Isao Tawara

Histone deacetylase inhibition modulates indoleamine 2,3-dioxygenase–dependent DC functions and regulates experimental graft-versus-host disease in mice

Histone deacetylase (HDAC) inhibitors are antitumor agents that also have antiinflammatory properties. However, the mechanisms of their immunomodulatory functions are not known. We investigated the mechanisms of action of 2 HDAC inhibitors, suberoylanilide hydroxamic acid (SAHA) and ITF 2357, on mouse DC responses. Pretreatment of DCs with HDAC inhibitors significantly reduced TLR-induced secretion of proinflammatory cytokines, suppressed the expression of CD40 and CD80, and reduced the in vitro and in vivo allostimulatory responses induced by the DCs. In addition, injection of DCs treated ex vivo with HDAC inhibitors reduced experimental graft-versus-host disease (GVHD) in a murine allogeneic BM transplantation model. Exposure of DCs to HDAC inhibitors increased expression of indoleamine 2,3-dioxygenase (IDO), a suppressor of DC function. Blockade of IDO in WT DCs with siRNA and with DCs from IDO-deficient animals caused substantial reversal of HDAC inhibition-induced in vitro suppression of DC-stimulated responses. Direct injection of HDAC inhibitors early after allogeneic BM transplantation to chimeric animals whose BM-derived cells lacked IDO failed to protect from GVHD, demonstrating an in vivo functional role for IDO. Together, these data show that HDAC inhibitors regulate multiple DC functions through the induction of IDO and suggest that they may represent a novel class of agents to treat immune-mediated diseases.

Extracorporeal photopheresis reverses experimental graft-versus-host disease through regulatory T cells

Extracorporeal photopheresis (ECP), a technique that exposes isolated white blood cells to photoactivatable 8-methoxypsoralen and ultraviolet A radiation, is used clinically to treat cutaneous T-cell lymphoma and immune-mediated diseases such as graft-versus-host disease (GVHD). ECP is thought to control these diseases in part through direct induction of lymphocyte apoptosis, but its effects on the immune system beyond apoptosis remain poorly characterized. We have developed a novel method for incorporating ECP treatment into well-established and clinically relevant murine models of GVHD to examine its effects during an ongoing immune response. We demonstrate that the transfer of cells treated with ECP reverses established GVHD by increasing donor regulatory T cells and indirectly reducing the number of donor effector lymphocytes that themselves had never been exposed to psoralen and ultraviolet A radiation.

In vivo antigen delivery by a Salmonella typhimurium type III secretion system for therapeutic cancer vaccines

Bacterial vectors may offer many advantages over other antigen delivery systems for cancer vaccines. We engineered a Salmonella typhimurium vaccine strain to deliver the NY-ESO-1 tumor antigen (S. typhimurium-NY-ESO-1) through a type III protein secretion system. The S. typhimurium-NY-ESO-1 construct elicited NY-ESO-1-specific CD8+ and CD4+ T cells from peripheral blood lymphocytes of cancer patients in vitro. Oral administration of S. typhimurium-NY-ESO-1 to mice resulted in the regression of established NY-ESO-1-expressing tumors. Intratumoral inoculation of S. typhimurium-NY-ESO-1 to NY-ESO-1-negative tumors resulted in delivery of antigen in vivo and led to tumor regression in the presence of preexisting NY-ESO-1-specific CD8+ T cells. Specific T cell responses against at least 2 unrelated tumor antigens not contained in the vaccine were observed, demonstrating epitope spreading. We propose that antigen delivery through the S. typhimurium type III secretion system is a promising novel strategy for cancer vaccine development.

Interleukin-6 modulates graft-versus-host responses after experimental allogeneic bone marrow transplantation

Purpose: The graft-versus-tumor (GVT) effect is a potent form of immunotherapy against many hematologic malignancies and some solid tumors. The beneficial GVT effect after allogeneic bone marrow transplantation (BMT) is tightly linked to its most significant complication, graft-versus-host disease (GVHD). The role of interleukin-6 (IL-6) after allogeneic BMT is not well understood. This study used a series of complementary knockout and antibody blockade strategies to analyze the impact of IL-6 in multiple clinically relevant murine models of GVHD and GVT. Experimental Design: We examined the effect of the source of IL-6 by analyzing the role IL-6 deficiency in donor T cells, donor bone marrow or in host tissues. We confirmed and extended the relevance of IL-6 deficiency on GVHD and GVT by treating BMT recipients with anti-mouse IL-6 receptor (IL-6R), MR16-1. Results: Deficiency of IL-6 in donor T cells led to prolongation of survival. Total inhibition of IL-6 with MR16-1 caused an even greater reduction in GVHD-induced mortality. The reduction in GVHD was independent of the direct effects on T effector cell expansion or donor regulatory T cells. GVT responses were preserved after treatment with MR16-1. Conclusion: MR16-1 treatment reduced GVHD and preserved sufficient GVT. Tocilizumab, a humanized anti–IL-6R monoclonal antibody (mAb), is approved in several countries including the United States and European Union for the treatment of rheumatoid arthritis and other inflammatory diseases. Blockade of IL-6 with anti–IL-6R mAb therapy may be testable in clinical trials as an adjunct to prevent GVHD in BMT patients without a significant loss of GVT. Clin Cancer Res; 17(1); 77–88. ©2010 AACR.

Definition of target antigens for naturally occurring CD4+ CD25+ regulatory T cells

The antigenic targets recognized by naturally occurring CD4+ CD25+ regulatory T cells (T reg cells) have been elusive. We have serologically defined a series of broadly expressed self-antigens derived from chemically induced mouse sarcomas by serological identification of antigens by recombinant expression cloning (SEREX). CD4+ CD25+ T cells from mice immunized with SEREX-defined self-antigens had strong suppressive activity on peptide-specific proliferation of CD4+ CD25− T cells and CD8+ T cells. The suppressive effect was observed without in vitro T cell stimulation. Foxp3 expression in these CD4+ CD25+ T cells from immunized mice was 5–10 times greater than CD4+ CD25+ T cells derived from naive mice. The suppressive effect required cellular contact and was blocked by anti-glucocorticoid–induced tumor necrosis factor receptor family–related gene antibody. In vitro suppressive activity essentially disappeared 8 wk after the last immunization. However, it was regained by in vitro restimulation with cognate self-antigen protein but not with control protein. We propose that SEREX-defined self-antigens such as those used in this study represent self-antigens that elicit naturally occurring CD4+ CD25+ T reg cells.

Cutting Edge: Negative Regulation of Dendritic Cells through Acetylation of the Nonhistone Protein STAT-3

Histone deacetylase (HDAC) inhibition modulates dendritic cell (DC) functions and regulates experimental graft-vs-host disease and other immune-mediated diseases. The mechanisms by which HDAC inhibition modulates immune responses remain largely unknown. STAT-3 is a transcription factor shown to negatively regulate DC functions. In this study we report that HDAC inhibition acetylates and activates STAT-3, which regulates DCs by promoting the transcription of IDO. These findings demonstrate a novel functional role for posttranslational modification of STAT-3 through acetylation and provide mechanistic insights into HDAC inhibition-mediated immunoregulation by induction of IDO.

Frequency of CD4+CD25hiFOXP3+ Regulatory T Cells Has Diagnostic and Prognostic Value as a Biomarker for Acute Graft-versus-Host-Disease

The relationship between regulatory T cells (Tregs) and acute graft-versus-host disease (aGVHD) in clinical allogeneic bone marrow transplantation (BMT) recipients is not well established. We conducted a prospective analysis of peripheral blood Tregs as determined by the frequency of CD4(+)CD25(hi)FOXP3(+) lymphocytes in 215 BMT patients. Autologous BMT patients (N = 90) and allogeneic BMT patients without GVHD (N = 65) had similar Treg frequencies, whereas allogeneic patients with GVHD (N = 60) had Treg frequencies that were 40% less than those without GVHD. Treg frequencies decreased linearly with increasing grades of GVHD at onset, and correlated with eventual maximum grade of GVHD (P < .001). In addition, frequency of Tregs at onset of GVHD predicted the response to GVHD treatment (P = .003). Patients with Treg frequencies less than the median had higher nonrelapse mortality (NRM) than patients with Tregs greater than the median, but experienced equivalent relapse mortality, resulting in an inferior survival at 2 years (38% versus 63%, P = .03). Treg frequency may therefore have important prognostic value as a biomarker of aGVHD.

IFN-γ Controls the Generation/Activation of CD4+CD25+ Regulatory T Cells in Antitumor Immune Response

Immunization with serological identification of Ags by recombinant expression cloning (SEREX)-defined self-Ags leads to generation/activation of CD4+CD25+ regulatory T cells with suppressive activities and enhanced expression of Foxp3. This is associated with increased susceptibility to pulmonary metastasis following challenge with syngeneic tumor cells and enhanced development of 3-methylcholanthrene-induced primary tumors. In contrast, coimmunization with the same SEREX-defined self-Ags mixed with a CTL epitope results in augmented CTL activity and heightened resistance to pulmonary metastasis, both of which depend on CD4+ Th cells. These active regulatory T cells and Th cells were derived from two distinct CD4+ T cell subsets, CD4+CD25+ T cells and CD4+CD25− T cells, respectively. In the present study, IFN-γ was found to abrogate the generation/activation of CD4+CD25+ regulatory T cells by immunization with SEREX-defined self-Ag. CD4+CD25+ T cells from these IFN-γ-treated mice failed to exhibit immunosuppressive activity as measured by 1) increased number of pulmonary metastasis, 2) enhanced development of 3-methylcholanthrene-induced primary tumors, 3) suppression of peptide-specific T cell proliferation, and 4) enhanced expression of Foxp3. The important role of IFN-γ produced by CD8+ T cells was shown in experiments demonstrating that CD4+CD25+ T cells cotransferred with CD8+ T cells from IFN-γ−/− mice, but not from wild-type BALB/c mice, became immunosuppressive and enhanced pulmonary metastasis when recipient animals were subsequently immunized with a SEREX-defined self-Ag and a CTL epitope. These findings support the idea that IFN-γ regulates the generation/activation of CD4+CD25+ regulatory T cells.

Alpha-1-antitrypsin monotherapy reduces graft-versus-host disease after experimental allogeneic bone marrow transplantation

Acute graft-versus-host disease (GvHD) is a major complication that prevents successful outcomes after allogeneic bone marrow transplantation (BMT), an effective therapy for hematological malignancies. Several studies demonstrate that donor T cells and host antigen-presenting cells along with several proinflammatory cytokines are required for the induction of GvHD and contribute to its severity. Increasing evidence demonstrates that human serum-derived αalpha-1- anti-trypsin (AAT) reduces production of proinflammatory cytokines, induces anti-inflammatory cytokines, and interferes with maturation of dendritic cells. Using well-characterized mouse models of BMT, we have studied the effects of AAT on GvHD severity. Administration of AAT early after BMT decreased mortality in three models of GvHD and reduced serum levels of proinflammatory cytokines in the allogeneic recipients compared with vehicle (albumin) treated animals. AAT treatment reduced the expansion of alloreactive T effector cells but enhanced the recovery of T regulatory T cells, (Tregs) thus altering the ratio of donor T effector to T regulatory cells in favor of reducing the pathological process. However, despite altering the ratio in vivo, AAT had no direct effects on either the donor T effector cells or T regulatory cells Tregs in vitro. In contrast, AAT suppressed LPS-induced in vitro secretion of proinflammatory cytokines such as TNF-α and IL-1β, enhanced the production of the anti-inflammatory cytokine IL-10, and impaired NF-κB translocation in the host dendritic cells. In light of its long history of safety in humans, these findings suggest that administration of AAT represents a novel unique and viable strategy to mitigate clinical GvHD.

Vorinostat plus tacrolimus and mycophenolate to prevent graft-versus-host disease after related-donor reduced-intensity conditioning allogeneic haemopoietic stem-cell transplantation: a phase 1/2 trial

BACKGROUND Acute graft-versus-host disease (GVHD) remains a barrier to more widespread application of allogeneic haemopoietic stem-cell transplantation. Vorinostat is an inhibitor of histone deacetylases and was shown to attenuate GVHD in preclinical models. We aimed to study the safety and activity of vorinostat, in combination with standard immunoprophylaxis, for prevention of GVHD in patients undergoing related-donor reduced-intensity conditioning haemopoietic stem-cell transplantation. METHODS Between March 31, 2009, and Feb 8, 2013, we did a prospective, single-arm, phase 1/2 study at two centres in the USA. We recruited adults (aged ≥18 years) with high-risk haematological malignant diseases who were candidates for reduced-intensity conditioning haemopoietic stem-cell transplantation and had an available 8/8 or 7/8 HLA-matched related donor. All patients received a conditioning regimen of fludarabine (40 mg/m(2) daily for 4 days) and busulfan (3.2 mg/kg daily for 2 days) and GVHD immunoprophylaxis of mycophenolate mofetil (1 g three times a day, days 0-28) and tacrolimus (0.03 mg/kg a day, titrated to a goal level of 8-12 ng/mL, starting day -3 until day 180). Vorinostat (either 100 mg or 200 mg, twice a day) was initiated 10 days before haemopoietic stem-cell transplantation until day 100. The primary endpoint was the cumulative incidence of grade 2-4 acute GVHD by day 100. This trial is registered with ClinicalTrials.gov, number NCT00810602. FINDINGS 50 patients were assessable for both toxic effects and response; eight additional patients were included in the analysis of toxic effects. All patients engrafted neutrophils and platelets at expected times after haemopoietic stem-cell transplantation. The cumulative incidence of grade 2-4 acute GVHD by day 100 was 22% (95% CI 13-36). The most common non-haematological adverse events included electrolyte disturbances (n=15), hyperglycaemia (11), infections (six), mucositis (four), and increased activity of liver enzymes (three). Non-symptomatic thrombocytopenia after engraftment was the most common haematological grade 3-4 adverse event (nine) but was transient and all cases resolved swiftly. INTERPRETATION Administration of vorinostat in combination with standard GVHD prophylaxis after related-donor reduced-intensity conditioning haemopoietic stem-cell transplantation is safe and is associated with a lower than expected incidence of severe acute GVHD. Future studies are needed to assess the effect of vorinostat for prevention of GVHD in broader settings of haemopoietic stem-cell transplantation. FUNDING Merck, Leukemia and Lymphoma Society, National Institutes of Health, St Baldricks Foundation, Michigan Institute for Clinical and Health Research.