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Immune checkpoint therapy, which targets regulatory pathways in T cells to enhance antitumor immune responses, has led to important clinical advances and provided a new weapon against cancer. This therapy has elicited durable clinical responses and, in a fraction of patients, long-term remissions where patients exhibit no clinical signs of cancer for many years. The way forward for this class of novel agents lies in our ability to understand human immune responses in the tumor microenvironment. This will provide valuable information regarding the dynamic nature of the immune response and regulation of additional pathways that will need to be targeted through combination therapies to provide survival benefit for greater numbers of patients. [ABSTRACT FROM AUTHOR]

CTLA-4 is thought to inhibit effector T cells both intrinsically, by competing with CD28 for B7 ligands, and ex-trinsically, through the action of regulatory T cells (Tregs). We studied in vivo responses of normal and CTLA-4-deficient Ag-specific murine effector CD4+ T cells. We directly demonstrate that effector T cell-restricted CTLA-4 inhibits T cell responses in a cell-extrinsic manner. Cotransfer experiments show that CTLA-4 on normal effector CD4+ T cells completely abrogates the dramatically increased expansion normally experienced by their CTLA-4-deficient counterparts. Neither the wild-type nor the CTLA-4-deficient T cells express the Treg transcription factor Foxp3 when transferred alone or together. Thus, cell-extrinsic inhibition of T cell responses by CTLA-4 is not limited to Tregs but is also a function of effector T cells. The Journal of Immunology, 2012, 189: 1123-1127. [ABSTRACT FROM AUTHOR]

The importance of the B7/CD28/CTLA-4 molecules has been established in studies of antigen-presenting cell-derived 87 and its interaction with the T cell costimulatory molecule CD28. CTLA-4, a T cell surface glycoprotein that is related to CD28, can also interact with B7-1 and 87-2. However, less is known about the function of CTLA-4, which is expressed at highest levels after activation. We have generated an antibody to CTLA-4 to investigate the consequences of engagement of this molecule in a carefully defined system using highly purified T cells. We show here that the presence of low levels of B7-2 on freshly explanted T cells can partially inhibit T cell proliferation, and this inhibition is mediated by interactions with CTLA-4. Cross-linking of CTLA-4 together with the TCR and CD28 strongly inhibits proliferation and IL-2 secretion by T cells. Finally, results show that CD28 and CTLA-4 deliver opposing signals that appear to be integrated by the T cell in determining the response to activation. These data strongly suggest that the outcome of T cell antigen receptor stimulation is regulated by CD28 costimulatory signals, as well as inhibitory signals derived from CTLA-4. [ABSTRACT FROM AUTHOR]

The activation of lymphocytes and development of adaptive immune responses is initiated by the engagement of TCRs by antigenic peptide—MHC complexes and shaped at the clonal level by both positive and negative costimulatory signals. The B7 family members are involved at several stages in this process. In this issue of the JCI, Vogt et al. show that the B7 family—related protein V-set and Ig domain—containing 4 (VSIG4) can act as an inhibitor of T cell activation (see the related article beginning on page 2817). Intriguingly, the same molecule was recently independently identified as a complement receptor of the Ig superfamily (CRIg) and was convincingly demonstrated to be a receptor for complement component 3 fragments. These findings raise interesting questions regarding the physiological roles and mechanisms of action of this molecule. Identification of dual functions of this molecule provides an additional level of complexity in T cell costimulation. [ABSTRACT FROM AUTHOR]

The activation of lymphocytes and development of adaptive immune responses is initiated by the engagement of TCRs by antigenic peptide-MHC complexes and shaped at the clonal level by both positive and negative costimulatory signals. The B7 family members are involved at several stages in this process. In this issue of the JCI, Vogt et al. show that the B7 family-related protein V-set and Ig domain-containing 4 (VSIG4) can act as an inhibitor of T cell activation (see the related article beginning on page 2817). Intriguingly, the same molecule was recently independently identified as a complement receptor of the Ig superfamily (CRIg) and was convincingly demonstrated to be a receptor for complement component 3 fragments. These findings raise interesting questions regarding the physiological roles and mechanisms of action of this molecule. Identification of dual functions of this molecule provides an additional level of complexity in T cell costimulation. [ABSTRACT FROM AUTHOR]

Abstract: Costimulatory pathway ligands and receptors can deliver either positive or negative signals to help determine the ultimate fate of activated T lymphocytes. Cytotoxic T lymphocyte antigen-4 (CTLA-4) represents one of the most extensively studied receptors in the costimulatory pathway and has recently been shown to function as a potent inhibitor of T cell-mediated immunity. T-cell expression of CTLA-4 indirectly facilitates tumor progression by restraining host antitumoral immunity. In contrast, administration of a monoclonal antibody to block CTLA-4 function can alleviate restraints on T-cell activity to promote immune-mediated tumor regression. We review the preclinical and clinical experience with CTLA-4 blockade as a promising immunotherapeutic approach to treat patients with advanced prostate cancer. [Copyright &y& Elsevier]

Emerging insights into the mechanisms of activation and negative regulation of innate and adaptive immune cells are providing new opportunities for the development of safe and effective cancer vaccines. [ABSTRACT FROM AUTHOR]

The controlled orchestration of immune responses is a vital feature of cellular immunity in a system that must be able to reliably distinguish self from non-self. Contrary to early beliefs, peptide recognition by T cells exhibits a relatively high level of promiscuity. The requirement for a second signalling event to be present in addition to that provided by T cell receptor ligation for T cell activation to proceed helps to prevent inappropriately directed responses. An expanding array of co-stimulatory or inhibitory signalling receptors and ligands are now recognised to be involved in the control of the crucial decisions made determining the activation, expansion, and effector functions of responding cells, and ultimately the final targeting and execution of these functions. Tight regulation of the temporal and spatial organisation of receptor/ligand expression, combined with both forward and reverse signalling, endows an extraordinary elegance to these co-stimulatory pathways. The immunoglobulin superfamily occupies a central importance in this coordination of immune responses. The understanding of its relevance in a variety of physio-pathological circumstances is now yielding a number of potential targets for therapeutic manipulation, and such immunological molecular adjuvants are beginning to enter clinical trials. [ABSTRACT FROM AUTHOR]

PD-L1 and PD-L2 are ligands for PD-1, a costimulatory molecule that plays an inhibitory role in regulating T cell activation in the periphery. We find that PD-L1 is highly expressed on inflammatory macrophages as compared with resident peritoneal macrophages but can be induced on resident macrophages by classical activation stimuli such as lipopolysaccharide, IFN-γ, and polyinosinic-polycytidylic acid. Further up-regulation of PD-L1 on inflammatory macrophages can also be induced by subsequent exposure to lipopolysaccharide and IFN-γ In contrast, PD-L2 is not expressed on inflammatory macrophages but can be induced by alternative activation via IL-4. Although PD-L1 is highly inducible on a variety of antigen-presenting cell lines as well as resident macrophages, PD-L2 is most significantly inducible only on inflammatory macrophages. PD-L1 up-regulation depends on TLR4 and STAT1, whereas PD-L2 expression depends on IL-4Rα and STAT6. Consistent with these results, T helper 1/T helper 2 (Th1/Th2) cells also differentially up-regulate PD-L1 and PD-L2 expression on inflammatory macrophages. Hence, Th1 cells as well as microbial products can enhance PD-L1 expression on many different macrophage populations, whereas Th2 cells instruct only inflammatory macrophages to up-regulate PD-L2. These results suggest that PD-L1 and PD-L2 might have different functions in regulating type 1 and type 2 responses. [ABSTRACT FROM AUTHOR]

CD28 and CTLA-4 engagement with B7 expressed by APCs generates critical regulatory signals for T cell activation. CD28 is expressed on the T cell surface and enhances T cell expansion, while CTLA-4 localizes primarily to an intracellular compartment and inhibits T cell proliferation. We demonstrate that CTLA-4 has several unique trafficking properties that may regulate its ability to attenuate a T cell response. Importantly, accumulation of CTLA-4 at the immunological synapse is proportional to the strength of the TCR signal, suggesting that cells receiving stronger stimuli are more susceptible to CTLA-4-mediated inhibition. This may represent a novel feedback control mechanism in which a stimulatory signal regulates the recruitment of an inhibitory receptor to a functionally relevant site on the cell surface. [Copyright &y& Elsevier]

Examines the biochemical mechanisms involved in the immunoglobin, CTLA-4's signalling and regulating the immune responses and is mainly located in cytoplasmic vesicles. When does CTLA-4 surface; Importance of the CTLA-4; Findings of studies conducted.

The activation of lymphocytes and development of adaptive immune responses is initiated by the engagement of TCRs by antigenic peptide–MHC complexes and shaped at the clonal level by both positive and negative costimulatory signals. The B7 family members are involved at several stages in this process. In this issue of the JCI, Vogt et al. show that the B7 family–related protein V-set and Ig domain–containing 4 (VSIG4) can act as an inhibitor of T cell activation (see the related article beginning on page 2817). Intriguingly, the same molecule was recently independently identified as a complement receptor of the Ig superfamily (CRIg) and was convincingly demonstrated to be a receptor for complement component 3 fragments. These findings raise interesting questions regarding the physiological roles and mechanisms of action of this molecule. Identification of dual functions of this molecule provides an additional level of complexity in T cell costimulation. [ABSTRACT FROM AUTHOR]

Examines the ability of tumors to deliver antigen-specific signals to T cells and costimulatory signals necessary for full activation of T cells with the expression of the costimulatory ligand B7 on melanoma cells. Rejection mediated by CD8+ T cells; B7 expression rendering tumor cells capable of effective antigen presentation; More.

The author reflects on the use of immune system for cancer treatment. Topics discussed include the role of bacterial component for stimulation of anti-tumor immune response, the activation of inflammatory response and innate immune system for killing tumor cells, and the effects of carcinogens for tumor incidence rates.

Immune checkpoint inhibitors such as anti-CTLA-4 antibody are widely accepted therapeutic options for many cancers, but there is still a considerable gap in achieving their full potential. We explored the potential of activating the innate and adaptive immune pathways together to improve tumor reduction and survival outcomes. We treated a mouse model of melanoma with intratumoral injections of Toll-like receptor 1/2 (TLR1/2) ligand Pam3CSK4 plus i.p. injections of anti-CTLA-4 antibody. This combination treatment enhanced antitumor immune responses both qualitatively and quantitatively over anti-CTLA-4 alone, and its efficacy depended on CD4 T cells, CD8 T cells, Fcγ receptor IV, and macrophages. Interestingly, our results suggest a unique mechanism by which TLR1/2 ligand increased Fcγ receptor IV expression on macrophages, leading to antibody-dependent macrophage-mediated depletion of regulatory T cells in the tumor microenvironment and increasing efficacy of anti-CTLA-4 antibody in the combination treatment. This mechanism could be harnessed to modulate the clinical outcome of anti-CTLA- 4 antibodies and possibly other antibody-based immunotherapies. [ABSTRACT FROM AUTHOR]

Focuses on T cells' two types of signals from antigen-presenting cells (APCs) for activation and subsequent differentiation to effector function. Balanced interplay between positive signals from CD28 and negative signals from CTLA-4; Reason for the CD28 and CTLA-4 receptors; Inhibitory signalling role for CTLA-4; Apoptosis in the homeostatic regulation of T cell responses.

Immune checkpoint therapy (ICT) has dramatically altered clinical outcomes for cancer patients and conferred durable clinical benefits, including cure in a subset of patients. Varying response rates across tumor types and the need for predictive biomarkers to optimize patient selection to maximize efficacy and minimize toxicities prompted efforts to unravel immune and non-immune factors regulating the responses to ICT. This review highlights the biology of anti-tumor immunity underlying response and resistance to ICT, discusses efforts to address the current challenges with ICT, and outlines strategies to guide the development of subsequent clinical trials and combinatorial efforts with ICT. Immune checkpoint therapy provides clinical benefits to many patients across different tumor types. Sharma, Goswami, and colleagues review the mechanisms of and clinical advances in immune checkpoint therapy and outline the challenges and approaches to broaden the clinical utility of immune checkpoint therapy. [ABSTRACT FROM AUTHOR]

An obituary is presented for immunologist Lloyd J. Old.

A letter to the editor is presented regarding the supposed recognition of the Nobel Prize Committee to the contributions of immunologists Ruslan Medzhitov and Charles A. Janeway Jr. in innate immunity.

The 2022 yearly Think Tank Meeting in Siena, Tuscany (Italy), organized by the Italian Network for Tumor Biotherapy (NIBIT) Foundation, the Parker Institute for Cancer Immunotherapy and the World Immunotherapy Council, included a focus on the future of integrating and expanding the use of targeting cytotoxic T-lymphocyte-associated protein 4 (CTLA-4). The conference members exchanged their views on the lessons from targeting CTLA-4 and compared the effect to the impact of blocking Programmed cell death protein 1 (PD1) or its ligand (PDL1). The increasing experience with both therapeutic approaches and their combination suggests that targeting CTLA-4 may lead to more durable responses for a sizeable proportion of patients, though the specific mechanism is not entirely understood. Overcoming toxicity of blocking CTLA-4 is currently being addressed with different doses and dose regimens, especially when combined with PD1/PDL1 blocking antibodies. Novel therapeutics targeting CTLA-4 hold the promise to reduce toxicities and thus allow different combination strategies in the future. On the whole, the consent was that targeting CTLA-4 remains an important strategy to improve the efficacy of cancer immunotherapies. • Anti-CTLA4 is a keyregulator of the immune system programming anti-tumor activity. • Anti-CTLA4 doubles major pathologic response rates in anti-PD1 based neoadjuvant therapies. • Anti-CTLA4 related irAEs can be reduced by dose reduction and novel therapeutics. • Anti-CTLA4 plus anti-PD1 has significant anti-tumor activity in multiple solid tumors. • Anti-CTLA4 is here to stay. [ABSTRACT FROM AUTHOR]

The transcription factor Hellos has been reported to be a marker of regulatory T cells (Treg) of thymic origin, distinguishing them from Treg induced in the periphery (iTreg). In this study, we demonstrate Helios expression in Foxp3+ iTreg, both in vitro and in vivo. Following i.v. peptide injection, in vivo Helios expression in adoptively transferred TCR transgenic T cells was more rapid than Foxp3 induction but less stable at later time points without a second injection of peptide. Our in vitro data suggest that APC influence Hellos expression in a manner distinct from stimuli required for Foxp3 induction. Thus, Helios expression in iTreg may reflect the context of stimulation during Foxp3 induction. In summary, the robust Hellos expression we observe in iTreg precludes its use as a marker of thymic Treg. [ABSTRACT FROM AUTHOR]

The TCR can detect subtle differences in the strength of interaction with peptide/MHC ligand and transmit this information to influence downstream events in T cell responses. Manipulation of the factor commonly referred to as TCR signal strength can be achieved by changing the amount or quality of peptide/MHC ligand. Recent work has enhanced our understanding of the many variables that contribute to the apparent cumulative strength of TCR stimulation during immunogenic and tolerogenic T cell responses. In this review, we consider data from in vitro studies in the context of in vivo immune responses and discuss in vivo consequences of manipulation of strength of TCR stimulation, including influences on T cell-APC interactions, the magnitude and quality of the T cell response, and the types of fate decisions made by peripheral T cells. [ABSTRACT FROM AUTHOR]

Inducible costimulator (ICOS), a member of the CD28 family of costimulatory molecules, is upregulated on the surface of T cells following T cell activation and upon binding to its ligand (ICOSL), initiates a cascade of events that can shape key aspects of the immune response. Although initial studies focused on determining the role of ICOS in Th1 versus T helper 2 (Th2) responses, new insights into its biology have revealed the contribution of ICOS to germinal center formation and isotype switching, as well as its relevance to the fate and function of effector and regulatory CD4+ T cells in the response against self (i.e., tumors) and non-self (i.e., bacterial, worm, and viral infections). This multiplicity of roles positions ICOS at the center of attention for immunotherapy where manipulation of this pathway could lead to novel approaches in the treatment of human diseases. [Copyright &y& Elsevier]

The generation of productive adaptive immune responses depends on the antigen-specific activation of T and B cells. The outcome of T-cell receptor engagement is influenced by signals from both positive and negative regulatory molecules that can either activate or inhibit T-cell function. CD28 and cytotoxic T-lymphocyte antigen-4 are the prototypical members of an immunoglobulin domain-containing protein family that play important roles in the control of T-cell responses against infection, cancer, and in autoimmune disease. Although the precise molecular details of their functions are still under active investigation, tumors and chronic pathogens seem to have exploited these pathways to achieve immune evasion. Furthermore, malfunction of the inhibitory arm of the immune response appears responsible for the development of multiple autoimmune pathologies. As a result, the negative regulators of T-cell activation have become attractive targets for therapeutic intervention in cancer, chronic infection, and autoimmune disease. The application of findings from basic research has provided insight into the manipulation of these pathways in the clinic and offers promising strategies for the treatment of disease. [ABSTRACT FROM AUTHOR]

Establishing a balance between the rapid generation of effective immunity and the production of overly exuberant or excessively prolonged responses is critical to the maintenance of the equilibrium between health and disease. The preservation of homeostasis and prevention of inappropriate activation of immunity is safeguarded by systems integrating the influences of T-cell receptor signaling, pro-inflammatory danger signals, and positive costimulatory signals on the one hand with those of several layers of both cell-intrinsic and cell-extrinsic inhibitory checkpoints on the other. Evolution has thus provided an immunological system capable of clearance of pathogens and infected cells but which generally avoids the severe collateral damage that is associated with failure to control immunity. Central tolerance to self-antigens constitutes the first line of defense against self-destruction. Because central tolerance mechanisms fail to eliminate all self-reactive immune effector cells, other immune-regulating (peripheral tolerance) mechanisms are required to prevent excessive immune responses. Dysfunction of these inhibitory pathways in terms of reduced activity can result in the unmasking of self-directed responses and a variety of autoimmune morbidities. Conversely, enhanced inhibitory activity can restrict the generation of clinically useful immunity to cancers and to chronic infectious pathogens. This may manifest not only as inhibition of immunity directed towards what are largely aberrantly or overexpressed ‘self’ targets on malignant cells but also additional exaggeration of inhibitory pathway activity mediated via upregulation on tumor cells or stromal tissues of the ligands for inhibitory receptors expressed by lymphocytes. The selective pressures exerted by immuno-editing will favor the outgrowth of such immuno-evasive malignant clones. These pathways therefore represent significant hurdles to the generation of therapeutic anti-cancer responses. The most active of the T-cell intrinsic inhibitory pathways belong to the immunoglobulin superfamily, which occupies a central importance in the coordination of immune responses. The CD28/cytotoxic T-lymphocyte antigen-4 (CTLA-4):B7-1/B7-2 receptor/ligand grouping represents the archetypal example of these immune regulators. Therapies aimed at overcoming these mechanisms of peripheral tolerance, in particular by blocking the inhibitory checkpoints, offer the potential to generate anti-tumor activity, either as monotherapies or in synergism with other therapies that directly or indirectly enhance presentation of tumor epitopes to the immune system. [ABSTRACT FROM AUTHOR]

In this Commentary we aim to provide an overview of some specific examples of cancer therapeutics, including targeted approaches using monoclonal antibodies and kinase inhibitors, as well as highlight novel approaches for enhancing immunological responses against tumors. We point out that a fundamental property of the cancer cell, genomic instability, confounds the targeted therapies that aim to induce cell death directly while simultaneously enhancing the potential for immunological attack by creating a large number of neoantigens. We argue for combinatorial strategies with agents that target tumor cells to release these antigens together with innovative therapies that enhance immunological responses by interfering with inhibitory checkpoints. [Copyright &y& Elsevier]

The discovery of multiple costimulatory cell surface molecules that influence the course oft cell activation has increased our appreciation of the complexity of the T cell response. It remains clear, however, that CD28 and cytotoxic T lymphocyte antigen 4 (CTLA-4) are the critical costimulatory receptors that determine the early outcome of stimulation through the T cell antigen receptor (TCR). Details of how the T cell integrates TCR stimulation with the costimulatory signals of CD28 and the inhibitory signals of CTLA-4 remain to be established, but unique features of the cell biology of CTLA-4 provide important insights into its function. We summarize here recent findings that suggest a previously unrecognized role for CTLA-4 in the regulation of T cell responses. We also describe preclinical and clinical results that indicate manipulation of CTLA-4 has considerable promise as a strategy for the immunotherapy of cancer. [ABSTRACT FROM AUTHOR]

Cancer immunotherapy has dramatically changed the approach to cancer treatment. The aim of targeting the immune system to recognize and destroy cancer cells has afforded many patients the prospect of achieving deep, long‐term remission and potential cures. However, many challenges remain for achieving the goal of effective immunotherapy for all cancer patients. Checkpoint inhibitors have been able to achieve long‐term responses in a minority of patients, yet improving response rates with combination therapies increases the possibility of toxicity. Chimeric antigen receptor T cells have demonstrated high response rates in hematological cancers, although most patients experience relapse. In addition, some cancers are notoriously immunologically "cold" and typically are not effective targets for immunotherapy. Overcoming these obstacles will require new strategies to improve upon the efficacy of current agents, identify biomarkers to select appropriate therapies, and discover new modalities to expand the accessibility of immunotherapy to additional tumor types and patient populations. [ABSTRACT FROM AUTHOR]

We report that cryoablation of primary tumors synergizes with anti-CTLA-4 treatment to mediate rejection of secondary tumors in the TRAMP mouse model of prostate cancer. T cells, in particular CD8+ T cells specific for the TRAMP antigen SPAS-1, were enriched in both secondary tumors and spleens of combination-treated mice. [ABSTRACT FROM AUTHOR]

Immune checkpoint blockade therapy targets T cell-negative costimulatory molecules such as cytotoxic T lymphocyte antigen-4 (CTLA-4) and programmed cell death-1 (PD-1). Combination anti- CTLA-4 and anti-PD-1 blockade therapy has enhanced efficacy, but it remains unclear through what mechanisms such effects are mediated. A critical question is whether combination therapy targets and modulates the same T cell populations as monotherapies. Using a mass cytometry-based systems approach, we comprehensively profiled the response of T cell populations to monotherapy and combination anti-CTLA-4 plus anti-PD-1 therapy in syngeneic murine tumors and clinical samples. Most effects of monotherapies were additive in the context of combination therapy; however, multiple combination therapy-specific effects were observed. Highly phenotypically exhausted cluster of differentiation 8 (CD8) T cells expand in frequency following anti-PD-1 monotherapy but not combination therapy, while activated terminally differentiated effector CD8 T cells expand only following combination therapy. Combination therapy also led to further increased frequency of T helper type 1 (Th1)-like CD4 effector T cells even though anti-PD-1 monotherapy is not sufficient to do so. Mass cytometry analyses of peripheral blood from melanoma patients treated with immune checkpoint blockade therapies similarly revealed mostly additive effects on the frequencies of T cell subsets along with unique modulation of terminally differentiated effector CD8 T cells by combination ipilimumab plus nivolumab therapy. Together, these findings indicate that dual blockade of CTLA-4 and PD-1 therapy is sufficient to induce unique cellular responses compared with either monotherapy. [ABSTRACT FROM AUTHOR]

Immune checkpoint (IC) therapy provides substantial benefits to cancer patients but can also cause distinctive toxicities termed immune-related adverse events (irAEs). Biomarkers to predict toxicities will be necessary to improve management of patients receiving IC therapy. We relied on serological analysis of recombinant cDNA expression libraries to evaluate plasma samples from patients treated with IC therapy and identified autoantibodies, both in pretreatment and on-treatment samples prior to the development of irAEs, which correlate with the development of immune-related hypophysitis (anti-GNAL and anti-ITM2B autoantibodies) and pneumonitis (anti-CD74 autoantibody). We developed an enzyme-linked immunosorbent assay and tested additional patient samples to confirm our initial findings. Collectively, our data suggest that autoantibodies may correlate with irAEs related to IC therapy, and specific autoantibodies may be detected early for the management of irAEs. [ABSTRACT FROM AUTHOR]

Enhancer of zeste homolog 2-mediated (EZH2-mediated) epigenetic regulation of T cell differentiation and Treg function has been described previously; however, the role of EZH2 in T cell-mediated antitumor immunity, especially in the context of immune checkpoint therapy, is not understood. Here, we showed that genetic depletion of EZH2 in Tregs (FoxP3creEZH2fl/fl mice) leads to robust antitumor immunity. In addition, pharmacological inhibition of EZH2 in human T cells using CPI-1205 elicited phenotypic and functional alterations of the Tregs and enhanced cytotoxic activity of Teffs. We observed that ipilimumab (anti-CTLA-4) increased EZH2 expression in peripheral T cells from treated patients. We hypothesized that inhibition of EZH2 expression in T cells would increase the effectiveness of anti-CTLA-4 therapy, which we tested in murine models. Collectively, our data demonstrated that modulating EZH2 expression in T cells can improve antitumor responses elicited by anti-CTLA-4 therapy, which provides a strong rationale for a combination trial of CPI-1205 plus ipilimumab. [ABSTRACT FROM AUTHOR]

Although strategies that block FOXP3-dependent regulatory T cell function (CTLA4 blockade) and the inhibitory receptor PD1 have shown great promise in promoting antitumor immune responses in humans, their widespread implementation for cancer immunotherapy has been hampered by significant off-target autoimmune side effects that can be lethal. Our work has shown that absence of OX40 and CD30 costimulatory signals prevents CD4 T cell-driven autoimmunity in Foxp3-deficient mice, suggesting a novel way to block these side effects. In this study, we show that excellent antitumor CD8 T cell responses can be achieved in Foxp3KO mice deficient in OX40 and CD30 signals, particularly in the presence of concurrent PD1 blockade. Furthermore, excellent antitumor immune responses can also be achieved using combinations of Abs that block CTLA4, PD1, OX40, and CD30 ligands, without CD4 T cell-driven autoimmunity. By dissociating autoimmune side effects from anticancer immune responses, this potentially shifts this antitumor approach to patients with far less advanced disease. [ABSTRACT FROM AUTHOR]

Immune checkpoint therapies, such as ipilimumab, induce dramatic antitumor responses in a subset of patients with advanced malignancies, but they may also induce inflammatory responses and toxicities termed immune-related adverse events (irAEs). These irAEs are often low grade and manageable, but severe irAEs may lead to prolonged hospitalizations or fatalities. Early intervention is necessary to minimize morbidities that occur with severe irAEs. However, correlative biomarkers are currently lacking. In a phase II clinical trial that treated 27 patients with metastatic prostate cancer, we aimed to test the safety and efficacy of androgen deprivation therapy plus ipilimumab. In this study, we observed grade 3 toxicities in >40% of treated patients, which led to early closure of the study. Because ipilimumab enhances T-cell responses, we hypothesized that increased clonal T-cell responses in the systemic circulation may contribute to irAEs. Sequencing of the T-cell receptor β-chains in purified T cells revealed clonal expansion of CD8 T cells, which occurred in blood samples collected before the onset of grade 2-3 irAEs. These initial results suggested that expansion of ≥55 CD8 T-cell clones preceded the development of severe irAEs. We further evaluated available blood samples from a second trial and determined that patients who experienced grade 2-3 irAEs also had expansion of ≥55 CD8 T-cell clones in blood samples collected before the onset of irAEs. We propose that CD8 T-cell clonal expansion may be a correlative biomarker to enable close monitoring and early intervention for patients receiving ipilimumab. [ABSTRACT FROM AUTHOR]

Background: Novel immunotherapies, or checkpoint inhibitors, targeting programmed cell death protein-1 (PD-1) and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) have significantly improved outcomes for patients with numerous different cancer types. However, owing to their exclusion from clinical trials and risk for autoimmune exacerbation on these treatments, the impact on safety and degree of toxicity of these potentially life-prolonging therapies is not well characterized in patients with an underlying autoimmune disease or previous organ transplant. Case presentation: We report a case of a patient with advanced melanoma and refractory Crohn’s disease who was treated concurrently with pembrolizumab (anti-PD-1 antibody) and tocilizumab (anti-interluekin-6 receptor antibody). This novel treatment strategy was well tolerated and did not result in Crohn’s disease exacerbation for at least 16 weeks. Importantly, this treatment resulted in marked, durable antitumor responses. Conclusions: This outcome suggests that targeted immunosuppression combined with checkpoint inhibitors may hold promise as a treatment strategy for this unique patient population and may warrant additional study. [ABSTRACT FROM AUTHOR]

A response by Rachel A. Gottschalk, Emily Corse and James P. Allison to a letter to the editor on article "Expression of Helios in Peripherally Induced Foxp3+ Regulatory T-Cells" published in this issue of the journal is presented.

Kidney fibrosis is marked by an epithelial-to-mesenchymal transition (EMT) of tubular epithelial cells (TECs). Here we find that, during renal fibrosis, TECs acquire a partial EMT program during which they remain associated with their basement membrane and express markers of both epithelial and mesenchymal cells. The functional consequence of the EMT program during fibrotic injury is an arrest in the G2 phase of the cell cycle and lower expression of several solute and solvent transporters in TECs. We also found that transgenic expression of either Twist1 (encoding twist family bHLH transcription factor 1, known as Twist) or Snai1 (encoding snail family zinc finger 1, known as Snail) expression is sufficient to promote prolonged TGF-β1-induced G2 arrest of TECs, limiting the cells' potential for repair and regeneration. In mouse models of experimentally induced renal fibrosis, conditional deletion of Twist1 or Snai1 in proximal TECs resulted in inhibition of the EMT program and the maintenance of TEC integrity, while also restoring cell proliferation, dedifferentiation-associated repair and regeneration of the kidney parenchyma and attenuating interstitial fibrosis. Thus, inhibition of the EMT program in TECs during chronic renal injury represents a potential anti-fibrosis therapy. [ABSTRACT FROM AUTHOR]

Members of the B7 family have been shown to be important for regulating immune responses by providing either positive or negative costimulatory signals. The function of B7-H3 has been controversial. We show that B7-H3 is upregulated in graft-versus-host disease (GVHD) target organs, including the colon, liver, and lung. Infusion of allogeneic donor T cells into B7-H3-/- vs wild-type (WT) recipients resulted in increased GVHD lethality associated with increased T-cell proliferation, colonic inflammatory cytokines, and destruction of epithelial barriers. Allogeneic B7-H3-/- vs WT donor T cells also had increased T-cell proliferation and GVHD lethality associated with increased proliferation and cytokine secretion in the spleen, intraepithelial lymphocyte inflammatory cytokines, and intestinal permeability. Both resting and activated regulatory T cells (Tregs) lack B7-H3 messenger RNA. Consistent with these data, GVHD was augmented in recipients of B7-H3-/- Treg-depleted grafts. In two delayed lymphocyte infusion (DLI) models, T cells lacking B7-H3 are capable of providing graft-versus-leukemia (GVL) effects. We conclude that B7-H3 is responsible for providing a negative costimulatory signal. Our studies provide support for developing and testing new therapies directed toward the B7-H3 pathway, including approaches to augment host B7-H3 early after bone marrow transplantation to prevent GVHD and to develop potent antagonistic antibodies later after transplant to facilitate DLl-mediated GVL without GVHD complications. [ABSTRACT FROM AUTHOR]

During primary Ag encounter, T cells receive numerous positive and negative signals that control their proliferation, function, and differentiation, but how these signals are integrated to modulate T cell memory has not been fully characterized. In these studies, we demonstrate that combining seemingly opposite signals, CTLA-4 blockade and rapamycin-mediated mammalian target of rapamycin inhibition, during in vivo T cell priming leads to both an increase in the frequency of memory CD8+ T cells and improved memory responses to tumors and bacterial challenges. This enhanced efficacy corresponds to increased early expansion and memory precursor differentiation of CD8+ T cells and increased mitochondrial biogenesis and spare respiratory capacity in memory CD8+ T cells in mice treated with anti-CTLA-4 and rapamycin during immunization. Collectively, these results reveal that mammalian target of rapamycin inhibition cooperates with rather than antagonizes blockade of CTLA-4, promoting unrestrained effector function and proliferation, and an optimal metabolic program for CD8+ T cell memory. [ABSTRACT FROM AUTHOR]

During primary Ag encounter, T cells receive numerous positive and negative signals that control their proliferation, function, and differentiation, but how these signals are integrated to modulate T cell memory has not been fully characterized. In these studies, we demonstrate that combining seemingly opposite signals, CTLA-4 blockade and rapamycin-mediated mammalian target of rapamycin inhibition, during in vivo T cell priming leads to both an increase in the frequency of memory CD8+ T cells and improved memory responses to tumors and bacterial challenges. This enhanced efficacy corresponds to increased early expansion and memory precursor differentiation of CD8+ T cells and increased mitochondrial biogenesis and spare respiratory capacity in memory CD8+ T cells in mice treated with anti-CTLA-4 and rapamycin during immunization. Collectively, these results reveal that mammalian target of rapamycin inhibition cooperates with rather than antagonizes blockade of CTLA-4, promoting unrestrained effector function and proliferation, and an optimal metabolic program for CD8+ T cell memory. [ABSTRACT FROM AUTHOR]

The immune system influences the fate of developing cancers by not only functioning as a tumour promoter that facilitates cellular transformation, promotes tumour growth and sculpts tumour cell immunogenicity, but also as an extrinsic tumour suppressor that either destroys developing tumours or restrains their expansion. Yet, clinically apparent cancers still arise in immunocompetent individuals in part as a consequence of cancer-induced immunosuppression. In many individuals, immunosuppression is mediated by cytotoxic T-lymphocyte associated antigen-4 (CTLA-4) and programmed death-1 (PD-1), two immunomodulatory receptors expressed on T cells. Monoclonal-antibody-based therapies targeting CTLA-4 and/or PD-1 (checkpoint blockade) have yielded significant clinical benefits-including durable responses-to patients with different malignancies. However, little is known about the identity of the tumour antigens that function as the targets of T cells activated by checkpoint blockade immunotherapy and whether these antigens can be used to generate vaccines that are highly tumour-specific. Here we use genomics and bioinformatics approaches to identify tumour-specific mutant proteins as a major class of T-cell rejection antigens following anti-PD-1 and/or anti-CTLA-4 therapy of mice bearing progressively growing sarcomas, and we show that therapeutic synthetic long-peptide vaccines incorporating these mutant epitopes induce tumour rejection comparably to checkpoint blockade immunotherapy. Although mutant tumour-antigen-specific T cells are present in progressively growing tumours, they are reactivated following treatment with anti-PD-1 and/or anti-CTLA-4 and display some overlapping but mostly treatment-specific transcriptional profiles, rendering them capable of mediating tumour rejection. These results reveal that tumour-specific mutant antigens are not only important targets of checkpoint blockade therapy, but they can also be used to develop personalized cancer-specific vaccines and to probe the mechanistic underpinnings of different checkpoint blockade treatments. [ABSTRACT FROM AUTHOR]

Summary: Pancreatic ductal adenocarcinoma (PDAC) is associated with marked fibrosis and stromal myofibroblasts, but their functional contribution remains unknown. Transgenic mice with the ability to delete αSMA+ myofibroblasts in pancreatic cancer were generated. Depletion starting at either noninvasive precursor (pancreatic intraepithelial neoplasia) or the PDAC stage led to invasive, undifferentiated tumors with enhanced hypoxia, epithelial-to-mesenchymal transition, and cancer stem cells, with diminished animal survival. In PDAC patients, fewer myofibroblasts in their tumors also correlated with reduced survival. Suppressed immune surveillance with increased CD4+Foxp3+ Tregs was observed in myofibroblast-depleted mouse tumors. Although myofibroblast-depleted tumors did not respond to gemcitabine, anti-CTLA4 immunotherapy reversed disease acceleration and prolonged animal survival. This study underscores the need for caution in targeting carcinoma-associated fibroblasts in PDAC. [ABSTRACT FROM AUTHOR]

Ipilimumab is the prototypical immunomodulatory antibody, approved by the FDA in 2011 for advanced melanoma on the basis of survival benefit. Since that time, we have made significant strides in optimizing this therapy: we have characterized the spectrum of immune-related adverse events and learned how to mitigate them with treatment algorithms, discovered potential biomarkers of activity, and identified the potential synergy between checkpoint modulation and other therapeutic modalities. Recent phase I trials have established the efficacy and safety of next-generation checkpoint agents, including PD-1 and PD-L1 inhibitors, across multiple tumor types. Much work lies ahead in developing these next-generation checkpoint agents, testing them in combination, and determining how to integrate them into the treatment paradigms of various tumor types. [ABSTRACT FROM AUTHOR]

The immunotherapeutic agent ipilimumab has helped address a significant unmet need in the treatment of advanced melanoma. Ipilimumab is a fully human monoclonal antibody that targets cytotoxic T-lymphocyte antigen-4 (CTLA-4), thereby augmenting antitumor immune responses. After decades in which a number of clinical trials were conducted, ipilimumab was the first therapy to improve overall survival in a randomized, controlled phase III trial of patients with advanced melanoma. These results led to the regulatory approval of ipilimumab at 3 mg/kg for the treatment of unresectable or metastatic melanoma. More than 17,000 patients worldwide have received ipilimumab, either as a commercial drug at 3 mg/kg or in clinical trials and expanded access programs at different doses. Consistent with its proposed mechanism of action, the most common toxicities associated with ipilimumab therapy are inflammatory in nature. These immune-related adverse events were mostly reversible when effective treatment guidelines were followed. Importantly, long-term follow-up of patients who received ipilimumab in a phase III trial showed that 24% survived at least two years, and in phase II studies, a proportion of patients survived at least five years. Evaluation of ipilimumab is ongoing in the adjuvant setting for melanoma, and for advanced disease in nonsmall cell lung, small cell lung, prostate, ovarian, and gastric cancers. [ABSTRACT FROM AUTHOR]

Despite considerable interest in the modulation of tumor-associated Foxp3+ regulatory T cells (Tregs) for therapeutic benefit, little is known about the developmental origins of these cells and the nature of the antigens that they recognize. We identified an endogenous population of antigen-specific Tregs (termed MJ23 Tregs) found recurrently enriched in the tumors of mice with oncogene-driven prostate cancer. MJ23 Tregs were not reactive to a tumor-specific antigen but instead recognized a prostate-associated antigen that was present in tumor-free mice. MJ23 Tregs underwent autoimmune regulator (Aire)-dependent thymic development in both mate and female mice. Thus, Aire-mediated expression of peripheral tissue antigens drives the thymic development of a subset of organ-specific Tregs, which are likely coopted by tumors developing within the associated organ. [ABSTRACT FROM AUTHOR]

Inflammation of the normally tolerant liver microen-vironment precedes the development of chronic liver disease. Study of the pathogenesis of autoimmune liver diseases, such as autoimmune hepatitis (AIH), has been hampered by a lack of autochthonous chronic animal models. Through our studies of T cell costimulation, we generated transgenic mice expressing a ligand specific for the CD28 receptor, which normally shares ligands with the related inhibitory receptor CTLA-4. The mice spontaneously develop chronic inflammatory liver dis-ease with several pathologies found in AIH, including elevated serum aminotransferases in the context of nor-mal alkaline phosphatase and bilirubin levels, lympho-cytic inflammation, focal necrosis, oval cell hyperplasia, and fibrosis. The prevalence of IFN-7--producing CD8+ T cells in the livers of transgenic mice suggests a role for autoimmune cytotoxicity in the chronic disease state. The CD28 ligand-specific transgenic mice will facilitate evaluation of CD8+ T cell function in liver disease pa-thologies found in AIH. [ABSTRACT FROM AUTHOR]

B7x (B7-H4 or B7S1) is the seventh member of the B7 family, and its in vivo function remains largely unknown. Despite new genetic data linking the B7x gene with autoimmune diseases, how exactly it contributes to peripheral tolerance and autoimmunity is unclear. In this study, we showed that B7x protein was not detected on APCs or β cells in both human and mice, which is unique in the B7 family. Because B7x protein is expressed in some peripheral cells such as pancreatic β cells, we used a CD8 T cell-mediated diabetes model (A14αβP) in which CD8 T cells recognize an endogenous self-Ag, and found that mice lacking B7x developed more severe diabetes than control AI4aP mice. Conversely, mice overexpressing B7x in the β cells (Rip-B7xA14αβ) were diabetes free. Furthermore, adoptive transfer of effector A14αβ CD8 T cells induced diabetes in control mice, but not in Rip-B7xA14αβ mice. Mechanistic studies revealed that pathogenic effector CD8 T cells were capable of migrating to the pancreas but failed to robustly destroy tissue when encountering local B7x in Rip-B7xA14αβ mice. Although A14αβ CD8 T cells in Rip-B7xA14αβ and A14αβ mice showed similar cytotoxic function, cell death, and global gene expression profiles, these cells had greater proliferation in A14αβ mice than in RIP-B7xAαβ mice. These results suggest that B7x in nonlymphoid organs prevents peripheral autoim-munity partially through inhibiting proliferation of tissue-specific CD8 T cells, and that local overexpression of B7x on pancreatic β cells is sufficient to abolish CD8 T cell-induced diabetes. [ABSTRACT FROM AUTHOR]

IL-15 has potential as an immunotherapeutic agent for cancer treatment because it is a critical factor for the proliferation and activation of NK and CD8+ T cells. However, monotherapy of patients with malignancy with IL-15 that has been initiated may not be optimal, because of the limited expression of the private receptor, IL-15Rα. We demonstrated greater CD8 T cell-mediated therapeutic efficacy using a combination regimen of murine IL-15 administered with an agonistic anti-CD40 Ab (FGK4.5) that led to increased IL-15Rα expression on dendritic cells (DCs), as well as other cell types, in a syngeneic established TRAMP-C2 tumor model. Seventy to one hundred percent of TRAMP-C2 tumor-bearing wild-type C57BL/6 mice in the combination group manifested sustained remissions, whereas only 0-30% in the anti-CD40-alone group and none in the murine IL-15-alone group became tumor free (p < 0.001). However, the combination regimen showed less efficacy in TRAMP-C2 tumor-bearing IL-15Rα-/- mice than in wild-type mice. The combination regimen significantly increased the numbers of TRAMP-C2 tumor-specific SPAS-1/SNC9-H8 tetramer+CD8+ T cells, which were associated with the protection from tumor development on rechallenge with TRAMP-C2 tumor cells. Using an in vitro cytolytic assay that involved NK cells primed by wild-type or IL-15Rα-/- bone marrow-derived DCs, we demonstrated that the expression of IL-15Rα by DCs appeared to be required for optimal IL-15-induced NK priming and killing. These findings support the view that anti-CD40-mediated augmented IL-15Rα expression was critical in IL-15-associated sustained remissions observed in TRAMP-C2 tumor-bearing mice receiving combination therapy. [ABSTRACT FROM AUTHOR]