Correlation between Tregs and ICOS-induced M2 macrophages polarization in colorectal cancer progression.

Objective: To explore the mechanism by which Tregs promote the progression of colorectal cancer by inducing tumor-associated macrophages to polarize into M2 type via ICOS. Methods: Postoperative pathological tissues and clinical pathological data of 268 colorectal cancer patients who underwent initial surgery were collected. Immunohistochemistry (IHC) was used to detect the expression levels of ICOS, CD163 (a marker for M2 macrophages), and Foxp3 (a marker for Tregs) in cancerous, adjacent non-tumorous, and normal tissues. The relationship of ICOS, M2 macrophages, and Tregs in CRC with clinical pathological characteristics and pre-surgical tumor markers (such as CEA and CA199) was explored. Results: The expression levels of M2 macrophages and Tregs increased with tumor progression, while ICOS expression showed a decreasing trend. Compared to adjacent and normal tissues, the expression levels of ICOS, M2 macrophages, and Tregs were higher in CRC tissues. The expression levels of M2 macrophages and Tregs were significantly positively correlated with tumor markers, while ICOS expression was significantly negatively correlated. Conclusion: Tumor-associated m2 macrophages induced by Tregs and ICOS participate in the dynamic balance of the colorectal cancer tumor microenvironment, and their interaction affects colorectal carcinogenesis and progression. High levels of ICOS are associated with better long-term survival rates.

The impact of ICOSL/ICOS pathway-regulated long non-coding RNAs on liver fibrosis in mice infected with Schistosoma japonicum.

BACKGROUND: The primary pathogenic mechanism of schistosomiasis-associated liver fibrosis involves the deposition of schistosome eggs, leading to the formation of liver egg granulomas and subsequent liver fibrosis. Hepatic stellate cells are abnormally activated, resulting in excessive collagen deposition and fibrosis development. While specific long non-coding RNAs (lncRNAs) have been associated with fibrotic processes, their roles in schistosomiasis-associated liver fibrosis remain unclear. METHODS: Our previous research indicated that downregulating the ICOSL/ICOS could partially alleviate liver fibrosis. In this study, we established a schistosomiasis infection model in C57BL/6 and ICOSL knockout (KO) mice, and the liver pathology changes were observed at various weeks postinfection (wpi) using hematoxylin and eosin and Masson's trichrome staining. Within the first 4 wpi, no significant liver abnormalities were observed. However, mice exhibited evident egg granulomas and fibrosis in their livers at 7 wpi. Notably, ICOSL-KO mice had significantly smaller pathological variations compared with simultaneously infected C57BL/6 mice. To investigate the impact of lncRNAs on schistosomiasis-associated liver fibrosis, quantitative real-time polymerase chain reaction (RT-qPCR) was used to monitor the dynamic changes of lncRNAs in hepatic stellate cells of infected mice. RESULTS: The results demonstrated that lncRNA-H19, -MALAT1, -PVT1, -P21 and -GAS5 all participated in liver fibrosis formation after schistosome infection. In addition, ICOSL-KO mice exhibited significantly inhibited expression of lncRNA-H19, -MALAT1 and -PVT1 after 7 wpi. In contrast, they showed enhanced expression of lncRNA-P21 and -GAS5 compared with C57BL/6 mice, influencing liver fibrosis development. Furthermore, small interfering RNA transfection (siRNA) in JS-1 cells in vitro confirmed that lncRNA-H19, -MALAT1, and -PVT1 promoted liver fibrosis, whereas lncRNA-P21 and -GAS5 had the opposite effect on key fibrotic molecules, including α- smooth muscle actin and collagen I expression. CONCLUSIONS: This study uncovers that ICOSL/ICOS may play a role in activating hepatic stellate cells and promoting liver fibrosis in mice infected with Schistosoma japonicum by dynamically regulating the expression of specific lncRNAs. These findings offer potential therapeutic targets for schistosomiasis-associated liver fibrosis.

ScRNA-Seq Analyses Define the Role of GATA3 in iNKT Cell Effector Lineage Differentiation.

While the transcription factor GATA-3 is well-established for its crucial role in T cell development, its specific influence on invariant natural killer T (iNKT) cells remains relatively unexplored. Using flow cytometry and single-cell transcriptomic analysis, we demonstrated that GATA-3 deficiency in mice leads to the absence of iNKT2 and iNKT17 cell subsets, as well as an altered distribution of iNKT1 cells. Thymic iNKT cells lacking GATA-3 exhibited diminished expression of PLZF and T-bet, key transcription factors involved in iNKT cell differentiation, and reduced production of Th2, Th17, and cytotoxic effector molecules. Single-cell transcriptomics revealed a comprehensive absence of iNKT17 cells, a substantial reduction in iNKT2 cells, and an increase in iNKT1 cells in GATA-3-deficient thymi. Differential expression analysis highlighted the regulatory role of GATA-3 in T cell activation signaling and altered expression of genes critical for iNKT cell differentiation, such as Icos, Cd127, Eomes, and Zbtb16. Notably, restoration of Icos, but not Cd127, expression could rescue iNKT cell development in GATA-3-deficient mice. In conclusion, our study demonstrates the pivotal role of GATA-3 in orchestrating iNKT cell effector lineage differentiation through the regulation of T cell activation pathways and Icos expression, providing insights into the molecular mechanisms governing iNKT cell development and function.

Interruption of the intratumor CD8+ T cell:Treg crosstalk improves the efficacy of PD-1 immunotherapy.

PD-1 blockade unleashes potent antitumor activity in CD8+ T cells but can also promote immunosuppressive T regulatory (Treg) cells, which may worsen the response to immunotherapy. Tumor-Treg inhibition is a promising strategy to improve the efficacy of checkpoint blockade immunotherapy; however, our understanding of the mechanisms supporting tumor-Tregs during PD-1 immunotherapy is incomplete. Here, we show that PD-1 blockade increases tumor-Tregs in mouse models of melanoma and metastatic melanoma patients. Mechanistically, Treg accumulation is not caused by Treg-intrinsic inhibition of PD-1 signaling but depends on an indirect effect of activated CD8+ T cells. CD8+ T cells produce IL-2 and colocalize with Tregs in mouse and human melanomas. IL-2 upregulates the anti-apoptotic protein ICOS on tumor-Tregs, promoting their accumulation. Inhibition of ICOS signaling before PD-1 immunotherapy improves control over immunogenic melanoma. Thus, interrupting the intratumor CD8+ T cell:Treg crosstalk represents a strategy to enhance the therapeutic efficacy of PD-1 immunotherapy.

Investigation of activation-induced markers (AIM) in porcine T cells by flow cytometry.

Activation-induced markers (AIMs) are frequently analyzed to identify re-activated human memory T cells. However, in pigs the analysis of AIMs is still not very common. Based on available antibodies, we designed a multi-color flow cytometry panel comprising pig-specific or cross-reactive antibodies against CD25, CD69, CD40L (CD154), and ICOS (CD278) combined with lineage/surface markers against CD3, CD4, and CD8α. In addition, we included an antibody against tumor necrosis factor alpha (TNF-α), to study the correlation of AIM expression with the production of this abundant T cell cytokine. The panel was tested on peripheral blood mononuclear cells (PBMCs) stimulated with phorbol 12-myristate 13-acetate (PMA)/ionomycin, Staphylococcus enterotoxin B (SEB) or PBMCs from African swine fever virus (ASFV) convalescent pigs, restimulated with homologous virus. PMA/ionomycin resulted in a massive increase of CD25/CD69 co-expressing T cells of which only a subset produced TNF-α, whereas CD40L expression was largely associated with TNF-α production. SEB stimulation triggered substantially less AIM expression than PMA/ionomycin but also here CD25/CD69 expressing T cells were identified which did not produce TNF-α. In addition, CD40L-single positive and CD25+CD69+CD40L+TNF-α- T cells were identified. In ASFV restimulated T cells TNF-α production was associated with a substantial proportion of AIM expressing T cells but also here ASFV-reactive CD25+CD69+TNF-α- T cells were identified. Within CD8α+ CD4 T cells, several CD25/CD40L/CD69/ICOS defined phenotypes expanded significantly after ASFV restimulation. Hence, the combination of AIMs tested will allow the identification of primed T cells beyond the commonly used cytokine panels, improving capabilities to identify the full breadth of antigen-specific T cells in pigs.

Prognostic and therapeutic potential of imbalance between PD-1+CD8 and ICOS+Treg cells in advanced HBV-HCC.

Over 50% of patients with hepatitis B virus-associated hepatocellular carcinoma (HBV-HCC) are diagnosed at an advanced stage, which is characterized by immune imbalance between CD8+ T cells and regulatory T (Treg) cells that accelerates disease progression. However, there is no imbalance indicator to predict clinical outcomes. Here, we show that the proportion of CD8+ T cells decreases and Treg cells increases in advanced HBV-HCC patients. During this stage, CD8+ T cells and Treg cells expressed the coinhibitory molecule PD-1 and the costimulatory molecule ICOS, respectively. Additionally, the ratio between PD-1+CD8 and ICOS+Tregs showed significant changes. Patients were further divided into high- and low-ratio groups: PD-1+CD8 and ICOS+Tregs high- (PD-1/ICOShi) and low-ratio (PD-1/ICOSlo) groups according to ratio median. Compared with PD-1/ICOSlo patients, the PD-1/ICOShi group had better clinical prognosis and weaker CD8+ T cells exhaustion, and the T cell-killing and proliferation functions were more conservative. Surprisingly, the small sample analysis found that PD-1/ICOShi patients exhibited a higher proportion of tissue-resident memory T (TRM) cells and had more stable killing capacity and lower apoptosis capacity than PD-1/ICOSlo advanced HBV-HCC patients treated with immune checkpoint inhibitors (ICIs). In conclusion, the ratio between PD-1+CD8 and ICOS+Tregs was associated with extreme immune imbalance and poor prognosis in advanced HBV-HCC. These findings provide significant clinical implications for the prognosis of advanced HBV-HCC and may serve as a theoretical basis for identifying new targets in immunotherapy.

Joint effects of CD8A and ICOS in Long QT Syndrome (LQTS) and Beckwith-Wiedemann Syndrome (BWS).

BACKGROUND: Long QT Syndrome (LQTS) and Beckwith-Wiedemann Syndrome (BWS) are complex disorders with unclear origins, underscoring the need for in-depth molecular investigations into their mechanisms. The main aim of this study is to identify the shared key genes between LQTS and BWS, shedding light on potential common molecular pathways underlying these syndromes. METHODS: The LQTS and BWS datasets are available for download from the GEO database. Differential expression genes (DEGs) were identified. Weighted gene co-expression network analysis (WGCNA) was used to detect significant modules and central genes. Gene enrichment analysis was performed. CIBERSORT was used for immune cell infiltration analysis. The predictive protein interaction (PPI) network of core genes was constructed using STRING, and miRNAs regulating central genes were screened using TargetScan. RESULTS: Five hundred DEGs associated with Long QT Syndrome and Beckwith-Wiedemann Syndrome were identified. GSEA analysis revealed enrichment in pathways such as T cell receptor signaling, MAPK signaling, and adrenergic signaling in cardiac myocytes. Immune cell infiltration indicated higher levels of memory B cells and naive CD4 T cells. Four core genes (CD8A, ICOS, CTLA4, LCK) were identified, with CD8A and ICOS showing low expression in the syndromes and high expression in normal samples, suggesting potential inverse regulatory roles. CONCLUSION: The expression of CD8A and ICOS is low in long QT syndrome and Beckwith-Wiedemann syndrome, indicating their potential as key genes in the pathogenesis of these syndromes. The identification of shared key genes between LQTS and BWS provides insights into common molecular mechanisms underlying these disorders, potentially facilitating the development of targeted therapeutic strategies.

Deficiency of CBL and CBLB ubiquitin ligases leads to hyper T follicular helper cell responses and lupus by reducing BCL6 degradation.

Recent evidence reveals hyper T follicular helper (Tfh) cell responses in systemic lupus erythematosus (SLE); however, molecular mechanisms responsible for hyper Tfh cell responses and whether they cause SLE are unclear. We found that SLE patients downregulated both ubiquitin ligases, casitas B-lineage lymphoma (CBL) and CBLB (CBLs), in CD4+ T cells. T cell-specific CBLs-deficient mice developed hyper Tfh cell responses and SLE, whereas blockade of Tfh cell development in the mutant mice was sufficient to prevent SLE. ICOS was upregulated in SLE Tfh cells, whose signaling increased BCL6 by attenuating BCL6 degradation via chaperone-mediated autophagy (CMA). Conversely, CBLs restrained BCL6 expression by ubiquitinating ICOS. Blockade of BCL6 degradation was sufficient to enhance Tfh cell responses. Thus, the compromised expression of CBLs is a prevalent risk trait shared by SLE patients and causative to hyper Tfh cell responses and SLE. The ICOS-CBLs axis may be a target to treat SLE.

ICOS agonist vopratelimab modulates follicular helper T cells and improves B cell function in common variable immunodeficiency.

Common variable immunodeficiency (CVID) is an immune defect characterized by hypogammaglobulinemia and impaired development of B cells into plasma cells. As follicular helper T cells (TFH) play a central role in humoral immunity, we examined TFH cells in CVID, and investigated whether an inducible T cell co-stimulator (ICOS) agonist, vopratelimab, could modulate TFH, B cell interactions and enhance immunoglobulin production. CVID subjects had decreased TFH17 and increased TFH1 subsets; this was associated with increased transitional B cells and decreased IgG+ B and IgD-IgM-CD27+ memory B cells. ICOS expression on CVID CD4+ T cells was also decreased. However, ICOS activation of CD4+ T cells by vopratelimab significantly increased total CVID TFH, TFH2, cell numbers, as well as IL-4, IL-10 and IL-21 secretion in vitro. Vopratelimab treatment also increased plasma cells, IgG+ B cells, reduced naïve & transitional B cells and significantly increased IgG1 secretion by CVID B cells. Interestingly, vopratelimab treatment also restored IgA secretion in PBMCs from several CVID patients who had a complete lack of endogenous serum IgA. Our data demonstrate the potential of TFH modulation in restoring TFH and enhancing B cell maturation in CVID. The effects of an ICOS agonist in antibody defects warrants further investigation. This biologic may also be of therapeutic interest in other clinical settings of antibody deficiency.

The Expression and Prognostic Significance of ICOS in NSCLC Integrated Pan-Cancer and Multi-Omics Analyses.

Background: Inducible co-stimulator (ICOS) shows great potential in the regulation of innate and adaptive immunity. However, previous studies of ICOS have often been limited to one or two levels. Methods: Using the data from the online database, the immunohistochemistry, and enzyme-linked immunosorbent assays, we investigated the role of ICOS / PD-L1 on patients with NSCLC at the mRNA, protein, and serum levels. Results: Our data revealed that unlike most solid tumors, the mRNA expression of ICOS was down-regulated in NSCLC. In addition, our data also showed that mRNA expression levels in ICOS are negatively associated with poor clinicopathologic grading but positively associated with better prognostic outcomes and higher Tregs infiltration level. Immunohistochemistry showed that ICOS correlated negatively with the T stage; while PD-L1 levels correlated positively with the N stage and FOXP3 levels. Serological biomarker analysis showed that patients with NSCLC had lower sICOS levels, which increased significantly post-surgery, and combined sICOS and sPD-L1 diagnosis improved efficacy and accuracy of disease diagnosis. Conclusion: Our findings support that ICOS suggests lower pathological staging and better prognosis. ICOS is a potential diagnostic and prognostic biomarker for NSCLC.

Sex-specific differences in ICOS+ T helper cell differentiation in systemic lupus erythematosus patients with low disease activity.

Systemic lupus erythematosus (SLE) is a sex biased chronic autoimmune disease affecting predominantly females during reproductive ages. Changes in the ratio of inducible costimulatory molecule (ICOS)+ regulatory (Treg) and non-regulatory responder (Tresp) CD4+ T cells proved to be crucial for the occurrence of high disease activity. Here, we investigated how the differentiation of ICOS+CD45RA+CD31+ recent thymic emigrant (RTE) Tresps into CD45RA-CD31- memory Tresps affects the percentages of ICOS+ Tresps within total CD4+ T cells. Three different pathways (pathway 1 via CD45RA-CD31+ memory Tresps, pathway 2 via direct proliferation and pathway 3 via resting mature naïve CD45RA+CD31- (MN) cells) were examined in healthy controls and SLE remission patients separated by sex. In female SLE remission patients, immunosuppressive therapy inhibited the ICOS+ RTE differentiation via CD45RA-CD31+ memory Tresps and direct proliferation, leaving an age-independently increased differentiation into CD45RA-CD31- memory Tresps by conversion of resting MN Tresps compared with healthy controls. Due to exhaustion of this pathway with age, no age-dependent change in the percentages of ICOS+ Tresps within total CD4+ T cells could be found. In contrast, no age-independently increased differentiation could be detected in men due to sufficient immunosuppression of all three pathways. This allowed an age-dependent differentiation of ICOS+ RTE Tresps into CD45RA-CD31- memory Tresps by conversion of resting MN Tresps, resulting in age-dependently increasing percentages of ICOS+ Tresps within total CD4+ T cells. We hypothesize that the sex-specific differential effect of immunosuppression on the differentiation of ICOS+ Tresps may explain the sex- and age-dependent occurrence of high disease activity.

Transcriptional profile and immune infiltration in colorectal cancer reveal the significance of inducible T-cell costimulator as a crucial immune checkpoint molecule.

BACKGROUND: Emergence of novel immuno-therapeutics has shown promising improvement in the clinical outcome of colorectal cancer (CRC). OBJECTIVE: To identify robust immune checkpoints based on expression and immune infiltration profiles of clinical CRC samples. METHODS: One dataset from The Cancer Genome Atlas database and two from Gene Expression Omnibus were independently employed for the analysis. Genes associated with overall survival were identified, and distribution of each immune checkpoint with respect to different clinical features was determined to explore key immune checkpoints. Multiple staining methods were used to verify the correlation between key immune checkpoint ICOS and clinical pathological features. Differentially expressed mRNA and long non-coding RNA (lncRNA) were then detected for gene set enrichment analysis and gene set variation analysis to investigate the differentially enriched biological processes between low- and high-expression groups. Significant immune-related mRNAs and lncRNA were subjected to competing endogenous RNA (ceRNA) network analysis. Correlation of inducible T-cell costimulator (ICOS) and top 10 genes in ceRNA network were further considered for validation. RESULTS: ICOS was identified from 14 immune checkpoints as the most highly correlated gene with survival and clinical features in CRC. The expression of ICOS protein in the poorly differentiated group was lower than that in the moderately differentiated group, and the expression in different pathological stages was significant. In addition, the expressions of ICOS were negatively correlated with Ki67. A conspicuous number of immune-related pathways were enriched in differentially expressed genes in the ICOS high- and low-expression groups. Integration with immune infiltration data revealed a multitude of differentially expressed immune-related genes enriched for ceRNA network. Furthermore, expression of top 10 genes investigated from ceRNA network showed high correlation with ICOS. CONCLUSION: ICOS might serve as a robust immune checkpoint for prognosis with several genes being potential targets of ICOS-directed immunotherapy in CRC.

Inducing expression of ICOS-L by oncolytic adenovirus to enhance tumor-specific bi-specific antibody efficacy.

BACKGROUND: Intratumoral injection of oncolytic viruses (OVs) shows promise in immunotherapy: ONCOS-102, a genetically engineered OV that encodes Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) demonstrated efficacy in early clinical trials, enhancing T cell infiltration in tumors. This suggests OVs may boost various forms of immunotherapy, including tumor-specific bi-specific antibodies (BsAbs). METHODS: Our study investigated in vitro, how ONCOS-204, a variant of ONCOS-virus expressing the ligand of inducible T-cell co-stimulator (ICOSL), modulates the process of T cell activation induced by a BsAb. ONCOS-102 was used for comparison. Phenotypic and functional changes induced by combination of different OVs, and BsAb in T cell subsets were assessed by flow cytometry, viability, and proliferation assays. RESULTS: Degranulation and IFNγ and TNF production of T cells, especially CD4 + T cells was the most increased upon target cell exposure to ONCOS-204. Unexpectedly, ONCOS-204 profoundly affected CD8 + T cell proliferation and function through ICOS-L/ICOS interaction. The effect solely depended on cell surface expression of ICOS-L as soluble ICOSL did not induce notable T cell activity. CONCLUSIONS: Together, our data suggests that oncolytic adenoviruses encoding ICOSL may enhance functional activity of tumor-specific BsAbs thereby opening a novel avenue for clinical development in immunotherapeutics.

Decoding autumn phenology: Unraveling the link between observation methods and detected environmental cues.

Leaf coloring and fall mark the end of the growing season (EOS), playing essential roles in nutrient cycling, resource allocation, ecological interactions, and as climate change indicators. However, understanding future changes in autumn phenology is challenging due to the multitude of likely environmental cues and substantial variations in timing caused by different derivation methods. Yet, it remains unclear whether these two factors are independent or if methodological uncertainties influence the environmental cues determined. We derived start of growing season (SOS) and EOS at a mixed beech forest in Central Germany for the period 2000-2020 based on four different derivation methods using a unique long-term data set of in-situ data, canopy imagery, eddy covariance measurements, and satellite remote sensing data and determined their influence on a predictor analysis of leaf senescence. Both SOS and EOS exhibited substantial ranges in mean onset dates (39.5 and 28.6 days, respectively) across the different methods, although inter-annual variations and advancing SOS trends were similar across methods. Depending on the data, EOS trends were advanced or delayed, but inter-annual patterns correlated well (mean r = .46). Overall, warm, dry, and less photosynthetically productive growing seasons were more likely to be associated with a delayed EOS, while colder, wetter, and more photosynthetically productive vegetation periods resulted in an earlier EOS. In addition, contrary to recent results, no clear influence of pre-solstice vegetation activity on the timing of senescence was detected. However, most notable were the large differences in sign and strength of potential drivers both in the univariate and multivariate analyses when comparing derivation methodologies. The results suggest that an ensemble analysis of all available phenological data sources and derivation methods is needed for general statements on autumn phenology and its influencing variables and correct implementation of the senescence process in ecosystem models.

The Role of the CD28 Family Receptors in T-Cell Immunomodulation.

The CD28 family receptors include the CD28, ICOS (inducible co-stimulator), CTLA-4 (cytotoxic T-lymphocyte antigen-4), PD-1 (programmed cell death protein 1), and BTLA (B- and T-lymphocyte attenuator) molecules. They characterize a group of molecules similar to immunoglobulins that control the immune response through modulating T-cell activity. Among the family members, CD28 and ICOS act as enhancers of T-cell activity, while three others-BTLA, CTLA-4, and PD-1-function as suppressors. The receptors of the CD28 family interact with the B7 family of ligands. The cooperation between these molecules is essential for controlling the course of the adaptive response, but it also significantly impacts the development of immune-related diseases. This review introduces the reader to the molecular basis of the functioning of CD28 family receptors and their impact on T-cell activity.

Pharmacological inhibition of ICOS attenuates the protective effect of exercise on cardiac fibrosis induced by isoproterenol.

AIMS: To investigate the cardioprotective mechanism of exercise or exercise combined with inducible costimulatory molecules (ICOS) monoclonal antibody (mAb) therapy against isoproterenol (ISO)-induced cardiac remodeling. MAIN METHODS: Totally 24 male C57BL/6J mice were randomly divided into four groups: the control group (normal saline treatment), ISO group (subcutaneous injection of isoproterenol, 10 mg/kg/day, once daily for 5 consecutive days), the exercise with subcutaneous ISO injection group (EPI), and the exercise with injected with ISO and ICOS mAb group (EPII). The mice in EPI and EPII group were trained on a small animal treadmill for 4 weeks (13 m/min, 0% grade, 60min/day). KEY FINDINGS: Exercise significantly attenuated CD45+, Mac-2 inflammatory cell infiltration, cardiac fibrosis and inhibited the RIPK1/RIPK3/MLKL/CaMKII and cardiomyocyte pyroptosis pathways to counter ISO-induced severe cardiac injury. The administration of the ICOS mAb may inhibit the cardioprotection of exercise against ISO-induced heart damage. Compared to those in EPI, our data showed that the increasing levels of myocardial fibrosis, the leukocyte infiltration of cardiac tissue and proteins expression of cardiac myocyte necrosis and pyroptosis signaling pathways in the EPII group. SIGNIFICANCE: Our results demonstrated that exercise decreased leukocyte infiltration in heart, inhibited the cardiomyocyte pyroptosis and necroptosis signaling pathways, and attenuated inflammatory responses to alleviate ISO-induced cardiac fibrosis. However, the antifibrotic effects of combined treatment with exercise and ICOS mAb intervention did not exhibit synergistic enhancement.

Design of cyclic peptides as novel inhibitors of ICOS/ICOSL interaction.

Compared to small molecules and antibodies, cyclic peptides exhibit unique biochemical and therapeutic attributes in the realm of pharmaceutical applications. The interaction between the inducible costimulator (ICOS) and its ligand (ICOSL) plays a key role in T-cell differentiation and activation. ICOS/ICOSL inhibition results in a reduction in the promotion of immunosuppressive regulatory T cells (Tregs) in both hematologic malignancies and solid tumors. Herein, we implement the computational cPEPmatch approach to design the first examples of cyclic peptides that inhibit ICOS/ICOSL interaction. The top cyclic peptide from our approach possessed an IC50 value of 1.87 ± 0.15 µM as an ICOS/ICOSL inhibitor and exhibited excellent in vitro pharmacokinetic properties as a drug candidate. Our work will lay the groundwork for future endeavors in cancer drug discovery, with the goal of developing cyclic peptides that target the ICOS/ICOSL interaction.

Tumor-infiltrating mast cells stimulate ICOS+ regulatory T cells through an IL-33 and IL-2 axis to promote gastric cancer progression.

INTRODUCTION: In solid tumors, regulatory T cell (Treg) and mast cell perform different roles depending on the microenvironment. Nevertheless, mast cell and Treg-mediated interactions in gastric cancer (GC) are unclear, as are their regulation, function, and clinical significance. OBJECTIVE: The present study demonstrated the mechanism of tumor-infiltrating mast cells stimulating ICOS+ regulatory T cells via the IL-33/IL-2 axis to promote the growth of gastric cancer. METHODS: Analyses of 98 patients with GC were conducted to examine mast cell counts, ICOS+ Tregs, and the levels of IL-33 or IL-2. Isolated ICOS+ Treg and CD8+ T cell were stimulated, cultured and tested for their functional abilities in vitro and in vivo. RESULTS: GC patients exhibited a significantly more production of IL-33 in tumors. Mast cell stimulated by tumor-derived IL-33 exhibited a prolonged lifespan through IL-33 mediated inhibition of apoptosis. Moreover, mast cells stimulated by tumor-derived IL-33 secreted IL-2, which induced Treg expansion. These inducible Tregs displayed an activated immunosuppressive phenotype with positive expression for the inducible T cell co-stimulator (ICOS). In vitro, IL-2 from IL to 33-stimulated mast cells induced increased numbers of ICOS+ Tregs with increased immunosuppressive activity against proliferation and effector function of CD8+ T cell. In vivo, ICOS+ Tregs were treated with anti-IL-2 neutralizing antibody followed by co-injection with CD8+ T cells in GC mouse model, which showed an increased CD8+ T cell infiltration and effector molecules production, meanwhile tumor growth and progression were inhibited. Besides, reduction in GC patient survival was associated with tumor-derived ICOS+ Tregs. CONCLUSION: Our results highlight a crosstalk between GC-infiltrating mast cells and ICOS+ Tregs and provide a novel mechanism describing ICOS+ Treg expansion and induction by an IL-33/mast cell/IL-2 signaling axis in GC, and also provide functional evidence that the modulation of this immunosuppressive pathway can attenuate GC-mediated immune tolerance.

Dysregulation of circulating T follicular helper cell subsets and their potential role in the pathogenesis of syphilis.

Introduction: The role of the host immune response could be critical in the development of Treponema pallidum (Tp) infection in individuals with latent syphilis. This study aims to investigate the alterations in T follicular helper T (Tfh) cell balance among patients with secondary syphilis and latent syphilis. Methods: 30 healthy controls (HCs), 24 secondary syphilis patients and 41 latent syphilis patients were enrolled. The percentages of total Tfh, ICOS+ Tfh, PD-1+ Tfh, resting Tfh, effector Tfh, naïve Tfh, effector memory Tfh, central memory Tfh,Tfh1, Tfh2, and Tfh17 cells in the peripheral blood were all determined by flow cytometry. Results: The percentage of total Tfh cells was significantly higher in secondary syphilis patients compared to HCs across various subsets, including ICOS+ Tfh, PD-1+ Tfh, resting Tfh, effector Tfh, naïve Tfh, effector memory Tfh, central memory Tfh, Tfh1, Tfh2, and Tfh17 cells. However, only the percentages of ICOS+ Tfh and effector memory Tfh cells showed significant increases in secondary syphilis patients and decreases in latent syphilis patients. Furthermore, the PD-1+ Tfh cells, central memory Tfh cells, and Tfh2 cells showed significant increases in latent syphilis patients, whereas naïve Tfh cells and Tfh1 cells exhibited significant decreases in secondary syphilis patients when compared to the HCs. However, no significant change was found in resting Tfh and effector Tfh in HCs and secondary syphilis patients or latent syphilis patients. Discussion: Dysregulated ICOS+ Tfh or effector memory Tfh cells may play an important role in immune evasion in latent syphilis patients.

Expression and prognosis of inducible T-cell co-stimulator and its ligand in Chinese stage I-III lung adenocarcinoma patients.

BACKGROUND: Immunotherapy has become the fastest-adopting treatment paradigm for lung cancer with improved survival. By binding with its ligand (inducible T-cell co-stimulator and its ligand [ICOSL]), an inducible T-cell co-stimulator (ICOS) could contribute to reversing immunosuppression and improving immune response and thus be a potential target for cancer immunotherapy. METHODS: We selected 54 formalin-fixed, paraffin-embedded tumor tissues from cases with stage I-III lung adenocarcinoma cancer. Immunohistochemical expression of ICOS and ICOSL was evaluated. The correlation with clinical parameters in Chinese patients was also compared with TCGA results. RESULTS: The positive rates of ICOS and ICOSL were 68% and 81.5%, respectively, in lung tumor tissues. Of these, 9 cases had a low expression of ICOS, and 22 cases had a high expression of ICOS; ICOSL expression was low in 20 cases and high in 24 cases. According to the International Association for the Study of Lung Cancer (8th edition), phase I lesions were detected in 21 cases, phase II lesions in 15 cases, and phase III lesions in 18 cases. The median survival time of all patients was 44.5 months, and the median disease-free survival was 32 months. Univariate analysis showed that the factors significantly associated with overall survival were tumor size, regional lymph node involvement, stage, and expression level of ICOS/ICOSL. Survival analysis using log-rank test indicated that the lower ICOS+ cell infiltration may predict poor prognosis, whereas lower ICOSL protein expression may be associated with better prognosis, but ICOSL data need further validation in larger samples due to inconsistency in TCGA mRNA prediction. CONCLUSION: ICOS/ICOSL might be associated with prognosis of lung cancer, and ICOS and its ligand may be potential therapeutic targets in non-small cell lung cancer.