CD160 serves as a negative regulator of NKT cells in acute hepatic injury

TIPE2 protein restrains invariant NKT activation and protects against immune-mediated hepatitis in mice

BACKGROUND AND AIMS

Concanavalin A (ConA) administration induces rapid and severe liver injury in mice, and invariant natural killer T (iNKT) cells are recognized to be the key effector cells in this process. However, the underlying regulatory mechanisms are not well defined.

APPROACH AND RESULTS

We found that iNKT cells constitutively expressed TIPE2 (tumor necrosis factor-α-induced protein 8-like 2, or TNFAIPL2). Genetic TIPE2 ablation strongly sensitized mice to ConA-induced hepatitis, accompanied by hyperactivation of iNKT cells. Moreover, Tipe2-/- mice were also more susceptible to α-galactosylceramide-induced liver injury, with elevated serum ALT levels and enhanced proinflammatory cytokine production. CD1d signaling blockade or iNKT cell elimination through antibodies reduced the effect of TIPE2 deficiency on liver injury. Mechanistic studies revealed that TIPE2 in iNKT cells functioned as a negative regulator, limiting iNKT cell activity and cytokine production through PIP3- AKT/mTOR pathway. TIPE2-mediated protection from liver injury was further validated by the administration of adeno-associated viruses expressing TIPE2, which effectively ameliorated ConA-induced hepatic injury. However, TIPE2 was dispensable in 2 other liver injury models, including D-GalN/LPS and acetaminophen-induced hepatitis.

CONCLUSIONS

Our findings reveal a new role of TIPE2 in the attenuation of iNKT cell-mediated hepatic injury. We propose that TIPE2 serves as an important regulator of immune homeostasis in the liver and might be exploited for the therapeutic treatment of autoimmune liver diseases.

Identification of tryptophan metabolism-related biomarkers for nonalcoholic fatty liver disease through network analysis

Background

Increasing evidence demonstrates that tryptophan metabolism is closely related to the development of nonalcoholic fatty liver disease (NAFLD). This study aimed to identify specific biomarkers of NAFLD associated with tryptophan metabolism and research its functional mechanism.

Methods

We downloaded NAFLD RNA-sequencing data from GSE89632 and GSE24807, and obtained tryptophan metabolism-related genes (TMRGs) from the MsigDB database. The R package limma and WGCNA were used to identify TMRGs-DEGs, and GO, KEGG and Cytoscape were used to analyze and visualize the data. Immune cell infiltration analysis was used to explore the immune mechanism of NAFLD and the biomarkers. We also validated extended levels of biomarkers.

Results

We identified 375 NAFLD differentially expressed genes (DEGs) and 85 TMRGs-DEGs. GO/KEGG analysis revealed that TMRGs-DEGs were mainly enriched in triglyceride and cholesterol metabolism. ROC curves identified CCL20 (AUC = 0.917), CD160 (AUC = 0.933) and CYP7A1 (AUC = 1) as biomarkers of NAFLD. Immune infiltration analysis showed significant differences in ten immune cells, and the activation of dendritic cells and mast cells were highly positively correlated with NAFLD. CCL20, CD160 and CYP7A1 were highly correlated with M2 macrophage, neutrophil and mast cells activation, respectively. Twenty-seven TMRGs correlated with hub genes, and gene set enrichment analysis demonstrated their function in tryptophan- and lysine-containing metabolic process. We identified 41 therapeutic drug matches which corresponded to two hub genes and four drugs which co-targeted CCL20 and CYP7A1. Finally, three hub genes were validated in our mouse model.

Conclusions

CCL20, CD160 and CYP7A1 are tryptophan metabolism-related biomarkers of NAFLD, related to glycerol ester and cholesterol metabolism. We screened four compounds which co-target CCL29 and CYP7A1 to provide potential experimental drugs for NAFLD.

Activatable Sulfur Dioxide Nanosonosensitizer Enables Precisely Controllable Sono-Gaseous Checkpoint Trimodal Therapy for Orthotopic Hepatocellular Carcinoma

Immune checkpoint blockade (ICB) is combined with sonodynamic therapy (SDT) to increase response rates and enhance anticancer efficacy. However, the "always on" property of most sonosensitizers in reducing tumor microenvironment (TME) compromises the therapeutic outcome of sonoimmunotherapy and exacerbates adverse side effects. Precisely controllable strategies combining sulfur dioxide (SO2) gas therapy with cancer immunotherapy can address these issues but remain lacking. Herein an "activatable SO2 nanosonosensitizer" for precise sono-gaseous checkpoint trimodal therapy of orthotopic hepatocellular carcinoma (HCC) is reported, whose full activity is initiated by ultrasound (US) irradiation in the reducing TME. This "activatable SO2 nanosonosensitizer," Aza-DNBS nanoparticles (NPs), are established by self-assembling Aza-boron-dipyrromethene based sonosensitizer molecules and 2,4-dinitrobenzenesulfonate (DNBS)-caged SO2 prodrug. The activity of Aza-DNBS NPs is initially silenced, and the sonodynamic, gaseous, and immunosuppressive TME reprogramming activities are precisely awakened under US irradiation. Due to the glutathione-responsiveness of Aza-DNBS NPs, Aza-DNBS NPs can generate large amounts of SO2 for gas therapy-enhanced SDT, which triggers robust immunogenic cell death activation and reprogramming of the immunosuppressive TME, thereby significantly suppressing orthotopic tumor growth and delaying lung metastasis. Thus, this study represents a strategy for designing a generic nanoplatform for precisely combined immunotherapy of orthotopic HCC.

The integrated molecular and histological analysis defines subtypes of esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is highly heterogeneous. Our understanding of full molecular and immune landscape of ESCC remains limited, hindering the development of personalised therapeutic strategies. To address this, we perform genomic-transcriptomic characterizations and AI-aided histopathological image analysis of 120 Chinese ESCC patients. Here we show that ESCC can be categorized into differentiated, metabolic, immunogenic and stemness subtypes based on bulk and single-cell RNA-seq, each exhibiting specific molecular and histopathological features based on an amalgamated deep-learning model. The stemness subgroup with signature genes, such as WFDC2, SFRP1, LGR6 and VWA2, has the poorest prognosis and is associated with downregulated immune activities, a high frequency of EP300 mutation/activation, functional mutation enrichment in Wnt signalling and the highest level of intratumoural heterogeneity. The immune profiling by transcriptomics and immunohistochemistry reveals ESCC cells overexpress natural killer cell markers XCL1 and CD160 as immune evasion. Strikingly, XCL1 expression also affects the sensitivity of ESCC cells to common chemotherapy drugs. This study opens avenues for ESCC treatment and provides a valuable public resource to better understand ESCC.

Internal regulation between constitutively expressed T cell co-inhibitory receptors BTLA and CD5 and tolerance in recent thymic emigrants

Immunologic self-tolerance involves signals from co-inhibitory receptors. Several T cell co-inhibitors, including PD-1, are expressed upon activation, whereas CD5 and BTLA are expressed constitutively. The relationship between constitutively expressed co-inhibitors and when they are needed is unknown. Deletion of Btla demonstrated BTLA regulates CD5 expression. Loss of BTLA signals, but not signalling by its ligand, HVEM, leads to increased CD5 expression. Higher CD5 expression set during thymic selection is associated with increased self-recognition, suggesting that BTLA might be needed early to establish self-tolerance. We found that BTLA and PD-1 were needed post-thymic selection in recent thymic emigrants (RTE). RTE lacking BTLA caused a CD4 T cell and MHC class II dependent multi-organ autoimmune disease. Together, our findings identify a negative regulatory pathway between two constitutively expressed co-inhibitors, calibrating their expression. Expression of constitutive and induced co-inhibitory receptors is needed early to establish tolerance in the periphery for RTE.

Pan-cancer analysis of immune checkpoint receptors and ligands in various cells in the tumor immune microenvironment

Drugs that target immune checkpoint have become the most popular weapon in cancer immunotherapy, yet only have practical benefits for a small percentage of patients. Tumor cells constantly interact with their microenvironment, which is made up of a variety of immune cells as well as endothelial cells and fibroblasts. Immune checkpoint expression and blocked signaling of immune cells in the tumor microenvironment (TME) are key to tumor progression. In this study, we perform deliberation convolution on the TCGA database for human lung, breast, and colorectal cancer to infer crosstalk between immune checkpoint receptors (ICRs) and ligands (ICLs) in TME of pan-carcinogenic solid tumor types, validated by flow cytometry. Analysis of immune checkpoints showed that there was little variation between different tumor types. It showed that CD160, LAG3, TIGIT were found to be highly expressed in CD8+ T cells instead of CD4+ T cells, PD-L1, PD-L2, CD86, LGALS9, TNFRSF14, LILRB4 and other ligands were highly expressed on macrophages, FVR, NECTIN2, FGL1 were highly expressed on Epithelial cells, CD200 was highly expressed in Endothelial cells, and CD80 was highly expressed in CD8 High expression on T cells. Overall, our study provides a new resource for the expression of immune checkpoints in TME on various types of cells. Significance: This study provides immune checkpoint expression of immune cells of multiple cancer types to infer immune mechanisms in the tumor microenvironment and provide ideas for the development of new immune checkpoint-blocking drugs.

Antigen Priming Induces Functional Reprogramming in iNKT Cells via Metabolic and Epigenetic Regulation: An Insight into iNKT Cell-Based Antitumor Immunotherapy

Dysfunction of intratumoral invariant natural killer T (iNKT) cells hinders their antitumor efficacy, but the underlying mechanisms and the relationship with endogenous antigen priming remain to be explored. Here, we report that antigen priming leads to metabolic reprogramming and epigenetic remodeling, which causes functional reprogramming in iNKT cells, characterized by limited cytokine responses upon restimulation but constitutive high cytotoxicity. Mechanistically, impaired oxidative phosphorylation (OXPHOS) in antigen-primed iNKT cells inhibited T-cell receptor signaling, as well as elevation of glycolysis, upon restimulation via reducing mTORC1 activation, and thus led to impaired cytokine production. However, the metabolic reprogramming in antigen-primed iNKT cells was uncoupled with their enhanced cytotoxicity; instead, epigenetic remodeling explained their high expression of granzymes. Notably, intratumoral iNKT cells shared similar metabolic reprogramming and functional reprogramming with antigen-primed iNKT cells due to endogenous antigen priming in tumors, and thus recovery of OXPHOS in intratumoral iNKT cells by ZLN005 successfully enhanced their antitumor responses. Our study deciphers the influences of antigen priming-induced metabolic reprogramming and epigenetic remodeling on functionality of intratumoral iNKT cells, and proposes a way to enhance efficacy of iNKT cell-based antitumor immunotherapy by targeting cellular metabolism.

The kinetics of inhibitory immune checkpoints during and post-COVID-19: the knowns and unknowns

The immune system is tightly regulated to prevent immune reactions to self-antigens and to avoid excessive immune responses during and after challenges from non-self-antigens. Inhibitory immune checkpoints (IICPs), as the major regulators of immune system responses, are extremely important for maintaining the homeostasis of cells and tissues. However, the high and sustained co-expression of IICPs in chronic infections, under persistent antigenic stimulations, results in reduced immune cell functioning and more severe and prolonged disease complications. Furthermore, IICPs-mediated interactions can be hijacked by pathogens in order to evade immune induction or effector mechanisms. Therefore, IICPs can be potential targets for the prognosis and treatment of chronic infectious diseases. This is especially the case with regards to the most challenging infectious disease of recent times, coronavirus disease-2019 (COVID-19), whose long-term complications can persist long after recovery. This article reviews the current knowledge about the kinetics and functioning of the IICPs during and post-COVID-19.

CD160 Signaling Is Essential for CD8+ T Cell Memory Formation via Upregulation of 4-1BB

A better understanding of the regulatory mechanisms governing the development of memory CD8+ T cells could provide instructive insights into vaccination strategies and T cell-based immunotherapies. In this article, we showed that CD160 surface protein is required for CD8+ T cell memory formation. In the response to acute lymphocytic choriomeningitis virus infection in a mouse model, CD160 ablation resulted in the failure of the development of all three memory CD8+ T cell subsets (central, effective, and tissue-resident memory), concomitant with a skewed differentiation into short-lived effector T cells. Such memory-related defect was manifested by a diminished protection from viral rechallenge. Mechanistically, CD160 deficiency led to downregulation of 4-1BB in activated CD8+ T cells, which contributes to the impaired cell survival and decreased respiratory capacity. The nexus between CD160 and 4-1BB was substantiated by the observation that ectopic introduction of 4-1BB was able to largely complement the loss of CD160 in memory CD8+ T cell development. Collectively, our studies discovered that CD160, once thought to be a coinhibitor of T cell signaling, is an essential promoter of memory CD8+ T cell development via activation of the costimulatory molecule 4-1BB.

Exogenous Interleukin-37 Alleviates Hepatitis with Reduced Dendritic Cells and Induced Regulatory T Cells in Acute Murine Cytomegalovirus Infection

Human cytomegalovirus (HCMV) infection is globally distributed, and the liver is one of the major targeting organs. So far, the mechanisms for cell and organ damage have not fully been elucidated and the treatments for the infection are mainly at symptoms. IL-37 has shown a protective role in certain inflammatory diseases. In the present study, potential protective effect of exogenous IL-37 on murine cytomegalovirus- (MCMV-) infected hepatitis was evaluated through analyses of serum transaminases, the liver histopathology and cytokine expression, and functional state of dendritic cells (DCs) and regulatory T cells (Tregs). These analyses showed a significant decrease in serum transaminase levels and a lower Ishak histopathologic score at the early stage of MCMV-infected mice with exogenous IL-37 pretreatment. The frequencies of MHC-Ⅱ, CD40, CD80, and CD86 positive DCs in the liver and spleen were decreased significantly at 7 days postinfection (dpi) in MCMV-infected mice with IL-37 pretreatment when compared with those without the pretreatment, while the total number of DCs in the liver was reduced in IL-37-pretreated mice. The induction of Tregs in the spleen was enhanced at dpi 3 with IL-37 pretreatment in MCMV-infected mice. The mRNA expression levels of cytokines in the liver were decreased significantly (IL-1β, IL-6, IL-10, IL-4) or to some extent (TGF-β and TNF-α). The present study suggested that exogenous IL-37 can alleviate MCMV-infected hepatitis, likely through reduced DCs and induced Tregs with a weaker cytokine storm, demonstrating its potential value in clinical management for HCMV-infected hepatitis.

Single-cell sequencing of PIT1-positive pituitary adenoma highlights the pro-tumour microenvironment mediated by IFN-γ-induced tumour-associated fibroblasts remodelling

BACKGROUND

PIT1-positive pituitary adenoma (PIT1-PA) is one of the most important lineages of pituitary adenoma (PA), which causes systematic endocrine disorders and a worse prognosis. Tumour-associated fibroblast (TAF) is a crucial stroma cell type in the tumour microenvironment (TME). However, cellular and functional heterogeneity of TAF and immune cells in PIT1-PA have not been fully investigated.

METHODS

By single-cell RNA sequencing of four PIT1-PAs and further analyses, we characterised the molecular and functional profiles of 28 different cell subtypes.

RESULTS

PA stem cells in PIT1/SF1-positve PA were in a hybrid epithelial/mesenchymal state, and differentiated along the PIT1- and SF- dependent branches. C1Q was overwhelmingly expressed in tumour-associated macrophages, indicating its pro-tumoral functionality. PIT1-PA progression was characterised by lower cell-cell communication strength and higher cell adhesion-associated signals, indicating the immunosuppressive but pro-invasive microenvironment. IFN-γ signal repressed functional remodelling of myofibroblastic TAF (mTAF) towards inflammatory TAF/antigen-presenting TAF. IFN-γ inhibited mTAF phenotypes and N-cadherin expression through STAT3 signal axis. CDH2 knockdown in TAFs abrogated their pro-tumour function in PAs.

CONCLUSIONS

Our study builds up a cellular landscape of PIT1-PA TME and highlights anti-tumour function of IFN-γ mediated TAF remodelling, which benefits clinical treatments and drug development.

Genetic deletion of HVEM in a leukemia B cell line promotes a preferential increase of PD-1- stem cell-like T cells over PD-1+ T cells curbing tumor progression

INTRODUCTION

A high frequency of mutations affecting the gene encoding Herpes Virus Entry Mediator (HVEM, TNFRSF14) is a common clinical finding in a wide variety of human tumors, including those of hematological origin.

METHODS

We have addressed how HVEM expression on A20 leukemia cells influences tumor survival and its involvement in the modulation of the anti-tumor immune responses in a parental into F1 mouse tumor model of hybrid resistance by knocking-out HVEM expression. HVEM WT or HVEM KO leukemia cells were then injected intravenously into semiallogeneic F1 recipients and the extent of tumor dissemination was evaluated.

RESULTS

The loss of HVEM expression on A20 leukemia cells led to a significant increase of lymphoid and myeloid tumor cell infiltration curbing tumor progression. NK cells and to a lesser extent NKT cells and monocytes were the predominant innate populations contributing to the global increase of immune infiltrates in HVEM KO tumors compared to that present in HVEM KO tumors. In the overall increase of the adaptive T cell immune infiltrates, the stem cell-like PD-1- T cells progenitors and the effector T cell populations derived from them were more prominently present than terminally differentiated PD-1+ T cells.

CONCLUSIONS

These results suggest that the PD-1- T cell subpopulation is likely to be a more relevant contributor to tumor rejection than the PD-1+ T cell subpopulation. These findings highlight the role of co-inhibitory signals delivered by HVEM upon engagement of BTLA on T cells and NK cells, placing HVEM/BTLA interaction in the spotlight as a novel immune checkpoint for the reinforcement of the anti-tumor responses in malignancies of hematopoietic origin.

LEF1 Drives a Central Memory Program and Supports Antitumor Activity of Natural Killer T Cells

Vα24-invariant natural killer T cells (NKT) possess innate antitumor properties that can be exploited for cancer immunotherapy. We have shown previously that the CD62L+ central memory-like subset of these cells drives the in vivo antitumor activity of NKTs, but molecular mediators of NKT central memory differentiation remain unknown. Here, we demonstrate that relative to CD62L- cells, CD62L+ NKTs express a higher level of the gene encoding the Wnt/β-catenin transcription factor lymphoid enhancer binding factor 1 (LEF1) and maintain active Wnt/β-catenin signaling. CRISPR/Cas9-mediated LEF1 knockout reduced CD62L+ frequency after antigenic stimulation, whereas Wnt/β-catenin activator Wnt3a ligand increased CD62L+ frequency. LEF1 overexpression promoted NKT expansion and limited exhaustion following serial tumor challenge and was sufficient to induce a central memory-like transcriptional program in NKTs. In mice, NKTs expressing a GD2-specific chimeric-antigen receptor (CAR) with LEF1 demonstrated superior control of neuroblastoma xenograft tumors compared with control CAR-NKTs. These results identify LEF1 as a transcriptional activator of the NKT central memory program and advance development of NKT cell-based immunotherapy. See related Spotlight by Van Kaer, p. 144.

CD160 receptor in CLL: Current state and future avenues

CD160 is a glycosylphosphatidylinositol (GPI)-anchored cell surface glycoprotein expressed on cytotoxic natural killer (NK) cells and T-cell subsets. It plays a crucial role in the activation of NK-cell cytotoxicity and cytokine production. It also modulates the immune system and is involved in some pathologies, such as cancer. CD160 is abnormally expressed in B-cell chronic lymphocytic leukemia (CLL) but not expressed in normal B lymphocytes. Its expression in CLL enhances tumor cell proliferation and resistance to apoptosis. CD160 is also a potential prognostic marker for the detection of minimal residual disease (MRD) in CLL, which is important for the clinical management of CLL, the prevention of disease relapse, and the achievement of complete remission. In this review, we present an overview of CD160 and its involvement in the pathophysiology of CLL. We also discuss its use as a prognostic marker for the assessment of MRD in CLL.

Immunomodulatory Factor TIM3 of Cytolytic Active Genes Affected the Survival and Prognosis of Lung Adenocarcinoma Patients by Multi-Omics Analysis

[Objective] Using multi-omics research methods to explore cytolytic activity-related genes through the immunoregulatory factors HAVCR2 (TIM3) affecting the survival and prognosis of lung adenocarcinoma. [Methods] We combined Cox single factor regression and lasso regression feature selection algorithm to screen out the key genes of cytolytic activity in lung adenocarcinoma, and applied multi-omics research to explore the clinical predictive value of the model, including onset risk, independent prognosis, clinical relevance, signal transduction pathways, drug sensitivity, and the correlation of immune regulatory factors, etc. TCGA data are used as the experimental group, and GEO data is used as the external data control group to verify the stability of the model. The survival curve was generated by the Kaplan–Meier method and compared by log-rank, and the Cox proportional hazard model was used for multivariate analysis. In this study, 10 fresh tissue samples of lung adenocarcinoma were collected for cellular immunohistochemical experiments to analyze the expression of immunoregulatory factors in cancer tissues, and the key immunoregulatory factors were verified and screened out. [Results] A total of 450 genes related to cytolytic activity were differentially expressed, of which 273 genes were up-regulated and 177 genes were down-regulated. A total of 91 key genes related to cytolytic activity related to the prognosis of lung adenocarcinoma were screened through Cox single factor regression. The ROC curve results showed that the AUC values of 1, 3, and 5 years in the training set and test set were all greater than 0.7, indicating that the model has a valid verification. The level of risk score is significantly related to the sensitivity of patients to AKT inhibitor VIII, Lenalidomide, and Tipifarnib. In addition, our study also found that receptor and MHC genes related to immunomodulatory, and chemokines, including HAVCR2, are more highly expressed in the low-risk group. [Conclusions] HAVCR2 (TIM3) immunoregulatory factors affect the expression of key genes that affect cytolytic activity in lung adenocarcinoma cells, and to some extent indirectly affect the survival and prognosis of patients with lung adenocarcinoma.

BTLA inhibition has a dominant role in the cis-complex of BTLA and HVEM

The engagement of the herpesvirus entry mediator (HVEM, TNFRSF14) by the B and T lymphocyte attenuator (BTLA) represents a unique interaction between an activating receptor of the TNFR-superfamily and an inhibitory receptor of the Ig-superfamily. BTLA and HVEM have both been implicated in the regulation of human T cell responses, but their role is complex and incompletely understood. Here, we have used T cell reporter systems to dissect the complex interplay of HVEM with BTLA and its additional ligands LIGHT and CD160. Co-expression with LIGHT or CD160, but not with BTLA, induced strong constitutive signaling via HVEM. In line with earlier reports, we observed that in cis interaction of BTLA and HVEM prevented HVEM co-stimulation by ligands on surrounding cells. Intriguingly, our data indicate that BTLA mediated inhibition is not impaired in this heterodimeric complex, suggesting a dominant role of BTLA co-inhibition. Stimulation of primary human T cells in presence of HVEM ligands indicated a weak costimulatory capacity of HVEM potentially owed to its in cis engagement by BTLA. Furthermore, experiments with T cell reporter cells and primary T cells demonstrate that HVEM antibodies can augment T cell responses by concomitantly acting as checkpoint inhibitors and co-stimulation agonists.

Identification of Distinct Immune Cell Subsets Associated With Asymptomatic Infection, Disease Severity, and Viral Persistence in COVID-19 Patients

The cell-mediated protective and pathogenic immune responses to SARS-CoV-2 infection remain largely elusive. Here we identified 76 distinct cell subsets in the PBMC samples that were associated with various clinical presentations of COVID-19 using scRNA-seq technology coupled with a deep and comprehensive analysis of unique cell surface markers and differentially expressed genes. We revealed that (TRAV1-2⁺CD8⁺)MAIT cells and (NCAM1^hiCD160⁺)NK cells significantly enriched in the asymptomatic subjects whereas (LAG3⁺CD160⁺CD8⁺)NKT cells increased in the symptomatic patients. We also observed that (CD68^-CSF1R^-IL1B^hiCD14⁺)classical monocytes were positively correlated with the disease severity. Moreover, (CD33^-HLA-DMA^-CD14⁺)classical monocytes and (CLEC10A^-S100A9^lo)pDC were associated with the viral persistence. The GO and KEGG analyses identified enriched pathways related to immune responses, inflammation, and apoptosis. These findings may enhance our understanding of the immunopathogenesis of COVID-19 and help develop novel strategies against SARS-CoV-2 infection.

The impact of CD160 deficiency on alloreactive CD8 T cell responses and allograft rejection

CD160 is a member of the immunoglobulin superfamily with a pattern of expression mainly restricted to cytotoxic cells. To assess the functional relevance of the HVEM/CD160 signaling pathway in allogeneic cytotoxic responses, exon 2 of the CD160 gene was targeted by CRISPR/Cas9 to generate CD160 deficient mice. Next, we evaluated the impact of CD160 deficiency in the course of an alloreactive response. To that aim, parental donor WT (wild-type) or CD160 KO (knock-out) T cells were adoptively transferred into non-irradiated semiallogeneic F1 recipients, in which donor alloreactive CD160 KO CD4 T cells and CD8 T cells clonally expanded less vigorously than in WT T cell counterparts. This differential proliferative response rate at the early phase of T cell expansion influenced the course of CD8 T cell differentiation and the composition of the effector T cell pool that led to a significant decreased of the memory precursor effector cells (MPECs) / short-lived effector cells (SLECs) ratio in CD160 KO CD8 T cells compared to WT CD8 T cells. Despite these differences in T cell proliferation and differentiation, allogeneic MHC class I mismatched (bm1) skin allograft survival in CD160 KO recipients was comparable to that of WT recipients. However, the administration of CTLA-4.Ig showed an enhanced survival trend of bm1 skin allografts in CD160 KO with respect to WT recipients. Finally, CD160 deficient NK cells were as proficient as CD160 WT NK cells in rejecting allogeneic cellular allografts or MHC class I deficient tumor cells. CD160 may represent a CD28 alternative costimulatory molecule for the modulation of allogeneic CD8 T cell responses either in combination with costimulation blockade or by direct targeting of alloreactive CD8 T cells that upregulate CD160 expression in response to alloantigen stimulation.

HVEM structures and mutants reveal distinct functions of binding to LIGHT and BTLA/CD160

HVEM is a TNF (tumor necrosis factor) receptor contributing to a broad range of immune functions involving diverse cell types. It interacts with a TNF ligand, LIGHT, and immunoglobulin (Ig) superfamily members BTLA and CD160. Assessing the functional impact of HVEM binding to specific ligands in different settings has been complicated by the multiple interactions of HVEM and HVEM binding partners. To dissect the molecular basis for multiple functions, we determined crystal structures that reveal the distinct HVEM surfaces that engage LIGHT or BTLA/CD160, including the human HVEM-LIGHT-CD160 ternary complex, with HVEM interacting simultaneously with both binding partners. Based on these structures, we generated mouse HVEM mutants that selectively recognized either the TNF or Ig ligands in vitro. Knockin mice expressing these muteins maintain expression of all the proteins in the HVEM network, yet they demonstrate selective functions for LIGHT in the clearance of bacteria in the intestine and for the Ig ligands in the amelioration of liver inflammation.

HO-1/BMMSC perfusion using a normothermic machine perfusion system reduces the acute rejection of DCD liver transplantation by regulating NKT cell co-inhibitory receptors in rats

Background

Liver transplantation (LT) is required in many end-stage liver diseases. Donation after cardiac death (DCD) livers are often used, and treatment of acute rejection (ACR) requires the use of immunosuppressive drugs that are associated with complications. Bone marrow mesenchymal stem cells (BMMSCs) are used in treatment following LT; however, they have limitations, including low colonization in the liver. An optimized BMMSC application method is required to suppress ACR.

Methods

BMMSCs were isolated and modified with the heme oxygenase 1 (HO-1) gene. HO-1/BMMSCs were perfused into donor liver in vitro using a normothermic machine perfusion (NMP) system, followed by LT into rats. The severity of ACR was evaluated based on liver histopathology. Gene chip technology was used to detect differential gene expression, and flow cytometry to analyze changes in natural killer (NK) T cells.

Results

NMP induced BMMSCs to colonize the donor liver during in vitro preservation. The survival of HO-1/BMMSCs in liver grafts was significantly longer than that of unmodified BMMSCs. When the donor liver contained HO-1/BMMSCs, the local immunosuppressive effect was improved and prolonged, ACR was controlled, and survival time was significantly prolonged. The application of HO-1/BMMSCs reduced the number of NKT cells in liver grafts, increased the expression of NKT cell co-inhibitory receptors, and reduced NKT cell expression of interferon-γ.

Conclusions

NK cell and CD8⁺ T cell activation was inhibited by application of HO-1/BMMSCs, which reduced ACR of transplanted liver. This approach could be developed to enhance the success rate of LT.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02647-5.

Allosteric regulation of binding specificity of HVEM for CD160 and BTLA ligands upon G89F mutation

Molecular interactions mediated by engagement of the Herpes virus entry mediator (HVEM) with members of TNF and Ig superfamily generate distinct signals in T cell activation pathways that modulate inflammatory and inhibitory responses. HVEM interacts with CD160 and B and T lymphocyte attenuator (BTLA), both members of the immunoglobulin (Ig) superfamily, which share a common binding site that is unique from that of LIGHT, a TNF ligand. BTLA or CD160 engagement with HVEM deliver inhibitory or stimulatory signals to the host immune response in a context dependent fashion, whereas HVEM engagement with LIGHT results in pro-inflammatory responses. We identified a mutation in human HVEM, G89F, which directly interferes with the human LIGHT interaction, but interestingly, also differentially modulates the binding of human BTLA and CD160 via an apparent allosteric mechanism involving recognition surfaces remote from the site of the mutation. Specifically, the G89F mutation enhances binding of CD160, while decreasing that of BTLA to HVEM in cell-based assays. Molecular dynamics simulations for wild-type and G89F mutant HVEM, bound to different sets of ligands, were performed to define the molecular basis of this unexpected allosteric effect. These results were leveraged to design additional human HVEM mutants with altered binding specificities.

SRSF1 plays a critical role in invariant natural killer T cell development and function

Invariant natural killer T (iNKT) cells are highly conserved innate-like T lymphocytes that originate from CD4⁺CD8⁺ double-positive (DP) thymocytes. Here, we report that serine/arginine splicing factor 1 (SRSF1) intrinsically regulates iNKT cell development by directly targeting Myb and balancing the abundance of short and long isoforms. Conditional ablation of SRSF1 in DP cells led to a substantially diminished iNKT cell pool due to defects in proliferation, survival, and TCRα rearrangement. The transition from stage 0 to stage 1 of iNKT cells was substantially blocked, and the iNKT2 subset was notably diminished in SRSF1-deficient mice. SRSF1 deficiency resulted in aberrant expression of a series of regulators that are tightly correlated with iNKT cell development and iNKT2 differentiation, including Myb, PLZF, Gata3, ICOS, and CD5. In particular, we found that SRSF1 directly binds and regulates pre-mRNA alternative splicing of Myb and that the expression of the short isoform of Myb is substantially reduced in SRSF1-deficient DP and iNKT cells. Strikingly, ectopic expression of the Myb short isoform partially rectified the defects caused by ablation of SRSF1. Furthermore, we confirmed that the SRSF1-deficient mice exhibited resistance to acute liver injury upon α-GalCer and Con A induction. Our findings thus uncovered a previously unknown role of SRSF1 as an essential post-transcriptional regulator in iNKT cell development and functional differentiation, providing new clinical insights into iNKT-correlated disease.

CD160 protein as a new therapeutic target in a battle against autoimmune, infectious and lifestyle diseases. Analysis of the structure, interactions and functions

The glycosylphosphatidylinositol-anchored transmembrane glycoprotein CD160 (cluster of differentiation 160) is a member of the immunoglobulin superfamily. Four isoforms, which differ by the presence or absence of an immunoglobulin-like domain and the mode of anchoring in the cell membrane, have been identified. CD160 has a significant impact on the proper functioning of the immune system by activating natural killer cells and inhibiting T cells. CD160 is a natural ligand for herpes virus entry mediator (HVEM), a member of the tumor necrosis factor superfamily. The CD160-HVEM complex is a rare example of direct interaction between the two different superfamilies. The interaction of these two proteins leads to the inhibition of CD4⁺ T cells which, in consequence, leads to the inhibition of the correct response of the immune system. Available research articles indicate that CD160 plays a role in various types of cancer, chronic viral diseases, malaria, paroxysmal nocturnal hemoglobinuria, atherosclerosis, autoimmune diseases, skin inflammation, acute liver damage and retinal vascular disease. We present here an overview of the CD160 protein, the general characteristics of the receptor and its isoforms, details of structural studies of CD160 and the CD160-HVEM complex, as well as a description of the role of this protein in selected human diseases.

Ectopic Expression of Human Thymosin β4 Confers Resistance to Legionella pneumophila during Pulmonary and Systemic Infection in Mice

Thymosin beta-4 (Tβ4) is an actin-sequestering peptide that plays important roles in regeneration and remodeling of injured tissues. However, its function in a naturally occurring pathogenic bacterial infection model has remained elusive. We adopted Tβ4-overexpressing transgenic (Tg) mice to investigate the role of Tβ4 in acute pulmonary infection and systemic sepsis caused by Legionella pneumophila Upon infection, Tβ4-Tg mice demonstrated significantly lower bacterial loads in the lung, less hyaline membranes and necrotic abscess, with lower interstitial infiltration of neutrophils, CD4⁺, and CD8⁺ T cells. Bronchoalveolar lavage fluid of Tβ4-Tg mice possessed higher bactericidal activity against exogenously added L. pneumophila, suggesting that constitutive expression of Tβ4 could efficiently control L. pneumophila Furthermore, qPCR analysis of lung homogenates demonstrated significant reduction of interleukin 1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α), which primarily originate from lung macrophages, in Tβ4-Tg mice after pulmonary infection. Upon L. pneumophila challenge of bone marrow-derived macrophages (BMDM) in vitro, secretion of IL-1β and TNF-α proteins was also reduced in Tβ4-Tg macrophages, without affecting their survival. The anti-inflammatory effects of BMDM in Tβ4-Tg mice on each cytokine were affected when triggering with tlr2, tlr4, tlr5, or tlr9 ligands, suggesting that anti-inflammatory effects of Tβ4 are likely mediated by the reduced activation of Toll-like receptors (TLR). Finally, Tβ4-Tg mice in a systemic sepsis model were protected from L. pneumophila-induced lethality compared to wild-type controls. Therefore, Tβ4 confers effective resistance against L. pneumophila via two pathways, a bactericidal and an anti-inflammatory pathway, which can be harnessed to treat acute pneumonia and septic conditions caused by L. pneumophila in humans.

Functional Analysis of Immune Signature Genes in Th1* Memory Cells Links ISOC1 and Pyrimidine Metabolism to IFN-γ and IL-17 Production

CCR6+CXCR3+CCR4-CD4+ memory T cells, termed Th1*, are important for long-term immunity to Mycobacterium tuberculosis and the pathogenesis of autoimmune diseases. Th1* cells express a unique set of lineage-specific transcription factors characteristic of both Th1 and Th17 cells and display distinct gene expression profiles compared with other CD4+ T cell subsets. To examine molecules and signaling pathways important for the effector function of Th1* cells, we performed loss-of-function screening of genes selectively enriched in the Th1* subset. The genetic screen yielded candidates whose depletion significantly impaired TCR-induced IFN-γ production. These included genes previously linked to IFN-γ or M. tuberculosis susceptibility and novel candidates, such as ISOC1, encoding a metabolic enzyme of unknown function in mammalian cells. ISOC1-depleted T cells, which produced less IFN-γ and IL-17, displayed defects in oxidative phosphorylation and glycolysis and impairment of pyrimidine metabolic pathway. Supplementation with extracellular pyrimidines rescued both bioenergetics and IFN-γ production in ISOC1-deficient T cells, indicating that pyrimidine metabolism is a key driver of effector functions in CD4+ T cells and Th1* cells. Results provide new insights into the immune-stimulatory function of ISOC1 as well as the particular metabolic requirements of human memory T cells, providing a novel resource for understanding long-term T cell-driven responses.

RNA delivery by extracellular vesicles in mammalian cells and its applications

The term 'extracellular vesicles' refers to a heterogeneous population of vesicular bodies of cellular origin that derive either from the endosomal compartment (exosomes) or as a result of shedding from the plasma membrane (microvesicles, oncosomes and apoptotic bodies). Extracellular vesicles carry a variety of cargo, including RNAs, proteins, lipids and DNA, which can be taken up by other cells, both in the direct vicinity of the source cell and at distant sites in the body via biofluids, and elicit a variety of phenotypic responses. Owing to their unique biology and roles in cell-cell communication, extracellular vesicles have attracted strong interest, which is further enhanced by their potential clinical utility. Because extracellular vesicles derive their cargo from the contents of the cells that produce them, they are attractive sources of biomarkers for a variety of diseases. Furthermore, studies demonstrating phenotypic effects of specific extracellular vesicle-associated cargo on target cells have stoked interest in extracellular vesicles as therapeutic vehicles. There is particularly strong evidence that the RNA cargo of extracellular vesicles can alter recipient cell gene expression and function. During the past decade, extracellular vesicles and their RNA cargo have become better defined, but many aspects of extracellular vesicle biology remain to be elucidated. These include selective cargo loading resulting in substantial differences between the composition of extracellular vesicles and source cells; heterogeneity in extracellular vesicle size and composition; and undefined mechanisms for the uptake of extracellular vesicles into recipient cells and the fates of their cargo. Further progress in unravelling the basic mechanisms of extracellular vesicle biogenesis, transport, and cargo delivery and function is needed for successful clinical implementation. This Review focuses on the current state of knowledge pertaining to packaging, transport and function of RNAs in extracellular vesicles and outlines the progress made thus far towards their clinical applications.

CD160 Plays a Protective Role During Chronic Infection by Enhancing Both Functionalities and Proliferative Capacity of CD8+ T Cells

The understanding of protective immunity during HIV infection remains elusive. Here we showed that CD160 defines a polyfunctional and proliferative CD8+ T cell subset with a protective role during chronic HIV-1 infection. CD160+ CD8+ T cells derived from HIV+ patients correlated with slow progressions both in a cross-sectional study and in a 60-month longitudinal cohort, displaying enhanced cytotoxicity and proliferative capacity in response to HIV Gag stimulation; triggering CD160 promoted their functionalities through MEK-ERK and PI3K-AKT pathways. These observations were corroborated by studying chronic lymphocytic choriomeningitis virus (LCMV) infection in mice. The genetic ablation of CD160 severely impaired LCMV-specific CD8+ T cell functionalities and thereby resulted in loss of virus control. Interestingly, transcriptional profiling showed multiple costimulatory and survival pathways likely to be involved in CD160+ T cell development. Our data demonstrated that CD160 acts as a costimulatory molecule positively regulating CD8+ T cells during chronic viral infections, thus representing a potential target for immune intervention.