OX40-OX40 ligand interaction through T cell-T cell contact contributes to CD4 T cell longevity

Blockade of OX40/OX40L signaling using anti-OX40L alleviates murine lupus nephritis

Genetic variants of the OX40 ligand (OX40L) locus are associated with the risk of systemic lupus erythematosus (SLE), it is unclear how the OX40L blockade delays the lupus phenotype. Therefore, we examined the effects of an anti-OX40L antibody in MRL/Lpr mice. Next, we investigated the effect of anti-OX40L on immunosuppression in keyhole limpet hemocyanin-immunized C57BL/6J mice. In vitro treatment of anti-OX40L in CD4+ T and B220+ B cells was used to explore the role of OX40L in the pathogenesis of SLE. Anti-OX40L alleviated murine lupus nephritis, accompanied by decreased production of anti-dsDNA and proteinuria, as well as lower frequencies of splenic T helper (Th) 1 and T-follicular helper cells (Tfh). In keyhole limpet hemocyanin-immunized mice, decreased levels of immunoglobulins and plasmablasts were observed in the anti-OX40L group. Anti-OX40L reduced the number and area of germinal centers. Compared with the control IgG group, anti-OX40L downregulated CD4+ T-cell differentiation into Th1 and Tfh cells and upregulated CD4+ T-cell differentiation into regulatory T cells in vitro. Furthermore, anti-OX40L inhibited toll-like receptor 7-mediated differentiation of antibody-secreting cells and antibody production through the regulation of the SPIB-BLIMP1-XBP1 axis in B cells. These results suggest that OX40L is a promising therapeutic target for SLE.

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

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

Engaging stimulatory immune checkpoint interactions in the tumour immune microenvironment of primary liver cancers - how to push the gas after having released the brake

Hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) are the first and second most common primary liver cancer (PLC). For decades, systemic therapies consisting of tyrosine kinase inhibitors (TKIs) or chemotherapy have formed the cornerstone of treating advanced-stage HCC and CCA, respectively. More recently, immunotherapy using immune checkpoint inhibition (ICI) has shown anti-tumour reactivity in some patients. The combination regimen of anti-PD-L1 and anti-VEGF antibodies has been approved as new first-line treatment of advanced-stage HCC. Furthermore, gemcibatine plus cisplatin (GEMCIS) with an anti-PD-L1 antibody is awaiting global approval for the treatment of advanced-stage CCA. As effective anti-tumour reactivity using ICI is achieved in a minor subset of both HCC and CCA patients only, alternative immune strategies to sensitise the tumour microenvironment of PLC are waited for. Here we discuss immune checkpoint stimulation (ICS) as additional tool to enhance anti-tumour reactivity. Up-to-date information on the clinical application of ICS in onco-immunology is provided. This review provides a rationale of the application of next-generation ICS either alone or in combination regimen to potentially enhance anti-tumour reactivity in PLC patients.

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.

YAP1 expression is associated with survival and immunosuppression in small cell lung cancer

Immunotherapy is considered a major breakthrough in the treatment of small cell lung cancer (SCLC), although its anti-tumor efficacy is limited. With a high degree of malignancy and high heterogeneity, SCLC is difficult to treat in the clinic. A new combination strategy is urgently needed to further improve the efficacy of immunotherapy in patients with SCLC. By immunofluorescence, 100 SCLC patients in a local cohort were classified into the SCLC-A (high ASCL1 expression; n = 36), SCLC-N (high NEUROD1 expression; n = 32), SCLC-P (high POU2F3 expression; n = 14), and SCLC-Y (high YAP1 expression; n = 18) subtypes. Each SCLC molecular subtype represented different prognoses, tumor microenvironment traits, and immunotherapy sensitivities. Analysis of both the local and public cohorts suggested that the SCLC-Y subtype exhibited the worst clinical outcome (p < 0.05) when compared with other subtypes. SCLC with high YAP1 expression was characterized by high PD-L1 expression, high stromal score, T-cell functional impairment, and a close relationship with immune-related pathways. YAP1 upregulated PD-L1 expression and suppressed T cell activation, thus leading to immune evasion. In in vitro experiments, blockade of YAP1 promoted cancer cell apoptosis, immune cell proliferation, T-cell activation, and cytotoxic T-cell infiltration, thus further potentiating the efficacy of immunotherapy in patients with the SCLC-Y subtype.

Activation priming and cytokine polyfunctionality modulate the enhanced functionality of low-affinity CD19 CAR T cells

We recently described a low-affinity second-generation CD19 chimeric antigen receptor (CAR) CAT that showed enhanced expansion, cytotoxicity, and antitumor efficacy compared with the high-affinity (FMC63-based) CAR used in tisagenlecleucel, in preclinical models. Furthermore, CAT demonstrated an excellent toxicity profile, enhanced in vivo expansion, and long-term persistence in a phase 1 clinical study. To understand the molecular mechanisms behind these properties of CAT CAR T cells, we performed a systematic in vitro characterization of the transcriptomic (RNA sequencing) and protein (cytometry by time of flight) changes occurring in T cells expressing low-affinity vs high-affinity CD19 CARs following stimulation with CD19-expressing cells. Our results show that CAT CAR T cells exhibit enhanced activation to CD19 stimulation and a distinct transcriptomic and protein profile, with increased activation and cytokine polyfunctionality compared with FMC63 CAR T cells. We demonstrate that the enhanced functionality of low-affinity CAT CAR T cells is a consequence of an antigen-dependent priming induced by residual CD19-expressing B cells present in the manufacture.

NFκB signaling in T cell memory

Memory T cells play an essential role in protecting against infectious diseases and cancer and contribute to autoimmunity and transplant rejection. Understanding how they are generated and maintained in the context of infection or vaccination holds promise to improve current immune-based therapies. At the beginning of any immune response, naïve T cells are activated and differentiate into cells with effector function capabilities. In the context of infection, most of these cells die once the pathogenic antigen has been cleared. Only a few of them persist and differentiate into memory T cells. These memory T cells are essential to host immunity because they are long-lived and can perform effector functions immediately upon re-infection. How a cell becomes a memory T cell and continues being one for months and even years past the initial infection is still not fully understood. Recent reviews have thoroughly discussed the transcriptional, epigenomic, and metabolic mechanisms that govern T cell memory differentiation. Yet much less is known of how signaling pathways that are common circuitries of multiple environmental signals regulate T cell outcome and, precisely, T cell memory. The function of the NFκB signaling system is perhaps best understood in innate cells. Recent findings suggest that NFκB signaling plays an essential and unique role in generating and maintaining CD8 T cell memory. This review aims to summarize these findings and discuss the remaining questions in the field.

Modeling and analyzing single-cell multimodal data with deep parametric inference

The proliferation of single-cell multimodal sequencing technologies has enabled us to understand cellular heterogeneity with multiple views, providing novel and actionable biological insights into the disease-driving mechanisms. Here, we propose a comprehensive end-to-end single-cell multimodal analysis framework named Deep Parametric Inference (DPI). DPI transforms single-cell multimodal data into a multimodal parameter space by inferring individual modal parameters. Analysis of cord blood mononuclear cells (CBMC) reveals that the multimodal parameter space can characterize the heterogeneity of cells more comprehensively than individual modalities. Furthermore, comparisons with the state-of-the-art methods on multiple datasets show that DPI has superior performance. Additionally, DPI can reference and query cell types without batch effects. As a result, DPI can successfully analyze the progression of COVID-19 disease in peripheral blood mononuclear cells (PBMC). Notably, we further propose a cell state vector field and analyze the transformation pattern of bone marrow cells (BMC) states. In conclusion, DPI is a powerful single-cell multimodal analysis framework that can provide new biological insights into biomedical researchers. The python packages, datasets and user-friendly manuals of DPI are freely available at https://github.com/studentiz/dpi.

Adenoviral delivery of soluble ovine OX40L or CD70 costimulatory molecules improves adaptive immune responses to a model antigen in sheep

The tumour necrosis factor superfamily OX40L and CD70 and their receptors are costimulatory signalling axes critical for adequate T and B cell activation in humans and mice. In this work we inoculated groups of sheep with human recombinant adenovirus type 5 (Ad) expressing Ovis aries (Oa)OX40L or OaCD70 or a control adenoviral vector to determine whether they could improve the immune response to the model antigen OVA. PBMCs and serum samples were obtained for analysis of the adaptive immune response to OVA at days 0, 15, 30 and 90 post-inoculation (pi). Recall responses to OVA were assessed at day 7 and 30 after the second antigen inoculation (pb) at day 90. Administration of these immunomodulatory molecules did not induce unspecific PBMC stimulation. While OaOX40L administration mainly increased TNF-α and IL-4 in PBMC at day 15 pi concomitantly with a slight increase in antibody titer and the number of IFN-γ producing cells, we detected greater effects on adaptive immunity after OaCD70 administration. AdOaCD70 inoculation improved antibody titers to OVA at days 30 and 90 pi, and increased anti-OVA-specific IgG-secreting B cell counts when compared to control. Moreover, higher IFN-γ production was detected on days 7 pi, 7 pb and 30 pb in PBMCs from this group. Phenotypic analysis of T cell activation showed an increase in effector CD8+ T cells (CD8+ CD62L- CD27-) at day 15 pi in AdOaCD70 group, concurrent with a decrease in early activated cells (CD8+ CD62L- CD27+). Moreover, recall anti-OVA CD8+ T cell responses were increased at 7 pb in the AdOaCD70 group. AdOaCD70 administration could therefore promote CD8+ T cell effector differentiation and long-term activity. In this work we characterized the in vivo adjuvant potential on the humoral and cellular immune response of OaOX40L and OaCD70 delivered by non-replicative adenovirus vectors using the model antigen OVA. We present data highlighting the potency of these molecules as veterinary vaccine adjuvant.

Current Clinical Trial Landscape of OX40 Agonists

PURPOSE OF REVIEW

Despite the efficacy of immune checkpoint blockade (ICB) immunotherapy, most cancer patients still develop progressive disease necessitating additional treatment options. One approach is ligation of the OX40 (CD134) costimulatory receptor which promotes T cell activation, effector function, and the generation of long-lived memory cells.

RECENT FINDINGS

Numerous preclinical studies have demonstrated that OX40 agonists alone or in combination with ICB (e.g., anti-PD-1, anti-PD-L1, and anti-CTLA-4) augment anti-tumor immunity. In this review, we discuss the impact of OX40 agonists on T cell function and the therapeutic potential of OX40 agonists alone or in conjunction with ICB for patients with advanced malignancies.

Clinical Significance of OX40 and OX40 Ligand in the Peripheral Blood of Patients with Myasthenia Gravis

Background

A previous study on thymomas in myasthenia gravis (MG) patients indicated that OX40 expression may be upregulated in thymic tissues adjacent to germinal centers (GCs) and thymomas, and OX40 may interact with OX40L in GCs to enhance anti-acetylcholine receptor antibody production. However, little is known about the clinical significance of the expression of OX40 and OX40L in the peripheral blood of patients with MG. We aimed to characterize the expression of membrane-bound and soluble OX40 and OX40L in the peripheral blood of patients with MG and to identify their clinical significance.

Methods

For membrane molecules, we collected peripheral blood (PB) from 39 MG patients at baseline, 22 patients in relapse, and 42 patients in remission, as well as from 36 healthy participants as controls. For soluble molecules, plasma from 37 MG patients at baseline, 34 patients in relapse, and 30 patients in remission, as well as plasma from 36 healthy controls (HC), was retrospectively collected from the sample bank of the First Hospital of Soochow University. The expression of membrane-bound OX40 and OX40L (mOX40 and mOX40L) by immune cells was measured using flow cytometry. Plasma levels of soluble OX40 and OX40L (sOX40 and sOX40L) were measured by ELISA.

Results

(1) The expression of OX40 on CD4+ T cells and that of OX40L on B cells and monocytes were significantly increased, and the levels of sOX40 were significantly decreased in MG patients at baseline compared with HC, while the expression of sOX40L was not significantly different between the two groups. (2) Dynamic observation of the molecules showed significantly higher expression of OX40 on CD4⁺ T cells and higher levels of sOX40 in MG patients in relapse than in MG patients at baseline and MG patients in remission. Furthermore, the expression levels of sOX40 were significantly elevated in MG patients in remission compared with MG patients at baseline, and the expression of sOX40L was significantly lower in MG patients in remission than in MG patients at baseline and MG patients in relapse. (3) Plasma levels of sOX40 and sOX40L were significantly decreased in 13 patients with relapsed MG after immunosuppressive treatment compared with those before treatment. (4) Correlation analysis showed that the expression of OX40 on CD4⁺ T cells in patients with relapsed MG was positively correlated with the concentration of acetylcholine receptor antibodies (AchR-Ab), whereas the expression of OX40L on CD19⁺ B cells and CD14⁺ monocytes was negatively correlated with disease duration. (5) Binary regression analysis showed that patients with high CD4⁺ OX40 expression and high sOX40L levels had an increased risk of relapse.

Conclusions

OX40 and OX40L are abnormally expressed in the peripheral blood of patients with MG and may be closely associated with disease status and treatment. The OX40/OX40L pathway may be involved in the immunopathological process of MG and may play a role mainly in the later stage of MG.

Immune Checkpoints OX40 and OX40L in Small-Cell Lung Cancer: Predict Prognosis and Modulate Immune Microenvironment

Background

OX40 and OX40 ligand (OX40L), as essential immune checkpoint (IC) modulators, are highly correlated with cancer immunity regulation as well as tumor microenvironment (TME). Immunotherapy showed outstanding advantages in small-cell lung cancer (SCLC) therapy. However, functions and clinical significance of OX40 and OX40L in SCLC were not clear yet.

Materials and Methods

SCLC samples of 143 patients were collected for immunohistochemistry (IHC) or whole-exome sequencing (WES). We comprehensively explored the expression and mutation of OX40/OX40L in SCLC, and systematically linked OX40/OX40L with TME.

Results

The expression of OX40/OX40L on tumor cells and tumor-infiltrating lymphocytes (TILs) was found in the IHC cohort and verified in other cohorts with SCLC tissues and cell lines. The results showed co-expression patterns among OX40/OX40L, other ICs, and T-cell markers. The WES data suggested that OX40/OX40L mutation is rare in SCLC (<5%). Patients with positive OX40 protein expression on TILs showed substantially higher recurrence-free survival than those with negative expression (p=0.009). The external dataset also indicated that high OX40/OX40L expression was correlated with better prognosis [overall survival: OX40, p<0.001; OX40L, p=0.019]. Importantly, activation of immunity and high infiltration of CD4(+) and CD8(+) T cells were observed in the high OX40/OX40L expression group.

Conclusions

Collectively, this work highlighted the significance of OX40 and OX40L in prognosis and TME cell infiltration characterization of SCLC. Evaluating the OX40/OX40L-expression levels of individual patients with SCLC might contribute to guiding more precise therapy.

Generation and characterization of a high-affinity chimeric anti-OX40 antibody with potent antitumor activity

OX40 is a costimulatory molecule that belongs to the tumor necrosis factor receptor (TNFR) superfamily. OX40 agonist-based combinations are emerging as promising candidates for novel cancer immunotherapy. Clinical trials have shown that OX40 agonist antibodies could lead to better results in cancer patients. Using a hybridoma platform and three different types of immunization strategies, namely recombinant protein, DNA, and overexpressing cells, we identified a chimeric anti-OX40 antibody (mAb035-hIgG1 from DNA immunization) that shows excellent binding specificity, and slightly stronger activation of human memory CD4⁺ T cells and similar potent antitumor activity compared with BMS 986178, an anti-OX40 antibody currently being evaluated for the treatment of solid tumors. This paper further systematically investigates the antigen-specific immune response, the number of binders, epitope bins, and functional activities of antibodies among different immunization strategies. Interestingly, we found that different immunization strategies affect the biological activity of monoclonal antibodies.

Inflammasomes in dendritic cells: Friend or foe?

Inflammasomes are cytosolic multiprotein complexes that crucially contribute to host defense against pathogens but are also involved in the pathogenesis of autoinflammatory diseases. Inflammasome formation leads to activation of effector caspases (caspase-1, 4, 5, or 11), the proteolytic maturation of IL-1β and IL-18 as well as cleavage of the pore-forming protein Gasdermin D. Dendritic cells are major regulators of immune responses as they bridge innate and adaptive immunity. We here summarize the current knowledge on inflammasome expression and formation in murine bone marrow-, human monocyte-derived as well as murine and human primary dendritic cells. Further, we discuss both, the beneficial and detrimental, involvement of inflammasome activation in dendritic cells in cancer, infections, and autoimmune diseases. As inflammasome activation is typically accompanied by Gasdermin d-mediated pyroptosis, which is an inflammatory form of programmed cell death, inflammasome formation in dendritic cells seems ill-advised. Therefore, we propose that hyperactivation, which is inflammasome activation without the induction of pyroptosis, may be a general model of inflammasome activation in dendritic cells to enhance Th1, Th17 as well as cytotoxic T cell responses.

Head-to-head study of oxelumab and adalimumab in a mouse model of ulcerative colitis based on NOD/Scid IL2Rγnull mice reconstituted with human peripheral blood mononuclear cells

This study's aim was to demonstrate that the combination of patient immune profiling and testing in a humanized mouse model of ulcerative colitis (UC) might lead to patient stratification for treatment with oxelumab. First, immunological profiles of UC patients and non-UC donors were analyzed for CD4⁺ T cells expressing OX40 (CD134; also known as TNFRSF4) and CD14⁺ monocytes expressing OX40L (CD252; also known as TNFSF4) by flow cytometric analysis. A significant difference was observed between the groups for CD14⁺ OX40L⁺ (UC: n=11, 85.44±21.17, mean±s.d.; non-UC: n=5, 30.7±34.92; P=0.02), whereas no significant difference was detected for CD4⁺ OX40⁺. CD14⁺ OX40L⁺ monocytes were correlated significantly with T helper 1 and 2 cells. Second, NOD/Scid IL2Rγ null mice were reconstituted with peripheral blood mononuclear cells from UC donors exhibiting elevated levels of OX40L, and the efficacy of oxelumab was compared with that of adalimumab. The clinical, colon and histological scores and the serum concentrations of IL-6, IL-1β and glutamic acid were assessed. Treatment with oxelumab or adalimumab resulted in significantly reduced clinical, colon and histological scores, reduced serum concentrations of IL-6 and reduced frequencies of splenic human effector memory T cells and switched B cells. Comparison of the efficacy of adalimumab and oxelumab by orthogonal partial least squares discrimination analysis revealed that oxelumab was slightly superior to adalimumab; however, elevated serum concentrations of glutamic acid suggested ongoing inflammation. These results suggest that oxelumab addresses the pro-inflammatory arm of inflammation while promoting the remodeling arm and that patients exhibiting elevated levels of OX40L might benefit from treatment with oxelumab.

Summary: The combination of patient profiling and testing in a NOD/Scid IL2Rγ^null mouse model of ulcerative colitis (UC) validates oxelumab as a potential therapeutic in UC.

Emerging immune checkpoint inhibitors for the treatment of head and neck cancers

Introduction: The benefits of immune checkpoint inhibitors (ICIs) in recurrent and/or metastatic (R/M) head and neck squamous cell carcinoma (HNSCC) have been demonstrated through multiple studies to improve overall survival (OS) with decreased side effects when compared to the standard of care (SOC) treatment regimens in place for decades, leading to the approval of two ICIs, nivolumab and pembrolizumab. There has been a subsequent influx in the development of novel immunotherapy agents for the treatment of HNSCC. Areas covered: Data for anti-programmed cell death protein 1 (PD-1)/programmed death ligand 1 (PD-L1) and anti-cytotoxic T-lymphocyte associated protein 4 (CTLA-4) antibodies in treatment of R/M HNSCC will be reviewed. Emerging immune checkpoint inhibitors as well as combined therapies in HNSCC will be discussed. The role of predictive biomarkers, HPV-status, PD-L1 expression, and challenges related to treating patients with ICIs will be summarized. Expert opinion: A shift toward ICIs as SOC for the treatment of R/M HNSCC will continue as emerging immune checkpoints and combination therapies are evaluated. Response rates are variable in this patient population underlying the importance of identifying predictive biomarkers to aid in patient selection for ICI treatment.

Extracellular vesicles produced by immunomodulatory cells harboring OX40 ligand and 4-1BB ligand enhance antitumor immunity

Genetically modified tumor cells harboring immunomodulators may be used as therapeutic vaccines to stimulate antitumor immunity. The therapeutic benefit of these tumor vaccines is extensively investigated and mechanisms by which they boost antitumor response may be further explored. Tumor cells are large secretors of extracellular vesicles (EVs). These EVs are able to vehiculate RNA and proteins to target cells, and engineered EVs also vehiculate recombinant proteins. In this study, we explore immunomodulatory properties of EVs derived from antitumor vaccines expressing the TNFSF ligands 4-1BBL and OX40L, modulating immune response mediated by immune cells and eliminating tumors. Our results suggest that the EVs secreted by genetically modified tumor cells harboring TNFSF ligands can induce T cell proliferation, inhibit the transcription factor FoxP3, associated with the maintenance of Treg phenotype, and enhance antitumor activity mediated by immune cells. The immunomodulatory extracellular vesicles have potential to be further engineered for developing new approaches for cancer therapy.

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

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

PGE2-HIF1α reciprocal induction regulates migration, phenotypic alteration and immunosuppressive capacity of macrophages in tumor microenvironment

BACKGROUND

Very little is known about the role inflammation and mechanism(s) that enables the tumor to evade host's anti-tumor immune function during very initial days of tumor establishment. Our study focuses on the immune response and local inflammation specially the pro-inflammatory and immune modifier components that are responsible for tumor-induced immune-suppression, tumor-associated macrophages (TAM) at tumor microenvironment in mouse model from very early to late phase of tumor progression.

METHODS

1 × 10⁵ Ascites tumor, EAC in Swiss albino or Sarcoma-180 (S-180) in Balb c mice strain were inoculated intra-peritonially and grouped into Control (0 day or no tumor), initial phase (3 day tumor), early (7 Day), Late (14 day) and terminal (21 day tumor) sets. T cell activity, tumor niche macrophage, inflammatory signatures were studied using Confocal microscopy, flowcytometry, ELISA, q-RT PCR and Western blot.

RESULTS

We observed increased T cell infiltration at a very early stage of tumorigenesis in the tumor site with elevated percentage of activated/memory T cells. But increased cellular death and functional suppression of tumor site T cells during final stages. We observed increased infiltration of TAMs with skewed M2 phenotype. Increased chemokine receptor expression could be noted on these TAMs. Using HIF-1α inhibitor and prostaglandin receptor antagonists we demonstrated crucial role of these factor in functional alteration in TAMs. HIF-1α inhibition and also by prostaglandin receptor inhibition reduced signature pro-inflammatory gene expression, migration of macrophages and T cell suppression capacity of TAMs. We also demonstrated that PGE2 can induce HIF-1α activation in relatively less hypoxic microenvironment during early stages of tumor.

CONCLUSION

Altogether, these findings strongly suggest link between prostaglandin mediated early HIF-1α activation and subsequent hypoxia induced HIF-1α activation that further enhances prostaglandin synthesis driving the recruitment and functional alteration of tumor site macrophages.

4-1BB costimulation promotes CAR T cell survival through noncanonical NF-κB signaling

Clinical response to chimeric antigen receptor (CAR) T cell therapy is correlated with CAR T cell persistence, especially for CAR T cells that target CD19⁺ hematologic malignancies. 4-1BB-costimulated CAR (BBζ) T cells exhibit longer persistence after adoptive transfer than do CD28-costimulated CAR (28ζ) T cells. 4-1BB signaling improves T cell persistence even in the context of 28ζ CAR activation, which indicates distinct prosurvival signals mediated by the 4-1BB cytoplasmic domain. To specifically study signal transduction by CARs, we developed a cell-free, ligand-based activation and ex vivo culture system for CD19-specific CAR T cells. We observed greater ex vivo survival and subsequent expansion of BBζ CAR T cells when compared to 28ζ CAR T cells. We showed that only BBζ CARs activated noncanonical nuclear factor κB (ncNF-κB) signaling in T cells basally and that the anti-CD19 BBζ CAR further enhanced ncNF-κB signaling after ligand engagement. Reducing ncNF-κB signaling reduced the expansion and survival of anti-CD19 BBζ T cells and was associated with a substantial increase in the abundance of the most pro-apoptotic isoforms of Bim. Although our findings do not exclude the importance of other signaling differences between BBζ and 28ζ CARs, they demonstrate the necessary and nonredundant role of ncNF-κB signaling in promoting the survival of BBζ CAR T cells, which likely underlies the engraftment persistence observed with this CAR design.

Recombinant Rabies Virus Overexpressing OX40-Ligand Enhances Humoral Immune Responses by Increasing T Follicular Helper Cells and Germinal Center B Cells

Rabies, caused by the rabies virus (RABV), remains a serious threat to public health in most countries. Development of a single-dose and efficacious rabies vaccine is the most important method to restrict rabies virus transmission. Costimulatory factor OX40-ligand (OX40L) plays a crucial role in the T cell-dependent humoral immune responses through T-B cell interaction. In this work, a recombinant RABV overexpressing mouse OX40L (LBNSE-OX40L) was constructed, and its effects on immunogenicity were evaluated in a mouse model. LBNSE-OX40L-immunized mice generated a larger number of T follicular helper (Tfh) cells, germinal center (GC) B cells, and plasma cells (PCs) than the parent virus LBNSE-immunized mice. Furthermore, LBNSE-OX40L induced significantly higher levels of virus-neutralizing antibodies (VNA) as early as seven days post immunization (dpi), which lasted for eight weeks, resulting in better protection for mice than LBNSE (a live-attenuated rabies vaccine strain). Taken together, our data in this study suggest that OX40L can be a novel and potential adjuvant to improve the induction of protective antibody responses post RABV immunization by triggering T cell-dependent humoral immune responses, and that LBNSE-OX40L can be developed as an efficacious and nonpathogenic vaccine for animals.

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

Background

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

Methods

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

Results

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

Conclusions

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

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.

TRAF5 promotes plasmacytoid dendritic cell development from bone marrow progenitors

The conventional dendritic cells (cDCs) and plasmacytoid DCs (pDCs) originate from the same common dendritic cell precursor cells in the bone marrow. The pDCs produce large amounts of type 1 interferon in response to foreign nucleic acid and crucially contribute to host defense against viral infection. Tumor necrosis factor (TNF) receptor-associated factor 5 (TRAF5) is a pivotal component of various TNF receptor signaling pathways in the immune system. Although the functions of TRAF5 in T and B lymphocytes have been well studied, its roles in pDCs remains to be fully elucidated. In this study, we show that the expression of TRAF5 supports the generation of pDCs in the bone marrow and also critically contributes to the homeostasis of the pDC subset in the periphery in a cell-intrinsic manner. Furthermore, we provide evidence that TRAF5 promotes the commitment of DC precursor cells toward pDC versus cDC subsets, which is regulated by the balance of transcription factors TCF4 and ID2. Together our findings reveal that TRAF5 acts as a positive regulator of pDC differentiation from bone marrow progenitors.

OX40 (CD134) and OX40 ligand, important immune checkpoints in cancer

Immunotherapy has shown promising results in cancer treatment. Research shows that most patients might be resistant to these therapies. So, new immune therapies are needed. OX40 (CD134) and OX40 ligand (OX40L), costimulatory molecules, express on different types of immune cells. The interaction between OX40 and OX40L (OX40/OX40L) induces the expansion and proliferation of T cells and decreases the immunosuppression of regulatory T (Treg) cells to enhance the immune response to the specific antigen. For the important role OX40 takes in the process of immunity, many clinical trials are focusing on OX40 to find out whether it may have active effects in clinical cancer treatment. The results of clinical trials are still not enough. So, we reviewed the OX40 and its ligand (OX40L) function in cancer, clinical trials with OX40/OX40L and the correlation between OX40/OX40L and other immune checkpoints to add more ideas to tumor feasible treatment.

Expansion of Human NK Cells Using K562 Cells Expressing OX40 Ligand and Short Exposure to IL-21

Background: Natural Killer (NK) cell-based immunotherapy used to treat cancer requires the adoptive transfer of a large number of activated NK cells. Here, we report a new effective method to expand human NK cells ex vivo using K562 cells genetically engineered (GE) to express OX40 ligand (K562-OX40L) in combination with a short exposure to soluble IL-21. In addition, we describe a possible mechanism of the NK cell expansion through the OX40 receptor-OX40 ligand axis which is dependent on NK cell homotypic interaction.

Methods: K562-OX40L cells were generated by lentiviral transduction and were used as feeder cells to expand and activate NK cells from PBMCs in the presence of IL-2/IL-15. Soluble IL-21 was also added in various concentrations only once at the beginning of the culture. NK cells were expanded for 4–5 weeks, and the purity, expansion rate, phenotype and function (cytotoxicity, antibody-dependent cell-mediated cytotoxicity (ADCC), cytokine production, CD107a degranulation) of these expanded NK cells were compared to those generated by using K562 feeder cells.

Results: The culture of NK cells with K562-OX40L cells in combination with the transient exposure to IL-21 highly enhanced NK cell expansion to approximately 2,000-fold after 4 weeks of culture, compared to a 303-fold expansion using the conventional K562 cells. Mechanistically, the OX40-OX40L axis between the feeder cells and NK cells as well as the homotypic interaction between NK cells through the OX40-OX40L axis were both necessary for NK cell expansion. The short exposure of NK cells to IL-21 had a synergistic effect with OX40 signaling for NK cell expansion. Apart from their enhanced expansion, NK cells grown with K562-OX40L feeder cells were similar to those grown with conventional K562 cells in regard to the surface expression of various receptors, cytotoxicity, ADCC, cytokine secretion, and CD107 degranulation.

Conclusion: Our data suggest that OX40 ligand is a potent co-stimulant for the robust expansion of human NK cells and the homotypic NK cell interactions through the OX40-OX40L axis is a mechanism of NK cell expansion.

Preparation, characterization and application of anti-human OX40 ligand (OX40L) monoclonal antibodies and establishment of a sandwich ELISA for autoimmune diseases detection

OX40L (CD252, TNFSF4), a type II transmembrane protein which like other tumor necrosis factor ligands, involved in the costimulation and differentiation of T cells, functions as a positive signal in immune response. To investigate the biological function of soluble OX40L (sOX40L), three functional anti-OX40L monoclonal antibodies (mAbs) 3D2, 3F7 and 2H3 were obtained by hybridoma technology. Besides, specificity of the mAbs was further demonstrated by ELISA, Western blot and Immunofluorescence experiments. We also developed a novel enzyme-linked immunosorbent assay (ELISA) based on two anti-human OX40L antibodies 3D2 and 3F7 with different epitopes. Using the ELISA system, we found that sOX40L in the sera of healthy donors increases in an age-dependent manner and that enhanced sOX40L expression in some autoimmune diseases especially in rheumatoid arthritis (RA) patients, suggesting the potential diagnostic significance of sOX40L in the autoimmune diseases. Together, these data demonstrate that the existence of circulating sOX40L in human sera might play an important role in immunoregulation.

Lymphoid tissue inducer-A divergent member of the ILC family

Innate lymphoid cells (ILCs) that are capable of producing effector cytokines reminiscent of CD4⁺ T helper (Th) cells during infections and tissue inflammations have drawn much attention in the immunology field in recent years. Within the ILCs, the lymphoid tissue inducer (LTi) cells that play a critical role in lymphoid organogenesis were identified long before the establishment of the ILC concept. LTi cells, developed and functioning mainly at the fetal stage, and LTi-like cells, presumably generated during the adulthood, are regarded as a subset of type 3 ILCs (ILC3s) because they express the ILC3 lineage-defining transcription factor RORγt, and like other ILC3s, can produce an ILC3 signature cytokine IL-22 and initiate protective immune responses against extracellular bacteria. However, LTi/LTi-like cells have a unique gene expression pattern, and they develop from a progenitor that is distinct from the progenitor of all other ILCs and the progenitor of conventional natural killer (cNK) cells. There are also several other unique features of LTi/LTi-like cells comparing to non-LTi ILC3s. In addition to their classical function in lymphoid organogenesis, LTi/LTi-like cells also have specialized functions in association with the adaptive immune system, which include their effects on T and B cell development, activation and function. In this review, we summarize these specific features of LTi/LTi-like cells and propose that these cells should be considered as a separated innate lymphoid lineage in parallel with other non-LTi ILCs and cNK cells.

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

Objectives

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

Methods

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

Results

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

Conclusions

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

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.

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.

Cytokine-Independent Detection of Antigen-Specific Germinal Center T Follicular Helper Cells in Immunized Nonhuman Primates Using a Live Cell Activation-Induced Marker Technique

A range of current candidate AIDS vaccine regimens are focused on generating protective HIV-neutralizing Ab responses. Many of these efforts rely on the rhesus macaque animal model. Understanding how protective Ab responses develop and how to increase their efficacy are both major knowledge gaps. Germinal centers (GCs) are the engines of Ab affinity maturation. GC T follicular helper (Tfh) CD4 T cells are required for GCs. Studying vaccine-specific GC Tfh cells after protein immunizations has been challenging, as Ag-specific GC Tfh cells are difficult to identify by conventional intracellular cytokine staining. Cytokine production by GC Tfh cells may be intrinsically limited in comparison with other Th effector cells, as the biological role of a GC Tfh cell is to provide help to individual B cells within the GC, rather than secreting large amounts of cytokines bathing a tissue. To test this idea, we developed a cytokine-independent method to identify Ag-specific GC Tfh cells. RNA sequencing was performed using TCR-stimulated GC Tfh cells to identify candidate markers. Validation experiments determined CD25 (IL-2Rα) and OX40 to be highly upregulated activation-induced markers (AIM) on the surface of GC Tfh cells after stimulation. In comparison with intracellular cytokine staining, the AIM assay identified >10-fold more Ag-specific GC Tfh cells in HIV Env protein-immunized macaques (BG505 SOSIP). CD4 T cells in blood were also studied. In summary, AIM demonstrates that Ag-specific GC Tfh cells are intrinsically stingy producers of cytokines, which is likely an essential part of their biological function.

The New Era of Cancer Immunotherapy: Manipulating T-Cell Activity to Overcome Malignancy

Using the immune system to control cancer has been investigated for over a century. Yet it is only over the last several years that therapeutic agents acting directly on the immune system have demonstrated improved overall survival for cancer patients in phase III clinical trials. Furthermore, it appears that some patients treated with such agents have been cured of metastatic cancer. This has led to increased interest and acceleration in the rate of progress in cancer immunotherapy. Most of the current immunotherapeutic success in cancer treatment is based on the use of immune-modulating antibodies targeting critical checkpoints (CTLA-4 and PD-1/PD-L1). Several other immune-modulating molecules targeting inhibitory or stimulatory pathways are being developed. The combined use of these medicines is the subject of intense investigation and holds important promise. Combination regimens include those that incorporate targeted therapies that act on growth signaling pathways, as well as standard chemotherapy and radiation therapy. In fact, these standard therapies have intrinsic immune-modulating properties that can support antitumor immunity. In the years ahead, adoptive T-cell therapy will also be an important part of treatment for some cancer patients. Other areas which are regaining interest are the use of oncolytic viruses that immunize patients against their own tumors and the use of vaccines against tumor antigens. Immunotherapy has demonstrated unprecedented durability in controlling multiple types of cancer and we expect its use to continue expanding rapidly.

Soluble OX40L is associated with presence of autoantibodies in early rheumatoid arthritis

Introduction

OX40 and its ligand OX40L are key components in the generation of adaptive memory response and provide necessary co-stimulatory signals for activated effector T cells. Here we investigate the dual roles of the membrane and soluble (s) forms of OX40 and OX40L in plasma and synovial fluid and their association with autoantibodies and disease activity in rheumatoid arthritis (RA).

Methods

Soluble OX40 and sOX40L plasma levels were measured in treatment-naïve early RA patients (eRA) at baseline and after 3, 6, and 12 months of treatment with methotrexate and adalimumab (n = 39) and with methotrexate alone (n = 37). Adalimumab was discontinued after the first year, and patients were followed for additional 12 months. For comparison, sOX40 and sOX40L were measured in patients with chronic RA (cRA, n = 15) and healthy volunteers (HV, n = 34). Membrane-bound OX40 and OX40L expression on T cells, B cells and monocytes were quantified.

Results

Soluble OX40 plasma levels of eRA patients were not different at the time of treatment initiation, but were significantly higher after 12 months of treatment, compared with HV or cRA patients. Soluble OX40L was significantly elevated throughout the first 12 months of treatment compared with HVs and patients with cRA. Adalimumab treatment did not influence sOX40 or sOX40L plasma levels. At baseline, sOX40L levels were strongly associated with the presence of anti-citrullinated protein antibodies (ACPA) (P <0.001) and IgM-RF (P <0.0001). The sOX40/sOX40L ratio was decreased in eRA, and a low ratio at the time of adalimumab discontinuation was associated with increased DAS28CRP and risk of flare the following year. T cells in the synovial fluid had the highest expression of OX40, while monocytes and B cells were the main expressers of OX40L in the joint.

Conclusions

Plasma levels of sOX40 and sOX40L were increased in eRA and sOX40L was correlated with ACPA and IgM-RF. Further, expression of membrane-bound OX40 and OX40L was increased in eRA and cRA. Combined, these findings could reflect that increased activity in the OX40 systems facilitate to drive disease activity and autoantibody production in RA.

Trial registration

Clincaltrials.gov NCT00660647, 10 April 2008.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-014-0474-4) contains supplementary material, which is available to authorized users.

T cells and costimulation in cancer

Optimal T cell response is dependent not only on T cell receptor activation, but also on additional signaling from coreceptors. The main coreceptors include B7 and tumor necrosis factor family members. They exert costimulatory or coinhibitory effects, and their balance determines the fate of T cell response. In normal conditions, costimulators facilitate the development of protective immune response, whereas coinhibitors dampen inflammation to avoid organ/tissue damage from excessive immune reaction. In the tumor microenvironment, the balance is garbled: inhibitory pathways predominate, and T cell response is impaired. The importance of cosignaling in the tumor immune response has been experimentally and clinically demonstrated. New therapeutic strategies targeting T cell cosignaling, especially coinhibitory molecules, are under active experimental and clinical investigation. This review summarizes the functions of main T cell cosignaling axes and discusses their clinical application.

The number of responding CD4 T cells and the dose of antigen conjointly determine the TH1/TH2 phenotype by modulating B7/CD28 interactions

Our previous in vivo studies show that both the amount of Ag and the number of available naive CD4 T cells affect the Th1/Th2 phenotype of the effector CD4 T cells generated. We examined how the number of OVA-specific CD4 TCR transgenic T cells affects the Th1/Th2 phenotype of anti-SRBC CD4 T cells generated in vivo upon immunization with different amounts of OVA-SRBC. Our observations show that a greater number of Ag-dependent CD4 T cell interactions are required to generate Th2 than Th1 cells. We established an in vitro system that recapitulates our main in vivo findings to more readily analyze the underlying mechanism. The in vitro generation of Th2 cells depends, as in vivo, upon both the number of responding CD4 T cells and the amount of Ag. We demonstrate, using agonostic/antagonistic Abs to various costimulatory molecules or their receptors, that the greater number of CD4 T cell interactions, required to generate Th2 over Th1 cells, does not involve CD40, OX40, or ICOS costimulation, but does involve B7/CD28 interactions. A comparison of the level of expression of B7 molecules by APC and CD4 T cells, under different conditions resulting in the substantial generation of Th1 and Th2 cells, leads us to propose that the critical CD28/B7 interactions, required to generate Th2 cells, may directly occur between CD4 T cells engaged with the same B cell acting as an APC.

The virus-receptor interaction in the replication of feline immunodeficiency virus (FIV)

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Expression of viral receptor CD134 is consistent with FIV cell tropism.

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Differential usage of CD134 by individual strains of FIV defined by requirement for CRD2 of CD134.

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CRD2-dependent strains dominate in early infection.

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CRD2-independent strains emerge in late infection.

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Selective expansion of CRD2-dependent variants following experimental transmission.

The feline and human immunodeficiency viruses (FIV and HIV) target helper T cells selectively, and in doing so they induce a profound immune dysfunction. The primary determinant of HIV cell tropism is the expression pattern of the primary viral receptor CD4 and co-receptor(s), such as CXCR4 and CCR5. FIV employs a distinct strategy to target helper T cells; a high affinity interaction with CD134 (OX40) is followed by binding of the virus to its sole co-receptor, CXCR4. Recent studies have demonstrated that the way in which FIV interacts with its primary receptor, CD134, alters as infection progresses, changing the cell tropism of the virus. This review examines the contribution of the virus–receptor interaction to replication in vivo as well as the significance of these findings to the development of vaccines and therapeutics.

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

Dendritic cells (DCs) are central in maintaining the intricate balance between immunity and tolerance by orchestrating adaptive immune responses. Being the most potent antigen presenting cells, DCs are capable of educating naïve T cells into a wide variety of effector cells ranging from immunogenic CD4⁺ T helper cells and cytotoxic CD8⁺ T cells to tolerogenic regulatory T cells. This education is based on three fundamental signals. Signal I, which is mediated by antigen/major histocompatibility complexes binding to antigen-specific T cell receptors, guarantees antigen specificity. The co-stimulatory signal II, mediated by B7 family molecules, is crucial for the expansion of the antigen-specific T cells. The final step is T cell polarization by signal III, which is conveyed by DC-derived cytokines and determines the effector functions of the emerging T cell. Although co-stimulation is widely recognized to result from the engagement of T cell-derived CD28 with DC-expressed B7 molecules (CD80/CD86), other co-stimulatory pathways have been identified. These pathways can be divided into two groups based on their impact on primed T cells. Whereas pathways delivering activatory signals to T cells are termed co-stimulatory pathways, pathways delivering tolerogenic signals to T cells are termed co-inhibitory pathways. In this review, we discuss how the nature of DC-derived signal II determines the quality of ensuing T cell responses and eventually promoting either immunity or tolerance. A thorough understanding of this process is instrumental in determining the underlying mechanism of disorders demonstrating distorted immunity/tolerance balance, and would help innovating new therapeutic approaches for such disorders.

OX40 ligand expression abrogates the immunosuppressive function of retinal pigment epithelium

Background

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

Results

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

Conclusions

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

SOX40L: An Important Inflammatory Mediator in Adult Bronchial Asthma

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

Runx1 deficiency in CD4+ T cells causes fatal autoimmune inflammatory lung disease due to spontaneous hyperactivation of cells

The Runx1 transcription factor is abundantly expressed in naive T cells but rapidly downregulated in activated T cells, suggesting that it plays an important role in a naive stage. In the current study, Runx1(-/-)Bcl2(tg) mice harboring Runx1-deleted CD4(+) T cells developed a fatal autoimmune lung disease. CD4(+) T cells from these mice were spontaneously activated, preferentially homed to the lung, and expressed various cytokines, including IL-17 and IL-21. Among these, the deregulation of IL-21 transcription was likely to be associated with Runx binding sites located in an IL-21 intron. IL-17 produced in Runx1-deleted cells mobilized innate immune responses, such as those promoted by neutrophils and monocytes, whereas IL-21 triggered humoral responses, such as plasma cells. Thus, at an initial stage, peribronchovascular regions in the lung were infiltrated by CD4(+) lymphocytes, whereas at a terminal stage, interstitial regions were massively occupied by immune cells, and alveolar spaces were filled with granular exudates that resembled pulmonary alveolar proteinosis in humans. Mice suffered from respiratory failure, as well as systemic inflammatory responses. Our data indicate that Runx1 plays an essential role in repressing the transcription of cytokine genes in naive CD4(+) T cells and, thereby, maintains cell quiescence.

Direct demonstration of CD4 T cell cooperation in the primary in vivo generation of CD4 effector T cells

Many observations bear upon the cellular and molecular requirements for CD4 T cell activation. The interaction of CD4 T cells with dendritic cells (DC), central to the induction of most immune responses, is the most studied. However, leukocytes other than DC can dramatically affect the induction and differentiation of CD4 T cells into effector cells. We recently provided indirect evidence that in vivo CD4 T cooperation facilitates the activation of CD4 T cells. Here, we demonstrate that the activation of CD4 T cells, specific for the hen egg lysozyme (HEL)(105) (-120) peptide, is optimally achieved when BALB/c mice are immunized with additional MHC class II-binding HEL peptides in incomplete Freund's adjuvant. This cooperation cannot be mimicked by the coadministration of LPS or of an agonistic antibody to CD40, at the time of immunization. In contrast, OX40-OX40L interactions are necessary for CD4 T cell cooperation in that an OX40 agonistic antibody can replace, and an OX40L-blocking antibody can abrogate, CD4 T cell cooperation in situations where such cooperation would otherwise enhance the activation of CD4 T cells.

TSLP and immune homeostasis

In an immune system, dendritic cells (DCs) are professional antigen-presenting cells (APCs) as well as powerful sensors of danger signals. When DCs receive signals from infection and tissue stress, they immediately activate and instruct the initiation of appropriate immune responses to T cells. However, it has remained unclear how the tissue microenvironment in a steady state shapes the function of DCs. Recent many works on thymic stromal lymphopoietin (TSLP), an epithelial cell-derived cytokine that has the strong ability to activate DCs, provide evidence that TSLP mediates crosstalk between epithelial cells and DCs, involving in DC-mediated immune homeostasis. Here, we review recent progress made on how TSLP expressed within the thymus and peripheral lymphoid and non-lymphoid tissues regulates DC-mediated T-cell development in the thymus and T-cell homeostasis in the periphery.

Synergistic CD40 signaling on APCs and CD8 T cells drives efficient CD8 response and memory differentiation

The role of CD4 help during CD8 response and memory differentiation has been clearly demonstrated in different experimental models. However, the exact mechanisms of CD4 help remain largely unknown and preclude replacement therapy to develop. Interestingly, studies have shown that administration of an agonist aCD40ab can substitute CD4 help in vitro and in vivo, whereas the targets of this antibody remain elusive. In this study, we address the exact role of CD40 expression on APCs and CD8 T cells using aCD40ab treatment in mice. We demonstrate that aCD40 antibodies have synergetic effects on APCs and CD8 T cells. Full efficiency of aCD40 treatment requires CD40 expression on both populations: if one of these cell populations is CD40-deficient, the CD8 T cell response is impaired. Most importantly, direct CD40 signaling on APCs and CD8 T cells affects CD8 T cell differentiation differently. In our model, CD40 expression on APCs plays an important but dispensable role on CD8 T cell expansion and effector functions during the early phase of the immune response. Conversely, CD40 on CD8 T cells is crucial and nonredundant for their progressive differentiation into memory cells. Altogether, these results highlight that CD40-CD40L-dependent and independent effects of CD4 help to drive a complete CD8 T cell differentiation.