The nature of activatory and tolerogenic dendritic cell-derived signal II

Factor of time in dendritic cell (DC) maturation: short-term activation of DCs significantly improves type 1 cytokine production and T cell responses

Dendritic cells (DCs) have been intensively studied in correlation to tumor immunology and for the development DC-based cancer vaccines. Here, we present the significance of the temporal aspect of DC maturation for the most essential subsequent timepoint, namely at interaction with responding T cells or after CD40-Ligand restimulation. Mostly, DC maturation is still being achieved by activation processes which lasts 24 h to 48 h. We hypothesized this amount of time is excessive from a biological standpoint and could be the underlying cause for functional exhaustion. Indeed, shorter maturation periods resulted in extensive capacity of monocyte-derived DCs to produce inflammatory cytokines after re-stimulation with CD40-Ligand. This effect was most evident for the primary type 1 polarizing cytokine, IL-12p70. This capacity reached peak at 6 h and dropped sharply with longer exposure to initial maturation stimuli (up to 48 h). The 6 h maturation protocol reflected superiority in subsequent functionality tests. Namely, DCs displayed twice the allostimulatory capacity of 24 h- and 48 h-matured DCs. Similarly, type 1 T cell response measured by IFN-γ production was 3-fold higher when CD4+ T cells had been stimulated with shortly matured DC and over 8-fold greater in case of CD8+ T cells, compared to longer matured DCs. The extent of melanoma-specific CD8+ cytotoxic T cell induction was also greater in case of 6 h DC maturation. The major limitation of the study is that it lacks in vivo evidence, which we aim to examine in the future. Our findings show an unexpectedly significant impact of temporal exposure to activation signals for subsequent DC functionality, which we believe can be readily integrated into existing knowledge on in vitro/ex vivo DC manipulation for various uses. We also believe this has important implications for DC vaccine design for future clinical trials.

Emerging strategies for treating autoimmune disease with genetically modified dendritic cells

Gene editing of living cells has become a crucial tool in medical research, enabling scientists to address fundamental biological questions and develop novel strategies for disease treatment. This technology has particularly revolutionized adoptive transfer cell therapy products, leading to significant advancements in tumor treatment and offering promising outcomes in managing transplant rejection, autoimmune disorders, and inflammatory diseases. While recent clinical trials have demonstrated the safety of tolerogenic dendritic cell (TolDC) immunotherapy, concerns remain regarding its effectiveness. This review aims to discuss the application of gene editing techniques to enhance the tolerance function of dendritic cells (DCs), with a particular focus on preclinical strategies that are currently being investigated to optimize the tolerogenic phenotype and function of DCs. We explore potential approaches for in vitro generation of TolDCs and provide an overview of emerging strategies for modifying DCs. Additionally, we highlight the primary challenges hindering the clinical adoption of TolDC therapeutics and propose future research directions in this field.

Nanomedicine for T-Cell Mediated Immunotherapy

T-cell immunotherapy offers outstanding advantages in the treatment of various diseases, and with the selection of appropriate targets, efficient disease treatment can be achieved. T-cell immunotherapy has made great progress, but clinical results show that only a small proportion of patients can benefit from T-cell immunotherapy. The extensive mechanistic work outlines a blueprint for using T cells as a new option for immunotherapy, but also presents new challenges, including the balance between different fractions of T cells, the inherent T-cell suppression patterns in the disease microenvironment, the acquired loss of targets, and the decline of T-cell viability. The diversity, flexibility, and intelligence of nanomedicines give them great potential for enhancing T-cell immunotherapy. Here, how T-cell immunotherapy strategies can be adapted with different nanomaterials to enhance therapeutic efficacy is discussed. For two different pathological states, immunosuppression and immune activation, recent advances in nanomedicines for T-cell immunotherapy in diseases such as cancers, rheumatoid arthritis, systemic lupus erythematosus, ulcerative colitis, and diabetes are summarized. With a focus on T-cell immunotherapy, this review highlights the outstanding advantages of nanomedicines in disease treatment, and helps advance one's understanding of the use of nanotechnology to enhance T-cell immunotherapy.

Ginger-derived bioactive compounds attenuate the Toll-like receptor mediated responses of human dendritic cells

Ginger has been used for thousands of years for the treatment of many illnesses, from nausea to migraines. Recently, an interest has grown in ginger compounds in the context of autoimmune and inflammatory diseases due to their significant anti-inflammatory effects. Nevertheless, the effects and mechanism of action of these phytochemicals in human immune cells, particularly in dendritic cells (DCs) are unclear. In the present study, we investigated the effects of 6-gingerol and 6-shogaol, the major compounds found in ginger rhizome, on the functionality of primary human monocyte-derived DCs (moDCs). Here we report for the first time that 6-gingerol and 6-shogaol dampen the immunogenicity of human DCs by inhibiting their activation, cytokine production and T cell stimulatory ability. In particular, the bioactive compounds of ginger dose-dependently inhibited the upregulation of activation markers, and the production of different cytokines in response to synthetic Toll-like receptor (TLR) ligands. Moreover, both compounds could significantly reduce the Escherichia coli-triggered cytokine production and T cell stimulatory capacity of moDCs. We also provide evidence that the ginger-derived compounds attenuate DC functionality via inhibiting the nuclear factor-κB (NF-kB), mitogen activated protein kinase (MAPK), and mammalian target of rapamycin (mTOR) signaling cascades. Further, 6-shogaol but not 6-gingerol activates the AMP-activated protein kinase (AMPK) and nuclear factor erythroid 2-related factor 2 (NRF2) pathways that might contribute to its anti-inflammatory action. Altogether, our results indicate that ginger-derived phytochemicals exert their anti-inflammatory activities via multiple mechanisms and suggest that 6-shogaol is more potent in its ability to suppress DC functionality than 6-gingerol.

Peptide nanovaccine in melanoma immunotherapy

Melanoma is an especially fatal neoplasm resistant to traditional treatment. The advancement of novel therapeutical approaches has gained attention in recent years by shedding light on the molecular mechanisms of melanoma tumorigenesis and their powerful interplay with the immune system. The presence of many mutations in melanoma cells results in the production of a varied array of antigens. These antigens can be recognized by the immune system, thereby enabling it to distinguish between tumors and healthy cells. In the context of peptide cancer vaccines, generally, they are designed based on tumor antigens that stimulate immunity through antigen-presenting cells (APCs). As naked peptides often have low potential in eliciting a desirable immune reaction, immunization with such compounds usually necessitates adjuvants and nanocarriers. Actually, nanoparticles (NPs) can provide a robust immune response to peptide-based melanoma vaccines. They improve the directing of peptide vaccines to APCs and induce the secretion of cytokines to get maximum immune response. This review provides an overview of the current knowledge of the utilization of nanotechnology in peptide vaccines emphasizing melanoma, as well as highlights the significance of physicochemical properties in determining the fate of these nanovaccines in vivo, including their drainage to lymph nodes, cellular uptake, and influence on immune responses.

IL-10-Engineered Dendritic Cells Modulate Allogeneic CD8+ T Cell Responses

Tolerogenic dendritic cells (tolDC) play a central role in regulating immune homeostasis and in promoting peripheral tolerance. These features render tolDC a promising tool for cell-based approaches aimed at inducing tolerance in T-cell mediated diseases and in allogeneic transplantation. We developed a protocol to generate genetically engineered human tolDC overexpressing IL-10 (DC^IL-10) by means of a bidirectional lentiviral vector (LV) encoding for IL-10. DC^IL-10 promote allo-specific T regulatory type 1 (Tr1) cells, modulate allogeneic CD4⁺ T cell responses in vitro and in vivo, and are stable in a pro-inflammatory milieu. In the present study, we investigated the ability of DC^IL-10 to modulate cytotoxic CD8⁺ T cell responses. We demonstrate that DC^IL-10 reduces allogeneic CD8⁺ T cell proliferation and activation in primary mixed lymphocyte reactions (MLR). Moreover, long-term stimulation with DC^IL-10 induces allo-specific anergic CD8⁺ T cells without signs of exhaustion. DC^IL-10-primed CD8⁺ T cells display limited cytotoxic activity. These findings indicate that stable over-expression of IL-10 in human DC leads to a population of cells able to modulate cytotoxic allogeneic CD8⁺ T cell responses, overall indicating that DC^IL-10 represent a promising cellular product for clinical applications aimed at inducing tolerance after transplantation.

A flexible liposomal polymer complex as a platform of specific and regulable immune regulation for individual cancer immunotherapy

BACKGROUND

The applicability and therapeutic efficacy of specific personalized immunotherapy for cancer patients is limited by the genetic diversity of the host or the tumor. Side-effects such as immune-related adverse events (IRAEs) derived from the administration of immunotherapy have also been observed. Therefore, regulatory immunotherapy is required for cancer patients and should be developed.

METHODS

The cationic lipo-PEG-PEI complex (LPPC) can stably and irreplaceably adsorb various proteins on its surface without covalent linkage, and the bound proteins maintain their original functions. In this study, LPPC was developed as an immunoregulatory platform for personalized immunotherapy for tumors to address the barriers related to the heterogenetic characteristics of MHC molecules or tumor associated antigens (TAAs) in the patient population. Here, the immune-suppressive and highly metastatic melanoma, B16F10 cells were used to examine the effects of this platform. Adsorption of anti-CD3 antibodies, HLA-A2/peptide, or dendritic cells' membrane proteins (MP) could flexibly provide pan-T-cell responses, specific Th1 responses, or specific Th1 and Th2 responses, depending on the host needs. Furthermore, with regulatory antibodies, the immuno-LPPC complex properly mediated immune responses by adsorbing positive or negative antibodies, such as anti-CD28 or anti-CTLA4 antibodies.

RESULTS

The results clearly showed that treatment with LPPC/MP/CD28 complexes activated specific Th1 and Th2 responses, including cytokine release, CTL and prevented T-cell apoptosis. Moreover, LPPC/MP/CD28 complexes could eliminate metastatic B16F10 melanoma cells in the lung more efficiently than LPPC/MP. Interestingly, the melanoma resistance of mice treated with LPPC/MP/CD28 complexes would be reversed to susceptible after administration with LPPC/MP/CTLA4 complexes. NGS data revealed that LPPC/MP/CD28 complexes could enhance the gene expression of cytokine and chemokine pathways to strengthen immune activation than LPPC/MP, and that LPPC/MP/CTLA4 could abolish the LPPC/MP complex-mediated gene expression back to un-treatment.

CONCLUSIONS

Overall, we proved a convenient and flexible immunotherapy platform for developing personalized cancer therapy.

Metabolic regulation of dendritic cell activation and immune function during inflammation

Dendritic cells (DCs) are antigen-presenting cells that bridge innate and adaptive immune responses. Multiple cell types, including DCs, rely on cellular metabolism to determine their fate. DCs substantially alter cellular metabolic pathways during activation, such as oxidative phosphorylation, glycolysis, fatty acid and amino acid metabolism, which have crucial implications for their functionality. In this review, we summarize and discuss recent progress in DC metabolic studies, focusing on how metabolic reprogramming influences DC activation and functionality and the potential metabolic differences among DC subsets. Improving the understanding of the relationship between DC biology and metabolic regulation may provide promising therapeutic targets for immune-mediated inflammatory diseases.

A Microfluidic Approach for Probing Heterogeneity in Cytotoxic T-Cells by Cell Pairing in Hydrogel Droplets

Cytotoxic T-cells (CTLs) exhibit strong effector functions to leverage antigen-specific anti-tumoral and anti-viral immunity. When naïve CTLs are activated by antigen-presenting cells (APCs) they display various levels of functional heterogeneity. To investigate this, we developed a single-cell droplet microfluidics platform that allows for deciphering single CTL activation profiles by multi-parameter analysis. We identified and correlated functional heterogeneity based on secretion profiles of IFNγ, TNFα, IL-2, and CD69 and CD25 surface marker expression levels. Furthermore, we strengthened our approach by incorporating low-melting agarose to encapsulate pairs of single CTLs and artificial APCs in hydrogel droplets, thereby preserving spatial information over cell pairs. This approach provides a robust tool for high-throughput and single-cell analysis of CTLs compatible with flow cytometry for subsequent analysis and sorting. The ability to score CTL quality, combined with various potential downstream analyses, could pave the way for the selection of potent CTLs for cell-based therapeutic strategies.

Bromodomain Inhibitors Modulate FcγR-Mediated Mononuclear Phagocyte Activation and Chemotaxis

IgG antibodies form immune complexes (IC) that propagate inflammation and tissue damage in autoimmune diseases such as systemic lupus erythematosus. IgG IC engage Fcγ receptors (FcγR) on mononuclear phagocytes (MNP), leading to widespread changes in gene expression that mediate antibody effector function. Bromodomain and extra-terminal domain (BET) proteins are involved in governing gene transcription. We investigated the capacity of BET protein inhibitors (iBET) to alter IgG FcγR-mediated MNP activation. We found that iBET dampened IgG IC-induced pro-inflammatory gene expression and decreased activating FcγR expression on MNPs, reducing their ability to respond to IgG IC. Despite FcγR downregulation, iBET-treated macrophages demonstrated increased phagocytosis of protein antigen, IgG IC, and apoptotic cells. iBET also altered cell morphology, generating more amoeboid MNPs with reduced adhesion. iBET treatment impaired chemotaxis towards a CCL19 gradient in IC-stimulated dendritic cells (DC) in vitro, and inhibited IC-induced DC migration to draining lymph nodes in vivo, in a DC-intrinsic manner. Altogether, our data show that iBET modulates FcγR-mediated MNP activation and migration, revealing the therapeutic potential of BET protein inhibition in antibody-mediated diseases.

JAK1 signaling in dendritic cells promotes peripheral tolerance in autoimmunity through PD-L1-mediated regulatory T cell induction

Dendritic cells (DCs) induce peripheral T cell tolerance, but cell-intrinsic signaling cascades governing their stable tolerogenesis remain poorly defined. Janus Kinase 1 (JAK1) transduces cytokine-receptor signaling, and JAK inhibitors (Jakinibs), including JAK1-specific filgotinib, break inflammatory cycles in autoimmunity. Here, we report in heterogeneous DC populations of multiple secondary lymphoid organs that JAK1 promotes peripheral T cell tolerance during experimental autoimmune encephalomyelitis (EAE). Mice harboring DC-specific JAK1 deletion exhibit elevated peripheral CD4+ T cell expansion, less regulatory T cells (Tregs), and worse EAE outcomes, whereas adoptive DC transfer ameliorates EAE pathogenesis by inducing peripheral Tregs, programmed cell death ligand 1 (PD-L1) dependently. This tolerogenic program is substantially reduced upon the transfer of JAK1-deficient DCs. DC-intrinsic IFN-γ-JAK1-STAT1 signaling induces PD-L1, which is required for DCs to convert CD4+ T cells into Tregs in vitro and attenuated upon JAK1 deficiency and filgotinib treatment. Thus, DC-intrinsic JAK1 promotes peripheral tolerance, suggesting potential unwarranted DC-mediated effects of Jakinibs in autoimmune diseases.

Myeloid and Mesenchymal Stem Cell Therapies for Solid Organ Transplant Tolerance

Transplantation is now performed globally as a routine procedure. However, the increased demand for donor organs and consequent expansion of donor criteria has created an imperative to maximize the quality of these gains. The goal is to balance preservation of allograft function against patient quality-of-life, despite exposure to long-term immunosuppression. Elimination of immunosuppressive therapy to avoid drug toxicity, with concurrent acceptance of the allograft-so-called operational tolerance-has proven elusive. The lack of recent advances in immunomodulatory drug development, together with advances in immunotherapy in oncology, has prompted interest in cell-based therapies to control the alloimmune response. Extensive experimental work in animals has characterized regulatory immune cell populations that can induce and maintain tolerance, demonstrating that their adoptive transfer can promote donor-specific tolerance. An extension of this large body of work has resulted in protocols for manufacture, as well as early-phase safety and feasibility trials for many regulatory cell types. Despite the excitement generated by early clinical trials in autoimmune diseases and organ transplantation, there is as yet no clinically validated, approved regulatory cell therapy for transplantation. In this review, we summarize recent advances in this field, with a focus on myeloid and mesenchymal cell therapies, including current understanding of the mechanisms of action of regulatory immune cells, and clinical trials in organ transplantation using these cells as therapeutics.

Mechanisms of Immune Checkpoint Inhibitor-Mediated Colitis

Immune checkpoint inhibitors (ICIs) have provided tremendous clinical benefit in several cancer types. However, systemic activation of the immune system also leads to several immune-related adverse events. Of these, ICI-mediated colitis (IMC) occurs frequently and is the one with the highest absolute fatality. To improve current treatment strategies, it is important to understand the cellular mechanisms that induce this form of colitis. In this review, we discuss important pathways that are altered in IMC in mouse models and in human colon biopsy samples. This reveals a complex interplay between several types of immune cells and the gut microbiome. In addition to a mechanistic understanding, patients at risk should be identifiable before ICI therapy. Here we propose to focus on T-cell subsets that interact with bacteria after inducing epithelial damage. Especially, intestinal resident immune cells are of interest. This may lead to a better understanding of IMC and provides opportunities for prevention and management.

Adoptive transfer of GRP78-treated dendritic cells alleviates insulitis in NOD mice

The 78-kDa glucose-regulated protein (GRP78) has extracellular, anti-inflammatory properties that can aid resolving inflammation. It has been established previously that GRP78 induced myeloid CD11c⁺ cell differentiation into distinct tolerogenic cells. This tolerance induction makes GRP78 a potential therapeutic agent for transplanted allogeneic grafts and autoimmune diseases, such as type 1 diabetes. In this research, it is revealed that rmGRP78-treated NOD mice bone marrow-derived CD11c⁺ cells (GRP78-DCs) highly expressed B7-H4 but down-regulated CD86 and CD40, and retained a tolerogenic signature even after stimulation by LPS. In the assessment of in vivo therapeutic efficacy after the adoptive transfer of GRP78-DCs into NOD mice, fluorescent imaging analyses revealed that the transfer specifically homed in inflamed pancreases, promoting β-cell survival and alleviating insulitis in NOD mice. The adoptive transfer of GRP78-DCs also helped reduce Th1, Th17, and CTL, suppressing inflammatory cytokine production in vivo. The findings suggest that adoptive GRP78-DC transfer is critical to resolving inflammation in NOD mice and may have relevance in a clinical setting.

Peptide-HLA-based immunotherapeutics platforms for direct modulation of antigen-specific T cells

Targeted pharmacologic activation of antigen-specific (AgS) T cells may bypass limitations inherent in current T cell-based cancer therapies. We describe two immunotherapeutics platforms for selective delivery of costimulatory ligands and peptide-HLA (pHLA) to AgS T cells. We engineered and deployed on these platforms an affinity-attenuated variant of interleukin-2, which selectively expands oligoclonal and polyfunctional AgS T cells in vitro and synergizes with CD80 signals for superior proliferation versus peptide stimulation.

Regulatory T Cell-Enhancing Therapies to Treat Atherosclerosis

Experimental studies have provided strong evidence that chronic inflammation triggered by the sub-endothelial accumulation of cholesterol-rich lipoproteins in arteries is essential in the initiation and progression of atherosclerosis. Recent clinical trials highlighting the efficacy of anti-inflammatory therapies in coronary patients have confirmed that this is also true in humans Monocytes/macrophages are central cells in the atherosclerotic process, but adaptive immunity, through B and T lymphocytes, as well as dendritic cells, also modulates the progression of the disease. Analysis of the role of different T cell subpopulations in murine models of atherosclerosis identified effector Th1 cells as proatherogenic, whereas regulatory T cells (Tregs) have been shown to protect against atherosclerosis. For these reasons, better understanding of how Tregs influence the atherosclerotic process is believed to provide novel Treg-targeted therapies to combat atherosclerosis. This review article summarizes current knowledge about the role of Tregs in atherosclerosis and discusses ways to enhance their function as novel immunomodulatory therapeutic approaches against cardiovascular disease.

Modulating the wayward T cell: New horizons with immune checkpoint inhibitor treatments in autoimmunity, transplant, and cancer

The T-cell response is regulated by the balance between costimulatory and coinhibitory signals. Immune checkpoints are essential for efficient T-cell activation, but also for maintaining self-tolerance and protecting tissues from damage caused by the immune system, and for providing protective immunity. Modulating immune checkpoints can serve diametric goals, such that blocking a coinhibitory molecule can unleash anti-cancer immunity whereas stimulating the same molecule can reduce an over-reaction in autoimmune disease. The purpose of this review is to examine the regulation of T-cell costimulation and coinhibition, which is central to the processes underpinning autoimmunity, transplant rejection and immune evasion in cancer. We will focus on the immunomodulation agents that regulate these unwanted over- and under-reactions. The use of such agents has led to control of symptoms and slowing of progression in patients with rheumatoid arthritis, reduced rejection rates in transplant patients, and prolonged survival in patients with cancer. The management of immune checkpoint inhibitor treatment in certain challenging patient populations, including patients with pre-existing autoimmune conditions or transplant patients who develop cancer, as well as the management of immune-related adverse events in patients receiving antitumor therapy, is examined. Finally, the future of immune checkpoint inhibitors, including examples of emerging targets that are currently in development, as well as recent insights gained using new molecular techniques, is discussed. T-cell costimulation and coinhibition play vital roles in these diverse therapeutic areas. Targeting immune checkpoints continues to be a powerful avenue for the development of agents suitable for treating autoimmune diseases and cancers and for improving transplant outcomes. Enhanced collaboration between therapy area specialists to share learnings across disciplines will improve our understanding of the opposing effects of treatments for autoimmune disease/transplant rejection versus cancer on immune checkpoints, which has the potential to lead to improved patient outcomes.

Time-dependent LPS exposure commands MSC immunoplasticity through TLR4 activation leading to opposite therapeutic outcome in EAE

Background

Mesenchymal stem cells (MSCs) have been recognized for their regenerative and anti-inflammatory capacity which makes them very attractive to cell therapy, especially those ones to treat inflammatory and autoimmune disease. Two different immune-phenotypes have been described for MSCs depending on which Toll-like receptor (TLR) is activated. MSC1 is endowed with a pro-inflammatory phenotype following TLR4 activation with LPS. On the other hand, anti-inflammatory MSC2 is induced by the activation of TLR3 with Poly(I:C). High immunoplasticity of MSCs is a matter of concern in cell-based therapies. In this study, we investigated whether a single stimulus can induce both types of MSCs through a differential activation of TLR4 with LPS.

Methods

MSCs were activated with LPS following a short exposure of 1-h (MSCs-LPS1h) or long-time exposure for 48 h (MSCs-LPS48h), and then, we evaluated the biological response in vitro, the immunosuppressive capacity of MSCs in vitro, and the therapeutic potential of MSCs in an experimental autoimmune encephalomyelitis (EAE) mouse model.

Results

Our results showed that 1-h LPS exposure induced a MSC1 phenotype. Indeed, MSCs-LPS1h expressed low levels of NO/iNOS and decreased immunosuppressive capacity in vitro without therapeutic effect in the EAE model. In contrast, MSCs-LPS48h achieved a MSC2-like phenotype with significant increase in the immunosuppressive capacity on T cell proliferation in vitro, together with an improved in the therapeutic effect and higher Treg, compared to unstimulated MSCs. Furthermore, we determine through the MSCs-TLR4KO that the expression of TLR4 receptor is essential for MSCs’ suppressive activity since TLR4 deletion was associated with a diminished suppressive effect in vitro and a loss of therapeutic effect in vivo.

Conclusions

We demonstrate that MSCs display a high immunoplasticity commanded by a single stimulus, where LPS exposure time regulated the MSC suppressive effect leading into either an enhanced or an impairment therapeutic activity. Our results underscore the importance of phenotype conversion probably related to the TLR4 expression and activation, in the design of future clinical protocols to treat patients with inflammatory and autoimmune diseases.

Donor myeloid derived suppressor cells (MDSCs) prolong allogeneic cardiac graft survival through programming of recipient myeloid cells in vivo

Solid organ transplantation is a lifesaving therapy for patients with end-organ disease. Current immunosuppression protocols are not designed to target antigen-specific alloimmunity and are uncapable of preventing chronic allograft injury. As myeloid-derived suppressor cells (MDSCs) are potent immunoregulatory cells, we tested whether donor-derived MDSCs can protect heart transplant allografts in an antigen-specific manner. C57BL/6 (H2K^b, I-A^b) recipients pre-treated with BALB/c MDSCs were transplanted with either donor-type (BALB/c, H2K^d, I-A^d) or third-party (C3H, H2K^k, I-A^k) cardiac grafts. Spleens and allografts from C57BL/6 recipients were harvested for immune phenotyping, transcriptomic profiling and functional assays. Single injection of donor-derived MDSCs significantly prolonged the fully MHC mismatched allogeneic cardiac graft survival in a donor-specific fashion. Transcriptomic analysis of allografts harvested from donor-derived MDSCs treated recipients showed down-regulated proinflammatory cytokines. Immune phenotyping showed that the donor MDSCs administration suppressed effector T cells in recipients. Interestingly, significant increase in recipient endogenous CD11b⁺Gr1⁺ MDSC population was observed in the group treated with donor-derived MDSCs compared to the control groups. Depletion of this endogenous MDSCs with anti-Gr1 antibody reversed donor MDSCs-mediated allograft protection. Furthermore, we observed that the allogeneic mixed lymphocytes reaction was suppressed in the presence of CD11b⁺Gr1⁺ MDSCs in a donor-specific manner. Donor-derived MDSCs prolong cardiac allograft survival in a donor-specific manner via induction of recipient's endogenous MDSCs.

A role for TNF-α in alveolar macrophage damage-associated molecular pattern release

Chronic beryllium disease (CBD) is a metal hypersensitivity/autoimmune disease in which damage-associated molecular patterns (DAMPs) promote a break in T cell tolerance and expansion of Be2+/self-peptide-reactive CD4+ T cells. In this study, we investigated the mechanism of cell death induced by beryllium particles in alveolar macrophages (AMs) and its impact on DAMP release. We found that phagocytosis of Be led to AM cell death independent of caspase, receptor-interacting protein kinases 1 and 3, or ROS activity. Before cell death, Be-exposed AMs secreted TNF-α that boosted intracellular stores of IL-1α followed by caspase-8-dependent fragmentation of DNA. IL-1α and nucleosomal DNA were subsequently released from AMs upon loss of plasma membrane integrity. In contrast, necrotic AMs released only unfragmented DNA and necroptotic AMs released only IL-1α. In mice exposed to Be, TNF-α promoted release of DAMPs and was required for the mobilization of immunogenic DCs, the expansion of Be-reactive CD4+ T cells, and pulmonary inflammation in a mouse model of CBD. Thus, early autocrine effects of particle-induced TNF-α on AMs led to a break in peripheral tolerance. This potentially novel mechanism may underlie the known relationship between fine particle inhalation, TNF-α, and loss of peripheral tolerance in T cell-mediated autoimmune disease and hypersensitivities.

Human Miscarriage Is Associated With Dysregulations in Peripheral Blood-Derived Myeloid Dendritic Cell Subsets

Dendritic cells (DC) are critically involved in decisions related to the acceptance or rejection of the foreign fetal antigens by the maternal immune system. However, particularly for human peripheral blood DCs (PBDC), available literature is rather inconsistent and the factors regulating these cells are ill-defined. Here, we investigated the phenotype and functionality of different human PBDC subsets during normal and pathologic pregnancies and studied an involvement of human chorionic gonadotropin (hCG) in PBDC regulation. Peripheral blood samples were obtained from normal pregnant women in all three trimesters, from first trimester miscarriage patients and from healthy non-pregnant women. Samples were analyzed for plasma hCG levels, for regulatory T (Treg) cell numbers, for frequencies of total and mature plasmacytoid (PDC) and myeloid (MDC1 and MDC2) PBDC subsets and for their cytokine secretion. In vitro assays, culturing PDC, MDC1 or MDC2 in the presence of two trophoblast cell lines, placenta explant supernatants or two hCG preparations were performed. The Treg-inducing capability of hCG- or non-hCG-treated stimulated MDC1 was assessed. Total and mature MDC1 and MDC2 frequencies increased during the first and second trimester of normal pregnancy, respectively. Miscarriage was associated with a reduced MDC1 and an increased MDC2 activation profile. PDC were not altered neither during normal pregnancy progression nor during miscarriage. In vitro, the culture of isolated PBDC subsets in the presence of placenta-derived factors impaired the maturation of MDC1 and differentially affected PDC maturation. An inhibitory effect on MDC1 and PDC maturation was also proven for the urine-derived hCG preparation. Finally, we observed a Treg cell elevation during early normal pregnancy that was not present in miscarriages. Stimulated MDC1 induced Treg cells in vitro, however, hCG was not involved in this process. Our findings suggest that during normal pregnancy PBDC subsets are differentially regulated dependent on gestational age. Miscarriage seems to be associated with dysregulations in the myeloid PBDC subsets and with disturbances in Treg cell frequencies. Moreover, our results propose an interdependency between MDC1 and Treg cells during early pregnancy. hCG, although shown to impair MDC1 maturation, does not seem to be a key regulator of PBDC alterations during pregnancy.

Antigen-specific tolerance to self-antigens in protein replacement therapy, gene therapy and autoimmunity

Trials of antigen-specific tolerance have been undertaken in the clinic for over fifty years and the results of these antigen-specific clinical trials are described in this review. Antigen-specific tolerization of the immune system in protein replacement therapy for hemophilia A is an accepted treatment. Clinical trials are ongoing for autoimmune conditions such as type 1 diabetes, multiple sclerosis, neuromyelitis optica, and rheumatoid arthritis with various antigen-specific strategies. Trials for tolerization in celiac disease aim for antigen specific tolerance to gluten, an environmental trigger, which may then halt the progression to autoimmunity targeting a self-antigen, tissue transglutaminase. Although many promising approaches have been demonstrated in pre-clinical models, this review will focus primarily on clinical trials of antigen-specific tolerance that have been taken to the clinic and with initial results reported in the peer reviewed literature. A separate article on approaches with CAR-T cells appears in this volume.

Site-Specific DC Surface Signatures Influence CD4+ T Cell Co-stimulation and Lung-Homing

Dendritic cells (DCs) that drain the gut and skin are known to favor the establishment of T cell populations that home to the original site of DC-antigen (Ag) encounter by providing soluble “imprinting” signals to T cells in the lymph node (LN). To study the induction of lung T cell-trafficking, we used a protein-adjuvant murine intranasal and intramuscular immunization model to compare in vivo-activated Ag⁺ DCs in the lung and muscle-draining LNs. Higher frequencies of Ag⁺ CD11b⁺ DCs were observed in lung-draining mediastinal LNs (MedLN) compared to muscle-draining inguinal LNs (ILN). Ag⁺ CD11b⁺ MedLN DCs were qualitatively superior at priming CD4⁺ T cells, which then expressed CD49a and CXCR3, and preferentially trafficked into the lung parenchyma. CD11b⁺ DCs from the MedLN expressed higher levels of surface podoplanin, Trem4, GL7, and the known co-stimulatory molecules CD80, CD86, and CD24. Blockade of specific MedLN DC molecules or the use of sorted DC and T cell co-cultures demonstrated that DC surface phenotype influences the ability to prime T cells that then home to the lung. Thus, the density of dLN Ag⁺ DCs, and DC surface molecule signatures are factors that can influence the output and differentiation of lung-homing CD4⁺ T cells.

Engineering immunomodulatory biomaterials for type 1 diabetes

A cure for type 1 diabetes (T1D) would help millions of people worldwide, but remains elusive thus far. Tolerogenic vaccines and beta cell replacement therapy are complementary therapies that seek to address aberrant T1D autoimmune attack and subsequent beta cell loss. However, both approaches require some form of systematic immunosuppression, imparting risks to the patient. Biomaterials-based tools enable localized and targeted immunomodulation, and biomaterial properties can be designed and combined with immunomodulatory agents to locally instruct specific immune responses. In this Review, we discuss immunomodulatory biomaterial platforms for the development of T1D tolerogenic vaccines and beta cell replacement devices. We investigate nano- and microparticles for the delivery of tolerogenic agents and autoantigens, and as artificial antigen presenting cells, and highlight how bulk biomaterials can be used to provide immune tolerance. We examine biomaterials for drug delivery and as immunoisolation devices for cell therapy and islet transplantation, and explore synergies with other fields for the development of new T1D treatment strategies.

Biomaterial-Based Activation and Expansion of Tumor-Specific T Cells

Traditional tumor vaccination approaches mostly focus on activating dendritic cells (DCs) by providing them with a source of tumor antigens and/or adjuvants, which in turn activate tumor-reactive T cells. Novel biomaterial-based cancer immunotherapeutic strategies focus on directly activating and stimulating T cells through molecular cues presented on synthetic constructs with the aim of improving T cell survival, more precisely steer T cell activation and direct T cell differentiation. Synthetic artificial antigen presenting cells (aAPCs) decorated with T cell-activating ligands are being developed to induce robust tumor-specific T cell responses, essentially bypassing DCs. In this perspective, we approach these promising new technologies from an immunological angle, first by identifying the CD4⁺ and CD8⁺ T cell subtypes that are imperative for robust anti-cancer immunity and subsequently discussing the molecular cues needed to induce these cells types. We will elaborate on how biomaterials can be applied to stimulate T cells in vitro and in vivo to improve their survival, activation and function. Scaffold-based methods can also be used as delivery vehicles for adoptive transfer of T cells, including tumor-infiltrating lymphocytes (TILs) and chimeric antigen receptor expressing (CAR) T cells, while simultaneously stimulating these cells. Finally, we provide suggestions on how these insights could advance the field of biomaterial-based activation and expansion of tumor-specific T cells in the future.

Vitamin D controls the capacity of human dendritic cells to induce functional regulatory T cells by regulation of glucose metabolism

Tolerogenic dendritic cells (tolDCs) instruct regulatory T cells (Tregs) to dampen autoimmunity. Active vitamin D₃ (1α,25-dihydroxyvitamin D₃; 1α,25(OH)₂D₃) imprints human monocyte-derived DCs with tolerogenic properties by reprogramming their glucose metabolism. Here we identify the glycolytic enzyme 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 4 (PFKFB4) as a critical checkpoint and direct transcriptional target of 1α,25(OH)₂D₃ in determining the tolDC profile. Using tracer metabolomics, we show that PFKFB4 activity is essential for glucose metabolism, especially for glucose oxidation, which is elevated upon 1α,25(OH)₂D₃ exposure. Pharmacological inhibition of PFKFB4 reversed the 1α,25(OH)₂D₃-mediated shift in metabolism, DC profile and function, as determined by expression of inhibitory surface markers and secretion of regulatory cytokines and factors. Moreover, PFKFB4 inhibition in 1α,25(OH)₂D₃-treated DCs blocked their hallmark capacity to induce suppressive Tregs. This work demonstrates that alterations in the bioenergetic metabolism of immune cells are central to the immunomodulatory effects induced by 1α,25(OH)₂D₃.

Development of a flow cytometry assay which allows to evaluate the efficiency of immunomodulatory vaccines to enhance T cell-mediated antitumor response

Immunotherapy has revolutionized the treatment of cancer. Since tumor cells exhibit low immunogenicity and can induce several mechanisms of tolerance, the use of monoclonal antibodies or other immunomodulators, targeting costimulation of T cells may mediate the inhibition of immunosuppressive mechanisms, favouring immune surveillance and enhancing the detection and elimination of tumor cells. We developed a new in vitro assay, based on flow cytometry, which allows exploring the therapeutic potential of tumor-derived immunomodulatory lineages, enhancing anti-tumor response. We generated tumor-derived cells that simultaneously co-express eGFP and one immunomodulatory molecule (OX40L, 4-1BBL or GM-CSF). These genetically modified tumor-derived cells are irradiated and then incubated with primary T cells to evaluate the killing activity, which can be estimated by a decrease in the eGFP positive cells. The results have shown correlation with in vivo experiments. This model may contribute to the development of high-throughput assays for the screening of immunomodulators and a reduction in the use of experimental animals.

The Journey of in vivo Virus Engineered Dendritic Cells From Bench to Bedside: A Bumpy Road

Dendritic cells (DCs) are recognized as highly potent antigen-presenting cells that are able to stimulate cytotoxic T lymphocyte (CTL) responses with antitumor activity. Consequently, DCs have been explored as cellular vaccines in cancer immunotherapy. To that end, DCs are modified with tumor antigens to enable presentation of antigen-derived peptides to CTLs. In this review we discuss the use of viral vectors for in situ modification of DCs, focusing on their clinical applications as anticancer vaccines. Among the viral vectors discussed are those derived from viruses belonging to the families of the Poxviridae, Adenoviridae, Retroviridae, Togaviridae, Paramyxoviridae, and Rhabdoviridae. We will further shed light on how the combination of viral vector-based vaccination with T-cell supporting strategies will bring this strategy to the next level.

Dendritic Cells Actively Limit Interleukin-10 Production Under Inflammatory Conditions via DC-SCRIPT and Dual-Specificity Phosphatase 4

Dendritic cell (DC)-based immunotherapy makes use of the DC’s ability to direct the adaptive immune response toward activation or inhibition. DCs perform this immune orchestration in part by secretion of selected cytokines. The most potent anti-inflammatory cytokine interleukin-10 (IL-10) is under tight regulation, as it needs to be predominantly expressed during the resolution phase of the immune response. Currently it is not clear whether there is active suppression of IL-10 by DCs at the initial pro-inflammatory stage of the immune response. Previously, knockdown of the DC-specific transcription factor DC-SCRIPT has been demonstrated to mediate an extensive increase in IL-10 production upon encounter with pro-inflammatory immune stimuli. Here, we explored how DC-SCRIPT contributes to IL-10 suppression under pro-inflammatory conditions by applying chromatin immunoprecipitation sequencing analysis of DC-SCRIPT and the epigenetic marks H3K4me3 and H3K27ac in human DCs. The data showed binding of DC-SCRIPT to a GA-rich motif at H3K27ac-marked genomic enhancers that associated with genes encoding MAPK dual-specificity phosphatases (DUSPs). Functional studies revealed that upon knockdown of DC-SCRIPT, human DCs express much less DUSP4 and exhibit increased phosphorylation of the three major MAPKs (ERK, JNK, and p38). Enhanced ERK signaling in DC-SCRIPT-knockdown-DCs led to higher production of IL-10, which was reverted by rescuing DUSP4 expression. Finally, DC-SCRIPT-knockdown-DCs induced less IFN-γ and increased IL-10 production in naïve T cells, indicative for a more anti-inflammatory phenotype. In conclusion, we have delineated a new mechanism by which DC-SCRIPT allows DCs to limit IL-10 production under inflammatory conditions and potentiate pro-inflammatory Th1 responses. These insights may be exploited to improve DC-based immunotherapies.

Streptococcus suis Serotype 2 Infection Impairs Interleukin-12 Production and the MHC-II-Restricted Antigen Presentation Capacity of Dendritic Cells

Streptococcus suis is an important swine pathogen and emerging zoonotic agent. Encapsulated strains of S. suis modulate dendritic cell (DC) functions, leading to poorly activated CD4⁺ T cells. However, the antigen presentation ability of S. suis-stimulated DCs has not been investigated yet. In this work, we aimed to characterize the antigen presentation profiles of S. suis-stimulated DCs, both in vitro and in vivo. Upon direct activation in vitro, S. suis-stimulated murine bone marrow-derived DCs (bmDCs) preserved their antigen capture/processing capacities. However, they showed delayed kinetics of MHC-II expression compared to lipopolysaccharide-stimulated bmDCs. Meanwhile, splenic DCs from infected mice exhibited a compromised MHC-II expression, despite an appropriate expression of maturation markers. To identify potential interfering mechanisms, Class II Major Histocompatibility Complex Transactivator (CIITA) and membrane-associated RING-CH (MARCH)1/8 transcription were studied. S. suis-stimulated DCs maintained low levels of CIITA at early time points, both in vitro and in vivo, which could limit their ability to increase MHC-II synthesis. S. suis-stimulated DCs also displayed sustained/upregulated levels of MARCH1/8, thus possibly leading to MHC-II lysosomal degradation. The bacterial capsular polysaccharide played a partial role in this modulation. Finally, interleukin (IL)-12p70 production was inhibited in splenic DCs from infected mice, a profile compatible with DC indirect activation by pro-inflammatory compounds. Consequently, these cells induced lower levels of IL-2 and TNF-α in an antigen-specific CD4⁺ T cell presentation assay and blunted T cell CD25 expression. It remains unclear at this stage whether these phenotypical and transcriptional modulations observed in response to S. suis in in vivo infections are part of a bacterial immune evasion strategy or rather a feature common to systemic inflammatory response-inducing agents. However, it appears that the MHC-II-restricted antigen presentation and Th1-polarizing cytokine production capacities of DCs are impaired during S. suis infection. This study highlights the potential consequences of inflammation on the type and magnitude of the immune response elicited by a pathogen.

Dual requirement for STAT signaling in dendritic cell immunobiology

Dendritic cells (DC) represent an attractive target for therapeutic manipulation of the immune system and enhancement of insufficient immune response in cancer. STAT family members play key roles in the differentiation and activation of DC, a feature that is currently being exploited in DC-based therapies. We previously reported that the small-molecule Stattic, originally developed as a STAT3-specific inhibitor, also inhibits STAT1 and STAT2 phosphorylation in DC exposed to cytokines or LPS. Aim of this study was to investigate the functional consequences of in vitro treatment with Stattic on DC immunobiology. Interestingly, we observed an opposite effect of Stattic on DC immunophenotype depending on the activation state. While the expression of costimulatory, coinhibitory, MHC class II and CD83 molecules was enhanced in immature DC exposed to Stattic, the LPS induced up-modulation of these molecules was strongly repressed. An effective blockade of LPS-induced secretion of proinflammatory cytokines and capacity to stimulate a Th1 polarization was also observed in the presence of Stattic. Our results indicate that the immunological consequences of STAT inhibition in DC vary depending on the cell activation state. This knowledge is of relevance for anticipating potential effects of STAT-targeted therapeutics, and pursuing selective DC manipulation in clinical applications.

Effect of immune tolerance induced by immature dendritic cells and CTLA4-Ig on systemic lupus erythematosus: An in vivo study

Systemic lupus erythematosus (SLE) is a multi-organ autoimmune disease in which tissue damage is caused by autoantibodies. The induction of specific immune tolerance, including the utilization of immune regulatory cells, may enhance the therapeutic effects of organ transplantation in patients with SLE. Furthermore, inhibiting immune responses has been reported to be an effective treatment for SLE. However, few studies have explored the association between an increased immune tolerance and a decreased immune response in SLE treatment. Dendritic cells (DCs), which are highly efficient antigen-presenting cells, are able to induce specific tolerance, while cytotoxic T lymphocyte antigen 4-immunoglobulin (CTLA4-Ig) inhibits the immune response. In the present study, interleukin (IL)-10-treated DCs and CTLA4-Ig were administered to mice with SLE alone or in combination and the therapeutic effects were investigated. IL-10 was added into the culture medium of bone marrow-derived DCs to prevent them from differentiating into mature cells. Low levels of major histocompatibility complex II, cluster of differentiation (CD)40, CD80 and CD86 were detected, which indicated that the immature state of DCs was maintained. IL-10-treated DCs were subsequently injected into the caudal vein of B6.MRL-Fas^lpr/J lupus mice, which are an established animal model of SLE. To amplify the tolerance effect, mice were simultaneously injected with CTLA4-Ig. Compared with the IL-10-treated DC and CTLA4-Ig groups, combined treatment with IL-10-treated DCs and CTLA4-Ig strongly induced immune tolerance in mice with SLE, as indicated by the significantly reduced levels of urine protein, anti-nuclear antibody, double-stranded DNA and IL-17A. A significant decrease in the proportion of T helper cells and an increase in the proportion of CD4⁺ forkhead box protein P3⁺ Treg cells was also observed, further confirming the induction of immune tolerance. These results suggest that combined treatment with IL-10-DCs and CTLA4-Ig may be a promising novel therapeutic strategy for the treatment of SLE.

Co-stimulatory function in primary germinal center responses: CD40 and B7 are required on distinct antigen-presenting cells

Watanabe et al. report that, contrary to the prevailing paradigm, there are unique cellular requirements for B7 and CD40 expression in primary GC responses. B7 is required on DCs but not on B cells, whereas CD40 is required on B cells but not on DCs for generation of Tfh cells, GC B cells, and high-affinity class-switched antibody production.

T cell–dependent germinal center (GC) responses require coordinated interactions of T cells with two antigen-presenting cell (APC) populations, B cells and dendritic cells (DCs), in the presence of B7- and CD40-dependent co-stimulatory pathways. Contrary to the prevailing paradigm, we found unique cellular requirements for B7 and CD40 expression in primary GC responses to vaccine immunization with protein antigen and adjuvant: B7 was required on DCs but was not required on B cells, whereas CD40 was required on B cells but not on DCs in the generation of antigen-specific follicular helper T cells, antigen-specific GC B cells, and high-affinity class-switched antibody production. There was, in fact, no requirement for coexpression of B7 and CD40 on the same cell in these responses. Our findings support a substantially revised model for co-stimulatory function in the primary GC response, with crucial and distinct contributions of B7- and CD40-dependent pathways expressed by different APC populations and with important implications for understanding how to optimize vaccine responses or limit autoimmunity.

Glucose represses dendritic cell-induced T cell responses

Glucose and glycolysis are important for the proinflammatory functions of many immune cells, and depletion of glucose in pathological microenvironments is associated with defective immune responses. Here we show a contrasting function for glucose in dendritic cells (DCs), as glucose represses the proinflammatory output of LPS-stimulated DCs and inhibits DC-induced T-cell responses. A glucose-sensitive signal transduction circuit involving the mTOR complex 1 (mTORC1), HIF1α and inducible nitric oxide synthase (iNOS) coordinates DC metabolism and function to limit DC-stimulated T-cell responses. When multiple T cells interact with a DC, they compete for nutrients, which can limit glucose availability to the DCs. In such DCs, glucose-dependent signalling is inhibited, altering DC outputs and enhancing T-cell responses. These data reveal a mechanism by which T cells regulate the DC microenvironment to control DC-induced T-cell responses and indicate that glucose is an important signal for shaping immune responses.

iPSC-Derived Regulatory Dendritic Cells Inhibit Allograft Rejection by Generating Alloantigen-Specific Regulatory T Cells

Regulatory dendritic cell (DCregs)-based immunotherapy is a potential therapeutic tool for transplant rejection. We generated DCregs from murine induced pluripotent stem cells (iPSCs), which could remain in a “stable immature stage” even under strong stimulation. Harnessing this characteristic, we hypothesized that iPS-DCregs worked as a negative vaccine to generate regulatory T cells (Tregs), and induced donor-specific allograft acceptance. We immunized naive CBA (H-2K^k) mice with B6 (H-2K^b) iPS-DCregs and found that Tregs (CD4⁺CD25⁺FOXP3⁺) significantly increased in CBA splenocytes. Moreover, immunized CBA recipients permanently accepted B6 cardiac grafts in a donor-specific pattern. We demonstrated mechanistically that donor-type iPS-DCregs triggered transforming growth factor β1 secretion, under which the donor-antigen peptides directed naive CD4⁺ T cells to differentiate into donor-specific FOXP3⁺ Tregs instead of into effector T cells in vivo. These findings highlight the potential of iPS-DCregs as a key cell therapy resource in clinical transplantation.

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iPS-DCregs keep in stable immature stage that makes them a powerful cellular vaccine

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Donor-type iPS-DCregs lead to permanent acceptance of allogeneic cardiac grafts

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iPS-DCregs reduce CTL and downregulate proinflammatory cytokine

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iPS-DCregs enhance Tregs transmigration capability in a TGF-β1-dependent manner

Diversity of immune cell types in multiple sclerosis and its animal model: Pathological and therapeutic implications

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system with an autoimmune attack on the components of the myelin sheath and axons. The etiology of the disease remains largely unknown, but it is commonly acknowledged that the development of MS probably results from the interaction of environmental factors in conjunction with a genetic predisposition. Current therapeutic approaches can only ameliorate the clinical symptoms or reduce the frequency of relapse in MS. Most drugs used in this disease broadly suppress the functions of immune effector cells, which can result in serious side effects. Thus, new therapeutic methods resulting in greater efficacy and lower toxicity are needed. Toward this end, cell-based therapies are of increasing interest in the treatment of MS. Several immunoregulatory cell types, including regulatory T cells, regulatory B cells, M2 macrophages, tolerogenic dendritic cells, and stem cells, have been developed as novel therapeutic tools for the treatment of MS. In this Review, we summarize studies on the application of these cell populations for the treatment of MS and its animal model, experimental autoimmune encephalomyelitis, and call for further research on applications and mechanisms by which these cells act in the treatment of MS. © 2017 The Authors Journal of Neuroscience Research Published by Wiley Periodicals, Inc.

Mining the Complex Family of Protein Tyrosine Phosphatases for Checkpoint Regulators in Immunity

The family of protein tyrosine phosphatases (PTPs) includes 107 genes in humans that are diverse in their structures and expression profiles. The majority are present in immune cells and play various roles in either inhibiting or promoting the duration and amplitude of signaling cascades. Several PTPs, including TC-PTP (PTPN2) and SHP-1 (PTPN6), have been recognized as being crucial for maintaining proper immune response and self-tolerance, and have gained recognition as true immune system checkpoint modulators. This chapter details the most recent literature on PTPs and immunity by examining their known functions in regulating signaling from either established checkpoint inhibitors or by their intrinsic properties, as modulators of the immune response. Notably, we review PTP regulatory properties in macrophages, antigen-presenting dendritic cells, and T cells. Overall, we present the PTP gene family as a remarkable source of novel checkpoint inhibitors wherein lies a great number of new targets for immunotherapies.

Recent advances and future of immunotherapy for glioblastoma

INTRODUCTION

Outcome for glioma (GBM) remains dismal despite advances in therapeutic interventions including chemotherapy, radiotherapy and surgical resection. The overall survival benefit observed with immunotherapies in cancers such as melanoma and prostate cancer has fuelled research into evaluating immunotherapies for GBM.

AREAS COVERED

Preclinical studies have brought a wealth of information for improving the prognosis of GBM and multiple clinical studies are evaluating a wide array of immunotherapies for GBM patients. This review highlights advances in the development of immunotherapeutic approaches. We discuss the strategies and outcomes of active and passive immunotherapies for GBM including vaccination strategies, gene therapy, check point blockade and adoptive T cell therapies. We also focus on immunoediting and tumor neoantigens that can impact the efficacy of immunotherapies.

EXPERT OPINION

Encouraging results have been observed with immunotherapeutic strategies; some clinical trials are reaching phase III. Significant progress has been made in unraveling the molecular and genetic heterogeneity of GBM and its implications to disease prognosis. There is now consensus related to the critical need to incorporate tumor heterogeneity into the design of therapeutic approaches. Recent data also indicates that an efficacious treatment strategy will need to be combinatorial and personalized to the tumor genetic signature.

Human CD1c(+) DCs are critical cellular mediators of immune responses induced by immunogenic cell death

Chemotherapeutics, including the platinum compounds oxaliplatin (OXP) and cisplatin (CDDP), are standard care of treatment for cancer. Although chemotherapy has long been considered immunosuppressive, evidence now suggests that certain cytotoxic agents can efficiently stimulate antitumor responses, through the induction of a form of apoptosis, called immunogenic cell death (ICD). ICD is characterized by exposure of calreticulin and heat shock proteins (HSPs), secretion of ATP and release of high-mobility group box 1 (HMGB1). Proper activation of the immune system relies on the integration of these signals by dendritic cells (DCs). Studies on the crucial role of DCs, in the context of ICD, have been performed using mouse models or human in vitro-generated monocyte-derived DCs (moDCs), which do not fully recapitulate the in vivo situation.

Here, we explore the effect of platinum-induced ICD on phenotype and function of human blood circulating DCs. Tumor cells were treated with OXP or CDDP and induction of ICD was investigated. We show that both platinum drugs triggered translocation of calreticulin and HSP70, as well as the release of ATP and HMGB1. Platinum treatment increased phagocytosis of tumor fragments by human blood DCs and enhanced phenotypic maturation of blood myeloid and plasmacytoid DCs. Moreover, upon interaction with platinum-treated tumor cells, CD1c⁺ DCs efficiently stimulated allogeneic proliferation of T lymphocytes. Together, our observations indicate that platinum-treated tumor cells may exert an active stimulatory effect on human blood DCs. In particular, these data suggest that CD1c⁺ DCs are critical mediators of immune responses induced by ICD.

Expansion of a BDCA1+CD14+ Myeloid Cell Population in Melanoma Patients May Attenuate the Efficacy of Dendritic Cell Vaccines

The tumor microenvironment is characterized by regulatory T cells, type II macrophages, myeloid-derived suppressor cells, and other immunosuppressive cells that promote malignant progression. Here we report the identification of a novel BDCA1(+)CD14(+) population of immunosuppressive myeloid cells that are expanded in melanoma patients and are present in dendritic cell-based vaccines, where they suppress CD4(+) T cells in an antigen-specific manner. Mechanistic investigations showed that BDCA1(+)CD14(+) cells expressed high levels of the immune checkpoint molecule PD-L1 to hinder T-cell proliferation. While this BDCA1(+)CD14(+) cell population expressed markers of both BDCA1(+) dendritic cells and monocytes, analyses of function, transcriptome, and proteome established their unique nature as exploited by tumors for immune escape. We propose that targeting these cells may improve the efficacy of cancer immunotherapy. Cancer Res; 76(15); 4332-46. ©2016 AACR.

Altered molecular expression of TLR-signaling pathways affects the steady-state release of IL-12p70 and IFN-α in patients with relapsing-remitting multiple sclerosis

Recent evidence suggests a key role of dendritic cells (DC) in the immunopathogenesis of multiple sclerosis (MS). Whereas dysfunction of DC was reported in MS patients, the underlying cause for this is not fully elucidated yet. The aim of the present study was to compare the gene expression profile of molecules involved in TLR4 and TLR7 signaling in DC from patients with MS and healthy controls. For this, circulating DC subsets were purified from patients with relapsing-remitting MS (RRMS) and from healthy controls for quantitative real-time PCR analysis. Additionally, TLR responsiveness in peripheral blood was investigated. We observed an aberrant steady-state release of IL-12p70 and IFN-α in patients with RRMS compared with healthy controls. Expression of IRF1 and JUN was reduced in conventional DC from patients with RRMS. In plasmacytoid DC from patients with RRMS, expression of IRF7 and IFNGR1 was reduced, while higher expression levels of TLR4 and LY86 were found compared with DC from healthy controls. The observed alterations in the gene expression of molecules involved in the TLR4 and TLR7 signaling pathways in circulating DC subsets may underlie the impaired IL-12p70 and IFN-α secretion in patients with RRMS, thereby potentially contributing to the disease pathogenesis of MS.

Primary Human Blood Dendritic Cells for Cancer Immunotherapy-Tailoring the Immune Response by Dendritic Cell Maturation

Dendritic cell (DC)-based cancer vaccines hold the great promise of tipping the balance from tolerance of the tumor to rejection. In the last two decades, we have gained tremendous knowledge about DC-based cancer vaccines. The maturation of DCs has proven indispensable to induce immunogenic T cell responses. We review the insights gained from the development of maturation cocktails in monocyte derived DC-based trials. More recently, we have also gained insights into the functional specialization of primary human blood DC subsets. In peripheral human blood, we can distinguish at least three primary DC subsets, namely CD1c⁺ and CD141⁺ myeloid DCs and plasmacytoid DCs. We reflect the current knowledge on maturation and T helper polarization by these blood DC subsets in the context of DC-based cancer vaccines. The maturation stimulus in combination with the DC subset will determine the type of T cell response that is induced. First trials with these natural DCs underline their excellent in vivo functioning and mark them as promising tools for future vaccination strategies.

Immunostimulatory Gene Therapy Using Oncolytic Viruses as Vehicles

Immunostimulatory gene therapy has been developed during the past twenty years. The aim of immunostimulatory gene therapy is to tilt the suppressive tumor microenvironment to promote anti-tumor immunity. Hence, like a Trojan horse, the gene vehicle can carry warriors and weapons into enemy territory to combat the tumor from within. The most promising immune stimulators are those activating and sustaining Th1 responses, but even if potent effects were seen in preclinical models, many clinical trials failed to show objective responses in cancer patients. However, with new tools to control ongoing immunosuppression in cancer patients, immunostimulatory gene therapy is now emerging as an interesting option. In parallel, oncolytic viruses have been shown to be safe in patients. To prolong immune stimulation and to increase efficacy, these two fields are now merging and oncolytic viruses are armed with immunostimulatory transgenes. These novel agents are racing towards approval as established cancer immunotherapeutics.

Contribution of enhanced engagement of antigen presentation machinery to the clinical immunogenicity of a human interleukin (IL)-21 receptor-blocking therapeutic antibody

Reliable risk assessment for biotherapeutics requires accurate evaluation of risk factors associated with immunogenicity. Immunogenicity risk assessment tools were developed and applied to investigate the immunogenicity of a fully human therapeutic monoclonal antibody, ATR-107 [anti-interleukin (IL)-21 receptor] that elicited anti-drug antibodies (ADA) in 76% of healthy subjects in a Phase 1 study. Because the ATR-107 target is expressed on dendritic cells (DCs), the immunogenicity risk related to engagement with DC and antigen presentation pathways was studied. Despite the presence of IL-21R on DCs, ATR-107 did not bind to the DCs more extensively than the control therapeutic antibody (PF-1) that had elicited low clinical ADA incidence. However, ATR-107, but not the control therapeutic antibody, was translocated to the DC late endosomes, co-localized with intracellular antigen-D related (HLA-DR) molecules and presented a dominant T cell epitope overlapping the complementarity determining region 2 (CDR2) of the light chain. ATR-107 induced increased DC activation exemplified by up-regulation of DC surface expression of CD86, CD274 (PD-L1) and CD40, increased expansion of activated DC populations expressing CD86(hi), CD40(hi), CD83(hi), programmed death ligand 1 (PD-L1)(hi), HLA-DR(hi) or CCR7(hi), as well as elevated secretion of tumour necrosis factor (TNF)-α by DCs. DCs exposed to ATR-107 stimulated an autologous T cell proliferative response in human donor cells, in concert with the detection of immunoglobulin (Ig)G-type anti-ATR-107 antibody response in clinical samples. Collectively, the enhanced engagement of antigen presentation machinery by ATR-107 was suggested. The approaches and findings described in this study may be relevant to identifying lower immunogenicity risk targets and therapeutic molecules.

Prospects of immune checkpoint modulators in the treatment of glioblastoma

Glioblastoma is the most common primary brain tumour in adults. Prognosis is poor: even with the current gold-standard first-line treatment—maximal safe resection and combination of radiotherapy with temozolomide chemotherapy—the median overall survival time is only approximately 15-17 months, because the tumour recurs in virtually all patients, and no commonly accepted standard treatment for recurrent disease exists. Several targeted agents have failed to improve patient outcomes in glioblastoma. Immunotherapy with immune checkpoint inhibitors such as ipilimumab, nivolumab, and pembrolizumab has provided relevant clinical improvements in other advanced tumours for which conventional therapies have had limited success, making immunotherapy an appealing strategy in glioblastoma. This Review summarizes current knowledge on immune checkpoint modulators and evaluates their potential role in glioblastoma on the basis of preclinical studies and emerging clinical data. Furthermore, we discuss challenges that need to be considered in the clinical development of drugs that target immune checkpoint pathways in glioblastoma, such as specific properties of the immune system in the CNS, issues with radiological response assessment, and potential interactions with established and emerging treatment strategies.

DC-SCRIPT Regulates IL-10 Production in Human Dendritic Cells by Modulating NF-κBp65 Activation

The balance between tolerance and immunity is important for the outcome of an infection or cancer, and dendritic cells (DCs) are key regulators of this balance. DC-specific transcript (DC-SCRIPT) is a protein expressed by DCs and has been demonstrated to suppress both TLR-mediated expression of IL-10 and glucocorticoid receptor-mediated transcription of glucocorticoid-induced leucine zipper (GILZ). Because GILZ is known to promote IL-10 production, we investigated whether these two processes are linked. Dual-knockdown and inhibition experiments demonstrated that neither GILZ nor glucocorticoid receptor play a role in TLR-induced IL-10 production after DC-SCRIPT knockdown. The NF-κB pathway is another route involved in IL-10 production after DC activation. Strikingly, inhibition of NF-κB led to a decreased TLR-mediated IL-10 production in DC-SCRIPT knockdown DCs. Moreover, DC-SCRIPT knockdown DCs showed enhanced phosphorylation, acetylation, and IL10 enhancer binding of the NF-κB subunit p65. These data demonstrate that besides nuclear receptor regulation, DC-SCRIPT also modulates activation of NF-κBp65 after TLR activation in human DCs.

Serotype-specific Binding Properties and Nanoparticle Characteristics Contribute to the Immunogenicity of rAAV1 Vectors

The immunogenic properties of recombinant adeno-associated virus (rAAV) gene transfer vectors remain incompletely characterized in spite of their usage as gene therapy vectors or as vaccines. Molecular interactions between rAAV and various types of antigen-presenting cells (APCs), as well as the impact of these interactions on transgene or capsid-specific immunization remain unclear. We herein show that binding motifs recognized by the capsid and which determine the vector tissue tropism are also critical for key immune activation processes. Using rAAV capsid serotype 1 (rAAV1) vectors which primary receptors on target cells are α2,3 and α2,6 N-linked sialic acids, we show that sialic acid-dependent binding of rAAV1 on APCs is essential to trigger CD4⁺ T-cell responses by increasing rAAV1 uptake and contributing to antigenic presentation of both the capsid and transgene product although this involves different APCs. In addition, the nanoparticulate structure of the vector in itself appears to be sufficient to trigger mobilization and activation of some APCs. Therefore, combinations of structural and of serotype-specific cell-targeting properties of rAAV1 determine its complex immunogenicity. These findings may be useful to guide a selection of rAAV variants depending on the intended level of immunogenicity for either gene therapy or vaccination applications.