HIV+ individuals had lower expression of Granzyme B and displayed reduced cytotoxicity against Daudi targets after in vitro stimulation. There was increased expression of FasR (CD95) on Vgamma2 cells from HIV+ PBMC that may be a mechanism for depletion of Vgamma2 cells during disease. In addition to the well-characterized defects in the Vgamma2 repertoire and functional responses to phosphoantigen, the proportion of CD27-/CD45RA- Vgamma2Vdelta2 T cells after isopentenyl pyrophosphate stimulation was reduced sharply in HIV+ donors versus controls. Thus, HIV infection has multiple impacts on the circulating Vgamma2Vdelta2 T cell population that combine to reduce the potential effector activity in terms of tumor cytotoxicity. Changes in Vgamma2Vdelta2 T cells, along with concomitant effects on NK and NKT cells that also contribute to tumor surveillance, may be important factors for elevating the risk of malignancy during AIDS.

V gamma 9 V delta 2 T cell cytotoxicity against tumor cells is enhanced by monoclonal antibody drugs--rituximab and trastuzumab

V gamma 9 V delta 2 T cells exert potent cytotoxicity toward various tumor cells and adoptive transfer of V gamma 9 V delta 2 T cells is an attractive proposition for cell based immunotherapy. V gamma 9 V delta 2 T cells expanded in the presence of Zoledronate and IL-2 express CD16 (Fc gamma RIII), which raises the possibility that V gamma 9 V delta 2 T cells could be used in conjunction with tumor targeting monoclonal antibody drugs to increase antitumor cytotoxicity by antibody dependent cellular cytotoxicity (ADCC). Cytotoxic activity against CD20-positive B lineage lymphoma or chronic lymphocytic leukemia (CLL) and HER2-positive breast cancer cells was assessed in the presence of rituximab and trastuzumab, respectively. Cytotoxicity of V gamma 9 V delta 2 T cells against CD20-positive targets was higher when used in combination with rituximab. Similarly, V gamma 9 V delta 2 T cells used in combination with trastuzumab resulted in greater cytotoxicity against HER2-positive cells in comparison with either agent alone and this effect was restricted to the CD16(+)V gamma 9 V delta 2 T cell population. Our results show that CD16(+)V gamma 9 V delta 2 T cells recognize monoclonal antibody coated tumor cells via CD16 and exert ADCC similar to that observed with NK cells, even when target cells are relatively resistant to monoclonal antibodies or V gamma 9 V delta 2 T cells alone. Combination therapy involving ex vivo expanded CD16(+)V gamma 9 V delta 2 T cells and monoclonal antibodies may enhance the clinical outcomes for patients treated with monoclonal antibody therapy.

Peripheral blood gamma-delta T cells in advanced-stage cancer patients

Gamma-delta T (gammadelta T) cells form a subgroup which has been reported to play a role in both natural and acquired immunity. Their levels have been found to increase in some tumour tissues. The aim of this study was to investigate the ratio of gammadelta T cells to all T cells in the peripheral blood of advanced-stage cancer patients; the level of gammadelta T cells expressing the Vdelta2-T-cell receptor (TCR) chain; NKG2D receptor expression; and apoptotic (Annexin-V) gammadelta T-cell levels. Twenty patients with advanced-stage cancer and 13 healthy controls were included. No statistical differences were found between control and patient groups in terms of the gammadelta T/total T-cell ratio (P=0.53), the Vgamma2-TCR expressing gammadelta T-cell ratio (P=0.19) or the Annexin-V ratio (P=0.48). However, NKG2D expression in gammadelta T cells was significantly different between the control and patient groups (P=0.014). In summary it was shown that the levels of NKG2D receptors, which are responsible for the cytolytic effect of gammadelta T cells, were lower in cancer patients than in healthy adults. However, no significant differences were observed in the other parameters studied between groups.

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.

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.

Human γδ T lymphocytes strip and kill tumor cells simultaneously

When human gammadelta lymphocytes bind to tumor cells for killing, they also strip their membrane for unknown reasons. Here we investigated this topic using the model of human gammadelta lymphocytes co-incubated with anaplastic large cell lymphomas, a group of tumors with cytolytic T or null lineage. By using flow cytometry and live cell imaging, we show that as soon as both cells were in contact, the TCR-mediated activation of gammadelta lymphocytes simultaneously triggered their secretion of lytic granules and stripping of lymphoma cell membranes, and both activities continued even after their cell death. However reciprocally in such conjugates, resistant lymphoma failed to strip gammadelta cells and to kill them by untargeted secretion of their own lytic granules. This indicated that secretion of lytic granules and target membrane stripping are associated in lytic cell conjugates, and that gammadelta T lymphocytes strip and kill their targets simultaneously.

Nonpeptide antigens, presentation mechanisms, and immunological memory of human Vgamma2Vdelta2 T cells: discriminating friend from foe through the recognition of prenyl pyrophosphate antigens

Human Vgamma2Vdelta2 T cells play important roles in mediating immunity against microbial pathogens and have potent anti-tumor activity. Vgamma2Vdelta2 T cells recognize the pyrophosphorylated isoprenoid intermediates (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP), an intermediate in the foreign 2-C-methyl-d-erythritol 4-phosphate (MEP) pathway, and isopentenyl pyrophosphate (IPP), an intermediate in the self-mevalonate pathway. Infection with bacteria and protozoa using the MEP pathway leads to the rapid expansion of Vgamma2Vdelta2 T cells to very high numbers through preferential recognition of HMBPP. Activated Vgamma2Vdelta2 T cells produce proinflammatory cytokines and chemokines, kill infected cells, secrete growth factors for epithelial cells, and present antigens to alphabeta T cells. Vgamma2Vdelta2 T cells can also recognize high levels of IPP in certain tumors and in cells treated with pharmacological agents, such as bisphosphonates and alkylamines, that block farnesyl pyrophosphate synthase. Activated Vgamma2Vdelta2 T cells are able to kill most tumor cells because of recognition by T-cell receptor and natural killer receptors. The ubiquitous nature of the antigens converts essentially all Vgamma2Vdelta2 T cells to memory cells at an early age. Thus, primary infections with HMBPP-producing bacteria are perceived by Vgamma2Vdelta2 T cells as a repeat infection. Extensive efforts are underway to harness these cells to treat a variety of cancers and to provide microbial immunity.

Flow cytometric assessment of autologous gammadelta T cells in patients with acute myeloid leukemia: potential effector cells for immunotherapy?

BACKGROUND

Gammadelta T cells are a rare component of the circulating innate immune system capable of exerting anti-neoplastic activity. This population may be suitable for the adoptive immunotherapy of acute myeloid leukemia (AML). Little is known however, about the frequency and function of circulating gammadelta T cells in AML. The aim of the study was to enumerate peripheral blood gammadelta T cells in patients with AML and explore the feasibility of their use clinically.

METHODS

We compared the absolute circulating gammadelta T cell levels in 33 AML patients before and after treatment versus 20 healthy volunteers using flow cytometry. The function of gammadelta T cells was assessed by detection of intracelluar interferon-gamma (IFN-gamma) and cytotoxicity against leukemic blasts.

RESULTS

AML patients with high blast counts prior to induction chemotherapy had marginally decreased gammadelta T cell levels compared with healthy controls: median 38/microL versus 83/microL; P = 0.051. Sequential gammadelta T cell enumeration after induction showed significantly decreased counts in patients with a persistently high blast burden compared to patients with reduced but detectable residual disease (molecular maker or borderline bone marrow infiltration): median 7/microL versus 105/microL; P = 0.008. Patients with residual disease had significantly higher gammadelta T cell counts compared to those retested after they had achieved complete remission (CR); P = 0.0025. In CR, gammadelta T cell counts remained lower than those of healthy individuals: median 33/microL versus 83/microL, P = 0.030. We detected a sharp increase (on average, four-fold higher than values in CR) of gammadelta T cells in patients in very early morphologic or molecular relapse. We also tested the functional properties of gammadelta T cells from patients with AML in CR. Flow cytometric assessment of IFN-gamma revealed similar numbers of gammadelta T cells expressing the T1 cytokine compared with healthy controls. We also showed that gammadelta T cells were able to kill leukemic target cells in vitro.

CONCLUSION

Flow cytometric assessment of gammadelta T cells in patients with AML revealed quantitative shifts with respect to disease status. Our data suggest that gammadelta T cells warrant further investigation as potential therapeutic agents.

Individual Vgamma2-Jgamma1.2+ T cells respond to both isopentenyl pyrophosphate and Daudi cell stimulation: generating tumor effectors with low molecular weight phosphoantigens

Human Vgamma2Vdelta2 T cells exhibit T cell receptor-dependent, MHC-unrestricted recognition of antigen and play important roles in tumor and pathogen immunity. To characterize antigen recognition by the Vgamma2Vdelta2 TCR, we used the combined approach of spectratyping and CDR3 sequence analysis that measures changes in the TCR repertoire before and after stimulation with a phosphoantigen (isopentenyl pyrophosphate) or an irradiated tumor cell line (Daudi B lymphoma). Here we describe common Vgamma2 chains that are substantially involved in the response to both phosphoantigens and tumor cells. The recognition properties of common Vgamma2 chains explains the observation that Vgamma2Vdelta2 T cells expanded by phosphoantigen stimulation specifically recognize and kill some but not all tumor cell lines. Our studies further justify efforts to stimulate tumor immunity by administering low molecular weight phosphoantigens and boosting the frequency and tumor effector functions of circulating Vgamma2Vdelta2 T cells.

Type I IFN-mediated enhancement of anti-leukemic cytotoxicity of gammadelta T cells expanded from peripheral blood cells by stimulation with zoledronate

BACKGROUND

In order to establish efficient gammadelta T-cell based tumor immunotherapy, we explored a method to enhance the cytotoxicity of gammadelta T cells against leukemia cells by stimulating gammadelta T cells with type I IFN.

METHODS

Gammadelta T cells were expanded from normal PBMC by culturing with zoledronate and a low concentration of IL-2 for 2 weeks. For the activation of gammadelta T cells, gammadelta T cells were cultured with type I IFN (HLBI, IFN-alpha2b and IFN-beta) for 1-3 days. The cytotoxicity of HLBI-activated gammadelta T cells against leukemia cell lines and fresh leukemia cells was evaluated by 51Cr-release assay.

RESULTS

Gammadelta T cells, which were expanded and purified with magnetic beads using an anti-gammadelta TCR MAb, were demonstrated to be cytotoxic against leukemia cell lines of both lymphoid and myeloid origin and fresh myeloid leukemia cells. By culturing expanded gammadelta T cells with type I IFN, the expression of the activation marker CD69 was increased and the cytometric bead array showed an elevated production of IFN-gamma by gammadelta T cells. In addition, the cytotoxicity of gammadelta T cells against leukemia cells was definitely enhanced by culturing gammadelta T cells with HLBI.

DISCUSSION

The present study has demonstrated that type I IFN could enhance the anti-leukemic cytotoxicity of expanded gammadelta T cells, which implies that in vitro bisphosphonate (such as zoledronate)-expanded and type I IFN-activated gammadelta T cells could be applied to immunotherapy for hematologic malignancies such as leukemia and lymphoma.

Gammadelta T cells: an alternative type of professional APC

A subtype of activated human gammadelta T cells, termed Vdelta2+ T cells, has antigen-presentation features similar in potency and efficacy to those seen in dendritic cells. Comparable treatment of alphabeta T cells does not result in 'professional' antigen presenting cells (APCs). What is so special about Vdelta2+ T cells? How do they acquire these unexpected properties? Under what physiological conditions would such a bridge between innate and adaptive immunity come into play? In addition to discussing these questions, we introduce a model that correlates the expression of lymph node homing receptors in Vdelta2+ T cells with the involvement of this alternative type of APC in anti-microbial alphabeta T cell responses.

In vivo immunomanipulation of V gamma 9V delta 2 T cells with a synthetic phosphoantigen in a preclinical nonhuman primate model

Vgamma9Vdelta2(+) cells represent the major population of gammadelta T cells in primate blood and react in an MHC-unrestricted fashion to a set of low m.w. nonpeptide phosphoantigens. Two types of structurally related agonists have been discovered so far: the natural phosphoantigens (hydroxydimethyl allyl-pyrophosphate or isopentenyl-pyrophosphate (IPP)) acting directly on Vgamma9Vdelta2(+) TCR and aminobisphosphonates, which block the mevalonate pathway in target cells, leading to accumulation of natural phosphoantigens that in turn activate Vgamma9Vdelta2(+) cells. We demonstrate in the cynomolgus monkey that Vgamma9Vdelta2 can be manipulated in vivo with bromohydrin pyrophosphate (BrHPP)/Phosphostim, a potent synthetic agonist for which the mechanism of action is similar to natural phosphoantigens. Although of very short half-life, injection of BrHPP leads to strong activation of Vgamma9Vdelta2, inducing production of a high level of Th1 cytokines. Combination of BrHPP with low-dose rhIL-2 induces specific amplification of effector-memory peripheral Vgamma9Vdelta2 in blood in a dose-dependant manner. This transient response returns to baseline within 10-15 days. Successive infusions of BrHPP and rhIL-2 induce less vigorous expansions, suggesting a progressive exhaustion of the response. As no toxicity is detected with or without IL-2, this scheme represents a promising immunotherapeutic strategy for induction of systemic Th1 cytokines and massive expansion of gammadelta T cell subset with antitumor and anti-infectious properties.

Drug-induced expansion and differentiation of V gamma 9V delta 2 T cells in vivo: the role of exogenous IL-2

Human Vgamma9Vdelta2 T cells recognize nonpeptidic Ags generated by the 1-deoxy-d-xylulose 5-phosphate (many eubacteria, algae, plants, and Apicomplexa) and mevalonate (eukaryotes, archaebacteria, and certain eubacteria) pathways of isoprenoid synthesis. The potent Vgamma9Vdelta2 T cell reactivity 1) against certain cancer cells or 2) induced by infectious agents indicates that therapeutic augmentations of Vgamma9Vdelta2 T cell activities may be clinically beneficial. The functional characteristics of Vgamma9Vdelta2 T cells from Macaca fascicularis (cynomolgus monkey) are very similar to those from Homo sapiens. We have found that the i.v. administration of nitrogen-containing bisphosphonate or pyrophosphomonoester drugs into cynomolgus monkeys combined with s.c. low-dose (6 x 10(5) U/animal) IL-2 induces a large pool of CD27+ and CD27- effector/memory T cells in the peripheral blood of treated animals. The administration of these drugs in the absence of IL-2 is substantially less effective, indicating the importance of additional exogenous costimuli. Shortly after the costimulatory IL-2 treatment, only gammadelta (but not alphabeta) T cells expressed the CD69 activation marker, indicating that Vgamma9Vdelta2 T lymphocytes are more responsive to low-dose IL-2 than alphabeta T cells. Up to 100-fold increases in the numbers of peripheral blood Vgamma9Vdelta2 T cells were observed in animals receiving the gammadelta stimulatory drug plus IL-2. Moreover, the expanded Vgamma9Vdelta2 T cells were potent Th1 effectors capable of releasing large amounts of IFN-gamma. These results may be relevant for designing novel (or modifying current) immunotherapeutic trials with nitrogen-containing bisphosphonate or pyrophosphomonoester drugs.

Anti-lymphoma effect of gammadelta T cells

During the last few years, our knowledge about the activation and control of non-major histocompatibility complex (MHC)-restricted innate effector lymphocytes (such as natural killer (NK) cells, NK T cells and gammadelta T cells) has advanced enormously and immunotherapeutic strategies based on these cell types receive more and more attention. Apart from NK cells, several lines of evidence indicate that T cells, which express an alternative T cell receptor (TCR) composed of a CD3-associated gammadelta heterodimer, also contribute to the innate immune defense against tumors. Human gammadelta T cells represent a small subset of T cells (1-10% of peripheral blood T cells) and differ from conventional MHC-restricted ass T cells in recognition of a unique set of antigens ("phosphoantigens") and the lack of requirement of classical antigen-presenting molecules. Besides their role in the innate immune response against pathogens based on the recognition of distinctive microbial metabolic products (metabolites of the non-mevalonate pathway of isoprenoid synthesis), Vgamma9Vdelta2 T cells that constitute the dominant fraction of gammadelta T cells in humans exert potent cytotoxic activity, especially against lymphoid malignancies, mediated by as yet only partially determined pathway(s) of tumor recognition. This article will review available evidence from pre-clinical and early clinical studies regarding the contribution of gammadelta T cells in the defense against lymphoid malignancies and highlights some important issues that need to be addressed in the future.

The Vgamma2/Vdelta2 T-cell repertoire in Macaca fascicularis: functional responses to phosphoantigen stimulation by the Vgamma2/Jgamma1.2 subset

Circulating Vgamma2/Vdelta2 T cells in human and non-human primates respond to small molecular weight non-peptidic phosphoantigens in a major histocompatibility complex (MHC)-unrestricted manner. These responses are encoded by the Vgamma2/Jgamma1.2 chain of the T-cell receptor and are positively selected during early development to create a biased repertoire in adults. We characterized the Vgamma2 chain in cynomolgus macaques (Macaca fascicularis) to develop a non-human primate model for studying the effects of infection and therapy on the circulating Vgamma2/Vdelta2 T-cell subset. The cynomolgus macaque Vgamma2 chain was highly homologous to the Vgamma2 chain from human beings and rhesus macaques (Macaca mulatta), though we noted conserved substitutions in critical residues within the CDR3 for both macaque species. Despite these substitutions, Vgamma2/Vdelta2+ T cells from cynomolgus monkeys exhibited polyclonal responses to two different phosphoantigens. Proliferative responses were observed with both isopentenylpyrophosphate and alendronate, but stronger interferon-gamma secretory responses were observed with isopentenylpyrophosphate. In vitro stimulation and expansion led to selective outgrowth of the Vgamma2/Jgamma1.2 subset, with a marked shift in the Vgamma2 spectratype. As a result of the less biased starting repertoire for Vgamma2, the cynomolgus macaque constitutes a sensitive model for examining the effects of in vitro or in vivo treatments on the Vgamma2/Vdelta2 T-cell population. Our studies establish the value of cynomolgus macaques as a model for Vgamma2/Vdelta2 T-cell responses to non-peptidic antigens, and further evidence the remarkable evolutionary conservation of this unusual, phosphoantigen-responsive T-cell subset that is found only in primate species.

Cytotoxic effects of gammadelta T cells expanded ex vivo by a third generation bisphosphonate for cancer immunotherapy

Nitrogen containing-bisphosphonates (N-BPs), widely used to treat bone diseases, have direct antitumor effects via the inactivation of Ras proteins. In addition to the direct antitumor activities, N-BPs expand gammadeltaT cells, which exhibit major histocompatibility complex-unrestricted lytic activity. BPs accumulate intermediate metabolites which may be tumor antigens in target cells. The purpose of our study was to clarify the cytotoxicity of gammadelta T cells expanded ex vivo by the most potent N-BP, zoledronate (ZOL). Especially, we focused on the importance of pretreatment against target cells also with ZOL; 1 microM ZOL plus IL-2 increased the absolute number of gammadeltaT cells 298-768 fold for 14 days incubation. The small cell lung cancer and fibrosarcoma cell lines pretreated with 5 microM ZOL showed a marked increase in sensitivity to lysis by gammadeltaT cells. While, untreated cell lines were much less sensitive to lysis by gdT cells. Video microscopy clearly demonstrated that gammadeltaT cells killed target cells pre-treated with ZOL within 3 hr. Pretreatment with 80 microg/kg ZOL also significantly enhanced the antitumor activity of gammadeltaT cells in mice xenografted with SBC-5 cells. These findings show that ZOL significantly stimulated the proliferation of gammadeltaT cells and that gammadeltaT cells required pre-treatment with ZOL for cytotoxic activity against target cells.

Profiling blood lymphocyte interactions with cancer cells uncovers the innate reactivity of human gamma delta T cells to anaplastic large cell lymphoma

Quantifying the contacts that circulating lymphocytes have with cancer cells is useful, because their deficit favors malignancy progression. All normal lymphocytes contact, scan, and acquire membrane fragments (trogocytosis) from foreign cells for their immunosurveillance. So in this study, we used the in vitro trogocytosis of PKH67-stained cancer cell lines as a measure of their interactions with bulks of PBMC freshly isolated from healthy donors. Allogeneic PBMC mixed and coincubated in vitro for 1 h did not trogocytosis, whereas in the same conditions CD20(+), CD4(+), CD8(+), gammadelta T, and CD16(+) PBMC interacted strongly with the cancer cells. Although most unprimed lymphoid effectors of innate (NK) and adaptive (B and T) immunity from healthy donors spontaneously trogocytosed different tumoral cell lines, some carcinoma cell lines could escape them in the coculture. This also uncovered the strong interactions of circulating Vgamma9/Vdelta2(+) central memory gammadelta T cells with anaplastic large cell lymphoma. These interaction profiles were stable upon time for healthy blood donors but were different with other tumors and blood donors. This profiling provides interaction signatures for the immunomonitoring of cancer.

Synthesis of chiral phosphoantigens and their activity in gamma delta T cell stimulation

Gammadelta T cells expressing Vgamma2Vdelta2 T cell receptors are activated by a broad range of phosphorus-containing small molecules, termed phosphoantigens, and are of interest in the context of the chemotherapy of B cell malignancies. Here, we report the synthesis of four pairs of chiral phosphoantigens: the bromohydrins of isopentenyl diphosphate (Phosphostim), the epoxides of isopentenyl diphosphate (EIPP); and the corresponding bromohydrin and epoxide analogs of but-3-enyl diphosphate. The ability of each compound to stimulate human Vgamma2Vdelta2 T cells was determined by TNF-alpha release and cell proliferation. In these assays, the (R)-bromohydrin diphosphates were, on average, about twice as active as the (S)-bromohydrin diphosphates. In contrast, the (S)-form of EIPP was about twice as active as (R)-EIPP. The activities of the epoxy but-3-enyl diphosphates were both very low. These results suggest that chiral phosphoantigens, as opposed to racemic mixtures, may have utility in immunotherapy.

Characterization of tumor reactivity of human V gamma 9V delta 2 gamma delta T cells in vitro and in SCID mice in vivo

Human Vgamma9Vdelta2 gammadelta T cells are selectively activated by bacterial phosphoantigens and aminobisphosphonates and exert potent cytotoxicity toward various tumor cells. In this study we have characterized the cytotoxic reactivity of gammadelta T cell lines established from healthy donors by stimulation with aminobisphosphonate alendronate toward melanoma MeWo and pancreatic adenocarcinomas Colo357 and PancTu1 lines in vitro and in vivo upon adoptive transfer into SCID mice. Lysis of all tumor cells was enhanced when gammadelta effector cells were preactivated with phosphoantigens. Recognition of MeWo was TCR dependent, as shown by anti-TCR Ab blockade, whereas only the phosphoantigen-mediated increased, but not the basal, lysis of Colo357 and PancTu1 was inhibited by anti-TCR Ab. Furthermore, lysis of Colo357, but not that of MeWo or PancTu1, was completely inhibited by the pan-caspase inhibitor zVAD, indicating different recognition and effector mechanisms involved in the gammadelta T cell/tumor cell interactions. Upon transfer into SCID mice, alendronate-activated gammadelta T cells given together with IL-2 and alendronate significantly prolonged the survival of SCID mice inoculated with human tumor cells. The best results were thus obtained when gammadelta T cells were repetitively given five times over a period of 30 days. With this protocol, human gammadelta T cells prolonged the mean survival of mice inoculated with MeWo melanoma from 28.5 to 87.3 days (p < 0.0001) and in the case of PancTu1 adenocarcinoma from 23.0 to 48.4 days (p < 0.0001). We conclude that an effective gammadelta T cell-based immunotherapy might require activation of endogenous gammadelta T cells with aminobisphosphonate (or phosphoantigen) and IL-2, followed by adoptive transfer of in vitro expanded gammadelta T cells.

Potential of human gammadelta T lymphocytes for immunotherapy of cancer

T lymphocytes are classified into 2 subsets based on their T-cell receptor (TCR) expression. The vast majority of T cells expresses an alphabeta TCR heterodimer. These alphabeta T cells recognize antigenic peptides presented by MHC class I (for CD8(+) T cells) or MHC class II molecules (for CD4(+) T cells). Concepts of cancer immunotherapy are mostly concerned with activation of these MHC-restricted alphabeta T cells. Until recently, a numerically small subset of T cells, which expresses an alternative TCR composed of a CD3-associated gammadelta heterodimer, has received far less attention as a potential agent in cancer therapy. These gammadelta T cells share with alphabeta T cells certain effector functions such as cytokine production and potent cytotoxic activity but recognize different sets of antigens, usually in a non-MHC-restricted fashion. Different subsets of human gammadelta T cells recognize stress-inducible MHC class I-related molecules frequently expressed on epithelial tumor cells or phosphorylated metabolites which can be generated by tumor cells. In line with this, many tumor cells are highly susceptible to gammadelta T-cell mediated lysis. In our article, we summarize the available evidence for a contribution of human gammadelta T cells in tumor defense and discuss potential strategies for the immunotherapy of tumors based on the endogenous activation and/or adoptive transfer of tumor-reactive gammadelta T lymphocytes.

Human gammadelta T cells as mediators of chimaeric-receptor redirected anti-tumour immunity

Human peripheral blood gammadelta T cells (Vgamma9(+) Vdelta2(+)) can be selectively expanded in vivo by the systemic administration of aminobisphosphonates without prior antigen priming. To assess the potential of human gammadelta T cells to serve as effector cells of specific anti-tumour immunity, we expanded peripheral blood-derived gammadelta T cells and transduced them with recombinant retrovirus encoding G(D2)- or CD19-specific chimaeric receptors. Flow cytometric analysis of T cells from four individual donors cultured in the presence of zoledronate at day 14 of culture showed selective enrichment of the gammadelta T cell population (Vgamma9(+) Vdelta2(+) CD3(+) CD4(-) CD8(-)) to 73-96% of total CD3(+) T cells. Retroviral gene transfer resulted in chimaeric receptor surface expression in 73 +/- 12% of the population. Transduced gammadelta T cells efficiently recognized antigen-expressing tumour cell targets, as demonstrated by target-specific upregulation of CD69 and secretion of interferon-alpha. Moreover, transduced gammadelta T cells efficiently and specifically lysed the antigen-expressing tumour targets. They could be efficiently expanded in vitro and maintained in culture for prolonged periods. Zoledronate-activated human gammadelta T cells expressing chimaeric receptors may thus serve as potent and specific anti-tumour effector cells. Their responsiveness to stimulation with aminobisphosphonates may enable the selective re-expansion of adoptively transferred T cells in vivo, permitting long lasting anti-tumour immune control.

Quantitative structure-activity relationships for gammadelta T cell activation by bisphosphonates

gammadelta T cells are the first line of defense against many infectious organisms and are also involved in tumor cell surveillance and killing. They are stimulated by a broad range of small, phosphorus-containing antigens (phosphoantigens) as well as by the bisphosphonates commonly used in bone resorption therapy, such as pamidronate and risedronate. Here, we report the activation of gammadelta T cells by a broad range of bisphosphonates and develop a pharmacophore model for gammadelta T cell activation, in addition to using a comparative molecular similarity index analysis (CoMSIA) approach to make quantitative relationships between gammadelta T cell activation by bisphosphonates and their three-dimensional structures. The CoMSIA analyses yielded R(2) values of approximately 0.8-0.9 and q(2) values of approximately 0.5-0.6 for a training set of 45 compounds. Using an external test set, the activities (IC(50) values) of 16 compounds were predicted within a factor of 4.5, on average. The CoMSIA fields consisted of approximately 40% hydrophobic, approximately 40% electrostatic, and approximately 20% steric interactions. Since bisphosphonates are known to be potent, nanomolar inhibitors of the mevalonate/isoprene pathway enzyme farnesyl pyrophosphate synthase (FPPS), we also compared the pharmacophores for gammadelta T cell activation with those for FPPS inhibition, using the Catalyst program. The pharmacophores for gammadelta T cell activation and FPPS inhibition both consisted of two negative ionizable groups, a positive charge feature and an endocyclic carbon feature, all having very similar spatial dispositions. In addition, the CoMSIA fields were quite similar to those found for FPPS inhibition by bisphosphonates. The activities of the bisphosphonates in gammadelta T cell activation were highly correlated with their activities in FPPS inhibition: R = 0.88, p = 0.002, versus a human recombinant FPPS (N = 9 compounds); R = 0.82, p < 0.0001, for an expressed Leishmania major FPPS (N = 45 compounds). The bisphosphonate gammadelta T cell activation pharmacophore differs considerably, however, from that reported previously for gammadelta T cell activation by phosphoantigens (Gossman, W.; Oldfield, E. J. Med. Chem. 2002, 45, 4868-4874), suggesting different primary targets for the two classes of compounds. The ability to quite accurately predict the activity of bisphosphonates as gammadelta T cell activators by using 3D QSAR techniques can be expected to help facilitate the design of additional bisphosphonates for potential use in immunotherapy.

Statins prevent bisphosphonate-induced gamma,delta-T-cell proliferation and activation in vitro

The acute phase response is the major adverse effect of intravenously administered N-BPs. In this study we show that N-BPs cause gamma,delta-T-cell activation and proliferation in vitro by an indirect mechanism through inhibition of FPP synthase, an effect that can be overcome by inhibiting HMG-CoA reductase with a statin. These studies clarify the probable initial cause of the acute phase response to N-BP drugs and suggest a possible way of preventing this phenomenon.

INTRODUCTION

The acute phase response is the major adverse effect of intravenously administered nitrogen-containing bisphosphonate drugs (N-BPs), used in the treatment of metabolic bone diseases. This effect has recently been attributed to their action as non-peptide antigens and direct stimulation of gamma,delta-T-cells. However, because N-BPs are potent inhibitors of farnesyl diphosphate (FPP) synthase, they could cause indirect activation of gamma,delta-T-cells owing to the accumulation of intermediates upstream of FPP synthase in the mevalonate pathway, such as isopentenyl diphosphate/dimethylallyl diphosphate, which are known gamma,delta-T-cell agonists.

MATERIALS AND METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from healthy volunteers and treated with N-BP, statin, or intermediates/inhibitors of the mevalonate pathway for 7 days in the presence of interleukin (IL)-2. Flow cytometric analysis of the T-cell-gated population was used to quantify the proportion of gamma,delta-T-cells in the CD3+ population.

RESULTS AND CONCLUSIONS

The ability of N-BPs to stimulate proliferation of CD3+ gamma,delta-T-cells in human PBMC cultures matched the ability to inhibit FPP synthase. Gamma,delta-T-cell proliferation and activation (interferon gamma [IFNgamma] and TNFalpha release) was prevented by mevastatin or lovastatin, which inhibit HMG-CoA reductase upstream of FPP synthase and prevent the synthesis of isopentenyl diphosphate/dimethylallyl diphosphate. Desoxolovastatin, an analog of lovastatin incapable of inhibiting HMG-CoA reductase, did not overcome the stimulatory effect of N-BP. Furthermore, statins did not prevent the activation of gamma,delta-T-cells by a synthetic gamma,delta-T-cell agonist or by anti-CD3 antibody. Together, these observations show that N-BPs indirectly stimulate the proliferation and activation of gamma,delta-T-cells caused by inhibition of FPP synthase and intracellular accumulation of isopentenyl diphosphate/ dimethylallyl diphosphate in PBMCs. Because activation of gamma,delta-T-cells could be the initiating event in the acute phase response to bisphosphonate therapy, co-administration of a statin could be an effective approach to prevent this adverse effect.

Immunobiology of haematological malignant disorders: the basis for novel immunotherapy protocols

The immune system is a complex arrangement of cellular interactions that preserve the integrity of a organism by elimination of all elements judged dangerous. However, the development of tumours in immunocompetent patients suggests the existence of an imbalance that favours tumour cells against the immune response. What are the different possibilities for reversing this process to drive an efficient antitumour response? We discuss, focusing on the haematological features, classic immunity (ie, antigen-specific and HLA-restricted immunity). We address the central issues of tumour antigen presentation and recognition and their possible clinical use. Last, we discuss non-HLA-restricted immunity, which does not require the recognition of specific antigens and relies on particular cell populations such as natural killer cells.