The human OX40 homolog: cDNA structure, expression and chromosomal assignment of the ACT35 antigen

OX40/OX40 ligand and its role in precision immune oncology

Immune checkpoint inhibitors have changed the treatment landscape for various malignancies; however, their benefit is limited to a subset of patients. The immune machinery includes both mediators of suppression/immune evasion, such as PD-1, PD-L1, CTLA-4, and LAG-3, all of which can be inhibited by specific antibodies, and immune-stimulatory molecules, such as T-cell co-stimulatory receptors that belong to the tumor necrosis factor receptor superfamily (TNFRSF), including OX40 receptor (CD134; TNFRSF4), 4-1BB (CD137; TNFRSF9), and glucocorticoid-induced TNFR-related (GITR) protein (CD357; TNFRSF18). In particular, OX40 and its binding ligand OX40L (CD134L; TNFSF4; CD252) are critical for immunoregulation. When OX40 on activated T cells binds OX40L on antigen-presenting cells, T-cell activation and immune stimulation are initiated via enhanced T-cell survival, proliferation and cytotoxicity, memory T-cell formation, and abrogation of regulatory T cell (Treg) immunosuppressive functions. OX40 agonists are in clinical trials both as monotherapy and in combination with other immunotherapy agents, in particular specific checkpoint inhibitors, for cancer treatment. To date, however, only a minority of patients respond. Transcriptomic profiling reveals that OX40 and OX40L expression vary between and within tumor types, and that only ~ 17% of cancer patients have high OX40 and low OX40L, one of the expression patterns that might be theoretically amenable to OX40 agonist enhancement. Taken together, the data suggest that the OX40/OX40L machinery is a critical part of the immune stimulatory system and that understanding endogenous expression patterns of these molecules and co-existing checkpoints merits further investigation in the context of a precision immunotherapy strategy for cancer therapy.

Boosting Antitumor Response by Costimulatory Strategies Driven to 4-1BB and OX40 T-cell Receptors

Immunotherapy explores several strategies to enhance the host immune system’s ability to detect and eliminate cancer cells. The use of antibodies that block immunological checkpoints, such as anti–programed death 1/programed death 1 ligand and cytotoxic T-lymphocyte–associated protein 4, is widely recognized to generate a long-lasting antitumor immune response in several types of cancer. Evidence indicates that the elimination of tumors by T cells is the key for tumor control. It is well known that costimulatory and coinhibitory pathways are critical regulators in the activation of T cells. Besides blocking checkpoints inhibitors, the agonistic signaling on costimulatory molecules also plays an important role in T-cell activation and antitumor response. Therefore, molecules driven to costimulatory pathways constitute promising targets in cancer therapy. The costimulation of tumor necrosis factor superfamily receptors on lymphocytes surface may transduce signals that control the survival, proliferation, differentiation, and effector functions of these immune cells. Among the members of the tumor necrosis factor receptor superfamily, there are 4-1BB and OX40. Several clinical studies have been carried out targeting these molecules, with agonist monoclonal antibodies, and preclinical studies exploring their ligands and other experimental approaches. In this review, we discuss functional aspects of 4-1BB and OX40 costimulation, as well as the progress of its application in immunotherapies.

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.

Genetic variations in autoimmune genes and VKH disease

PURPOSE

Vogt-Koyanagi-Harada (VKH) disease is a rare autoimmune disease. The autoimmune response in VKH disease is against the melanin-producing cells; therefore, in affected individuals melanocyte-containing organs manifest disease symptoms including eyes, ears, skin and nervous system. VKH is a multifactorial disease, and the precise cause of the VKH disease is unknown. Studies have suggested that both environmental and genetic factors are responsible for the VKH disease. In this review, the authors have collected all the available literature on the genetics of VKH to their knowledge and discussed the role of genetic variants in causing VKH disease.

METHODS

An extensive literature search was performed in order to review all the published studies regarding VKH clinical phenotyping and genetic variants in VKH disease. Medline, PubMed, Cochrane library, and Scopus was searched using combination of keywords.

RESULTS

It was found that variants in HLA genes, IL-12b, TNFSF4, and miR-20-5p genes are significantly associated with VKH; however, variants in genes ATG10, TNIP1 and CLEC16A did not achieve significant genome-wide association threshold. Moreover, polymorphisms in TNIP1 and CLEC16A play a protective role against VKH.

CONCLUSION

The authors conclude that increased sample size and a more homogeneous VKH patient population may reveal a significant association of variants in ATG10, TNIP1 and CLEC16A genes with VKH disease.

Kawasaki disease OX40-OX40L axis acts as an upstream regulator of NFAT signaling pathway

BACKGROUND

We investigated a costimulatory molecule OX40-OX40L acting as an upstream regulator to regulate the nuclear factor of activated T cell (NFAT) in the acute phase of Kawasaki disease (KD).

METHODS

One hundred and one samples were collected and divided into six groups: coronary artery lesion (KD-CAL) before intravenous immunoglobulin (IVIG), KD-CAL after IVIG, KD without CAL (KD-nCAL) before IVIG, KD-nCAL after IVIG, fever of unknown (Fou), and Healthy. In vitro OX40-stimulating and OX40L-inhibiting tests were conducted in Healthy and KD groups, respectively. Both the messenger RNA (mRNA) and protein expression levels of OX40, OX40L, NFAT1, and NFAT2 were investigated using quantitative reverse transcription PCR and immunoblotting assay, respectively.

RESULTS

The mRNA and protein expression levels of NFAT1, NFAT2, OX40, and OX40L were significantly increased in KD-CAL and KD-nCAL groups before IVIG compared with Fou and Healthy groups and decreased after IVIG. A positive correlation was found between them in KD. In vitro OX40-stimulating test demonstrated the significantly increased mRNA and protein expression levels of NFAT1 and NFAT2 in the peripheral blood mononuclear cells of the Healthy group. Meanwhile, OX40L-inhibiting test showed significantly decreased expression levels of NFAT1 and NFAT2 in the KD group.

CONCLUSION

OX40-OX40L acts as an upstream regulator in the NFAT signaling pathway involved in KD.

Characterisation of chicken OX40 and OX40L

The Tumour Necrosis Factor superfamilies of receptors and ligands play a crucial role in the regulation of effective immune responses against pathogens and malignant cells. In chickens, only few members have been identified. Here, we characterise the chicken homologues for mammalian costimulatory molecules OX40 and OX40L, which are involved in sustaining T cell responses. Both genes were identified by virtue of their genomic localisation close to highly conserved genes and their structural relationship to their mammalian homologues. Following cloning and expression of soluble and cell-associated chicken OX40 and OX40L, we confirmed their mutual interaction via ELISA and flow cytometric analyses. In addition, we showed the application of soluble OX40-Fc in staining of chicken cells. Whereas non-activated cells did not express OX40L, activation by IL-2 and IL-12 resulted in upregulation of OX40L on αβ and γδ T cell populations. Our results demonstrate the existence of the costimulatory OX40-OX40L system in the chicken and provide the basis for further investigations of chicken T cell responses.

Optimizing Tumor Microenvironment for Cancer Immunotherapy: β-Glucan-Based Nanoparticles

Immunotherapy is revolutionizing cancer treatment. Recent clinical success with immune checkpoint inhibitors, chimeric antigen receptor T-cell therapy, and adoptive immune cellular therapies has generated excitement and new hopes for patients and investigators. However, clinically efficacious responses to cancer immunotherapy occur only in a minority of patients. One reason is the tumor microenvironment (TME), which potently inhibits the generation and delivery of optimal antitumor immune responses. As our understanding of TME continues to grow, strategies are being developed to change the TME toward one that augments the emergence of strong antitumor immunity. These strategies include eliminating tumor bulk to provoke the release of tumor antigens, using adjuvants to enhance antigen-presenting cell function, and employ agents that enhance immune cell effector activity. This article reviews the development of β-glucan and β-glucan-based nanoparticles as immune modulators of TME, as well as their potential benefit and future therapeutic applications. Cell-wall β-glucans from natural sources including plant, fungi, and bacteria are molecules that adopt pathogen-associated molecular pattern (PAMP) known to target specific receptors on immune cell subsets. Emerging data suggest that the TME can be actively manipulated by β-glucans and their related nanoparticles. In this review, we discuss the mechanisms of conditioning TME using β-glucan and β-glucan-based nanoparticles, and how this strategy enables future design of optimal combination cancer immunotherapies.

Association of TNFSF4 Polymorphisms with Vogt-Koyanagi-Harada and Behcet's Disease in Han Chinese

To investigate whether single nucleotide polymorphisms (SNPs) of the Tumor Necrosis Factor Superfamily 4 (TNFSF4) gene are associated with Vogt–Koyanagi–Harada (VKH) and Behcet’s disease (BD) in a Chinese Han population. A two-stage case control study was carried out in 1331 VKH, 938 BD and 1752 healthy controls. Ten TNFSF4 SNPs, including rs1234314, rs1234315, rs2205960, rs704840, rs2795288, rs844654, rs12039904, rs10912580, rs844665, and rs844644, were genotyped using the PCR-restriction fragment length polymorphism method. Genotype and allele frequencies were analyzed between cases and healthy controls using the X² or Fisher’s exact test and p values were corrected for multiple comparisons. We observed a significantly increased frequency of the TT genotype of rs1234315 in BD patients (Pc = 1.44 × 10⁻⁵, OR = 1.734, 95% CI = 1.398–2.151). The frequency of the TT genotype of rs12039904 was significantly higher in patients with VKH disease as compared to controls (Pc = 4.62 × 10⁻⁵, OR = 1.959, 95% CI = 1.483–2.588). Analysis of clinical manifestations in VKH disease and BD did not show an association with the TNFSF4 gene polymorphisms. The study suggests that the TNFSF4 gene may be involved in the susceptibility to VKH disease and BD in Han Chinese.

Regulatory and activated effector T cells in chronic hepatitis C virus: Relation to autoimmunity

AIM

To investigate how Tregs are regulated in chronic hepatitis C virus (HCV) patients via assessment of Tregs markers (granzyme 2, CD69 and FoxP3), Teffs markers [TNFRSF4 (OX40), INFG] and CD4, CD25 genes.

METHODS

A prospective study was conducted on 120 subjects divided into 4 groups: Group I (n = 30) treatment naïve chronic HCV patients; Group II (n = 30) chronic HCV treated with Peg/Riba; Group III (n = 30) chronic HCV associated with non-organ specific autoantibody and Group IV (n = 30) healthy persons as a control group. Tregs and Teffs markers were assessed in peripheral blood mononuclear cells by quantitative real time reverse transcriptase-polymerase chain reaction.

RESULTS

Chronic HCV patients exhibited significant higher levels of both Teffs and Tregs in comparison to healthy control group. Tregs markers were significantly decreased in Peg/Riba treated HCV patients in comparison to treatment naïve HCV group. In HCV patients with antinuclear antibody (ANA) +ve, Tregs markers were significantly decreased in comparison to all other studied groups. Teffs markers were significantly elevated in all HCV groups in comparison to control and in HCV group with ANA +ve in comparison to treatment naïve HCV group.

CONCLUSION

Elevated Tregs cells in chronic HCV patients dampen both CD4+ and CD8+ autologous T cell immune response. Interferon-α and ribavirin therapy suppress proliferation of Tregs. More significant suppression of Tregs was observed in HCV patients with autoantibodies favoring pathological autoimmune response.

Immune checkpoint blockade as a potential therapeutic target in non-small cell lung cancer

INTRODUCTION

The recent emergence of immune checkpoint blockade therapy and the progression of immunobiology in cancer have spurred an increasing interest in the immunotherapy for advanced non-small cell lung cancer (NSCLC). Immune checkpoint inhibitors (ICIs), designed to directly target immune inhibitory molecules, have demonstrated efficacy in the treatment of patients with advanced NSCLC.

AREAS COVERED

In the present article, the authors summarize the mechanism, efficacy and safety of major ICIs for the treatment of advanced or metastatic NSCLC. Combinations of different ICIs or conventional therapy and/or targeted agents for NSCLC treatment in clinical trials are also updated. In addition, immune-related adverse events and the roles of inhibitory immune checkpoint molecules as potential biomarkers in the immune checkpoint blockade therapy for NSCLC are emphatically elucidated.

EXPERT OPINION

Immunotherapies targeting the immune checkpoint pathways have shown potential to generate durable responses and improve survival for NSCLC patients. Although the toxicity profile of this immunotherapy is manageable, immune-related adverse events and drug resistance may cause therapeutic failure. Therefore, a better understanding of the mechanisms underpinning its function and the potential side effects of ICIs, as well as the identification of predictive biomarkers for patient selection are essential.

Current status of immunotherapy

The successful use of immune checkpoint inhibitors has been big breakthrough in the development of cancer immunotherapy. Anti-CTLA-4 monoclonal antibody, ipilimumab, is the first-approved immune checkpoint inhibitor and has shown durable objective responses for advanced melanoma beyond the effect of dacarbazine. Anti-PD-1 monoclonal antibodies, nivolumab and pembrolizumab, are other immune checkpoint inhibitors that have demonstrated more effective results than conventional drugs in clinical trials for a variety of advanced solid tumors including melanoma, non-small cell lung carcinoma and renal carcinoma. These studies have indicated that the enhancement of anti-cancer immunity by controlling the immune suppressive environment in cancer tissues is an important issue for the development of cancer immune-therapy. Accordingly, in recent years, the enthusiasm for research of cancer immunology has shifted to studies regarding the formation of the immune suppressive environment, immune suppression mechanisms in cancer tissues and the molecules and cells involved in these pathways. Novel findings from these studies might lead to the development of cancer immunotherapy based on control of the immune suppressive environment.

Chance, genetics, and the heterogeneity of disease and pathogenesis in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a remarkably complex and heterogeneous systemic autoimmune disease. Disease complexity within individuals and heterogeneity among individuals, even genetically identical individuals, is driven by stochastic execution of a complex inherited program. Genome-wide association studies (GWAS) have progressively improved understanding of which genes are most critical to the potential for SLE and provided illuminating insight about the immune mechanisms that are engaged in SLE. What initiates expression of the genetic program to cause SLE within an individual and how that program is initiated remains poorly understood. If we extrapolate from all of the different experimental mouse models for SLE, we can begin to appreciate why SLE is so heterogeneous and consequently why prediction of disease outcome is so difficult. In this review, we critically evaluate extrinsic versus intrinsic cellular functions in the clearance and elimination of cellular debris and how dysfunction in that system may promote autoimmunity to nuclear antigens. We also examine several mouse models genetically prone to SLE either because of natural inheritance or inheritance of induced mutations to illustrate how different immune mechanisms may initiate autoimmunity and affect disease pathogenesis. Finally, we describe the heterogeneity of disease manifestations in SLE and discuss the mechanisms of disease pathogenesis with emphasis on glomerulonephritis. Particular attention is given to discussion of how anti-DNA autoantibody initiates experimental lupus nephritis (LN) in mice.

Natural OX40L expressed on human T cell leukemia virus type-I-immortalized T cell lines interferes with infection of activated peripheral blood mononuclear cells by CCR5-utilizing human immunodeficiency virus

BACKGROUND

OX40 ligand (OX40L) co-stimulates and differentiates T cells via ligation of OX40 that is transiently induced on T cells upon activation, resulting in prolonged T cell survival and enhanced cytokine production by T cells. This view has led to the targeting of OX40 as a strategy to boost antigen specific T cells in the context of vaccination. In addition, the ligation of OX40 has also been shown to inhibit infection by CCR5-utilizing (R5) but not CXCR4-utilizing (X4) human immunodeficiency virus type-1 (HIV-1) via enhancement of production of CCR5-binding β-chemokines. It was reasoned that human T cell leukemia virus type-I (HTLV-1) immortalized T cell lines that express high levels of OX40L could serve as an unique source of physiologically functional OX40L. The fact that HTLV-1+ T cell lines simultaneously also express high levels of OX40 suggested a potential limitation.

RESULTS

Results of our studies showed that HTLV-1+ T cell lines bound exogenous OX40 but not OX40L, indicating that HTLV-1+ T cell lines express an active form of OX40L but an inactive form of OX40. Anti-OX40 non-blocking monoclonal antibody (mAb), but not blocking mAb, stained HTLV-1+ T cell lines, suggesting that the OX40 might be saturated with endogenous OX40L. Functionality of the OX40L was confirmed by the fact that a paraformaldehyde (PFA)-fixed HTLV-1+ T cell lines inhibited the infection of autologous activated peripheral blood mononuclear cells (PBMCs) with R5 HIV-1 which was reversed by either anti-OX40L blocking mAb or a mixture of neutralizing mAbs against CCR5-binding β-chemokines.

CONCLUSIONS

Altogether, these results demonstrated that autologous T cell lines immortalized by HTLV-1 can be utilized as a conventional source of physiologically functional OX40L.

Association of TNFSF4 polymorphisms with systemic lupus erythematosus: a meta-analysis

INTRODUCTION

To more precisely estimate the association between the tumor necrosis factor ligand superfamily member 4 (TNFSF4) gene polymorphisms and systemic lupus erythematosus (SLE) risk, we surveyed studies on the association of the TNFSF4 rs2205960, rs1234315, rs844644, and rs844648 polymorphisms with SLE.

METHODS

A literature-based search was conducted to identify all relevant studies. A total of eight independent studies were identified and subsequently reviewed in the meta-analysis.

RESULTS

The meta-analysis showed an association between the TNFSF4 rs2205960 polymorphism and SLE in all subjects [ odds ratio (OR) 1.327, 95% confidence interval (CI) 1.227-1.436, P < 0.001]. In a subgroup analysis by ethnicity, a significantly increased risk for SLE was associated with TNFSF4 rs2205960 T allele among patients of European (OR 1.254, 95% CI 1.185-1.328, P < 0.001) and Asian ethnicity (OR 1.425, 95% CI 1.352-1.501, P < 0.001). The meta-analysis of the rs1234315 polymorphism revealed no association between SLE and the rs1234315 T allele in all subjects (OR 1.167, 95% CI 0.874-1.558, P = 0.296), but the results of the subgroup analysis revealed significant association in subjects of Asian ethnicity (OR 1.386, 95% CI 1.318-1.458, P < 0.001). No association was found between the rs844644 and rs844648 polymorphisms and SLE.

CONCLUSION

The results of our meta-analysis suggest that the TNFSF4 rs2205960 polymorphism may confer susceptibility to SLE in different populations and that the TNFSF4 rs1234315 polymorphism is associated with susceptibility to SLE in Asians.

Role of cytokines in systemic lupus erythematosus: recent progress from GWAS and sequencing

Systemic lupus erythematosus (SLE) is a complex autoimmune disorder, known to have a strong genetic component. Concordance between monozygotic twins is approximately 30-40%, which is 8-20 times higher than that of dizygotic twins. In the last decade, genome-wide approaches to understanding SLE have yielded many candidate genes, which are important to understanding the pathophysiology of the disease and potential targets for pharmaceutical intervention. In this paper, we focus on the role of cytokines and examine how genome-wide association studies, copy number variation studies, and next-generation sequencing are being employed to understand the etiology of SLE. Prominent genes identified by these approaches include BLK, FCγR3B, and TREX1. Our goal is to present a brief overview of genomic approaches to SLE and to introduce some of the key discussion points pertinent to the field.

[Association study between TNFSF4 and coronary heart disease]

Previous studies suggest that TNFSF4 is a susceptibility gene of atherosclerosis. But case-control association analysis in Swedish population and German population provided inconsistent, even opposite results. In order to explore the relationship between this gene and coronary heart disease (CHD) in Chinese Han population, we collected 498 cases and 509 controls from Qilu hospital of Shandong University and analyzed the association between five single-nucleotide polymorphisms (SNPs) (rs1234314, rs45454293, rs3850641, rs1234313, and rs3861950) of TNFSF4 and CHD. On the basis of using traditional statistical analysis methods based on single SNP and haplotypes, we introduced principal component score-based logistic regression analysis to deal with the data. The results suggested that in Armitage trend test, only rs3861950 was significant, when used the Bonferroni correction, and all of the five SNPs were not statistically significant. In the logistic regression analysis which adjusts the confounding factors, all of the five SNPs were not statistically significant. In haplotype analysis, the frequencies of six haplotypes were significantly different in cases and controls (CTAGT (P=0.0006), CTAAC (P=0.0123), CCAGT (P=0.0004), GTGGT (P=0.0329), GCGAC (P<0.0001), and GCAAC (P=0.0173)). In principal component score-based logistic regression analysis, the first principal component has statistical significance (P=0.0236). These results indicate that TNFSF4 is a susceptibility gene of CHD in Chinese Han population.

In vitro generated anti-tumor T lymphocytes exhibit distinct subsets mimicking in vivo antigen-experienced cells

The T-lymphocyte pool can be subdivided into naïve (Tn), effector memory (Tem), and central memory (Tcm) T cells. In this study, we characterized in vitro short-term cultured anti-tumor human T lymphocytes generated by lentiviral transduction with an anti-tumor antigen TCR vector. Within 2 weeks of in vitro culture, the cultured T cells showed a Tcm-like phenotype illustrated by a high percentage of CD62L and CD45RO cells. When the cells were sorted into populations that were CD45RO+/CD62L-(Tem), CD45RO+/CD62L+(Tcm), or CD45RO(low)/CD62L+(Tn) and co-cultured with antigen-matched tumor lines, the magnitude of cytokine release from these populations for IFNγ (Tn < Tcm < Tem) and IL-2 (Tn > Tcm > Tem) mimicked the types of immune cell responses observed in vivo. In comparing cell-mediated effector function, Tn were found to be deficient (relative to Tcm and Tem) in the ability to form conjugates with tumor cells and subsequent lytic activity. Moreover, analysis of the gene expression profiles of the in vitro cultured and sorted T-cell populations also demonstrated patterns consistent with their in vivo counterparts. When Tcm and Tem were tested for the ability to survive in vivo, Tcm displayed significantly increased engraftment and persistence in NOD/SCID/γc(-/-) mice. In general, a large percentage of in vitro generated anti-tumor T lymphocytes mimic a Tcm-like phenotype (based on phenotype, effector function, and increased persistence in vivo), which suggests that these Tcm-like cultured T cells may be optimal for adoptive immunotherapy.

A recombinant vesicular stomatitis virus encoding HIV-1 receptors and human OX40 ligand efficiently eliminates HIV-1-infected CD4-positive T cells expressing OX40

OX40 protein is highly expressed on activated CD4-positive T cells that are susceptible for human immunodeficiency virus type 1 (HIV-1) infection. To target and kill HIV-1-infected OX40(+) T cells, we used a recombinant vesicular stomatitis virus (rVSV) lacking its envelope glycoprotein (ΔG) and instead expressing HIV-1 receptors CD4/CXCR4 and OX40 ligand (OX40L). Expression of OX40L as well as HIV-1 receptors on the VSV particles led to specific infection of OX40(+) T cells, including primary cells, either acutely or chronically infected with X4 HIV-1. Consequently, the rVSV rapidly eliminated these infected cells and caused a marked reduction of HIV-1 viral load in culture. Inclusion of the OX40L gene in the VSV recombinant led to significantly better infection and HIV-1 elimination compared with an rVSVΔG expressing only HIV-1 receptors. A novel rVSVΔG encoding both HIV-1 receptors and OX40L has a potentially greater therapeutic value than an rVSVΔG expressing only HIV-1 receptors.

Control of immunity by the TNFR-related molecule OX40 (CD134)

TNFR/TNF superfamily members can control diverse aspects of immune function. Research over the past 10 years has shown that one of the most important and prominent interactions in this family is that between OX40 (CD134) and its partner OX40L (CD252). These molecules strongly regulate conventional CD4 and CD8 T cells, and more recent data are highlighting their ability to modulate NKT cell and NK cell function as well as to mediate cross-talk with professional antigen-presenting cells and diverse cell types such as mast cells, smooth muscle cells, and endothelial cells. Additionally, OX40-OX40L interactions alter the differentiation and activity of regulatory T cells. Blocking OX40L has produced strong therapeutic effects in multiple animal models of autoimmune and inflammatory disease, and, in line with a prospective clinical future, reagents that stimulate OX40 signaling are showing promise as adjuvants for vaccination as well as for treatment of cancer.

TRAF-mediated TNFR-family signaling

The tumor necrosis factor (TNF) superfamily consists of a wide variety of cell-bound and secreted proteins that regulate numerous cellular processes. In particular, TNF-family proteins regulate the proliferation and death of tumor cells, as well as activated immune cells. This overview discusses the mammalian TNF receptor-associated factors (TRAFs), of which TRAF1, 2, 3, 5, and 6 have been shown to interact directly or indirectly with members of the TNF receptor superfamily. Structural features of TRAF proteins are described along with a discussion of TRAF-interacting proteins and the signaling pathways activated by the TRAF proteins. Finally, we examine the phenotypes observed in TRAF-knockout mice.

The promise of 4-1BB (CD137)-mediated immunomodulation and the immunotherapy of cancer

The continuing efforts in biomedical research to develop new therapies for cancer are entering an exciting new phase. Research over the past two to three decades has yielded a much more detailed understanding of the complexities of the cellular and molecular interactions involved in the generation and regulation of immune responses. We are also gaining insights into the mechanisms by which tumors evade or escape immune recognition and by which they become resistant to various existing chemotherapeutic and/or radiotherapeutic strategies. A clear conclusion that can be drawn from these studies is that effective treatments of cancer will become much more multifaceted and will include immunotherapeutic approaches. The identification and molecular cloning of genes encoding the receptors and ligands that play crucial roles in the generation and regulation of immune responses provides exciting new opportunities to induce and enhance effective endogenous immune responses to cancer. In this regard, the genes that comprise the tumor necrosis factor and tumor necrosis factor receptor superfamilies show particular promise. One receptor:ligand pair (4-1BB/CD137 and 4-1BBL/CD137L) is emerging as a target with important potential in its ability to enhance the generation of effective tumor-specific immune responses in situ. The results of the studies cited in this review highlight the potentials of 4-1BB-mediated immunotherapy.

Enhancement of OX40-induced apoptosis by TNF coactivation in OX40-expressing T cell lines in vitro leading to decreased targets for HIV type 1 production

OX40, a member of the tumor necrosis factor receptor (TNF-R) superfamily, has been shown to play an important role in the survival of antigen-specific CD4(+) T cells. We have previously reported that stimulation of the OX40-expressing and HIV-1 chronically infected T cell line, ACH-2/OX40, with either OX40 ligand (OX40L)-expressing cells or with TNF resulted in the activation of HIV-1 followed by apoptotic cell death. In the present study we found that costimulation via OX40 and TNF-R in OX40-expressing HIV-1-infected T cell lines leads to a marked reduction of HIV-1 production associated with rapid cell death. Since HIV-1-negative OX40(+) T cell lines underwent rapid apoptotic cell death after OX40L and TNF stimulation, it was reasoned that the ACH-2/OX40 cell death was unlikely to be due to HIV-1 infection. Furthermore, we found that the OX40-mediated apoptosis of the CD4(+) T cell line, Molt-4/CCR5-OX40 (M/R5-OX40), required (1) signals mediated via the cytoplasmic tail of OX40, (2) activation of the caspase cascade, including caspase-8 and caspase-3, and (3) induction of endogenous TNF-alpha, but not of TNF-beta, FasL, or TNF-related apoptosis-inducing ligand (TRAIL), suggesting that this apoptosis occurred indirectly via the TNF/TNF-R system. Finally, a fraction of primary activated CD4(+) T cells, expressing high levels of OX40, underwent apoptosis, as revealed by annexin V staining, after cocultivation with OX40L(+) cells. These results suggest a new biological role of the OX40L/OX40 system in controlling the fate of activated CD4(+) T cells and of controlling HIV-1 infection in inflammatory environments.

Polymorphism at the TNF superfamily gene TNFSF4 confers susceptibility to systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multisystem complex autoimmune disease of uncertain etiology (OMIM 152700). Over recent years a genetic component to SLE susceptibility has been established. Recent successes with association studies in SLE have identified genes including IRF5 (refs. 4,5) and FCGR3B. Two tumor necrosis factor (TNF) superfamily members located within intervals showing genetic linkage with SLE are TNFSF4 (also known as OX40L; 1q25), which is expressed on activated antigen-presenting cells (APCs) and vascular endothelial cells, and also its unique receptor, TNFRSF4 (also known as OX40; 1p36), which is primarily expressed on activated CD4+ T cells. TNFSF4 produces a potent co-stimulatory signal for activated CD4+ T cells after engagement of TNFRSF4 (ref. 11). Using both a family-based and a case-control study design, we show that the upstream region of TNFSF4 contains a single risk haplotype for SLE, which is correlated with increased expression of both cell-surface TNFSF4 and the TNFSF4 transcript. We hypothesize that increased expression of TNFSF4 predisposes to SLE either by quantitatively augmenting T cell-APC interaction or by influencing the functional consequences of T cell activation via TNFRSF4.

Enhancement of the anti-leukemic activity of cytokine induced killer cells with an anti-CD19 chimeric receptor delivering a 4-1BB-ζ activating signal

OBJECTIVE

There is growing interest in the use of cytokine-induced killer (CIK) cells in cancer therapy. In this study, we sought to maximize the antileukemic activity of anti-CD19 receptor-modified CIK cells against B-lineage acute lymphoblastic leukemia (ALL).

MATERIALS AND METHODS

CIK cells were transduced with retroviral vectors carrying different types of anti-CD19 chimeric receptors: anti-CD19-zeta, anti-CD19-DAP10, anti-CD19-4-1BB-zeta, and anti-CD19-CD28-zeta. A truncated form of the receptor was used as a control. Transduced CIK cells were then analyzed for their cytotoxic activity against ALL cells and for their capability to proliferate and to release cytokines after ALL encounter.

RESULTS

CIK cells were efficiently transduced with all the anti-CD19 retroviral vectors. Anti-CD19 receptor expression conferred powerful killing activity against ALL cells. However, there were clear advantages when receptors containing the co-stimulatory molecules 4-1BB or CD28 were transduced. Such cells had significantly more potent cytotoxicity than cells expressing the anti-CD19-zeta or anti-CD19-DAP10. Moreover, the presence of 4-1BB or CD28 in the receptor increased the production of interleukin (IL)-2, tumor necrosis factor (TNF)-alpha, TNF-beta, IL-5, IL-6, and IL-8 elicited by coculture with ALL cells. Notably, anti-CD19-4-1BB-zeta CIK cells secreted particularly low levels of interleukin-10 and proliferated strongly after contact with ALL cells.

CONCLUSIONS

Anti-CD19 chimeric receptors delivering primary and costimulatory signals render CIK cells powerfully cytotoxic against ALL cells and induce secretion of immunostimulatory cytokines and proliferation. These results support the testing of genetically modified CIK cells in clinical trials.

Expression and function of the OX40/OX40L costimulatory pair during herpes stromal keratitis

Herpes stromal keratitis (HSK) is an immunopathological disease regulated by Th1 CD4 T cells, which require APC and costimulation within the infected cornea to mediate disease. Recent studies suggest the OX40:OX40 ligand (OX40L) interaction enhances effector cell cytokine secretion at inflammatory sites. OX40(+) cells were detected in HSV-1-infected mouse corneas as early as 3 days postinfection (dpi), prior to the onset of HSK, and their frequency increased through 15 dpi, when all mice exhibited severe HSK. OX40L(+) cells were first detected at 7 dpi, coincident with the initiation of HSK. It is interesting that the OX40L(+) cells did not coexpress MHC Class II or the dendritic cell (DC) marker CD11c. Our findings demonstrate rapid infiltration of activated (OX40(+)) CD4(+) T cells into HSV-1-infected corneas and expression of OX40L on MHC Class II-negative cells but surprisingly, not on MHC Class II(+) CD11c(+) DC, which are present in the infected corneas and required for HSK. Moreover, neither local nor systemic treatment of mice with a blocking antibody to OX40L or with a blocking fusion protein altered the course of HSK significantly, possibly as a result of a lack of OX40L expression on functional APC.

Effect of antibody to CD134 on perforin-mediated cytolysis in human peripheral blood mononuclear cells

CD134 (OX40) is a new member of the tumor necrosis factor receptor (TNFR) superfamily. The influence of CD134 on perforin-mediated cytolysis remains obscure. In this study, human peripheral blood mononuclear cells (PBMC) were induced with phytohemagglutinin (50 microg/mL), by using anti-CD134 blocking monoclonal antibody (MAb; 1, 5, and 10 microg/mL) for 6, 12, 24, and 48 h. Perforin-mediated cytolysis against human erythrocytes of PBMC was detected. The expression of perforin mRNA and protein was also measured by reverse transcription-polymerase chain reaction and flow cytometry. Our data showed that the perforin-mediated cytolysis of PBMC was downregulated by various concentrations of anti-CD134 blocking MAb for different times and reached a minimum at 24 h at any concentration. Anti-CD134 blocking MAb induced downregulation of perforin-mediated cytolysis of PBMC in a dose-dependent manner in the range of 1-5 microg/mL. Perforin- mediated cytolysis of PBMC reached a plateau when the concentration of anti-CD134 blocking MAb exceeded 5 microg/mL. Anti-CD134 blocking MAb also induced the inhibition of the expression of perforin protein and mRNA in PBMC. In conclusion, anti-CD134 blocking MAb inhibits perforin-mediated cytolysis of PBMC by, at least in some part, decreasing the production of preforin, which may be useful in treating several autoimmune diseases.

Function of tumor necrosis factor receptor family members on regulatory T-cells

Effector cells play a crucial role in the immune system of higher vertebrates in eliminating invading pathogens and transformed cells that could cause disease or death of the individual. To be effective and specific, immune responses have to distinguish between self and nonself. Mechanisms of central and peripheral tolerance have evolved to control effector cells that could respond to autoantigens. Regulatory T-cells (Treg cells) are critical modulators of effector cells in the periphery that suppress autoreactive T-cells but are also involved in modulating immune responses against invading pathogens. Identification of surface markers of Treg cells and the development of in vitro systems to study the suppressive function of Treg cells have revealed distinct phenotypic and functional subsets of Treg cells. Several tumor necrosis factor receptor (TNFR) family members have been shown to play a role in the development, homeostasis, and suppressor function of Treg cells. Recent findings suggest that TNFRs and other cell-surface molecules of Treg cells can be explored for therapeutic strategies targeting autoimmune disorders, cancer, and immune responses against pathogens.

Sequential CD134-CXCR4 interactions in feline immunodeficiency virus (FIV): soluble CD134 activates FIV Env for CXCR4-dependent entry and reveals a cryptic neutralization epitope

Recombinant soluble CD134 (sCD134) facilitated feline immunodeficiency virus (FIV) entry into CXCR4-positive, cell surface CD134-negative target cells. sCD134-activated entry was dose dependent and CXCR4 dependent. We used the sCD134 activation system to explore the neutralization by four anti-V3 monoclonal antibodies (MAbs). V3 MAbs weakly neutralized FIV infection using target cells expressing both CD134 and CXCR4 but potently inhibited sCD134-activated entry into target cells expressing CXCR4 alone. These findings provide direct evidence for a sequential interaction of FIV Env with CD134 and CXCR4 and reveal the presence of a cryptic epitope in V3 that is masked in the mature envelope oligomers.

Characterization and application of two novel monoclonal antibodies against human OX40: costimulation of T cells and expression on tumor as well as normal gland tissues

OX40, a membrane-bound molecule of the tumor-necrosis-factor-receptor superfamily, is a critical costimulatory receptor during the immune response. Here, we newly generated two specific mouse antihuman OX40 monoclonal antibodies (mAbs) (2G2 and 1F7), whose specificities are quite different from the available OX40 mAb (ACT35) by competition assay. It was also found that both mAbs could enhance the proliferation, activation and differentiation of T lymphocytes primed by anti-CD3 mAb. These results evidenced that both were functional antihuman OX40 mAbs. Furthermore, stained by 2G2 and 1F7, FCM and immunohistochemistry detected the constitutive expression of OX40 on tumor cell lines from epithelium, breast cancer and glioma tissues. Meanwhile, the non-tumor tissues (thyroid gland, stomach gland) were also found OX40 expression. These results suggested that OX40 is not only expressed in activated T cells, but also in some tumors as well as normal gland tissues. Such expression pattern indicated that OX40 may be a valuable surface antigen in unveiling its expression and function outside the immune system. Briefly, these novel antibodies may contribute to the evaluation of the mechanism of tumor metastasis and eventually shed light on further study of tumor immunotherapy and autoimmune diseases.

Bone marrow transplantation and approaches to avoid graft-versus-host disease (GVHD)

Haematopoietic stem cell transplantation (HSCT) offers promise for the treatment of haematological and immune disorders, solid tumours, and as a tolerance inducing regimen for organ transplantation. Allogeneic HSCTs engraftment requires immunosuppression and the anti-tumour effects are dependent upon the immune effector cells that are contained within or generated from the donor graft. However, significant toxicities currently limit its efficacy. These problems include: (i) graft-versus-host disease (GVHD) in which donor T cells attack the recipient resulting in multi-organ attack and morbidity, (ii) a profound period of immune deficiency following HSCT, and (iii) donor graft rejection. Currently available methods to prevent or treat GVHD with systemic immunosuppression can lead to impaired immune recovery, increased opportunistic infections, and higher relapse rates. This review will provide an overview of GVHD pathophysiology and discuss the roles of various cells, pathways, and factors in the GVHD generation process and in the preservation of graft-versus-tumour effects. Variables that need to be taken into consideration in attempting to extrapolate preclinical results to the clinical paradigm will be highlighted.

Structural mapping of CD134 residues critical for interaction with feline immunodeficiency virus

CD134 is a primary binding receptor for feline immunodeficiency virus (FIV), and with CXCR4 facilitates infection of CD4(+) T cells. Human CD134 fails to support FIV infection. To delineate the regions important for defining virus specificity of CD134, we exchanged domains between human and feline CD134. The binding site for FIV surface glycoprotein (SU) is located in domain 1, in a region distinct from the natural ligand (CD134L)-binding site. Mutagenesis showed that Asp60 and Asp62 are required for interaction with FIV, and modeling studies localized these two residues to the outer edge of domain 1. Substitutions S60D and N62D, in conjunction with H45S, R59G and V64K, imparted both FIV SU binding and receptor function to human CD134. Finally, we demonstrated that soluble CD134 facilitates infection of CD134(-) CXCR4(+) target cells in a manner analogous to CD4 augmentation of HIV infection.

Factors that increase the effective concentration of CXCR4 dictate feline immunodeficiency virus tropism and kinetics of replication

The surface glycoprotein (gp95) of the feline immunodeficiency virus (FIV) binds in a strain-specific manner to several cell surface molecules, including CXCR4, heparan sulfate proteoglycans (HSPGs), DC-SIGN, and a 43-kDa cell surface receptor on T cells recently identified as CD134 by M. Shimojima et al. (Science 303:1192-1195, 2004). CXCR4 is the entry receptor in all known cases, and the other molecules act as binding receptors to help facilitate infection. In this report, we confirm and extend the findings regarding CD134 as a primary receptor for FIV. In addition, we show that temperature critically influences the binding properties of FIV gp95 to CXCR4 and HSPGs. The data show that gp95 of the field strain FIV-PPR bound to CXCR4 at 22 degrees C, whereas binding was not detected at 4 degrees C. In contrast, binding of the laboratory adapted FIV-34TF10 gp95 was observed at either 4 degrees C or 22 degrees C, albeit at increased levels at the higher temperature. The level of CXCR4 increased after the temperature was switched from 4 to 22 degrees C, whereas the level of HSPGs decreased, resulting in higher binding of gp95 from both strains to CXCR4 and lower binding of gp95 of FIV-34TF10 to HSPGs (FIV-PPR gp95 does not bind to these molecules). The findings also show that HSPGs facilitate the CXCR4-mediated infectivity of CrFK and G355-5 cells by FIV-34TF10. These two nonlymphoid cell lines express very low levels of CXCR4 and are permissive to FIV-34TF10 but not to productive infection by FIV-PPR. However, overexpression of human CXCR4 in CrFK or G-355-5 cells resulted in extensive cell fusion and infection by FIV-PPR. Taken together, these findings indicate that factors that increase the effective concentration of CXCR4 enhance FIV infectivity and may involve (i) temperature or ligand-induced conformational changes in CXCR4 that enhance SU binding, (ii) coreceptor interactions with gp95 that either alter gp95 conformation to enhance CXCR4 binding and/or raise the localized concentration of receptor or ligand, or (iii) direct increase in CXCR4 concentration via overexpression.

Feline immunodeficiency virus targets activated CD4+ T cells by using CD134 as a binding receptor

The major surface glycoprotein of feline immunodeficiency virus (FIV) specifically binds to a 43-kDa glycoprotein expressed on the surface of a subset of T cells in peripheral blood mononuclear cells and IL-2-dependent T cell lines. Binding to this molecule, in conjunction with CXC chemokine receptor (CXCR) 4, is required for productive infection of these cells by primary isolates of FIV. Here, we demonstrate that the 43-kDa molecule is CD134, a receptor for FIV recently identified independently [Shimojima, M., et al. (2004) Science 303, 1192-1195]. Furthermore, we show that CD134 is specifically up-regulated on CD4+ T cells that have been activated by treatment with IL-2 and Con A. CD8+ T cells remained negative for CD134 expression regardless of the activation state. Binding of the FIV major surface glycoprotein on activated CD4+ T cells was observed through direct interaction with CD134 whereas, on activated CD8+ T cells, the binding was CD134-independent and mediated by CXCR4 and, to a lesser extent, heparan sulfate proteoglycans. However, this CD134-independent interaction was not sufficient to render CD8+ T cells permissive to FIV infection, as FIV replicated primarily in activated CD4+ T cells and not in cells negative for CD134 expression. Altogether, our results substantiate that CD134 acts as a primary binding receptor for FIV and explain the specific targeting and depletion of the CD4+ T cell population observed during the course of infection independent of the use of CD4 as a binding receptor/coreceptor.

Death receptor 3 (DR3) gene duplication in a chromosome region 1p36.3: gene duplication is more prevalent in rheumatoid arthritis

The death receptor 3 (DR3) gene is a member of the apoptosis-inducing Fas gene family. In the current study, fluorescence in situ hybridization (FISH) and Fiber-FISH revealed the existence of a second DR3 gene approximately 200 kb upstream of the original DR3 gene. The existence of the duplicated DR3 gene was confirmed by sequencing the corresponding human artificial chromosome clones as well as with quantitative PCR that measured the ratio of the DR3 gene mutation (Rm), intrinsic to rheumatoid arthritis (RA) patients, by simultaneous amplification of the normal and mutated DR3 sequences. The DR3 gene duplication measured by FISH was found to be more frequent in patients with RA as compared to healthy individuals. We therefore surmise that the human DR3 gene can be duplicated and that this gene duplication is more prevalent in patients with RA.

T-cell costimulatory pathways in allograft rejection and tolerance

The destiny of activated T cells is critical to the ultimate fate of immune response. After encountering antigen, naïve T cells receive signal 1 through the T-cell receptor (TCR)-major histocompatibility complex (MHC) plus antigenic peptide complex and signal 2 through "positive" costimulatory molecules leading to full activation. "Negative" T-cell costimulatory pathways, on the other hand, function to downregulate immune responses. The purpose of this article is to review the current state of knowledge and recent advances in our understanding of the functions of the positive and negative T-cell costimulatory pathways in alloimmune responses. Specifically, we discuss the functions of the CD28:B7 and the tumor necrosis factor receptor (TNFR):tumor necrosis factor (TNF) family of molecules in allograft rejection and tolerance. We address the following important questions: are T-cell costimulatory pathways merely redundant or do they provide distinct and unique functions? What are the important and unique interactions between the various pathways? And, what are the effects and mechanisms of targeting of these pathways in different types and patterns of allograft rejection and tolerance models?

Interaction of scavenger receptor class B type I with peroxisomal targeting receptor Pex5p

Scavenger receptor class B type I (SR-BI) is an HDL receptor that mediates selective HDL lipid uptake. Peroxisomes play an important role in lipid metabolism and peroxisomal targeting signal type 1 (PTS1)-containing proteins are translocated to peroxisomes by the peroxisomal targeting import receptor, Pex5p. We have previously identified a PTS1 motif in the intracellular domain of rat SR-BI. Here, we examine the possible interaction between Pex5p and SR-BI. Expression of a Flag-tagged intracellular domain of SR-BI resulted in translocation to the peroxisome as demonstrated by double labeling with anti-Flag IgG and anti-catalase IgG analyzed by confocal microscopy. Immunoprecipitation experiments with anti-SR-BI antibody showed that Pex5p co-precipitated with SR-BI. However, when an antibody against Pex5p was used for immunoprecipitation, only the 57kDa, non-glycosylated form, of SR-BI co-precipitated. We conclude that the PTS1 domain of SR-BI is functional and can mediate peroxisomal interaction via Pex5p, in vitro.

Activation of Resting Human Primary T Cells with Chimeric Receptors: Costimulation from CD28, Inducible Costimulator, CD134, and CD137 in Series with Signals from the TCRζ Chain

Chimeric receptors that include CD28 signaling in series with TCRzeta in the same receptor have been demonstrated to activate prestimulated human primary T cells more efficiently than a receptor providing TCRzeta signaling alone. We examined whether this type of receptor can also activate resting human primary T cells, and whether molecules other than CD28 could be included in a single chimeric receptor in series with TCRzeta to mediate the activation of resting human primary T cells. Human CD33-specific chimeric receptors were generated with CD28, inducible costimulator, CD134, or CD137 signaling regions in series with TCRzeta signaling region and transfected by electroporation into resting human primary T cells. Their ability to mediate Ag-specific activation was analyzed in comparison with a receptor providing TCRzeta signaling alone. Inclusion of any of the costimulatory signaling regions in series with TCRzeta enhanced the level of specific Ag-induced IL-2, IFN-gamma, TNF-alpha, and GM-CSF cytokine production and enabled resting primary T cells to survive and proliferate in response to Ag in the absence of any exogenous factors. Inclusion of CD28, inducible costimulator, or CD134 enhanced TCRzeta-mediated, Ag-specific target cell lysis. Chimeric receptors providing B7 and TNFR family costimulatory signals in series with TCRzeta in the same receptor can confer self-sufficient clonal expansion and enhanced effector function to resting human T cells. This type of chimeric receptor may now be used to discover the most potent combination of costimulatory signals that will improve current immunotherapeutic strategies.

The role of the CD134-CD134 ligand costimulatory pathway in alloimmune responses in vivo

The CD134-CD134 ligand (CD134L) costimulatory pathway has been shown to be critical for both T and B cell activation; however, its role in regulating the alloimmune response remains unexplored. Furthermore, its interactions with other costimulatory pathways and immunosuppressive agents are unclear. We investigated the effect of CD134-CD134L pathway blockade on allograft rejection in fully MHC-mismatched rat cardiac and skin transplantation models. CD134L blockade alone did not prolong graft survival compared with that of untreated recipients, and in combination with donor-specific transfusion, cyclosporine, or rapamycin, was less effective than B7 blockade in prolonging allograft survival. However, in combination with B7 blockade, long-term allograft survival was achieved in all recipients (>200 days). Moreover, this was synergistic in reducing the frequency of IFN-gamma-producing alloreactive lymphocytes and inhibiting the generation of activated/effector lymphocytes. Most impressively, this combination prevented rejection in a presensitized model using adoptive transfer of primed lymphocytes into athymic heart transplant recipients. In comparison to untreated recipients (mean survival time (MST): 5.3 +/- 0.5 days), anti-CD134L mAb alone modestly prolonged allograft survival (MST: 14 +/- 2.8 days) as did CTLA4Ig (MST: 21.5 +/- 1.7 days), but all grafts were rejected within 24 days. Importantly, combined blockade further and significantly prolonged allograft survival (MST: 75.3 +/- 12.7 days) and prevented the expansion and/or persistence of primed/effector alloreactive T cells. Our data suggest that CD134-CD134L is a critical pathway in alloimmune responses, especially recall/primed responses, and is synergistic with CD28-B7 in mediating T cell effector responses during allograft rejection. Understanding the mechanisms of collaboration between these different pathways is important for the development of novel strategies to promote long-term allograft survival.

Pimecrolimus inhibits up-regulation of OX40 and synthesis of inflammatory cytokines upon secondary T cell activation by allogeneic dendritic cells

Pimecrolimus is a new non-steroidal inhibitor of T cell and mast cell activation. In the present study, we compared the potency of pimecrolimus and cyclosporin A (CyA) to inhibit cytokine synthesis of alloantigen-primed T cells and the expression of CD134 (OX40), an inducible co-receptor molecule thought to be critical for the survival and expansion of inflammation-mediating T cells. To mimic the physiological situation of recurrent antigenic stimulation, we have used dendritic cells (DC) as stimulators of purified CD4+ T cells in the primary and secondary allogeneic mixed lymphocyte culture (allo-MLC). Pimecrolimus inhibited surface expression of OX40 and prevented the up-regulation of CD25 and CD54 with a 10-fold higher potency compared to CyA. Similarly, 50% inhibition of allo-DC-mediated T cell proliferation by pimecrolimus was obtained at 0.55 nm, compared to about 12 nm for CyA. Furthermore, pimecrolimus blocked the increase of OX40 on primed T cells restimulated on day 10 in secondary allo-MLC. Allo-DC-primed T cells showed a restricted cytokine profile characterized by the production of TNF-alpha, IFN-gamma and IL-2 but low to undetectable levels of IL-4 and IL-10. The synthesis of TNF-alpha and IFN-gamma and the up-regulation of OX40 on T cells after secondary allogeneic stimulation were almost entirely blocked by 10 nm pimecrolimus. Taken together, pimecrolimus inhibits T cell proliferation and Th1 cytokine synthesis and also prevents the up-regulation of the OX40 co-receptor on primed T cells indicating its potential in the therapy of chronic inflammation and autoimmunity.

OX40 signaling renders adult T-cell leukemia cells resistant to Fas-induced apoptosis

We reported previously that OX40, a member of the tumor necrosis factor receptor family, is expressed constitutively on fresh leukemia/lymphoma cells isolated from patients with adult T-cell leukemia (ATL). In this study, we tested whether OX40 signaling affects the Fas-mediated apoptosis of fresh ATL cells isolated from 7 patients (3 acute type, 3 chronic type, and 1 smoldering type). In all these patients, the coculture of ATL cells with MMCE/OX40 ligand gp34, a stable human gp34 transfectant of a mouse epithelial cell line, resulted in a decrease in the percentage of apoptotic cells after treatment with anti-Fas monoclonal antibody, compared to coculture with MMCE/mock controls. Similar findings were obtained in OX40(+)- human T-cell leukemia virus type I-transformed T-cell lines. To elucidate the molecular mechanism of this phenomenon, we used Kit225/OX40, a stable OX40 transfectant of an IL-2-dependent T-cell line, and its deletion mutant, Kit225/del-OX40, in which the intracytoplasmic domain of OX40 had been deleted. Coculture with MMCE/gp34 inhibited the apoptosis of Kit225/OX40, but Kit225/del-OX40 apoptosis was hardly affected. These results suggest that ATL cells may escape Fas-mediated destruction of the immune system through OX40 signaling.

Ox40 costimulation enhances the development of T cell responses induced by dendritic cells in vivo

Dendritic cells (DCs) are bone marrow-derived APCs that display unique properties aimed at stimulating naive T cells. Several members of the TNF/TNFR families have been implicated in T cell functions. In this study, we examined the role that Ox40 costimulation might play on the ability of DCs to regulate CD4(+) and CD8(+) T cell responses in vivo. Administration of anti-mouse Ox40 mAb enhanced the Th response induced by immunization with Ag-pulsed DCs, and introduced a bias toward a Th1 immune response. However, anti-Ox40 treatment enhanced the production of Th2 cytokines in IFN-gamma(-/-) mice after immunization with Ag-pulsed DCs, suggesting that the production of IFN-gamma during the immune response could interfere with the development of Th2 lymphocytes induced by DCs. Coadministration of anti-Ox40 with DCs during Ag rechallenge enhanced both Th1 and Th2 responses induced during a primary immunization with DCs, and did not reverse an existing Th2 response. This suggests that Ox40 costimulation amplifies an ongoing immune response, regardless of Th differentiation potential. In an OVA-TCR class II-restricted adoptive transfer system, anti-Ox40 treatment greatly enhanced the level of cytokine secretion per Ag-specific CD4(+) T cell induced by immunization with DCs. In an OVA-TCR class I-restricted adoptive transfer system, administration of anti-Ox40 strongly enhanced expansion, IFN-gamma secretion, and cytotoxic activity of Ag-specific CD8(+) T cells induced by immunization with DCs. Thus, by enhancing immune responses induced by DCs in vivo, the Ox40 pathway might be a target for immune intervention in therapeutic settings that use DCs as Ag-delivery vehicles.

OX40 stimulation by gp34/OX40 ligand enhances productive human immunodeficiency virus type 1 infection

OX40 is a member of the tumor necrosis factor (TNF) receptor superfamily and known to be an important costimulatory molecule expressed on activated T cells. To investigate the role of costimulation of OX40 in human immunodeficiency virus type 1 (HIV-1) infection by its natural ligand, gp34, the OX40-transfected ACH-2 cell line, ACH-2/OX40, chronically infected with HIV-1, was cocultured with paraformaldehyde (PFA)-fixed gp34-transfected mouse cell line, SV-T2/gp34. The results showed that HIV-1 production was strongly induced. This was followed by apparent apoptosis, and both processes were specifically inhibited by the gp34-specific neutralizing monoclonal antibody 5A8. Endogenous TNF alpha (TNF-alpha) and TNF-beta production were not involved in the enhanced HIV-1 production. Furthermore, enhanced HIV-1 transcription in gp34-stimulated ACH-2/OX40 cells was dependent on the kappa B site of the HIV-1 long terminal repeat, and the OX40-gp34 interaction activated NF-kappa B consisting of p50 and p65 subunits. When primary activated CD4(+) T cells acutely infected with HIV-1(NL4-3) (CXCR4-using T-cell-line-tropic) were cocultured with PFA-fixed gp34(+) human T-cell leukemia virus type 1-bearing MT-2 cells or SV-T2/gp34 cells, HIV-1 production was also markedly enhanced. The enhancement was again significantly inhibited by 5A8. The present study first shows that OX40-gp34 interaction stimulates HIV-1 expression and suggests that OX40 triggering by gp34 may play an important role in enhancing HIV-1 production in both acutely and latently infected CD4(+) T cells in vivo.

Expression of gp34 (OX40 ligand) and OX40 on human T cell clones

gp34, which we previously cloned, is a ligand of OX40 (CD134), a costimulatory molecule involved in T cell activation. To elucidate the role of human OX40 / OX40L interaction, we examined the expression of gp34 (OX40L) and OX40 in normal human hematopoietic cells by using flow cytometry. OX40 expression is observed on activated T cells, while OX40L is expressed in antigen-presenting cells. However, cytotoxic T lymphocyte (CTL) clones specific for Epstein-Barr virus (EBV)-transformed autologous lymphoblastic cell lines (LCLs) induced both OX40 and OX40L expression after antigen or T cell receptor (TCR) stimulation. This study suggests a possible function of OX40L / OX40, through T cell-T cell interaction, in the reactivation of memory T cells in an autocrine manner, with implications for the pathogenesis of viral infections and neoplasms.