Vg9Vd2 T cells respond in a TCR-dependent fashion to both microbial and host-derived pyrophosphate compounds (phosphoantigens, or P-Ag). Butyrophilin-3A1 (BTN3A1), a protein structurally related to the B7 family of costimulatory molecules, is necessary but insufficient for this process. We performed radiation hybrid screens to uncover direct TCR ligands and cofactors that potentiate BTN3A1's P-Ag sensing function. These experiments identified butyrophilin-2A1 (BTN2A1) as essential to Vg9Vd2 T cell recognition. BTN2A1 synergised with BTN3A1 in sensitizing P-Ag-exposed cells for Vg9Vd2 TCR-mediated responses. Surface plasmon resonance experiments established Vg9Vd2 TCRs used germline-encoded Vg9 regions to directly bind the BTN2A1 CFG-IgV domain surface. Notably, somatically recombined CDR3 loops implicated in P-Ag recognition were uninvolved. Immunoprecipitations demonstrated close cell-surface BTN2A1-BTN3A1 association independent of P-Ag stimulation. Thus, BTN2A1 is a BTN3A1-linked co-factor critical to Vg9Vd2 TCR recognition. Furthermore, these results suggest a composite-ligand model of P-Ag sensing wherein the Vg9Vd2 TCR directly interacts with both BTN2A1 and an additional ligand recognized in a CDR3-dependent manner.

Colonization of the gastric mucosa by Helicobacter pylori is the major cause of gastroduodenal pathologies in humans. Studying the outcome of the humoral immune response directed against this gastric pathogen may contribute substantially to vaccine development and to the improvement of diagnostic techniques based on serology. By using two-dimensional gel electrophoresis, 29 proteins from H. pylori G27 were identified which strongly react with sera derived from H. pylori-infected patients suffering from different gastroduodenal pathologies. These antigens were characterized by mass spectrometry and proved to correspond to products of open reading frames predicted by the H. pylori genome sequence. The comparison of the antigenic patterns recognized by these sera revealed no association of specific H. pylori antigens with antibodies in patients with particular gastroduodenal pathologies.

Emerging evidence suggests that nitrogen-containing bisphosphonates have direct and indirect anticancer effects including immunomodulatory effects. Using in vivo targeting of bisphosphonate-reactive γδ T cells by adding low-dose interleukin-2 to zoledronic acid, we evaluated the safety, pharmacodynamics, and antitumor activity of this immunotherapy approach in 21 adults with advanced malignancies (renal cell carcinoma [RCC], malignant melanoma, and acute myeloid leukemia). A total of 58 treatment cycles were administered and the median number of treatment cycles was 2.7 (range, 1 to 6). The regimen was well tolerated, with no grade 3 to 4 drug-related adverse events, except for fever. No objective responses were observed in both cohorts of solid tumors (RCC and malignant melanoma), whereas 2 patients with acute myeloid leukemia (25%) achieved objective tumor responses (partial remission). Pharmacodynamic analyses showed significant in vivo activation (interferon-γ production) and expansion of γδ T cells in all evaluable patients. High pretreatment serum vascular endothelial growth factor (VEGF) levels and an unexpected increase in VEGF induced by zoledronic acid plus low-dose interleukin-2 were correlated with the lack of a clinical response. In conclusion, this study indicates that immunotherapy-induced VEGF can limit clinical innate tumor immune responses, especially for angiogenesis-dependent solid tumors. Our data challenge the current cellular immunotherapy paradigms in the treatment of cancer.

BackgroundThe primary aim of this pilot study was to determine the feasibility and safety of an adoptive transfer and in vivo expansion of human haploidentical γδ T lymphocytes.MethodsPatients with advanced haematological malignancies who are not eligible for allogeneic transplantation received peripheral blood mononuclear cells from half-matched family donors. For that, a single unstimulated leukapheresis product was incubated with both the anti-CD4 and anti-CD8 antibodies conjugated to paramagnetic particles. The depletion procedure was performed on a fully automated CliniMACS® device according to the manufacturer’s instructions. On average, patients received 2.17 × 106/kg (range 0.9-3.48) γδ T cells with <1% CD4- or CD8-positive cells remaining in the product. All patients received prior lymphopenia-inducing chemotherapy (fludarabine 20-25 mg/m2 day -6 until day -2 and cyclophosphamide 30-60 mg/kg day -6 and -5) and were treated with 4 mg zoledronate on day 0 and 1.0x106 IU/m2 IL-2 on day +1 until day +6 for the induction of γδ T cell proliferation in vivo.ResultsThis resulted in a marked in vivo expansion of donor γδ T cells and, to a lower extent, natural killer cells and double-negative αβ T cells (mean 68-fold, eight-fold, and eight-fold, respectively). Proliferation peaked by around day +8 and donor cells persisted up to 28 days. Although refractory to all prior therapies, three out of four patients achieved a complete remission, which lasted for 8 months in a patient with plasma cell leukaemia. One patient died from an infection 6 weeks after treatment.ConclusionThis pilot study shows that adoptive transfer and in vivo expansion of haploidentical γδ T lymphocytes is feasible and suggests a potential role of these cells in the treatment of haematological diseases.

Summary Tumour growth promotes the expansion of CD4+ CD25+ FoxP3+ regulatory T cells (Tregs) which suppress various arms of immune responses and might therefore contribute to tumour immunosurveillance. In this study, we found an inverse correlation between circulating Treg frequencies and phosphoantigen‐induced γδ T‐cell proliferation in cancer patients, which prompted us to address the role of Tregs in controlling the γδ T‐cell arm of innate immune responses. In vitro, human Treg–peripheral blood mononuclear cell (PBMC) co‐cultures strongly inhibited phosphoantigen‐induced proliferation of γδ T cells and depletion of Tregs restored the impaired phosphoantigen‐induced γδ T‐cell proliferation of cancer patients. Tregs did not suppress other effector functions of γδ T cells such as cytokine production or cytotoxicity. Our experiments indicate that Tregs do not mediate their suppressive activity via a cell–cell contact‐dependent mechanism, but rather secrete a soluble non‐proteinaceous factor, which is independent of known soluble factors interacting with amino acid depletion (e.g. arginase‐diminished arginine and indolamine 2,3‐dioxygenase‐diminished tryptophan) or nitric oxide (NO) production. However, the proliferative activity of αβ T cells was not affected by this cell–cell contact‐independent suppressive activity induced by Tregs. In conclusion, these findings indicate a potential new mechanism by which Tregs can specifically suppress γδ T cells and highlight the strategy of combining Treg inhibition with subsequent γδ T‐cell activation to enhance γδ T cell‐mediated immunotherapy.

Human Vγ9Vδ2 T cells are characterized by a unique specificity for certain tumors (e.g., Daudi), cells presenting so-called phosphoantigens such as isopentenyl pyrophosphate (IPP), or cells treated with aminobisphosphonates. We now report conversion of hematopoietic and nonhematopoietic tumor cell lines into Vγ9Vδ2 T cell activators by means of short hairpin RNA-mediated knockdown of expression of the IPP-consuming enzyme, farnesyl pyrophosphate synthase (FPPS). FPPS knockdown cells activated Vγ9Vδ2 T cells, as measured by increased levels of CD69 and CD107a, killing of FPPS knockdown cells, and induction of IFN-γ secretion. The IPP-synthesis-inhibiting drug mevastatin reduced Vγ9Vδ2 T cell activation by FPPS knockdown cells but not activation by the phosphoantigen bromohydrin pyrophosphate. In conclusion, our data support the concept of Vγ9Vδ2 T cells as sensors of a dysregulated isoprenoid metabolism and suggest therapeutic down-modulation of FPPS expression as an additional tool to target tumor cells to Vγ9Vδ2 T cell-mediated immunosurveillance.

SummaryDespite the presence of highly conserved signalling modules, significant cross-communication between different two-component systems has only rarely been observed. Domain swapping and the characterization of liberated signalling modules enabled us to characterize in vitro the protein domains that mediate specificity and are responsible for the high fidelity in the phosphorelay of the unorthodox Bvg and Evg twocomponent systems. Under equimolar conditions, significant in vitro phosphorylation of purified BvgA and EvgA proteins was only obtained by their histidine kinases, BvgS and EvgS respectively. One hybrid histidine kinase consisting of the BvgS transmitter and HPt domains and of the EvgS receiver domain (BvgS-TO-EvgS-R) was able to phosphorylate BvgA but not EvgA. In contrast, the hybrid protein consisting of the BvgS transmitter and the EvgS receiver and HPt domains (BvgS-T-EvgS-RO) was unable to phosphorylate BvgA but efficiently phosphorylated EvgA. These results demonstrate that the C-terminal HPt domains of the sensor proteins endow the unorthodox twocomponent systems with a high specificity for the corresponding regulator protein. In the case of the response regulators, the receiver but not the output domains contribute to the specific interaction with the histidine kinases, because a hybrid protein consisting of the EvgA receiver and the BvgA output domain could only be phosphorylated by the EvgS protein.

Allogeneic innate lymphocytes such as Vγ9Vδ2 T cells are attractive candidates for cancer immunotherapy as they provide MHC-unrestricted antitumor activity without clinical evidence for inducing graft-versus-host disease (GvHD). However, current cellular immunotherapy approaches lack predictive biomarkers identifying patient cohorts most susceptible to immune attack. For this purpose we performed a comprehensive analysis of clinical, genetic, metabolic, and immunophenotypic features of 19 primary acute myeloid leukemia (AML) samples and correlated these factors with AML blast recognition by allogeneic Vγ9Vδ2 T cells. We show that 36% of primary AML samples were intrinsically susceptible to allogeneic Vγ9Vδ2 T cells. Among several evaluated features, only UL-16 binding protein 1 (ULBP1) expression (P<0.01) determines intrinsic AML susceptibility to allogeneic Vγ9Vδ2 T cells. Within the intrinsically resistant AML samples, pretreatment of AML blasts with nitrogen-containing bisphosphonates (NBP) significantly induced Vγ9Vδ2 T-cell cytotoxicity in 50% of AML samples, whereas 50% of AML samples were consistently refractory to γδ T-cell cytolysis. Activity of the mevalonate pathway (P<0.05) and myelomonocytic differentiation of AML (P<0.05) correlated with sensitivity of primary AML samples toward NBP pretreatment. In conclusion, this study identifies subsets of AML patients most likely to benefit from allogeneic Vγ9Vδ2 T-cell-mediated immunotherapy.