Abstract 2714: Combination of monalizumab and durvalumab as a potent immunotherapy treatment for solid human cancers

Inhibitory CD94-NKG2A (Natural Killer Group 2A) receptors are expressed on subsets of natural killer (NK) cells, γδ and CD8+ T cells. HLA-E (Human Leukocytes Antigen-E), the ligand for CD94-NKG2A, is upregulated on cancer cells of several solid tumors, providing a negative regulatory signal to tumor-infiltrating lymphocytes (TILs). Blockade of this immune checkpoint pathway with anti-NKG2A monoclonal antibodies (Ab) enhances NK cell responses to tumor cells in vitro and in humanized mice. Here, we describe NK and CD8+ T cell infiltrates in several human solid tumors by immunohistochemistry (IHC) and multicolor flow cytometry. We then studied the effects of in vitro targeting both pathways on primary human NK and CD8+ T cells. By using IHC on formalin-fixed paraffin-embedded samples on cohorts of solid tumors i.e. non-small cell lung cancer (NSCLC, n=45), stomach tumor (n=76), colorectal cancer (CRC, n=103), head and neck tumor (HNSCC, n=68), pancreatic tumors (n=77) and renal cell carcinoma (RCC, n=75), we observed NKp46+ NK cells in the large majority of cancer types (especially in RCC, HNSCC and stomach cancers). CD8+ T cells were found at significantly higher densities in all tumor types. In another cohort of HNSCC samples (n=60), higher proportions of CD94+ lymphocytes were found within the tumor islets both in the primary tumors and in the metastatic lymph nodes. In addition, in CRC patients with liver metastasis (n=101), high CD94+ cell densities were associated with poor overall survival. These data suggest that NKG2A blockade might unleash NK and T cells that are present in close contact to tumor cells. As previously shown, we confirmed that CD94-NKG2A ligand, HLA-E, was expressed by tumor cells in the large majority of solid tumor. In addition, high PD-L1 expressions were observed in NSCLC, stomach tumors, CRC and HNSCC. Flow cytometry analyses revealed that NK and CD8+ T cells co-expressing NKG2A and PD-1 were more numerous in tumor compared to matched peripheral blood and adjacent tissues of NSCLC and HNSCC patients. To mimic the “NKG2A+PD-1+” TILs phenotype, chronic stimulation of peripheral blood cells from healthy volunteers was performed using IL-15. The conditions led to the induction of NKG2A and PD-1 on NK and antigen-specific CD8+ T cell subsets. These effector cells were then co-cultured with tumor cell lines expressing HLA-E +/- PD-L1. We showed that monalizumab, a first-in class anti-NKG2A Ab, combined with durvalumab resulted in higher responses (CD107 mobilization and IFN-γ production) compared to each Ab alone. These data were confirmed in a syngeneic mouse model where both NK and CD8+ T cells were found to be involved in tumor rejection. Together, these data confirm that blocking NKG2A can potentiate the anti-tumor efficacy of PD-1 inhibitors and support the rationale for ongoing clinical trials investigating the monalizumab/durvalumab combination (NCT02671435 and NCT03088059).

Citation Format: Caroline Soulas, Romain Remark, Vedran Brezar, Julie Lopez, Elodie Bonnet, Flavien Caraguel, Ana Lalanne, Caroline Hoffmann, Caroline Denis, Thomas Arnoux, Clarisse Caillet, Arnaud Dujardin, Guillaume Habif, Olivier Lantz, Cécile Bonnafous, Eric Vivier, Pascale Andre. Combination of monalizumab and durvalumab as a potent immunotherapy treatment for solid human cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2714.

Negative modulation of suppressive HIV-specific regulatory T cells by IL-2 adjuvanted therapeutic vaccine

The potential benefit in using IL-2 in immunotherapy for cancer and autoimmunity has been linked to the modulation of immune responses, which partly relies on a direct effect on Tregs populations. Here, we revisited the role of IL-2 in HIV infection and investigated whether its use as an adjuvant with therapeutic vaccination, impacts on HIV-specific responses. Antiretroviral therapy treated-patients were randomized to receive 4 boosts of vaccination (ALVACHIV/Lipo-6T, weeks 0/4/8/12) followed by 3 cycles of IL-2 (weeks 16/24/32) before treatment interruption (TI) at week40. IL-2 administration increased significantly HIV-specific CD4⁺CD25⁺CD134⁺ T-cell responses, which inversely correlated with viral load after TI (r = -0.7, p <0.007) in the vaccine/IL-2 group. IL-2 increased global CD25⁺CD127^lowFoxP3⁺Tregs (p <0.05) while it decreased HIV- but not CMV- specific CD39⁺FoxP3⁺CD25⁺CD134⁺Tregs (p <0.05). HIV-specific Tregs were inversely correlated with IFN-γ producing specific-effectors (p = 0.03) and positively correlated with viral load (r = 0.7, p = 0.01), revealing their undesired presence during chronic infection. Global Tregs, but not HIV-specific Tregs, inversely correlated with a decrease in exhausted PD1⁺CD95⁺ T-cells (p = 0.001). Altogether, our results underline the negative impact of HIV-specific Tregs on HIV-specific effectors and reveal the beneficial use of IL-2 as an adjuvant as its administration increases global Tregs that impact on T-cell exhaustion and decreases HIV-specific CD39⁺Tregs by shifting the balance towards effectors.

Interleukin-2 (IL-2) has been used in immunotherapy for cancer and autoimmunity and its beneficial effect has been linked to the modulation of immune responses, which partly relies on a direct effect on Tregs populations. In this study, we assessed the role of IL-2 in HIV infection and investigated whether its use as an adjuvant with therapeutic vaccination, impacts on HIV-specific responses. We show that IL-2 administration increased HIV-specific CD4⁺CD25⁺CD134⁺ T-cell responses which inversely correlated with viral load after treatment interruption in the vaccine/IL-2 group. We also show that IL-2 increased global CD25⁺CD127^lowFoxP3⁺Tregs while it decreased HIV- but not CMV- specific CD39⁺FoxP3⁺CD25⁺CD134⁺Tregs. Moreover, we show that HIV-specific Tregs were inversely correlated with IFN-γ-producing specific-effectors and positively correlated with viral load. Moreover, we show that global Tregs, but not HIV-specific Tregs, inversely correlated with a decrease in exhausted PD1⁺CD95⁺ T-cells. Altogether, our results underline the negative impact of HIV-specific Tregs on HIV-specific effectors and reveal the beneficial use of IL-2 as an adjuvant as its administration increases global Tregs that impact on T-cell exhaustion and decreases HIV-specific CD39⁺Tregs by shifting the balance towards effectors.

Priming of transcriptional memory responses via the chromatin accessibility landscape in T cells

Memory T cells exhibit transcriptional memory and “remember” their previous pathogenic encounter to increase transcription on re-infection. However, how this transcriptional priming response is regulated is unknown. Here we performed global FAIRE-seq profiling of chromatin accessibility in a human T cell transcriptional memory model. Primary activation induced persistent accessibility changes, and secondary activation induced secondary-specific opening of previously less accessible regions associated with enhanced expression of memory-responsive genes. Increased accessibility occurred largely in distal regulatory regions and was associated with increased histone acetylation and relative H3.3 deposition. The enhanced re-stimulation response was linked to the strength of initial PKC-induced signalling, and PKC-sensitive increases in accessibility upon initial stimulation showed higher accessibility on re-stimulation. While accessibility maintenance was associated with ETS-1, accessibility at re-stimulation-specific regions was linked to NFAT, especially in combination with ETS-1, EGR, GATA, NFκB, and NR4A. Furthermore, NFATC1 was directly regulated by ETS-1 at an enhancer region. In contrast to the factors that increased accessibility, signalling from bHLH and ZEB family members enhanced decreased accessibility upon re-stimulation. Interplay between distal regulatory elements, accessibility, and the combined action of sequence-specific transcription factors allows transcriptional memory-responsive genes to “remember” their initial environmental encounter.

Nuclear PKC-θ facilitates rapid transcriptional responses in human memory CD4+ T cells through p65 and H2B phosphorylation

Memory T cells are characterized by their rapid transcriptional programs upon re-stimulation. This transcriptional memory response is facilitated by permissive chromatin, but exactly how the permissive epigenetic landscape in memory T cells integrates incoming stimulatory signals remains poorly understood. By genome-wide ChIP-sequencing ex vivo human CD4⁺ T cells, here, we show that the signaling enzyme, protein kinase C theta (PKC-θ) directly relays stimulatory signals to chromatin by binding to transcriptional-memory-responsive genes to induce transcriptional activation. Flanked by permissive histone modifications, these PKC-enriched regions are significantly enriched with NF-κB motifs in ex vivo bulk and vaccinia-responsive human memory CD4⁺ T cells. Within the nucleus, PKC-θ catalytic activity maintains the Ser536 phosphorylation on the p65 subunit of NF-κB (also known as RelA) and can directly influence chromatin accessibility at transcriptional memory genes by regulating H2B deposition through Ser32 phosphorylation. Furthermore, using a cytoplasm-restricted PKC-θ mutant, we highlight that chromatin-anchored PKC-θ integrates activating signals at the chromatin template to elicit transcriptional memory responses in human memory T cells.

Summary: Memory T cells have a rapid transcriptional program upon re-stimulation. Chromatin-anchored PKC-θ integrates activating signals at the chromatin template to elicit this transcriptional memory in T cells.

PKC-Theta in Regulatory and Effector T-cell Functions

One of the major goals in immunology research is to understand the regulatory mechanisms that underpin the rapid switch on/off of robust and efficient effector (Teffs) or regulatory (Tregs) T-cell responses. Understanding the molecular mechanisms underlying the regulation of such responses is critical for the development of effective therapies. T-cell activation involves the engagement of T-cell receptor and co-stimulatory signals, but the subsequent recruitment of serine/threonine-specific protein Kinase C-theta (PKC-θ) to the immunological synapse (IS) is instrumental for the formation of signaling complexes, which ultimately lead to a transcriptional network in T cells. Recent studies demonstrated that major differences between Teffs and Tregs occurred at the IS where its formation induces altered signaling pathways in Tregs. These pathways are characterized by reduced recruitment of PKC-θ, suggesting that PKC-θ inhibits Tregs suppressive function in a negative feedback loop. As the balance of Teffs and Tregs has been shown to be central in several diseases, it was not surprising that some studies revealed that PKC-θ plays a major role in the regulation of this balance. This review will examine recent knowledge on the role of PKC-θ in T-cell transcriptional responses and how this protein can impact on the function of both Tregs and Teffs.

Decreased HIV-specific T-regulatory responses are associated with effective DC-vaccine induced immunity

The role of regulatory T cells (Tregs) in vaccination has been poorly investigated. We have reported that vaccination with ex vivo-generated dendritic-cells (DC) loaded with HIV-lipopeptides (LIPO-5-DC vaccine) in HIV-infected patients was well tolerated and highly immunogenic. These responses and their relation to viral replication following analytical treatment interruption (ATI) were variable. Here, we investigated whether the presence of HIV-specific Tregs might explain these differences. Co-expression of CD25, CD134, CD39 and FoxP3 was used to delineate both antigen-specific Tregs and effectors T cells (Teffs). Median LIPO-5 specific-CD25⁺CD134⁺ polyfunctional T cells increased from 0.1% (IQR 0-0.3) before vaccination (week -4) to 2.1% (IQR 1.1-3.9) at week 16 following 4 immunizations (p=0.001) and were inversely correlated with maximum viral load following ATI (r=-0.77, p=0.001). Vaccinees who displayed lower levels of HIV-specific CD4⁺CD134⁺CD25⁺CD39⁺FoxP3⁺ Tregs responded better to the LIPO-5-DC vaccine. After vaccination, the frequency of HIV-specific Tregs decreased (from 69.3 at week -4 to 31.7% at week 16) and inversely correlated with HIV-specific IFN-γ-producing cells (r=-0.64, p=0.002). We show that therapeutic immunization skewed the HIV-specific response from regulatory to effector phenotype which impacts on the magnitude of viral replication following ATI.

Highly active antiretroviral therapy (HAART) has considerably decreased AIDS-related mortality and morbidity in recent years. Nevertheless, the search for effective vaccine to combat HIV is in the limelight of modern medical research. In clinical trial settings, T-cell responses are routinely measured following vaccinations. However, the measurement of antigen-specific regulatory T-cell (Tregs) responses is omitted most of the time, since their detection is not possible with the use of standard assays. Following a phase I clinical trial in which autologous dendritic-cells pulsed with HIV-lipopeptides were used to induce T-cell responses, we used a novel assay to detect a whole range of T-helper responses, including Tregs. We report very high levels of HIV-specific Tregs responses in infected patients and interestingly, we observed that the dendritic cell-based vaccine shifted the responses from regulatory to effector phenotype, which impact on the magnitude of viral rebound after treatment interruption.

A highly relevant and efficient single step method for simultaneous depletion and isolation of human regulatory T cells in a clinical setting

Regulatory T cells (Tregs) are pivotal in preventing autoimmunity. They play a major but still ambiguous role in cancer and viral infections. Functional studies of human Tregs are often hampered by numerous technical difficulties arising from imperfections in isolating and depleting protocols, together with the usual low cell number available from clinical samples. We standardized a simple procedure (Single Step Method, SSM), based on magnetic beads technology, in which both depletion and isolation of human Tregs with high purities are simultaneously achieved. SSM is suitable when using low cell numbers either fresh or frozen from both patients and healthy individuals. It allows simultaneous Tregs isolation and depletion that can be used for further functional work to monitor suppressive function of isolated Tregs (in vitro suppression assay) and also effector IFN-γ responses of Tregs-depleted cell fraction (OX40 assay). To our knowledge, there is no accurate standardized method for Tregs isolation and depletion in a clinical context. SSM could thus be used and easily standardized across different laboratories.

Role of miR-155 in the regulation of lymphocyte immune function and disease

MicroRNAs (miRNAs) have emerged as critical regulators of gene expression within cells. One particular miRNA, miR-155, is highly expressed within lymphocytes (both B and T cells) and mediates a number of important roles. These include shaping the transcriptome of lymphoid cells that control diverse biological functions vital in adaptive immunity. The use of mice engineered to be deficient in miR-155, as well as the identification of endogenous targets of miR-155 in T cells by transcriptome-wide analysis, has helped to unravel the crucial role that this miRNA plays in fine tuning the regulation of lymphocyte subsets such as B cells, CD8(+) and CD4(+) T cells ranging from T helper type 1 (Th1), Th2, Th17 and regulatory T cells. In this review, we summarize what we have learned about miR-155 in the regulation of lymphocyte responses at the cellular and molecular levels and in particular, we focus on the recent findings showing that miR-155 shapes the balance between tolerance and immunity.

Insulin and type 1 diabetes: immune connections

Insulin is the hormone produced by pancreatic β-cells, with a central role in carbohydrate and fat metabolism. Together with its precursors preproinsulin and proinsulin, insulin is also a key target antigen (Ag) of the autoimmune islet destruction leading to type 1 diabetes. Being recognized by both autoantibodies (aAbs) and autoreactive T cells, insulin plays a triggering role, at least in rodent models, in diabetes pathogenesis. It is expressed not only by β-cells but also in the thymus, where it plays a major role in central tolerance mechanisms. We will summarize current knowledge concerning insulin, its role in β-cell autoimmunity as initial target Ag, its recognition by aAbs and autoreactive T cells, and the detection of these immune responses to provide biomarkers for clinical trials employing insulin as an immune modulatory agent.

Short-term subcutaneous insulin treatment delays but does not prevent diabetes in NOD mice

Despite encouraging results in the NOD mouse, type 1 diabetes prevention trials using subcutaneous insulin have been unsuccessful. To explain these discrepancies, 3-week-old NOD mice were treated for 7 weeks with subcutaneous insulin at two different doses: a high dose (0.5 U/mouse) used in previous mouse studies; and a low dose (0.005 U/mouse) equivalent to that used in human trials. Effects on insulitis and diabetes were monitored along with immune and metabolic modifications. Low-dose insulin did not have any effect on disease incidence. High-dose treatment delayed but did not prevent diabetes, with reduced insulitis reappearing once insulin discontinued. This effect was not associated with significant immune changes in islet infiltrates, either in terms of cell composition or frequency and IFN-γ secretion of islet-reactive CD8(+) T cells recognizing the immunodominant epitopes insulin B(15-23) and islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP)(206-214). Delayed diabetes and insulitis were associated with lower blood glucose and endogenous C-peptide levels, which rapidly returned to normal upon treatment discontinuation. In conclusion, high- but not low-dose prophylactic insulin treatment delays diabetes onset and is associated with metabolic changes suggestive of β-cell "rest" which do not persist beyond treatment. These findings have important implications for designing insulin-based prevention trials.

T cells recognizing a peptide contaminant undetectable by mass spectrometry

Synthetic peptides are widely used in immunological research as epitopes to stimulate their cognate T cells. These preparations are never completely pure, but trace contaminants are commonly revealed by mass spectrometry quality controls. In an effort to characterize novel major histocompatibility complex (MHC) Class I-restricted β-cell epitopes in non-obese diabetic (NOD) mice, we identified islet-infiltrating CD8+ T cells recognizing a contaminating peptide. The amount of this contaminant was so small to be undetectable by direct mass spectrometry. Only after concentration by liquid chromatography, we observed a mass peak corresponding to an immunodominant islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP)_206-214 epitope described in the literature. Generation of CD8+ T-cell clones recognizing IGRP_206-214 using a novel method confirmed the identity of the contaminant, further underlining the immunodominance of IGRP_206-214. If left undetected, minute impurities in synthetic peptide preparations may thus give spurious results.

Beyond the hormone: insulin as an autoimmune target in type 1 diabetes

Insulin is not only the hormone produced by pancreatic β-cells but also a key target antigen of the autoimmune islet destruction leading to type 1 diabetes. Despite cultural biases between the fields of endocrinology and immunology, these two facets should not be regarded separately, but rather harmonized in a unifying picture of diabetes pathogenesis. There is increasing evidence suggesting that metabolic factors (β-cell dysfunction, insulin resistance) and immunological components (inflammation and β-cell-directed adaptive immune responses) may synergize toward islet destruction, with insulin standing at the crossroad of these pathways. This concept further calls for a revision of the classical dichotomy between type 1 and type 2 diabetes because metabolic and immune mechanisms may both contribute to different extents to the development of different forms of diabetes. After providing a background on the mechanisms of β-cell autoimmunity, we will explain the role of insulin and its precursors as target antigens expressed not only by β-cells but also in the thymus. Available knowledge on the autoimmune antibody and T-cell responses against insulin will be summarized. A unifying scheme will be proposed to show how different aspects of insulin biology may lead to β-cell destruction and may be therapeutically exploited. We will argue about possible reasons why insulin remains the mainstay of metabolic control in type 1 diabetes but has so far failed to prevent or halt β-cell autoimmunity as an immune modulatory reagent.

Viral infection prevents diabetes by inducing regulatory T cells through NKT cell-plasmacytoid dendritic cell interplay

Type 1 diabetes (T1D) is an autoimmune disease resulting from T cell-mediated destruction of insulin-producing β cells, and viral infections can prevent the onset of disease. Invariant natural killer T cells (iNKT cells) exert a regulatory role in T1D by inhibiting autoimmune T cell responses. As iNKT cell-plasmacytoid dendritic cell (pDC) cooperation controls viral replication in the pancreatic islets, we investigated whether this cellular cross talk could interfere with T1D development during viral infection. Using both virus-induced and spontaneous mouse models of T1D, we show that upon viral infection, iNKT cells induce TGF-β-producing pDCs in the pancreatic lymph nodes (LNs). These tolerogenic pDCs convert naive anti-islet T cells into Foxp3(+) CD4(+) regulatory T cells (T reg cells) in pancreatic LNs. T reg cells are then recruited into the pancreatic islets where they produce TGF-β, which dampens the activity of viral- and islet-specific CD8(+) T cells, thereby preventing T1D development in both T1D models. These findings reveal a crucial cooperation between iNKT cells, pDCs, and T reg cells for prevention of T1D by viral infection.