OX40 (CD134) engagement drives differentiationof CD4+ T cells to effector cells

SARS-CoV-2 antigen-carrying extracellular vesicles activate T cell responses in a human immunogenicity model

Extracellular vesicles (EVs) are entering the clinical arena as novel biologics for infectious diseases, potentially serving as the immunogenic components of next generation vaccines. However, relevant human assays to evaluate the immunogenicity of EVs carrying viral antigens are lacking, contributing to challenges in translating rodent studies to human clinical trials. Here, we engineered EVs to carry SARS-CoV-2 Spike to evaluate the immunogenicity of antigen-carrying EVs using human peripheral blood mononuclear cells (PBMCs). Delivery of Spike EVs to PBMCs resulted in specific immune cell activation as assessed through T cell activation marker expression. Further, Spike EVs were taken up largely by antigen-presenting cells (monocytes, dendritic cells and B cells). Taken together, this human PBMC-based system models physiologically relevant pathways of antigen delivery, uptake and presentation. In summary, the current study highlights the suitability of using human PBMCs for evaluating the immunogenicity of EVs engineered to carry antigens for infectious disease therapeutics.

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

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

Neuropilin-1 identifies a subset of highly activated CD8+ T cells during parasitic and viral infections

Neuropilin-1 (Nrp-1) expression on CD8+ T cells has been identified in tumor-infiltrating lymphocytes and in persistent murine gamma-herpes virus infections, where it interferes with the development of long-lived memory T cell responses. In parasitic and acute viral infections, the role of Nrp-1 expression on CD8+ T cells remains unclear. Here, we demonstrate a strong induction of Nrp-1 expression on CD8+ T cells in Plasmodium berghei ANKA (PbA)-infected mice that correlated with neurological deficits of experimental cerebral malaria (ECM). Likewise, the frequency of Nrp-1+CD8+ T cells was significantly elevated and correlated with liver damage in the acute phase of lymphocytic choriomeningitis virus (LCMV) infection. Transcriptomic and flow cytometric analyses revealed a highly activated phenotype of Nrp-1+CD8+ T cells from infected mice. Correspondingly, in vitro experiments showed rapid induction of Nrp-1 expression on CD8+ T cells after stimulation in conjunction with increased expression of activation-associated molecules. Strikingly, T cell-specific Nrp-1 ablation resulted in reduced numbers of activated T cells in the brain of PbA-infected mice as well as in spleen and liver of LCMV-infected mice and alleviated the severity of ECM and LCMV-induced liver pathology. Mechanistically, we identified reduced blood-brain barrier leakage associated with reduced parasite sequestration in the brain of PbA-infected mice with T cell-specific Nrp-1 deficiency. In conclusion, Nrp-1 expression on CD8+ T cells represents a very early activation marker that exacerbates deleterious CD8+ T cell responses during both, parasitic PbA and acute LCMV infections.

Challenges and opportunities in the development of combination immunotherapy with OX40 agonists

INTRODUCTION

Costimulatory members of the tumor necrosis factor receptor family, such as OX40 (CD134), provide essential survival and differentiation signals that enhance T cell function. Specifically, OX40 (CD134) agonists stimulate potent anti-tumor immunity in a variety of preclinical models but their therapeutic impact in patients with advanced malignancies has been limited thus far.

AREAS COVERED

In this review, we discuss the current state of combination immunotherapy with OX40 agonists including preclinical studies and recent clinical trials. We also discuss the strengths and limitations of these approaches and provide insight into alternatives that may help enhance the efficacy of combination OX40 agonist immunotherapy.

EXPERT OPINION

OX40 agonist immunotherapy has not yet demonstrated significant clinical activity as a monotherapy or in combination with immune checkpoint blockade (ICB), likely due to several factors including the timing of administration, drug potency, and selection of agents for combination therapy clinical trials. We believe that careful consideration of the biological mechanisms regulating OX40 expression and function may help inform new approaches, particularly in combination with novel agents, capable of increasing the therapeutic efficacy of this approach.

First-in-human phase I/II, open-label study of the anti-OX40 agonist INCAGN01949 in patients with advanced solid tumors

BACKGROUND

OX40 is a costimulatory receptor upregulated on antigen-activated T cells and constitutively expressed on regulatory T cells (Tregs). INCAGN01949, a fully human immunoglobulin G1κ anti-OX40 agonist monoclonal antibody, was designed to promote tumor-specific immunity by effector T-cell activation and Fcγ receptor-mediated Treg depletion. This first-in-human study was conducted to determine the safety, tolerability, and preliminary efficacy of INCAGN01949.

METHODS

Phase I/II, open-label, non-randomized, dose-escalation and dose-expansion study conducted in patients with advanced or metastatic solid tumors. Patients received INCAGN01949 monotherapy (7-1400 mg) in 14-day cycles while deriving benefit. Safety measures, clinical activity, pharmacokinetics, and pharmacodynamic effects were assessed and summarized with descriptive statistics.

RESULTS

Eighty-seven patients were enrolled; most common tumor types were colorectal (17.2%), ovarian (8.0%), and non-small cell lung (6.9%) cancers. Patients received a median three (range 1-9) prior therapies, including immunotherapy in 24 patients (27.6%). Maximum tolerated dose was not reached; one patient (1.1%) receiving 350 mg dose reported dose-limiting toxicity of grade 3 colitis. Treatment-related adverse events were reported in 45 patients (51.7%), with fatigue (16 (18.4%)), rash (6 (6.9%)), and diarrhea (6 (6.9%)) being most frequent. One patient (1.1%) with metastatic gallbladder cancer achieved a partial response (duration of 6.3 months), and 23 patients (26.4%) achieved stable disease (lasting >6 months in one patient). OX40 receptor occupancy was maintained over 90% among all patients receiving doses of ≥200 mg, while no treatment-emergent antidrug antibodies were detected across all dose levels. Pharmacodynamic results demonstrated that treatment with INCAGN01949 did not enhance proliferation or activation of T cells in peripheral blood or reduce circulating Tregs, and analyses of tumor biopsies did not demonstrate any consistent increase in effector T-cell infiltration or function, or decrease in infiltrating Tregs.

CONCLUSION

No safety concerns were observed with INCAGN01949 monotherapy in patients with metastatic or advanced solid tumors. However, tumor responses and pharmacodynamic effects on T cells in peripheral blood and post-therapy tumor biopsies were limited. Studies evaluating INCAGN01949 in combination with other therapies are needed to further evaluate the potential of OX40 agonism as a therapeutic approach in patients with advanced solid tumors.

TRIAL REGISTRATION NUMBER

NCT02923349.

Development of OX40 agonists for canine cancer immunotherapy

Recent breakthroughs in cancer immunotherapy have provided unprecedented clinical benefits to human cancer patients. Cancer is also one of the most common causes of death in pet dogs. Thus, canine-specific immune therapies targeting similar signaling pathways can provide better treatment options for canine cancer patients. Here, we describe the development and characterization of two canine-specific anti-OX40 agonists to activate OX40 signaling. We show that canine OX40, like human OX40, is not expressed on resting T cells, and its expression is markedly increased on canine CD4 T cells and Tregs after stimulation with concanavalin A (Con-A). cOX40 is also expressed on tumor-infiltrating lymphocytes (TILs) in canine osteosarcoma patients. The canine-specific OX40 agonists strongly activates cPBMCs by increasing IFN-γ expression and do not require Fc receptor-mediated cross-linking for OX40 agonism. Together, these results suggest that cFcOX40L proteins are potent OX40 agonists and have the potential to enhance antitumor immunity in canine cancer patients.

Immune Recovery Following Autologous Hematopoietic Stem Cell Transplantation in HIV-Related Lymphoma Patients on the BMT CTN 0803/AMC 071 Trial

We report a first in-depth comparison of immune reconstitution in patients with HIV-related lymphoma following autologous hematopoietic cell transplant (AHCT) recipients (n=37, lymphoma, BEAM conditioning), HIV(-) AHCT recipients (n=30, myeloma, melphalan conditioning) at 56, 180, and 365 days post-AHCT, and 71 healthy control subjects. Principal component analysis showed that immune cell composition in HIV(+) and HIV(-) AHCT recipients clustered away from healthy controls and from each other at each time point, but approached healthy controls over time. Unsupervised feature importance score analysis identified activated T cells, cytotoxic memory and effector T cells [higher in HIV(+)], and naïve and memory T helper cells [lower HIV(+)] as a having a significant impact on differences between HIV(+) AHCT recipient and healthy control lymphocyte composition (p<0.0033). HIV(+) AHCT recipients also demonstrated lower median absolute numbers of activated B cells and lower NK cell sub-populations, compared to healthy controls (p<0.0033) and HIV(-) AHCT recipients (p<0.006). HIV(+) patient T cells showed robust IFNγ production in response to HIV and EBV recall antigens. Overall, HIV(+) AHCT recipients, but not HIV(-) AHCT recipients, exhibited reconstitution of pro-inflammatory immune profiling that was consistent with that seen in patients with chronic HIV infection treated with antiretroviral regimens. Our results further support the use of AHCT in HIV(+) individuals with relapsed/refractory lymphoma.

Priming Leukemia with 5-Azacytidine Enhances CAR T Cell Therapy

Purpose

Despite the success of chimeric antigen receptor (CAR) T cells in clinical studies, a significant proportion of responding patients eventually relapsed, with the latter correlating with low CAR T cell expansion and persistence.

Methods and Results

Using patient-derived xenograft (PDX) mouse models of CD19⁺ B cell acute lymphoblastic leukemia (B-ALL), we show that priming leukemia-bearing mice with 5-azacytidine (AZA) enhances CAR T cell therapy. AZA given 1 day prior to CAR T cell infusion delayed leukemia growth and promoted CAR T cell expansion and effector function. Priming leukemia cells with AZA increased CAR T cell/target cell conjugation and target cell killing, promoted CAR T cell divisions and expanded IFNγ⁺ effector T cells in co-cultures with CD19⁺ leukemia Nalm-6 and Raji cells. Transcriptome analysis revealed activation of diverse immune pathways in leukemia cells isolated from mice treated with AZA. We propose that epigenetic priming with AZA induces transcriptional changes that sensitize tumor cells to subsequent CAR T cell treatment. Among the candidate genes up-regulated by AZA is TNFSF4 which encodes OX40L, one of the strongest T cell co-stimulatory ligands. OX40L binds OX40, the TNF receptor superfamily member highly specific for activated T cells. TNFSF4 is heterogeneously expressed in a panel of pediatric PDXs, and high TNFSF4 expression correlated with increased CAR T cell numbers identified in co-cultures with individual PDXs. High OX40L expression in Nalm-6 cells increased their susceptibility to CAR T cell killing while OX40L blockade reduced leukemia cell killing.

Conclusion

We propose that treatment with AZA activates OX40L/OX40 co-stimulatory signaling in CAR T cells. Our data suggest that the clinical use of AZA before CAR T cells could be considered.

PD-L1 Expression Correlated with p53 Expression in Pediatric Glioblastoma Multiforme

High-grade gliomas are infrequent in the pediatric population compared to adults, nevertheless, mortality and morbidity caused by malignant gliomas in this group of patients remain significant. PD-L1 and PD-1 Immune checkpoints (IC) molecules maintain immunological balance between activation and suppression. Eighteen patients with a histopathological diagnosis of pediatric glioblastoma multiforme (GBM, WHO IV) were studied. In total, PD-L1 expression was detected in 8 patients (44%). The molecular aspect of IC and immunotherapy targeted on PD-1/PD-L1 axis in pediatric population may be a promising adjuvant therapy in pediatric glioblastoma multiform treatment, however, this subject requires further investigation.

Antiapoptotic Clone 11-Derived Peptides Induce In Vitro Death of CD4+ T Cells Susceptible to HIV-1 Infection

HIV-1 successfully establishes long-term infection in its target cells despite viral cytotoxic effects. We have recently shown that cell metabolism is an important factor driving CD4+ T cell susceptibility to HIV-1 and the survival of infected cells. We show here that expression of antiapoptotic clone 11 (AAC-11), an antiapoptotic factor upregulated in many cancers, increased with progressive CD4+ T cell memory differentiation in association with the expression of cell cycle, activation, and metabolism genes and was correlated with susceptibility to HIV-1 infection. Synthetic peptides based on the LZ domain sequence of AAC-11, responsible for its interaction with molecular partners, were previously shown to be cytotoxic to cancer cells. Here, we observed that these peptides also blocked HIV-1 infection by inducing the death of HIV-1-susceptible primary CD4+ T cells across all T cell subsets. The peptides targeted metabolically active cells and had the greatest effect on effector and transitional CD4+ T cell memory subsets. Our results suggest that the AAC-11 survival pathway is potentially involved in the survival of HIV-1-infectible cells and provide proof of principle that some cellular characteristics can be targeted to eliminate the cells offering the best conditions to sustain HIV-1 replication.IMPORTANCE Although antiretroviral treatment efficiently blocks HIV multiplication, it cannot eliminate cells already carrying integrated proviruses. In the search for an HIV cure, the identification of new potential targets to selectively eliminate infected cells is of the outmost importance. We show here that peptides derived from antiapoptotic clone 11 (AAC-11), whose expression levels correlated with susceptibility to HIV-1 infection of CD4+ T cells, induced cytotoxicity in CD4+ T cells showing the highest levels of activation and metabolic activity, conditions known to favor HIV-1 infection. Accordingly, CD4+ T cells that survived the cytotoxic action of the AAC-11 peptides were resistant to HIV-1 replication. Our results identify a new potential molecular pathway to target HIV-1 infection.

IL-22 production of effector CD4+ T-cells is altered in SLE patients

BACKGROUND

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by T-cell-dependent B-cell activation and altered T-cell response. Co-stimulatory and co-inhibitory molecules regulate and exert T-cell differentiation, survival and cytokine production. CD134+ and PD-1+ T-cells in SLE patients are increased in SLE. The aim of this study was to characterize CD134+ and PD-1+CD4+ T-cells according to their ability to produce IFN-γ, IL-21 and IL-22 in SLE patients.

METHODS

Peripheral blood of 39 SLE patients and 19 healthy controls (HC) was stimulated with phorbol myristate acetate (PMA) calcium ionophore (Ca-Io). The expression of IFN-γ, IL-21 and IL-22 T-cells within the CD134+ and PD-1+ T-cells was analyzed by flow cytometry. Disease activity was assessed by SLE Disease Activity Index.

RESULTS

Peripheral unstimulated CD134+ and PD-1+ CD4+ T-cells were significantly increased in patients with lupus nephritis. Upon stimulation both, CD134+ and PD-1+ CD4+ T-cells, produced significantly less IFN-γ in SLE patients as compared to HC. The percentages of IL-22 within the CD134+CD4+ T-cells were also significantly decreased in SLE as compared to HC.

CONCLUSION

CD134+ and PD-1+CD4+ T-cells have mainly a Th1 effector T-cell signature. A lower proportion produces also IL-21 and IL-22. The impaired capacity to produce IFN-γ and IL-22 in SLE patients may contribute to the pathogenesis of the disease.

Challenges and potential of PD-1/PD-L1 checkpoint blockade immunotherapy for glioblastoma

PD-1/PD-L1 checkpoint blockades have achieved significant progress in several kinds of tumours. Pembrolizumab, which targets PD-1, has been approved as a first-line treatment for advanced non-small cell lung cancer (NSCLC) patients with positive PD-L1 expression. However, PD-1/PD-L1 checkpoint blockades have not achieved breakthroughs in treating glioblastoma because glioblastoma has a low immunogenic response and an immunosuppressive microenvironment caused by the precise crosstalk between cytokines and immune cells. A phase III clinical trial, Checkmate 143, reported that nivolumab, which targets PD-1, did not demonstrate survival benefits compared with bavacizumab in recurrent glioblastoma patients. Thus, the combination of a PD-1/PD-L1 checkpoint blockade with RT, TMZ, antibodies targeting other inhibitory or stimulatory molecules, targeted therapy, and vaccines may be an appealing solution aimed at achieving optimal clinical benefit. There are many ongoing clinical trials exploring the efficacy of various approaches based on PD-1/PD-L1 checkpoint blockades in primary or recurrent glioblastoma patients. Many challenges need to be overcome, including the identification of discrepancies between different genomic subtypes in their response to PD-1/PD-L1 checkpoint blockades, the selection of PD-1/PD-L1 checkpoint blockades for primary versus recurrent glioblastoma, and the identification of the optimal combination and sequence of combination therapy. In this review, we describe the immunosuppressive molecular characteristics of the tumour microenvironment (TME), candidate biomarkers of PD-1/PD-L1 checkpoint blockades, ongoing clinical trials and challenges of PD-1/PD-L1 checkpoint blockades in glioblastoma.

Late-Stage Tumor Regression after PD-L1 Blockade Plus a Concurrent OX40 Agonist

The protective capability of tumor antigen-specific T cells is regulated by costimulatory and inhibitory signals. Current approaches in cancer immunotherapy seek to restore the function of unresponsive T cells by blocking inhibitory pathways. In contrast, providing exogenous costimulatory signals to T cells also enhances antitumor functionality. By combining these two clinical approaches, we demonstrate the synergy of targeting PD-L1 together with the costimulatory molecule OX40, to enhance antitumor immunity. Concurrently blocking PD-L1 and providing a costimulatory agonist to OX40 increased the presence and functionality of tumor antigen-specific CD8⁺ T cells with simultaneous enhancement of T-helper type 1 (Th1)-skewed CD4⁺ T cells. This shift was functionally supported by increased glucose metabolism of antigen-specific CD8⁺ T cells and the acquisition of granzyme B by regulatory T cells. Together, this mechanism promoted tumor regression of late-stage tumors beyond that achieved by either blockade as monotherapy. These findings indicate that targeting both T-cell intrinsic (OX40) and extrinsic (PD-L1) regulatory molecules increases the bioenergetic potential of T cells, thereby expanding functional and tumor antigen-specific T cells.

Prior Puma Lentivirus Infection Modifies Early Immune Responses and Attenuates Feline Immunodeficiency Virus Infection in Cats

We previously showed that cats that were infected with non-pathogenic Puma lentivirus (PLV) and then infected with pathogenic feline immunodeficiency virus (FIV) (co-infection with the host adapted/pathogenic virus) had delayed FIV proviral and RNA viral loads in blood, with viral set-points that were lower than cats infected solely with FIV. This difference was associated with global CD4⁺ T cell preservation, greater interferon gamma (IFN-γ) mRNA expression, and no cytotoxic T lymphocyte responses in co-infected cats relative to cats with a single FIV infection. In this study, we reinforced previous observations that prior exposure to an apathogenic lentivirus infection can diminish the effects of acute infection with a second, more virulent, viral exposure. In addition, we investigated whether the viral load differences that were observed between PLV/FIV and FIV infected cats were associated with different immunocyte phenotypes and cytokines. We found that the immune landscape at the time of FIV infection influences the infection outcome. The novel findings in this study advance our knowledge about early immune correlates and documents an immune state that is associated with PLV/FIV co-infection that has positive outcomes for lentiviral diseases.

Timing of PD-1 Blockade Is Critical to Effective Combination Immunotherapy with Anti-OX40

Purpose: Antibodies specific for inhibitory checkpoints PD-1 and CTLA-4 have shown impressive results against solid tumors. This has fueled interest in novel immunotherapy combinations to affect patients who remain refractory to checkpoint blockade monotherapy. However, how to optimally combine checkpoint blockade with agents targeting T-cell costimulatory receptors, such as OX40, remains a critical question.Experimental Design: We utilized an anti-PD-1-refractory, orthotopically transplanted MMTV-PyMT mammary cancer model to investigate the antitumor effect of an agonist anti-OX40 antibody combined with anti-PD-1. As PD-1 naturally aids in immune contraction after T-cell activation, we treated mice with concurrent combination treatment versus sequentially administering anti-OX40 followed by anti-PD-1.Results: The concurrent addition of anti-PD-1 significantly attenuated the therapeutic effect of anti-OX40 alone. Combination-treated mice had considerable increases in type I and type II serum cytokines and significantly augmented expression of inhibitory receptors or exhaustion markers CTLA-4 and TIM-3 on T cells. Combination treatment increased intratumoral CD4⁺ T-cell proliferation at day 13, but at day 19, both CD4⁺ and CD8⁺ T-cell proliferation was significantly reduced compared with untreated mice. In two tumor models, sequential combination of anti-OX40 followed by anti-PD-1 (but not the reverse order) resulted in significant increases in therapeutic efficacy. Against MMTV-PyMT tumors, sequential combination was dependent on both CD4⁺ and CD8⁺ T cells and completely regressed tumors in approximately 30% of treated animals.Conclusions: These results highlight the importance of timing for optimized therapeutic effect with combination immunotherapies and suggest the testing of sequencing in combination immunotherapy clinical trials. Clin Cancer Res; 23(20); 6165-77. ©2017 AACRSee related commentary by Colombo, p. 5999.

Optimal CD4 T cell priming after LPS-based adjuvanticity with CD134 costimulation relies on CXCL9 production

LPS is a powerful adjuvant, and although LPS-mediated TLR4 signaling has been exquisitely delineated, the in vivo mechanism of how TLR4 responses impact T cell priming is far less clear. Besides costimulation, TNF and type 1 IFN are dominant cytokines released after TLR4 activation and can shape T cell responses, but other downstream factors have not been examined extensively. Depending on context, we show that IFNαR1 blockade resulted in minor to major effects on specific CD4 T cell clonal expansion. To help explain these differences, it was hypothesized that IFNαR1 blockade would inhibit specific T cell migration by reducing chemokine receptor signaling, but specific CD4 T cells from IFNαR1-blocked mice were readily able to migrate in response to specific chemokines. Next, we examined downstream factors and found that type 1 IFN signaling was necessary for chemokine production, even when mice were immunized with specific Ag with LPS and CD134 costimulation. IFNαR1 signaling promoted CXCL9 and CXCL10 synthesis, suggesting that these chemokines might be involved in the LPS and CD134 costimulation response. After immunization, we show that CXCL9 blockade inhibited CD4 T cell accumulation in the liver but also in LNs, even in the presence of elevated serum IFN-β levels. Thus, whereas type 1 IFN might have direct effects on primed CD4 T cells, the downstream chemokines that play a role during migration also impact accumulation. In sum, CXCL9 production is a key benchmark for productive CD4 T cell vaccination strategies.

Enhancing the safety of antibody-based immunomodulatory cancer therapy without compromising therapeutic benefit: Can we have our cake and eat it too?

INTRODUCTION

Monoclonal antibodies (mAbs) targeting checkpoint inhibitors have demonstrated clinical benefit in treating patients with cancer and have paved the way for additional immune-modulating mAbs such as those targeting costimulatory receptors. The full clinical utility of these agents, however, is hampered by immune-related adverse events (irAEs) that can occur during therapy.

AREAS COVERED

We first provide a general overview of tumor immunity, followed by a review of the two major classes of immunomodulatory mAbs being developed as cancer therapeutics: checkpoint inhibitors and costimulatory receptor agonists. We then discuss therapy-associated adverse events. Finally, we describe in detail the mechanisms driving their therapeutic activity, with an emphasis on interactions between antibody fragment crystallizable (Fc) domains and Fc receptors (FcR).

EXPERT OPINION

Given that Fc-FcR interactions appear critical in facilitating the ability of immunomodulatory mAbs to elicit both therapeutically useful as well as adverse effects, the engineering of mAbs that can effectively engage their targets while limiting interaction with FcRs might represent a promising future avenue for developing the next generation of immune-enhancing tumoricidal agents with increased safety and retention of efficacy.

Betting on improved cancer immunotherapy by doubling down on CD134 and CD137 co-stimulation

The ability of T cells to recognize a vast array of antigens enables them to destroy tumor cells while inflicting minimal collateral damage. Nevertheless, tumor antigens often are a form of self-antigen, and thus tumor immunity can be dampened by tolerance mechanisms that evolved to prevent autoimmunity. Since tolerance can be induced by steady-state antigen-presenting cells that provide insufficient co-stimulation, the exogenous administration of co-stimulatory agonists can favor the expansion and tumoricidal functions of tumor-specific T cells. Agonists of the co-stimulatory tumor necrosis factor receptor (TNFR) family members CD134 and CD137 exert antitumor activity in mice, and as monotherapies have exhibited encouraging results in clinical trials. This review focuses on how the dual administration of CD134 and CD137 agonists synergistically boosts T-cell priming and elaborates a multi-pronged antitumor immune response, as well as how such dual co-stimulation might be translated into effective anticancer therapies.

Skin thymic stromal lymphopoietin initiates Th2 responses through an orchestrated immune cascade

Thymic stromal lymphopoietin (TSLP) has emerged as a key initiator in Th2 immune responses, but the TSLP-driven immune cascade leading to Th2 initiation remains to be delineated. Here, by dissecting the cellular network triggered by mouse skin TSLP in vivo, we uncover that TSLP-promoted IL-4 induction in CD4(+) T cells in skin-draining lymph nodes is driven by an orchestrated 'DC-T-Baso-T' cascade, which represents a sequential cooperation of dendritic cells (DCs), CD4(+) T cells and basophils. Moreover, we reveal that TSLP-activated DCs prime naive CD4(+) T cells to produce IL-3 via OX40L signalling and demonstrate that the OX40L-IL-3 axis has a critical role in mediating basophil recruitment, CD4(+) T-cell expansion and Th2 priming. These findings thus add novel insights into the cellular network and signal axis underlying the initiation of Th2 immune responses.

Exogenous OX40 stimulation during lymphocytic choriomeningitis virus infection impairs follicular Th cell differentiation and diverts CD4 T cells into the effector lineage by upregulating Blimp-1

T cell costimulation is a key component of adaptive immunity to viral infection but has also been associated with pathology because of excessive or altered T cell activity. We recently demonstrated that the TNFR family costimulatory molecule OX40 (CD134) is critically required to sustain antiviral T cell and Ab responses that enable control of viral replication in the context of chronic lymphocytic choriomeningitis virus (LCMV) infection. In this study, we investigated whether reinforcing OX40 stimulation through an agonist Ab had the potential to prevent LCMV persistence. We observed that anti-OX40 injection early after LCMV clone 13 infection increased CD8 T cell-mediated immunopathology. More strikingly, OX40 stimulation of virus-specific CD4 T cells promoted expression of the transcriptional repressor Blimp-1 and diverted the majority of cells away from follicular Th cell differentiation. This occurred in both acute and chronic infections, and resulted in dramatic reductions in germinal center and Ab responses to the viral infection. The effect of the OX40 agonist was dependent on IL-2 signaling and the timing of OX40 stimulation. Collectively, our data demonstrate that excessive OX40 signaling can result in deleterious consequences in the setting of LCMV infection.

Peripheral CD4(+) T-cell tolerance is induced in vivo by rare antigen-bearing B cells in follicular, marginal zone, and B-1 subsets

B cells are efficient APCs when they internalize antigen via BCR-mediated uptake. Adoptively transferred antigen-presenting B cells can induce T-cell tolerance to foreign and self antigens; however, it is unknown whether endogenous B cells presenting self-peptides interact with naïve T cells and contribute to peripheral T-cell self-tolerance. Moreover, the relative abilities of mature B-cell subsets to induce T-cell tolerance have not been examined. To address these questions, we created a new mouse model wherein a very small fraction of B cells expresses an antigen transgene that cannot be transferred to other APCs. We limited antigen expression to follicular, marginal zone, or B-1 B-cell subsets and found that small numbers of each subset interacted with naïve antigen-specific T cells. Although antigen expressed by B-1 B cells induced the most T-cell division, divided T cells subsequently disappeared from secondary lymphoid tissues. Independent of which B-cell subset presented antigen, the remaining T cells were rendered hypo-responsive, and this effect was not associated with Foxp3 expression. Our data show that physiologically relevant proportions of B cells can mediate peripheral T-cell tolerance, and suggest that the mechanisms of tolerance induction might differ among follicular, marginal zone, and B-1 B-cell subsets.

In situ observation of the effects of local irradiation on cytotoxic and regulatory T lymphocytes in cervical cancer tissue

Local radiotherapy is the major therapeutic approach to control inoperable cervical cancer. In this study, we analyzed the local immune microenvironment of cervical cancer before and after clinical radiation therapy to investigate whether tumor response due to immunomodulation. A total of 59 patients with pathologically diagnosed cervical cancers classified according to the International Federation of Obstetrics and Gynecology (FIGO) criteria were recruited. The patients were treated according to their disease status with standard radiation regimens. For each patient, tumor biopsies were conducted before, during and after radiation treatment with the doses of 0, 10, 20 and 30 Gy, respectively. All of the tumor samples were then grouped according to the doses delivered and tumor infiltrating lymphocytes with the biomarkers of CD8, CD4, FOXP3 and OX40 were measured by in situ immunohistochemistry. We found that before radiation treatment both CD8(+) T cell and CD4(+) T cell infiltrates were more present in the tumor stroma than in the tumor nests, while OX40(+) and FOXP3(+) T cell infiltrates were present at similar levels in both the tumor nests and stroma. After radiation treatment, the levels of CD8(+) T cells and CD4(+) T cells in the tumor nests and stroma were decreased compared with the levels before irradiation. However, OX40(+) T cells and FOXP3(+) T cells did not show any difference before and after irradiation, which indicates that the FOXP3(+) T cells were more resistant to ionizing radiation than were the cytotoxic effector T cells and demonstrates a dynamic rebalance of infiltrating lymphocytes in the tumor milieu occurs after radiotherapy. This suggest that local antitumor immunity could be compromised due to decreased cytotoxic effector cells and the relatively stable status of FOXP3(+) T cells after irradiation. Therefore, regulation of these FOXP3(+) T cells may be a potentially effective approach to enhance the efficacy of cancer radiation therapy.

CD134/CD137 dual costimulation-elicited IFN-γ maximizes effector T-cell function but limits Treg expansion

T cell tolerance to tumor antigens represents a major hurdle in generating tumor immunity. Combined administration of agonistic monoclonal antibodies to the costimulatory receptors CD134 plus CD137 can program T cells responding to tolerogenic antigen to undergo expansion and effector T cell differentiation, and also elicits tumor immunity. Nevertheless, CD134 and CD137 agonists can also engage inhibitory immune components. To understand how immune stimulatory versus inhibitory components are regulated during CD134 plus CD137 dual costimulation, the current study utilized a model where dual costimulation programs T cells encountering a highly tolerogenic self-antigen to undergo effector differentiation. IFN-γ was found to play a pivotal role in maximizing the function of effector T cells while simultaneously limiting the expansion of CD4⁺CD25⁺Foxp3⁺ Tregs. In antigen-responding effector T cells, IFN-γ operates via a direct cell-intrinsic mechanism to cooperate with IL-2 to program maximal expression of granzyme B. Simultaneously, IFN-γ limits expression of the IL-2 receptor alpha chain (CD25) and IL-2 signaling through a mechanism that does not involve T-bet-mediated repression of IL-2. IFN-γ also limited CD25 and Foxp3 expression on bystanding CD4⁺Foxp3⁺ Tregs, and limited the potential of these Tregs to expand. These effects could not be explained by the ability of IFN-γ to limit IL-2 availability. Taken together, during dual costimulation IFN-γ interacts with IL-2 through distinct mechanisms to program maximal expression of effector molecules in antigen-responding T cells while simultaneously limiting Treg expansion.

Study on the expression of co-stimulatory marker CD134 on CD4+ T cells in HIV-1-infected individuals

CD4+CD25+CD134+ T cells play an important role in suppressing T cell responses to foreign pathogens, including human immunodeficiency virus (HIV). Thus, we aimed to investigate an increase in these populations in HIV-1-infected individuals. In this study, we used a panel of monoclonal antibodies staining of CD3/CD4/CD25/CD134. Without antigen stimulation, the expression of CD4+CD25+CD134+ T cells in 14 HIV-1-infected and 24 healthy individuals were 4.01% and 3.21%, respectively. However, there was an increase in the expression of CD4 + CD25+CD134+ T cells in HIV-1-infected individuals (6.85%) when stimulated with gag peptide. The upregulation of CD4+CD25+CD134+ T cells in HIV-1-infected individuals may result from activation of naturally occurring or by disease-associated antigen stimulation.

NF-κB–inducing kinase plays an essential T cell–intrinsic role in graft-versus-host disease and lethal autoimmunity in mice

NF-κB–inducing kinase (NIK) is an essential upstream kinase in noncanonical NF-κB signaling. NIK-dependent NF-κB activation downstream of several TNF receptor family members mediates lymphoid organ development and B cell homeostasis. Peripheral T cell populations are normal in the absence of NIK, but the role of NIK during in vivo T cell responses to antigen has been obscured by other developmental defects in NIK-deficient mice. Here, we have identified a T cell–intrinsic requirement for NIK in graft-versus-host disease (GVHD), wherein NIK-deficient mouse T cells transferred into MHC class II mismatched recipients failed to cause GVHD. Although NIK was not necessary for antigen receptor signaling, it was absolutely required for costimulation through the TNF receptor family member OX40 (also known as CD134). When we conditionally overexpressed NIK in T cells, mice suffered rapid and fatal autoimmunity characterized by hyperactive effector T cells and poorly suppressive Foxp3(+) Tregs. Together, these data illuminate a critical T cell–intrinsic role for NIK during immune responses and suggest that its tight regulation is critical for avoiding autoimmunity.

The small molecule TGF-β signaling inhibitor SM16 synergizes with agonistic OX40 antibody to suppress established mammary tumors and reduce spontaneous metastasis

Effective tumor immunotherapy may require not only activation of anti-tumor effector cells, but also abrogation of tumor-mediated immunosuppression. The cytokine TGF-β, is frequently elevated in the tumor microenvironment and is a potent immunosuppressive agent and promoter of tumor metastasis. OX40 (CD134) is a member of the TNF-α receptor superfamily and ligation by agonistic antibody (anti-OX40) enhances effector function, expansion, and survival of activated T cells. In this study, we examined the therapeutic efficacy and anti-tumor immune response induced by the combination of a small molecule TGF-β signaling inhibitor, SM16, plus anti-OX40 in the poorly immunogenic, highly metastatic, TGF-β-secreting 4T1 mammary tumor model. Our data show that SM16 and anti-OX40 mutually enhanced each other to elicit a potent anti-tumor effect against established primary tumors, with a 79% reduction in tumor size, a 95% reduction in the number of metastatic lung nodules, and a cure rate of 38%. This positive treatment outcome was associated with a 3.2-fold increase of tumor-infiltrating, activated CD8+ T cells, an overall accumulation of CD4+ and CD8+ T cells, and an increased tumor-specific effector T cell response. Complete abrogation of the therapeutic effect in vivo following depletion of CD4+ and CD8+ T cells suggests that the anti-tumor efficacy of SM16+ anti-OX40 therapy is T cell dependent. Mice that were cured of their tumors were able to reject tumor re-challenge and manifested a significant tumor-specific peripheral memory IFN-γ response. Taken together, these data suggest that combining a TGF-β signaling inhibitor with anti-OX40 is a viable approach for treating metastatic breast cancer.

Cyclosporine-resistant, Rab27a-independent mobilization of intracellular preformed CD40 ligand mediates antigen-specific T cell help in vitro

CD40L is critically important for the initiation and maintenance of adaptive immune responses. It is generally thought that CD40L expression in CD4(+) T cells is regulated transcriptionally and made from new mRNA following Ag recognition. However, recent studies with two-photon microscopy revealed that most cognate interactions between effector CD4(+) T cells and APCs are too short for de novo synthesis of CD40L. Given that effector and memory CD4(+) T cells store preformed CD40L (pCD40L) in lysosomal compartments and that pCD40L comes to the cell surface within minutes of antigenic stimulation, we and others have proposed that pCD40L might mediate T cell-dependent activation of cognate APCs during brief encounters in vivo. However, it has not been shown that this relatively small amount of pCD40L is sufficient to activate APCs, owing to the difficulty of separating the effects of pCD40L from those of de novo CD40L and other cytokines in vitro. In this study, we show that pCD40L surface mobilization is resistant to cyclosporine or FK506 treatment, while de novo CD40L and cytokine expression are completely inhibited. These drugs thus provide a tool to dissect the role of pCD40L in APC activation. We find that pCD40L mediates selective activation of cognate but not bystander APCs in vitro and that mobilization of pCD40L does not depend on Rab27a, which is required for mobilization of lytic granules. Therefore, effector CD4(+) T cells deliver pCD40L specifically to APCs on the same time scale as the lethal hit of CTLs but with distinct molecular machinery.

A non-redundant role for OX40 in the competitive fitness of Treg in response to IL-2

OX40 stimulation is known to enhance activation of effector T cells and to inhibit induction and suppressive function of Treg. Here we uncovered a novel role of OX40 in sustaining Treg competitive fitness in vivo, during repopulation of lymphopenic hosts and reconstitution of BM chimeras. Defective expansion of OX40-null Treg diminished their ability to suppress inflammation in a model of lymphopenia-driven colitis. OX40-mediated promotion of Treg fitness spanned beyond lymphopenic environments, as endogenous Treg in OX40-null mice showed decreased accumulation during thymic development, enhanced susceptibility to antibody-mediated depletion and defective turnover following thymectomy. In vitro, OX40-deficient Treg were found to be intrinsically hyporesponsive to IL-2, in terms of Stat5 phosphorylation and proliferation, according to elevated SOCS1 content and reduced miR155 expression. Therefore, OX40 is a key factor in shaping Treg sensitivity to IL-2 and promoting their proliferation and survival, toward accurate immune regulation.

Signaling through OX40 enhances antitumor immunity

The existence of tumor-specific T cells, as well as their ability to be primed in cancer patients, confirms that the immune response can be deployed to combat cancer. However, there are obstacles that must be overcome to convert the ineffective immune response commonly found in the tumor environment to one that leads to sustained destruction of tumor. Members of the tumor necrosis factor (TNF) superfamily direct diverse immune functions. OX40 and its ligand, OX40L, are key TNF members that augment T-cell expansion, cytokine production, and survival. OX40 signaling also controls regulatory T-cell differentiation and suppressive function. Studies over the past decade have demonstrated that OX40 agonists enhance antitumor immunity in preclinical models using immunogenic tumors; however, treatment of poorly immunogenic tumors has been less successful. Combining strategies that prime tumor-specific T cells together with OX40 signaling could generate and maintain a therapeutic antitumor immune response.

Role of NFKB2 on the early myeloid differentiation of CD34+ hematopoietic stem/progenitor cells

To better understand the early events regulating lineage-specific hematopoietic differentiation, we analyzed the transcriptional profiles of CD34+ human hematopoietic stem and progenitor cells (HSPCs) subjected to differentiation stimulus. CD34+ cells were cultured for 12 and 40h in liquid cultures with supplemented media favoring myeloid or erythroid commitment. Serial analysis of gene expression (SAGE) was employed to generate four independent libraries. By analyzing the differentially expressed regulated transcripts between the un-stimulated and the stimulated CD34+ cells, we observed a set of genes that was initially up-regulated at 12h but were then down-regulated at 40h, exclusively after myeloid stimulus. Among those we found transcripts for NFKB2, RELB, IL1B, LTB, LTBR, TNFRSF4, TGFB1, and IKBKA. Also, the inhibitor NFKBIA (IKBA) was more expressed at 12h. All those transcripts code for signaling proteins of the nuclear factor kappa B pathway. NFKB2 is a subunit of the NF-κB transcription factor that with RELB mediates the non-canonical NF-κB pathway. Interference RNA (RNAi) against NFKB1, NFKB2 and control RNAi were transfected into bone marrow CD34+HSPC. The percentage and the size of the myeloid colonies derived from the CD34+ cells decreased after inhibition of NFKB2. Altogether, our results indicate that NFKB2 gene has a role in the early commitment of CD34+HSPC towards the myeloid lineage.

Increased expression of costimulatory markers CD134 and CD80 on interleukin-17 producing T cells in patients with systemic lupus erythematosus

Introduction

There is growing evidence that interleukin 17 (IL-17) producing T cells are involved in the pathogenesis of systemic lupus erythematosus (SLE). Previous studies showed that increased percentages of T-cell subsets expressing the costimulatory molecules CD80 and CD134 are associated with disease activity and renal involvement in SLE. The aim of this study was to investigate the distribution and phenotypical characteristics of IL-17 producing T-cells in SLE, in particular in patients with lupus nephritis, with emphasis on the expression of CD80 and CD134.

Methods

Thirty-four patients (3 male, 31 female, mean age 41 ± 15 years) fulfilling at least four of the American College of Rheumatology (ACR) revised criteria for the diagnosis of SLE and 24 healthy controls were enrolled. T-cells from the peripheral blood were analysed by fluorescence activated cell sorting (FACS) for their expression levels of CD80, CD134 and CCR6. In vitro stimulated CD3⁺IL17⁺ cells were also investigated for the expression of these costimulatory markers. Finally, renal biopsies from SLE patients were evaluated for the presence of CD134 expressing T-cells.

Results

Percentages of IL-17 expressing T-cells were significantly increased in patients with active disease as compared to healthy controls (1.46 ± 0.58% versus 0.93 ± 0.30%, P = 0.007). The percentage of IL-17 producing T-cells was correlated with disease activity as assessed by systemic lupus erythematosus disease activity index (SLEDAI) (r = 0.53, P = 0.003). In patients, most of the IL-17 producing T-cells were confined to the CCR6⁺ T-cell subset (80 ± 13%). Expression of CD80 and CD134 on the IL-17 producing T-cell subset was higher in SLE than in healthy controls (HC) (CD134: 71.78 ± 14.51% versus 51.45 ± 16.58%, P = 0.002; CD80: 25.5 ± 14.99% versus 14.99 ± 5.74%, P = 0.02). Also, patients with lupus nephritis expressed higher levels of CD134⁺ on CD3⁺IL-17⁺ cells as compared to HC (72.69 ± 11.54% versus 51.45 ± 16.58%, P = 0.006). Furthermore, renal biopsies of lupus nephritis patients showed infiltration of CD134⁺ T cells.

Conclusions

Percentages of IL-17 expressing T-cells correlate with disease activity. Further, these cells show increased expression of costimulatory markers such as CD134 and CD80. The presence of CD134⁺ T-cells in renal biopsies of lupus nephritis patients suggest that these cells migrate to the kidney and might contribute to inflammatory processes through IL-17 secretion.

Comparison of OX40 ligand and CD70 in the promotion of CD4+ T cell responses

The TNF superfamily members CD70 and OX40 ligand (OX40L) were reported to be important for CD4(+) T cell expansion and differentiation. However, the relative contribution of these costimulatory signals in driving CD4(+) T cell responses has not been addressed. In this study, we found that OX40L is a more important determinant than CD70 of the primary CD4(+) T cell response to multiple immunization regimens. Despite the ability of a combined TLR and CD40 agonist (TLR/CD40) stimulus to provoke appreciable expression of CD70 and OX40L on CD8(+) dendritic cells, resulting CD4(+) T cell responses were substantially reduced by Ab blockade of OX40L and, to a lesser degree, CD70. In contrast, the CD8(+) T cell responses to combined TLR/CD40 immunization were exclusively dependent on CD70. These requirements for CD4(+) and CD8(+) T cell activation were not limited to the use of combined TLR/CD40 immunization, because vaccinia virus challenge elicited primarily OX40L-dependent CD4 responses and exclusively CD70-dependent CD8(+) T cell responses. Attenuation of CD4(+) T cell priming induced by OX40L blockade was independent of signaling through the IL-12R, but it was reduced further by coblockade of CD70. Thus, costimulation by CD70 or OX40L seems to be necessary for primary CD4(+) T cell responses to multiple forms of immunization, and each may make independent contributions to CD4(+) T cell priming.

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

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

OX40 (CD134) and OX40L

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

CD134-allodepletion allows selective elimination of alloreactive human T cells without loss of virus-specific and leukemia-specific effectors

Graft-versus-host disease (GVHD) remains a frequent and severe complication of allogeneic stem cell transplantation (SCT). One approach to reducing alloreactivity is to deplete the graft of alloreactive T cells. Global T cell depletion results in poor immune reconstitution with high mortality from viral infections and disease relapse. Therefore, an approach to selectively deplete alloreactive T cells without compromising other responses would be highly beneficial. We undertook studies to identify an inducible activation marker expressed on alloreactive effector T cells following culture with HLA-mismatched allostimulators. Compared to other markers, CD134 was superior because of its negative baseline expression and rapid upregulation after activation. Depletion of CD134(+) cells from responder populations dramatically reduced specific alloreactivity as determined by reduction of helper T cell precursor frequencies below the threshold predicting development of clinical GVHD while retaining responses to third-party alloantigens. CD134-allodepleted populations retained effectors specific for the Wilms' tumor (WT1) leukemia antigen as determined by WT1 specific pentamers, and CMV-specific effectors as determined by CMV-specific pentamers and CMV-specific ELISpot. Thus, use of CD134-allodepleted grafts may improve allogeneic SCT by reducing GVHD without loss of pathogen-specific and leukemia-specific immunity.

Monosomy 1p36 uncovers a role for OX40 in survival of activated CD4+ T cells

Monosomy 1p36 is a subtelomeric deletion syndrome associated with congenital anomalies presumably due to haploinsufficiency of multiple genes. Although immunodeficiency has not been reported, genes encoding costimulatory molecules of the TNF receptor superfamily (TNFRSF) are within 1p36 and may be affected. In one patient with monosomy 1p36, comparative genome hybridization and fluorescence in- situ hybridization confirmed that TNFRSF member OX40 was included within the subtelomeric deletion. T cells from this patient had decreased OX40 expression after stimulation. Specific, ex vivo T cell activation through OX40 revealed enhanced proliferation, and reduced viability of patient CD4+ T cells, providing evidence for the association of monosomy 1p36 with reduced OX40 expression, and decreased OX40-induced T cell survival. These results support a role for OX40 in human immunity, and calls attention to the potential for haploinsufficiency deletions of TNFRSF costimulatory molecules in monosomy 1p36.

IL-12 is required for anti-OX40-mediated CD4 T cell survival

Engagement of OX40 greatly improves CD4 T cell function and survival. Previously, we showed that both OX40 engagement and CTLA-4 blockade led to enhanced CD4 T cell expansion, but only OX40 signaling increased survival. To identify pathways associated with OX40-mediated survival, the gene expression of Ag-activated CD4 T cells isolated from mice treated with anti-OX40 and -CTLA-4 was compared. This comparison revealed a potential role for IL-12 through increased expression of the IL-12R-signaling subunit (IL-12Rbeta2) on T cells activated 3 days previously with Ag and anti-OX40. The temporal expression of IL-12Rbeta2 on OX40-stimulated CD4 T cells was tightly regulated and peaked approximately 4-6 days after initial activation/expansion, but before the beginning of T cell contraction. IL-12 signaling, during this window of IL-12Rbeta2 expression, was required for enhanced T cell survival and survival was associated with STAT4-specific signaling. The findings from these observations were exploited in several different mouse tumor models where we found that the combination of anti-OX40 and IL-12 showed synergistic therapeutic efficacy. These results may lead to the elucidation of the molecular pathways involved with CD4 T cell survival that contribute to improved memory, and understanding of these pathways could lead to greater efficacy of immune stimulatory Abs in tumor-bearing individuals.

OX40 (CD134) expression in sentinel lymph nodes correlates with prognostic features of primary melanomas

BACKGROUND

The expression of OX40 (CD134) on activated CD4+ T cells has been associated with favorable cancer patient outcomes. Because of recent reports that sentinel lymph nodes (SLNs) may represent an immunosuppressive environment, we investigated the expression of OX40 in SLNs from patients with primary cutaneous melanoma.

METHODS

Samples of peripheral blood lymphocytes and a section of 71 SLNs from 53 patients with clinically node negative melanoma were purified for CD4+ T cells, stained for OX40, and analyzed by flow cytometry.

RESULTS

The mean percentage of OX40 on CD4 T cells in the SLNs versus peripheral blood lymphocytes was related indirectly to the T stage of the primary tumor and was decreased in ulcerated primary tumors and positive sentinel nodes.

CONCLUSIONS

The expression of OX40 on CD4+ T cells in SLNs draining primary melanomas decreased with more advanced tumor features (higher T stage, ulceration) and nodal involvement, suggesting that such tumors may have an immunosuppressive effect on the SLN microenvironment.

OX40 triggering blocks suppression by regulatory T cells and facilitates tumor rejection

Regulatory T (T reg) cells are the major obstacle to cancer immunotherapy, and their depletion promptly induces conversion of peripheral precursors into T reg cells. We show that T reg cells can be functionally inactivated by OX40 triggering. In tumors, the vast majority of CD4⁺ T cells are Foxp3⁺ and OX40^bright. However, intratumor injection of the agonist anti-OX40 monoclonal antibody (mAb) OX86, but not anti-CD25 mAb, induces tumor rejection in 80% of mice, an effect that is abrogated by CD8 depletion. Upon intratumor OX40 triggering, increased numbers of infiltrating dendritic cells (DCs) migrate to draining lymph nodes and generate a new wave of tumor-specific cytotoxic T lymphocytes, as detected by tetramer and CD44 staining of node CD8⁺ T lymphocytes. Tumor-bearing Rag1-knockout (KO) mice reconstituted with OX40-deficient T reg cells and wild-type (WT) effector T cells, or the reciprocal combination, showed that both T reg and effector T cells must be triggered via OX40 for the tumor to be rejected. Accordingly, WT but not OX40-KO mice receiving intratumor coinjection of OX86 and ovalbumin protein were able to revert tumor-induced tolerization of adoptively transferred OX40-competent OTII T lymphocytes. In conclusion, OX40-mediated inactivation of T reg cell function unleashes nearby DCs, allowing them to induce an adaptive immune response. In addition, the known OX40-dependent delivery of fitness signals to activated T cells is boosted by concurrent T reg cell inhibition. OX40 triggering thus has multiple effects that converge to mediate tumor rejection.

Defects in the acquisition of CD8 T cell effector function after priming with tumor or soluble antigen can be overcome by the addition of an OX40 agonist

Several members of the TNFR superfamily, including OX40 (CD134), 4-1BB (CD137), and CD27 provide critical costimulatory signals that promote T cell survival and differentiation in vivo. Although several studies have demonstrated that OX40 engagement can enhance CD4 T cell responses, the mechanisms by which OX40-mediated signals augment CD8 T cell responses are still unclear. Previously, we and others have shown that OX40 engagement on Ag-specific CD8 T cells led to increased CD8 T cell expansion, survival, and the generation of greater numbers of long-lived memory cells. Currently, we demonstrate that provision of an OX40 agonist during the activation of naive CD8 T cells primed in vivo with either soluble or tumor-associated Ag significantly augments granzyme B expression and CD8 T cell cytolytic function through an IL-2-dependent mechanism. Furthermore, augmented CTL function required direct engagement of OX40 on the responding CD8 T cells and was associated with increased antitumor activity against established prostate tumors and enhanced the survival of tumor-bearing hosts. Thus, in the absence of danger signals, as is often the case in a tumor-bearing host, provision of an OX40 agonist can overcome defective CD8 T cell priming and lead to a functional antitumor response in vivo.

OX40-mediated differentiation to effector function requires IL-2 receptor signaling but not CD28, CD40, IL-12Rbeta2, or T-bet

Ag-specific CD4 T cells transferred into unirradiated Ag-bearing recipients proliferate, but survival and accumulation of proliferating cells is not extensive and the donor cells do not acquire effector functions. We previously showed that a single costimulatory signal delivered by an agonist Ab to OX40 (CD134) promotes accumulation of proliferating cells and promotes differentiation to effector CD4 T cells capable of secreting IFN-gamma. In this study, we determined whether OX40 costimulation requires supporting costimulatory or differentiation signals to drive acquisition of effector T cell function. We report that OX40 engagement drives effector T cell differentiation in the absence of CD28 and CD40 signals. Two important regulators of Th1 differentiation, IL-12R and T-bet, also are not required for acquisition of effector function in CD4 T cells responsive to OX40 stimulation. Finally, we show that CD25-deficient CD4 T cells produce little IFN-gamma in the presence of OX40 costimulation compared with wild type, suggesting that IL-2R signaling is required for efficient OX40-mediated differentiation to IFN-gamma secretion.

Development and characterization of recombinant human Fc:OX40L fusion protein linked via a coiled-coil trimerization domain

OX40 (CD134) is a potent costimulatory molecule found on the surface of activated CD4(+) and CD8(+) T cells. Immunotherapy with OX40 agonists administered in vivo has demonstrated efficacy in several murine tumor models. A phase I clinical trial is currently underway in patients with advanced cancer using a mouse anti-CD134 monoclonal antibody. Therapy with this antibody will likely be limited to one cycle because patients develop neutralizing human anti-mouse antibody (HAMA). Therefore, we developed a humanized OX40 agonist that links the extracellular domain of human OX40L to the Fc domain of human IgG(1) via a trimerizing isoleucine zipper domain (ILZ). Physical characterization by velocity sedimentation revealed that this novel construct, hFcILZOX40L, was assembled into hexamers in which the Fc domains formed three disulfide-bonded dimers and the ILZ-OX40L domains formed two trimers. Trimerization of the ILZ domain was necessary to achieve appropriate assembly. In vitro biologic activity of the hFcILZOX40L hexamer was equivalent to the activity of agonist antibodies in plate-bound assays and was superior when the agonists were tested as soluble agents. Our ultimate goal is to use this recombinant molecule in a future clinical trial, and we feel that the OX40L hexamer will have equivalent or superior agonist activity in vivo when compared to an anti-OX40 antibody.