Critical role for OX40 ligand in the development of pathogenic Th2 cells in a murine model of asthma

TL1A priming induces a multi-cytokine Th9 cell phenotype that promotes robust allergic inflammation in murine models of asthma

Multi-cytokine-producing Th9 cells secrete IL-9 and type 2 cytokines and mediate mouse and human allergic inflammation. However, the cytokines that promote a multi-cytokine secreting phenotype have not been defined. Tumor necrosis factor superfamily member TL1A signals through its receptor DR3 to increase IL-9. Here we demonstrate that TL1A increases expression of IL-9 and IL-13 co-expressing cells in murine Th9 cell cultures, inducing a multi-cytokine phenotype. Mechanistically, this is linked to histone modifications allowing for increased accessibility at the Il9 and Il13 loci. We further show that TL1A alters the transcription factor network underlying expression of IL-9 and IL-13 in Th9 cells and increases binding of transcription factors to Il9 and Il13 loci. TL1A-priming enhances the pathogenicity of Th9 cells in murine models of allergic airway disease through the increased expression of IL-9 and IL-13. Lastly, in both chronic and memory-recall models of allergic airway disease, blockade of TL1A signaling decreases the multi-cytokine Th9 cell population and attenuates the allergic phenotype. Taken together, these data demonstrate that TL1A promotes the development of multi-cytokine Th9 cells that drive allergic airway diseases and that targeting pathogenic T helper cell-promoting cytokines could be an effective approach for modifying disease.

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.

Immune checkpoint molecules in prevention and development of asthma

Allergic asthma is a respiratory disease initiated by type-2 immune responses characterized by secretion of alarmins, interleukin-4 (IL-4), IL-5, and IL-13, eosinophilic inflammation, and airway hyperresponsiveness (AHR). Immune checkpoints (ICPs) are inhibitory or stimulatory molecules expressed on different immune cells, tumor cells, or other cell types that regulate immune system activation and maintain immune homeostasis. Compelling evidence indicates a key role for ICPs in both the progression and prevention of asthma. There is also evidence of asthma development or exacerbation in some cancer patients receiving ICP therapy. The aim of this review is to provide an updated overview of ICPs and their roles in asthma pathogenesis, and to assess their implications as therapeutic targets in asthma.

Characteristics of tumor microenvironment and novel immunotherapeutic strategies for non-small cell lung cancer

Immune checkpoint inhibitor-based immunotherapy has revolutionized the treatment approach of non-small cell lung cancer (NSCLC). Monoclonal antibodies against programmed cell death-1 (PD-1) and PD-ligand 1 (PD-L1) are widely used in clinical practice, but other antibodies that can circumvent innate and acquired resistance are bound to undergo preclinical and clinical studies. However, tumor cells can develop and facilitate the tolerogenic nature of the tumor microenvironment (TME), resulting in tumor progression. Therefore, the immune escape mechanisms exploited by growing lung cancer involve a fine interplay between all actors in the TME. A better understanding of the molecular biology of lung cancer and the cellular/molecular mechanisms involved in the crosstalk between lung cancer cells and immune cells in the TME could identify novel therapeutic weapons in the old war against lung cancer. This article discusses the role of TME in the progression of lung cancer and pinpoints possible advances and challenges of immunotherapy for NSCLC.

OX40 Expression in Eosinophils Aggravates OVA-Induced Eosinophilic Gastroenteritis

Background & Aims

Eosinophils are the main inflammatory effector cells that damage gastrointestinal tissue in eosinophilic gastrointestinal diseases (EGIDs). Activation of the OX40 pathway aggravates allergic diseases, such as asthma, but it is not clear whether OX40 is expressed in eosinophils to regulate inflammation in EGIDs. In this study, we assessed the expression and effect of OX40 on eosinophils in WT and Ox40^-/- eosinophilic gastroenteritis (EGE) mice.

Methods

Eosinophil infiltration, ovalbumin (OVA)-specific Ig production, OX40 expression and inflammatory factor levels in the intestine and bone marrow (BM) were investigated to evaluate inflammation.

Results

We confirmed that OVA-challenged mice produced high levels of Ox40, Mbp, Ccl11, Il5, Il4, Il13, and Il6 mRNA and a low level of Ifng mRNA in the intestine. Increased eosinophils were observed in intestinal and lymph tissues, accompanied by significantly upregulated OX40 and Type 2 cytokine production in eosinophils of EGE mice. Ox40 deficiency ameliorated OVA-induced inflammation, eosinophil infiltration, and cytokine production in the intestine. Consistently, Ox40^{-/ -} eosinophils exhibited decreased proliferation and proinflammatory function. The stimulation of the agonistic anti-OX40 antibody, OX86, promoted the effect of OX40 on eosinophils. The present study also showed that Ox40 deficiency dampened the Traf2/6-related NF-κB signaling pathway in eosinophils.

Conclusions

OX40 may play a critical role in the progress of OVA-induced EGE by promoting the maturation and function of eosinophils via the Traf2/6-related NF-κB signaling pathway.

Future Prospects of Immunotherapy in Non-Small-Cell Lung Cancer Patients: Is There Hope in Other Immune Checkpoints Targeting Molecules?

Currently, one of the leading treatments for non-small-cell lung cancer is immunotherapy involving immune checkpoint inhibitors. These monoclonal antibodies restore the anti-tumour immune response altered by negative immune checkpoint interactions. The most commonly used immunotherapeutics in monotherapy are anti-PD-1 and anti-PD-L1 antibodies. The effectiveness of both groups of antibodies has been proven in many clinical trials, which have translated into positive immunotherapeutic registrations for cancer patients worldwide. These antibodies are generally well tolerated, and certain patients achieve durable responses. However, given the resistance of some patients to this form of therapy, along with its other drawbacks, such as adverse events, alternatives are constantly being sought. Specifically, new drugs targeting already known molecules are being tested, and new potential targets are being explored. The aim of this paper is to provide an overview of the latest developments in this area.

Lymph node-resident dendritic cells drive TH2 cell development involving MARCH1

Type 2 T helper (TH2) cells are protective against parasitic worm infections but also aggravate allergic inflammation. Although the role of dendritic cells (DCs) in TH2 cell differentiation is well established, the underlying mechanisms are largely unknown. Here, we show that DC induction of TH2 cells depends on membrane-associated RING-CH-1 (MARCH1) ubiquitin ligase. The pro-TH2 effect of MARCH1 relied on lymph node (LN)–resident DCs, which triggered T cell receptor (TCR) signaling and induced GATA-3 expression from naïve CD4+ T cells independent of tissue-driven migratory DCs. Mice with mutations in the ubiquitin acceptor sites of MHCII and CD86, the two substrates of MARCH1, failed to develop TH2 cells. These findings suggest that TH2 cell development depends on ubiquitin-mediated clearance of antigen-presenting and costimulatory molecules by LN-resident DCs and consequent control of TCR signaling.

Effect of E-Cigarette aerosol exposure on airway inflammation in a murine model of asthma

OBJECTIVE

The popularity of electronic cigarettes (E-Cigs) smoking is increasing worldwide including patients with asthma. In this study, the effects of E-Cigs aerosol exposure on airway inflammation in an allergen-driven murine model of asthma were investigated.

MATERIALS AND METHODS

Balb/c mice were randomly assigned to; control group (received fresh air, Ovalbumin (Ova) sensitization and saline challenge), E-Cig group (received E-Cig aerosol, Ova sensitization, and saline challenge), Ova S/C group (received fresh air, Ova sensitization and Ova challenge) and E-Cig + Ova S/C group. Bronchoalveolar lavage fluid (BALF) and lung tissue were evaluated for inflammatory cells and inflammatory mediators, respectively.

RESULTS

Exposure to E-Cig aerosol significantly increased the number of all types of inflammatory cells in BALF (p < 0.05). Further, E-Cig aerosol reduced levels of transforming growth factor (TGF)-β1 and matrix metalloproteinase (MMP)-2 in lung tissue homogenate (p < 0.05). Combined E-Cig aerosol and Ova S/C increased the airway recruitment of inflammatory cells, especially neutrophils, eosinophils, and lymphocytes (p < 0.05), increased the level of interleukin (IL)-13, and reduced the level of TGF-β1 (p < 0.05).

CONCLUSIONS

E-Cig aerosol exposure induced airway inflammation in both control mice and allergen-driven murine model of asthma. The inflammatory response induced by E-Cig was slightly higher in allergen-driven murine model of asthma than in healthy animals.

Antigen presentation by dendritic cells and their instruction of CD4+ T helper cell responses

Dendritic cells are powerful antigen-presenting cells that are essential for the priming of T cell responses. In addition to providing T-cell-receptor ligands and co-stimulatory molecules for naive T cell activation and expansion, dendritic cells are thought to also provide signals for the differentiation of CD4+ T cells into effector T cell populations. The mechanisms by which dendritic cells are able to adapt and respond to the great variety of infectious stimuli they are confronted with, and prime an appropriate CD4+ T cell response, are only partly understood. It is known that in the steady-state dendritic cells are highly heterogenous both in phenotype and transcriptional profile, and that this variability is dependent on developmental lineage, maturation stage, and the tissue environment in which dendritic cells are located. Exposure to infectious agents interfaces with this pre-existing heterogeneity by providing ligands for pattern-recognition and toll-like receptors that are variably expressed on different dendritic cell subsets, and elicit production of cytokines and chemokines to support innate cell activation and drive T cell differentiation. Here we review current information on dendritic cell biology, their heterogeneity, and the properties of different dendritic cell subsets. We then consider the signals required for the development of different types of Th immune responses, and the cellular and molecular evidence implicating different subsets of dendritic cells in providing such signals. We outline how dendritic cell subsets tailor their response according to the infectious agent, and how such transcriptional plasticity enables them to drive different types of immune responses.

Therapeutic strategies for the costimulatory molecule OX40 in T-cell-mediated immunity

The T cell co-stimulatory molecule OX40 and its cognate ligand OX40L have attracted broad research interest as a therapeutic target in T cell-mediated diseases. Accumulating preclinical evidence highlights the therapeutic efficacy of both agonist and blockade of the OX40-OX40L interaction. Despite this progress, many questions about the immuno-modulator roles of OX40 on T cell function remain unanswered. In this review we summarize the impact of the OX40-OX40L interaction on T cell subsets, including Th1, Th2, Th9, Th17, Th22, Treg, Tfh, and CD8+ T cells, to gain a comprehensive understanding of anti-OX40 mAb-based therapies. The potential therapeutic application of the OX40-OX40L interaction in autoimmunity diseases and cancer immunotherapy are further discussed; OX40-OX40L blockade may ameliorate autoantigen-specific T cell responses and reduce immune activity in autoimmunity diseases. We also explore the rationale of targeting OX40-OX40L interactions in cancer immunotherapy. Ligation of OX40 with targeted agonist anti-OX40 mAbs conveys activating signals to T cells. When combined with other therapeutic treatments, such as anti-PD-1 or anti-CTLA-4 blockade, cytokines, chemotherapy, or radiotherapy, the anti-tumor activity of agonist anti-OX40 treatment will be further enhanced. These data collectively suggest great potential for OX40-mediated therapies.

Whole blood vs PBMC: compartmental differences in gene expression profiling exemplified in asthma

Background

Blood has proven to be a useful resource for molecular analysis in numerous biomedical studies, with peripheral blood mononuclear cells (PBMCs) and whole blood being the major specimen types. However, comparative analyses between these two major compartments (PBMCs and whole blood) are few and far between. In this study, we compared gene expression profiles of PBMCs and whole blood samples obtained from research subjects with or without mild allergic asthma.

Methods

Whole blood (PAXgene) and PBMC samples were obtained from 5 mild allergic asthmatics and 5 healthy controls. RNA from both sample types was measured for expression of 730 immune-related genes using the NanoString nCounter platform.

Results

We identified 64 uniquely expressed transcripts in whole blood that reflected a variety of innate, humoral, and adaptive immune processes, and 13 uniquely expressed transcripts in PBMCs which were representative of T-cell and monocyte-mediated processes. Furthermore, analysis of mild allergic asthmatics versus non-asthmatics revealed 47 differentially expressed transcripts in whole blood compared to 1 differentially expressed transcript in PBMCs (FDR < 0.25). Finally, through simultaneous measurement of PBMC proteins on the nCounter assay, we identified CD28 and OX40 (TNFRSF4), both of which are critical co-stimulatory molecules during T-cell activation, as significantly upregulated in asthmatics.

Conclusions

Whole blood RNA preserved in PAXgene tubes is excellent for producing gene expression data with minimal variability and good sensitivity, suggesting its utility in multi-centre studies requiring measurement of blood gene expression.

Critical role of OX40/OX40L in ILC2-mediated activation of CD4+T cells during respiratory syncytial virus infection in mice

CD4⁺T cells are crucial cellular source of type 2 cytokines and responsible for RSV-induced asthma-like symptoms and asthma exacerbations. However, the mechanism for regulating the activation of CD4⁺T cells during RSV infection is not clear completely. We show in this study that infection with RSV may induce an expansion and activation of CD4⁺T cells in the lungs of BALB/c mice. RSV-induced CD4⁺T cell expansion and activation seems to depend upon the pulmonary group 2 innate lymphoid cells (ILC2s), since adoptive transfer of lung ILC2s can enhance not only the numbers of CD4⁺T cells but also the cytokine production by CD4⁺T cells. Interestingly, blockade of the contact between ILC2s and CD4⁺T cells, may significantly diminish the CD4⁺T cell expansion and cytokine production, suggesting that membrane molecules may be involved in ILC2-regulated CD4⁺T cell activation. In fact, infection with RSV resulted in an increase in the numbers of OX40⁺CD4⁺T cells as well as OX40L⁺ILC2s in the lungs of mice. Moreover, the mRNA expressions of OX40 and OX40L as well as the levels of OX40 and OX40L proteins in the lung CD4⁺T cells and ILC2s were elevated respectively. When co-culture of CD4⁺T cells with ILC2s in the presence of anti-OX40L antibody, the cytokine productions by CD4⁺T cells were reduced markedly, suggesting that lung ILC2s may regulate RSV-induced CD4⁺T cell expansion and activation perhaps via OX40/OX40L interaction.

OX40 and OX40L protein expression of tumor infiltrating lymphocytes in non-small cell lung cancer and its role in clinical outcome and relationships with other immune biomarkers

Background

Anti-tumoral immunotherapy of anti-program death-1/program death-ligand 1 (PD-1/PD-L1) immune checkpoint therapy demonstrated promising efficacy and tolerability in patients with lung cancer. Apart from inhibitory checkpoints, OX40, the co-stimulatory receptor related to T cell priming and proliferation, was valued identically. In this study, the relationship between OX40/OX40L expressed on tumor infiltrating lymphocytes (TILs), PD-1/PD-L1 and other immunological factors, as well as its role serving as the potential prognostic biomarker, were analyzed in NSCLC.

Methods

We investigated the relationship between OX40/OX40L, PD-1/PD-L1 and TILs in surgical samples from 139 patients with NSCLC by immunohistochemistry (IHC). Factors related to OX40/OX40L expression were analyzed by logistic regression and multi-linear regression. Cox analysis was also performed to find the influencing factors. Survival analysis was conducted in order to testify its role in predicting patients' prognosis.

Results

The TILs OX40, OX40L expression were negatively correlated with the PD-1/PD-L1 expression, respectively. PD-1 expression was negatively correlated with the TILs OX40 expression [R=0.250, (P=0.003)], it was also negatively correlated with the TILs OX40L expression [R=0.386, (P=0.0001)]. PD-1 expression was positively correlated with TILs grades and negatively correlated with the TILs OX40L expression in multiple linear model [R=0.531, (X1, 95% CI: 3.552-8.176, P=0.0001; X2, 95% CI: 0.216-0.683), (P=0.0001)]. The expression of TILs OX40 varied significantly among tumor OX40 and OX40L, PD-1, PD-L1, TILs and pathology types. Tumor OX40L expression, TILs OX40L expression, PD-1 expression, PD-L1 expression and TILs were considered as risk factors for TILs OX40 expression. The staging and TILs OX40L were considered as risk factors for overall survival (OS) while stage and gender were risk factors for recurrence-free survival (RFS). The low-expression of OX40 was related to longer RFS, OS and better prognosis.

Conclusions

OX40 plays a pivotal role in NSCLC, which was closely correlated with immunological factors, RFS and prognosis.

Hakemi M, Ghasemi R, Eskandari N. Correlation of OX40 ligand on B cells with serum total IgE and IL-4 levels by CD4+ T cells in allergic rhinitis

INTRODUCTION AND OBJECTIVES

Allergic rhinitis (AR) is a classic Th2-mediated disease, with important contributions to the pathology of interleukins 4, 5, and 13. The co-stimulatory molecule of OX40 and its ligand interaction participate in the immune response by regulation of Th1/Th2 cells balance. Considering the paucity of information on the relation between OX40 ligand (OX40L) and AR, this study aimed to examine its expression on B lymphocytes.

PATIENTS AND METHODS

This case-control study consisted of 20 AR patients and 20 healthy subjects. The serum level of total immunoglobulin E (IgE) was measured using the electro-chemiluminescence (ECL) technology. The percentage of B-lymphocytes expressing OX40L was assessed by flow cytometry. The amounts of IL-4 in CD4⁺ T cells culture supernatant was also measured by the enzyme-linked immunosorbent assay (ELISA).

RESULTS

OX40L expression on B lymphocytes of patients was significantly higher than the control group (44.32±19.21% vs. 2.79±2.48% respectively, p<0.001). In AR patients, OX40L expression correlated positively with the levels of serum total IgE and IL-4 produced by CD4⁺ T lymphocytes (p<0.01 - p<0.05) respectively.

CONCLUSIONS

Collectively, the findings of this work suggest that there is a relationship between the OX40L expression level on B lymphocytes and allergic markers such as IgE and IL-4 in patients with allergic rhinitis.

Intratracheal Administration of siRNA Triggers mRNA Silencing in the Lung to Modulate T Cell Immune Response and Lung Inflammation

Clinical application of siRNA-based therapeutics outside of the liver has been hindered by the inefficient delivery of siRNA effector molecules into extra-hepatic organs and cells of interest. To understand the parameters that enable RNAi activity in vivo, it is necessary to develop a systematic approach to identify which cells within a tissue are permissive to oligonucleotide internalization and activity. In the present study, we evaluate the distribution and activity within the lung of chemically stabilized siRNA to characterize cell-type tropism and structure-activity relationship. We demonstrate intratracheal delivery of fully modified siRNA for RNAi-mediated target knockdown in lung CD11c⁺ cells (dendritic cells, alveolar macrophages) and alveolar epithelial cells. Finally, we use an allergen-induced model of lung inflammation to demonstrate the capacity of inhaled siRNA to induce target knockdown in dendritic cells and ameliorate lung pathology.

STAT6 inhibitory peptide reduces dendritic cell migration to the lymph nodes to control Th2 adaptive immunity in the mouse lung

Type 2 immunity in the lung is promoted through the release of innate cytokines, including TSLP, from lung structural cells. These cytokines drive Type 2 immunity in part through upregulation of OX40L on dendritic cells (DCs). DCs expressing OX40L are potent inducers of Th2 differentiation. We have shown previously that STAT6 inhibitory peptide (STAT6-IP), a cell penetrating peptide designed to inhibit the STAT6 transcription factor, reduces the induction of Th2 adaptive immunity in murine models of respiratory syncytial virus infection. Here we show that intranasal administration of STAT6-IP at the time of antigen priming with ovalbumin (OVA), in conjunction with the Nod2 agonist, MDP, reduced frequencies of CD11b⁺ lung DCs expressing OX40L. Consistent with these reductions, fewer activated DCs were localized to the lung draining lymph nodes in STAT6-IP-treated mice. Upon OVA challenge four weeks later, mice treated with STAT6-IP at the time of OVA/MDP priming did not develop airway hyperresponsiveness (AHR) and had reduced influx of eosinophils into the airways, mucus production, and serum OVA-specific IgE levels. Our findings provide evidence that the long-lasting inhibitory effects of STAT6-IP are due in part to inhibition of DC responses that drive maladaptive Th2 adaptive immunity and allergic airways disease.

Tissue-Restricted Adaptive Type 2 Immunity Is Orchestrated by Expression of the Costimulatory Molecule OX40L on Group 2 Innate Lymphoid Cells

The local regulation of type 2 immunity relies on dialog between the epithelium and the innate and adaptive immune cells. Here we found that alarmin-induced expression of the co-stimulatory molecule OX40L on group 2 innate lymphoid cells (ILC2s) provided tissue-restricted T cell co-stimulation that was indispensable for Th2 and regulatory T (Treg) cell responses in the lung and adipose tissue. Interleukin (IL)-33 administration resulted in organ-specific surface expression of OX40L on ILC2s and the concomitant expansion of Th2 and Treg cells, which was abolished upon deletion of OX40L on ILC2s (Il7raCre/+Tnfsf4fl/fl mice). Moreover, Il7raCre/+Tnfsf4fl/fl mice failed to mount effective Th2 and Treg cell responses and corresponding adaptive type 2 pulmonary inflammation arising from Nippostrongylus brasiliensis infection or allergen exposure. Thus, the increased expression of OX40L in response to IL-33 acts as a licensing signal in the orchestration of tissue-specific adaptive type 2 immunity, without which this response fails to establish.

Dectin-1/2-induced autocrine PGE2 signaling licenses dendritic cells to prime Th2 responses

The molecular mechanisms through which dendritic cells (DCs) prime T helper 2 (Th2) responses, including those elicited by parasitic helminths, remain incompletely understood. Here, we report that soluble egg antigen (SEA) from Schistosoma mansoni, which is well known to drive potent Th2 responses, triggers DCs to produce prostaglandin E2 (PGE₂), which subsequently—in an autocrine manner—induces OX40 ligand (OX40L) expression to license these DCs to drive Th2 responses. Mechanistically, SEA was found to promote PGE₂ synthesis through Dectin-1 and Dectin-2, and via a downstream signaling cascade involving spleen tyrosine kinase (Syk), extracellular signal-regulated kinase (ERK), cytosolic phospholipase A₂ (cPLA₂), and cyclooxygenase 1 and 2 (COX-1 and COX-2). In addition, this pathway was activated independently of the actions of omega-1 (ω-1), a previously described Th2-priming glycoprotein present in SEA. These findings were supported by in vivo murine data showing that ω-1–independent Th2 priming by SEA was mediated by Dectin-2 and Syk signaling in DCs. Finally, we found that Dectin-2^−/−, and to a lesser extent Dectin-1^−/− mice, displayed impaired Th2 responses and reduced egg-driven granuloma formation following S. mansoni infection, highlighting the physiological importance of this pathway in Th2 polarization during a helminth infection. In summary, we identified a novel pathway in DCs involving Dectin-1/2-Syk-PGE₂-OX40L through which Th2 immune responses are induced.

T helper 2 (Th2) responses, which are initiated by dendritic cells (DCs), can cause allergic diseases, but they can also provide protection against metabolic disorders and parasitic helminth infections. As such, there is great interest in better understanding how their activity is induced and regulated by DCs. Parasitic helminths can potently induce Th2 responses. However, how helminths condition DCs for priming of Th2 responses remains incompletely understood. Here, we find that egg antigens from the parasitic helminth Schistosoma mansoni bind to pattern-recognition receptors (PRRs) Dectin-1 and Dectin-2 on DCs. This binding triggers a signaling cascade in DCs that results in synthesis of eicosanoid prostaglandin E2 (PGE₂). PGE₂ is sensed by the DCs themselves, resulting in expression of OX40 ligand (OX40L), which subsequently enables the DCs to promote Th2 differentiation. We show that this pathway is activated independently of omega-1 (ω-1), which is a glycoprotein secreted by the eggs and previously shown to condition DCs for priming of Th2 responses. Moreover, we demonstrate that this ω-1–independent pathway is crucial for Th2 induction and egg-driven immunopathology following S. mansoni infection in vivo. In summary, we identified a novel pathway in DCs involving Dectin-1/2–induced autocrine PGE₂ signaling through which Th2 responses are induced.

Type 2 cytokine responses: regulating immunity to helminth parasites and allergic inflammation

Purpose of Review

It is well established that T helper type 2 (T_H2) immune responses are necessary to provide protection against helminth parasites but also to promote the detrimental inflammation associated with allergies and asthma. Given the importance of type 2 immunity and inflammation, many studies have focused on better understanding the factors that regulate T_H2 cell development and activation. As a result, significant progress has been made in understanding the signaling pathways and molecular events necessary to promote T_H2 cell polarization. In addition to the adaptive compartment, emerging studies are better defining the innate immune pathways needed to promote T_H2 cell responses. Given the recent and substantial growth of this field, the purpose of this review is to highlight recent studies defining the innate immune events that promote immunity to helminth parasites and allergic inflammation.

Recent Findings

Emerging studies have begun to elucidate the importance of cytokine alarmins such as thymic stromal lymphopoietin (TSLP), IL-25 (IL-17E) and IL-33 in promoting type 2 immunity and inflammation following helminth challenge or exposure to allergens. Specifically, recent reports have begun to define the complex cellular networks these alarmins activate and their contribution to type 2 immunity and inflammation.

Summary

Our increased understanding of the pathways that regulate type 2 cytokine-mediated immunity and inflammation have revealed novel therapeutic targets to treat both helminth infections and allergic disease states.

PKC-ѳ is dispensable for OX40L-induced TCR-independent Treg proliferation but contributes by enabling IL-2 production from effector T-cells

We have previously shown that OX40L/OX40 interaction is critical for TCR-independent selective proliferation of Foxp3⁺ Tregs, but not Foxp3^- effector T-cells (Teff), when CD4⁺ T-cells are co-cultured with GM-CSF derived bone marrow dendritic cells (G-BMDCs). Events downstream of OX40L/OX40 interaction in Tregs responsible for this novel mechanism are not understood. Earlier, OX40L/OX40 interaction has been shown to stimulate CD4⁺ T-cells through the formation of a signalosome involving TRAF2/PKC-Ѳ leading to NF-kB activation. In this study, using CD4⁺ T-cells from WT and OX40^-/- mice we first established that OX40 mediated activation of NF-kB was critical for this Treg proliferation. Although CD4⁺ T-cells from PKC-Ѳ^-/- mice were also defective in G-BMDC induced Treg proliferation ex vivo, this defect could be readily corrected by adding exogenous IL-2 to the co-cultures. Furthermore, by treating WT, OX40^-/-, and PKC-Ѳ^-/- mice with soluble OX40L we established that OX40L/OX40 interaction was required and sufficient to induce Treg proliferation in vivo independent of PKC-Ѳ status. Although PKC-Ѳ is dispensable for TCR-independent Treg proliferation per se, it is essential for optimum IL-2 production by Teff cells. Finally, our findings suggest that OX40L binding to OX40 likely results in recruitment of TRAF1 for downstream signalling.

OX40: Structure and function - What questions remain?

OX40 is a type 1 transmembrane glycoprotein, reported nearly 30 years ago as a cell surface antigen expressed on activated T cells. Since its discovery, it has been validated as a bone fide costimulatory molecule for T cells and member of the TNF receptor family. However, many questions still remain relating to its function on different T cell sub-sets and with recent interest in its utility as a target for antibody-mediated immunotherapy, there is a growing need to gain a better understanding of its biology. Here, we review the expression pattern of OX40 and its ligand, discuss the structure of the receptor:ligand interaction, the downstream signalling it can elicit, its function on different T cell subsets and how antibodies might engage with it to provide effective immunotherapy.

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.

Transcription Factor KLF2 in Dendritic Cells Downregulates Th2 Programming via the HIF-1α/Jagged2/Notch Axis

The adaptive immune response is tightly regulated by complex signals in dendritic cells (DCs). Although Th2 polarization is dictated by defined functional DC subsets, the molecular factors that govern the amplitude of these responses are not well understood. Krüppel-like factor 2 (KLF2) is a transcription factor that negatively regulates the activation of numerous immune cells in response to stimuli. Here, we demonstrate that suppression of KLF2 in conditioned DCs preferentially amplifies Th2 responses in two model systems, one of which is a prototypical intracellular pathogen and the other an allergen. This elevation in Th2 responses was dependent on contact-mediated Notch signaling in vitro and in vivo. A deficiency of KLF2 increased the expression of Notch ligand Jagged2 via hypoxia-inducible factor 1α (HIF-1α), which led to Th2 amplification. Our results revealed a novel circuit in DCs for Th2 polarization that is governed by KLF2.

Dendritic cells are the key element that bridges innate and adaptive immunity. A complex and not-well-understood area in dendritic cell biology is the regulatory network that predetermines or moderates their function to shape the adaptive immune response. Our study for the first time demonstrates that KLF2, a transcription factor, conditions dendritic cells to regulate Th2 responses via a Jagged2/Notch axis. Downregulation of KLF2 expression in dendritic cells may provide a beneficial effect for treatment of diseases such as obesity or parasitic infections but may be deleterious in the case of invasion by intracellular pathogens. Strategies to tune KLF2 may be useful for future therapeutic approaches to particular diseases of mankind.

Age-dependent divergent effects of OX40L treatment on the development of diabetes in NOD mice

Earlier, we have shown that GM-CSF derived bone marrow (BM) dendritic cells (G-BMDCs) can expand Foxp3(+) regulatory T-cells (Tregs) through a TCR-independent, but IL-2 dependent mechanism that required OX40L/OX40 interaction. While some reports have shown suppression of autoimmunity upon treatment with an OX40 agonist, others have shown exacerbation of autoimmune disease instead. To better understand the basis for these differing outcomes, we compared the effects of OX40L treatment in 6-week-old pre-diabetic and 12-week-old near diabetic NOD mice. Upon treatment with OX40L, 6-week-old NOD mice remained normoglycemic and showed a significant increase in Tregs in their spleen and lymph nodes, while 12-week-old NOD mice very rapidly developed hyperglycemia and failed to show Treg increase in spleen or LN. Interestingly, OX40L treatment increased Tregs in the thymus of both age groups. However, it induced Foxp3(+)CD103(+)CD38(-) stable-phenotype Tregs in the thymus and reduced the frequency of autoreactive Teff cells in 6-week-old mice; while it induced Foxp3(+)CD103(-)CD38(+) labile-phenotype Tregs in the thymus and increased autoreactive CD4(+) T cells in the periphery of 12-week-old mice. This increase in autoreactive CD4(+) T cells was likely due to either a poor suppressive function or conversion of labile Tregs into Teff cells. Using ex vivo cultures, we found that the reduction in Treg numbers in 12-week-old mice was likely due to IL-2 deficit, and their numbers could be increased upon addition of exogenous IL-2. The observed divergent effects of OX40L treatment were likely due to differences in the ability of 6- and 12-week-old NOD mice to produce IL-2.

Genetic risk of TNFSF4 and FAM167A-BLK polymorphisms in children with asthma and allergic rhinitis in a Han Chinese population

BACKGROUND

Asthma and allergic rhinitis (AR) frequently occur as comorbid diseases of the upper airways. Single-nucleotide polymorphisms (SNPs) in the TNFSF4 and FAM167A-BLK genes have recently been shown to be associated with various immune-related disorders.

OBJECTIVE

Our aim was to determine whether TNFSF4 or FAM167A-BLK polymorphisms confer genetic susceptibility to asthma and AR in a Han Chinese population.

METHODS

We performed a case-control study of 290 asthmatic children and 252 healthy controls. Nine SNPs in the TNFSF4 region (rs1234313, rs1234314, rs1234315, rsl 2039904, rs844648 and rsl 0912580) and the FAM167A-BLK region (rs2254546, rs13277113 and rs1600249) were detected using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay.

RESULTS

This study revealed that three SNPs in TNFSF4 (rsl 234313, rsl 234314 and rsl 234315) and two SNPs in FAM167A-BLK (rs2254546 and rsl 600249) were significantly correlated with asthma and AR, while SNP rsl600249 was associated with asthma without allergic rhinitis as a risk factor. Further, we demonstrated synergistic effects between the TNFSF4 and FAM167A-BLK SNPs.

CONCLUSION

This study supports that the SNPs in TNFSF4 and FAM167A-BLK may be involved in asthma and AR gene risk in the Han Chinese cohort.

Anti-OX40L alone or in combination with anti-CD40L and CTLA4Ig does not inhibit the humoral and cellular response to a major grass pollen allergen

BACKGROUND

IgE-mediated allergy is a common disease characterized by a harmful immune response towards otherwise harmless environmental antigens. Induction of specific immunological non-responsiveness towards allergens would be a desirable goal. Blockade of costimulatory pathways is a promising strategy to modulate the immune response in an antigen-specific manner. Recently, OX40 (CD134) was identified as a costimulatory receptor important in Th2-mediated immune responses. Moreover, synergy between OX40 blockade and 'conventional' costimulation blockade (anti-CD40L, CTLA4Ig) was observed in models of alloimmunity.

OBJECTIVE

We investigated the potential of interfering with OX40 alone or in combination with CD40/CD28 signals to influence the allergic immune response.

METHODS

The OX40 pathway was investigated in an established murine model of IgE-mediated allergy where BALB/c mice are repeatedly immunized with the clinically relevant grass pollen allergen Phl p 5. Groups were treated with combinations of anti-OX40L, CTLA4Ig and anti-CD40L. In selected mice, Tregs were depleted with anti-CD25.

RESULTS

Blockade of OX40L alone at the time of first or second immunization did not modulate the allergic response on the humoral or effector cell levels but slightly on T cell responses. Administration of a combination of anti-CD40L/CTLA4Ig delayed the allergic immune response, but antibody production could not be inhibited after repeated immunization even though the allergen-specific T cell response was suppressed in the long run. Notably, additional blockade of OX40L had no detectable supplementary effect. Immunomodulation partly involved regulatory T cells as depletion of CD25(+) cells led to restored T cell proliferation.

CONCLUSIONS AND CLINICAL RELEVANCE

Collectively, our data provide evidence that the allergic immune response towards Phl p 5 is independent of OX40L, although reduction on T cell responses and slightly on the asthmatic phenotype was detectable. Besides, no relevant synergistic effect of OX40L blockade in addition to CD40L/CD28 blockade could be detected. Thus, the therapeutic potential of OX40L blockade for IgE-mediated allergy appears to be ineffective in this setting.

Regulation of Th1/Th2 balance through OX40/OX40L signalling by glycyrrhizic acid in a murine model of asthma

BACKGROUND AND OBJECTIVE

Glycyrrhizic acid (GA) has been reported to have attenuating airway inflammation effects in asthma mouse model. However, the potential molecular mechanisms by which GA exerts anti-inflammatory effects on ovalbumin (OVA)-induced allergic asthma have not been well elaborated.

METHODS

The effect of GA on OVA-sensitized and challenged mice was investigated. The effect of GA on anti-OX40 mAb stimulated splenocytes from asthma mice model was also examined.

RESULTS

In OVA-induced asthmatic mice, GA treatment prevented the decrease of T helper1 cytokine (interferon (IFN)-γ) and the increase of T helper2 cytokines (interleukin (IL)-4, IL-5, IL-13) in bronchoalveolar lavage fluid (BALF), reduced serum immunoglobulin (Ig)E and OVA-specific IgE levels, prohibited the protein and mRNA expression of OX40 and OX40 Ligand (OX40L) in lung tissues, and the expression of OX40 in CD4(+) T cells and OX40L in CD11b(+) monocytes and CD19(+) B cells in spleens in a dose-dependent manner compared with the vehicle treatment (all P < 0.05). Moreover, OVA significantly increased the activation of p38 mitogen-activated protein kinase (MAPK) in lung tissues, whereas GA and anti-OX40L mAb markedly reduced phosphorylation of p38 MAPK. In addition, GA could inhibit the T cell proliferation and modulate the balance of Th1/Th2 in anti-OX40 mAb stimulated CD4(+) T cells from asthmatic spleens (all P < 0.05).

CONCLUSIONS

GA may exert a therapeutic effect on OVA-induced experimental asthma partly by regulating the Th1/Th2 balance through suppressing OX40-OX40L signalling and p38 MAPK activity. GA may be a promising treatment for asthma.

Basophil-associated OX40 ligand participates in the initiation of Th2 responses during airway inflammation

Asthma is characterized by increased airway submucosal infiltration of T helper (Th) cells and myeloid cells that co-conspire to sustain a chronic inflammation. While recent studies have demonstrated that the myeloid basophils promote Th2 cells in response to various types of allergens, the underlying mechanisms are poorly understood. Here, we found for the first time that in a mouse model of allergic asthma basophils highly expressed OX40 ligand (OX40L) after activation. Interestingly, blockade of OX40-OX40L interaction suppressed basophils-primed Th2 cell differentiation in vitro and ameliorated ovalbumin (OVA)-induced allergic eosinophilic inflammation mediated by Th2 activation. In accordance, the adoptive transfer of basophils derived from mediastinal lymph nodes (MLN) of OVA-immunized mice triggered a robust Th2 response and eosinophilic inflammation in wild-type mice but largely muted in OX40(-/-) mice and mice receiving OX40L-blocked basophils. Taken together, our results reveal a critical role of OX40L presented by the activated basophils to initiate Th2 responses in an allergic asthma model, implicating OX40-OX40L signaling as a potential therapeutic target in the treatment of allergic airway inflammation.

Airway epithelium interactions with aeroallergens: role of secreted cytokines and chemokines in innate immunity

Airway epithelial cells are the first line of defense against the constituents of the inhaled air, which include allergens, pathogens, pollutants, and toxic compounds. The epithelium not only prevents the penetration of these foreign substances into the interstitium, but also senses their presence and informs the organism’s immune system of the impending assault. The epithelium accomplishes the latter through the release of inflammatory cytokines and chemokines that recruit and activate innate immune cells at the site of assault. These epithelial responses aim to eliminate the inhaled foreign substances and minimize their detrimental effects to the organism. Quite frequently, however, the innate immune responses of the epithelium to inhaled substances lead to chronic and high level release of pro-inflammatory mediators that may mediate the lung pathology seen in asthma. The interactions of airway epithelial cells with allergens will be discussed with particular focus on interactions-mediated epithelial release of cytokines and chemokines and their role in the immune response. As pollutants are other major constituents of inhaled air, we will also discuss how pollutants may alter the responses of airway epithelial cells to allergens.

IgE and IgA produced by OX40-OX40L or CD40-CD40L interaction in B cells-mast cells re-activate FcεRI or FcαRI on mast cells in mouse allergic asthma

Mast cells are major effector cells of allergic diseases related to IgE. This study was undertaken to determine whether IgE or IgA, produced by CD40-CD40L or OX40-OX40L interactions between B cells and mast cells, re-activate FcεRI or FcαRI on mast cell surface. C57BL mice were sensitized and subjected to OVA challenge to induce asthma. Bone marrow-derived mast cells (BMMCs) and primary B cells were co-cultured. Mast cell recruitment into airways was stained by May-Grünwald Giemsa, the expression of markers or signaling molecules were determined by immunohistochemistry or Western blotting, and co-localization of B cells and mast cells by immunofluorescence. Anti-CD40 plus anti-OX40L Abs synergistically reduced IgE and IgA production, and mediators (histamine, LTs and cytokines) released in mast cells, and additively reduced other responses, such as, numbers of mast cells, the expression of markers (tryptase, mMCP5, B220 and CD19), surface molecules (CD40, CD40L, OX40 and OX40L), FcεRI or FcαRI and the co-localization of BMMCs and B cells, and IgE- or IgA-producing cells, as compared with individual blocking Ab treatment which reducedresponses in BAL cells or lung tissues of OVA-challenged mice or in co-culture of B and mast cells. The data suggest that IgE and IgA, produced by OX40-OX40L or CD40-CD40L interaction between B cells and mast cells, may re-activate receptors of FCεRI and FcαRI on mast cell surfaces, followed by more mediator release, and furthermore, that treatment with anti-CD40 plus anti-OX40L Abs offers a potential treatment for allergic asthma.

OX40 blockade inhibits house dust mite driven allergic lung inflammation in mice and in vitro allergic responses in humans

The costimulatory receptor OX40 is expressed on activated T cells and regulates T-cell responses. Here, we show the efficacy and mechanism of action of an OX40 blocking antibody using the chronic house dust mite (HDM) mouse model of lung inflammation and in vitro HDM stimulation of cells from HDM allergic human donors. We have demonstrated that OX40 blockade leads to a reduction in the number of eosinophils and neutrophils in the lavage fluid and lung tissue of HDM sensitized mice. This was accompanied by a decrease in activated and memory CD4(+) T cells in the lungs and further analysis revealed that both the Th2 and Th17 populations were inhibited. Improved lung function and decreased HDM-specific antibody responses were also noted. Significantly, efficacy was observed even when anti-OX40 treatment was delayed until after inflammation was established. OX40 blockade also inhibited the release of the Th2 cytokines IL-5 and IL-13 from cells isolated from HDM allergic human donors. Altogether, our data provide evidence of a role of the OX40/OX40L pathway in ongoing allergic lung inflammation and support clinical studies of a blocking OX40 antibody in Th2 high severe asthma patients.

Novel treatments of asthma and allergic diseases

The prevalence of allergic diseases has considerably increased, mostly in industrialized countries (> 20%), and asthma affects approximately 300 million individuals worldwide. Current therapies are able to control symptoms although they do not modulate immunological dysregulation that characterizes allergic diseases. Over the last 30 years, only a few new drugs have been introduced on the market and they all act on Th2-type response which has a critical role in the pathogenesis of allergic diseases. Recently, a new scenario has been opened on Th17-cells, Th1-type cytokines and innate immune system components involved in the inflammatory pathogenesis of asthma and other allergic diseases. These findings suggest a promising therapeutic role of new agents that block the action of specific cytokines. Furthermore, the concept of an intrinsic structural defect in the bronchial epithelium paves the way to innovative therapeutic strategies. In this review we present an update on therapies for allergic diseases with special focus on asthma.

OX40L blockade and allergen-induced airway responses in subjects with mild asthma

Background

The OX40/OX40L interaction contributes to an optimal T cell response following allergic stimuli and plays an important role in the maintenance and reactivation of memory T effector cells.

Objective

We tested whether treatment with an anti-OX40L monoclonal antibody (MAb) would inhibit allergen-induced responses in subjects with asthma.

Methods

Twenty-eight mild, atopic asthmatic subjects were recruited for a double-blind, randomized, placebo-controlled, parallel-group trial (ClinicalTrials.gov identifier NCT00983658) to compare blockade of OX40L using a humanized anti-OX40L MAb to placebo-administered intravenously in 4 doses over 3 months. Allergen inhalation challenges were carried out 56 and 113 days after the first dose of study drug. The primary outcome variable was the late-phase asthmatic response. Other outcomes included the early-phase asthmatic response, airway hyperresponsiveness, serum IgE levels, blood and sputum eosinophils, safety and tolerability.

Results

Treatment with anti-OX40L MAb did not attenuate the early- or late-phase asthmatic responses at days 56 or 113 compared with placebo. In the anti-OX40L MAb treatment group, total IgE was reduced 17% from pre-dosing levels, and sputum eosinophils decreased 75% by day 113 (both P = 0.04). There was no effect of anti-OX40L MAb on airway hyperresponsiveness or blood eosinophils. The frequency of AEs was similar in both groups.

Conclusion and Clinical Relevance

Pharmacological activity of anti-OX40L MAb was observed by decreases in serum total IgE and airway eosinophils at 16 weeks post-dosing, but there was no effect on allergen-induced airway responses. It is possible that the treatment duration or dose of antibody was insufficient to impact the airway responses.

Helminth-conditioned dendritic cells prime CD4+ T cells to IL-4 production in vivo

Dendritic cells (DC) are critical for the initiation of immune responses; however, their role in priming IL-4-producing Th2 cells in vivo is not fully understood. We used a model of intradermal injection with fluorescent-labeled, nonviable larvae from the helminth parasite nonviable Nippostrongylus brasiliensis L3 larvae (Nb), a strong inducer of Th2 responses, together with IL-4-GFP reporter mice that enable a sensitive detection of IL-4 production to examine the contribution of DC to the priming of IL-4-producing CD4(+) T cells in vivo. We found that parasite material is taken up by two distinct DC populations in draining lymph nodes: a mostly CD11c(int)MHC class II (MHCII)(hi)CD11b(+)Ly6C(-) dermal DC population and a CD11c(hi)MHCII(int)CD11b(+)Ly6C(+) monocyte-derived DC population. After Nb treatment, these two DC populations appeared in the draining lymph nodes in comparable numbers and with similar kinetics; however, treatment with pertussis toxin blocked the migration of dermal DC and the priming of IL-4-producing T cells, but only partially affected monocyte-derived DC numbers. In line with this observation, transfer of OVA-loaded CD11c(int)MHCII(hi) DC from Nb-treated mice into naive hosts could sensitize OVA-specific CD4(+) T cells to IL-4 production, whereas transfer of CD11c(int)MHCII(hi) DC from naive mice, or CD11c(hi)MHCII(int) DC from Nb-treated or naive mice, induced CD4(+) T cell expansion but no IL-4 production. Phenotypic analysis of Nb-loaded CD11c(int)MHCII(hi) DC revealed expression of programmed death ligand 2, CD301b, IFN regulatory factor 4, and moderate upregulation of OX40 ligand. However, thymic stromal lymphopoietin and OX40 ligand were not required for Th2 priming. Thus, our data suggest that appropriate stimuli can induce DC to express the unique signals sufficient to direct CD4(+) T cells to Th2 differentiation.

Proteinase-activated receptor-2 activation participates in allergic sensitization to house dust mite allergens in a murine model

BACKGROUND

Many aeroallergens contain proteinase activity and are able to induce allergic sensitization when presented to mucosal surfaces. Some of these allergens activate proteinase-activated receptor-2 (PAR2 ).

OBJECTIVE

To determine the role of PAR2 activation in a murine house dust mite (HDM) allergy model.

METHODS

We sensitized and challenged PAR2 -deficient mice with HDM, and examined allergic outcomes compared to wild-type animals. To focus on the role of PAR2 in allergic sensitization, we administered a PAR2 blocking antibody to wild-type animals during the sensitization phase and examined the outcomes immediately after sensitization or following subsequent allergen challenge.

RESULTS

We found PAR2 -deficient mice sensitized and challenged with HDM failed to develop airway inflammation, did not produce HDM-specific IgG1 and had less IL-4 mRNA in the lungs than wild-type animals. Prevention of PAR2 activation during sensitization in wild-type mice diminished the levels of Th2 mediators, including IL-4, IL-5 and IL-13, in the lungs. Blocking PAR2 during the sensitization phase also led to decreased manifestations of allergic disease, including airway hyperresponsiveness (AHR) and airway inflammation following subsequent allergen challenge. HDM-induced proliferation of splenocytes obtained from animals sensitized in the presence of PAR2 antibody was reduced relative to those that did not receive antibody. The effect of PAR2 blockade could be transferred to naïve mice through splenic CD4(+) T cells from sensitized mice.

CONCLUSIONS AND CLINICAL RELEVANCE

PAR2 activation plays a key role during the sensitization phase of our HDM allergy model, leading to increased lung cytokine production and augmented lung reactivity. PAR2 activation is a common mechanism for sensitization to a wide variety of allergens and is therefore a potential pharmacological target to prevent allergy.

OX40 ligand: a potential costimulatory molecule in atopic asthma

OBJECTIVE

We aimed to assess the percentage of peripheral blood B-lymphocytes expressing OX40 ligand (OX40L) in adult atopic and non-atopic asthmatic patients, and in healthy controls.

METHODS

This case-control study included 15 atopic asthmatic patients, 15 non-atopic asthmatic patients, and 15 healthy controls. Atopic status was determined by skin prick test reaction to the most common locally-encountered allergens. For all subjects, pulmonary function tests and measurement of total serum immunoglobulin E (IgE) levels by ELISA were performed. In addition, the percentage of B-lymphocytes expressing OX40L was assessed by flow cytometry in all three groups.

RESULTS

OX40L expression was significantly higher in atopic asthmatics than in non-atopic asthmatics and controls, but did not differ significantly between non-atopic asthmatics or controls. Among atopic asthmatics, OX40L expression correlated positively with total serum IgE levels, but not with age, disease duration, or values of forced expiratory volume in the first second.

CONCLUSION

The over-expression of OX40L in atopic asthmatic patients appears to be linked to markers of the atopic status as total serum IgE, and signifies the vital role of OX40L in the atopic mechanism. Further large-scale studies are needed to investigate the role of OX40L in other atopic diseases and its relation to disease activity and severity.

PD-L2 modulates asthma severity by directly decreasing dendritic cell IL-12 production

Studies examining the role of programmed death 1 (PD-1) ligand 2 (PD-L2)/PD-1 in asthma have yielded conflicting results. To clarify its role, we examined the PD-L2 expression in biopsies from human asthmatics and the lungs of aeroallergen-treated mice. PD-L2 expression in bronchial biopsies correlated with the severity of asthma. In mice, allergen exposure increased PD-L2 expression on pulmonary myeloid dendritic cells (DCs), and PD-L2 blockade diminished allergen-induced airway hyperresponsiveness (AHR). By contrast, PD-1 blockade had no impact, suggesting that PD-L2 promotes AHR in a PD-1-independent manner. Decreased AHR was associated with enhanced serum interleukin (IL)-12 p40, and in vitro stimulation of DCs with allergen and PD-L2-Fc reduced IL-12 p70 production, suggesting that PD-L2 inhibits allergen-driven IL-12 production. In our model, IL-12 did not diminish T helper type 2 responses but rather directly antagonized IL-13-inducible gene expression, highlighting a novel role for IL-12 in regulation of IL-13 signaling. Thus, allergen-driven enhancement of PD-L2 signaling through a PD-1-independent mechanism limits IL-12 secretion, exacerbating AHR.

Vitamin D regulation of OX40 ligand in immune responses to Aspergillus fumigatus

OX40 ligand (OX40L) is a costimulatory molecule involved in Th2 allergic responses. It has been shown that vitamin D deficiency is associated with increased OX40L expression in peripheral CD11c(+) cells and controls Th2 responses to Aspergillus fumigatus in vitro in cystic fibrosis (CF) patients with allergic bronchopulmonary aspergillosis (ABPA). To investigate if vitamin D deficiency regulated OX40L and Th2 responses in vivo, we examined the effect of nutritional vitamin D deficiency on costimulatory molecules in CD11c(+) cells and A. fumigatus-induced Th2 responses. Vitamin D-deficient mice showed increased expression of OX40L on lung CD11c(+) cells, and OX40L was critical for enhanced Th2 responses to A. fumigatus in vivo. In in vitro assays, vitamin D treatment led to vitamin D receptor (VDR) binding in the promoter region of OX40L and significantly decreased the promoter activity of the OX40L promoter. In addition, vitamin D altered NF-κB p50 binding in the OX40L promoter that may be responsible for repression of OX40L expression. These data show that vitamin D can act directly on OX40L, which impacts Th2 responses and supports the therapeutic use of vitamin D in diseases regulated by OX40L.

OX40 ligand expression abrogates the immunosuppressive function of retinal pigment epithelium

Background

This study aims to investigate the role of OX40 ligand (OX40L) in ocular inflammation via abrogation of retinal pigment epithelium (RPE)-mediated immunosuppression using an in vitro expression approach. OX40L cDNA was polymerase chain reaction-amplified and cloned into an eYFP fusion vector. Cultured retinal pigment epithelial cells (ARPE-19) were transfected with the vector. Total RNA from unstimulated or inflammatory cytokine-stimulated ARPE cells were isolated and analyzed for OX40L expression by reverse transcription-polymerase chain reaction. Peripheral blood mononuclear cells (PBMCs) were isolated from healthy human donors. Human ARPE cells (±OX40L ± GITR ligand (GITRL) expression) and PBMCs were co-cultured for in vitro proliferation studies.

Results

Polymerase chain reaction confirmed the insertion of the OX40L gene into the fusion vector. Flow cytometry and fluorescence microscopy further confirmed surface expression of OX40L on ARPE cells after transfection. OX40L expression was induced in the RPE cells stimulated with pro-inflammatory cytokines. In the co-culture studies, there was a significant reversal (20% to 30%) of the RPE-induced suppression of activated PBMCs when the ARPE cells were transfected with OX40L. When both OX40L and GITRL were concomitantly transfected into ARPE cells, there was an additive reversal of RPE-mediated T cell suppression, when compared to the reversal caused by RPE cells expressing either OX40L alone or GITRL alone.

Conclusions

Using an in vitro approach, we found that OX40L causes an abrogation of the RPE-mediated immunosuppression. OX40L appears to be regulated in the ARPE-19 cell line and may play an important role in the pathogenesis of various ocular inflammatory conditions.

Disabling inflammatory pathways with biologics and resulting clinical outcomes in severe asthma

INTRODUCTION

Patients with severe asthma have a significant unmet need with persistent symptoms and/or frequent exacerbations despite high intensity treatment. These severe unrelenting symptoms have a huge impact on heathcare resources due to frequent hospital admissions and requirement for intensive and expensive medications. There is a compelling need for more effective and safer therapies to help severe asthma sufferers to achieve adequate control of their disease.

AREAS COVERED

Expanding knowledge of innate and adaptive immune responses has led to development of new biologic approaches for severe asthma. Here, the authors will review the existing efficacy and safety data from clinical trials of some of the new biologic therapies that are in development for severe asthma. Their specific role in distinctively targeted subpopulations of severe asthmatics will be also discussed.

EXPERT OPINION

Defining and phenotyping severe asthma patients will become increasingly important as some patients who were previously classified as having severe asthma may become well-controlled with a targeted phenotype-specific treatment. However, pharmacoeconomic concerns should also be taken into account given the elevated acquisition costs of recombinant human monoclonals and of the diagnostic screening procedures for the identification of potential responders.

Monoclonal antibodies for asthma and chronic obstructive pulmonary disease

INTRODUCTION

In asthma and chronic obstructive pulmonary disease (COPD), the inflammation in the airways cannot always be controlled with conventional therapies, such as inhaled corticosteroids. Addition of more specific anti-inflammatory therapies, such as monoclonal antibodies, against inflammation pathways might improve the disease outcome.

AREAS COVERED

This review individually discusses the major inflammation pathways and their potential blocking monoclonal antibodies in asthma and COPD.

EXPERT OPINION

The current use of omalizumab in asthma provides a good example on the potential therapeutic role of monoclonal antibodies in both asthma and COPD. There are many other monoclonal antibodies which are currently investigated as possible therapies in these diseases. The identification of the disease subsets in which such antibodies might exert the maximum benefit opens the door for personalized medicine and for targeted biological therapy in asthma and COPD.

Effect of mite allergen immunotherapy on the altered phenotype of dendritic cells in allergic asthmatic children

BACKGROUND

Allergic asthma is a T(H)2 inflammatory disease. Dendritic cells (DCs) play key roles in the T(H)1/T(H)2 balance. Allergen specific immunotherapy (SIT) has the potential to modify the course of allergy because the ratio of T(H)1 to T(H)2 cytokines produced is increased after SIT.

OBJECTIVE

To determine how SIT affects DCs in children and to define novel parameters of this treatment.

METHODS

We investigated the changes of phenotypic and functional variations of monocyte-derived DCs from allergic asthmatic children undergoing complete mite SIT. Peripheral blood monocytes from SIT allergic asthmatic children, allergic asthmatic controls, and healthy controls were cultured with granulocyte-macrophage colony-stimulating factor and interleukin 4 and then stimulated with Dermatophagoides pteronyssinus (Der p) allergen or lipopolysaccharide (LPS). The expressions of surface molecules on monocyte-derived DCs were assessed by flow cytometry. Cytokine production by cultured monocyte-derived DCs was determined by enzyme-linked immunosorbent assay.

RESULTS

After LPS stimulation, monocyte-derived DCs of the allergic asthmatic group had a higher CD86 and lower HLA-DR expression than the healthy controls. In SIT patients, the expression was similar to that of the healthy controls. After Der p stimulation monocyte-derived DCs of the allergic asthmatic patients displayed lower Toll-like receptor 4 (TLR4), whereas again in SIT patients the expression was similar to that of healthy controls.

CONCLUSION

These findings indicate that SIT normalizes the expression of CD86, HLA-DR, and TLR4 on DCs. Moreover, CD86, HLA-DR, and TLR4 may be useful parameters for monitoring SIT. Decreased TLR4 expression in allergic asthmatic patients might be compensated by TLR4 agonists, with the potential of amplifying the effects of SIT.

Responsiveness to respiratory syncytial virus in neonates is mediated through thymic stromal lymphopoietin and OX40 ligand

BACKGROUND

Recent studies revealed a critical role for thymic stromal lymphopoietin (TSLP) released from epithelial cells and OX40 ligand (OX40L) expressed on dendritic cells (DCs) in T(H)2 priming and polarization.

OBJECTIVES

We sought to determine the importance of the TSLP-OX40L axis in neonatal respiratory syncytial virus (RSV) infection.

METHODS

Mice were initially infected with RSV as neonates or adults and reinfected 5 weeks later. Anti-OX40L or anti-TSLP were administered during primary or secondary infection. Outcomes included assessment of airway function and inflammation and expression of OX40L, TSLP, and IL-12.

RESULTS

OX40L was expressed mainly on CD11c(+)MHC class II (MHCII)(+)CD11b(+) DCs but not CD103(+) DCs. Treatment of neonates with OX40L antibody during primary RSV infection prevented the subsequent enhancement of airway hyperresponsiveness and the development of airway eosinophilia and mucus hyperproduction on reinfection. Administration of anti-TSLP before neonatal RSV infection reduced the accumulation of lung DCs, decreased OX40L expression on lung DCs, and attenuated the enhancement of airway responses after reinfection.

CONCLUSIONS

In mice initially infected as neonates, TSLP expression induced by RSV infection is an important upstream event that controls OX40L expression, lung DC migration, and T(H)2 polarization, accounting for the enhanced response on reinfection.

SOX40L: An Important Inflammatory Mediator in Adult Bronchial Asthma

Introduction: The role of soluble OX40 ligand (sOX40L) in adult bronchial asthma is unclear. This study aims to determine the serum concentrations of sOX40L in adult patients with bronchial asthma, and discussed its relationship with pulmonary function. Materials and Methods: We measured the pulmonary function using the spirometer and detected the serum concentrations of sOX40L by enzyme linked immunosorbent assay (ELISA) in 19 healthy persons in the control group, 58 acute asthmatic adult patients who were grouped according to their disease severity: 18 mild grade, 24 moderate grade, 16 severe grade, and 24 persons in a stable asthmatic group. Results: The serum concentrations of sOX40L in asthmatic adult patients (6.80 ± 4.95 ng/L) were distinctly higher than those in the control group (3.98 ± 2.83 ng/L, P <0.05), and they were negatively correlated with pulmonary function indexes (FEV1%, FVC%, FEV1/FVC) (r = –0.754, P <0.01, r = –0.557, P <0.01, r = –0.457, P <0.01, respectively). Moreover, the serum concentrations of sOX40L showed obvious differences among control, mild, moderate, and severe groups (3.98 ± 2.83, 4.87 ± 1.89, 6.97 ± 5.91, 8.71 ± 5.18 ng/L, respectively; P <0.01). The concentrations of sOX40L decreased to the same extent as the control group after therapeutic treatments were provided to the asthmatic adult patients. Conclusion: The concentrations of sOX40L were found to be high in adult asthmatic patients and were associated with the severity of the disease. Therefore, sOX40L could be a potential inflammatory mediator in the pathogenesis of asthma. Key words: Co-stimulatory, Pulmonary function, ELISA, Soluble OX40 ligand

OX40/OX40 ligand interactions in T-cell regulation and asthma

The OX40 receptor is preferentially expressed by T cells, and its cognate ligand OX40L is primarily expressed by antigen-presenting cells such as dendritic cells following activation by thymic stromal lymphopoietin (TSLP). TSLP is released by the bronchial epithelium, airway smooth muscle, and some inflammatory cells in response to numerous insults such as allergens, viruses, and physical damage. OX40L is a costimulatory molecule that plays a sentinel role in the adaptive immune response by promoting T helper (Th) 2 polarization of naive T cells within the lymph node. These polarized T cells produce Th2 cytokines such as IL-4, IL-5, and IL-13, which have been implicated particularly in allergic eosinophilic asthma. Animal models have positioned both TSLP and OX40/OX40L as critical in the development of airway inflammation and hyperreactivity. In human disease, there is good evidence that TSLP is upregulated in asthma, but there are limited data to demonstrate overexpression of OX40 or OX40L in disease. Targeting the OX40/OX40L axis or TSLP presents a novel therapeutic strategy that has the potential of modifying the disease process and, therefore, impacting on its natural history. Whether this approach can demonstrate efficacy in established disease rather than at disease onset is unknown. Biologic therapies directed toward OX40/OX40L are in early phases of development, and results from these studies are eagerly awaited.

Cellular and molecular mechanisms of TSLP function in human allergic disorders--TSLP programs the "Th2 code" in dendritic cells

Thymic stromal lymphopoietin (TSLP) has been recently implicated as a key molecule for initiating allergic inflammation at the epithelial cell-dendritic cell (DC) interface. In humans, aberrant TSLP expression is observed in allergic tissues, such as lesional skins of atopic dermatitis, lungs of asthmatics, nasal mucosa of atopic rhinitis and nasal polyps, and ocular surface of allergic keratoconjunctivitis. TSLP is produced predominantly by damaged epithelial cells and stimulates myeloid DCs (mDCs). TSLP-activated mDCs can promote the differentiation of naïve CD4(+) T cells into a Th2 phenotype and the expansion of CD4(+) Th2 memory cells in a unique manner dependent on OX40L, one of the tumor necrosis factor superfamily members with Th2-promoting function, and lack of production of IL-12. From a genetic point of view, multiple genome-wide association studies have repeatedly identified the TSLP gene as one of the loci associated with susceptibility to allergic diseases. Thus, TSLP is a rational therapeutic target for the treatment of allergic disorders. Elucidating the mechanisms that regulate TSLP expression and the effects of TSLP on orchestrating the immune response toward a Th2 phenotype is essential for developing anti-TSLP therapy.