Amelioration of experimental autoimmune encephalomyelitis with anti-OX40 ligand monoclonal antibody: a critical role for OX40 ligand in migration, but not development, of pathogenic T cells

A novel anti-OX40 human monoclonal antibody that blocks OX40/OX40L signaling and depletes OX40+ T cells

Tumor necrosis factor receptor superfamily member 4 (TNFRSF4), also known as OX40, plays a crucial role in the regulation of T-cell immune responses under normal physiological conditions. Abnormal expression of OX40 and its cognate ligand OX40L (TNFSF4) have been associated with various autoimmune diseases, indicating that blocking the OX40/OX40L pathway could be a promising strategy for the treatment of a broad range of T cell-mediated autoimmune diseases. Here, we screened and characterized a fully human anti-OX40 antibody (JY007) from a naïve human scFv phage library. JY007 has an affinity constant of 7.71 nmol/L and effectively inhibited the OX40-OX40L interaction at both molecular and cellular levels, with IC50 values of 1.088 and 10.12 nmol/L, respectively. Furthermore, JY007 demonstrated the ability to deplete activated T lymphocytes through antibody-dependent cellular cytotoxicity (ADCC) activity, with an EC50 of 5.592 pmol/L. The combination of ADCC and its antagonist activity against OX40 suggests potential efficacy in suppressing inflammatory responses mediated by the OX40/OX40L pathway. Additionally, we employed molecular docking, site-directed mutagenesis, and competitive ELISA to pinpoint the epitopes on OX40. The results revealed that JY007 binds to Pro37, Ser38, and Asp40 of OX40. Interestingly, we also found that the most potent anti-OX40 antibody drug in the clinical stage, KHK4083, binds to different OX40 amino-acid residues, including Asp74, Lys82, Asp117, Ser118, Tyr119, and Lys120. This divergence suggests that the novel monoclonal antibody JY007 holds promise as a potential therapeutic option for patients with atopic dermatitis and may find broad applications in the treatment of autoimmune diseases.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-025-00284-y.

The bidirectional immune crosstalk in metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) is an unabated risk factor for end-stage liver diseases with no available therapies. Dysregulated immune responses are critical culprits of MASLD pathogenesis. Independent contributions from either the innate or adaptive arms of the immune system or their unidirectional interplay are commonly studied in MASLD. However, the bidirectional communication between innate and adaptive immune systems and its impact on MASLD remain insufficiently understood. Given that both innate and adaptive immune cells are indispensable for the development and progression of inflammation in MASLD, elucidating pathogenic contributions stemming from the bidirectional interplay between these two arms holds potential for development of novel therapeutics for MASLD. Here, we review the immune cell types and bidirectional pathways that influence the pathogenesis of MASLD and highlight potential pharmacologic approaches to combat MASLD based on current knowledge of this bidirectional crosstalk.

Comparison of OX40 expression in patients with multiple sclerosis and neuromyelitis optica as an approach to diagnosis

BACKGROUND

Previous studies have shown that CD134 (OX40) co-stimulation is involved in the pathogenesis of experimental autoimmune encephalomyelitis (EAE) models and the antigen is expressed within multiple sclerosis lesions in humans. OX40 (CD134) is thought to be a secondary co-stimulatory immune checkpoint molecule that is expressed by T cells. This study aimed to evaluate the mRNA expression of OX40 and its serum levels in the peripheral blood of patients with Multiple Sclerosis (MS) or Neuromyelitis Optica (NMO).

METHODS

Patients with MS (n = 60), NMO (n = 20), and 20 healthy subjects were recruited from Sina Hospital, Tehran, Iran. The diagnoses were confirmed by a specialist in clinical neurology. Peripheral venous blood was obtained from all subjects, and mRNA quantification of OX40 was conducted using real-time PCR. Serum samples were also obtained and the concentration of OX40 was determined using an enzyme-linked immunosorbent assay (ELISA).

RESULTS

There was a significant correlation between the mRNA expression and serum levels of OX40 and disability as assessed using the expanded disability status scale (EDSS) in the patients with MS, but not in the patients with NMO. Expression of OX40 mRNA was significantly higher in the peripheral blood of MS patients compared to healthy individuals and NMO patients (*P < 0.05). In addition, serum OX40 concentrations were also significantly higher in patients with MS patients compared with healthy subjects (9.08 ± 2.48 vs. 1.49 ± 0.54 ng/ml; P = 0.041).

CONCLUSIONS

It appears that an increased expression of OX40 may be associated with the hyperactivation of T cells in patients with MS, and this may play a role in the pathogenesis of the disease.

Activation pathways that drive CD4+ T cells to break tolerance in autoimmune diseases. Immunol Rev 2022;307:161-190. [PMID: 35142369 PMCID: PMC9255211 DOI: 10.1111/imr.13071]

Autoimmune diseases are characterized by dysfunctional immune systems that misrecognize self as non-self and cause tissue destruction. Several cell types have been implicated in triggering and sustaining disease. Due to a strong association of major histocompatibility complex II (MHC-II) proteins with various autoimmune diseases, CD4+ T lymphocytes have been thoroughly investigated for their roles in dictating disease course. CD4+ T cell activation is a coordinated process that requires three distinct signals: Signal 1, which is mediated by antigen recognition on MHC-II molecules; Signal 2, which boosts signal 1 in a costimulatory manner; and Signal 3, which helps to differentiate the activated cells into functionally relevant subsets. These signals are disrupted during autoimmunity and prompt CD4+ T cells to break tolerance. Herein, we review our current understanding of how each of the three signals plays a role in three different autoimmune diseases and highlight the genetic polymorphisms that predispose individuals to autoimmunity. We also discuss the drawbacks of existing therapies and how they can be addressed to achieve lasting tolerance in patients.

OX40L Inhibition Suppresses KLH‐driven Immune Responses in Healthy Volunteers: A Randomized Controlled Trial Demonstrating Proof‐of‐Pharmacology for KY1005

The safety, tolerability, immunogenicity, and pharmacokinetic (PK) profile of an anti‐OX40L monoclonal antibody (KY1005, currently amlitelimab) were evaluated. Pharmacodynamic (PD) effects were explored using keyhole limpet hemocyanin (KLH) and tetanus toxoid (TT) immunizations. Sixty‐four healthy male subjects (26.5 ± 6.0 years) were randomized to single doses of 0.006, 0.018, or 0.05 mg/kg, or multiple doses of 0.15, 0.45, 1.35, 4, or 12 mg/kg KY1005, or placebo (6:2). Serum KY1005 concentrations were measured. Antibody responses upon KLH and TT immunizations and skin response upon intradermal KLH administration were performed. PD data were analyzed using repeated measures analysis of covariances (ANCOVAs) and post hoc exposure‐response modeling. No serious adverse events occurred and all adverse events were temporary and of mild or moderate severity. A nonlinear increase in mean serum KY1005 concentrations was observed (median time to maximum concentration (T_max) ~ 4 hours, geometric mean terminal half‐life (t½) ~ 24 days). Cutaneous blood perfusion (estimated difference (ED) −13.4 arbitrary unit (AU), 95% confidence interval (CI) −23.0 AU to −3.8 AU) and erythema quantified as average redness (ED −0.23 AU, 95% CI −0.35 AU to −0.11 AU) decreased after KY1005 treatment at doses of 0.45 mg/kg and above. Exposure‐response analysis displayed a statistically significant treatment effect on anti‐KLH antibody titers (IgG maximum effect (E_max) −0.58 AU, 95% CI −1.10 AU to −0.06 AU) and skin response (erythema E_max −0.20 AU, 95% CI −0.29 AU to −0.11 AU). Administration of KY1005 demonstrated an acceptable safety and tolerability profile and PK analyses displayed a nonlinear profile of KY1005. Despite the observed variability, skin challenge response after KY1005 treatment indicated pharmacological activity of KY1005. Therefore, KY1005 shows potential as a novel pharmacological treatment in immune‐mediated disorders.

The OX40/OX40L Axis Regulates T Follicular Helper Cell Differentiation: Implications for Autoimmune Diseases

T Follicular helper (Tfh) cells, a unique subset of CD4+ T cells, play an essential role in B cell development and the formation of germinal centers (GCs). Tfh differentiation depends on various factors including cytokines, transcription factors and multiple costimulatory molecules. Given that OX40 signaling is critical for costimulating T cell activation and function, its roles in regulating Tfh cells have attracted widespread attention. Recent data have shown that OX40/OX40L signaling can not only promote Tfh cell differentiation and maintain cell survival, but also enhance the helper function of Tfh for B cells. Moreover, upregulated OX40 signaling is related to abnormal Tfh activity that causes autoimmune diseases. This review describes the roles of OX40/OX40L in Tfh biology, including the mechanisms by which OX40 signaling regulates Tfh cell differentiation and functions, and their close relationship with autoimmune diseases.

Pro-inflammatory dopamine-2 receptor-specific T cells in paediatric movement and psychiatric disorders

Objectives

A dysregulated inflammatory response against the dopamine‐2 receptor (D2R) has been implicated in movement and psychiatric disorders. D2R antibodies were previously reported in a subset of these patients; however, the role of T cells in these disorders remains unknown. Our objective was to identify and characterise pro‐inflammatory D2R‐specific T cells in movement and psychiatric disorders.

Methods

Blood from paediatric patients with movement and psychiatric disorders of suspected autoimmune and neurodevelopmental aetiology (n = 24) and controls (n = 16) was cultured in vitro with a human D2R peptide library, and D2R‐specific T cells were identified by flow cytometric quantification of CD4⁺CD25⁺CD134⁺ T cells. Cytokine secretion was analysed using a cytometric bead array and ELISA. HLA genotypes were examined in D2R‐specific T‐cell‐positive patients. D2R antibody seropositivity was determined using a flow cytometry live cell‐based assay.

Results

Three immunodominant regions of D2R, amino acid (aa)121–131, aa171–181 and aa396–416, specifically activated CD4⁺ T cells in 8/24 patients. Peptides corresponding to these regions were predicted to bind with high affinity to the HLA of the eight positive patients and had also elicited the secretion of pro‐inflammatory cytokines IL‐2, IFN‐ γ, TNF, IL‐6, IL‐17A and IL‐17F. All eight patients were seronegative for D2R antibodies.

Conclusion

Autoreactive D2R‐specific T cells and a pro‐inflammatory Th1 and Th17 cytokine profile characterise a subset of paediatric patients with movement and psychiatric disorders, further underpinning the theory of immune dysregulation in these disorders. These findings offer new perspectives into the neuroinflammatory mechanisms of movement and psychiatric disorders and can influence patient diagnosis and treatment.

Associations between TNFSF4 gene polymorphisms (rs2205960 G > A, rs704840 T > G and rs844648 G > A) and susceptibility to autoimmune diseases in Asians: a meta-analysis

BACKGROUND

Tumor necrosis factor superfamily member 4 (TNFSF4) has significant role in modulating autoimmune diseases (ADs) and single nucleotide polymorphism (SNP) is also related with the susceptibility to some diseases. So a meta-analysis aimed at systematically assessing the associations between TNFSF4 polymorphisms (rs2205960 G > A, rs704840 T > G and rs844648 G > A) and ADs risk was performed in Asians.

METHODS

Total 14 eligible articles published before March 2019 involving 35 studies, of which 21 studies (16,109 cases and 26,378 controls) for rs2205960 G > A, 8 studies (2,424 cases and 3,692 controls) for rs704840 T > G, and 6 studies (3,839 cases and 5,867 controls) for rs844648 G > A were included. Effects of the three respective polymorphisms on the susceptibility to ADs were estimated by pooling the odds ratios (ORs) with their corresponding 95% confidence interval (95% CI) in allelic, dominant, recessive, heterozygous and homozygous models.

RESULTS

The overall analysis revealed that all the rs2205960 G > A, rs704840 T > G and rs844648 G > A polymorphisms could increase the risk of ADs in allelic, dominant, recessive, heterozygous and homozygous models. Furthermore, subgroup analysis showed that both rs2205960 G > A and rs704840 T > G were significantly associated with the susceptibility to systemic lupus erythematosus (SLE). What's more, statistically significant association between rs2205960 G > A polymorphism and primary Sjögren's syndrome (pSS) susceptibility was also observed in allelic, dominant and heterozygous models.

CONCLUSIONS

This current meta-analysis suggested that all of the three TNFSF4 polymorphisms may be associated with ADs susceptibility in Asians.

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.

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.

Central Roles of OX40L-OX40 Interaction in the Induction and Progression of Human T Cell-Driven Acute Graft-versus-Host Disease

Graft-versus-host disease (GVHD) is one of the major obstacles for the success of allogeneic hematopoietic stem cell transplantation. Here, we report that the interaction between OX40L and OX40 is of critical importance for both induction and progression of acute GVHD (aGVHD) driven by human T cells. Anti-human OX40L monoclonal antibody (hOX40L) treatment could thus effectively reduce the disease severity in a xenogeneic-aGVHD (x-aGVHD) model in both preventative and therapeutic modes. Mechanistically, blocking OX40L-OX40 interaction with an anti-hOX40L antibody reduces infiltration of human T cells in target organs, including liver, gut, lung, and skin. It also decreases IL-21- and TNF-producing T cell responses, while promoting regulatory T cell (Treg) responses without compromising the cytolytic activity of CD8⁺ T cells. Single blockade of hOX40L was thus more effective than dual blockade of IL-21 and TNF in reducing the severity of aGVHD as well as mortality. Data from this study indicate that OX40L-OX40 interactions play a central role in the pathogenesis of aGVHD induced by human T cells. Therapeutic strategies that can efficiently interrupt OX40L-OX40 interaction in patients might have potential to provide patients with an improved clinical benefit.

IQGAP1 restrains T-cell cosignaling mediated by OX40

A costimulatory signal from the tumor necrosis factor receptor (TNFR) family molecule OX40 (CD134), which is induced on activated T cells, is important for T-cell immunity. Aberrant OX40 cosignaling has been implicated in autoimmune and inflammatory disorders. However, the molecular mechanism by which the OX40 cosignaling regulates the T-cell response remains obscure. We found that OX40 associated with a scaffold protein, IQ motif-containing GTPase-activating protein 1 (IQGAP1) after ligation by its ligand OX40L. Naïve CD4⁺ T cells from Iqgap1^-/- mice displayed enhanced proliferation and cytokine secretion upon receiving OX40 cosignaling. A C-terminal IQGAP1 region was responsible for its association with OX40, and TNFR-associated factor 2 (TRAF2) bridged these two proteins. The enhanced cytokine response in Iqgap1^-/- T cells was restored by the expression of the C-terminal IQGAP1. Thus, the IQGAP1 binding limits the OX40 cosignaling. Disease severity of experimental autoimmune encephalomyelitis (EAE) was significantly exacerbated in Iqgap1^-/- mice as compared to wild-type mice. Additionally, recipient mice with Iqgap1^-/- donor CD4⁺ T cells exhibited significantly higher EAE scores than those with their wild-type counterparts, and OX40 blockade led to a significant reduction in the EAE severity. Thus, our study defines an important component of the OX40 cosignaling that restricts inflammation driven by antigen-activated T cells.

Targeting Costimulatory Pathways in Systemic Sclerosis

Systemic sclerosis (SSc) is an autoimmune T-cell disease that is characterized by pathological fibrosis of the skin and internal organs. SSc is considered a prototype condition for studying the links between autoimmunity and fibrosis. Costimulatory pathways such as CD28/CTLA-4, ICOS-B7RP1, CD70-CD27, CD40-CD154, or OX40-OX40L play an essential role in the modulation of T-cell and inflammatory immune responses. A growing body of evidence suggests that T-cell costimulation signals might be implicated in the pathogenesis of SSc. CD28, CTLA-4, ICOS, and OX40L are overexpressed in patients with SSc, particularly in patients with cutaneous diffuse forms. In pre-clinical models of SSc, T-cell costimulation blockade with abatacept (CTLA-4-Ig) prevented and induced the regression of inflammation-driven dermal fibrosis, improved digestive involvement, prevented lung fibrosis, and attenuated pulmonary hypertension in complementary models of SSc. Likewise, potent anti-fibrotic effects were seen with the blockade of OX40L by reducing the infiltration of inflammatory cells into lesional tissues leading to decreased fibroblast activation. Concerning clinical effects, a preliminary observational study suggested some effectiveness of abatacept on inflammatory joint involvement, whereas clinical improvement of skin fibrosis was observed in a small placebo-controlled randomized trial. Currently there is one ongoing phase II clinical trial assessing the efficacy of abatacept in SSc (ASSET trial, NCT02161406). Overall, given the lack of available effective agents and the known toxic effects of immunosuppressive agents approved for use in SSc, costimulatory pathways offer the advantage of a targeted approach to costimulatory signals and potentially a better safety profile.

The immunological synapse as a pharmacological target

The development of T cell mediated immunity relies on the assembly of a highly specialized interface between T cell and antigen presenting cell (APC), known as the immunological synapse (IS). IS assembly is triggered when the T cell receptor (TCR) binds to specific peptide antigen presented in association to the major histocompatibility complex (MHC) by the APC, and is followed by the spatiotemporal dynamic redistribution of TCR, integrins, co-stimulatory receptors and signaling molecules, allowing for the fine-tuning and integration of the signals that lead to T cell activation. The knowledge acquired to date about the mechanisms of IS assembly underscores this structure as a robust pharmacological target. The activity of molecules involved in IS assembly and function can be targeted by specific compounds to modulate the immune response in a number of disorders, including cancers and autoimmune diseases, or in transplanted patients. Here, we will review the state-of-the art of the current therapies which exploit the IS to modulate the immune response.

Association of TNFSF4 Polymorphisms with Neuromyelitis Optica Spectrum Disorders in a Chinese Population

The tumor necrosis factor ligand superfamily member 4 (TNFSF4) gene encodes a vital co-stimulatory molecule of the immune system and has been identified as a susceptibility locus for systemic lupus erythematosus, systemic sclerosis, and primary Sjögren's syndrome. However, the association of TNFSF4 polymorphisms with neuromyelitis optica spectrum disorders (NMOSD), an inflammatory, demyelinating autoimmune disease of the central nervous system, has not yet been investigated. To evaluate whether TNFSF4 polymorphisms contribute to risk of NMOSD, four single-nucleotide polymorphisms (SNPs) (rs1234315, rs2205960, rs704840, and rs844648) were selected and genotyped in a cohort of 312 patients with NMOSD and 487 healthy controls. Our study showed that rs844648 was associated with an increased risk of NMOSD, according to the allelic model (OR = 1.30, 95% CI 1.06-1.59, P = 0.011, Pcorr = 0.044). Significant associations of rs844648 (OR = 1.67, 95% CI 1.17-2.38, P = 0.005, Pcorr = 0.02) and rs704840 (OR = 1.75, 95% CI 1.17-2.63, P = 0.007, Pcorr = 0.027) with NMOSD occurrence were also observed under the recessive model. Moreover, linkage disequilibrium analysis revealed two blocks within TNFSF4; in one block, the haplotype A_rs844648G_rs704840 significantly increased the risk of NMOSD, whereas G_rs844648T_rs704840 reduced the risk. This study demonstrates an association between TNFSF4 polymorphisms and susceptibility for the development of NMOSD in the Chinese population.

Monoclonal Antibodies in Preclinical EAE Models of Multiple Sclerosis: A Systematic Review

Monoclonal antibodies (mAb) are promising therapeutics in multiple sclerosis and multiple new candidates have been developed, hence increasing the need for some agreement for preclinical mAb studies. We systematically analyzed publications of experimental autoimmune encephalomyelitis (EAE) studies showing effects of monoclonal antibodies. A PubMed search retrieved 570 records, out of which 122 studies with 253 experiments were eligible based on experimental design, number of animals and presentation of time courses of EAE scores. Analysis of EAE models, treatment schedules, single and total doses, routes of administration, and onset of treatment from pre-immunization up to 35 days after immunization revealed high heterogeneity. Total doses ranged from 0.1 to 360 mg/kg for observation times of up to 35 days after immunization. About half of experiments (142/253) used total doses of 10-70 mg/kg. Employing this range, we tested anti-Itga4 as a reference mAb at varying schedules and got no, mild or substantial EAE-score reductions, depending on the mouse strain and onset of the treatment. The result agrees with the range of outcomes achieved in 10 reported anti-Itga4 experiments. Studies comparing low and high doses of various mAbs or early vs. late onset of treatment did not reveal dose-effect or timing-effect associations, with a tendency towards better outcomes with preventive treatments starting within the first week after immunization. The systematic comparison allows for extraction of some "common" design characteristics, which may be helpful to further assess the efficacy of mAbs and role of specific targets in preclinical models of multiple sclerosis.

Co-stimulatory and Co-inhibitory Pathways in Autoimmunity

The immune system is guided by a series of checks and balances, a major component of which is a large array of co-stimulatory and co-inhibitory pathways that modulate the host response. Although co-stimulation is essential for boosting and shaping the initial response following signaling through the antigen receptor, inhibitory pathways are also critical for modulating the immune response. Excessive co-stimulation and/or insufficient co-inhibition can lead to a breakdown of self-tolerance and thus to autoimmunity. In this review, we will focus on the role of co-stimulatory and co-inhibitory pathways in two systemic (systemic lupus erythematosus and rheumatoid arthritis) and two organ-specific (multiple sclerosis and type 1 diabetes) emblematic autoimmune diseases. We will also discuss how mechanistic analysis of these pathways has led to the identification of potential therapeutic targets and initiation of clinical trials for autoimmune diseases, as well as outline some of the challenges that lie ahead.

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.

OX40, OX40L and Autoimmunity: a Comprehensive Review

The tumour necrosis factor receptor OX40 (CD134) is activated by its cognate ligand OX40L (CD134L, CD252) and functions as a T cell co-stimulatory molecule. OX40-OX40L interactions have been proposed as a potential therapeutic target for treating autoimmunity. OX40 is expressed on activated T cells, and in the mouse at rest on regulatory T cells (Treg). OX40L is found on antigen-presenting cells, activated T cells and others including lymphoid tissue inducer cells, some endothelia and mast cells. Expression of both molecules is increased after antigen presentation occurs and also in response to multiple other pro-inflammatory factors including CD28 ligation, CD40L ligation and interferon-gamma signaling. Their interactions promote T cell survival, promote an effector T cell phenotype, promote T cell memory, tend to reduce regulatory function, increase effector cytokine production and enhance cell mobility. In some circumstances, OX40 agonism may be associated with increased tolerance, although timing with respect to antigenic stimulus is important. Further, recent work has suggested that OX40L blockade may be more effective than OX40 blockade in reducing autoimmunity. This article reviews the expression of OX40 and OX40L in health, the effects of their interactions and insights from their under- or over-expression. We then review OX40 and OX40L expression in human autoimmune disease, identified associations of variations in their genes (TNFRSF4 and TNFSF4, respectively) with autoimmunity, and data from animal models of human diseases. A rationale for blocking OX40-OX40L interaction in human autoimmunity is then presented along with commentary on the one trial of OX40L blockade in human disease conducted to date. Finally, we discuss potential problems with clinical use of OX40-OX40L directed pharmacotherapy.

Cellular and Molecular Mechanisms of Autoimmunity and Lupus Nephritis

Autoimmunity involves immune responses directed against self, which are a result of defective self/foreign distinction of the immune system, leading to proliferation of self-reactive lymphocytes, and is characterized by systemic, as well as tissue-specific, inflammation. Numerous mechanisms operate to ensure the immune tolerance to self-antigens. However, monogenetic defects or genetic variants that weaken immune tolerance render susceptibility to the loss of immune tolerance, which is further triggered by environmental factors. In this review, we discuss the phenomenon of immune tolerance, genetic and environmental factors that influence the immune tolerance, factors that induce autoimmunity such as epigenetic and transcription factors, neutrophil extracellular trap formation, extracellular vesicles, ion channels, and lipid mediators, as well as costimulatory or coinhibitory molecules that contribute to an autoimmune response. Further, we discuss the cellular and molecular mechanisms of autoimmune tissue injury and inflammation during systemic lupus erythematosus and lupus nephritis.

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.

Enhancement of CD4(+) T cell response and survival via coexpressed OX40/OX40L in Graves' disease

OX40/OX40L pathway plays a very important role in the antigen priming T cells and effector T cells. In the present study, we aimed to examine the involvement of OX40/OX40L pathway in the activation of autoreactive T cells in patients with Grave's disease (GD). We found that OX40 and OX40L were constitutively coexpressed on peripheral CD4(+) T cells from GD patients using flow cytometry analysis. The levels of OX40 and OX40L coexpression on CD4(+) T cells were shown to be correlated with TRAbs. Cell proliferation assay showed that blocking OX40/OX40L signal inhibited T cell proliferation and survival, which suggested that OX40/OX40L could enhance CD4(+) T cell proliferation and maintain their long-term survival in GD by self-enhancing loop of T cell activation independent of APCs. Confocal microscopy and coimmunoprecipitation analysis further revealed that OX40 and OX40L formed a functional complex, which may facilitate signal transduction from OX40L to OX40 and contribute to the pathogenesis of GD.

Death Ligands and Autoimmune Demyelination

Death ligands induce apoptosis, which is a cell suicide program leading mainly to selective elimination of an organism's useless cells. Importantly, the dying cell is an active participant in its own demise (“cellular suicide”). Under physiological conditions, apoptosis is most often found during normal cell turnover and tissue homeostasis, embryogenesis, induction and maintenance of immune tolerance, development of the nervous system, and endocrine-dependent tissue atrophy. However, apoptotic processes have also been suggested to contribute to the pathology of the autoimmune demyelinating disease multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis. Here, apoptosis plays a double role. On one hand, impaired apoptosis may result in increased numbers or persistence of activated myelinspecific T cells. On the other hand, local tissue damage involves apoptosis of oligodendrocytes and neurons, leading to the clinical symptoms. In this article, an overview is given of the current knowledge of the roles of apoptosis-mediating and immune regulatory death ligands of the tumor necrosis factor (TNF) family (TNF, lymphotoxin-beta, OX40L [CD134L], CD154 [CD40L], CD95L, CD70 [CD27L], CD153 [CD30L], 4-1BBL [CD137L], TRAIL, TWEAK, BAFF, GITRL) in the pathogenesis of MS and of their implications for related therapeutic strategies.

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.

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.

VBP15, a novel anti-inflammatory, is effective at reducing the severity of murine experimental autoimmune encephalomyelitis

Multiple sclerosis is a chronic disease of the central nervous system characterized by an autoimmune inflammatory reaction that leads to axonal demyelination and tissue damage. Glucocorticoids, such as prednisolone, are effective in the treatment of multiple sclerosis in large part due to their ability to inhibit pro-inflammatory pathways (e.g., NFκB). However, despite their effectiveness, long-term treatment is limited by adverse side effects. VBP15 is a recently described compound synthesized based on the lazeroid steroidal backbone that shows activity in acute and chronic inflammatory conditions, yet displays a much-reduced side effect profile compared to traditional glucocorticoids. The purpose of this study was to determine the effectiveness of VBP15 in inhibiting inflammation and disease progression in experimental autoimmune encephalomyelitis (EAE), a widely used mouse model of multiple sclerosis. Our data show that VBP15 is effective at reducing both disease onset and severity. In parallel studies, we observed that VBP15 was able to inhibit the production of NFκB-regulated pro-inflammatory transcripts in human macrophages. Furthermore, treatment with prednisolone-but not VBP15-increased expression of genes associated with bone loss and muscle atrophy, suggesting lack of side effects of VBP15. These findings suggest that VBP15 may represent a potentially safer alternative to traditional glucocorticoids in the treatment of multiple sclerosis and other inflammatory diseases.

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.

Effector T cells boost regulatory T cell expansion by IL-2, TNF, OX40, and plasmacytoid dendritic cells depending on the immune context

CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cells play a major role in peripheral tolerance. Multiple environmental factors and cell types affect their biology. Among them, activated effector CD4(+) T cells can boost Treg cell expansion through TNF or IL-2. In this study, we further characterized this effector T (Teff) cell-dependent Treg cell boost in vivo in mice. This phenomenon was observed when both Treg and Teff cells were activated by their cognate Ag, with the latter being the same or different. Also, when Treg cells highly proliferated on their own, there was no additional Treg cell boost by Teff cells. In a condition of low inflammation, the Teff cell-mediated Treg cell boost involved TNF, OX40L, and plasmacytoid dendritic cells, whereas in a condition of high inflammation, it involved TNF and IL-2. Thus, this feedback mechanism in which Treg cells are highly activated by their Teff cell counterparts depends on the immune context for its effectiveness and mechanism. This Teff cell-dependent Treg cell boost may be crucial to limit inflammatory and autoimmune responses.

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.

A diametric role for OX40 in the response of effector/memory CD4+ T cells and regulatory T cells to alloantigen

OX40 is a member of the TNFR superfamily that has potent costimulatory properties. Although the impact of blockade of the OX40-OX40 ligand (OX40L) pathway has been well documented in models of autoimmune disease, its effect on the rejection of allografts is less well defined. In this article, we show that the alloantigen-mediated activation of naive and memory CD4(+) T cells results in the induction of OX40 expression and that blockade of OX40-OX40L interactions prevents skin allograft rejection mediated by either subset of T cells. Moreover, a blocking anti-OX40 had no effect on the activation and proliferation of T cells; rather, effector T cells failed to accumulate in peripheral lymph nodes and subsequently migrate to skin allografts. This was found to be the result of an enhanced degree of cell death among proliferating effector cells. In clear contrast, blockade of OX40-OX40L interactions at the time of exposure to alloantigen enhanced the ability of regulatory T cells to suppress T cell responses to alloantigen by supporting, rather than diminishing, regulatory T cell survival. These data show that OX40-OX40L signaling contributes to the evolution of the adaptive immune response to an allograft via the differential control of alloreactive effector and regulatory T cell survival. Moreover, these data serve to further highlight OX40 and OX40L as therapeutic targets to assist the induction of tolerance to allografts and self-Ags.

Trans-ancestral studies fine map the SLE-susceptibility locus TNFSF4

We previously established an 80 kb haplotype upstream of TNFSF4 as a susceptibility locus in the autoimmune disease SLE. SLE-associated alleles at this locus are associated with inflammatory disorders, including atherosclerosis and ischaemic stroke. In Europeans, the TNFSF4 causal variants have remained elusive due to strong linkage disequilibrium exhibited by alleles spanning the region. Using a trans-ancestral approach to fine-map the locus, utilising 17,900 SLE and control subjects including Amerindian/Hispanics (1348 cases, 717 controls), African-Americans (AA) (1529, 2048) and better powered cohorts of Europeans and East Asians, we find strong association of risk alleles in all ethnicities; the AA association replicates in African-American Gullah (152,122). The best evidence of association comes from two adjacent markers: rs2205960-T (P=1.71 × 10(-34) , OR=1.43[1.26-1.60]) and rs1234317-T (P=1.16 × 10(-28) , OR=1.38[1.24-1.54]). Inference of fine-scale recombination rates for all populations tested finds the 80 kb risk and non-risk haplotypes in all except African-Americans. In this population the decay of recombination equates to an 11 kb risk haplotype, anchored in the 5' region proximal to TNFSF4 and tagged by rs2205960-T after 1000 Genomes phase 1 (v3) imputation. Conditional regression analyses delineate the 5' risk signal to rs2205960-T and the independent non-risk signal to rs1234314-C. Our case-only and SLE-control cohorts demonstrate robust association of rs2205960-T with autoantibody production. The rs2205960-T is predicted to form part of a decameric motif which binds NF-κBp65 with increased affinity compared to rs2205960-G. ChIP-seq data also indicate NF-κB interaction with the DNA sequence at this position in LCL cells. Our research suggests association of rs2205960-T with SLE across multiple groups and an independent non-risk signal at rs1234314-C. rs2205960-T is associated with autoantibody production and lymphopenia. Our data confirm a global signal at TNFSF4 and a role for the expressed product at multiple stages of lymphocyte dysregulation during SLE pathogenesis. We confirm the validity of trans-ancestral mapping in a complex trait.

Science gone translational: the OX40 agonist story

OX40 (CD134) is a tumor necrosis factor (TNF) receptor expressed primarily on activated CD4(+) and CD8(+) T cells and transmits a potent costimulatory signal when engaged. OX40 is transiently expressed after T-cell receptor engagement and is upregulated on the most recently antigen-activated T cells within inflammatory lesions (e.g. sites of autoimmune destruction and on tumor-infiltrating lymphocytes). Hence, it is an attractive target to modulate immune responses: OX40 blocking agents to inhibit undesirable inflammation or OX40 agonists to enhance immune responses. In regards to this review, OX40 agonists enhance anti-tumor immunity, which leads to therapeutic effects in mouse tumor models. A team of laboratory and clinical scientists at the Providence Cancer Center has collaborated to bring the preclinical observations in cancer models from the bench to the bedside. This review describes the journey from in vitro experiments through preclinical mouse models to the successful translation of the first OX40 agonist to the clinic for the treatment of patients with cancer.

The role of costimulatory receptors of the tumour necrosis factor receptor family in atherosclerosis

Atherosclerosis is a chronic inflammatory disease that is mediated by both the innate and adaptive immune responses. T lymphocytes, that together with B cells are the cellular effectors of the adaptive immune system, are currently endowed with crucial roles in the development and progression of atherosclerosis. Costimulatory receptors are a class of molecules expressed by T lymphocytes that regulate the activation of T cells and the generation of effector T-cell responses. In this review we present the roles of costimulatory receptors of the tumour necrosis factor receptor (TNFR) superfamily in atherosclerosis and discuss the implications for future therapies that could be used to specifically modulate the immune response of pathogenic T cells in this disease.

A single intrathecal injection of DNA and an asymmetric cationic lipid as lipoplexes ameliorates experimental autoimmune encephalomyelitis

Intrathecal delivery of gene therapeutics is a route of administration that overcomes several of the limitations that plague current immunosuppressive treatments for autoimmune diseases of the central nervous system (CNS). Here we report intrathecal delivery of small amounts (3 μg) of plasmid DNA that codes for an immunomodulatory fusion protein, OX40-TRAIL, composed of OX40, a tumor necrosis factor receptor, and tumor necrosis factor related apoptosis inducing ligand (TRAIL). This DNA was delivered in a formulated nucleic acid-lipid complex (lipoplexes) with an asymmetric two-chain cationic lipid myristoyl (14:0) and lauroyl (12:1) rosenthal inhibitor-substituted compound (MLRI) formed from the tetraalkylammonium glycerol-based compound N-(1-(2,3-dioleoyloxy)-propyl-N-1-(2-hydroxy)ethyl)-N,N-dimethyl ammonium iodide. Delivery and expression in the CNS of OX40-TRAIL in the mouse prior to onset of experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis, decreased the severity of clinical disease. We believe this preclinical demonstration of rapid, widespread, and biologically therapeutic nonviral gene delivery to the CNS is important in further development of clinical lipid-based therapeutics for CNS disorders.

OX40 Ligand Levels and High-Sensitivity C-Reactive Protein Levels in Blood from Local Coronary Plaque and the Femoral Artery in Patients with Acute Coronary Syndrome or Stable Angina

OX40 ligand (OX40L) and high-sensitivity C-reactive protein (hs-CRP) play important roles in the pathogenesis of atherosclerosis. In this study, consecutive patients with acute coronary syndrome (ACS; n = 90) or stable angina (SA; n = 40) and healthy control subjects ( n = 50) were evaluated to assess plasma OX40L and serum hs-CRP levels in local coronary plaque and the femoral artery. OX40L and hs-CRP levels in the femoral artery were significantly higher in patients with ACS compared with controls. OX40L and hs-CRP levels in local coronary plaque (OX40Lc and hs-CRPc, respectively) were significantly higher in ACS than in SA patients. OX40L and hs-CRP levels were positively correlated with each other and were also correlated with fibrinogen levels. The number of complex lesions was correlated with OX40Lc and hs-CRPc levels. It is concluded that the OX40Lc level was highly sensitive for evaluating the inflammatory response in ACS and elevated levels of OX40Lc may be a valuable predictive marker for increased risk of atherosclerotic progression in ACS patients.

Autoimmune therapies targeting costimulation and emerging trends in multivalent therapeutics

Proteins participating in immunological signaling have emerged as important targets for controlling the immune response. A multitude of receptor-ligand pairs that regulate signaling pathways of the immune response have been identified. In the complex milieu of immune signaling, therapeutic agents targeting mediators of cellular signaling often either activate an inflammatory immune response or induce tolerance. This review is primarily focused on therapeutics that inhibit the inflammatory immune response by targeting membrane-bound proteins regulating costimulation or mediating immune-cell adhesion. Many of these signals participate in larger, organized structures such as the immunological synapse. Receptor clustering and arrangement into organized structures is also reviewed and emerging trends implicating a potential role for multivalent therapeutics is posited.

Nasal cardiac myosin peptide treatment and OX40 blockade protect mice from acute and chronic virally-induced myocarditis

Myocarditis poses a severe health problem, can lead to dilated cardiomyopathy (DCM) and death, and is thought to be triggered by infections. Enteroviruses such as Coxsackie virus B3 (CVB3) have been implicated as a culprit, since they can cause acute and chronic heart disease in susceptible mice. CVB was detected in human cardiac myocytes in some cases, whereas acute CVB infection was thought to have caused death. Here we studied, whether nasal administration of cardiac myosin (CM) major histocompatibility class (MHC) II peptides CM₉₄₇-₉₆₀ and CM₇₃₅-₇₄₇ and OX40 blockade would be able to ameliorate immunopathology and heart disease in BALB/C mice infected with CVB3. We found that nasal CM-peptide prophylactic treatment significantly reduced myocarditis and mortality by enhancing Treg and IL-10 induction and that blockade of OX40 signaling could reduce heart inflammation when administered late during pathogenesis. Altogether, these results chart the way for novel prevention and intervention strategies for viral myocarditis.

Increased OX40 and soluble OX40 ligands in children with Henoch-Schonlein purpura: association with renal involvement

Henoch-Schonlein purpura (HSP) is one of the most common types of vasculitis disorders in childhood and is characterized by a rash, arthritis, abdominal pain, and renal involvement. T-lymphocyte activation is considered to play a critical role in vasculitis. However, the regulation of the T cells in HSP remains poorly understood. In this study, OX40/OX40L (CD134/CD252) costimulatory pathway, which could promote T-cell activation and long survival, was investigated. Results from 32 HSP patients and 25 healthy donors revealed that the freshly isolated CD4(+) T cells from patients with HSP expressed higher OX40 than that of the cells from healthy individuals. The levels of soluble OX40L (sOX40L) in the sera of patients with HSP were also much higher than the controls. Importantly, significantly elevated levels of OX40 on CD4(+) T cells and sOX40L in sera were detected in patients with HSP with nephritis compared to patients without nephritis, indicating both OX40 upregulation and sOX40L increase were closely associated with disease activity of the patients. Thus, circulating sOX40L could provide excessive costimulatory signal for CD4(+) OX40(+) T-cell activation, and OX40/OX40L signal might contribute to the development of HSP disease.

Activation of OX40 augments Th17 cytokine expression and antigen-specific uveitis

Uveitis is a major and common cause of visual disability. Recent studies have shown that Th17 cells are implicated in the pathogenesis of this serious intraocular disorder. Activated T cells express an inducible costimulatory molecule called OX40, and OX40 in turn promotes the activation and proliferation of these lymphocytes. Nevertheless, it is unclear whether OX40 plays a vital role in enhancing the effector function of Th17 cells as well as the severity of uveitis. In this study, we demonstrated an increase of OX40 transcription in ovalbumin-induced uveitis, whereas anti-OX40L antibody substantially inhibited the antigen-specific ocular inflammation. Next, results from flow cytometry showed that activated Th17 cells expressed OX40, and OX40-activating antibody significantly augmented the production of Th17 cytokines in vitro. To validate the impact of OX40 in vivo, we stimulated ovalbumin-specific T cells with the OX40-activating antibody. Compared to donor cells without OX40 activation, adoptive transfer of OX40-stimulated lymphocytes elicited more severe ocular inflammation. Furthermore, an interleukin-17-neutralizing antibody attenuated OX40-mediated uveitis. In conclusion, our findings suggest that activation of OX40 augments Th17 cell function and thereby contributes to ocular inflammation. This study thus enhances our knowledge of costimulatory molecule-mediated immunopathological mechanisms of uveitis and suggests a future therapeutic strategy to treat uveitis by the targeting of OX40.

OX40 ligand regulates inflammation and mortality in the innate immune response to sepsis

The initial phase of sepsis is characterized by massive inflammatory cytokine production that contributes to multisystem organ failure and death. Costimulatory molecules are a class of receptors capable of regulating cytokine production in adaptive immunity. Recent studies described their presence on neutrophils and monocytes, suggesting a potential role in the regulation of cytokine production in innate immunity. The purpose of this study was to determine the role for OX40-OX40 ligand (OX40L) interaction in the innate immune response to polymicrobial sepsis. Humans with sepsis demonstrated upregulation of OX40L on monocytes and neutrophils, with mortality and intensive care unit stay correlating with expression levels. In an animal model of polymicrobial sepsis, a direct role for OX40L in regulating inflammation was indicated by improved survival, decreased cytokine production, and a decrease in remote organ damage in OX40L(-/-) mice. The finding of similar results with an OX40L Ab suggests a potential therapeutic role for OX40L blockade in sepsis. The inability of anti-OX40L to provide significant protection in macrophage-depleted mice establishes macrophages as an indispensable cell type within the OX40/OX40L axis that helps to mediate the clinical signs of disease in sepsis. Conversely, the protective effect of anti-OX40L Ab in RAG1(-/-) mice further confirms a T cell-independent role for OX40L stimulation in sepsis. In conclusion, our data provide an in vivo role for the OX40/OX40L system in the innate immune response during polymicrobial sepsis and suggests a potential beneficial role for therapeutic blockade of OX40L in this devastating disorder.

Costimulatory molecule OX40/OX40L expression in ductal carcinoma in situ and invasive ductal carcinoma of breast: an immunohistochemistry-based pilot study

OX40, a membrane-bound member of the tumor-necrosis-factor-receptor (TNFR) superfamily, plays an important role in proliferation, survival and infiltration of activated T cells via binding to OX40L. Recent studies indicate that OX40/OX40L system mediates the adhesion and infiltration of adult T cell leukemia (ATL). Previously, we detected OX40 expression in breast carcinoma cell lines and tissues. The correlation of expression of OX40 and OX40L and clinical features in breast carcinogenesis, however, has not been well characterized. The expression of OX40 and OX40L in 107 invasive ductal carcinomas (IDCa), 9 ductal carcinomas in situ (DCIS), and 31 fibroadenomas from breast tissues and its relationship with the clinical features were determined using immunohistochemistry (peroxidase-conjugated polymer method, ChemMate™ Envision™ Detection kit). The positive immunostaining rates for OX40 in IDCa, DCIS and fibroadenomas from breast tissues were 85.0%, 66.7% and 38.7% respectively, showing a significant difference in OX40 expression among IDCa, DCIS and fibroadenoma of breast (z=5.206, P=0.001). Increased staining intensity of OX40 was associated with TNM stages (z=2.112, P=0.017). Meanwhile, a relation of OX40 expression with lymph node metastatic status in IDCa was found (P=0.041). The expression of OX40L did not show any obvious difference among IDCa, DCIS and fibroadenomas from breast tissues. OX40L expression was also not related to histopathological parameters in IDCa except for progesterone receptor (PR) being positive (P=0.005). However, a high coincidental positive rate for OX40 and OX40L was observed in biopsy samples with IDCa (P=0.017, Kappa=0.231). The present results suggest that high OX40 expression may be associated with malignant transformation, progression, invasion and metastasis in breast cancer biology.

Association of TNFSF4 (OX40L) polymorphisms with susceptibility to systemic sclerosis

OBJECTIVE

It is increasingly being appreciated that multiple autoimmune diseases share common susceptibility genes. The tumour necrosis factor ligand superfamily member 4 gene (TNFSF4, OX40L), which encodes for the T cell costimulatory molecule OX40 ligand, has been identified as a susceptibility gene for the development of systemic lupus erythematosus (SLE). Accordingly, the aim of the current study was to investigate the possible association of the TNFSF4 gene region with systemic sclerosis (SSc), an autoimmune disease that leads to the development of cutaneous and visceral fibrosis.

METHODS

A total of 9 single nucleotide polymorphisms (SNPs) in the TNFSF4 gene region, previously associated with susceptibility to SLE, were tested for association with SSc in a collection of 1059 patients with SSc and 698 controls.

RESULTS

Case-control comparisons revealed a significant association between susceptibility to SSc and the minor alleles at SNPs rs1234314 (OR 1.20, 95% CI 1.04 to 1.4, p(FDR)=0.019), rs2205960 (OR 1.24, 95% CI 1.10 to 1.50, p(FDR)=0.019) and rs844648 (OR 1.16, 95% CI 1.01 to 1.30, p(FDR)=0.032). The minor allele at rs844644 was protective (OR 0.84, 95% CI 0.70 to 0.97, p(FDR)=0.038). Analysis of subsets of patients with SSc demonstrated significant associations of the TNFSF4 SNPs with limited and diffuse SSc as well as specific SNPs that were associated with SSc-associated autoantibodies. Finally, the analyses suggest a potential interaction between two TNFSF4 SNPs, rs2205960 and rs844648, with regards to SSc susceptibility.

CONCLUSIONS

Polymorphisms in the TNFSF4 gene region are associated with susceptibility to SSc and its clinical and autoantibody subsets. TNFSF4 may be another gene that confers risk to multiple autoimmune diseases.

New insights into T cell biology and T cell-directed therapy for autoimmunity, inflammation, and immunosuppression

T cell-directed therapies have become mainstays in the management of various autoimmune diseases and organ transplantation. The understanding of T cell biology has expanded greatly since the development of most agents currently in use. Here we discuss important recent discoveries pertaining to T helper cell differentiation, lineage commitment, and function. Within this context, we examine existing T cell-directed therapies, including new agents being evaluated in clinical and preclinical studies. We also use recent findings to speculate on novel targets.

The role of OX40-mediated co-stimulation in T-cell activation and survival

The extent of T-cell activation, proliferation, and survival that follows T-cell receptor (TCR) ligation is controlled by several factors, including the strength of TCR stimulation, the availability of prosurvival cytokines, and the presence or absence of co-stimulatory signals. In addition to engagement of the CD28 co-stimulatory receptor by its natural ligands, B7.1 (CD80) and B7.2 (CD86), recent work has begun to elucidate the mechanisms by which signaling through the OX40 (CD134) co-stimulatory receptor, a member of the tumor necrosis factor receptor (TNFR) superfamily, affects T-cell responses. Importantly, OX40 ligation has been shown to augment CD4 and CD8 T-cell clonal expansion, effector differentiation, survival, and in some cases, abrogate the suppressive activity of regulatory FoxP3+CD25+CD4+ T cells. In this review, we focus on the mechanisms regulating OX40 expression on activated T cells as well as the role of OX40-mediated co-stimulation in boosting T-cell clonal expansion, effector differentiation, and survival.

Quantitation of peripheral blood markers of rat experimental autoimmune encephalomyelitis

Identification and quantitation of peripheral blood non-invasive, cell-surface markers of EAE disease activity and drug response would facilitate the preclinical development of potential therapeutics. Towards this end, we characterized the influx of immune mediators into spinal cords of diseased rats to establish the kinetics of T cell and monocyte-mediated inflammation. We then examined the periphery for regulation of T cell and monocyte activation. We report increased CD80 and VLA-4 expression on peripheral blood monocytes (PBM) during the onset and peak of experimental disease scores. Increased CD4+, CD62L - and CD4+, CD134+ T cells were detected only at disease peak, not during disease onset. PBM CD80 expression was significantly inhibited in CSA-treated animals, but increased in Dex-treated animals. PBM VLA-4 expression was unaffected by drug treatment. Both CSA and Dex inhibited CD62L shedding and CD134 expression on peripheral CD4+ T cells. These results identify quantitative, peripheral markers of disease activity and drug response.

The significance of OX40 and OX40L to T-cell biology and immune disease

SUMMARY

OX40 (CD134) and its binding partner, OX40L (CD252), are members of the tumor necrosis factor receptor/tumor necrosis factor superfamily and are expressed on activated CD4(+) and CD8(+) T cells as well as on a number of other lymphoid and non-lymphoid cells. Costimulatory signals from OX40 to a conventional T cell promote division and survival, augmenting the clonal expansion of effector and memory populations as they are being generated to antigen. OX40 additionally suppresses the differentiation and activity of T-regulatory cells, further amplifying this process. OX40 and OX40L also regulate cytokine production from T cells, antigen-presenting cells, natural killer cells, and natural killer T cells, and modulate cytokine receptor signaling. In line with these important modulatory functions, OX40-OX40L interactions have been found to play a central role in the development of multiple inflammatory and autoimmune diseases, making them attractive candidates for intervention in the clinic. Conversely, stimulating OX40 has shown it to be a candidate for therapeutic immunization strategies for cancer and infectious disease. This review provides a broad overview of the biology of OX40 including the intracellular signals from OX40 that impact many aspects of immune function and have promoted OX40 as one of the most prominent costimulatory molecules known to control T cells.

OX40 (CD134) and OX40L

The interaction between OX40 and OX40L plays an important role in antigen-specific T-cell expansion and survival. While OX40 is expressed predominantly on T-lymphocytes early after antigen activation, OX40L is expressed on activated antigen presenting cells and endothelial cells within acute inflammatory environments. We discuss here how ligation of OX40 by OX40L leads to enhanced T-cell survival, along with local inflammatory responses that appear critical for both effective T-cell mediated responses and chronic immune pathologies. We describe how interventions that block or mimic the OX40-OX40L interaction can be applied to treat autoimmune diseases or enhance anti-tumor immune responses. The clinically relevant properties of these agents emphasize the importance of this particular TNFSF-TNFSF in health and disease.

The TNF-family receptor DR3 is essential for diverse T cell-mediated inflammatory diseases

DR3 (TRAMP, LARD, WSL-1, TNFRSF25) is a death-domain-containing tumor necrosis factor (TNF)-family receptor primarily expressed on T cells. TL1A, the TNF-family ligand for DR3, can costimulate T cells, but the physiological function of TL1A-DR3 interactions in immune responses is not known. Using DR3-deficient mice, we identified DR3 as the receptor responsible for TL1A-induced T cell costimulation and dendritic cells as the likely source for TL1A during T cell activation. Despite its role in costimulation, DR3 was not required for in vivo T cell priming, for polarization into T helper 1 (Th1), Th2, or Th17 effector cell subtypes, or for effective control of infection with Toxoplasma gondii. Instead, DR3 expression was required on T cells for immunopathology, local T cell accumulation, and cytokine production in Experimental Autoimmune Encephalomyelitis (EAE) and allergic lung inflammation, disease models that depend on distinct effector T cell subsets. DR3 could be an attractive therapeutic target for T cell-mediated autoimmune and allergic diseases.