Tubastatin A, a Selective HDAC6 Inhibitor, Enhances Antigen-Presenting Cell (APC) Function and Restores the Responsiveness of Anergic CD4+ T Cells

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 520-520
Author(s):  
Hongwei Wang ◽  
Zi Wang ◽  
Fengdong Cheng ◽  
Karrune V. Woan ◽  
Jennifer Rock-Klotz ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cd4 T Cells ◽  
Critical Role ◽  
T Cell Tolerance ◽  
Cell Tolerance ◽  
Inflammatory Status ◽  
Cognate Antigen ◽  
Hdac6 Inhibitor ◽  
Antigen Presenting

Abstract Abstract 520 Histones play a critical role in transcriptional regulation, cell cycle progression and developmental events. Histone acetylation/deacetylation alters chromatin structure and affects transcription factor access to DNA. Histone deacetylase inhibitors (HDI) induce growth arrest, cellular differentiation, and apoptosis and are being pursued as anticancer drugs. Interestingly, in addition to their antitumor properties, HDI have also been shown to modulate inflammatory responses. Recently, we have found that HDAC6 is required for the production of the immunosuppressive cytokine IL-10 by APCs. Given the role of this cytokine in T-cell tolerance induction we asked whether inhibition of HDAC6 with Tubastatin A, a potent and selective HDAC6 inhibitor would influence the inflammatory status of APCs and their ability to determine activation versus tolerance of antigen-specific CD4+ T cells in vitro. First, treatment of peritoneal elicited macrophages (PEM) with increasing concentration of Tubastatin A resulted in enhanced tubulin acetylation which was accompanied by enhanced expression of co-stimulatory molecules in treated cells. In addition, Tubastatin-A treated PEM were unable to produce IL-10 and TNF-a in response to LPS stimulation. In sharp contrast, Tubastatin-A treated PEM produce higher level of the pro-inflammatory cytokines IL-12 and IL-6. Next, we evaluated the ability of Tubastatin A-treated APCs to present cognate antigen to naïve and tolerant CD4+ T-cells specific for a MHC class II restricted epitope of influenza hemagglutinin (HA). We found that treatment of PEM with Tubastatin A significantly enhanced their antigen-presenting capabilities leading to effective priming of naïve CD4+ T-cells confirmed by their increased production of IL-2 and IFN-g in response to cognate antigen. More importantly, Tubastatin-A treated APCs were able to restore the responsiveness of tolerant CD4+ T cells isolated from lymphoma bearing mice. Taken together, selective HDAC6 inhibition with Tubastatin A provides a novel therapeutic approach to induce inflammatory APCs and overcome the significant barrier that T-cell tolerance has imposed to effective lymphoma immunotherapy. Disclosures: No relevant conflicts of interest to declare.

The Immunomodulatory Drug Lenalidomide (CC5013; Revlimid), Enhances Antigen-Presenting Cell’s Function Leading to Effective Priming of CD4+ T-Lymphocytes.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 2391-2391
Author(s):  
Hongwei Wang ◽  
Aung Naing ◽  
Fengdong Cheng ◽  
Pedro Horna ◽  
Ildelfonso Suarez ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Mhc Class Ii ◽  
Immune Tolerance ◽  
T Cell Responses ◽  
T Cell Tolerance ◽  
Cell Tolerance ◽  
Cell Responses ◽  
Cognate Antigen ◽  
Antigen Presenting

Abstract Professional antigen-presenting cells (APCs) play an important role in the initiation of antigen-specific T-cell responses. The demonstration that these cells are also required for the induction of T-cell tolerance, placed APCs at the crossroads of immune activation versus immune tolerance. Recent studies have demonstrated that the inflammatory status of the APC at the time of antigen presentation is the central determinant of T-cell priming versus T-cell tolerance. As such, therapeutic induction of inflammatory APCs might override immune tolerance and enhance the efficacy of immunotherapeutic strategies targeting hematologic tumors. Lenalidomide (CC5013) is a thalidomide analogue with immunomodulatory properties. Phase I and Phase II clinical trials in patients with myelodysplastic syndrome (MDS) have shown high frequency of erythropoietic responses, particularly in patients with 5q31 deletion associated with emergence of polyclonal lymphoid infiltrate in responding patient bone marrows. This observation raised the question as to whether immunological mechanism(s) may mediate, at least in part, the beneficial effect of CC5013 in patients with MDS. To gain further insight into the effects of Lenalidomide on APC’s function and regulation of antigen-specific CD4+ T-cell responses, we treated peritoneal elicited macrophages (PEM) and bone marrow-derived dendritic cells (DCs) with escalating concentration of Lenalidomide in vitro. Enhanced expression of both B7.1 and B7.2 co-stimulatory molecules was observed in Lenalidomide-treated APCs relative to untreated APCs. No difference in the expression of MHC class II molecules or CD40 was detected. Assessment of cytokine production by ELISA showed that Lenalidomide-treated APCs produce higher levels of TNF-a, IL-6 and IL-10 in response to LPS stimulation as compared to untreated APCs. Next, we evaluated the ability of Lenalidomide-treated APCs to present cognate antigen to naïve and tolerant CD4+ T-cells specific for a MHC class II restricted epitope of influenza hemagglutinin (HA). We found that treatment of either PEM or DC with low doses of Lenalidomide (range: 1.5–12.5 uM) significantly enhanced their antigen-presenting capabilities leading to effective priming of naïve CD4+ T-cells confirmed by their increased production of IL-2 and IFN-gamma in response to cognate antigen. Taken together, our results shows that by inducing inflammatory APCs, Lenalidomide directs the outcome of antigen-specific T-cell responses. Furthermore, they have broadened the scope of this drug as a promising adjuvant in cancer immunotherapy.

JQ 1, a Selective Bromodomain Inhibitor, Decreased the Expression of the Tolerogenic Molecule PDL1 in Antigen-Presenting Cells (APCs) and Restores the Responsiveness of Anergic CD4+ T Cells

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 2749-2749 ◽  
Author(s):  
Hongwei Wang ◽  
Fengdong Cheng ◽  
Limin Xing ◽  
Xiaohong Zhao ◽  
Alejandro Villagra ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cd4 T Cells ◽  
Inflammatory Cytokine ◽  
Conflicts Of Interest ◽  
Specific Inhibitor ◽  
Inflammatory Status ◽  
Bet Inhibitors ◽  
Cognate Antigen ◽  
Antigen Presenting

Abstract Bromodomain and extraterminal (BET) is a protein domain that recognizes acetylated lysine residues such as those on the N-terminal tails of histones. This recognition is often a prerequisite for protein-histone association, chromatin remodeling and gene transcription. The role of BET proteins in regulating the response of inflammatory cytokine genes through translation of histone marks is poorly understood. Given that the inflammatory status of the APC is critical in determining T-cell activation versus T-cell tolerance and that epigenetic modifications of specific genes in the APC play a key role in this process, we recently determined the functional consequences of inhibiting BET in APCs. First, we evaluated the effects of JQ 1, a selective small-molecule BET bromodomain inhibitor on APC’s function and its regulation of antigen-specific CD4+ T-cells response. In vitro treatment of peritoneal elicited macrophages (PEM) or bone marrow derived dendritic cells (DCs) with increasing concentrations of JQ 1 resulted in decreased expression and protein production of the anti-inflammatory cytokine IL-10 and IL-6 in response to LPS stimulation. At the concentration used, JQ 1 did not affect the viability of treated APCs. Second, analysis of the expression of MHC class molecules and co-stimulatory molecules revealed a decreased expression of the tolerogenic PDL1 molecule in JQ 1- treated APCs as compared to untreated APCs. Third, we evaluated the ability of JQ 1 treated APCs to present cognate antigen to naïve or tolerant antigen-specific CD4+ T-cells. We found that treatment of either PEM or DC with JQ 1 enhanced their antigen-presenting capabilities leading to effective priming of naïve CD4+ T-cells confirmed by their increased production of IL-2 and IFN-gamma in response to cognate antigen. More importantly, JQ 1- treated APCs were able to restore the responsiveness of tolerant CD4+ T-cells isolated from lymphoma bearing hosts. Taken together, we have found that APCs treated with the Bromodomain specific inhibitor JQ 1 are more inflammatory, display lower expression of the immunosuppressive molecule PDL1 and more importantly, are capable of restoring the responsiveness of tolerant T-cells. Our studies therefore have unveiled a previously unknown immunological effect of BET inhibitors and have broadened their clinical scope as promising adjuvants in cancer immunotherapy. Disclosures No relevant conflicts of interest to declare.

Regulatory T Cells Are Not Required for Prevention of RBC-Specific Autoantibody Generation

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 568-568
Author(s):  
Krystalyn E. Hudson ◽  
James C. Zimring
Keyword(s):  
T Cells ◽  
T Cell ◽  
Regulatory T Cells ◽  
Cd4 T Cells ◽  
T Cell Tolerance ◽  
Cell Tolerance ◽  
Tolerance Mechanisms ◽  
Antibody Treatment ◽  
Isotype Control

Introduction: Loss of humoral tolerance to red blood cell (RBC) antigens may lead to the generation of pathogenic autoantibodies and result in autoimmune hemolytic anemia (AIHA), a severe and potentially fatal disease. Failure of tolerance to RBC antigens occurs with considerable frequency (1-3 cases/1,000 adults) and prevalence of AIHA is as high as 30% in persons with compromised B and/or T cell tolerance mechanisms. However, RBC-specific tolerance mechanisms are poorly understood. To elucidate the immune tolerances to RBC autoantigens, we utilized HOD mice. The HOD mouse expresses an RBC-specific transgene consisting of hen egg lysozyme (HEL), ovalbumin (OVA), and Duffy. Using the HOD model, we previously demonstrated B cell tolerance to RBC-specific HOD antigen is incomplete; however, T cell tolerance is stringent. HOD mice have similar detectable frequencies of HOD-specific CD4+ T cells compared to B6 mice. Although present, autoreactive HOD-specific CD4+ T cells are non-functional. Circumventing T cell tolerance by adoptive transfer, HOD mice make high titer anti-HOD autoantibodies in vivo. Thus, despite the presence of autoreactive B cells, no HOD-reactive antibodies are detectable unless CD4+ T cells are given, indicating T cell tolerance is a stopgap to autoimmunity. Methods: Leukocytes from C57BL/6 (B6) and HOD mice were harvested and OVA-specific CD4+ T cell responses were assessed by tetramer-pulldown assays with pooled tetramers I-Ab-OVA 329-337/326-334. Isolated cells were stained for surface and intracellular markers and analyzed via flow cytometry. For in vivo analysis, mice were treated with 300ug anti-CD25 (clone PC-61) depleting antibody or isotype control; a subset of antibody-treated mice was immunized with OVA/CFA. Antibodies bound to HOD RBCs were determined by direct antibody test. Anti-HOD antibodies were quantified by indirect immunofluorescence using HOD RBCs as targets. Results: Tetramer pull-down assays revealed similar numbers of OVA-reactive CD4+ T cells from HOD and B6 mice (mean 56 and 40, respectively, p = 0.3). However, cell surface and intracellular marker staining demonstrated that HOD mice had higher numbers of OVA-tetramer reactive CD4+ T cells that express regulatory markers CD25 and FoxP3, and exhaustion marker PD1 as compared to control B6 mice. Inhibitory CTLA4 expression was not detectable on OVA-reactive CD4+ T cells from HOD or B6 mice. To test whether regulatory T cells were required for RBC-specific immune tolerance, HOD and B6 mice were treated with CD25 depleting antibody or isotype control antibody. Anti-CD25 antibody treated mice had a significant reduction of CD25+ cells 4 days post treatment (p < 0.001, 2 independent experiments). Similarly, there was a significant reduction in FoxP3+CD25+CD4+ T cells (Tregs) in anti-CD25 treated mice (p < 0.001), compared to isotype. Mice received weekly injections of anti-CD25 or isotype antibody to maintain depletion for one month. A subset of mice received an OVA/CFA immunization. Sustained CD25+ depletion did not result in anti-HOD autoantibody generation. Further, there was no change in the endogenous frequency of OVA-reactive CD4+ T cells between HOD and B6 mice, regardless of antibody treatment. Similarly, HOD mice treated with depletion (or isotype) antibody and immunized with OVA/CFA did not make detectable anti-HOD autoantibodies. Consistent with lack of detectable autoantibodies, no expansion of OVA-tetramer reactive CD4+ T cells was observed in HOD mice. In contrast, B6 mice (treated with anti-CD25 or isotype antibody) had a detectable expansion of OVA-specific CD4+ T cells as a result of immunization. Conclusions: The data demonstrate a phenotypic difference between the OVA-reactive CD4+ T cells from HOD and B6 mice, with an increase in number of Tregs detectable in HOD mice. Administration of anti-CD25 antibody significantly reduced the number of overall CD25+ cells and Tregs. Prolonged depletion of these cellular subsets did not elicit autoantibodies in HOD mice. Further, immunization of CD25 depleted mice with a strong immune stimulus (OVA/CFA, known to expand OVA-reactive T cells in B6 mice), did not induce anti-HOD autoantibodies nor did it expand OVA-specific autoreactive CD4+ T cells in HOD mice. Together, these data demonstrate that CD25+ cells are not required for the maintenance of RBC-specific T cell tolerance and suggest a role for other regulatory mechanisms. Disclosures No relevant conflicts of interest to declare.

Central T Cell Tolerance and Peripheral B Cell Tolerance for An RBC Autoantigen Are Incomplete in Healthy Mice; Implications for AIHA Pathogenesis

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 693-693
Author(s):  
Krystalyn E Hudson ◽  
Jeanne Hendrickson ◽  
Chantel M Cadwell ◽  
Neal N Iwakoshi ◽  
James C. Zimring
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Cd4 T Cells ◽  
Peripheral Tolerance ◽  
Cd4 T Cell ◽  
T Cell Tolerance ◽  
Cell Tolerance ◽  
B Cell Tolerance

Abstract Abstract 693 Introduction: Breakdown of humoral tolerance to red blood cell (RBC) antigens can result in autoimmune hemolytic anemia (AIHA), a severe and potentially fatal disease. The pathogenesis of AIHA is poorly understood. To investigate the baseline biology of tolerance to self-antigens expressed on RBCs, we utilized a murine transgenic mouse with RBC-specific expression of a model antigen consisting of a triple fusion protein of hen egg lysozyme (HEL), ovalbumin (Ova), and human blood group molecule Duffy; HEL-OVA-Duffy (HOD mouse). Methods: Wild-type C57BL/6 (B6) mice or HOD mice (on a B6 background) were immunized with HEL/CFA or OVA/CFA to test immune responses to antigens contained within HOD. Some animals were immunized with peptides as opposed to whole protein. Anti-HOD antibodies were quantified by indirect immunofluorescence using HOD RBCs as targets. Anti-HEL IgG was quantified by ELISA and anti-HEL secreting B cells were enumerated by ELISPOT. CD4+ T cell responses were assessed by tetramer staining and tetramer pull-down assays using I-Ab-OVA-329-337/326-334. T cell tolerance was specifically broken by adoptive transfer of OT-II CD4+ T cells into HOD mice (OT-II T cells recognize OVA323-339 presented by I-Ab). Effects of HOD antigen expression on B cell development were evaluated by crossing the HOD mouse with an anti-HEL BCR knockin mouse (SwHEL mouse) that is capable of normal class switching. Results: Immunization of B6 mice with OVA/CFA induced high titer antibodies reactive with HOD RBCs; in contrast, no anti-HOD was detected in HOD mice immunized with OVA/CFA. Similarly, no anti-HEL was detected in HOD mice immunized with HEL/CFA, whereas wild-type B6 mice had high anti-HEL titers (p<0.05). These data demonstrate overall humoral tolerance to the HOD antigen. Using pull-down assays, OVA-tetramer reactive T cells were detected in both B6 and HOD mice, with similar endogenous frequencies (mean numbers are 40 and 53 T cells, respectively; at least 6 mice analyzed), suggesting that central tolerance did not eliminate HOD reactive T cells. However, upon immunization with OVA peptide, B6 but not HOD mice had a detectable expansion of OVA-tetramer reactive CD4+ T cells, indicating that peripheral tolerance was preventing HOD autoreactive CD4+ T cells from participating in an immune response. To assess B cell tolerance to the HOD antigen, T cell tolerance was circumvented through adoptive transfer or OTII splenocytes (specific for the OVA323-339 peptide) into HOD mice. Anti-HEL autoantibodies were detected in HOD mice but not control B6 mice (p<0.001). Antibody production correlated with a 10–20 fold increase of anti-HEL antibody secreting cells, as determined by ELISPOT. Autoantibody production in HOD mice was not due to passenger B cells from the OTII donor, an artifact of excess CD4+ T cell number, or bystander activation as no autoantibodies were observed upon adoptive transfer with OTIIs on a Rag knockout background, irrelevant CD4+ T cells from SMARTA mice, or activated CD4+ T cells from TCR75 mice. To test the effects of HOD antigen expression on development of autoreactive B cells, HOD mice were crossed with SwHEL BCR transgenic mice (that express anti-HEL) and the F1 mice were analyzed. HEL-reactive B cells were visualized using multimeric HEL conjugated to allophycocyanin. In HOD-SwHEL+ mice, approximately 46±14% of immature bone marrow B cells were reactive with HEL, compared to 15±12% in HOD+SwHEL+ mice (p=0.043, 3 independent experiments, 5 mice total). Conclusions: These data demonstrate that tolerance to an RBC specific antigen is complete in the CD4+ T cell, but not the B cell compartment. CD4+ T cell tolerance appears to be more an effect of peripheral tolerance than central deletion, as OVA-tetramer reactive CD4+ T cells were visible in HOD mice but did not activate upon immunization with their cognate antigen. In contrast, while the HODxSwHEL F1 mice demonstrate that some B cell tolerance to HOD occurs, the induction of autoantibodies by introducing CD4+ autoreactive T cells (OT-II) demonstrates that B cell tolerance to the HOD antigen is incomplete in HOD mice. Together, these data suggest that a breakdown in T cell tolerance is all that is required for the pathogenesis of AIHA. As the T cell tolerance appears not to be deletional, it is predicted that environmental factors leading to a breakdown in peripheral tolerance of CD4+ T cells would be sufficient to induce AIHA. Disclosures: Zimring: Immucor Inc,: Research Funding.

Mechanisms of early peripheral CD4 T-cell tolerance induction by anti-CD154 monoclonal antibody and allogeneic bone marrow transplantation: evidence for anergy and deletion but not regulatory cells

Blood ◽  
2004 ◽  
Vol 103 (11) ◽  
pp. 4336-4343 ◽  
Author(s):  
Josef Kurtz ◽  
Juanita Shaffer ◽  
Ariadne Lie ◽  
Natalie Anosova ◽  
Gilles Benichou ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Bone Marrow ◽  
T Cells ◽  
Bone Marrow Transplantation ◽  
T Cell ◽  
Cd4 T Cells ◽  
Marrow Transplantation ◽  
Cd4 T Cell ◽  
T Cell Tolerance ◽  
Cell Tolerance

Abstract Anti-CD154 (CD40L) monoclonal antibody (mAb) plus bone marrow transplantation (BMT) in mice receiving CD8 cell-depleting mAb leads to long-term mixed hematopoietic chimerism and systemic donor-specific tolerance through peripheral and central deletional mechanisms. However, CD4+ T-cell tolerance is demonstrable in vitro and in vivo rapidly following BMT, before deletion of donor-reactive CD4 cells is complete, suggesting the involvement of other mechanisms. We examined these mechanisms in more detail. Spot enzyme-linked immunosorbent (ELISPOT) analysis revealed specific tolerization (within 4 to 15 days) of both T helper 1 (Th1) and Th2 cytokine responses to the donor, with no evidence for cytokine deviation. Tolerant lymphocytes did not significantly down-regulate rejection by naive donor-reactive T cells in adoptive transfer experiments. No evidence for linked suppression was obtained when skin expressing donor alloantigens in association with third-party alloantigens was grafted. T-cell receptor (TCR) transgenic mixing studies revealed that specific peripheral deletion of alloreactive CD4 T cells occurs over the first 4 weeks following BMT with anti-CD154. In contrast to models involving anti-CD154 without BMT, BMT with anti-CD154 leads to the rapid induction of anergy, followed by deletion of pre-existing donor-reactive peripheral CD4+ T cells; the rapid deletion of these cells obviates the need for a regulatory cell population to suppress CD4 cell-mediated alloreactivity. (Blood. 2004;103:4336-4343)

scholarly journals CTLA-4 on alloreactive CD4 T cells interacts with recipient CD80/86 to promote tolerance

Blood ◽  
2009 ◽  
Vol 113 (15) ◽  
pp. 3475-3484 ◽  
Author(s):  
Josef Kurtz ◽  
Forum Raval ◽  
Casey Vallot ◽  
Jayden Der ◽  
Megan Sykes
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
T Cell ◽  
Cd4 T Cells ◽  
Bone Marrow Cells ◽  
Antigen Presenting Cells ◽  
Cd4 T Cell ◽  
Cell Tolerance ◽  
Antigen Presenting ◽  
Marrow Cells

Abstract Although the inhibitory receptor CTLA-4 (CD152) has been implicated in peripheral CD4 T-cell tolerance, its mechanism of action remains poorly defined. We analyzed mechanisms of CD4 cell tolerance in a model of tolerance induction involving establishment of mixed hematopoietic chimerism in recipients of fully MHC-mismatched allogeneic bone marrow cells with anti-CD154 mAb. Animals lacking CD80 and CD86 failed to achieve chimerism. We detected no T cell–intrinsic requirement for CD28 for chimerism induction. However, a CD4 T cell–intrinsic signal through CTLA-4 was shown to be essential within the first 48 hours of exposure to alloantigen for the establishment of tolerance and mixed chimerism. This signal must be provided by a recipient CD80/86+ non–T-cell population. Donor CD80/86 expression was insufficient to achieve tolerance. Together, our findings demonstrate a surprising role for interactions of CTLA-4 expressed by alloreactive peripheral CD4 T cells with CD80/86 on recipient antigen-presenting cells (APCs) in the induction of early tolerance, suggesting a 3-cell tolerance model involving directly alloreactive CD4 cells, donor antigen-expressing bone marrow cells, and recipient antigen-presenting cells. This tolerance is independent of regulatory T cells and culminates in the deletion of directly alloreactive CD4 T cells.

Treatment of Antigen-Presenting Cells with Histone Deacetylase Inhibitors Represents a Novel Strategy To Overcome CD4+ T-Cell Tolerance: Divergent Effects on the IL10 and IL-12 Promoter.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 2392-2392
Author(s):  
Hongwei Wang ◽  
Fengdong Cheng ◽  
P. Horna ◽  
I.V. Suarez ◽  
Jian Wu ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
T Cell ◽  
Inflammatory Cytokine ◽  
T Cell Responses ◽  
Cd4 T Cell ◽  
T Cell Tolerance ◽  
Cell Tolerance ◽  
Cell Responses ◽  
Antigen Presenting

Abstract Tumor-antigen-specific T-cell tolerance imposes a significant barrier to the development of effective therapeutic cancer vaccines. Bone marrow-derived antigen presenting cells (APCs) are critical in the induction of this unresponsive state. The requirement for APCs in tolerance induction, together with their well-known role in priming T-cell antitumor responses place APCs at the crossroads of immune activation versus immune tolerance and points to manipulation of these cells as an enticing strategy to modulate T-cell responses against tumors. Identification of the intracellular mechanisms by which APCs induces either T-cell outcome represents therefore a critical step to better understand and overcome tumor-induced immune tolerance. Histones tail plays an important role in modulation of gene transcription. Emerging evidence suggest that inhibition of hystone deacetylases (HDAC) increases the expression of inflammatory genes. Given that the inflammatory status of the APC at the time of antigen presentation is central in determining T-cell priming versus T-cell tolerance, we evaluated the effects of the HDAC inhibitor LAQ842 (Novartis Pharmaceutical Inc.) on APC function and regulation of antigen-specific CD4+ T-cell responses. First, treatment of peritoneal elicited macrophages (PEM) or bone marrow derided dendritic cells (DCs) with increasing concentrations of LAQ842 resulted in enhanced acetylation of hystones H-2A, H-2B, H3 and H4. Analysis of the expression of MHC class molecules and co-stimulatory molecules revealed a significant increase in B7.2 and CD40 in LAQ842-treated APCs as compared to untreated APCs. Utilizing multi-template RNA probes and ELISA we found that LAQ842-treated APCs produce enhanced levels of several inflammatory mediators such as IL-1a, IL-1b, IL-6, TNF-a and RANTES relative to untreated APCs. Similarly, in response to LPS-stimulation, LAQ842-treated APCs produce significant higher levels of the pro-inflammatory cytokine IL-12 but reduce production of the anti-inflammatory cytokine IL-10 as determined by RT-PCR and ELISA. Furthermore, by chromatin immune precipitation (CHIP) assays we found that LAQ842-treated APCs display an increased acetylation of histones associated with the IL-12 promoter but a diminished acetylation of histones at the IL-10 promoter in response to LPS stimulation. Next, we evaluated whether the inflammatory APCs induced by LAQ842 were capable of effectively present antigen and prime productive antigen-specific T-cell responses. In vitro treatment of PEM or DCs with increasing concentrations of LAQ842 resulted in an enhanced presentation of HA-peptide to naïve CD4+ T cells specific for a MHC class II restricted epitope of influenza hemagglutinin (HA). Indeed, these clonotypic T cells display an enhanced HA-specific proliferation, IL-2 and IFN-gamma production relative to clonotypic T cells that encountered HA-antigen on untreated APCs. More importantly, LAQ842-treated APCs were able to restore the responsiveness of tolerant CD4+ T-cells isolated from lymphoma bearing hosts. By demonstrating that HDAC inhibitor induces inflammatory APCs capable of restoring the responsiveness of tolerant T-cells, our studies have unveiled a previously unknown immunological effect of these agents and have broadened their clinical scope as promising adjuvants in cancer immunotherapy.

A Novel Role for Histone Deacetylase 6 (HDAC6) in the Regulation of IL-10 and Immune Tolerance Mediated by Antigen-Presenting Cells (APCs).

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 1360-1360
Author(s):  
Fengdong Cheng ◽  
Hongwei Wang ◽  
Noreen Luetteke ◽  
Javier Pinilla ◽  
Alan Kozikowski ◽  
...  
Keyword(s):  
Gene Expression ◽  
T Cells ◽  
T Cell ◽  
Gene Transcription ◽  
Immune Tolerance ◽  
Cd4 T Cells ◽  
Research Funding ◽  
Inflammatory Status ◽  
C Terminus ◽  
Antigen Presenting

Abstract Abstract 1360 Poster Board I-382 There is now an undisputed recognition that bone marrow (BM) derived APCs can induce T-cell activation as well as T-cell tolerance to tumor antigens. The inflammatory status of the APC at the time of tumor antigen presentation, rather than its phenotype, has been proposed as explanation for the induction of such divergent T-cell outcomes. The molecular basis by which the APC regulate this critical decision remain however to be fully elucidated. Recently, we have focused our efforts to mechanistically understand the regulation of inflammatory/anti-inflammatory genes in their natural setting, the chromatin substrate, and how changes at this level could influence the overall inflammatory status of the APC. In particular, we have studied the consequences of chromatin modification by deacetylation of histone tails (mediated by histone deacetylases) upon expression of IL-10, an immunosuppressive cytokine that plays a central role in tolerance induction. By utilizing a reporter gene carrying the IL10 promoter fused to a luciferase gene, and plasmids encoding Flag-tagged versions of specific HDACs, we found that among all the HDACs evaluated, overexpression of HDAC6 in the APC resulted in transcriptional activation of IL-10 gene expression. Conversely, knockdown of HDAC6 in APCs using shRNA specific for murine HDAC6 resulted in abrogation of IL-10 gene transcription in response to LPS, as compared to APCs transduced with nontarget control (NT). Similar results were found when APCs were treated with the hydroxamate-based selective HDAC6 inhibitors, compound 3 (ST-3-06) and compound 7 (ST-292). Treatment of APCs with either compound resulted in a dose-dependent inhibition of IL-10 production in response to LPS. This effect was specific for IL-10, since no inhibition of other cytokines was observed in HDAC6 inhibitor-treated cells. Next, we evaluated the antigen-presenting capabilities of APCs in which HDAC6 was either knocked down or pharmacologically inhibited. In vitro culture of these APCs with naïve CD4+ T cells specific for a MHC class II restricted epitope of influenza hemagglutinin (HA) in the presence of cognate HA peptide resulted in enhanced activation of antigen-specific T cells since they produce higher levels of IL-2 and IFN-g ƒnrelative to clonotypic T cells encountering antigen on control APCs. Importantly, APCs lacking HDAC6 were capable of restoring the responsiveness of tolerized CD4+ T cells isolated from tumor-bearing mice. Our results suggest a role for HDAC6 in positively regulating IL-10 gene transcription in APCs, an effect that it is opposite to the recently described role of HDAC11 as a negative regulator IL-10 gene transcription1. To address whether a potential crosstalk between these two HDACs could represent a novel mechanism to tightly regulate IL-10 gene expression, we first performed confocal studies that revealed that HDAC6 and HDAC11 indeed colocalize in the cytoplasm. Coimmunoprecipitation confirmed that HDAC6 and HDAC11 interact. Furthermore, by using Flag-tagged HDAC6 wild type (1-1215) or Flag-tagged HDAC6 mutants lacking the C-terminus domain we demonstrated that the C-terminus portion of HDAC6 is required for its interaction with HDAC11. Taken together, we have demonstrated for the first time that HDAC6 regulates IL-10 gene expression, an effect that influences the overall inflammatory status of APC and determines antigen-specific T-cell responses. Importantly, inhibition of HDAC6 in APC with specific HDAC inhibitors represents a novel therapeutic approach to tip the balance towards immune activation rather than immune tolerance, a critical decision with significant implications for cancer immunotherapy. 1Villagra et al. Nature Immunology, 10:92-100, 2009 Disclosures Pinilla: Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Bristol-Myers Squibb: Research Funding; exelixis: Research Funding.

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