Ox40-ligand has a critical costimulatory role in dendritic cell:T cell interactions

Disrupting TSLP-TSLP receptor interactions via putative small molecule inhibitors yields a novel and efficient treatment option for atopic diseases

Thymic stromal lymphopoietin (TSLP) is a key player in atopic diseases, which has sparked great interest in therapeutically targeting TSLP. Yet, no small-molecule TSLP inhibitors exist due to the challenges of disrupting the protein-protein interaction between TSLP and its receptor. Here, we report the development of small-molecule TSLP receptor inhibitors using virtual screening and docking of >1,000,000 compounds followed by iterative chemical synthesis. BP79 emerged as our lead compound that effectively abrogates TSLP-triggered cytokines at low micromolar concentrations. For in-depth analysis, we developed a human atopic disease drug discovery platform using multi-organ chips. Here, topical application of BP79 onto atopic skin models that were co-cultivated with lung models and Th2 cells effectively suppressed immune cell infiltration and IL-13, IL-4, TSLP, and periostin secretion, while upregulating skin barrier proteins. RNA-Seq analysis corroborate these findings and indicate protective downstream effects on the lungs. To the best of our knowledge, this represents the first report of a potent putative small molecule TSLPR inhibitor which has the potential to expand the therapeutic and preventive options in atopic diseases.

The Role of OX40-OX40L Axis in the Pathogenesis of Atopic Dermatitis

OX40 is a co-stimulatory immune checkpoint molecule that promotes the activation and the effector function of T lymphocytes through interaction with its ligand (OX40L) on antigen-presenting cells. OX40-OX40L axis plays a crucial role in Th1 and Th2 cell expansion, particularly during the late phases or long-lasting response. Atopic dermatitis is characterized by an immune dysregulation of Th2 activity and by an overproduction of proinflammatory cytokines such as interleukin (IL)-4 and IL-13. Other molecules involved in its pathogenesis include thymic stromal lymphopoietin, IL-33, and IL-25, which contribute to the promotion of OX40L expression on dendritic cells. Lesional skin in atopic dermatitis exhibits a higher level of OX40L+-presenting cells compared with other dermatologic diseases or normal skin. Recent clinical trials using antagonizing anti-OX40 or anti-OX40L antibodies have shown symptom improvement and cutaneous manifestation alleviation in patients with atopic dermatitis. These findings suggest the relevance of the OX40-OX40L axis in atopic dermatitis pathogenesis.

BGB-A445, a novel non-ligand-blocking agonistic anti-OX40 antibody, exhibits superior immune activation and antitumor effects in preclinical models

OX40 is a costimulatory receptor that is expressed primarily on activated CD4+, CD8+, and regulatory T cells. The ligation of OX40 to its sole ligand OX40L potentiates T cell expansion, differentiation, and activation and also promotes dendritic cells to mature to enhance their cytokine production. Therefore, the use of agonistic anti-OX40 antibodies for cancer immunotherapy has gained great interest. However, most of the agonistic anti-OX40 antibodies in the clinic are OX40L-competitive and show limited efficacy. Here, we discovered that BGB-A445, a non-ligand-competitive agonistic anti-OX40 antibody currently under clinical investigation, induced optimal T cell activation without impairing dendritic cell function. In addition, BGB-A445 dose-dependently and significantly depleted regulatory T cells in vitro and in vivo via antibody-dependent cellular cytotoxicity. In the MC38 syngeneic model established in humanized OX40 knock-in mice, BGB-A445 demonstrated robust and dose-dependent antitumor efficacy, whereas the ligand-competitive anti-OX40 antibody showed antitumor efficacy characterized by a hook effect. Furthermore, BGB-A445 demonstrated a strong combination antitumor effect with an anti-PD-1 antibody. Taken together, our findings show that BGB-A445, which does not block OX40-OX40L interaction in contrast to clinical-stage anti-OX40 antibodies, shows superior immune-stimulating effects and antitumor efficacy and thus warrants further clinical investigation.

OX40L-expressing recombinant modified vaccinia virus Ankara induces potent antitumor immunity via reprogramming Tregs

Effective depletion of immune suppressive regulatory T cells (Tregs) in the tumor microenvironment without triggering systemic autoimmunity is an important strategy for cancer immunotherapy. Modified vaccinia virus Ankara (MVA) is a highly attenuated, non-replicative vaccinia virus with a long history of human use. Here, we report rational engineering of an immune-activating recombinant MVA (rMVA, MVA∆E5R-Flt3L-OX40L) with deletion of the vaccinia E5R gene (encoding an inhibitor of the DNA sensor cyclic GMP-AMP synthase, cGAS) and expression of two membrane-anchored transgenes, Flt3L and OX40L. Intratumoral (IT) delivery of rMVA (MVA∆E5R-Flt3L-OX40L) generates potent antitumor immunity, dependent on CD8+ T cells, the cGAS/STING-mediated cytosolic DNA-sensing pathway, and type I IFN signaling. Remarkably, IT rMVA (MVA∆E5R-Flt3L-OX40L) depletes OX40hi regulatory T cells via OX40L/OX40 interaction and IFNAR signaling. Single-cell RNA-seq analyses of tumors treated with rMVA showed the depletion of OX40hiCCR8hi Tregs and expansion of IFN-responsive Tregs. Taken together, our study provides a proof-of-concept for depleting and reprogramming intratumoral Tregs via an immune-activating rMVA.

Biomaterials Facilitating Dendritic Cell-Mediated Cancer Immunotherapy

Dendritic cell (DC)-based cancer immunotherapy has exhibited remarkable clinical prospects because DCs play a central role in initiating and regulating adaptive immune responses. However, the application of traditional DC-mediated immunotherapy is limited due to insufficient antigen delivery, inadequate antigen presentation, and high levels of immunosuppression. To address these challenges, engineered biomaterials have been exploited to enhance DC-mediated immunotherapeutic effects. In this review, vital principal components that can enhance DC-mediated immunotherapeutic effects are first introduced. The parameters considered in the rational design of biomaterials, including targeting modifications, size, shape, surface, and mechanical properties, which can affect biomaterial optimization of DC functions, are further summarized. Moreover, recent applications of various engineered biomaterials in the field of DC-mediated immunotherapy are reviewed, including those serve as immune component delivery platforms, remodel the tumor microenvironment, and synergistically enhance the effects of other antitumor therapies. Overall, the present review comprehensively and systematically summarizes biomaterials related to the promotion of DC functions; and specifically focuses on the recent advances in biomaterial designs for DC activation to eradicate tumors. The challenges and opportunities of treatment strategies designed to amplify DCs via the application of biomaterials are discussed with the aim of inspiring the clinical translation of future DC-mediated cancer immunotherapies.

Self-Adaptive Antibiofilm Effect and Immune Regulation by Hollow Cu2MoS4 Nanospheres for Treatment of Implant Infections

Implant infections are difficult to cure by traditional antibiotic therapy due to bacterial biofilm-induced antibiotic tolerance and impaired immune responses. To efficiently treat implant infections, therapeutic agents need to kill bacteria and regulate the inflammatory response of immune cells during the biofilm elimination process. Herein, multifunctional smart hollow Cu₂MoS₄ nanospheres (H-CMS NSs) with pH-responsive enzyme-like activities were prepared for self-adaptively eliminating biofilms and regulating the inflammation of macrophages in implant infections. During biofilm infection, the tissue microenvironment around implants is acidic. H-CMS NSs with oxidase (OXD)/peroxidase (POD)-like activities can catalyze reactive oxidative species (ROS) generation for directly killing bacteria and polarizing macrophages to a proinflammatory phenotype. Moreover, the POD-like activity and antibacterial property of H-CMS NSs can be further enhanced under ultrasound (US) irradiation. After the elimination of biofilms, the tissue microenvironment around implants shifts from acidic to neutral. H-CMS NSs show catalase (CAT)-like activity and eliminate excessive ROS, which polarizes macrophages to anti-inflammatory phenotype and promotes healing of infected tissue. This work provides a smart nanozyme with self-adaptive regulation of the antibiofilm activity and immune response by regulating ROS generation/elimination according to the different pathological microenvironments in implant infections during the different therapeutic stages.

Roles of OX40 and OX40 Ligand in Mycosis Fungoides and Sézary Syndrome

Mycosis fungoides (MF) and Sézary syndrome (SS), the most common types of cutaneous T-cell lymphoma (CTCL), are characterized by proliferation of mature CD4+ T-helper cells. Patients with advanced-stage MF and SS have poor prognosis, with 5-year survival rates of 52%. Although a variety of systemic therapies are currently available, there are no curative options for such patients except for stem cell transplantation, and thus the treatment of advanced MF and SS still remains challenging. Therefore, elucidation of the pathophysiology of MF/SS and development of medical treatments are desired. In this study, we focused on a molecule called OX40. We examined OX40 and OX40L expression and function using clinical samples of MF and SS and CTCL cell lines. OX40 and OX40L were co-expressed on tumor cells of MF and SS. OX40 and OX40L expression was increased and correlated with disease severity markers in MF/SS patients. Anti-OX40 antibody and anti-OX40L antibody suppressed the proliferation of CTCL cell lines both in vitro and in vivo. These results suggest that OX40–OX40L interactions could contribute to the proliferation of MF/SS tumor cells and that the disruption of OX40–OX40L interactions could become a new therapeutic strategy for the treatment of MF/SS.

Tumor eradicated by combination of imiquimod and OX40 agonist for in situ vaccination

Various cancer vaccines have been developed to generate and amplify antigen‐specific T cell responses against malignancy. Among them, in situ vaccination is one of the most practical types as it can trigger immune responses without previous antigen identification. Here we reported a novel in situ vaccine by intratumoral injection of imiquimod and OX40 agonist. In mice bearing hepatic carcinoma, both the injected tumor and the noninjected tumor in the distant lesion of the same mice were suppressed after vaccination. Further studies found that this in situ vaccine triggered systemic tumor‐specific responses, with one‐fold increase of effector memory T cells properties and stronger toxicity of lymphocytes in spleen. Besides, we found that imiquimod upregulated the expression of OX40 on CD4⁺ T cells and thus enhanced the effectiveness of OX40 agonist. Five immune‐positive‐related pathways were activated after vaccination. This in situ vaccine caused little harm to normal organs and provided long‐term protection against the same syngeneic tumor rechallenge. Due to its effectiveness, feasibility and safety, this strategy could potentially be applied to various types of late‐stage solid tumors and worthy of further clinical research.

CD40 Activity on Mesenchymal Cells Negatively Regulates OX40L to Maintain Bone Marrow Immune Homeostasis Under Stress Conditions

Background

Within the bone marrow (BM), mature T cells are maintained under homeostatic conditions to facilitate proper hematopoietic development. This homeostasis depends upon a peculiar elevated frequency of regulatory T cells (Tregs) and immune regulatory activities from BM-mesenchymal stem cells (BM-MSCs). In response to BM transplantation (BMT), the conditioning regimen exposes the BM to a dramatic induction of inflammatory cytokines and causes an unbalanced T-effector (Teff) and Treg ratio. This imbalance negatively impacts hematopoiesis, particularly in regard to B-cell lymphopoiesis that requires an intact cross-talk between BM-MSCs and Tregs. The mechanisms underlying the ability of BM-MSCs to restore Treg homeostasis and proper B-cell development are currently unknown.

Methods

We studied the role of host radio-resistant cell-derived CD40 in restoring Teff/Treg homeostasis and proper B-cell development in a murine model of BMT. We characterized the host cellular source of CD40 and performed radiation chimera analyses by transplanting WT or Cd40-KO with WT BM in the presence of T-reg and co-infusing WT or - Cd40-KO BM-MSCs. Residual host and donor T cell expansion and activation (cytokine production) and also the expression of Treg fitness markers and conversion to Th17 were analyzed. The presence of Cd40+ BM-MSCs was analyzed in a human setting in correlation with the frequency of B-cell precursors in patients who underwent HSCT and variably developed acute graft-versus-host (aGVDH) disease.

Results

CD40 expression is nearly undetectable in the BM, yet a Cd40-KO recipient of WT donor chimera exhibited impaired B-cell lymphopoiesis and Treg development. Lethal irradiation promotes CD40 and OX40L expression in radio-resistant BM-MSCs through the induction of pro-inflammatory cytokines. OX40L favors Teff expansion and activation at the expense of Tregs; however, the expression of CD40 dampens OX40L expression and restores Treg homeostasis, thus facilitating proper B-cell development. Indeed, in contrast to dendritic cells in secondary lymphoid organs that require CD40 triggers to express OX40L, BM-MSCs require CD40 to inhibit OX40L expression.

Conclusions

CD40+ BM-MSCs are immune regulatory elements within BM. Loss of CD40 results in uncontrolled T cell activation due to a reduced number of Tregs, and B-cell development is consequently impaired. GVHD provides an example of how a loss of CD40+ BM-MSCs and a reduction in B-cell precursors may occur in a human setting.

Immunomodulatory drugs suppress Th1-inducing ability of dendritic cells but enhance Th2-mediated allergic responses

Immunomodulatory drugs (IMiDs), lenalidomide and pomalidomide, are widely used treatments for multiple myeloma; however, they occasionally lead to episodes of itchy skin and rashes. Here, we analyzed the effects of IMiDs on human myeloid dendritic cells (mDCs) as major regulators of Th1 or Th2 responses and the role they play in allergy. We found that lenalidomide and pomalidomide used at clinical concentrations did not affect the survival or CD86 and OX40-ligand expression of blood mDCs in response to lipopolysaccharide (LPS) and thymic stromal lymphopoietin (TSLP) stimulation. Both lenalidomide and pomalidomide dose-dependently inhibited interleukin-12 (IL-12) and TNF production and STAT4 expression, and enhanced IL-10 production in response to LPS. When stimulated with TSLP, both IMiDs significantly enhanced CCL17 production and STAT6 and IRF4 expression and promoted memory Th2-cell responses. In 46 myeloma patients, serum CCL17 levels at the onset of lenalidomide-associated rash were significantly higher than those without rashes during lenalidomide treatment and those before treatment. Furthermore, serum CCL17 levels in patients who achieved a very good partial response (VGPR) were significantly higher compared with a less than VGPR during lenalidomide treatment. The median time to next treatment was significantly longer in lenalidomide-treated patients with rashes than those without. Collectively, IMiDs suppressed the Th1-inducing capacity of DCs, instead promoting a Th2 response. Thus, the lenalidomide-associated rashes might be a result of an allergic response driven by Th2-axis activation. Our findings suggest clinical efficacy and rashes as a side effect of IMiDs are inextricably linked through immunostimulation.

The Roles of Immunoregulatory Networks in Severe Drug Hypersensitivity

The immunomodulatory effects of regulatory T cells (Tregs) and co-signaling receptors have gained much attention, as they help balance immunogenic and immunotolerant responses that may be disrupted in autoimmune and infectious diseases. Drug hypersensitivity has a myriad of manifestations, which ranges from the mild maculopapular exanthema to the severe Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug reaction with eosinophilia and systemic symptoms/drug-induced hypersensitivity syndrome (DRESS/DIHS). While studies have identified high-risk human leukocyte antigen (HLA) allotypes, the presence of the HLA allotype at risk is not sufficient to elicit drug hypersensitivity. Recent studies have suggested that insufficient regulation by Tregs may play a role in severe hypersensitivity reactions. Furthermore, immune checkpoint inhibitors, such as anti-CTLA-4 or anti-PD-1, in cancer treatment also induce hypersensitivity reactions including SJS/TEN and DRESS/DIHS. Taken together, mechanisms involving both Tregs as well as coinhibitory and costimulatory receptors may be crucial in the pathogenesis of drug hypersensitivity. In this review, we summarize the currently implicated roles of co-signaling receptors and Tregs in delayed-type drug hypersensitivity in the hope of identifying potential pharmacologic targets.

OX40 costimulation by a chimeric antigen receptor abrogates CD28 and IL-2 induced IL-10 secretion by redirected CD4(+) T cells

Adoptive therapy with chimeric antigen receptor (CAR) redirected T cells recently showed remarkable anti-tumor efficacy in early phase clinical trials; self-repression of the immune response by T-cell secreted cytokines, however, is still an issue raising interest to abrogate the secretion of repressive cytokines while preserving the panel of CAR induced pro-inflammatory cytokines. We here revealed that T-cell activation by a CD28-ζ signaling CAR induced IL-10 secretion, which compromises T cell based immunity, along with the release of pro-inflammatory IFN-γ and IL-2. T cells stimulated by a ζ CAR without costimulation did not secrete IL-2 or IL-10; the latter, however, could be induced by supplementation with IL-2. Abrogation of CD28-ζ CAR induced IL-2 release by CD28 mutation did not reduce IL-10 secretion indicating that IL-10 can be induced by both a CD28 and an IL-2 mediated pathway. In contrast to the CD28-ζ CAR, a CAR with OX40 (CD134) costimulation did not induce IL-10. OX40 cosignaling by a 3rd generation CD28-ζ-OX40 CAR repressed CD28 induced IL-10 secretion but did not affect the secretion of pro-inflammatory cytokines, T-cell amplification or T-cell mediated cytolysis. IL-2 induced IL-10 was also repressed by OX40 co-signaling. OX40 moreover repressed IL-10 secretion by regulatory T cells which are strong IL-10 producers upon activation. Taken together OX40 cosignaling in CAR redirected T cell activation effectively represses IL-10 secretion which contributes to counteract self-repression and provides a rationale to explore OX40 co-signaling CARs in order to prolong a redirected T cell response.

Harnessing the Complete Repertoire of Conventional Dendritic Cell Functions for Cancer Immunotherapy

The onset of checkpoint inhibition revolutionized the treatment of cancer. However, studies from the last decade suggested that the sole enhancement of T cell functionality might not suffice to fight malignancies in all individuals. Dendritic cells (DCs) are not only part of the innate immune system, but also generals of adaptive immunity and they orchestrate the de novo induction of tolerogenic and immunogenic T cell responses. Thus, combinatorial approaches addressing DCs and T cells in parallel represent an attractive strategy to achieve higher response rates across patients. However, this requires profound knowledge about the dynamic interplay of DCs, T cells, other immune and tumor cells. Here, we summarize the DC subsets present in mice and men and highlight conserved and divergent characteristics between different subsets and species. Thereby, we supply a resource of the molecular players involved in key functional features of DCs ranging from their sentinel function, the translation of the sensed environment at the DC:T cell interface to the resulting specialized T cell effector modules, as well as the influence of the tumor microenvironment on the DC function. As of today, mostly monocyte derived dendritic cells (moDCs) are used in autologous cell therapies after tumor antigen loading. While showing encouraging results in a fraction of patients, the overall clinical response rate is still not optimal. By disentangling the general aspects of DC biology, we provide rationales for the design of next generation DC vaccines enabling to exploit and manipulate the described pathways for the purpose of cancer immunotherapy in vivo. Finally, we discuss how DC-based vaccines might synergize with checkpoint inhibition in the treatment of malignant diseases.

Recombinant Costimulatory Fusion Proteins as Functional Immunomodulators Enhance Antitumor Activity in Murine B16F10 Melanoma

Blocking inhibitory signaling and engaging stimulatory signaling have emerged as important therapeutic modalities for cancer immunotherapy. This study aimed to investigate immunomodulatory features of three recombinant costimulatory ligand proteins in a mouse model, which are extracellular domains of OX40-ligand (OX40L), 4-1BB-ligand (4-1BBL), or two domains in tandem, fused with the transmembrane domain of diphtheria toxin (DTT), named DTT-COS1, DTT-COS2, and DTT-COS12, respectively. In vitro study showed that DTT-COS1 and DTT-COS12 had immunological activity increasing the ratio of CD8/CD4 T cells. Treatments with DTT-COS1 and DTT-COS12 dramatically generated immune protection against the B16F10 tumor challenge in both prophylactic and therapeutic efficacy. Furthermore, regarding tumor microenvironment (TME) immunomodulation, DTT-COS1 treatment increased the proportion of CD4+ effector T cells (Teff) and decreased the expression of a suppressive cytokine. Meanwhile, DTT-COS12 reduced regulatory T cells (Treg) and improved the level of stimulatory cytokines. In addition, endogenous antibodies against OX40L/4-1BBL were generated, which may help with antitumor responses. Unexpectedly, DTT-COS2 lacked antitumor effects in vitro and in vivo. Importantly, serum analysis of liver-function associated factors and pro-inflammatory cytokines demonstrated that treatments were safe formulations in mice without signs of systemic toxicity. Remarkably, DTT-COS1 and DTT-COS12 are functional immunomodulators for mouse B16F10 melanoma, creating practical preclinical value in cancer immunotherapy.

In vitro model for the assessment of human immune responses to subunit RSV vaccines

Respiratory syncytial virus (RSV) is the single most important cause of serious lower respiratory tract disease in infants and young children worldwide and a high priority for vaccine development. Despite over 50 years of research, however, no vaccine is yet available. One block to vaccine development is an incomplete understanding of the aberrant memory response to the formalin-inactivated RSV vaccine (FI-RSV) given to children in the 1960s. This vaccine caused enhanced respiratory disease (ERD) with later natural RSV infection. Concern that any non-live virus vaccine may also cause ERD has blocked development of subunit vaccines for young children. A number of animal FI-RSV studies suggest various immune mechanisms behind ERD. However, other than limited data from the original FI-RSV trial, there is no information on the human ERD-associated responses. An in vitro model with human blood specimens may shed light on the immune memory responses likely responsible for ERD. Memory T cell responses to an antigen are guided by the innate responses, particularly dendritic cells that present an antigen in conjunction with co-stimulatory molecules and cytokine signaling. Our in vitro model involves human monocyte derived dendritic cells (moDC) and allogenic T cell cultures to assess innate responses that direct T cell responses. Using this model, we evaluated human responses to live RSV, FI-RSV, and subunit RSV G vaccines (G-containing virus-like particles, G-VLP). Similar to findings in animal studies, FI-RSV induced prominent Th2/Th17-biased responses with deficient type-1 responses compared to live virus. Responses to G-VLPs were similar to live virus, i.e. biased towards a Th1 and not a Th2/Th17. Also mutating CX3C motif in G gave a more pronounced moDC responses associated with type-1 T cell responses. This in vitro model identifies human immune responses likely associated with ERD and provides another pre-clinical tool to assess the safety of RSV vaccines.

Blockade of OX40/OX40L pathway combined with ethylene-carbodiimide-fixed donor splenocytes induces donor-specific allograft tolerance in presensitized recipients

Background

Memory T cells (Tms) are the major barrier preventing long-term allograft survival in presensitized transplant recipients. The OX40/OX40L pathway is important in the induction and maintenance of Tms.

Methods

In this study, we added anti-OX40L mAb to ethylene-carbodiimide-fixed donor splenocytes (ECDI-SPs)-a method which is effective in inducing allograft tolerance in non-presensitized mouse heart transplant model. Recipient mice received heart transplantation after 6 weeks of donor skin presensitization and were treated with anti-OX40L mAb, ECDI-SPs or anti-OX40L mAb + ECDI-SPs, respectively.

Results

Our data showed that the combination of ECDI-SPs and anti-OX40L mAb induced donor-specific tolerance in skin-presensitized heart transplant recipients, with the mechanism for this being associated with suppression of Tms and upregulation of CD4⁺CD25⁺Foxp3⁺ T regulatory cells (Tregs). Importantly, CD25⁺ T-cell depletion in the combined therapy-treated recipients broke the establishment of allograft tolerance, whereas adoptive transfer of presensitization-derived T cells into tolerant recipients suppressed Tregs expansion and abolished established tolerance.

Conclusions

Blockade of OX40/OX40L pathway in combination with ECDI-SPs appears to modulate the Tms/Tregs imbalance so as to create a protective milieu and induce graft tolerance in presensitized recipients.

New pathways in immune stimulation: targeting OX40

Immune checkpoint blockers (ICB) reinvigorate the immune system by removing the molecular brakes responsible for the scarce activity of immune phenotypes against malignant cells. After having proven their remarkable role as monotherapy, combinations of anti-Programmed cell death 1 (PD-1)/Programmed death-ligand 1 (PD-L1) agents with cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) antibodies, chemotherapy and/or anti-angiogenic compounds provide unprecedented results and durable responses across a variety of tumour types. Nevertheless, the main drawbacks of ICB are represented by primary and acquired resistance, translating into disease progression, as well as by immune-related toxicities. In this sense, novel strategies to foster the immune system through its direct stimulation are being tested in order to provide additional clinical improvements in patients with cancer. In this scenario, the co-stimulatory molecule OX40 (CD134) belongs to the next generation of immune therapeutic targets. Preliminary results of early clinical trials evaluating OX40 stimulation by means of different agents are encouraging. Here we review the rationale of OX40 targeting, highlighting the combination of OX40-directed therapies with different anticancer agents as a potential strategy to foster the immune system against malignant phenotypes.

Reciprocal changes in CD11c+CD11b+ and CD11c+CD8α+ dendritic cell subsets determine protective or permissive immune response in murine experimental VL

CD11c⁺CD8α⁺ and CD11c⁺CD11b⁺ dendritic cells are two major subsets of murine splenic CD11c⁺ DCs which play a crucial role in T cell priming and shaping Th1/Th2 responses, but their role in the context of experimental visceral leishmaniasis (VL) is poorly understood. Herein, we showed that L. donovani infection in Balb/c mice preferentially decreased the population abundance of CD11c⁺CD11b⁺ DCs and increased relative abundance of splenic CD11c⁺CD8α ⁺DCs. During infection, splenic CD11c⁺CD11b⁺ DCs induced Th1 differentiation whereas CD11c⁺CD8α⁺ DCs promoted Th2 differentiation. Additionally, treatment of infected mice with miltefosine as experimental control exhibited host defense allowing the restoration of CD11c⁺CD11b⁺ population and decrease in CD11c⁺CD8α⁺ subset. Furthermore, reciprocal regulation of immune accessory surface molecules, Sema4A and OX40L critically determined Th1/Th2 response induced by these DC subsets during VL. L. donovani infection significantly induced OX40L expression and slightly downregulated SEMA 4A expression in CD11c⁺CD8α⁺ DCs whereas miltefosine treatment significantly downregulated OX40L expression along with pronounced upregulation of SEMA 4A expression in CD11c⁺CD11b⁺ DCs. SiRNA mediated knockdown of SEMA 4A markedly reduced CD11c⁺CD11b⁺ driven IFN-γ, TNF-α and IL-12 synthesis in miltefosine treated mice whereas functional blocking of OX40L decreased CD11c⁺CD8α⁺ induced IL-10, IL-4 and TGF-β synthesis in L. donovani infected group. Vaccination of Balb/c mice with antigen-pulsed + CpG-ODN-activated DC subsets revealed that only antigen-pulsed CD11c⁺CD11b⁺ DCs eliminated parasite load in visceral organ and restored protective Th1 cytokine response. Collectively, our results suggest that differential regulation of splenic CD11c⁺ subsets by L. donovani is essential for disease progression and specific subtypes may be exploited as prophylactic measures against visceral leishmaniasis.

OX40 ligand is inhibitory during the effector phase of crescentic glomerulonephritis

BACKGROUND

The functional relevance of OX40 ligand (OX40L) in the effector phase of crescentic glomerulonephritis (GN) is unknown. These studies defined the role of endogenous OX40L during the effector stage of murine crescentic GN.

METHODS

GN was induced by immunization with sheep globulin/adjuvant on Day 0 and injection of sheep anti-mouse glomerular basement membrane immunoglobulin (Ig) on Day 10. Rat IgG or neutralizing anti-OX40L antibody was administered on Days 10-18 and immune responses and renal injury assessed on Day 20.

RESULTS

Compared with naïve animals, OX40L was upregulated in the lymph nodes (LNs) and on leucocytes and resident non-immune cells in the kidneys of mice with GN. Inhibition of OX40L in GN augmented renal injury, as indicated by increased crescent formation, proteinuria and glomerular leucocyte accumulation. In line with increased injury, anti-OX40L treatment increased proliferation and decreased apoptosis of CD4 T cells in the LNs, without affecting LN CD4 cytokine production and CD8 T-cell responses. Blockade of OX40L decreased LN regulatory T-cell (Treg) proliferation, transforming growth factor β production and foxp3 expression. OX40L inhibition did not affect B cell expansion or circulating antibody levels. In the kidney, neutralization of OX40L augmented interferon γ (IFNγ) expression by CD4 and CD8 T cells and shifted macrophage polarization towards the pro-inflammatory M1 phenotype.

CONCLUSIONS

OX40L is protective during the effector phase of murine crescentic GN by reducing the expansion of CD4 T cells and enhancing Treg responses in the LNs, and by locally inhibiting T-cell IFNγ production and pro-inflammatory macrophage phenotype in the kidney.

Costimulation Blockade in Transplantation

T cells play a pivotal role in orchestrating immune responses directed against a foreign (allogeneic) graft. For T cells to become fully activated, the T-cell receptor (TCR) must interact with the major histocompatibility complex (MHC) plus peptide complex on antigen-presenting cells (APCs), followed by a second "positive" costimulatory signal. In the absence of this second signal, T cells become anergic or undergo deletion. By blocking positive costimulatory signaling, T-cell allo-responses can be aborted, thus preventing graft rejection and promoting long-term allograft survival and possibly tolerance (Alegre ML, Najafian N, Curr Mol Med 6:843-857, 2006; Li XC, Rothstein DM, Sayegh MH, Immunol Rev 229:271-293, 2009). In addition, costimulatory molecules can provide negative "coinhibitory" signals that inhibit T-cell activation and terminate immune responses; strategies to promote these pathways can also lead to graft tolerance (Boenisch O, Sayegh MH, Najafian N, Curr Opin Organ Transplant 13:373-378, 2008). However, T-cell costimulation involves an incredibly complex array of interactions that may act simultaneously or at different times in the immune response and whose relative importance varies depending on the different T-cell subsets and activation status. In transplantation, the presence of foreign alloantigen incites not only destructive T effector cells but also protective regulatory T cells, the balance of which ultimately determines the fate of the allograft (Lechler RI, Garden OA, Turka LA, Nat Rev Immunol 3:147-158, 2003). Since the processes of alloantigen-specific rejection and regulation both require activation of T cells, costimulatory interactions may have opposing or synergistic roles depending on the cell being targeted. Such complexities present both challenges and opportunities in targeting T-cell costimulatory pathways for therapeutic purposes. In this chapter, we summarize our current knowledge of the various costimulatory pathways in transplantation and review the current state and challenges of harnessing these pathways to promote graft tolerance (summarized in Table 10.1).

Role of Co-stimulatory Molecules in T Helper Cell Differentiation

CD4⁺ T cells play a central role in orchestrating the immune response to a variety of pathogens but also regulate autoimmune responses, asthma, allergic responses, as well as tumor immunity. To cover this broad spectrum of responses, naïve CD4⁺ T cells differentiate into one of several lineages of T helper cells, including Th1, Th2, Th17, and T_FH, as defined by their cytokine pattern and function. The fate decision of T helper cell differentiation integrates signals delivered through the T cell receptor, cytokine receptors, and the pattern of co-stimulatory signals received. In this review, we summarize the contribution of co-stimulatory and co-inhibitory receptors to the differentiation and maintenance of T helper cell responses.

Statins can suppress DC-mediated Th2 responses through the repression of OX40-ligand and CCL17 expression

DCs and epithelial cell-derived thymic stromal lymphopoietin (TSLP) have pivotal roles in allergic inflammation. TSLP stimulates myeloid DCs to express OX40-ligand (OX40L) and CCL17, which trigger and maintain Th2 cell responses. We have previously shown that statins, which are HMG-CoA reductase inhibitors, have the ability to suppress type I IFN production by plasmacytoid DCs. Here, we extended our previous work to examine the immunomodulatory effect of statins on allergic responses, particularly the TSLP-dependent Th2 pathway induced by myeloid DCs. We found that treatment of TSLP-stimulated DCs with either pitavastatin or simvastatin suppressed both the DC-mediated inflammatory Th2 cell differentiation and CRTH2+ CD4+ memory Th2 cell expansion and also repressed the expressions of OX40L and CCL17 by DCs. These inhibitory effects of statins were mimicked by treatment with either a geranylgeranyl-transferase inhibitor or Rho-kinase inhibitor and were counteracted by the addition of mevalonate, suggesting that statins induce geranylgeranylated Rho inactivation through a mevalonate-dependent pathway. We also found that statins inhibited the expressions of phosphorylated STA6 and NF-κB-p50 in TSLP-stimulated DCs. This study identified a specific ability of statins to control DC-mediated Th2 responses, suggesting their therapeutic potential for treating allergic diseases.

ILC3-derived OX40L is essential for homeostasis of intestinal Tregs in immunodeficient mice

OX40L is one of the co-stimulatory molecules that can be expressed by splenic lymphoid tissue inducer (Lti) cells, a subset of group 3 innate lymphoid cells (ILC3s). OX40L expression in subsets of intestinal ILC3s and the molecular regulation of OX40L expression in ILC3s are unknown. Here, we showed intestinal ILC3s marked as an OX40L^high population among all the intestinal leukocytes and were the dominant source of OX40L in Rag1^-/- mice. All ILC3 subsets expressed OX40L, and NCR^-ILC3s were the most abundant source of OX40L. The expression of OX40L in ILC3s could be upregulated during inflammation. In addition to tumor necrosis factor (TNF)-like cytokine 1A (TL1A), which has been known as a trigger for OX40L, we found that Poly (I:C) representing viral stimulus promoted OX40L expression in ILC3s via a cell-autonomous manner. Furthermore, we demonstrated that IL-7-STAT5 signaling sustained OX40L expression by ILC3s. Intestinal regulatory T cells (Tregs), most of which expressed OX40, had defective expansion in chimeric mice, in which ILC3s were specifically deficient for OX40L expression. Consistently, co-localization of Tregs and ILC3s was found in the cryptopatches of the intestine, which suggests the close interaction between ILC3s and Tregs. Our study has unveiled the crosstalk between Tregs and ILC3s in mucosal tissues through OX40-OX40L signaling, which is crucial for the homeostasis of intestinal Tregs.

IL-33 drives influenza-induced asthma exacerbations by halting innate and adaptive antiviral immunity

BACKGROUND

Influenza virus triggers severe asthma exacerbations for which no adequate treatment is available. It is known that IL-33 levels correlate with exacerbation severity, but its role in the immunopathogenesis of exacerbations has remained elusive.

OBJECTIVE

We hypothesized that IL-33 is necessary to drive asthma exacerbations. We intervened with the IL-33 cascade and sought to dissect its role, also in synergy with thymic stromal lymphopoietin (TSLP), in airway inflammation, antiviral activity, and lung function. We aimed to unveil the major source of IL-33 in the airways and IL-33-dependent mechanisms that underlie severe asthma exacerbations.

METHODS

Patients with mild asthma were experimentally infected with rhinovirus. Mice were chronically exposed to house dust mite extract and then infected with influenza to resemble key features of exacerbations in human subjects. Interventions included the anti-IL-33 receptor ST2, anti-TSLP, or both.

RESULTS

We identified bronchial ciliated cells and type II alveolar cells as a major local source of IL-33 during virus-driven exacerbation in human subjects and mice, respectively. By blocking ST2, we demonstrated that IL-33 and not TSLP was necessary to drive exacerbations. IL-33 enhanced airway hyperresponsiveness and airway inflammation by suppressing innate and adaptive antiviral responses and by instructing epithelial cells and dendritic cells of house dust mite-sensitized mice to dampen IFN-β expression and prevent the T_H1-promoting dendritic cell phenotype. IL-33 also boosted luminal NETosis and halted cytolytic antiviral activities but did not affect the T_H2 response.

CONCLUSION

Interventions targeting the IL-33/ST2 axis could prove an effective acute short-term therapy for virus-induced asthma exacerbations.

Identification of a Novel OX40L+ Dendritic Cell Subset That Selectively Expands Regulatory T cells

We have previously shown GM-CSF derived bone-marrow dendritic cells (G-BMDCs) can induce the selective expansion of Tregs through the surface-bound molecule OX40L; however, the physiological role of this ex vivo derived DC subset remained to be elucidated. We determined GM-CSF administration to mice induced the generation of in vivo derived OX40L⁺ DCs, phenotypically similar to ex vivo OX40L⁺G-BMDCs, in the spleen, brachial lymph nodes and liver. The generation of OX40L⁺ DCs correlated with increased percentages of functionally suppressive Tregs in the spleen, brachial lymph nodes, and liver of GM-CSF treated mice. DCs from GM-CSF treated mice expanded Tregs in CD4⁺ T-cell co-cultures in an OX40L dependent manner, suggesting OX40L⁺ DCs may play a role in peripheral Treg homeostasis. Furthermore, comparing the transcriptome data of OX40L⁺ DCs to that of all immune cell types revealed OX40L⁺ DCs to be distinct from steady-state immune cells and, microarray analysis of OX40L⁺G-BMDCs and OX40L⁻G-BMDCs revealed higher expression of molecules that are associated with tolerogenic phenotype and could play important roles in the function of OX40L⁺ DCs. These findings suggest that OX40L⁺ DCs may represent a unique DC subset induced under inflammatory conditions that may play an essential role in maintaining Treg homeostasis.

Emerging strategies for combination checkpoint modulators in cancer immunotherapy

Current immune checkpoint-modulating agents have demonstrated clinical efficacy in certain tumor types, particularly those with a high burden of tumor-specific neoantigens, high tumor-mutational burden, and abundant tumor-infiltrating T cells. However, these tumors often stop responding, with signs of T cells exhaustion, decreased T cell effector function, and upregulated inhibitory checkpoints. To enhance antitumor immunity and rescue exhausted T cells, newer inhibitory and stimulatory checkpoint modulators are being tested as monotherapy or in combination with approved checkpoint inhibitors. In contrast, tumors with low tumor-mutational burden, low neoantigen burden, and a paucity of T cells are immunologically "cold," and therefore first require the addition of agents to facilitate the induction of T cells into tumors. Cold tumors also often recruit immunosuppressive cell subsets, including regulatory T cells, myeloid-derived suppressor cells, and macrophages, and secrete immunosuppressive soluble cytokines, chemokines, and metabolites. To unleash an optimal antitumor immune response, combinatorial therapeutics that combine immune checkpoints with other modalities, such as vaccines, are being developed. From current preclinical data, it appears that combinatorial strategies will provide robust and durable responses in patients with immunologically cold cancers.

Development of third generation anti-EGFRvIII chimeric T cells and EGFRvIII-expressing artificial antigen presenting cells for adoptive cell therapy for glioma

Glioblastoma multiforme (GBM) is the most aggressive and deadly form of adult brain cancer. Despite of many attempts to identify potential therapies for this disease, including promising cancer immunotherapy approaches, it remains incurable. To address the need of improved persistence, expansion, and optimal antitumor activity of T-cells in the glioma milieu, we have developed an EGFRvIII-specific third generation (G3-EGFRvIII) chimeric antigen receptor (CAR) that expresses both co-stimulatory factors CD28 and OX40 (MR1-CD8TM-CD28-OX40-CD3ζ). To enhance ex vivo target specific activation and optimize T-cell culturing conditions, we generated artificial antigen presenting cell lines (aAPC) expressing the extracellular and transmembrane domain of EGFRvIII (EGFRVIIIΔ654) with costimulatory molecules including CD32, CD80 and 4-1BBL (EGFRVIIIΔ654 aAPC and CD32-80-137L-EGFRVIIIΔ654 aAPC). We demonstrate that the highest cell growth was achieved when G3-EGFRvIII CAR T-cells were cocultured with both co-stimulatory aAPCs and with exposure to EGFRvIII (CD32-80-137L-EGFRVIIIΔ654 aAPCs) in culturing periods of three to six weeks. G3-EGFRvIII CAR T-cells showed an increased level of IFN-γ when cocultured with CD32-80-137L-EGFRVIIIΔ654 aAPCs. Evaluation of G3-EGFRvIII CAR T-cells in an orthotropic human glioma xenograft model demonstrated a prolonged survival of G3-EGFRvIII CAR treated mice compared to control mice. Importantly, we observed survival of G3-EGFRvIII CAR T-cells within the tumor as long as 90 days after implantation in low-dose and single administration, accompanied by a marked tumor stroma demolition. These findings suggest that G3-EGFRvIII CAR cocultured with CD32-80-137L-EGFRVIIIΔ654 aAPCs warrants itself as a potential anti-tumor therapy strategy for glioblastoma.

Combined OX40L and mTOR blockade controls effector T cell activation while preserving Treg reconstitution after transplant

A critical question facing the field of transplantation is how to control effector T cell (T_eff) activation while preserving regulatory T cell (T_reg) function. Standard calcineurin inhibitor-based strategies can partially control T_effs, but breakthrough activation still occurs, and these agents are antagonistic to T_reg function. Conversely, mechanistic target of rapamycin (mTOR) inhibition with sirolimus is more T_reg-compatible but is inadequate to fully control T_eff activation. In contrast, blockade of OX40L signaling has the capacity to partially control T_eff activation despite maintaining T_reg function. We used the nonhuman primate graft-versus-host disease (GVHD) model to probe the efficacy of combinatorial immunomodulation with sirolimus and the OX40L-blocking antibody KY1005. Our results demonstrate significant biologic activity of KY1005 alone (prolonging median GVHD-free survival from 8 to 19.5 days), as well as marked, synergistic control of GVHD with KY1005 + sirolimus (median survival time, >100 days; P < 0.01 compared to all other regimens), which was associated with potent control of both T_H/T_C1 (T helper cell 1/cytotoxic T cell 1) and T_H/T_C17 activation. Combined administration also maintained T_reg reconstitution [resulting in an enhanced T_reg/T_eff ratio (40% over baseline) in the KY1005/sirolimus cohort compared to a 2.9-fold decrease in the unprophylaxed GVHD cohort]. This unique immunologic signature resulted in transplant recipients that were able to control GVHD for the length of analysis and to down-regulate donor/recipient alloreactivity despite maintaining anti-third-party responses. These data indicate that combined OX40L blockade and sirolimus represents a promising strategy to induce immune balance after transplant and is an important candidate regimen for clinical translation.

B cell OX40L supports T follicular helper cell development and contributes to SLE pathogenesis

Objectives

TNFSF4 (encodes OX40L) is a susceptibility locus for systemic lupus erythematosus (SLE). Risk alleles increase TNFSF4 expression in cell lines, but the mechanism linking this effect to disease is unclear, and the OX40L-expressing cell types mediating the risk are not clearly established. Blockade of OX40L has been demonstrated to reduce disease severity in several models of autoimmunity, but not in SLE. We sought to investigate its potential therapeutic role in lupus.

Methods

We used a conditional knockout mouse system to investigate the function of OX40L on B and T lymphocytes in systemic autoimmunity.

Results

Physiologically, OX40L on both B and T cells contributed to the humoral immune response, but B cell OX40L supported the secondary humoral response and antibody affinity maturation. Our data also indicated that loss of B cell OX40L impeded the generation of splenic T follicular helper cells. We further show that in two models of SLE—a spontaneous congenic model and the H2-IA^bm12 graft-versus-host-induced model—loss of B cell OX40L ameliorates the autoimmune phenotype. This improvement was, in each case, accompanied by a decline in T follicular helper cell numbers. Importantly, the germline knockout did not exhibit a markedly different phenotype from the B cell knockout in these models.

Conclusions

These findings contribute to a model in which genetically determined increased OX40L expression promotes human SLE by several mechanisms, contingent on its cellular expression. The improvement in pathology in two models of systemic autoimmunity indicates that OX40L is an excellent therapeutic target in SLE.

The Ox40/Ox40 Ligand Pathway Promotes Pathogenic Th Cell Responses, Plasmablast Accumulation, and Lupus Nephritis in NZB/W F1 Mice

Ox40 ligand (Ox40L) locus genetic variants are associated with the risk for systemic lupus erythematosus (SLE); however, it is unclear how Ox40L contributes to SLE pathogenesis. In this study, we evaluated the contribution of Ox40L and its cognate receptor, Ox40, using in vivo agonist and antagonist approaches in the NZB × NZW (NZB/W) F1 mouse model of SLE. Ox40 was highly expressed on several CD4 Th cell subsets in the spleen and kidney of diseased mice, and expression correlated with disease severity. Treatment of aged NZB/W F1 mice with agonist anti-Ox40 mAbs potently exacerbated renal disease, which was accompanied by activation of kidney-infiltrating T cells and cytokine production. The agonist mAbs also induced activation and inflammatory gene expression in splenic CD4 T cells, including IFN-regulated genes, increased the number of follicular helper T cells and plasmablasts in the spleen, and led to elevated levels of serum IgM and enhanced renal glomerular IgM deposition. In a type I IFN-accelerated lupus model, treatment with an antagonist Ox40:Fc fusion protein significantly delayed the onset of severe proteinuria and improved survival. These data support the hypothesis that the Ox40/Ox40L pathway drives cellular and humoral autoimmune responses during lupus nephritis in NZB/W F1 mice and emphasize the potential clinical value of targeting this pathway in human lupus.

ATVB Distinguished Scientist Award: How Costimulatory and Coinhibitory Pathways Shape Atherosclerosis

OBJECTIVE

Immune cells play a critical role in atherosclerosis. Costimulatory and coinhibitory molecules of the tumor necrosis factor receptor and CD28 immunoglobulin superfamilies not only shape T-cell and B-cell responses but also have a major effect on antigen-presenting cells and nonimmune cells.

APPROACH AND RESULTS

Pharmacological inhibition or activation of costimulatory and coinhibitory molecules and genetic deletion demonstrated their involvement in atherosclerosis. This review highlights recent advances in understanding how costimulatory and coinhibitory pathways shape the immune response in atherosclerosis.

CONCLUSIONS

Insights gained from costimulatory and coinhibitory molecule function in atherosclerosis may inform future therapeutic approaches.

Advances in targeting co-inhibitory and co-stimulatory pathways in transplantation settings: the Yin to the Yang of cancer immunotherapy

In the past decade, the power of harnessing T-cell co-signaling pathways has become increasingly understood to have significant clinical importance. In cancer immunotherapy, the field has concentrated on two related modalities: First, targeting cancer antigens through highly activated chimeric antigen T cells (CAR-Ts) and second, re-animating endogenous quiescent T cells through checkpoint blockade. In each of these strategies, the therapeutic goal is to re-ignite T-cell immunity, in order to eradicate tumors. In transplantation, there is also great interest in targeting T-cell co-signaling, but with the opposite goal: in this field, we seek the Yin to cancer immunotherapy's Yang, and focus on manipulating T-cell co-signaling to induce tolerance rather than activation. In this review, we discuss the major T-cell signaling pathways that are being investigated for tolerance induction, detailing preclinical studies and the path to the clinic for many of these molecules. These include blockade of co-stimulation pathways and agonism of coinhibitory pathways, in order to achieve the delicate state of balance that is transplant tolerance: a state which guarantees lifelong transplant acceptance without ongoing immunosuppression, and with preservation of protective immune responses. In the context of the clinical translation of immune tolerance strategies, we discuss the significant challenge that is embodied by the fact that targeted pathway modulators may have opposing effects on tolerance based on their impact on effector vs regulatory T-cell biology. Achieving this delicate balance holds the key to the major challenge of transplantation: lifelong control of alloreactivity while maintaining an otherwise intact immune system.

Is There Still Room for Cancer Vaccines at the Era of Checkpoint Inhibitors

Checkpoint inhibitor (CPI) blockade is considered to be a revolution in cancer therapy, although most patients (70%–80%) remain resistant to this therapy. It has been hypothesized that only tumors with high mutation rates generate a natural antitumor T cell response, which could be revigorated by this therapy. In patients with no pre-existing antitumor T cells, a vaccine-induced T cell response is a rational option to counteract clinical resistance. This hypothesis has been validated in preclinical models using various cancer vaccines combined with inhibitory pathway blockade (PD-1-PDL1-2, CTLA-4-CD80-CD86). Enhanced T cell infiltration of various tumors has been demonstrated following this combination therapy. The timing of this combination appears to be critical to the success of this therapy and multiple combinations of immunomodulating antibodies (CPI antagonists or costimulatory pathway agonists) have reinforced the synergy with cancer vaccines. Only limited results are available in humans and this combined approach has yet to be validated. Comprehensive monitoring of the regulation of CPI and costimulatory molecules after administration of immunomodulatory antibodies (anti-PD1/PD-L1, anti-CTLA-4, anti-OX40, etc.) and cancer vaccines should help to guide the selection of the best combination and timing of this therapy.

Critical Role of Transcription Factor PU.1 in the Function of the OX40L/TNFSF4 Promoter in Dendritic Cells

PU.1 is a hematopoietic lineage-specific transcription factor belonging to the Ets family. We investigated the role of PU.1 in the expression of OX40L in dendritic cells (DCs), because the regulatory mechanism of cell type-specific expression of OX40L, which is mainly restricted to antigen-presenting cells, is largely unknown despite the critical involvement in Th2 and Tfh development. PU.1 knockdown decreased the expression of OX40L in mouse DCs. Chromatin immunoprecipitation (ChIP) assays demonstrated that PU.1 constitutively bound to the proximal region of the OX40L promoter. Reporter assays and electrophoretic mobility shift assays revealed that PU.1 transactivated the OX40L promoter through direct binding to the most-proximal Ets motif. We found that this Ets motif is conserved between mouse and human, and that PU.1 bound to the human OX40L promoter in ChIP assay using human monocyte-derived DCs. ChIP assays based on ChIP-seq datasets revealed that PU.1 binds to several sites distant from the transcription start site on the OX40L gene in addition to the most-proximal site in mouse DCs. In the present study, the structure of the OX40L promoter regulated by PU.1 is determined. It is also suggested that PU.1 is involved in mouse OX40L expression via multiple binding sites on the gene.

Clinical trials exploring the benefit of immunotherapy and radiation in cancer treatment: A review of the past and a look into the future

Cancer immunotherapy is rapidly redefining the standard of cancer care. The role of radiation therapy in eliciting antitumoral immune response is also being actively investigated in combination with various immunotherapeutic agents to exploit potential synergy between the 2 modalities. In this review, we summarize the rationale and results of past and ongoing clinical trials that combined the use of radiation therapy and immunogenic agents such as vaccines, cytokines, immune checkpoint inhibitors, costimulatory agonists, and myeloid activators.

Role of Tumor Necrosis Factor Superfamily in Neuroinflammation and Autoimmunity

Tumor necrosis factor superfamily (TNFSF) molecules play an important role in the activation, proliferation, differentiation, and migration of immune cells into the central nervous system (CNS). Several TNF superfamily molecules are known to control alloimmunity, autoimmunity, and immunity. Development of transgenic and gene knockout animals, and monoclonal antibodies against TNFSF molecules have increased our understanding of individual receptor-ligand interactions, and their intracellular signaling during homeostasis and neuroinflammation. A strong clinical association has been observed between TNFSF members and CNS autoimmunity such as multiple sclerosis and also in its animal model experimental autoimmune encephalomyelitis. Therefore, they are promising targets for alternative therapeutic options to control autoimmunity. Although, TNFSF ligands are widely distributed and have diverse functions, we have restricted the discussions in this review to TNFSF receptor-ligand interactions and their role in the pathogenesis of neuroinflammation and CNS autoimmunity.

Combinations of immunotherapy and radiation in cancer therapy

The immune system has the ability to recognize and specifically reject tumors, and tumors only become clinically apparent once they have evaded immune destruction by creating an immunosuppressive tumor microenvironment. Radiotherapy (RT) can cause immunogenic tumor cell death resulting in cross-priming of tumor-specific T-cells, acting as an in situ tumor vaccine; however, RT alone rarely induces effective anti-tumor immunity resulting in systemic tumor rejection. Immunotherapy can complement RT to help overcome tumor-induced immune suppression, as demonstrated in pre-clinical tumor models. Here, we provide the rationale for combinations of different immunotherapies and RT, and review the pre-clinical and emerging clinical evidence for these combinations in the treatment of cancer.

Myeloid dendritic cells are primed in allergic asthma for thymic stromal lymphopoietin-mediated induction of Th2 and Th9 responses

BACKGROUND

Type 1 myeloid dendritic cells (mDCs) contribute to inception of allergic asthma (AA) and are regulated by epithelial-derived cytokines.

OBJECTIVES

To evaluate whether mDCs from AA patients are primed for thymic stromal lymphopoietin (TSLP)-driven responses.

METHODS

mDCs from 18 AA patients and 15 controls were purified using immunomagnetic sorting. Cells were pulsed with TSLP or Dermatophagoides pteronyssinus (Der p) allergen, before FACS phenotyping and co-culture with allogeneic CD4+ T cells. Bronchial biopsies from 15 AA patients and four controls were immunostained for CD1c and TSLP receptor (TSLPR).

RESULTS

Allergic asthma patients had a higher proportion of TSLPR+ mDCs, in blood and bronchial mucosa. When compared to mDCs from controls, both TSLP- and Der p-pulsed blood mDCs from AA patients induced increased polarization of CD4+ T cells into Th2 cells (IL-5, IL-13, and GATA3+), while only TSLP-mDCs promoted Th9 cells (IL-9 and PU.1+ /IRF4+). In addition, OX40L was induced upon TSLP stimulation and was required for the induction of Th2, but not Th9, cells. In contrast, development of Th9 cells in this model depended on TGF-β1.

CONCLUSIONS

Our data indicate overlapping but partially distinct effects of TSLP and Der p allergen pathways, showing that DCs are primed in human asthma for TSLP-driven induction of both Th2 and Th9 cells. This novel TSLP/mDC/Th9 axis operates through a distinct, OX40L-independent pathway. These data further highlight the TSLP pathway as a relevant target in human asthma.

Manipulation of costimulatory pathways in autoimmune diseases

Abstract There has recently been an increased understanding of the role of costimulatory pathways in the activation of the immune system and the maintenance of self-tolerance. It has been suggested that the absence of costimulatory molecules on normal tissue cells could serve to induce self-tolerance, and that inappropriate expression of costimulatory molecules on antigen-presenting cells (APCs) could activate self-reactive T cells, resulting in autoimmunity. Among several costimulatory molecules characterized, the interaction of CD28/CTLA4 on T cells with B7 (CD80 and CD86) on APC appears to be of primary importance. In fact, inhibition of the CD28-B7 interaction ameliorates several autoimmune diseases in experimental animal models. However, differential roles for CD80 and CD86 have been reported in certain conditions, and CTLA4 has been shown to play a negative role in T cell activation, suggesting that the actual regulatory mechanisms of this pathway in autoimmunity is much more complex. While the CD28-B7 interaction constitutes a predominant pathway of T cell costimulation, some intact T cell responses in CD28-deficient mice have suggested the presence of alternative pathways. T cell-dependent immunity is also critically regulated not only by other immunoglobulin superfamilies such as B7RP-1/ICOS, but also by tumor necrosis factor (TNF) and TNF-receptor superfamilies, which control immune responses in both a positive and a negative fashion. Therefore, further investigation of the physiological function of these costimulatory pathways in vivo may help in developing rational therapeutic approaches for autoimmune diseases.

T-cell costimulatory blockade in organ transplantation

Before it became possible to derive T-cell lines and clones, initial experimentation on the activation requirements of T lymphocytes was performed on transformed cell lines, such as Jurkat. These studies, although technically correct, proved misleading as most transformed T cells can be activated by stimulation of the clonotypic T-cell receptor (TCR) alone. In contrast, once it became possible to study nontransformed T cells, it quickly became clear that TCR stimulation by itself is insufficient for optimal activation of naïve T cells, but in fact, induces a state of anergy. It then became clear that functional activation of T cells requires not only recognition of major histocompatibility complex (MHC) and peptide by the TCR, but also requires ligation of costimulatory receptors expressed on the cell surface.

Novel antibodies targeting immune regulatory checkpoints for cancer therapy

Cancers must evade or suppress the immune system in order to develop. Better understanding of the molecular regulation governing tumour detection and effective activation of the immune system (so called immune regulatory checkpoints) has provided new targets for cancer immunotherapy. Therapeutic monoclonal antibodies against these targets are currently undergoing clinical evaluation with more in pre-clinical development; buoyed by the recent licence approval of the anti-CTLA-4 antibody, ipilumumab, for use in melanoma. This article will review the current status of the various antibodies and target molecules being investigated.

Immunotherapy for the management of advanced melanoma: the next steps

Melanoma is an immunogenic tumor that can induce a natural immune response. A number of immunotherapy-based approaches have been developed over the past decades, and certain degrees of effectiveness were achieved by the use of cytokines, adoptive cell transfer and T-cell immune modulators. Currently, interleukin-2 and the immune stimulatory antibody, ipilimumab, are the only two approved immunotherapies for metastatic melanoma, but various new therapies are in promising developmental stages. This comprehensive review will discuss the latest achievements of immunotherapy and emerging directions for the management of advanced melanoma.

Upregulation of OX40 ligand on monocytes contributes to early virological control in patients with chronic hepatitis C

Dysfunctional hepatitis C virus (HCV) specific CD4(+) T cells are known to contribute to inadequate adaptive immunity in chronic hepatitis C (CHC), although the underlying mechanisms remain largely undefined. In this study, OX40 ligand (OX40L) expression was investigated in 41 treatment-naïve CHC patients, 20 sustained virological responders and 36 healthy subjects. We observed that OX40L expression was significantly upregulated in peripheral monocytes in CHC patients compared with sustained virological responders and healthy subjects. OX40L upregulation correlated significantly with plasma viral load rather than serum alanine aminotransaminase levels. Furthermore, longitudinal analyses indicated that upregulated OX40L expression on monocytes is closely associated with rapid or early virological responses in patients receiving pegylated IFN-α/ribavirin treatment. In vitro, HCV core antigen strongly stimulated monocyte expression of OX40L and blockade of TLR2 signaling significantly downregulated OX40L expression. More importantly, elevated OX40L expression was also shown to be closely associated with elevation of the HCV-specific CD4(+) T-cell response and in vitro blockade of OX40L expressed on monocytes led to impaired CD4(+) T-cell function. These findings, therefore, implicate OX40L expression can be used as a marker to evaluate antiviral treatment efficacy and extend the notion that enhancement of OX40L expression could be a good way for immunotherapy in CHC patients.

Natural killer cells: walking three paths down memory lane

Immunological memory has traditionally been regarded as a unique feature of the adaptive immune response, mediated in an antigen-specific manner by T and B lymphocytes. All other hematopoietic cells, including natural killer (NK) cells, are classified as innate immune cells, which have been considered short-lived but can respond rapidly against pathogens in a manner not thought to be driven by antigen. Interestingly, NK cells have recently been shown to survive long term after antigen exposure and subsequently mediate antigen-specific recall responses. In this review, we address the similarities between, and the controversies surrounding, three major viewpoints of NK memory that have arisen from these recent studies: (i) mouse cytomegalovirus (MCMV)-induced memory; (ii) cytokine-induced memory; and (iii) liver-restricted memory cells.