Establishment of a healthy human range for the whole blood "OX40" assay for the detection of antigen-specific CD4+ T cells by flow cytometry

OX40/OX40 ligand and its role in precision immune oncology

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

Parallel analysis of multiple human memory CD4+ T-cell subsets within antigen-specific responses using cell proliferation dyes

Activation induced marker (AIM) assays are being used increasingly to measure antigen-specific T-cell responses, but this activation can alter cell lineage defining phenotypic markers. We aimed to extend the utility of AIM assays to enable pre-activation defined cell populations to be tracked and quantified within T-cell memory responses. We sorted three ex vivo CD4+ T-cell populations prior to any activation using well defined ex vivo lineage surface marker combinations. These populations were memory non-Tregs, CD39+ Tregs and CD39neg Tregs, although any three memory CD4+ T-cell populations able to be isolated by cell surface markers could potentially be tracked. These cells were labeled with three distinct fluorescent cell proliferation dyes (CFSE, CellTrace Violet and Cell Proliferation Dye eF670) and then all autologous PBMCs were reconstituted maintaining ex vivo cell ratios and CD25/OX40 AIM assays performed with CMV and HSV antigens. This approach enabled tracking of pre-defined cell populations within antigen stimulated responses using both activation marker and cell proliferation readouts. We confirmed that although CD39+ Tregs comprise a substantial proportion of AIM assay responses, they do not make substantial contributions to the proliferative response. This extends the utility of AIM assays to enable parallel analysis of the relative contribution of several CD4+ memory T-cell subsets to recall responses.

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

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

OX40 expression in neutrophils promotes hepatic ischemia/reperfusion injury

Neutrophils play critical roles during the initial phase of hepatic ischemia/reperfusion injury (HIRI). However, the regulation of neutrophil activation, infiltration, and proinflammatory cytokine secretion has not been fully elucidated. In this study, we revealed that OX40 was expressed by neutrophils, its expression in neutrophils was time-dependently upregulated following HIRI, and Ox40 knockout markedly alleviated liver injury. Compared with wild-type neutrophils, the adoptive transfer of Ox40-/- neutrophils decreased HIRI in neutrophil-depleted Rag2/Il2rg-/- or Ox40-/- mice. Moreover, consistently, the in vitro experiments showed that Ox40 not only prolonged neutrophil survival but also promoted proinflammatory cytokines, ROS production, and even neutrophil chemotaxis. Further investigation demonstrated that the knockout of Ox40 in neutrophils inhibited NF-κB signaling via the TRAF1/2/4 and IKKα/IKKβ/IκBα pathways. OX40L and OX86 stimulation could enhance neutrophil activation and survival in vitro and in vivo. In conclusion, our study provides a new understanding of OX40, which is expressed not only in adaptive immune cells but also in innate immune cells, i.e., neutrophils, contributing to the activation and survival of neutrophils. These findings provide a novel potential therapeutic target for the prevention of HIRI during liver transplantation or hepatic surgery.

A new human challenge model for testing heat-stable toxin-based vaccine candidates for enterotoxigenic Escherichia coli diarrhea - dose optimization, clinical outcomes, and CD4+ T cell responses

Enterotoxigenic Escherichia coli (ETEC) are a common cause of diarrheal illness in young children and travelers. There is yet no licensed broadly protective vaccine against ETEC. One promising vaccine development strategy is to target strains expressing the heat-stable toxin (ST), particularly the human ST (STh), since infections with these strains are among the leading causes of diarrhea in children in low-and-middle income countries. A human challenge model based on an STh-only ETEC strain will be useful to evaluate the protective efficacy of new ST-based vaccine candidates. To develop this model, we experimentally infected 21 healthy adult volunteers with the epidemiologically relevant STh-only ETEC strain TW10722, identified a suitable dose, assessed safety, and characterized clinical outcomes and immune responses caused by the infection. Doses of 1×10¹⁰ colony-forming units (CFU) of TW10722 gave a suitable attack risk of 67% for moderate or severe diarrhea and an overall diarrhea attack risk of 78%. Non-diarrheal symptoms were mostly mild or moderate, and there were no serious adverse events. During the first month after ingesting the challenge strain, we measured significant increases in both activated CD4+ T cells and levels of serum IgG and IgA antibodies targeting coli surface antigen 5 (CS5) and 6 (CS6), as well as the E. coli mucinase YghJ. The CS5-specific CD4+ T cell and antibody responses were still significantly elevated one year after experimental infection. In conclusion, we have developed a safe STh-only ETEC-based human challenge model which can be efficiently used in Phase 2B trials to evaluate the protective efficacy of new ST-based vaccine candidates.

Enterotoxigenic Escherichia coli (ETEC) is a common cause of diarrheal illness in young children living in low- and middle-income countries and in travelers to these countries. Several ETEC vaccine candidates are currently being developed, but so far, no broadly protective vaccines have been licensed. Since most moderate and severe ETEC diarrheal episodes are caused by strains that express the heat-stable enterotoxin (ST), ST represents a promising vaccine target. Here we present a human challenge model that can be used to estimate the protective efficacy of ST-based vaccine candidates in clinical vaccine trials. The model is based on the epidemiologically relevant ST-only ETEC strain TW10722, which we show is safe to ingest by volunteers and readily induce diarrhea.

Experimental Infection of Human Volunteers with the Heat-Stable Enterotoxin-Producing Enterotoxigenic Escherichia coli Strain TW11681

Infection with enterotoxigenic Escherichia coli (ETEC) producing the heat-stable enterotoxin (ST) is one of the most important causes of childhood diarrhoea in low- and middle-income countries. Here, we undertook a controlled human infection model (CHIM) study to investigate whether ST-producing ETEC strain TW11681 would be suitable for testing the protective efficacy of new ST-based vaccine candidates in vaccine challenge models. In groups of three, nine volunteers ingested 1 × 10⁶, 1 × 10⁷, or 1 × 10⁸ colony-forming units (CFU) of TW11681. Flow cytometry-based assays were used to measure CD4+ T cell responses and antibody levels targeting virulence factors expressed by the strain. We found that infection with TW11681 elicited few and mild symptoms, including mild diarrhoea in two volunteers, both of whom ingested 1 × 10⁶ CFU. Averaged across all volunteers, the CD4+ T cell responses specific for E. coli YghJ mucinase peaked 10 days after infection (3.2-fold (p = 0.016)), while the CD4+ T cell responses specific for Colonization Factor Antigen I (CFA/I) major fimbrial subunit (CfaB) peaked after 28 days (3.6-fold (p = 0.063)). The serum CfaB-specific anti-IgA and anti-IgG/IgM levels were significantly increased and peaked 3 months after infection. Both remained elevated for the duration of the 12-month follow-up. The corresponding anti-YghJ serological response was strongest after 10 days, although a significant increase was seen only for IgA levels (3.2-fold (p = 0.008)). In conclusion, due to its low diarrhoea attack risk, TW11681 is probably not suitable for testing the efficacy of new vaccines in human challenge studies at doses 1 × 10⁶ to 1 × 10⁸. However, the strain may still be useful in CHIMs for studying ETEC host-pathogen interactions.

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.

A Cytokine-Independent Approach To Identify Antigen-Specific Human Germinal Center T Follicular Helper Cells and Rare Antigen-Specific CD4+ T Cells in Blood

Detection of Ag-specific CD4(+) T cells is central to the study of many human infectious diseases, vaccines, and autoimmune diseases. However, such cells are generally rare and heterogeneous in their cytokine profiles. Identification of Ag-specific germinal center (GC) T follicular helper (Tfh) cells by cytokine production has been particularly problematic. The function of a GC Tfh cell is to selectively help adjacent GC B cells via cognate interaction; thus, GC Tfh cells may be stingy cytokine producers, fundamentally different from Th1 or Th17 cells in the quantities of cytokines produced. Conventional identification of Ag-specific cells by intracellular cytokine staining relies on the ability of the CD4(+) T cell to generate substantial amounts of cytokine. To address this problem, we have developed a cytokine-independent activation-induced marker (AIM) methodology to identify Ag-specific GC Tfh cells in human lymphoid tissue. Whereas Group A Streptococcus-specific GC Tfh cells produced minimal detectable cytokines by intracellular cytokine staining, the AIM method identified 85-fold more Ag-specific GC Tfh cells. Intriguingly, these GC Tfh cells consistently expressed programmed death ligand 1 upon activation. AIM also detected non-Tfh cells in lymphoid tissue. As such, we applied AIM for identification of rare Ag-specific CD4(+) T cells in human peripheral blood. Dengue, tuberculosis, and pertussis vaccine-specific CD4(+) T cells were readily detectable by AIM. In summary, cytokine assays missed 98% of Ag-specific human GC Tfh cells, reflecting the biology of these cells, which could instead be sensitively identified by coexpression of TCR-dependent activation markers.

Combinatorial Immunoprofiling in Latent Tuberculosis Infection. Toward Better Risk Stratification

RATIONALE

Most immunocompetent patients diagnosed with latent tuberculosis infection (LTBI) will not progress to tuberculosis (TB) reactivation. However, current diagnostic tools cannot reliably distinguish nonprogressing from progressing patients a priori, and thus LTBI therapy must be prescribed with suboptimal patient specificity. We hypothesized that LTBI diagnostics could be improved by generating immunomarker profiles capable of categorizing distinct patient subsets by a combinatorial immunoassay approach.

OBJECTIVES

A combinatorial immunoassay analysis was applied to identify potential immunomarker combinations that distinguish among unexposed subjects, untreated patients with LTBI, and treated patients with LTBI and to differentiate risk of reactivation.

METHODS

IFN-γ release assay (IGRA) was combined with a flow cytometric assay that detects induction of CD25(+)CD134(+) coexpression on TB antigen-stimulated T cells from peripheral blood. The combinatorial immunoassay analysis was based on receiver operating characteristic curves, technical cut-offs, 95% bivariate normal density ellipse prediction, and statistical analysis. Risk of reactivation was estimated with a prediction formula.

MEASUREMENTS AND MAIN RESULTS

Sixty-five out of 150 subjects were included. The combinatorial immunoassay approach identified at least four different T-cell subsets. The representation of these immune phenotypes was more heterogeneous in untreated patients with LTBI than in treated patients with LTBI or unexposed groups. Patients with IGRA(+) CD4(+)CD25(+)CD134(+) T-cell phenotypes had the highest estimated reactivation risk (4.11 ± 2.11%).

CONCLUSIONS

These findings suggest that immune phenotypes defined by combinatorial assays may potentially have a role in identifying those at risk of developing TB; this potential role is supported by risk of reactivation modeling. Prospective studies will be needed to test this novel approach.

Identification of a novel mutation in MAGT1 and progressive multifocal leucoencephalopathy in a 58-year-old man with XMEN disease

XMEN disease (X-linked immunodeficiency with Magnesium defect, Epstein-Barr virus infection and Neoplasia) is a novel primary immune deficiency caused by mutations in MAGT1 and characterised by chronic infection with Epstein-Barr virus (EBV), EBV-driven lymphoma, CD4 T-cell lymphopenia, and dysgammaglobulinemia [1]. Functional studies have demonstrated roles for magnesium as a second messenger in T-cell receptor signalling [1], and for NKG2D expression and consequently NK- and CD8 T-cell cytotoxicity [2]. 7 patients have been described in the literature; the oldest died at 45 years and was diagnosed posthumously [1-3]. We present the case of a 58-year-old Caucasian gentleman with a novel mutation in MAGT1 with the aim of adding to the phenotype of this newly described disease by detailing his clinical course over more than 20 years.