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Viral infections are controlled, and very often cleared, by activated T lymphocytes. The inducible co-stimulator (ICOS) mediates its functions by binding to its ligand ICOSL, enhancing T-cell activation and optimal germinal center (GC) formation. Here, we show that ICOSL is heavily downmodulated during infection of antigen-presenting cells by different herpesviruses. We found that, in murine cytomegalovirus (MCMV), the immunoevasin m138/fcr-1 physically interacts with ICOSL, impeding its maturation and promoting its lysosomal degradation. This viral protein counteracts T-cell responses, in an ICOS-dependent manner, and limits virus control during the acute MCMV infection. Additionally, we report that blockade of ICOSL in MCMV-infected mice critically regulates the production of MCMV-specific antibodies due to a reduction of T follicular helper and GC B cells. Altogether, these findings reveal a novel mechanism evolved by MCMV to counteract adaptive immune surveillance, and demonstrates a role of the ICOS:ICOSL axis in the host defense against herpesviruses.
Immunotherapy checkpoint inhibitors, such as antibodies targeting PD-1 and CTLA-4, have demonstrated the potential of harnessing the immune system to treat cancer. However, despite encouraging results particularly with respect to survival, only a minority of patients benefit from these therapies. In clinical studies aimed at understanding changes in the immune system following immunotherapy treatment, ICOS (Inducible T cell CO-Stimulator) was shown to be significantly up-regulated on CD4+ T cells and this was associated with clinical activity, indicating that ICOS stimulatory activity may be beneficial in the treatment of solid tumors. In this report, we describe the generation of specific, species cross-reactive, agonist antibodies to ICOS, including the humanized clinical candidate, JTX-2011 (vopratelimab). Preclinical studies suggest that the ICOS stimulating antibodies require Fc receptor cross-linking for optimal agonistic activity. Notably, the ICOS antibodies do not exhibit superagonist properties but rather require T cell receptor (TCR)-mediated upregulation of ICOS for agonist activity. Treatment with the ICOS antibodies results in robust anti-tumor benefit and long-term protection in preclinical syngeneic mouse tumor models. Additional benefit is observed when the ICOS antibodies are administered in combination with anti-PD-1 and anti-CTLA-4 therapies. Based on the preclinical data, JTX-2011 is currently being developed in the clinical setting for the treatment of solid tumors.
Angioimmunoblastic T cell lymphoma (AITL) is an aggressive tumor derived from malignant transformation of T follicular helper (Tfh) cells. AITL is characterized by loss-of-function mutations in Ten-Eleven Translocation 2 (TET2) epigenetic tumor suppressor and a highly recurrent mutation (p.Gly17Val) in the RHOA small GTPase. Yet, the specific role of RHOA G17V in AITL remains unknown. Expression of Rhoa G17V in CD4+ T cells induces Tfh cell specification; increased proliferation associated with inducible co-stimulator (ICOS) upregulation and increased phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase signaling. Moreover, RHOA G17V expression together with Tet2 loss resulted in development of AITL in mice. Importantly, Tet2-/-RHOA G17V tumor proliferation in vivo can be inhibited by ICOS/PI3K-specific blockade, supporting a driving role for ICOS signaling in Tfh cell transformation.
The co-stimulators ICOS (inducible T cell co-stimulator) and CD28 are both important for T follicular helper (TFH) cells, yet their individual contributions are unclear. Here, we show that each molecule plays an exclusive role at different stages of TFH cell development. While CD28 regulated early expression of the master transcription factor Bcl-6, ICOS co-stimulation was essential to maintain the phenotype by regulating the novel TFH transcription factor Klf2 via Foxo1. Klf2 directly binds to Cxcr5, Ccr7, Psgl-1, and S1pr1, and low levels of Klf2 were essential to maintain this typical TFH homing receptor pattern. Blocking ICOS resulted in relocation of fully developed TFH cells back to the T cell zone and reversion of their phenotype to non-TFH effector cells, which ultimately resulted in breakdown of the germinal center response. Our study describes for the first time the exclusive role of ICOS and its downstream signaling in the maintenance of TFH cells by controlling their anatomical localization in the B cell follicle.
The T cell expression of various co-signalling receptors from the CD28 immunoglobulin superfamily (Inducible T cell co-stimulator (ICOS), Programmed cell death 1(PD-1), cytotoxic T lymphocyte associated protein 4 (CTLA-4), B and T lymphocyte attenuator (BTLA) or from the tumour necrosis factor receptor superfamily (glucocorticoid-induced TNFR family related (GITR), 4-1BB, and CD27), is essential for T cell responses regulation. Other receptors (such as T cell immunoglobulin and mucin domain-containing protein 3, T cell immunoglobulin and T cell immunoglobulin and ITIM domain (TIGIT), and lymphocyte activation gene 3) are also involved in this regulation. Disturbance of the balance between activating and inhibitory signals can induce autoimmunity. We have developed an in vitro assay to simultaneously assess the function of naive CD4+ effector T cells (TEFFs), dendritic cells (DCs) and regulatory T cells (TREGs) and the expression of co-signalling receptors. By running the assay on cells from healthy adult, we investigated the regulation of activated T cell proliferation and phenotypes. We observed that TEFFs activated by DCs mainly expressed BTLA, ICOS and PD-1, whereas activated TREGs mainly expressed TIGIT, ICOS, and CD27. Strikingly, we observed that programmed death-ligand 1 (PD-L1) was significantly expressed on both activated TEFFs and TREGs. Moreover, high PD-L1 expression on activated TEFFs was correlated with a higher index of proliferation. Lastly, and in parallel to the TREG-mediated suppression of TEFF proliferation, we observed the specific modulation of the surface expression of PD-L1 (but not other markers) on activated TEFFs. Our results suggest that the regulation of T cell proliferation is correlated with the specific expression of PD-L1 on activated TEFFs.
The role of B cells in the development of CD4+ regulatory T cells has been emphasized recently. Our previous studies have demonstrated that the antigen-presenting splenic B cells converted naïve CD4+CD25- T cells into CD4+CD25+Foxp3- T cells without additional cytokines or chemicals with regulatory activity and that referred to as Treg-of-B cells. The present study further showed that Treg-of-B cells increased the IL-10-producing population, and the expression of c-Maf, inducible T-cell co-stimulator (ICOS) as well as cytotoxic T-lymphocyte-associated protein 4 (CTLA4) after repeated stimulation of B cells in a cell-cell contact-dependent manner. Long-term cultured Treg-of-B cells exerted IL-10 and CTLA4-mediated antigen-specific suppressive activity; moreover, the single antigen-specific Treg-of-B cells inhibited in a non-antigen-specific fashion. In conclusion, these results suggest that repeated stimulation of B cells induced IL-10-producing CD4+Foxp3- regulatory T cells in a contact-dependent manner and these Treg-of-B cells possess IL-10 and CTLA4-dependent suppressive function.
Exploring the regulation of co-inhibitory (PD-1, PD-L1, CTLA-4) and co-stimulatory (CD28) genes by chemotherapeutic drugs is important for combined immune checkpoint blockade (ICB) therapy. ICB interferes with T-cell receptor and major histocompatibility complex (MHC) signaling by antibody drugs directed against the co-inhibitors. Here, we analyzed urothelial (T24) cell line with respect to cytokine signaling by interferon γ (IFNG) and the leukemia lymphocyte (Jurkat) cell line with respect to T-cell activation as mimicked by phorbolester and calcium ionophore (pma/iono). Alongside, we considered possible intervention with the chemotherapeutics gemcitabine, cisplatin and vinflunine. Noteworthy, cisplatin significantly induced PD-L1-mRNA in naïve and IFNG treated cells whereas gemcitabine and vinflunine had no effect on PD-L1-mRNA. At the protein level, PD-L1 showed typical induction in IFNG treated cells. In Jurkat cells, cisplatin significantly induced PD-1-mRNA and PD-L1-mRNA. Pma/iono administration did not alter PD-1-mRNA and PD-L1-mRNA but significantly increased CTLA-4-mRNA and CD28-mRNA levels where vinflunine suppressed the CD28-mRNA induction. In sum, we demonstrated that certain cytostatic drugs being relevant for the therapy of urothelial cancer, affect co-inhibitory and co-stimulatory modulators of immune signaling with potential impact for perspective combined ICB therapy of patients. MHC-TCR signaling between antigen presenting cells and T-lymphocytes with co-stimulator (blue) and co-inhibitors (red) and interacting proteins (blank). Co-inhibitory connections are shown by lines and co-stimulatory connections by dotted lines. The inducible or suppressive actions of the drugs (underlined) on the respective targets are indicated.
Cancer immunotherapy is a powerful tool for inducing antigen-specific antitumor cytotoxic T lymphocytes (CTLs). Next-generation strategies may include vaccination against overexpressed oncogenic tumor-self antigens. Previously, we reported vaccination against the oncogenic tumor-self antigen D52 (D52) was effective in preventing tumor growth. We recently reported that D52-vaccinated IL-10-deficient mice generated a significant memory response against tumor recurrence compared to wild-type mice and that vaccine-induced CD8+ IL-10+ T cells may possess regulatory function. Herein, we extended these studies by testing the hypothesis that D52-vaccine-elicited CD8+ IL-10+ T cells represent a distinct T cell population with a regulatory phenotype. C57Black/6J mice deficient in IL-10 or IFN-γ were vaccinated with the murine orthologue of D52; vaccination of wild-type (wt) mice served as a control for comparison. T cells were isolated from all three groups of vaccinated mice, and RNA was extracted from purified CD8+ T cells for deep sequencing and expression analysis. Chemokine receptor 8 (CCR8) and inducible co-stimulator (ICOS) were overexpressed in CD8+ T cells that produced IL-10 but not IFN-γ. These surface markers are associated with IL-10 producing CD4+ T regulatory cells thus supporting the possibility that CD8+ IL-10+ T cells elicited by D52 vaccination represent a unique regulatory T cell subset. The current phenotypic analyses of D52 vaccine elicited CD8+ T cells strengthen our premise that CD8+ IL-10+ T cells elicited by D52 tumor-self protein vaccination likely contribute to the suppression of memory CTL responses and inhibition of durable tumor immunity.
Immune checkpoint blockade endows patients with unparalleled success in conquering cancer. Unfortunately, inter‑individual heterogeneity causes failure in controlling tumors in many patients. Emerging mass cytometry technology is capable of revealing a multiscale onco‑immune landscape that improves the efficacy of cancer immunotherapy. We introduced mass cytometry to determine the personalized immune checkpoint status in bone marrow and peripheral blood samples from 3 patients with multiple myeloma, amyloid light‑chain amyloidosis, and solitary bone plasmacytoma and 1 non‑hematologic malignancy patient. The expression of 18 immune regulatory receptors and ligands on 17 defined cell populations was simultaneously examined. By single‑cell analyses, we identified the T cell clusters that serve as immunosuppressive signal source and revealed integrated immune checkpoint axes of individuals, thereby providing multiple potential immunotherapeutic targets, including programmed cell death protein 1 (PD‑1), inducible co‑stimulator (ICOS), and cluster of differentiation 28 (CD28), for each patient. Distinguishing the cell populations that function as providers and receivers of the immune checkpoint signals demonstrated a distinct cross‑interaction network of immunomodulatory signals in individuals. These in‑depth personalized data demonstrate mass cytometry as a powerful innovation to discover the systematical immune status in the primary and peripheral tumor microenvironment.
The dramatic clinical benefit of immune checkpoint blockade for a fraction of cancer patients suggests the potential for further clinical benefit in a broader cancer patient population by combining immune checkpoint inhibitors with active immunotherapies. The anti-tumor efficacy of MVA-BN-HER2 poxvirus-based active immunotherapy alone or in combination with CTLA-4 checkpoint blockade was investigated in a therapeutic CT26-HER-2 lung metastasis mouse model. MVA-BN-HER2 immunotherapy significantly improved the median overall survival compared to untreated controls or CTLA-4 blockade alone (p < 0.001). Robust synergistic efficacy was achieved with the combination therapy (p < 0.01). Improved survival following MVA-BN-HER2 administration was accompanied by increased tumor infiltration by HER-2-specific cytotoxic T lymphocytes (CTL). These tumor-specific CTL had characteristics similar to antiviral CTL, including strong expression of activation markers and co-expression of IFNγ and TNFα. Combination with CTLA-4 blockade significantly increased the magnitude of HER-2-specific T cell responses, with a higher proportion co-expressing TNFα and/or IL-2 with IFNγ. Furthermore, in mice treated with MVA-BN-HER2 (alone or in combination with CTLA-4 blockade), the inducible T cell co-stimulator (ICOS) protein was expressed predominantly on CD4 and CD8 effector T cells but not on regulatory T cells (T(reg)). In contrast, mice left untreated or treated solely with CTLA-4 blockade harbored elevated ICOS(+) Treg, a phenotype associated with highly suppressive activity. In conclusion, poxvirus-based active immunotherapy induced robust tumor infiltration by highly efficient effector T cells. Combination with CTLA-4 immune checkpoint blockade amplified this response resulting in synergistically improved efficacy. These hypothesis-generating data may help elucidate evidence of enhanced clinical benefit from combining CTLA-4 blockade with poxvirus-based active immunotherapy.
T follicular helper (Tfh) cells are a subset of T cells carrying the CD4 antigen; they are important in supporting plasma cell and germinal centre responses. The initial induction of Tfh cell properties occurs within the first few days after activation by antigen recognition on dendritic cells, although how dendritic cells promote this cell-fate decision is not fully understood. Moreover, although Tfh cells are uniquely defined by expression of the follicle-homing receptor CXCR5 (refs 1, 2), the guidance receptor promoting the earlier localization of activated T cells at the interface of the B-cell follicle and T zone has been unclear. Here we show that the G-protein-coupled receptor EBI2 (GPR183) and its ligand 7α,25-dihydroxycholesterol mediate positioning of activated CD4 T cells at the interface of the follicle and T zone. In this location they interact with activated dendritic cells and are exposed to Tfh-cell-promoting inducible co-stimulator (ICOS) ligand. Interleukin-2 (IL-2) is a cytokine that has multiple influences on T-cell fate, including negative regulation of Tfh cell differentiation. We demonstrate that activated dendritic cells in the outer T zone further augment Tfh cell differentiation by producing membrane and soluble forms of CD25, the IL-2 receptor α-chain, and quenching T-cell-derived IL-2. Mice lacking EBI2 in T cells or CD25 in dendritic cells have reduced Tfh cells and mount defective T-cell-dependent plasma cell and germinal centre responses. These findings demonstrate that distinct niches within the lymphoid organ T zone support distinct cell fate decisions, and they establish a function for dendritic-cell-derived CD25 in controlling IL-2 availability and T-cell differentiation.
With the increasing oncological potential of immunotherapy, several immune checkpoint modulators are being investigated. The value of immune markers, including programmed cell death ligand-1, programmed cell death-1 (PD-1), inducible co-stimulator (ICOS), lymphocyte activation gene-3, T-cell immunoglobulin, and mucin-dominant containing-3 (TIM-3), is not well known. Using tissue microarrays of 396 patients who underwent surgery for oesophageal squamous cell carcinoma (ESCC), infiltrated T-cell subsets (CD3, CD8, and Foxp3) and checkpoint protein expression were scored. With a median follow-up of 24.8 months, CD3+ TIL subsets (50.0%) had longer median recurrence-free survival (RFS, 55.0 vs 21.4 months) and overall survival (OS, 77.7 vs 35.8 months). Patients with high ICOS expression (46.5%) had longer median RFS (53.9 vs 25.3 months) and OS (88.8 vs 36.9 months). For PD-1, RFS (hazard ratio [HR] 0.67) and OS (HR 0.66) were significantly longer in the high-expression group (45.2%). In the multivariate analysis, high TIM-3 expression (50.8%) had a significant relationship with shorter RFS (HR = 1.52) and OS (HR = 1.60). High CD3+ TIL and T-cell ICOS expression were associated with favourable prognosis, whereas high TIM-3 expression suggested a poor prognosis. Our findings may confer new insights to improve ESCC outcomes beyond the application of PD-1 blockade.
Dysregulation of T cells mediated immune responses is a hallmark in the development of systemic lupus erythematosus (SLE). Recent genome wide association study (GWAS) revealed the genetic contribution of variants located in the cytotoxic T lymphocyte-associated protein-4 (CTLA4)-inducible T cell co-stimulator (ICOS) intergenic region to SLE susceptibility. Our aim is to find a functional variant in this region.
Inducible T cell co-stimulator (ICOS) deficiency has been categorized as a combined immunodeficiency often complicated by enteropathies, autoimmunity, lymphoproliferation, and malignancy. We report seven new patients and four novel ICOS mutations resulting in a common variable immunodeficiency (CVID)-like phenotype and show that dysregulated IL-12 release, reduced cytotoxic T lymphocyte-associated protein 4 (CTLA4) expression, and skewing towards a Th1-dominant phenotype are all associated with inflammatory complications in this condition.
The ICOS (Inducible T cell Co-Stimulator)/B7RP-1 (B7-related protein 1) interaction is critical for the proper activation of a T lymphocyte. In this manuscript we describe a systematic in vivo approach to determine the level of blockade required to impair the generation of a T cell-dependent antibody response. We have developed an overall strategy for correlating drug exposure, target saturation, and efficacy in a biological response that can be generalized for most protein therapeutics. Using this strategy, we determined that low levels of B7RP-1 blockade are still sufficient to inhibit the immune response. These data suggest that contact between the T cell and the antigen-presenting cell during antigen presentation is much more sensitive to inhibition than previously believed and that ICOS/B7RP-1 blockade may be efficacious in the treatment of autoimmune diseases.
The present study aimed to explore latent markers for identifying primary Sjogren's syndrome (pSS), as well as their expression and molecular mechanism. Hub inducible T cell co‑stimulator genes were retrieved from the Gene Expression Omnibus. A total of 95 patients with pSS and 68 healthy individuals from Affiliated Hospital of Nantong University (Nantong, China) were included in the study. The expression of inducible T cell co‑stimulator (ICOS) in whole blood and saliva was evaluated using ELISA. Western blotting was performed to investigate aquaporin 5 (AQP5) protein expression, as well as the inflammatory effects of ICOS in patients with pSS compared with healthy individuals. Differentially expressed mRNAs were analyzed in whole blood (GSE84844) and salivary gland (GSE40611) of patients with pSS. In total, 15 hub genes were identified, among which ICOS was indicated to serve a role in the most pivotal immunity pathways. pSS was markedly associated with inflammatory pathways. Results from the present study found that ICOS was upregulated in the salivary gland, whole blood and saliva of patients with pSS. Salivary weight was negatively correlated with the levels of ICOS in the saliva of patients with pSS. The expression of AQP5 was markedly lower in patients with pSS. The expression of AQP5 was negatively associated with ICOS. Compared with that of healthy individuals, the expression of ICOS and inflammatory factors was higher and the expression of AQP5 was lower in pSS patients as assessed by western blotting. These data demonstrated that ICOS may affect AQP5 expression by promoting inflammation in the salivary glands of patients with pSS.
The substitution of one amino acid in the Roquin protein by the sanroque mutation induces a dramatic autoimmune syndrome in mice. This is believed to occur through ectopic expression of inducible T cell co-stimulator (ICOS) and unrestrained differentiation of follicular T helper cells, which induce spontaneous germinal center reactions to self-antigens. In this study, we demonstrate that tissue-specific ablation of Roquin in T or B cells, in the entire hematopoietic system, or in epithelial cells of transplanted thymi did not cause autoimmunity. Loss of Roquin induced elevated expression of ICOS through T cell-intrinsic and -extrinsic mechanisms, which itself was not sufficient to break self-tolerance. Instead, ablation of Roquin in the hematopoietic system caused defined changes in immune homeostasis, including the expansion of macrophages, eosinophils, and T cell subsets, most dramatically CD8 effector-like T cells, through cell-autonomous and nonautonomous mechanisms. Germline Roquin deficiency led to perinatal lethality, which was partially rescued on the genetic background of an outbred strain. However, not even complete absence of Roquin resulted in overt self-reactivity, suggesting that the sanroque mutation induces autoimmunity through an as yet unknown mechanism.
Pancreatic ductal adenocarcinoma (PDA) is characterized by immune tolerance and immunotherapeutic resistance. We discovered upregulation of receptor-interacting serine/threonine protein kinase 1 (RIP1) in tumor-associated macrophages (TAMs) in PDA. To study its role in oncogenic progression, we developed a selective small-molecule RIP1 inhibitor with high in vivo exposure. Targeting RIP1 reprogrammed TAMs toward an MHCIIhiTNFα+IFNγ+ immunogenic phenotype in a STAT1-dependent manner. RIP1 inhibition in TAMs resulted in cytotoxic T cell activation and T helper cell differentiation toward a mixed Th1/Th17 phenotype, leading to tumor immunity in mice and in organotypic models of human PDA. Targeting RIP1 synergized with PD1-and inducible co-stimulator-based immunotherapies. Tumor-promoting effects of RIP1 were independent of its co-association with RIP3. Collectively, our work describes RIP1 as a checkpoint kinase governing tumor immunity.
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