Type I Interferon Transcriptional Network Regulates Expression of Coinhibitory Receptors in Human T cells

While inhibition of T cell co-inhibitory receptors has revolutionized cancer therapy, the mechanisms governing their expression on human T cells have not been elucidated. Type 1 interferon (IFN-I) modulates T cell immunity in viral infection, autoimmunity, and cancer, and may facilitate induction of T cell exhaustion in chronic viral infection. Here we show that IFN-I regulates co-inhibitory receptor expression on human T cells, inducing PD-1/TIM-3/LAG-3 while surprisingly inhibiting TIGIT expression. High-temporal-resolution mRNA profiling of IFN-I responses enabled the construction of dynamic transcriptional regulatory networks uncovering three temporal transcriptional waves. Perturbation of key transcription factors on human primary T cells revealed unique regulators that control expression of co-inhibitory receptors. We found that the dynamic IFN-I response in vitro closely mirrored T cell features with IFN-I linked acute SARS-CoV-2 infection in human, with high LAG3 and decreased TIGIT expression. Finally, our gene regulatory network identified SP140 as a key regulator for differential LAG3 and TIGIT expression, which were validated at the level of protein expression. The construction of IFN-I regulatory networks with identification of unique transcription factors controlling co-inhibitory receptor expression may provide targets for enhancement of immunotherapy in cancer, infectious diseases, and autoimmunity.

Tim-3 adaptor protein Bat3 is a molecular checkpoint of T cell terminal differentiation and exhaustion

T cell exhaustion has been associated with poor prognosis in persistent viral infection and cancer. Conversely, in the context of autoimmunity, T cell exhaustion has been favorably correlated with long-term clinical outcome. Understanding the development of exhaustion in autoimmune settings may provide underlying principles that can be exploited to quell autoreactive T cells. Here, we demonstrate that the adaptor molecule Bat3 acts as a molecular checkpoint of T cell exhaustion, with deficiency of Bat3 promoting a profound exhaustion phenotype, suppressing autoreactive T cell-mediated neuroinflammation. Mechanistically, Bat3 acts as a critical mTORC2 inhibitor to suppress Akt function. As a result, Bat3 deficiency leads to increased Akt activity and FoxO1 phosphorylation, indirectly promoting Prdm1 expression. Transcriptional analysis of Bat3 -/- T cells revealed up-regulation of dysfunction-associated genes, concomitant with down-regulation of genes associated with T cell effector function, suggesting that absence of Bat3 can trigger T cell dysfunction even under highly proinflammatory autoimmune conditions.

Abstract IA02: Next targets for immune checkpoint blockade in melanoma

Multiple mechanisms of melanoma-induced immune escape contribute to the failure of T-cell responses to control tumor growth in humans. Many inhibitory pathways play a critical role in impeding T-cell responses to tumor antigens (TAs), including PD-1, the T-cell immunoglobulin and mucin-domain containing-protein 3 (Tim-3), and the T-cell immunoreceptor with Ig and ITIM domains (TIGIT). These inhibitory receptors (IRs) are upregulated by TA-specific CD8+T cells in the tumor microenvironment (TME) while their respective ligands are expressed by antigen-presenting cells (APCs) and tumor cells. Circulating TA-specific CD8+ T cells and CD8+ tumor-infiltrating lymphocytes (TILs) that coexpress PD-1, TIGIT and Tim-3 exhibit different levels of T-cell dysfunction. Dysfunctional/exhausted CD8+ TILs are not totally inert and can exhibit cytolytic functions but are likely kept in check by multiple inhibitory pathways that can be targeted by immune checkpoint blockade. TIGIT is an attractive target for the next-generation immune checkpoint blockade for several reasons. First, it is highly expressed by the majority of CD8+ TILs together with PD-1. Second, the TIGIT ligands, CD155/PVR, and CD112, are highly expressed in the TME by melanoma cells and APCs. Third, dual PD-1/TIGIT blockade augments the expansion and function of human TA-specific CD8+ T cells in vitro and promotes tumor rejection in animal models. Fourth, TIGIT also acts in Tregs and NK cells to regulate antitumor immune responses. CD8+ TILs in melanoma and other solid tumors downregulate the costimulatory molecule DNAM-1/CD226, which competes with TIGIT for binding to the same ligands CD155 and CD112. Therefore, in addition to the TIGIT-mediated T-cell intrinsic inhibitory effects, the downregulation of CD226 expression by CD8+TILs in the TME also contributes to impede T-cell responses to melanoma. Collectively, our findings provide the rationale for dual PD-1/TIGIT blockade together with therapeutic strategies to counteract CD226 downregulation in the TME to improve the clinical benefits of single PD-1 blockade in patients with melanoma and other solid tumors.

Citation Format: Joe-Marc Chauvin, Mignane Ka, Ornella Pagliano, Julien Foucade, Carmine Menna, Diwakar Davar, John Kirkwood, Vijay Kuchroo, Ana Anderson, Alan Korman, Hassane Zarour. Next targets for immune checkpoint blockade in melanoma [abstract]. In: Proceedings of the AACR Special Conference on Melanoma: From Biology to Target; 2019 Jan 15-18; Houston, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(19 Suppl):Abstract nr IA02.

Transcriptomic and Epigenomic Regulation of Leukocytes by the Polyamine Pathway

Cellular metabolism can orchestrate immune cell function. We previously demonstrated that lipid biosynthesis represents one such gatekeeper to Th17 cell functional state, promoting autoimmune responses in the experimental autoimmune encephalomyelitis model. Utilizing a transcriptome-based insilico fluxomics tool, we investigated ancillary metabolic pathways associated with Th17 cell function and studied in detail the relevance of the polyamine pathway as modulators of autoimmune inflammation. We investigated this pathway using carbon-tracing fluxomics, transcriptomics, epigenomics (ATACseq) and functionally validated their relevance in autoimmune disease models using small molecule inhibitors and knockout animals.

Epigenetic and transcriptional mechanisms for the regulation of IL-10

IL-10 is a critical immunoregulatory cytokine expressed in virtually all immune cell types. Maintaining a delicate balance between effective immune response and tolerance requires meticulous and dynamic control of IL-10 expression both epigenetically and transcriptionally. In this Review, we describe the epigenetic mechanisms controlling IL-10 expression, including chromatin remodeling, 3D chromatin loops, histone modification and DNA methylation. We discuss the role of transcription factors in directing chromatin modifications, with a special highlight on the emerging concept of pioneer transcription factors in setting up the chromatin landscape in T helper cells for IL-10 induction. Besides summarizing the recent progress on transcriptional regulation in specialized IL-10 producers such as type 1 regulatory T cells, regulatory B cells and regulatory innate lymphoid cells, we also discuss common transcriptional mechanisms for IL-10 regulation that are shared with other IL-10 producing cells.

Transcriptional regulation of IL-10 in T helper cells

IL-10 produced by CD4 T cells plays an essential role in limiting inflammation and autoimmunity. All T help cell subsets can co-produce IL-10 to mitigate unwanted immunopathology but naïve CD4 T cells can also be directly polarized to IL-10 producing Type 1 regulatory (Tr1) cells by the immunoregulatory cytokine, IL-27. Although several transcription factors (TFs) have been shown to regulate IL-10 expression in different contexts, a comprehensive transcriptional network that induce and maintain IL-10 in various CD4 T cells is lacking.

Here we utilized two complementary approaches to systemically study the transcriptional mechanisms driving IL-10 production in T helper cells: 1) We combined novel computational tools with transcriptomic profiling of in-vitro Tr1 cell differentiation at high temporal resolution to build a comprehensive and dynamic transcriptional network that regulates IL-10 production in CD4 T cells. We identified four transcription waves that govern Tr1 differentiation: dynamic early phase, stable early phase, induction phase and maintenance phase. Based on the network analysis, we computationally predicted 78 TFs that regulate different waves and experimentally validated 24 of them using knock-out mice. 2) To identify TFs associated with IL-10 production across T helper cell subsets, we compared RNA-seq data of IL-10+ versus IL-10− compartments of in-vitro differentiated Th1, Th2 and Th17 cells. Using a comprehensive ranking scheme, we identified two TFs that regulates IL-10 production in all helper T cell subsets. Conditional deletion of both the TFs but not either alone with CD4-Cre abolishes IL-10 production from Tr1 cells in vitro and leads to spontaneous colitis in vivo.

T Helper Cell Cytokines Modulate Intestinal Stem Cell Renewal and Differentiation

In the small intestine, a niche of accessory cell types supports the generation of mature epithelial cell types from intestinal stem cells (ISCs). It is unclear, however, if and how immune cells in the niche affect ISC fate or the balance between self-renewal and differentiation. Here, we use single-cell RNA sequencing (scRNA-seq) to identify MHC class II (MHCII) machinery enrichment in two subsets of Lgr5⁺ ISCs. We show that MHCII⁺ Lgr5⁺ ISCs are non-conventional antigen-presenting cells in co-cultures with CD4⁺ T helper (Th) cells. Stimulation of intestinal organoids with key Th cytokines affects Lgr5⁺ ISC renewal and differentiation in opposing ways: pro-inflammatory signals promote differentiation, while regulatory cells and cytokines reduce it. In vivo genetic perturbation of Th cells or MHCII expression on Lgr5⁺ ISCs impacts epithelial cell differentiation and IEC fate during infection. These interactions between Th cells and Lgr5⁺ ISCs, thus, orchestrate tissue-wide responses to external signals.

Toxicity and Efficacy of a Novel GADD34-expressing Oncolytic HSV-1 for the Treatment of Experimental Glioblastoma

Purpose: Glioblastoma (GBM) is the most common primary central nervous system cancer in adults. Oncolytic HSV-1 (oHSV) is the first FDA-approved gene therapy approach for the treatment of malignant melanoma. For GBM, oHSVs need to be engineered to replicate within and be toxic to the glial tumor but not to normal brain parenchymal cells. We have thus engineered a novel oHSV to achieve these objectives.Experimental Design: NG34 is an attenuated HSV-1 with deletions in the genes encoding viral ICP6 and ICP34.5. These mutations suppress virus replication in nondividing brain neurons. NG34 expresses the human GADD34 gene under transcriptional control of a cellular Nestin gene promoter/enhancer element, whose expression occurs selectively in GBM. In vitro cytotoxicity assay and survival studies with mouse models were performed to evaluate therapeutic potency of NG34 against glioblastoma. In vivo neurotoxicity evaluation of NG34 was tested by intracerebral inoculation.Results: NG34 replicates in GBM cells in vitro with similar kinetics as those exhibited by an oHSV that is currently in clinical trials (rQNestin34.5). Dose-response cytotoxicity of NG34 in human GBM panels was equivalent to or improved compared with rQNestin34.5. The in vivo efficacy of NG34 against two human orthotopic GBM models in athymic mice was similar to that of rQNestin34.5, whereas intracerebral injection of NG34 in the brains of immunocompetent and athymic mice showed significantly better tolerability. NG34 was also effective in a syngeneic mouse glioblastoma model.Conclusions: A novel oHSV encoding GADD34 is efficacious and relatively nontoxic in mouse models of GBM. Clin Cancer Res; 24(11); 2574-84. ©2018 AACR.

SGK1 Governs the Reciprocal Development of Th17 and Regulatory T Cells

A balance between Th17 and regulatory T (Treg) cells is critical for immune homeostasis and tolerance. Our previous work has shown Serum- and glucocorticoid-induced kinase 1 (SGK1) is critical for the development and function of Th17 cells. Here, we show that SGK1 restrains the function of Treg cells and reciprocally regulates development of Th17/Treg balance. SGK1 deficiency leads to protection against autoimmunity and enhances self-tolerance by promoting Treg cell development and disarming Th17 cells. Treg cell-specific deletion of SGK1 results in enhanced Treg cell-suppressive function through preventing Foxo1 out of the nucleus, thereby promoting Foxp3 expression by binding to Foxp3 CNS1 region. Furthermore, our data suggest that SGK1 also plays a critical role in IL-23R-mediated inhibition of Treg and development of Th17 cells. Therefore, we demonstrate that SGK1 functions as a pivotal node in regulating the reciprocal development of pro-inflammatory Th17 and Foxp3+ Treg cells during autoimmune tissue inflammation.

Targeting latency-associated peptide promotes antitumor immunity

Regulatory T cells (T_regs) promote cancer by suppressing antitumor immune responses. We found that anti-LAP antibody, which targets the latency-associated peptide (LAP)/transforming growth factor-β (TGF-β) complex on T_regs and other cells, enhances antitumor immune responses and reduces tumor growth in models of melanoma, colorectal carcinoma, and glioblastoma. Anti-LAP decreases LAP⁺ T_regs, tolerogenic dendritic cells, and TGF-β secretion and is associated with CD8⁺ T cell activation. Anti-LAP increases infiltration of tumors by cytotoxic CD8⁺ T cells and reduces CD103⁺ CD8 T cells in draining lymph nodes and the spleen. We identified a role for CD103⁺ CD8 T cells in cancer. Tumor-associated CD103⁺ CD8 T cells have a tolerogenic phenotype with increased expression of CTLA-4 and interleukin-10 and decreased expression of interferon-γ, tumor necrosis factor-α, and granzymes. Adoptive transfer of CD103⁺ CD8 T cells promotes tumor growth, whereas CD103 blockade limits tumorigenesis. Thus, anti-LAP targets multiple immunoregulatory pathways and represents a potential approach for cancer immunotherapy.

Abstract B085: Combining transcriptomic profiling and genome engineering to dissect regulation of tumor immunology

There is great interest in understanding the dysfunctional state of T-cells during uncontrolled tumor growth, particular regarding the molecular pathways that regulate this functional state for development of potential therapeutic approaches. Here we apply systematic transcriptomic profiling and analysis to dissect the molecular regulation of dysfunctional CD8+ tumor-filtrating lymphocytes (TILs) in a mice melanoma model. We identified key putative regulators and, through combination with precise genome perturbation, established their causal role in driving the dysfunctional phenotype of CD8+ TILs.

Citation Format: Le Cong, Meromit Singer, Chao Wang, John Kwon, Ana Anderson, Orit Rozenblatt-Rosen, Vijay Kuchroo, Aviv Regev. Combining transcriptomic profiling and genome engineering to dissect regulation of tumor immunology [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B085.

NFIL3 and Ets1 co-regulate a cluster of genes, including Tim-3, that is associated with T cell tolerance

Inhibitory receptor Tim-3 has critical roles in the suppression of effector T cell function. Here we demonstrate that the expression of Tim-3 is highly associated with T cell tolerance induction. TCR other than CD28 co-stimulatory signal is required for its induction. This process is accompanied with inhibition of IL-2 but upregulation of IL-10. Among the downstream pathways of TCR signaling, the calcium-calmodulin-dependent Kinase II (CaMKII) pathway is essential for Tim-3, IL-10 induction and IL-2 inhibition. CaMKII directly regulates transcription factors Ets1 and NFIL3. While NFIL3 induces Tim-3, IL-10 and suppresses IL-2 expression, Ets1 plays an opposite role for their expression. Accordingly, functional analyses suggest that NFIL3 is required, but Ets1 actually has an opposite role, in maintaining T cell tolerance/anergy. ChIP-Seq results reveal that NFIL3 and Ets1 co-localize in the loci of Tim-3, IL-2 and IL-10, suggesting a functional cooperation between NFIL3 and Ets1 in the regulation of these genes. We further identified a cluster of genes that has direct binding with both NFIL3 and Ets1. RNA-seq analysis reveals that the expression of these genes is associated with ionomycin-mediated T cell anergy induction. Collectively, our study suggests that NFIL3 and Ets1 cooperatively regulate a transcriptional network to control the expression of a cluster of genes, including Tim-3, IL-10, and IL-2, that is functionally important for T cell tolerance/anergy induction.

Ptpn22 and Cd2 Variations Are Associated with Altered Protein Expression and Susceptibility to Type 1 Diabetes in Nonobese Diabetic Mice

By congenic strain mapping using autoimmune NOD.C57BL/6J congenic mice, we demonstrated previously that the type 1 diabetes (T1D) protection associated with the insulin-dependent diabetes (Idd)10 locus on chromosome 3, originally identified by linkage analysis, was in fact due to three closely linked Idd loci: Idd10, Idd18.1, and Idd18.3. In this study, we define two additional Idd loci—Idd18.2 and Idd18.4—within the boundaries of this cluster of disease-associated genes. Idd18.2 is 1.31 Mb and contains 18 genes, including Ptpn22, which encodes a phosphatase that negatively regulates T and B cell signaling. The human ortholog of Ptpn22, PTPN22, is associated with numerous autoimmune diseases, including T1D. We, therefore, assessed Ptpn22 as a candidate for Idd18.2; resequencing of the NOD Ptpn22 allele revealed 183 single nucleotide polymorphisms with the C57BL/6J (B6) allele—6 exonic and 177 intronic. Functional studies showed higher expression of full-length Ptpn22 RNA and protein, and decreased TCR signaling in congenic strains with B6-derived Idd18.2 susceptibility alleles. The 953-kb Idd18.4 locus contains eight genes, including the candidate Cd2. The CD2 pathway is associated with the human autoimmune disease, multiple sclerosis, and mice with NOD-derived susceptibility alleles at Idd18.4 have lower CD2 expression on B cells. Furthermore, we observed that susceptibility alleles at Idd18.2 can mask the protection provided by Idd10/Cd101 or Idd18.1/Vav3 and Idd18.3. In summary, we describe two new T1D loci, Idd18.2 and Idd18.4, candidate genes within each region, and demonstrate the complex nature of genetic interactions underlying the development of T1D in the NOD mouse model.

Defining the functional states of Th17 cells

The molecular mechanisms governing T helper (Th) cell differentiation and function have revealed a complex network of transcriptional and protein regulators. Cytokines not only initiate the differentiation of CD4 Th cells into subsets but also influence the identity, plasticity and effector function of a T cell. Of the subsets, Th17 cells, named for producing interleukin 17 (IL-17) as their signature cytokine, secrete a cohort of other cytokines, including IL-22, IL-21, IL-10, IL-9, IFNγ, and GM-CSF.  In recent years, Th17 cells have emerged as key players in host defense against both extracellular pathogens and fungal infections, but they have also been implicated as one of the main drivers in the pathogenesis of autoimmunity, likely mediated in part by the cytokines that they produce. Advances in high throughput genomic sequencing have revealed unexpected heterogeneity in Th17 cells and, as a consequence, may have tremendous impact on our understanding of their functional diversity. The assortment in gene expression may also identify different functional states of Th17 cells. This review aims to understand the interplay between the cytokine regulators that drive Th17 cell differentiation and functional states in Th17 cells.

Maresin-1 regulates type 2 innate lymphoid cells and promotes generation of regulatory T cells to limit allergic inflammation (HYP2P.336)

Asthma is a chronic inflammatory disease that fails to resolve and is classically considered to be mediated by an overzealous CD4+Th2 immune response. Recently, a key role for type 2 innate lymphoid cells (ILC2s) was shown to have an important role in the initiation and amplification of allergic inflammation; however, mechanisms for ILC2 regulation remain to be determined. In this study, metabololipidomics of murine lungs identified temporal changes in the endogenous levels of docosahexaenoic acid (DHA)-derived pro-resolving mediator, maresin 1, (MaR1) during self-limited allergic inflammation to ovalbumin (OVA). MaR1 decreased after allergen challenge relative to levels found during sensitization, and subsequently increased during the resolution of inflammation. Exogenous administration of MaR1 reduced lung inflammation and ILC2 expression of IL-5 and IL-13 and increased amphiregulin. MaR1 augmented de novo generation of regulatory T cells (Tregs), which interacted with ILC2s to markedly suppress cytokine production in a TGF-β-dependent manner. Antibody-mediated depletion of Tregs interrupted MaR1 control of ILC2 expression of IL-13 in vivo. These results point to a pivotal role for Tregs in the control of ILC2s in a new proresolving mechanism engaged by MaR1.

Tim-1 is essential for induction and maintenance of IL-10 in regulatory B cells and their regulation of tissue inflammation (IRC11P.435)

T cell Ig and mucin domain (Tim)-1 identifies IL-10-producing regulatory B cells (Bregs). Mice on the C57BL/6 background harboring a loss of function Tim-1 mutant showed progressive loss of IL-10 production in B cells and with age developed severe multi-organ tissue inflammation. We demonstrate that Tim-1 expression and signaling in Bregs are required for optimal production of IL-10. B cells with Tim-1 defects have impaired IL-10 production but increased proinflammatory cytokine production including IL-1 and IL-6. Tim-1-deficient B cells promote Th1 and Th17 responses but inhibit the generation of regulatory T cells (Foxp3+ and IL-10-producing type 1 regulatory T (Tr1) cells) and enhance the severity of experimental autoimmune encephalomyelitis (EAE). Mechanistically, Tim-1 on Bregs is required for apoptotic cell (AC) binding to Bregs and for AC-induced IL-10 production in Bregs. Treatment with AC reduces EAE severity in wildtype (WT) but not Tim-1-deficient Bregs. Collectively, these findings suggest that in addition to serving as a marker for identifying IL-10-producing Bregs, Tim-1 is also critical for maintaining self-tolerance by regulating IL-10 production in Bregs.

KIM-1-mediated phagocytosis reduces acute injury to the kidney

Kidney injury molecule 1 (KIM-1, also known as TIM-1) is markedly upregulated in the proximal tubule after injury and is maladaptive when chronically expressed. Here, we determined that early in the injury process, however, KIM-1 expression is antiinflammatory due to its mediation of phagocytic processes in tubule cells. Using various models of acute kidney injury (AKI) and mice expressing mutant forms of KIM-1, we demonstrated a mucin domain-dependent protective effect of epithelial KIM-1 expression that involves downregulation of innate immunity. Deletion of the mucin domain markedly impaired KIM-1-mediated phagocytic function, resulting in increased proinflammatory cytokine production, decreased antiinflammatory growth factor secretion by proximal epithelial cells, and a subsequent increase in tissue macrophages. Mice expressing KIM-1Δmucin had greater functional impairment, inflammatory responses, and mortality in response to ischemia- and cisplatin-induced AKI. Compared with primary renal proximal tubule cells isolated from KIM-1Δmucin mice, those from WT mice had reduced proinflammatory cytokine secretion and impaired macrophage activation. The antiinflammatory effect of KIM-1 expression was due to the interaction of KIM-1 with p85 and subsequent PI3K-dependent downmodulation of NF-κB. Hence, KIM-1-mediated epithelial cell phagocytosis of apoptotic cells protects the kidney after acute injury by downregulating innate immunity and inflammation.

Specific targeting of the IL-23 receptor, using a novel small peptide noncompetitive antagonist, decreases the inflammatory response

IL-23 is part of the IL-12 family of cytokines and is composed of the p19 subunit specific to IL-23 and the p40 subunit shared with IL-12. IL-23 specifically contributes to the inflammatory process of multiple chronic inflammatory autoimmune disorders, including psoriasis, multiple sclerosis, inflammatory bowel disease, and rheumatoid arthritis. So far, one antibody targeting the shared p40 subunit of IL-12 and IL-23, Ustekinumab, is approved clinically to treat psoriasis. However, there are no treatments inhibiting specifically the IL-23 proinflammatory response. We have developed small IL-23R-specific antagonists by designing all D-peptides arising from flexible regions of IL-23R. Of these peptides, we selected 2305 (teeeqqly), since in addition to its soluble properties, it inhibited IL-23-induced STAT3 phosphorylation in spleen cells. Peptide 2305 specifically binds to IL-23R/IL-12Rβ1-expressing HEK-293 cells and not to cells devoid of the receptor. Peptide 2305 showed functional selectivity by modulating IL-23-induced gene expression in IL-23R/IL-12Rβ1-expressing cells and in Jurkat cells; 2305 does not inhibit IL-12-induced cytokine expression in IL-12Rβ-IL-12Rβ2-HEK-293 cells. Finally, compared with anti-p40 treatment, 2305 effectively and selectively inhibits IL-23-induced inflammation in three in vivo mouse models: IL-23-induced ear inflammation, anti-CD40-induced systemic inflammatory response, and collagen-induced arthritis. We, hereby, describe the discovery and characterization of a potent IL-23R small-peptide modulator, 2305 (teeeqqly), that is effective in vivo. 2305 may be more convenient, less cumbersome, less costly, and most importantly, more specific than current biologics for the treatment of inflammatory conditions, and conceivably complement the actual therapies for these chronic and debilitating inflammatory diseases.

Anti-TIM-4 mediates long-term engraftment of islet allografts by promoting IL-10 expression by TIM-1+ Bregs and inhibiting IFNγ expression by proinflammatory “Be1” B cells (IRC3P.464)

We previously defined TIM-1 as an inclusive marker for IL-10+ regulatory B cells (Bregs). Moreover, α-TIM-1 mAb prolongs islet allograft survival (GS) through induction of TIM-1+ Bregs. We recently noted that TIM-4, a TIM-1 ligand, identifies B cells enriched for IFNγ (Be1). We therefore hypothesized that TIM-4 blockade should also prolong GS and that this may involve B cells. In fact, α-TIM-4 (RMT4-53) treatment resulted in long-term GS in BALB/c recipients of B6 islets (MST >100d). Moreover, α-TIM-4 increases Th2 cytokines (IL-4, IL-10) and Foxp3+Tregs, while reducing both Th1 cytokines (IFNγ) and CD4 proliferation. However, these α-TIM-4-mediated changes and long-term GS were B cell dependent, and did not occur in either B cell deficient (JHD) or depleted (α-CD20) recipients. To address whether α-TIM-4 directly targets (TIM-4+) Be1 cells, we showed that adoptive transfer of WT, but not TIM-4-/- B cells, into μMT recipients, reconstitutes long-term GS mediated by α-TIM-4. We also found that α-TIM-4 inhibits IFNγ expression by TIM-4+ B cells by 40%. Bregs were also required for α-TIM-4 induced transplant tolerance. Transfer of B cells from TIM-1Δmucin (mucin domain deletion) mice, which exhibit a defect in Bregs, is unable to prolong GS in B deficient mice. In wt mice, α-TIM-4 increases TIM-1+ IL-10+ Bregs by ~100%. Taken together, our data reveal that targeting TIM-4 enhances IL-10 expressing Bregs and also reduces inflammatory Be1 B cells to promote allograft tolerance.

PD-1 and Tim-3 regulate the expansion of vaccine-induced tumor antigen-specific CD8+ T cells in patients with advanced melanoma (VAC3P.944)

Although melanoma vaccines stimulate tumor antigen (TA)-specific CD8+ T cells, objective clinical responses are rarely observed. To investigate this discrepancy, we have evaluated vaccine-induced CD8+ T cells for frequency, function and expression of the inhibitory receptors PD-1 and Tim-3 in patients with metastatic melanoma immunized with incomplete Freund’s adjuvant, CpG-oligodeoxynucleotide, and the HLA-A2-restricted analog peptide NY-ESO-1 157-165V either alone, or in combination with the pan-DR epitope NY-ESO-1 119-143. Both vaccines stimulated rapid TA-specific CD8+ T cell responses detected ex vivo, however, TA-specific CD8+ T cells produced more IFN-γ and exhibited higher lytic function upon immunization with MHC class I and class II epitopes. Notably, the vast majority of vaccine-induced CD8+ T cells upregulated PD-1 whereas a minority also upregulated Tim-3 and the levels of PD-1 and Tim-3 expression by vaccine-induced CD8+ T cells at the time of vaccine administration inversely correlated with their expansion in vivo. PD-1 and Tim-3 blockades further enhanced the expansion and cytokine production of vaccine-induced CD8+ T cells in vitro. Collectively, our findings support the use of PD-1 and Tim-3 blockades in addition to cancer vaccines to stimulate potent antitumor T cell responses and increase the likelihood of clinical responses in patients with advanced melanoma.

Tim-3 is expressed by a majority of NK cells at periphery but not at tumor site in patients with advanced melanoma (TUM2P.919)

Tim-3 is a type I glycoprotein expressed by innate and adaptive immune cells. Tim-3 is an inhibitory receptor expressed by dysfunctional tumor antigen-specific CD8+ T cells of patients with advanced melanoma at periphery and in the tumor microenvironment. Tim-3 is also constitutively expressed by functional and mature NK cells in healthy donors (HD). The expression of Tim-3 on NK cells isolated from melanoma patients (MP) and its role in regulating NK functions have not been evaluated yet. To this end, we have investigated Tim-3 expression by NK cells in PBMCs isolated from HD and MP. In sharp contrast with HD, Tim-3 is upregulated by CD56bright as compared to CD56dim NK cells in PBMCs of MP. Upon stimulation with IL-12 and IL-18, NK cells in HD and MP upregulated Tim-3 expression and Tim-3high NK cells produced more IFN-γ than Tim-3neg, suggesting they are more functional. IFN-γ production increased upon NK stimulation with cytokines and Tim-3 ligand Galectin-9 and did not decrease upon Tim-3 blockade. In contrast to circulating NK cells, tumor-infiltrating NK cells (TINKs) are CD56dim in their large majority (> 98%), and exhibit lower levels of Tim-3 expression. Collectively, our data show that Tim-3 is expressed by a majority of functional circulating NK cells in HD and MP but only a minority of TINK cells, suggesting that TINK may be less functional than their peripheral counterpart.

T cell-derived interleukin (IL)-21 promotes brain injury following stroke in mice

T lymphocytes are key contributors to the acute phase of cerebral ischemia reperfusion injury, but the relevant T cell-derived mediators of tissue injury remain unknown. Using a mouse model of transient focal brain ischemia, we report that IL-21 is highly up-regulated in the injured mouse brain after cerebral ischemia. IL-21-deficient mice have smaller infarcts, improved neurological function, and reduced lymphocyte accumulation in the brain within 24 h of reperfusion. Intracellular cytokine staining and adoptive transfer experiments revealed that brain-infiltrating CD4(+) T cells are the predominant IL-21 source. Mice treated with decoy IL-21 receptor Fc fusion protein are protected from reperfusion injury. In postmortem human brain tissue, IL-21 localized to perivascular CD4(+) T cells in the area surrounding acute stroke lesions, suggesting that IL-21-mediated brain injury may be relevant to human stroke.

The dichotomous pattern of IL-12r and IL-23R expression elucidates the role of IL-12 and IL-23 in inflammation

IL-12 and IL-23 cytokines respectively drive Th1 and Th17 type responses. Yet, little is known regarding the biology of these receptors. As the IL-12 and IL-23 receptors share a common subunit, it has been assumed that these receptors are co-expressed. Surprisingly, we find that the expression of each of these receptors is restricted to specific cell types, in both mouse and human. Indeed, although IL-12Rβ2 is expressed by NK cells and a subset of γδ T cells, the expression of IL-23R is restricted to specific T cell subsets, a small number of B cells and innate lymphoid cells. By exploiting an IL-12- and IL-23-dependent mouse model of innate inflammation, we demonstrate an intricate interplay between IL-12Rβ2 NK cells and IL-23R innate lymphoid cells with respectively dominant roles in the regulation of systemic versus local inflammatory responses. Together, these findings support an unforeseen lineage-specific dichotomy in the in vivo role of both the IL-12 and IL-23 pathways in pathological inflammatory states, which may allow more accurate dissection of the roles of these receptors in chronic inflammatory diseases in humans.

Immunology of neuromyelitis optica: a T cell-B cell collaboration

Neuromyelitis optica (NMO) is a debilitating autoimmune inflammatory disease of the central nervous system (CNS) that is distinct from multiple sclerosis (MS). The discovery of NMO-immunoglobulin G (IgG) in the serum of NMO-but not MS-patients was a breakthrough in defining diagnostic criteria for NMO. NMO-IgG is an antibody directed against the astrocytic water channel protein aquaporin-4 (AQP4). While there is evidence that NMO-IgG is also involved in mediating tissue damage in the CNS, many aspects of the pathogenic cascade in NMO remain to be determined. It is clear that antigen-specific T cells contribute to the generation of NMO-IgG in the peripheral immune compartment, as well as to the development of NMO lesions in the CNS. T helper 17 (Th17) cells, equipped both in providing B cell help and inducing tissue inflammation, may be involved in NMO development and pathogenesis. Here, we review immunologic aspects of NMO, placing recent findings in the biology of T-B cell cooperation into perspective with autoimmunity of the CNS.

Chemical inhibition of the RORγt-dependent transcriptional network in Th17 cells (P5163)

RORγt is a master transcription factor required for Th17 development. We identified two novel RORγt-specific inhibitors that suppress Th17 response and Th17-mediated autoimmune disease. To assess their mechanisms of action, we systemically characterize their function within the context of RORγt-directed transcriptional circuitry by integrating RORγt binding data in the presence and absence of drug with corresponding whole-transcriptome sequencing for wildtype and RORγt-deficient cells. RORγt is central in a densely interconnected regulatory network, acting both as a direct activator of genes important for Th17 differentiation and as a direct inhibitor of genes from other T-cell lineages. These inhibitors reversed both of these modes of action, but to varying extents and through distinct mechanisms. While one inhibitor displaced RORγt from its target-loci, the more potent inhibitor affected transcription predominantly without removing DNA-binding. Our work illustrates the power of a system-scale analysis of transcriptional regulation to characterize potential therapeutic compounds that inhibit pathogenic Th17 cells and suppress autoimmunity.

IRF-1 is a key transcriptional regulator of Tr1 differentiation (P1135)

IL-10 producing Type 1 regulatory T cells (Tr1) are crucial for maintenance of peripheral tolerance and prevention of autoimmune inflammation. Using IL-27 as the differentiation factor, we undertook a detailed whole genome transcriptional network analysis of differentiating Tr1 cells. We identified IRF-1 as a key transcriptional regulator of Tr1 differentiation. Our studies demonstrate a critical requirement for IRF1 in the generation of Tr1 cells both in vitro and in vivo. IRF1-/- mice immunized for the development of Experimental autoimmune encephalomyelitis (EAE) develop very severe clinical disease and fail to recover. Furthermore, CD4+ T cells in IRF1-deficient mice with active disease showed increased number of IL-17 secreting cells in the CNS. In fact, over-expression of IRF1 during Th17 differentiation suppresses induction of both IL17 and IL23 receptor, the role opposite to the one played by another IRF family member - IRF4. Interestingly, loss of IRF-1 enhances IRF4 binding to the key DNA-binding sites involved in Th17 differentiation and functional assays further support that IRF1 can actively repress IRF4-mediated transactivation of IL17A, pointing to a cross-competition of IRF1 and IRF4 for the same DNA-binding sites in CD4+ T cells. Collectively these data demonstrate a critical role of IRF-1 in the generation of Tr1 cells, but at the same time, the induction of IRF-1 represses Th17 differentiation by actively inhibiting IRF-4 mediated Th17 differentiation.

Induction of pathogenic Th17 cells by inducible salt sensing kinase SGK1 (P1145)

Th17 cells are highly proinflammatory cells that are critical for clearing extracellular pathogens and induction of multiple autoimmune diseases. IL-23 plays a critical role in stabilizing and endowing Th17 cells with pathogenic effector functions. IL-23 has been shown to reinforce the Th17 phenotype by increasing expression of IL-23 receptor (IL-23R). However, the molecular mechanism by which IL-23 sustains the Th17 response and induces pathogenic effector functions is unclear. Here we used unbiased transcriptional profiling of developing Th17 cells to construct a model of their signaling network and identify major nodes that regulate Th17 development. We identified serum glucocorticoid kinase-1 (SGK1) is critical for regulating IL-23R expression and for stabilizing the Th17 cell by deactivation of Foxo1, a direct repressor of IL-23R expression. SGK1 has been shown to govern Na+ transport and homeostasis. We show that a modest increase in salt (NaCl) concentration induces SGK1 expression, promotes IL-23R expression and enhances Th17 cell differentiation in vitro and in vivo, ultimately accelerating the development of autoimmunity. The loss of SGK1 resulted in abrogation of Na+-mediated Th17 differentiation in an IL-23-dependent manner. These data indicate that SGK1 is critical for the induction of pathogenic Th17 cells and provides a molecular insight by which an environmental factor such as a high salt diet could trigger Th17 development and promote tissue inflammation.

Brief report: increased expression of a short splice variant of CTLA-4 exacerbates lupus in MRL/lpr mice

OBJECTIVE

CTLA-4 is a negative regulator of the immune response expressed by regulatory T (Treg) cells and activated T cells. Polymorphisms in the CTLA4 gene have been associated with autoimmune diseases, including systemic lupus erythematosus. Disease-associated polymorphisms have been shown to affect the production of the different CTLA-4 variants through an effect on alternative splicing. This study was undertaken to evaluate the role of the 1/4 CTLA-4 isoform in lupus-prone mice.

METHODS

We generated an MRL/lpr mouse strain that transgenically overexpresses a short isoform of CTLA-4 (1/4 CTLA-4) by backcrossing C57BL/6.1/4CTLA-4-transgenic mice to the MRL/lpr strain for 9 generations. A new antibody was generated to detect the expression of the 1/4 CTLA-4 isoform. Routine methods were used to evaluate kidney damage, humoral immunity, and cellular immunity.

RESULTS

Expression of the 1/4 CTLA-4 isoform accelerated autoimmune disease. Transgenic mice died earlier, had more severe renal disease, and had higher titers of anti-double-stranded DNA antibodies than wild-type MRL/lpr mice. The acceleration of autoimmunity and disease pathology associated with the presence of the short (1/4) isoform of CTLA-4 was linked to increased numbers of activated T cells and B cells and heightened interferon-γ production, but not to altered expression of the full-length CTLA-4 molecule or Treg cell numbers.

CONCLUSION

Our results indicate that the presence of the alternatively spliced 1/4 CTLA-4 isoform can further promote autoimmunity and autoimmune pathology in lupus-prone mice and suggest that altered splicing of CTLA4 contributes to the expression of autoimmune disease.

Podoplanin-rich stromal networks induce dendritic cell motility via activation of the C-type lectin receptor CLEC-2

To initiate adaptive immunity, dendritic cells (DCs) move from parenchymal tissues to lymphoid organs by migrating along stromal scaffolds that display the glycoprotein podoplanin (PDPN). PDPN is expressed by lymphatic endothelial and fibroblastic reticular cells and promotes blood-lymph separation during development by activating the C-type lectin receptor, CLEC-2, on platelets. Here, we describe a role for CLEC-2 in the morphodynamic behavior and motility of DCs. CLEC-2 deficiency in DCs impaired their entry into lymphatics and trafficking to and within lymph nodes, thereby reducing T cell priming. CLEC-2 engagement of PDPN was necessary for DCs to spread and migrate along stromal surfaces and sufficient to induce membrane protrusions. CLEC-2 activation triggered cell spreading via downregulation of RhoA activity and myosin light-chain phosphorylation and triggered F-actin-rich protrusions via Vav signaling and Rac1 activation. Thus, activation of CLEC-2 by PDPN rearranges the actin cytoskeleton in DCs to promote efficient motility along stromal surfaces.

Tim-3 expression and function in natural killer cells from advanced melanoma patients

8571

Background: The concept of CD8+ T cell exhaustion in the context of metastatic cancer has been reinforced by the recent success of immunotherapies targeting the exhaustion markers CTLA-4 and PD-1 in advanced melanoma. T-cell immunoglobulin 3 (Tim-3), another exhaustion marker, is also expressed in natural killer (NK) cells, however its role is still unknown. Recent reports have shown that NK cells, innate immune cells that eliminate tumors through cytotoxicity and IFN-g production, are functionally impaired in advanced melanoma patients, although no receptor has been linked with that phenotype so far. In this study, we characterize the role of Tim-3 in NK cells, particularly in the presence of its natural ligand, Galectin-9 (Gal-9), that is known to be expressed/secreted by some tumor cells including melanoma. Methods: We compared 20 advanced melanoma donors NK cells with 40 healthy donors NK cells as it relates to Tim-3 expression (by flow cytometry) and function (cytotoxicity, IFN-γ production and proliferation). NK cells cytotoxicity was measured by lamp-1 expression, and two different target cells were used: i) K562 cells (Gal-9-) and ii) Gmel Gal-9+ and Gmel Gal-9- sorted melanoma cells. Proliferation was quantified by CFSE after 6 days in the presence of rhIL-2. Recombinant rhGal9 effect was tested in cytotoxicity and IFN-γ production. Results: Melanoma patients NK cells express higher levels of Tim-3 compared to healthy donors NK cells (p<0.05). Melanoma patients NK cells have a defect in cytotoxicity, proliferation and IFN-γ production. Tim-3 expression by itself (without engagement of specific ligands) does not negatively affect NK cell functions (p<0.05). However, when rhGal9 is added to the system, a decrease in NK cell cytotoxicity and IFN-γ production (p<0.05) was observed. Finally, the expression of Gal-9 by the target cells induces a defect in NK cell cytotoxicity (Gmel Gal-9+ vs Gmel Gal-9-). Conclusions: These data suggest that advanced melanoma patients NK cells are exhausted, although it still remains unclear if Tim-3 is involved in this phenotype. In addition,the expression/secretion of Galectin-9, immunosuppressive for NK cells, may be a possible mechanism for tumors to evade immune surveillance.

Induced-tolerogenic Dendritic Cells promote tolerance and de novo differentiation of regulatory T cells (65.6)

Tolerance towards specific antigens is achieved by elimination of reactive T cells and/or their differentiation into regulatory T cells (Tregs). We screened several cell culture conditions known to confer potent tolerogenic capacity on Dendritic Cells (DC) in an attempt to obtain antigen-presenting cells that eliminate naïve CD4+ T cells (Tn) or induce Foxp3 expression, the master regulator of Treg differentiation and function. We identified Rapamycin and TGFβ as key factors that imprint DCs with strong tolerogenic function. TCR stimulation of Tn by these induced-tolerogenic DC (itDC) results in the selective reduction of antigen specific cells and the upregulation of Foxp3 expression in the remaining cells. The resulting adaptive regulatory T cells (aTregs) express high levels of CD25, GITR, CD152, CD62L and suppress T cell responses in vitro. Interestingly, aTreg differentiation induced by itDC was cell contact-dependent and occurred in absence of IL-10, TGFβ, IDO1 and FasL. In vivo injection of itDCs at the first clinical signs of MOG-induced Experimental Autoimmune Encephalomyelitis (EAE, Day 12) completely blocks the progress of the disease. Finally, monocyte-derived human itDC also induced sustained Foxp3 expression in human T cells that display suppressive function. These results suggest that itDCs may be a valuable tool to induce antigen-specific tolerance in vivo and represent a potential novel therapy for autoimmune disorders.

Tim3/Galectin-9 interactions regulate innate and adaptive immunity to Mycobacterium tuberculosis (70.6)

In vivo control of Mycobacterium tuberculosis (Mtb) reflects the balance between host-immunity and bacterial evasion strategies. Effector TH1 cells that mediate protective immunity by depriving the bacterium of its intracellular niche are regulated in many ways to prevent over-exuberant inflammation. Although Tim3 is generally recognized to down regulate TH1 responses and mediate T cell exhaustion, we recently described that its interaction with Galectin-9 (Gal9) expressed by Mtb infected macrophages (Mϕ) stimulates IL-1β secretion, which is essential for host resistance to Mtb. IL-1β signaling is both necessary for Tim3 mediated Mtb control and sufficient to directly kill Mtb in murine and human Mϕ. The molecular mechanism by which IL-1β restricts bacterial growth is not known. We report that IL-1β kills Mtb through the recruitment of other antimicrobial effector molecules. IL-1β directly augments TNF signaling through increased TNF secretion and TNFR cell surface expression. Furthermore, Tim3/Gal9 and IL-1β activates the executioner caspase-3. Thus, Tim3/Gal9, via IL-1β and downstream TNF production lead to apoptosis and restriction of intracellular Mtb growth. We propose that Tim3/Gal9 interaction acts as a bidirectional molecular rheostat that activates pathways to clear intracellular pathogens in innate immune cells while fine-tuning termination of TH1 responses to prevent immunopathology.

High salt induces pathogenic Th17 cells and exacerbates autoimmune diseases (60.13)

Interleukin (IL)-17 producing CD4+ helper T cells (Th17 cells) play a pivotal role in autoimmune diseases. Apart from their importance for the control of certain pathogens, IL-23 dependent Th17 cells have been shown to be critical for the development of experimental autoimmune encephalomyelitis (EAE). Moreover, genetic risk factors associated with multiple sclerosis (MS) are linked to the IL23/Th17 pathway. Besides genetic factors, the increased incidence of autoimmune diseases like MS in developed countries is also believed to be related to environmental risk factors. However, how environmental risk factors such as changes in diet, sun exposure or medications could directly influence the development of pathogenic Th17 cells is not well established. Here we show that increased salt (sodium chloride; NaCl) concentrations dramatically boost the induction of murine and human Th17 cells in vitro. Moreover, mice fed with a high salt diet develop a very severe form of EAE, dependent on the induction of highly pathogenic Th17 cells. The generation of Th17 cells under high salt conditions is well regulated on the molecular level and seems to be dependent on specific pathways. Thus, increased salt intake, which may represents one of the biggest contributors to changes in diet during the last half century and accounts for cardiovascular disease, might also represent an environmental risk factor for autoimmune diseases through the exacerbated induction of pathogenic Th17 cells.

The upregulation of the inhibitory receptors BTLA and PD-1 defines a novel subset of dysfunctional tumor antigen-specific CD8+ T cells (127.19)

Cytotoxic T cells present at the periphery or at tumor sites recognize tumor epitopes presented by melanoma cells but fail to induce tumor rejection in melanoma patients. Inhibitory receptors including PD-1 and Tim-3 expressed by spontaneous CD8+ T cells directed against the cancer-germline antigen NY-ESO-1 play a role in promoting tumor-induced T cell dysfunction. In the present study, we show that BTLA is upregulated on spontaneous NY-ESO-1-specific CD8+ T cells and that BTLA-expressing PD-1+Tim-3- CD8+ T cells represent the largest subset of NY-ESO-1-specific CD8+ T cells in melanoma patients. These cells were partially dysfunctional, producing less IFN-γ than BTLA- T cells, but more IFN-γ, TNF and IL-2 than the highly dysfunctional subset expressing all three receptors. Unlike PD-1, BTLA expression by NY-ESO-1-specific CD8+ T cells does not increase with higher T cell dysfunction or upon cognate antigen stimulation, suggesting that BTLA upregulation occurs independently of functional exhaustion driven by high antigen load. Finally, BTLA blockade adds to PD-1 and Tim-3 blockades, enhancing NY-ESO-1-specific CD8+ T cell expansion, proliferation and cytokine production. Collectively, our findings support the targeting of BTLA, PD-1 and Tim-3 pathways to reverse tumor-induced T cell dysfunction in patients with advanced melanoma.

FoxP3+Tim-3+ Tregs are site-specific suppressors supporting tumor growth by influencing the functional phenotype of tumor-infiltrating lymphocytes (46.5)

In prior studies, we and others have found Tim-3 to be expressed on exhausted CD8+ tumor infiltrating lymphocytes (TILs). It was shown that anti-Tim-3 antibody treatment together with anti-PD-1/PD-L1 antibody could abrogate tumor growth and effectively restore T cell effector function to exhausted CD8+ T cells (Sakuishi et al 2010, Fourcade et al 2010, Zhou et al 2011, Ngiow et al 2011). Tim-3 is also expressed on CD4+ TILs but its role in tumor immunity has not been addressed. We have found that the majority of FoxP3+ TILs express Tim-3 in multiple tumor models. Kinetic studies in B16F10 melanoma show that the accumulation of FoxP3+Tim3+ cells parallels tumor growth. Interestingly, this accumulation of FoxP3+Tim-3+ cells is not observed in either the tumor draining lymph node or spleen of tumor-bearing mice, indicating site-specific expansion. FoxP3+Tim-3+ cells are higher producers of IL-10 and are more efficient in suppressing FoxP3- effector T cells in vitro when compared to FoxP3+Tim-3- cells. Depleting FoxP3+ regulatory T cells (Tregs) from established B16 melanoma results in tumor regression and modulation of Tim-3 expression on both FoxP3- CD4 and CD8 TILs. Furthermore, Treg depletion influences the development of exhausted phenotype in CD8+ TILs. This is the first report revealing that the Tim-3+ subset of Tregs predominates within tumor and plays an important role in tumor progression in situ by regulating the functional phenotype of FoxP3- CD4+ and CD8+ TILs.

Abstract 5407: The upregulation of BTLA and PD-1 defines a novel subset of dysfunctional tumor antigen-specific CD8+ T cells

Cytotoxic T cells present at the periphery or at tumor sites recognize tumor epitopes presented by melanoma cells but fail to induce tumor rejection in melanoma patients. Inhibitory receptors including PD-1 and Tim-3 expressed by spontaneous CD8+ T cells directed against the cancer-germline antigen NY-ESO-1 play a role in promoting tumor-induced T cell dysfunction. In the present study, we show that BTLA is upregulated on spontaneous NY-ESO-1-specific CD8+ T cells and that BTLA+PD-1+Tim-3− CD8+ T cells represent the largest subset of NY-ESO-1-specific CD8+ T cells in melanoma patients. BTLA+PD-1+Tim-3− CD8+ T cells are partially dysfunctional, producing less IFN-γ than BTLA−PD-1+Tim-3− and BTLA−PD-1−Tim-3− but more IFN-γ, TNF and IL-2 than highly dysfunctional BTLA+PD-1+Tim-3+ NY-ESO-1-specific CD8+ T cells. Unlike PD-1, BTLA expression by NY-ESO-1-specific CD8+ T cells does not increase with higher T cell dysfunction or upon cognate antigen stimulation, suggesting that BTLA upregulation occurs independently of functional exhaustion driven by high antigen load. Finally, BTLA pathway blockade adds to PD-1 and Tim-3 blockades, enhancing NY-ESO-1-specific CD8+ T cell expansion, proliferation and cytokine production. Collectively, our findings support the targeting of BTLA, PD-1 and Tim-3 pathways to reverse tumor-induced T cell dysfunction in patients with advanced melanoma. This work was supported by the National Institutes of Health/National Cancer Institute grants R01CA90360 and R01CA157467 (to H.M. Zarour), an award from the Melanoma Skin Spore grant NCI P50CA121973 (to H.M. Zarour) and a grant from the Cancer Research Institute (to H.M. Zarour).

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5407. doi:1538-7445.AM2012-5407

The TIGIT/CD226 axis regulates human T cell function

T cell Ig and ITIM domain (TIGIT) is a newly identified receptor expressed on T cells that binds to CD155 on the dendritic cell surface, driving them to a more tolerogenic phenotype. Given that TIGIT contains an ITIM motif in its intracellular domain and considering the potential importance of the TIGIT/CD226 pathway in human autoimmune disease, we investigated the specific role of TIGIT in human CD4(+) T cells. Using an agonistic anti-TIGIT mAb, we demonstrate a direct inhibitory effect on T cell proliferation with a decrease in expression of T-bet, GATA3, IFN regulatory factor 4, and retinoic acid-related orphan receptor c with inhibition of cytokine production, predominantly IFN-γ. Knockdown of TIGIT expression by short hairpin RNA resulted in an increase of both T-bet and IFN-γ mRNA and protein expression with concomitant decrease in IL-10 expression. Increases in IFN-γ with TIGIT knockdown could be overcome by blocking CD226 signaling, indicating that TIGIT exerts immunosuppressive effects by competing with CD226 for the same CD155 ligand. These data demonstrate that TIGIT can inhibit T cell functions by competing with CD226 and can also directly inhibit T cells in a T cell-intrinsic manner. Our results provide evidence for a novel role of this alternative costimulatory pathway in regulating human T cell responses associated with autoimmune disease.

CD8(+) T cells specific for tumor antigens can be rendered dysfunctional by the tumor microenvironment through upregulation of the inhibitory receptors BTLA and PD-1

Cytotoxic T cells that are present in tumors and capable of recognizing tumor epitopes are nevertheless generally impotent in eliciting tumor rejection. Thus, identifying the immune escape mechanisms responsible for inducing tumor-specific CD8(+) T-cell dysfunction may reveal effective strategies for immune therapy. The inhibitory receptors PD-1 and Tim-3 are known to negatively regulate CD8(+) T-cell responses directed against the well-characterized tumor antigen NY-ESO-1. Here, we report that the upregulation of the inhibitory molecule BTLA also plays a critical role in restricting NY-ESO-1-specific CD8(+) T-cell expansion and function in melanoma. BTLA-expressing PD-1(+)Tim-3(-) CD8(+) T cells represented the largest subset of NY-ESO-1-specific CD8(+) T cells in patients with melanoma. These cells were partially dysfunctional, producing less IFN-γ than BTLA(-) T cells but more IFN-γ, TNF, and interleukin-2 than the highly dysfunctional subset expressing all three receptors. Expression of BTLA did not increase with higher T-cell dysfunction or upon cognate antigen stimulation, as it does with PD-1, suggesting that BTLA upregulation occurs independently of functional exhaustion driven by high antigen load. Added with PD-1 and Tim-3 blockades, BTLA blockade enhanced the expansion, proliferation, and cytokine production of NY-ESO-1-specific CD8(+) T cells. Collectively, our findings indicate that targeting BTLA along with the PD-1 and Tim-3 pathways is critical to reverse an important mechanism of immune escape in patients with advanced melanoma.

Abstract 3657: Upregulation of PD-1 and Tim-3 expression on tumor antigen-specific CD4+ T cells is associated with reversible T cell dysfunction in patients with advanced melanoma

The paradoxical coexistence of spontaneous tumor antigen-specific immune T cell responses with progressive disease in cancer patients furthers the need to dissect the molecular pathways involved in tumor-induced T cell dysfunction and exhaustion. We have previously observed in patients with advanced melanoma that the cancer-germline antigen NY-ESO-1 stimulates spontaneous NY-ESO-1-specific CD8+ T cells that upregulate PD-1 expression and that a fraction of PD-1+ NY-ESO-1-specific CD8+ T cells upregulates Tim-3 expression. We have found that Tim-3+PD-1+ NY-ESO-1-specific CD8+ T cells represent highly dysfunctional T cells in terms of cytokine production and proliferation. Importantly, Tim-3/Tim-3L blockade together with PD-1/PD-L1 blockade enhanced cytokine production and proliferation of NY-ESO-1-specific CD8+ T cells upon prolonged antigen stimulation. Whether the upregulation of PD-1 and Tim-3 is associated with tumor antigen-specific CD4+ T cell dysfunction/exhaustion in patients with advanced melanoma remains unknown. Here, our findings show that in contrast to EBV-specific, CMV-specific and total CD4+ T cells, PD-1 and Tim-3 expression is upregulated by NY-ESO-1-specific CD4+ T cells isolated from peripheral blood lymphocytes of patients with advanced melanoma. Interestingly, PD-1/PD-L1 blockade synergized with Tim-3/Tim-3L pathway blockade to restore the numbers of cytokine-producing and proliferating NY-ESO-1-specific CD4+ T cells. Collectively, our findings support the use of Tim-3/Tim-3L blockade in association with PD-1/PD-L1 blockade to reverse tumor-induced CD8+ and CD4+ T cell exhaustion/dysfunction in patients with advanced melanoma. Our findings have significant implication in terms of novel immunotherapeutic strategies aiming at promoting T cell-mediated tumor regression in patients with advanced cancers.

This work was supported by NIH/NCI Grants CA90360 and CA112198 (HMZ) and Cancer Research Institute grant (HMZ).

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3657. doi:10.1158/1538-7445.AM2011-3657

Targeting PD-1 and Tim-3 pathways to reverse tumor antigen-specific CD4+ T cell dysfunction in patients with advanced melanoma (66.1)

The coexistence of spontaneous tumor antigen-specific immune T cell responses with progressive disease in cancer patients furthers the need to dissect the molecular pathways involved in tumor-induced T cell dysfunction and exhaustion. We have previously observed in patients with advanced melanoma that NY-ESO-1-specific CD8+ T cells upregulate PD-1 and a fraction of PD-1+ NY-ESO-1-specific CD8+ T cells upregulates Tim-3. We have found that Tim-3+PD-1+ NY-ESO-1-specific CD8+ T cells represent highly dysfunctional T cells. Importantly, Tim-3 and PD-1 pathway blockades synergized to enhance immune functions of NY-ESO-1-specific CD8+ T cells upon prolonged antigen stimulation. Whether the upregulation of PD-1 and Tim-3 is associated with tumor antigen-specific CD4+ T cell dysfunction remains unknown. Here, our findings in advanced melanoma patients show that in contrast to virus-specific and total CD4+ T cells, PD-1 and Tim-3 expression is upregulated by NY-ESO-1-specific CD4+ T cells. Interestingly, PD-1 and Tim-3 pathway blockades synergized to restore the numbers of cytokine-producing and proliferating NY-ESO-1-specific CD4+ T cells. Collectively, our findings support the use of Tim-3 and PD-1 pathway blockades to reverse tumor-induced CD8+ and CD4+ T cell exhaustion in patients with advanced melanoma. Our findings have significant implication in terms of novel immunotherapeutic strategies aiming at promoting T cell-mediated tumor regression in patients with advanced cancers.

Upregulation of Tim-3 and PD-1 expression is associated with tumor antigen-specific CD8+ T cell dysfunction in melanoma patients

The paradoxical coexistence of spontaneous tumor antigen-specific immune responses with progressive disease in cancer patients furthers the need to dissect the molecular pathways involved in tumor-induced T cell dysfunction. In patients with advanced melanoma, we have previously shown that the cancer-germline antigen NY-ESO-1 stimulates spontaneous NY-ESO-1-specific CD8(+) T cells that up-regulate PD-1 expression. We also observed that PD-1 regulates NY-ESO-1-specific CD8(+) T cell expansion upon chronic antigen stimulation. In the present study, we show that a fraction of PD-1(+) NY-ESO-1-specific CD8(+) T cells in patients with advanced melanoma up-regulates Tim-3 expression and that Tim-3(+)PD-1(+) NY-ESO-1-specific CD8(+) T cells are more dysfunctional than Tim-3(-)PD-1(+) and Tim-3(-)PD-1(-) NY-ESO-1-specific CD8(+) T cells, producing less IFN-γ, TNF, and IL-2. Tim-3-Tim-3L blockade enhanced cytokine production by NY-ESO-1-specific CD8(+) T cells upon short ex vivo stimulation with cognate peptide, thus enhancing their functional capacity. In addition, Tim-3-Tim-3L blockade enhanced cytokine production and proliferation of NY-ESO-1-specific CD8(+) T cells upon prolonged antigen stimulation and acted in synergy with PD-1-PD-L1 blockade. Collectively, our findings support the use of Tim-3-Tim-3L blockade together with PD-1-PD-L1 blockade to reverse tumor-induced T cell exhaustion/dysfunction in patients with advanced melanoma.

Upregulation of Tim-3 and PD-1 expression is associated with tumor antigen-specific CD8+ T cell dysfunction in melanoma patients

The paradoxical coexistence of spontaneous tumor antigen–specific immune responses with progressive disease in cancer patients furthers the need to dissect the molecular pathways involved in tumor-induced T cell dysfunction. In patients with advanced melanoma, we have previously shown that the cancer-germline antigen NY-ESO-1 stimulates spontaneous NY-ESO-1–specific CD8⁺ T cells that up-regulate PD-1 expression. We also observed that PD-1 regulates NY-ESO-1–specific CD8⁺ T cell expansion upon chronic antigen stimulation. In the present study, we show that a fraction of PD-1⁺ NY-ESO-1–specific CD8⁺ T cells in patients with advanced melanoma up-regulates Tim-3 expression and that Tim-3⁺PD-1⁺ NY-ESO-1–specific CD8⁺ T cells are more dysfunctional than Tim-3⁻PD-1⁺ and Tim-3⁻PD-1⁻ NY-ESO-1–specific CD8⁺ T cells, producing less IFN-γ, TNF, and IL-2. Tim-3–Tim-3L blockade enhanced cytokine production by NY-ESO-1–specific CD8⁺ T cells upon short ex vivo stimulation with cognate peptide, thus enhancing their functional capacity. In addition, Tim-3–Tim-3L blockade enhanced cytokine production and proliferation of NY-ESO-1–specific CD8⁺ T cells upon prolonged antigen stimulation and acted in synergy with PD-1–PD-L1 blockade. Collectively, our findings support the use of Tim-3–Tim-3L blockade together with PD-1–PD-L1 blockade to reverse tumor-induced T cell exhaustion/dysfunction in patients with advanced melanoma.