Proliferative capacity exhibited by human liver-resident CD49a+CD25+ NK cells.

The recruitment and retention of Natural Killer (NK) cells in the liver are thought to play an important role during hepatotropic infections and liver cirrhosis. The aims of this study were to determine differences between liver-derived and peripheral blood-derived NK cells in the context of liver inflammation and cirrhosis. We conducted a prospective dual-center cross-sectional study in patients undergoing liver transplantation or tumor-free liver resections, in which both liver tissue and peripheral blood samples were obtained from each consenting study participants. Intrahepatic lymphocytes and PBMCs were stained, fixed and analyzed by flow cytometry. Our results showed that, within cirrhotic liver samples, intrahepatic NK cells were particularly enriched for CD49a+ NK cells when compared to tumor-free liver resection samples. CD49a+ liver-derived NK cells included populations of cells expressing CD25, CD34 and CXCR3. Moreover, CD49a+CD25+ liver-derived NK cells exhibited high proliferative capacity in vitro in response to low doses of IL-2. Our study identified a specific subset of CD49a+CD25+ NK cells in cirrhotic livers bearing functional features of proliferation.

CDK6-mediated repression of CD25 is required for induction and maintenance of Notch1-induced T-cell acute lymphoblastic leukemia.

T-cell acute lymphoblastic leukemia (T-ALL) is a high-risk subset of acute leukemia, characterized by frequent activation of Notch1 or AKT signaling, where new therapeutic approaches are needed. We showed previously that cyclin-dependent kinase 6 (CDK6) is required for thymic lymphoblastic lymphoma induced by activated AKT. Here, we show CDK6 is required for initiation and maintenance of Notch-induced T-ALL. In a mouse retroviral model, hematopoietic stem/progenitor cells lacking CDK6 protein or expressing kinase-inactive (K43M) CDK6 are resistant to induction of T-ALL by activated Notch, whereas those expressing INK4-insensitive (R31C) CDK6 are permissive. Pharmacologic inhibition of CDK6 kinase induces CD25 and RUNX1 expression, cell cycle arrest and apoptosis in mouse and human T-ALL. Ablation of Cd25 in a K43M background restores Notch-induced T leukemogenesis, with disease that is resistant to CDK6 inhibitors in vivo. These data support a model whereby CDK6-mediated suppression of CD25 is required for initiation of T-ALL by activated Notch1, and CD25 induction mediates the therapeutic response to CDK6 inhibition in established T-ALL. These results both validate CDK6 as a molecular target for therapy of this subset of T-ALL and suggest that CD25 expression could serve as a biomarker for responsiveness of T-ALL to CDK4/6 inhibitor therapy.

The Interleukin-2-mTORc1 Kinase Axis Defines the Signaling, Differentiation, and Metabolism of T Helper 1 and Follicular B Helper T Cells.

The differentiation of CD4(+) helper T cell subsets with diverse effector functions is accompanied by changes in metabolism required to meet their bioenergetic demands. We find that follicular B helper T (Tfh) cells exhibited less proliferation, glycolysis, and mitochondrial respiration, accompanied by reduced mTOR kinase activity compared to T helper 1 (Th1) cells in response to acute viral infection. IL-2-mediated activation of the Akt kinase and mTORc1 signaling was both necessary and sufficient to shift differentiation away from Tfh cells, instead promoting that of Th1 cells. These findings were not the result of generalized signaling attenuation in Tfh cells, because they retained the ability to flux calcium and activate NFAT-transcription-factor-dependent cytokine production. These data identify the interleukin-2 (IL-2)-mTORc1 axis as a critical orchestrator of the reciprocal balance between Tfh and Th1 cell fates and their respective metabolic activities after acute viral infection.

Regulatory function of CD4+CD25++ T cells in patients with myasthenia gravis is associated with phenotypic changes and STAT5 signaling: 1,25-Dihydroxyvitamin D3 modulates the suppressor activity.

Regulatory T cells were investigated in early-onset (EO) and late-onset (LO) myasthenia gravis patients with anti-acetylcholine receptor antibody (AChR-MG). Alterations in PD-1 and PD-L1 on CD4(+)CD25(++) (Treg) and responder T cells (Tresp, CD4(+)CD25(-)) were observed in LOMG patients. GITR was decreased on CD4(+)CD25(++) of all patients. Decrease of FOXP3 was associated with lower phosphorylation of STAT5.1,25-dihydroxyvitamin D3 (VitD3) increased suppression in co-culture with a stronger effect in patients by acting possibly both on cell groups. Changes in surface molecules and intracellular pathways contribute to the defects of Treg in non-thymomatous AChR-MG and VitD3 can have modulatory effects.

Safety and efficacy of a tCD25 preselective combination anti-HIV lentiviral vector in human hematopoietic stem and progenitor cells.

The successful suppression of human immunodeficiency virus (HIV) in the "Berlin Patient" has highlighted the ability of HIV-resistant hematopoietic stem cells to offer a potential functional cure for HIV-infected patients. HIV stem cell gene therapy can mimic this result by genetically modifying a patient's own cells with anti-HIV genes. Previous attempts of HIV gene therapy have been hampered by a low percentage of transplanted HIV-resistant cells which has led to minimal clinical efficacy. In our current study, we have evaluated the in vitro and in vivo safety and efficacy of a truncated/mutated form of human CD25 preselective anti-HIV lentiviral vector in human hematopoietic stem cells. This preselective vector allows us to purify vector-transduced cells prior to transplantation so an increased percentage of gene-modified cells can be delivered. Here, we demonstrate the safety of this strategy with successful engraftment and multilineage hematopoiesis of transduced cells in a humanized NOD-RAG1-/-IL-2rγ-/- knockout mouse model. Efficacy was also demonstrated with significant protection from HIV-1 infection including maintenance of human CD4+ cell levels and a decrease in HIV-1 plasma viremia. Collectively, these results establish the utility of this HIV stem cell gene therapy strategy and bring it closer to providing a functional cure for HIV-infected patients.

The roles of ZFAT in thymocyte differentiation and homeostasis of peripheral naive T-cells.

ZFAT (zinc-finger gene in AITD susceptibility region), originally identified as a candidate susceptibility gene for autoimmune thyroid disease, has been reported to be involved in various cellular processes and several common diseases including multiple sclerosis. Recent studies revealed that mouse Zfat is a novel critical regulator for both thymocyte differentiation and peripheral T-cell homeostasis. Zfat deficiency at early thymocyte developmental stages results in the inhibition of the development of CD4(+)CD8(+) thymocytes with an impaired positive selection. Zfat deficiency in peripheral T-cells results in a reduction in the number of T-cells with decreased expression of the interleukin-7 receptor-α (IL-7Rα) that is critical for T-cell homeostasis. In addition, T-cell antigen receptor stimulation-induced responses of Zfat-deficient T-cells are also impaired, with reduced IL-2Rα expression. This review highlights and discusses the roles of Zfat in thymocyte differentiation of T-cells and in the homeostasis of naive T-cells with recent work.

The IL-2/CD25 axis maintains distinct subsets of chronic myeloid leukemia-initiating cells.

Just as normal stem cells require niche cells for survival, leukemia-initiating cells (LICs) may also require niche cells for their maintenance. Chronic myeloid leukemia (CML) is caused by the activity of BCR-ABL, a constitutively active tyrosine kinase. CML therapy with tyrosine kinase inhibitors is highly effective; however, due to the persistence of residual LICs, it is not curative. Several factors are known to support CML LICs, but purification of LICs and a thorough understanding of their niche signals have not yet been achieved. Using a CML-like mouse model of myeloproliferative disease, we demonstrate that CML LICs can be divided into CD25(+)FcεRIα(-) Lineage marker (Lin)(-) Sca-1(+)c-Kit(+) (F(-)LSK) cells and CD25(-)F(-)LSK cells. The CD25(+)F(-)LSK cells had multilineage differentiation capacity, with a preference toward cytokine-producing mast cell commitment. Although cells interconverted between CD25(-)F(-)LSK and CD25(+)F(-)LSK status, the CD25(+)F(-)LSK cells exhibited higher LIC capacity. Our findings suggest that interleukin-2 derived from the microenvironment and CD25 expressed on CML LICs constitute a novel signaling axis. The high levels of CD25 expression in the CD34(+)CD38(-) fraction of human CML cells indicate that CD25(+) LICs constitute an "LIC-derived niche" that could be preferentially targeted in therapy for CML.

Mice are unable to endogenously regenerate podocytes during the repair of immunotoxin-induced glomerular injury.

BACKGROUND: Recent studies have reported that podocytes are postnatally generated from progenitor cells localized in Bowman's capsule or in the bone marrow. In the present study, we investigated whether or not podocyte regeneration is important in the repair of injured glomeruli after mild podocyte injury in mice. METHODS: Mild podocyte injury was induced in NEP25 mice (n = 8) by injecting an immunotoxin, LMB2 (0.625 ng/g body weight). Control mice, not injured by LMB2 injection (n = 7) was used as a comparison. Proliferating cells were labeled by continuous infusion of bromodeoxyuridine (BrdU). Podocytes, identified by nephrin, WT1 or podocin staining, that had incorporated BrdU were enumerated 4 weeks later. RESULTS: A total of 742 corpuscles were inspected in serial sections stained for BrdU and nephrin; 19% showed sclerosis. BrdU(+) cells were observed in both the glomeruli and Bowman's capsules, averaging 2.5 ± 3.1 in non-sclerotic corpuscles and 7.0 ± 5.8 in sclerotic corpuscles. Only one BrdU(+) cell was also positive for nephrin. Another cell, localized at a position consistent with its potential identification as a podocyte, was nephrin negative but had incorporated BrdU. WT1 staining similarly revealed that only two nuclei were doubly positive for BrdU and WT1. Additional 1676 corpuscles were inspected by double staining for BrdU and podocin; none were doubly positive. CONCLUSIONS: Podocytes are not replenished by proliferation of endogenous progenitor cells in mice with glomerular injury.

Antitumor efficacy of a monoclonal antibody that inhibits the activity of cancer-associated carbonic anhydrase XII.

Carbonic anhydrase XII (CA XII) is a membrane-tethered cell surface enzyme that is highly expressed on many human tumor cells. Carbonic anhydrase members in this class of exofacial molecules facilitate tumor metabolism by facilitating CO2 venting and intracellular pH regulation. Accordingly, inhibition of exofacial CAs has been proposed as a general therapeutic strategy to target cancer. The recent characterization of 6A10, the first CA XII-specific inhibitory monoclonal antibody, offered an opportunity to evaluate this strategy with regard to CA XII-mediated catalysis. Using functional assays, we showed that 6A10 inhibited exofacial CA activity in CA XII-expressing cancer cells. 6A10 reduced spheroid growth in vitro under culture conditions where CA XII was active (i.e., alkaline pH) and where its catalytic activity was likely rate-limiting (i.e., restricted extracellular HCO3-supply). These in vitro results argued that the antibody exerted its growth-retarding effect by acting on the catalytic process, rather than on antigen binding per se. Notably, when administered in a mouse xenograft model of human cancer, 6A10 exerted a significant delay on tumor outgrowth. These results corroborate the notion that exofacial CA is critical for cancer cell physiology and they establish the immunotherapeutic efficacy of targeting CA XII using an inhibitory antibody.

A small-molecule blocking ribonucleotide reductase holoenzyme formation inhibits cancer cell growth and overcomes drug resistance.

Ribonucleotide reductase (RNR) is an attractive target for anticancer agents given its central function in DNA synthesis, growth, metastasis, and drug resistance of cancer cells. The current clinically established RNR inhibitors have the shortcomings of short half-life, drug resistance, and iron chelation. Here, we report the development of a novel class of effective RNR inhibitors addressing these issues. A novel ligand-binding pocket on the RNR small subunit (RRM2) near the C-terminal tail was proposed by computer modeling and verified by site-directed mutagenesis and nuclear magnetic resonance (NMR) techniques. A compound targeting this pocket was identified by virtual screening of the National Cancer Institute (NCI) diverse small-molecule database. By lead optimization, we developed the novel RNR inhibitor COH29 that acted as a potent inhibitor of both recombinant and cellular human RNR enzymes. COH29 overcame hydroxyurea and gemcitabine resistance in cancer cells. It effectively inhibited proliferation of most cell lines in the NCI 60 human cancer panel, most notably ovarian cancer and leukemia, but exerted little effect on normal fibroblasts or endothelial cells. In mouse xenograft models of human cancer, COH29 treatment reduced tumor growth compared with vehicle. Site-directed mutagenesis, NMR, and surface plasmon resonance biosensor studies confirmed COH29 binding to the proposed ligand-binding pocket and offered evidence for assembly blockade of the RRM1-RRM2 quaternary structure. Our findings offer preclinical validation of COH29 as a promising new class of RNR inhibitors with a new mechanism of inhibition, with broad potential for improved treatment of human cancer.

Preferential expansion of human virus-specific multifunctional central memory T cells by partial targeting of the IL-2 receptor signaling pathway: the key role of CD4+ T cells.

Effector memory T cells are effective in controlling acute infections, but central memory T cells play a key role in long-lasting protection against viruses and tumors. In vivo/in vitro challenge by Ag commonly supports the generation of effector memory T cells with limited longevity. To our knowledge, this study demonstrates for the first time in the human system and under rechallenge conditions that targeting IL-2R by partial mammalian target of rapamycin inhibition or blocking IL-2Rα enriches human CD4(+)/CD8(+) central memory T cells within the virus-specific T cell product associated with enhanced functionality (i.e., multicytokine secretors, including IL-2; enhanced CD137 and CD107a expression on CD8(+) and CD4(+) T cells, respectively; and killing infected target cells). Remarkably, the effects on CD8(+) T cells are mainly mediated via the enhancement of CD4(+) T cell function. The data reveal new insights into the role of CD4(+) T cell support for the quality of CD8(+) T cell memory, even under rechallenge conditions. Moreover, our method offers a new approach to improve the long-lasting efficacy of adoptive T cell therapy in patients.

The effect of human fetal liver-derived mesenchymal stem cells on CD34+ hematopoietic stem cell repopulation in NOD/Shi-scid/IL-2Rã(null) mice.

Mesenchymal stem cells (MSCs) are progenitors that are capable of differentiating into mesenchymal tissues. They are known to support allogeneic hematopoietic stem cell transplantation by facilitating engraftment without increasing the risk of graft-versus-host disease. We optimized culture conditions for human fetal liver-derived MSCs (hFL-MSCs) to investigate the role of hFL-MSCs on repopulation of hematopoietic stem cells in NOD/Shi-scid/IL-2Rγ(null) (NOG) mice using CD34(+) hematopoietic stem cells (HSCs) derived from umbilical cord blood (UCB). FL-MSCs and CD34(+) HSCs were prepared from fetal liver and UCB, respectively. Twenty-four hours after irradiation, CD34(+) HSCs and hFL-MSCs were injected intravenously and intratibially into NOG mice. During 24 weeks posttransplantation, engraftment levels of human cells were analyzed in bone marrow, peripheral blood, and spleen of transplanted mice by flow cytometry. hFL-MSCs showed a fibroblast-like morphology and immunophenotypic characteristics appropriate for MSCs. hFL-MSCs prolonged the survival of NOG mice that had been cotransplanted with UCB CD34(+) cells. Fluorescence-activated cell-sorting analysis showed that engraftment of human cells was increased by cotransplantation of hFL-MSCs. However, significant enhancement of human cell engraftment was not detected in NOG mice regardless of the number of cotransplanted MSCs. Although survival of repopulating NOG mice and engraftment of human cells were prolonged by cotransplantation of hFL-MSCs, 8.0 × 10(6) MSCs were not sufficient to increase HSC engraftment in irradiated NOG mice in vivo.

Natural and induced T CD4+CD25+FOXP3+ regulatory T cells.

Evidence has been accumulated to show that the forkhead/winged-helix transcription factor Foxp3 is a good marker for specialized CD4+ T cells that regulate immune responses to self as well as to a variety of foreign antigens including infectious or tumor antigens, alloantigens, allergens, and commensal antigens. It is now well established that CD4+CD25+Foxp3+ regulatory T cells encompass two categories of lymphocytes that are distinct in their origin, antigen specificity, as well as the stimuli driving their differentiation and homeostasis. Natural CD4+CD25+Foxp3+ regulatory T cells are an independent lineage generated in the thymus through major histocompatibility class II molecules-dependent MHC class high avidity interactions with their T cell receptor. They are specific for self-antigens. Adaptive or induced CD4+CD25+Foxp3+ regulatory T cells stem from mature CD4+CD25-Foxp3-precursors at the periphery following adequate stimulation. They have been shown to develop in vivo following suboptimal antigen stimulation, in situations characterized by chronic inflammation (autoimmunity, allergy, immune responses to tumors and transplants) and also as physiological actors of the mucosal immune system. Although major progress has been accomplished over the last years in our understanding of the central role of CD4+CD25+Foxp3+ regulatory T cells in the control of immune responses, major issues are still elusive. In particular, there are still no reliable phenotypic or functional markers that make it possible to distinguish between natural and induced CD25+Foxp3+ regulatory T cells.

[IL-2/IL-2R pathway in dendritic cell modulates both their cytokine synthesis profiles and their capacity to activate allogeneic CD4+ T lymphocytes]. / La voie IL-2/IL-2R chez la cellule dendritique module à la fois leur synthèse de cytokines et leur capacité à activer des lymphocytes T CD4+ allogéniques.

The results provide new insights into the role of IL-2/IL-2R pathway in DC. We report that stimulation of human monocyte-derived DC with LPS strongly upregulated CD25 (α chain of the IL-2R) expression. In addition, by using a humanized monoclonal antibody against CD25, we demonstrated that the IL-2 signalling in DC upregulated both IL-12 and γIFN production but decreased IL-10 synthesis. Anti-CD25 treatment reduced the ability of LPS-DC to induce allogeneic CD4(+) T cell proliferation as compared to LPS-matured DC. In addition, LPS-matured DC treated with IL-2 had a higher allostimulatory capacity compared to LPS-DC. We also found that LPS-matured DC produced IL-2. Thus, IL-2 seems to contribute actively to DC activation through an autocrine pathway. Moreover, IL-2 pathway in DC is involved in T helper priming. These findings might be useful for protocols in cellular therapy and a valuable tool to understand graft rejection versus the acquisition of peripheral tolerance.

Transcriptome analysis and cytokine profiling of naive T cells stimulated by a tumor vaccine via CD3 and CD25.

T-cell receptor engagement by peptide/MHC complexes constitutes the main signal for the activation of naive T cells, but for a productive generation and maintenance of effector cells, full activation requires additional signals driven by costimulatory molecules present on activated antigen-presenting cells. Herein we describe T cell costimulation via CD25, the interleukin (IL)-2 receptor, during priming of naive T cells with a tumor vaccine. To this end, we produced, purified and characterized the fusion protein bsHN-IL2 which contains the IL-2 cytokine and an antibody scFv fragment directed towards the Hemagglutinin-Neuraminidase (HN) protein of Newcastle Disease Virus (NDV). Tumor vaccine cells were modified by infection with this virus which allows the attachment of the immunocytokine bsHN-IL2. In the presence of CD3-mediated signal 1, the vaccine/bsHN-IL2 provided via CD25 a strong bystander antitumor effect in vitro leading to tumor growth inhibition, even stronger than the vaccine/bsHN-CD28 which provides costimulation via CD28. Transcriptome analysis of naive T cells which were stimulated with the vaccine/bsHN-IL2 showed, similarly to the vaccine/bsHN-CD28, upregulation of 71 genes belonging to different signalling pathways, including PLC-γ1, Grb-2, Vav-1 and PDE-4A. Analysis of the supernatants of activated T cells with ligand-bound tumor vaccine showed that the vaccine/bsHN-IL2, in contrast to the vaccine/bsHN-CD28, did not lead to the production of additional IL-2. We report here the first transcriptome analysis of IL-2 receptor mediated costimulatory signals. The findings provide new insights into mechanisms of function of IL-2 during T cell priming.

IFN-gamma promotes generation of IL-10 secreting CD4+ T cells that suppress generation of CD8 responses in an antigen-experienced host.

Ags characterizing tumors or chronic viral infection are generally presented to the host immune system before specific immunotherapy is initiated, and consequent generation of regulatory CD4(+) T cells can inhibit induction of desired effector CD8 T cell responses. IL-10 produced in response to ongoing Ag exposure inhibits generation of CD8 T cells in an Ag-experienced host. We now show that this IL-10 is produced by Ag experienced CD4(+) glucocorticoid-induced tumor necrosis factor receptor(+) T cells that also secrete IFN-gamma upon antigenic stimulation, that IL-10 secretion by these cells is enhanced through IFN-gamma signaling, and, unexpectedly, that IFN-gamma signaling is required for inhibition of generation of Ag-specific CD8 T cell responses in an Ag-experienced host. Systemic inhibition of both IL-10 and IFN-gamma at the time of immunization may therefore facilitate induction of effective immunotherapeutic responses against tumor specific and viral Ags.

Soluble IL-2RA levels in multiple sclerosis subjects and the effect of soluble IL-2RA on immune responses.

Multiple sclerosis (MS) is an organ-specific autoimmune disorder that is in part genetically determined. The gene encoding the alpha-chain of the IL-2 receptor, IL2RA, harbors alleles associated with risk to MS and other autoimmune diseases. In addition, IL2RA genetic variants correlate with the levels of a soluble form of the IL-2 receptor in subjects with type 1 diabetes and multiple sclerosis. Here, we show that the IL2RA genotypes differentially affects soluble IL-2RA (sIL-2RA) levels in MS cases vs healthy controls; the two variants associated with MS (rs12722489 and rs2104286) account for 15 and 18% of the total variance in log(10)-transformed sIL-2RA concentration in control subjects but less so in subjects with MS (2 and 5%), suggesting that perturbations associated with disease or treatment may influence sIL-2RA levels in subjects with MS. Whereas analyses demonstrate that sIL-2RA serum concentrations are a remarkably stable phenotype in both healthy controls and untreated MS subjects, a difference is observed between benign and malignant MS. These data indicate that, in addition to specific allelic variants at IL2RA, immunological perturbations associated with aggressive forms of the disease can influence sIL-2RA levels in serum of MS subjects. We also demonstrate, functionally, that sIL-2RA can inhibit IL-2 signaling, yet enhance T cell proliferation and expansion. In summary, we propose that before disease onset, strong genetic factors associated with disease risk dictate sIL-2RA levels that may be further modulated with onset of chronic systemic inflammation associated with MS.

Balancing between antitumor efficacy and autoimmune pathology in T-cell-mediated targeting of carcinoembryonic antigen.

Carcinoembryonic antigen (CEA) is intensively studied as a potential target for immunotherapy of colorectal cancers. Although overexpressed by tumors, CEA is also expressed in normal tissues, raising questions about the feasibility and safety of CEA-targeted immunotherapy. We investigated these issues in transgenic mice in which the expression of human CEA in normal tissues closely resembles that in man. Our data show that the T-cell response against CEA in these mice is blunted by both thymic and peripheral tolerance. Consequently, effective tumor targeting is only achieved by adoptive transfer of T cells from nontolerant donors in combination with interventions that eliminate peripheral immune regulatory mechanisms. However, such treatments can result in severe intestinal autoimmune pathology associated with weight loss and mortality. Interestingly, preconditioning of recipient mice by depletion of T-regulatory cells results in immune-mediated tumor control in the absence of toxicity. In this setting, CEA-specific T-cell responses are lower than those induced by toxic regimens and accompanied by additional T-cell responses against non-self antigen. These findings illustrate the importance of testing adoptive immunotherapies targeting self antigens such as CEA in preclinical in vivo models and show that the choice of immune intervention regimen critically determines the balance between therapeutic efficacy and toxicity.

Regulatory T cells: potential target in anticancer immunotherapy.

The concept of regulatory T cells was first described in the early 1970s, and regulatory T cells were called suppressive T cells at that time. Studies that followed have demonstrated that these suppressive T cells negatively regulated tumor immunity and contributed to tumor growth in mice. Despite the importance of these studies, there was extensive skepticism about the existence of these cells, and the concept of suppressive T cells left the center stage of immunologic research for decades. Interleukin-2 receptor alpha-chain, CD25, was first demonstrated in 1995 to serve as a phenotypic marker for CD4+ regulatory cells. Henceforth, research of regulatory T cells boomed. Regulatory T cells are involved in the pathogenesis of cancer, autoimmune disease, transplantation immunology, and immune tolerance in pregnancy. Recent evidence has demonstrated that regulatory T cell-mediated immunosuppression is one of the crucial tumor immune evasion mechanisms and the main obstacle of successful cancer immunotherapy. The mechanism and the potential clinical application of regulatory T cells in cancer immunotherapy are discussed.