Loss of programmed death ligand-1 expression on donor T cells lessens acute graft-versus-host disease lethality

The PD-1/PD-L1 pathway plays an important role in regulation of alloimmune responses and in induction and maintenance of peripheral tolerance. Because GVHD is driven by donor T cells and PD-L1 expression can be markedly elevated on T cells during activation, we investigated the functional significance of PD-L1 expressed by donor T cells in regulating murine models of acute GVHD. PD-L1 expression was up-regulated on donor CD4 and CD8 T cells during GVHD. We considered the possibility that PD-L1 expression on activated donor T cells might inhibit GVHD by down regulating donor anti-host T cell responses, consistent with PD-L1 co-inhibitory activity when expressed on host parenchymal cells during GVHD. Surprisingly, T cell mediated GVHD lethality was markedly reduced in recipients of PD-L1-/- compared to WT donor T cells in both B6 to BALB/c model of GVHD(P<0.0001; Fig 1A) and in B6 to B10.BR model (P=0.0047; Fig 1B), suggesting that PD-L1 expression on donor T cells is involved in interactions that enhance T cell mediated effector function. Survival data confirmed that PD-L1-/- Teffs and not Tregs were responsible for reduced lethality in recipients of PD-L1-/- donor T cells (Fig 1C). During GVHD, PD-L1-/- donor CD4 and CD8 T cells had reduced expression of gut homing receptors (Fig 1D), and recipients of PD-L1-/- donor T cells had reduced T cell infiltration into lymphoid organs and gut, retained intestinal epithelial integrity, and had lower inflammatory cytokine production. PD-L1-/- donor CD4 and CD8 T cells had increased expression of multiple inhibitory receptors (Fig 1E, 1F), reduced T cell proliferation, and increased T cell apoptosis by transcriptional profiling and cell surface marker expression. Four pathways, including proteasome activity showed decreased expression in PD-L1-/- donor T cells. In vitro T cell activation in the presence of single (PD-L1:B7-1) vs. dual (PD-L1:B7-1 and PD-L1:PD-1) pathway blocking anti-PD-L1 mAb confirmed that T-T interaction between PD-1 and PD-L1 is important for proliferation and survival, whereas sensitive in vitro assays with supported lipid bilayers found no evidence for a functionally relevant cis interaction of PD-L1 and PD-1 on T cells. We found a significant increase in glucose transporter (GLUT1) expression in proliferating WT vs. PD-L1-/- donor CD4 and CD8 T cells, along with increased glycolysis, OXPHOS, glutamine consumption and glutamate production. We also observed increased fatty acid (FA) uptake and FA oxidation, and enhanced pharmacologic inhibition of FA oxidation in WT donor T cells, suggesting that PD-1:PD-L1 interactions are important for FA metabolism, which may further support T cell survival. Studies using stable isotope carbon tracers highlighted the divergent roles for glutamine and glucose in energy generation and biosynthetic pathways. Given the importance of acetyl-CoA as a high energy thioester intermediate in the TCA cycle and a lipogenic precursor for T cells undergoing expansion, significantly enhanced production of acetyl-CoA from glucose by WT donor T cells support the notion that PD-L1 on T cells promotes clonal expansion of alloreactive T cells. In summary, these data are the first to show that PD-L1 expression on donor T cells can provide positive signals for T cell survival, activation, and metabolism. Greater understanding of the function of PD-L1 expression by activated donor T cells will provide new insight into the regulation of GVHD and suggest strategies to selectively inhibit PD-L1 on donor T cells that may be clinically useful to prevent GVHD

Programmed death ligand-1 expression on donor T cells drives graft-versus-host disease lethality.

Programmed death ligand-1 (PD-L1) interaction with PD-1 induces T cell exhaustion and is a therapeutic target to enhance immune responses against cancer and chronic infections. In murine bone marrow transplant models, PD-L1 expression on host target tissues reduces the incidence of graft-versus-host disease (GVHD). PD-L1 is also expressed on T cells; however, it is unclear whether PD-L1 on this population influences immune function. Here, we examined the effects of PD-L1 modulation of T cell function in GVHD. In patients with severe GVHD, PD-L1 expression was increased on donor T cells. Compared with mice that received WT T cells, GVHD was reduced in animals that received T cells from Pdl1-/- donors. PD-L1-deficient T cells had reduced expression of gut homing receptors, diminished production of inflammatory cytokines, and enhanced rates of apoptosis. Moreover, multiple bioenergetic pathways, including aerobic glycolysis, oxidative phosphorylation, and fatty acid metabolism, were also reduced in T cells lacking PD-L1. Finally, the reduction of acute GVHD lethality in mice that received Pdl1-/- donor cells did not affect graft-versus-leukemia responses. These data demonstrate that PD-L1 selectively enhances T cell-mediated immune responses, suggesting a context-dependent function of the PD-1/PD-L1 axis, and suggest selective inhibition of PD-L1 on donor T cells as a potential strategy to prevent or ameliorate GVHD

Programmed death ligand-1 expression on donor T cells drives graft-versus-host disease lethality

Programmed death ligand-1 (PD-L1) interaction with PD-1 induces T cell exhaustion and is a therapeutic target to enhance immune responses against cancer and chronic infections. In murine bone marrow transplant models, PD-L1 expression on host target tissues reduces the incidence of graft-versus-host disease (GVHD). PD-L1 is also expressed on T cells; however, it is unclear whether PD-L1 on this population influences immune function. Here, we examined the effects of PD-L1 modulation of T cell function in GVHD. In patients with severe GVHD, PD-L1 expression was increased on donor T cells. Compared with mice that received WT T cells, GVHD was reduced in animals that received T cells from Pdl1–/– donors. PD-L1–deficient T cells had reduced expression of gut homing receptors, diminished production of inflammatory cytokines, and enhanced rates of apoptosis. Moreover, multiple bioenergetic pathways, including aerobic glycolysis, oxidative phosphorylation, and fatty acid metabolism, were also reduced in T cells lacking PD-L1. Finally, the reduction of acute GVHD lethality in mice that received Pdl1–/– donor cells did not affect graft-versus-leukemia responses. These data demonstrate that PD-L1 selectively enhances T cell–mediated immune responses, suggesting a context-dependent function of the PD-1/PD-L1 axis, and suggest selective inhibition of PD-L1 on donor T cells as a potential strategy to prevent or ameliorate GVHD

Treatment with interleukin-2 in malignant pleural mesothelioma: immunological and angiogenetic assessment and prognostic impact

BACKGROUND: Administration of interleukin-2 (IL-2) has shown some effects on malignant pleural mesothelioma (MPM) tumour regression. The purpose of this study was to investigate the ability of IL-2 to modify immunological effector cells and angiogenesis in MPM patients and their prognostic value. METHODS: Tumour-infiltrating lymphocytes (CD4, CD8, Foxp3), mast cells (MCs) (tryptase and chymase), microvessel count (MVC) and VEGF were determined by immunohistochemistry in two series of MPM patients: 60 patients treated with intra-pleural preoperative IL-2 and 33 patients untreated. RESULTS: Tryptase MCs, and CD8 and Foxp3 lymphocytes were significantly increased in the IL-2-treated group, whereas MVC was significantly lower in the same group. Moreover, in the IL-2-treated group, greater tryptase + MCs and greater Foxp3 lymphocytes were associated with improved and poorer clinical outcomes, respectively. Notably, when these two immunological parameters were combined, they predicted outcomes more effectively. CONCLUSIONS: This study showed that IL-2 treatment leads to a significant increase of immunological parameters, concomitantly with a reduction in vasculature, providing new insight into the cancer mechanisms mediated by IL-2. Moreover, these results suggest that tryptase-positive MCs and Foxp3 + lymphocytes predict clinical outcomes in IL-2-treated patients, highlighting the critical role of the inflammatory response in mesothelioma cancer progression. British Journal of Cancer (2009) 101, 1869-1875. doi:10.1038/sj.bjc.6605438 www.bjcancer.com (C) 2009 Cancer Research U

Maintenance of CD4 T cell fitness through regulation of Foxo1

Foxo transcription factors play an essential role in regulating specialized lymphocyte functions and in maintaining T cell quiescence. Here, we used a system in which Foxo1 transcription-factor activity, which is normally terminated upon cell activation, cannot be silenced, and we show that enforcing Foxo1 activity disrupts homeostasis of CD4 conventional and regulatory T cells. Despite limiting cell metabolism, continued Foxo1 activity is associated with increased activation of the kinase Akt and a cell-intrinsic proliferative advantage; however, survival and cell division are decreased in a competitive setting or growth-factor-limiting conditions. Via control of expression of the transcription factor Myc and the IL-2 receptor β-chain, termination of Foxo1 signaling couples the increase in cellular cholesterol to biomass accumulation after activation, thereby facilitating immunological synapse formation and mTORC1 activity. These data reveal that Foxo1 regulates the integration of metabolic and mitogenic signals essential for T cell competitive fitness and the coordination of cell growth with cell division

Regulatory cell therapy in kidney transplantation (The ONE Study): a harmonised design and analysis of seven non-randomised, single-arm, phase 1/2A trials.

BackgroundUse of cell-based medicinal products (CBMPs) represents a state-of-the-art approach for reducing general immunosuppression in organ transplantation. We tested multiple regulatory CBMPs in kidney transplant trials to establish the safety of regulatory CBMPs when combined with reduced immunosuppressive treatment.MethodsThe ONE Study consisted of seven investigator-led, single-arm trials done internationally at eight hospitals in France, Germany, Italy, the UK, and the USA (60 week follow-up). Included patients were living-donor kidney transplant recipients aged 18 years and older. The reference group trial (RGT) was a standard-of-care group given basiliximab, tapered steroids, mycophenolate mofetil, and tacrolimus. Six non-randomised phase 1/2A cell therapy group (CTG) trials were pooled and analysed, in which patients received one of six CBMPs containing regulatory T cells, dendritic cells, or macrophages; patient selection and immunosuppression mirrored the RGT, except basiliximab induction was substituted with CBMPs and mycophenolate mofetil tapering was allowed. None of the trials were randomised and none of the individuals involved were masked. The primary endpoint was biopsy-confirmed acute rejection (BCAR) within 60 weeks after transplantation; adverse event coding was centralised. The RTG and CTG trials are registered with ClinicalTrials.gov, NCT01656135, NCT02252055, NCT02085629, NCT02244801, NCT02371434, NCT02129881, and NCT02091232.FindingsThe seven trials took place between Dec 11, 2012, and Nov 14, 2018. Of 782 patients assessed for eligibility, 130 (17%) patients were enrolled and 104 were treated and included in the analysis. The 66 patients who were treated in the RGT were 73% male and had a median age of 47 years. The 38 patients who were treated across six CTG trials were 71% male and had a median age of 45 years. Standard-of-care immunosuppression in the recipients in the RGT resulted in a 12% BCAR rate (expected range 3·2-18·0). The overall BCAR rate for the six parallel CTG trials was 16%. 15 (40%) patients given CBMPs were successfully weaned from mycophenolate mofetil and maintained on tacrolimus monotherapy. Combined adverse event data and BCAR episodes from all six CTG trials revealed no safety concerns when compared with the RGT. Fewer episodes of infections were registered in CTG trials versus the RGT.InterpretationRegulatory cell therapy is achievable and safe in living-donor kidney transplant recipients, and is associated with fewer infectious complications, but similar rejection rates in the first year. Therefore, immune cell therapy is a potentially useful therapeutic approach in recipients of kidney transplant to minimise the burden of general immunosuppression.FundingThe 7th EU Framework Programme

Regulatory T cells and their role in rheumatic diseases: a potential target for novel therapeutic development

Regulatory T cells have an important role in limiting immune reactions and are essential regulators of self-tolerance. Among them, CD4+CD25high regulatory T cells are the best-described subset. In this article, we summarize current knowledge on the phenotype, function, and development of CD4+CD25high regulatory T cells. We also review the literature on the role of these T cells in rheumatic diseases and discuss the potential for their use in immunotherapy