Dietlinde Wolf

Therapeutic Treg expansion in mice by TNFRSF25 prevents allergic lung inflammation

TNF receptor superfamily member 25 (TNFRSF25; also known as DR3, and referred to herein as TNFR25) is constitutively and highly expressed by CD4(+)FoxP3(+) Tregs. However, its function on these cells has not been determined. Here we used a TNFR25-specific agonistic monoclonal antibody, 4C12, to study the effects of TNFR25 signaling on Tregs in vivo in mice. Signaling through TNFR25 induced rapid and selective expansion of preexisting Tregs in vivo such that they became 30%-35% of all CD4(+) T cells in the peripheral blood within 4 days. TNFR25-induced Treg proliferation was dependent upon TCR engagement with MHC class II, IL-2 receptor, and Akt signaling, but not upon costimulation by CD80 or CD86; it was unaffected by rapamycin. TNFR25-expanded Tregs remained highly suppressive ex vivo, and Tregs expanded by TNFR25 in vivo were protective against allergic lung inflammation, a mouse model for asthma, by reversing the ratio of effector T cells to Tregs in the lung, suppressing IL-13 and Th2 cytokine production, and blocking eosinophil exudation into bronchoalveolar fluid. Our studies define what we believe to be a novel mechanism for Treg control and important functions for TNFR25 in regulating autoaggression that balance its known role in enhancing autoimmunity.

HIV Nef Enhances Tat-Mediated Viral Transcription through a hnRNP-K-Nucleated Signaling Complex

Although dispensable in vitro, HIV Nef enables high-level viral replication in infected hosts by an as yet unexplained mechanism. Previously, we proposed that Nef functionally cooperates with the viral transactivator Tat by derepressing the viral promoter via a Nef-associated kinase complex (NAKC). Here, we demonstrate that hnRNP-K, a host factor thought to facilitate crosstalk between kinases and gene expression, interacts with Nef and, as part of NAKC, nucleates Nef-interacting kinases, including Lck, PKCdelta, and PI-3 kinase, leading to Lck and Erk1/2 activation. This strongly increased HIV transcription, which depended on Tat and the NF-kB motif in the viral promoter, but not on NF-kB activation. Depletion of hnRNP-K in a Jurkat model of HIV latency increased Erk1/2 activity and greatly augmented HIV reactivating stimuli. We conclude that hnRNP-K coordinates membrane signaling with transcriptional derepression through Erk1/2 and is targeted by HIV to enable Tat-mediated transcription.

Cloning, Expression, and Functional Characterization of TL1A-Ig

TNF superfamily member 15 (TL1A) is the ligand for TNFR superfamily (TNFRSF)25. We previously reported that TNFRSF25 stimulation with an agonist Ab, 4C12, expands pre-existing CD4+Foxp3+ regulatory T cells (Tregs) in vivo. To determine how the physiological ligand differs from the Ab, we generated a soluble mouse TL1A-Ig fusion protein that forms a dimer of TL1A trimers in solution with an apparent molecular mass of 516 kDa. In vitro, TL1A-Ig mediated rapid proliferation of Foxp3+ Tregs and a population of CD4+Foxp3− conventional T cells. TL1A-Ig also blocked de novo biogenesis of inducible Tregs and it attenuated the suppressive function of Tregs. TNFRSF25 stimulation by TL1A-Ig in vivo induced expansion of Tregs such that they increased to 30–35% of all CD4+ T cells in the peripheral blood within 5 d of treatment. Treg proliferation in vivo was dependent on TCR engagement with MHC class II. Elevated Treg levels can be maintained for at least 20 d with daily injections of TL1A-Ig. TL1A-Ig–expanded Tregs expressed high levels of activation/memory markers KLRG1 and CD103 and were highly suppressive ex vivo. TL1A-Ig–mediated Treg expansion in vivo was protective against allergic lung inflammation, a mouse model for asthma, by reversing the ratio of conventional T cells to Tregs in the lung and blocking eosinophil exudation into the bronchoalveolar fluid. Thus, TL1A-Ig fusion proteins are highly active and tightly controllable agents to stimulate Treg proliferation in vivo, and they are uniquely able to maintain high levels of expanded Tregs by repeated administration.

Tregs expanded in vivo by TNFRSF25 agonists promote cardiac allograft survival.

Background Thymic-derived Foxp3+CD4+ regulatory T cells (Tregs)—also called natural Tregs—are critical for the induction and maintenance of transplantation tolerance. Using an agonistic tumor necrosis factor–receptor super family (TNFRSF) 25 antibody, clone 4C12, we showed that TNFRSF25 is a powerful regulator of Treg proliferation–mediating expansion of natural Tregs in vivo. In the present study, we investigate the role of Tregs expanded in vivo by TNFRSF25 on cardiac allograft survival in a mouse model of fully major histocompatibility complex–mismatched ectopic heart transplants. Methods C57BL/6 mice were treated with 20 &mgr;g of TNFRSF25 agonist 4C12 4 days before heterotopic allogeneic heart transplantation. The survival of the graft was monitored daily by abdominal palpation until the cessation of cardiac contraction. The severity of immune rejection was evaluated by histopathology. Infiltration of inflammatory cells and Tregs into the graft were characterized by flow cytometry. The expression of cytokines and other regulatory proteins was measured by quantitative real-time polymerase chain reaction. Results Treatment with 4C12 resulted in expansion of Tregs to 30%–35% of CD4+ cells and was associated with a significant prolongation of median graft survival from 8 days to 17 days (P=0.0049). On day 7 after transplantation, the time point when controls reject the graft, the transplants of 4C12-treated animals beat strongly and showed increased accumulation of Foxp3+ Tregs within the graft and decreased infiltration of inflammatory cells. Conclusions TNFRSF25 agonists expand Tregs in vivo and delay allograft rejection.

Tumor antigen specific iTreg accumulate in the tumor microenvironment and suppress therapeutic vaccination

Tumor specific antigens (TSA) provide an opportunity to mobilize therapeutic immune responses against cancer. To evade such responses, tumor development in immunocompetent hosts is accompanied by acquisition of both active and passive mechanisms of immune suppression, including recruitment of CD4+FoxP3+ regulatory T cells (Treg). Thymic derived Treg (nTreg) may recognize self-antigens in the tumor microenvironment, while peripherally induced Treg (iTreg) may preferentially recognize the same TSA which provide an opportunity for therapeutic immunity from peripheral T cells. In this study we provide a systematic analysis of nTreg and iTreg accumulation in the tumor microenvironment (TME) at the cellular level. iTreg accumulation to the TME was influenced by the abundance of a known TSA, and in the absence of a known TSA intratumoral Treg displayed a unique TCR repertoire from peripheral Treg. In vivo suppression assays demonstrate that cognate-antigen matched iTreg are more potent suppressors of CD4+ than are polyclonal iTreg or nTreg, but were unable to suppress CD8+ T cell proliferation. Suppression occurred only locally at the site of immunization, and correlated with decreased expression of CD80 and CD86 on CD11c positive cells. Although established tumors facilitated the induction of TSA-specific iTreg, these iTreg suppressed CD4+ T cell accumulation only locally to the TME. Tumor mediated suppression of CD8+ T cell immunity appeared independent of TSA-specific iTreg.

T Cell Costimulation by TNFR Superfamily (TNFRSF)4 and TNFRSF25 in the Context of Vaccination

TNFR superfamily (TNFRSF)4 (OX40, CD134) and TNFRSF25 are costimulatory receptors that influence CD4+ and CD8+ T cell responses to cognate Ag. Independently, these receptors have been described to stimulate overlapping functions, including enhanced proliferation and activation for both regulatory T cells (CD4+Foxp3+; Tregs) and conventional T cells (CD4+Foxp3− or CD8+Foxp3−; Tconvs). To determine the relative functionality of TNFRSF4 and TNFRSF25 in T cell immunity, the activity of TNFRSF4 and TNFRS25 agonistic Abs was compared in the context of both traditional protein/adjuvant (OVA/aluminum hydroxide) and CD8+-specific heat shock protein-based (gp96-Ig) vaccine approaches. These studies demonstrate that both TNFRSF4 and TNFRSF25 independently and additively costimulate vaccine-induced CD8+ T cell proliferation following both primary and secondary Ag challenge. In contrast, the activities of TNFRSF4 and TNFRSF25 were observed to be divergent in the costimulation of CD4+ T cell immunity. TNFRSF4 agonists were potent costimulators of OVA/aluminum hydroxide-induced CD4+ Tconv proliferation, but they only weakly costimulated Treg proliferation and IgG2a production, whereas TNFRSF25 agonists were strong costimulators of Treg proliferation, producers of IgG1, IgG2a, and IgG2b, and weak costimulators of CD4+ Tconv proliferation. Interestingly, Ag-specific cellular and humoral responses were uncoupled upon secondary immunization, which was dramatically affected by the presence of TNFRSF4 or TNFRSF25 costimulation. These studies highlight the overlapping but nonredundant activities of TNFRSF4 and TNFRSF25 in T cell immunity, which may guide the application of receptor agonistic agents as vaccine adjuvants for infectious disease and tumor immunity.

The Role of TNFRSF25:TNFSF15 in Disease… and Health?

TNFRSF25 (DR3) is one of the most recently discovered TNF superfamily receptors and includes an intracellular death domain required to initiate signaling. Over the past decade significant progress has been made in defining the characteristics of this receptor, including the identification of its ligand, TNFSF15 (TL1A). Although TL1A can be provided from a number of sources, signaling through TNFRSF25 is primarily concentrated on T cells. TNFRSF25 signaling can lower the threshold for TCR-induced cell proliferation or cytokine production in an IL-2-dependent manner as well as amplify cytokine production initiated by IL-12 and IL-18. In vivo, TNFRSF25:TL1A signaling has been associated with a number of autoinflammatory conditions including allergic asthma, experimental autoimmune encephalomyelitis, type 1 diabetes, rheumatoid arthritis, and inflammatory bowel disease. Here we discuss the short history of TL1A:TNFRSF25 in health and disease states, including several exciting new observations reported at the 12th international TNF conference, 2009.

Marked in Vivo Donor Regulatory T Cell Expansion via Interleukin-2 and TL1A-Ig Stimulation Ameliorates Graft-versus-Host Disease but Preserves Graft-versus-Leukemia in Recipients after Hematopoietic Stem Cell Transplantation

Regulatory T cells (Tregs) are critical for self-tolerance. Although adoptive transfer of expanded Tregs limits graft-versus-host disease (GVHD) after hematopoietic stem cell transplantation (HSCT), ex vivo generation of large numbers of functional Tregs remains difficult. Here, we demonstrate that in vivo targeting of the TNF superfamily receptor TNFRSF25 using the TL1A-Ig fusion protein, along with IL-2, resulted in transient but massive Treg expansion in donor mice, which peaked within days and was nontoxic. Tregs increased in multiple compartments, including blood, lymph nodes, spleen, and colon (GVHD target tissue). Tregs did not expand in bone marrow, a critical site for graft-versus-malignancy responses. Adoptive transfer of in vivo-expanded Tregs in the setting of MHC-mismatched or MHC-matched allogeneic HSCT significantly ameliorated GVHD. Critically, transplantation of Treg-expanded donor cells facilitated transplant tolerance without GVHD, with complete sparing of graft-versus-malignancy. This approach may prove valuable as a therapeutic strategy promoting transplantation tolerance.

Superior immune reconstitution using Treg-expanded donor cells versus PTCy treatment in preclinical HSCT models

Posttransplant cyclophosphamide (PTCy) has been found to be effective in ameliorating acute graft-versus-host disease (GVHD) in patients following allogeneic hematopoietic stem cell transplantation (aHSCT). Adoptive transfer of high numbers of donor Tregs in experimental aHSCT has shown promise as a therapeutic modality for GVHD regulation. We recently described a strategy for in vivo Treg expansion targeting two receptors: TNFRSF25 and CD25. To date, there have been no direct comparisons between the use of PTCy and Tregs regarding outcome and immune reconstitution within identical groups of transplanted mice. Here, we assessed these two strategies and found both decreased clinical GVHD and improved survival long term. However, recipients transplanted with Treg-expanded donor cells (TrED) exhibited less weight loss early after HSCT. Additionally, TrED recipients demonstrated less thymic damage, significantly more recent thymic emigrants, and more rapid lymphoid engraftment. Three months after HSCT, PTCy-treated and TrED recipients showed tolerance to F1 skin allografts and comparable immune function. Overall, TrED was found superior to PTCy with regard to weight loss early after transplant and initial lymphoid engraftment. Based on these findings, we speculate that morbidity and mortality after transplant could be diminished following TrED transplant into aHSCT recipients, and, therefore, that TrED could provide a promising clinical strategy for GVHD prophylaxis.

Abstract A38: T cell costimulation by TNFRSF4, TNFRSF18, and TNFRSF25 in the context of vaccination.

TNFRSF4 (OX40, CD134), TNFRSF18 (GITR) and TNFRSF25 are costimulatory receptors that influence CD4+ and CD8+ T cell responses to cognate-antigen. Independently, these receptors have been described to stimulate overlapping functions including enhanced proliferation and activation for both regulatory (CD4+FoxP3+, Treg) and conventional (CD4+FoxP3- or CD8+FoxP3-) T cells. To determine the relative functionality of TNFRSF4, TNFRSF18 and TNFRSF25 in T cell immunity, the activity of TNFRSF4, TNFRSF18 and TNFRS25 agonistic antibodies was compared in the context of both traditional protein/adjuvant (ovalbumin/alum) and CD8+ specific heat shock protein based (gp96-Ig) vaccine approaches. These studies demonstrate that both TNFRSF4, TNFRSF18 and TNFRSF25 independently and additively costimulate vaccine induced CD8+ T cell proliferation following both primary and secondary antigen challenge. In contrast, the activity of TNFRSF4 and TNFRSF25 were observed to be divergent in the costimulation of CD4+ T cell immunity. TNFRSF4 and TNFRSF18 agonists were potent costimulators of ova/alum induced CD4+ conventional T cell proliferation but only weakly costimulated Treg proliferation and IgG2a production, while TNFRSF25 agonists were strong costimulators of Treg proliferation, production of IgG1, IgG2a and IgG2b and weak costimulators of CD4+ Tconv proliferation. Interestingly, antigen-specific cellular and humoral responses were uncoupled upon secondary immunization, which was dramatically effected by the presence of TNFRSF4, TNFRSF18 or TNFRSF25 costimulation. These studies highlight the overlapping but non-redundant activities of these three TNF receptors in T cell immunity, which may guide the application of receptor agonistic agents as vaccine adjuvants for infectious disease and tumor immunity. Citation Format: Taylor H. Schreiber, Louis Gonzalez, Dietlinde Wolf, Maria Bodero, Eckhard R. Podack. T cell costimulation by TNFRSF4, TNFRSF18, and TNFRSF25 in the context of vaccination. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr A38.