CD226 (DNAM-1) is involved in lymphocyte function-associated antigen 1 costimulatory signal for naive T cell differentiation and proliferation

Inhibition of CD226 co-stimulation suppresses diabetes development in the NOD mouse by augmenting regulatory T cells and diminishing effector T cell function

AIMS/HYPOTHESIS

Immunotherapeutics targeting T cells are crucial for inhibiting autoimmune disease progression proximal to disease onset in type 1 diabetes. There is an outstanding need to augment the durability and effectiveness of T cell targeting therapies by directly restraining proinflammatory T cell subsets, while simultaneously augmenting regulatory T cell (Treg) activity. Here, we present a novel strategy for preventing diabetes incidence in the NOD mouse model using a blocking monoclonal antibody targeting the type 1 diabetes risk-associated T cell co-stimulatory receptor, CD226.

METHODS

Female NOD mice were treated with anti-CD226 at 7-8 weeks of age and then monitored for diabetes incidence and therapeutic mechanism of action.

RESULTS

Compared with isotype-treated controls, anti-CD226-treated NOD mice showed reduced insulitis severity (0.84-fold, p=0.0002) at 12 weeks and decreased disease incidence (HR 0.41, p=0.015) at 30 weeks. Flow cytometric analysis performed 5 weeks post treatment demonstrated reduced proliferation of conventional CD4+ T cells (0.87-fold, p=0.030) and CD8+ (0.78-fold, p=0.0018) effector memory T cells in spleens of anti-CD226-treated mice. Phenotyping of pancreatic Tregs revealed increased CD25 expression (2.05-fold, p=0.0073) and signal transducer and activator of transcription 5 (STAT5) phosphorylation (1.39-fold, p=0.0007) following anti-CD226, with splenic Tregs displaying augmented suppression of CD4+ responder T cells (Tresps) (1.49-fold, p=0.0008, 1:2 Treg:Tresp) in vitro. Anti-CD226-treated mice exhibited reduced frequencies of islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP)-reactive CD8+ T cells in the pancreas, using both ex vivo tetramer staining (0.50-fold, p=0.0317) and single-cell T cell receptor sequencing (0.61-fold, p=0.022) approaches. 51Cr-release assays demonstrated reduced cell-mediated lysis of beta cells (0.61-fold, p<0.0001, 1:1 effector:target) by anti-CD226-treated autoreactive cytotoxic T lymphocytes.

CONCLUSIONS/INTERPRETATION

CD226 blockade reduces T cell cytotoxicity and improves Treg function, representing a targeted and rational approach for restoring immune regulation in type 1 diabetes.

CD226 identifies effector CD8 + T cells during tuberculosis and costimulates recognition of Mycobacterium tuberculosis -infected macrophages

CD8 + T cells defend against Mycobacterium tuberculosis (Mtb) infection but variably recognize Mtb-infected macrophages. To define how the diversity of lung parenchymal CD8 + T cells changes during chronic infection, cells from C57BL/6J mice infected for 6- and 41-weeks were analyzed by scRNA-seq. We identified an effector lineage, including a cluster that expresses high levels of cytotoxic effectors and cytokines, and dysfunctional lineage that transcriptionally resembles exhausted T cells. The most significant differentially expressed gene between two distinct CD8 + T cell lineages is CD226. Mtb-infected IFNγ-eYFP reporter mice revealed IFNγ production is enriched in CD226 + CD8 + T cells, confirming these as functional T cells in vivo. Purified CD226 + but not CD226 - CD8 + T cells recognize Mtb-infected macrophages, and CD226 blockade inhibits IFNγ and granzyme B production. Thus, CD226 costimulation is required for efficient CD8 + T cell recognition of Mtb-infected macrophages, and its expression identifies CD8 + T cells that recognize Mtb-infected macrophages.

One Sentence Summary

Shinkawa et al. discover that CD226 is a functional marker that distinguishes effector from dysfunctional CD8 + T cells in the Mycobacterium tuberculosis (Mtb)-infected lung and has a crucial role in costimulating CD8 + T cell recognition of Mtb-infected macrophages.

Impact of the Multiple Sclerosis-Associated Genetic Variant CD226 Gly307Ser on Human CD8 T-Cell Functions

BACKGROUND AND OBJECTIVES

The rs763361 nonsynonymous variant in the CD226 gene, which results in a glycine-to-serine substitution at position 307 of the CD226 protein, has been implicated as a risk factor of various immune-mediated diseases, including multiple sclerosis (MS). Compelling evidence suggests that this allele may play a significant role in predisposing individuals to MS by decreasing the immune-regulatory capacity of Treg cells and increasing the proinflammatory potential of effector CD4 T cells. However, the impact of this CD226 gene variant on CD8 T-cell functions, a population that also plays a key role in MS, remains to be determined.

METHODS

To study whether the CD226 risk variant affects human CD8 T-cell functions, we used CD8 T cells isolated from peripheral blood mononuclear cell of 16 age-matched healthy donors homozygous for either the protective or the risk allele of CD226. We characterized these CD8 T cells on T-cell receptor (TCR) stimulation using high-parametric flow cytometry and bulk RNAseq and through characterization of canonical signaling pathways and cytokine production.

RESULTS

On TCR engagement, the phenotype of ex vivo CD8 T cells bearing the protective (CD226-307Gly) or the risk (CD226-307Ser) allele of CD226 was largely overlapping. However, the transcriptomic signature of CD8 T cells from the donors carrying the risk allele presented an enrichment in TCR, JAK/STAT, and IFNγ signaling. We next found that the CD226-307Ser risk allele leads to a selective increase in the phosphorylation of the mitogen-activated protein kinases extracellular signal-regulated kinases 1 and 2 (ERK1/2) associated with enhanced phosphorylation of STAT4 and increased production of IFNγ.

DISCUSSION

Our data suggest that the CD226-307Ser risk variant imposes immune dysregulation by increasing the pathways related to IFNγ signaling in CD8 T cells, thereby contributing to the risk of developing chronic inflammation.

Revisiting T-cell adhesion molecules as potential targets for cancer immunotherapy: CD226 and CD2

Cancer immunotherapy aims to initiate or amplify immune responses that eliminate cancer cells and create immune memory to prevent relapse. Immune checkpoint inhibitors (ICIs), which target coinhibitory receptors on immune effector cells, such as CTLA-4 and PD-(L)1, have made significant strides in cancer treatment. However, they still face challenges in achieving widespread and durable responses. The effectiveness of anticancer immunity, which is determined by the interplay of coinhibitory and costimulatory signals in tumor-infiltrating immune cells, highlights the potential of costimulatory receptors as key targets for immunotherapy. This review explores our current understanding of the functions of CD2 and CD226, placing a special emphasis on their potential as novel agonist targets for cancer immunotherapy. CD2 and CD226, which are present mainly on T and NK cells, serve important functions in cell adhesion and recognition. These molecules are now recognized for their costimulatory benefits, particularly in the context of overcoming T-cell exhaustion and boosting antitumor responses. The importance of CD226, especially in anti-TIGIT therapy, along with the CD2‒CD58 axis in overcoming resistance to ICI or chimeric antigen receptor (CAR) T-cell therapies provides valuable insights into advancing beyond the current barriers of cancer immunotherapy, underscoring their promise as targets for novel agonist therapy.

Meta-analysis of the Selected Genetic Variants in Immune-Related Genes and Multiple Sclerosis Risk

Previous studies have suggested that certain variants in immune-related genes may participate in the pathogenesis of multiple sclerosis (MS), including rs17824933 in the CD6 gene, rs1883832 in the CD40 gene, rs2300747 in the CD58 gene, rs763361 in the CD226 gene, rs16944 in the IL-1β gene, rs2243250 in the IL-4 gene, and rs12722489 and rs2104286 in the IL-2Rα gene. However, the results remained inconclusive and conflicting. In view of this, a comprehensive meta-analysis including all eligible studies was conducted to investigate the association between these 8 selected genetic variants and MS risk. Up to June 2023, 64 related studies were finally included in this meta-analysis. The odds ratios (ORs) and corresponding 95% confidence intervals (CIs) calculated by the random-effects model were used to evaluate the strength of association. Publication bias test, sensitivity analyses, and trial sequential analysis (TSA) were conducted to examine the reliability of statistical results. Our results indicated that rs17824933 in the CD6 gene, rs1883832 in the CD40 gene, rs2300747 in the CD58 gene, rs763361 in the CD226 gene, and rs12722489 and rs2104286 in the IL-2Rα gene may serve as the susceptible factors for MS pathogenesis, while rs16944 in the IL-1β gene and rs2243250 in the IL-4 gene may not be associated with MS risk. However, the present findings need to be confirmed and reinforced in future studies.

Focusing on CD8+ T-cell phenotypes: improving solid tumor therapy

Vigorous CD8+ T cells play a crucial role in recognizing tumor cells and combating solid tumors. How T cells efficiently recognize and target tumor antigens, and how they maintain the activity in the "rejection" of solid tumor microenvironment, are major concerns. Recent advances in understanding of the immunological trajectory and lifespan of CD8+ T cells have provided guidance for the design of more optimal anti-tumor immunotherapy regimens. Here, we review the newly discovered methods to enhance the function of CD8+ T cells against solid tumors, focusing on optimizing T cell receptor (TCR) expression, improving antigen recognition by engineered T cells, enhancing signal transduction of the TCR-CD3 complex, inducing the homing of polyclonal functional T cells to tumors, reversing T cell exhaustion under chronic antigen stimulation, and reprogramming the energy and metabolic pathways of T cells. We also discuss how to participate in the epigenetic changes of CD8+ T cells to regulate two key indicators of anti-tumor responses, namely effectiveness and persistence.

Protective effects of Ganoderma lucidum spores on estradiol benzoate-induced TEC apoptosis and compromised double-positive thymocyte development

Backgroud: Thymic atrophy marks the onset of immune aging, precipitating developmental anomalies in T cells. Numerous clinical and preclinical investigations have underscored the regulatory role of Ganoderma lucidum spores (GLS) in T cell development. However, the precise mechanisms underlying this regulation remain elusive. Methods: In this study, a mice model of estradiol benzoate (EB)-induced thymic atrophy was constructed, and the improvement effect of GLS on thymic atrophy was evaluated. Then, we employs multi-omics techniques to elucidate how GLS modulates T cell development amidst EB-induced thymic atrophy in mice. Results: GLS effectively mitigates EB-induced thymic damage by attenuating apoptotic thymic epithelial cells (TECs) and enhancing the output of CD4+ T cells into peripheral blood. During thymic T cell development, sporoderm-removed GLS (RGLS) promotes T cell receptor (TCR) α rearrangement by augmenting V-J fragment rearrangement frequency and efficiency. Notably, biased Vα14-Jα18 rearrangement fosters double-positive (DP) to invariant natural killer T (iNKT) cell differentiation, partially contingent on RGLS-mediated restriction of peptide-major histocompatibility complex I (pMHCⅠ)-CD8 interaction and augmented CD1d expression in DP thymocytes, thereby promoting DP to CD4+ iNKT cell development. Furthermore, RGLS amplifies interaction between a DP subpopulation, termed DPsel-7, and plasmacytoid dendritic cells (pDCs), likely facilitating the subsequent development of double-negative iNKT1 cells. Lastly, RGLS suppresses EB-induced upregulation of Abpob and Apoa4, curbing the clearance of CD4+Abpob+ and CD4+Apoa4+ T cells by mTECs, resulting in enhanced CD4+ T cell output. Discussion: These findings indicate that the RGLS effectively mitigates EB-induced TEC apoptosis and compromised double-positive thymocyte development. These insights into RGLS's immunoregulatory role pave the way for its potential as a T-cell regeneration inducer.

Inhibition of CD226 Co-Stimulation Suppresses Diabetes Development in the NOD Mouse by Augmenting Tregs and Diminishing Effector T Cell Function

Aims/hypothesis

Immunotherapeutics targeting T cells are crucial for inhibiting autoimmune disease progression proximal to disease onset in type 1 diabetes. A growing number of T cell-directed therapeutics have demonstrated partial therapeutic efficacy, with anti-CD3 (α-CD3) representing the only regulatory agency-approved drug capable of slowing disease progression through a mechanism involving the induction of partial T cell exhaustion. There is an outstanding need to augment the durability and effectiveness of T cell targeting by directly restraining proinflammatory T helper type 1 (Th1) and type 1 cytotoxic CD8+ T cell (Tc1) subsets, while simultaneously augmenting regulatory T cell (Treg) activity. Here, we present a novel strategy for reducing diabetes incidence in the NOD mouse model using a blocking monoclonal antibody targeting the type 1 diabetes-risk associated T cell co-stimulatory receptor, CD226.

Methods

Female NOD mice were treated with anti-CD226 between 7-8 weeks of age and then monitored for diabetes incidence and therapeutic mechanism of action.

Results

Compared to isotype-treated controls, anti-CD226 treated NOD mice showed reduced insulitis severity at 12 weeks and decreased disease incidence at 30 weeks. Flow cytometric analysis performed five weeks post-treatment demonstrated reduced proliferation of CD4+ and CD8+ effector memory T cells in spleens of anti-CD226 treated mice. Phenotyping of pancreatic Tregs revealed increased CD25 expression and STAT5 phosphorylation following anti-CD226, with splenic Tregs displaying augmented suppression of CD4+ T cell responders in vitro. Anti-CD226 treated mice exhibited reduced frequencies of islet-specific glucose-6-phosphatase catalytic subunit related protein (IGRP)-reactive CD8+ T cells in the pancreas, using both ex vivo tetramer staining and single-cell T cell receptor sequencing (scTCR-seq) approaches. 51Cr-release assays demonstrated reduced cell-mediated lysis of beta-cells by anti-CD226-treated autoreactive cytotoxic T lymphocytes.

Conclusions/interpretation

CD226 blockade reduces T cell cytotoxicity and improves Treg function, representing a targeted and rational approach for restoring immune regulation in type 1 diabetes.

CD226 promotes renal fibrosis by regulating macrophage activation and migration

It has been found that CD226 plays an important role in regulating macrophage function, but its expression and function in macrophages during renal fibrogenesis have not been studied. Our data demonstrated that CD226 expression in macrophages was obviously upregulated in the unilateral ureteral obstruction model, while CD226 deficiency attenuated collagen deposition in renal interstitium along with fewer M1 within renal cortex and renal medulla and a lower level of proinflammatory factors compared to that of control littermates. Further studies demonstrated that Cd226-/- bone marrow-derived macrophages transferring could significantly reduce the tubular injury, collagen deposition, and proinflammatory cytokine secretion compared with that of Cd226+/+ bone marrow-derived macrophages transferring in the unilateral ureteral obstruction model. Mechanistic investigations revealed that CD226 promoted proinflammatory M1 macrophage accumulation in the kidney via suppressing KLF4 expression in macrophages. Therefore, our results uncovered a pathogenic role of CD226 during the development of chronic kidney disease by promoting monocyte infiltration from peripheral blood into the kidney and enhancing macrophage activation toward the inflammatory phenotype by suppressing KLF4 expression.

CD112 is an epithelial-to-mesenchymal transition-related and immunological biomarker in pan-cancer

Background

The nectin adhesion molecule CD112, an important component of tumor progression, belongs to the nectin family. However, a comprehensive evaluation of its clinical relevance and mechanism in various cancers is yet to be conducted.

Methods

This investigation fully examined the relationship between prognosis and CD112 expression. We clarified the function of CD112 in tumor immunity by employing The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) databases. This involved examining its connections to tumor mutation burden (TMB), DNA methylation, tumor immune invasion, mismatch repair (MMR), microsatellite instability (MSI), and common immune checkpoint inhibitors (ICIs). Additionally, the impact of CD112 knockdown on cell function was examined in colorectal cancer (CRC) cell lines.

Results

In the current study, we found malignant tissues express high levels of CD112, which was related to TMB, MMR, MSI, and DNA methylation. Survival analysis indicated that patients with high CD112 expression had an unfavorable prognosis more frequently. In addition, CD112 expression was negatively associated with infiltration levels of CD4 positive (CD4+) T cells, CD8 positive (CD8+) T cells, and T cells. Western blotting and pathway enrichment analysis showed that CD112 is significantly linked to epithelial-to-mesenchymal transition (EMT). Additionally, CRC cells migrate and proliferate less when CD112 was knocked down. CD112 expression was found to be negatively associated with anti-programmed cell death protein 1 (PD-1) and anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) treatment outcomes in patients.

Conclusions

CD112 may act as a possible prognostic marker in immune therapy and may stimulate tumor growth by upregulating the EMT pathway.

Development of pharmacological immunoregulatory anti-cancer therapeutics: current mechanistic studies and clinical opportunities

Immunotherapy represented by anti-PD-(L)1 and anti-CTLA-4 inhibitors has revolutionized cancer treatment, but challenges related to resistance and toxicity still remain. Due to the advancement of immuno-oncology, an increasing number of novel immunoregulatory targets and mechanisms are being revealed, with relevant therapies promising to improve clinical immunotherapy in the foreseeable future. Therefore, comprehending the larger picture is important. In this review, we analyze and summarize the current landscape of preclinical and translational mechanistic research, drug development, and clinical trials that brought about next-generation pharmacological immunoregulatory anti-cancer agents and drug candidates beyond classical immune checkpoint inhibitors. Along with further clarification of cancer immunobiology and advances in antibody engineering, agents targeting additional inhibitory immune checkpoints, including LAG-3, TIM-3, TIGIT, CD47, and B7 family members are becoming an important part of cancer immunotherapy research and discovery, as are structurally and functionally optimized novel anti-PD-(L)1 and anti-CTLA-4 agents and agonists of co-stimulatory molecules of T cells. Exemplified by bispecific T cell engagers, newly emerging bi-specific and multi-specific antibodies targeting immunoregulatory molecules can provide considerable clinical benefits. Next-generation agents also include immune epigenetic drugs and cytokine-based therapeutics. Cell therapies, cancer vaccines, and oncolytic viruses are not covered in this review. This comprehensive review might aid in further development and the fastest possible clinical adoption of effective immuno-oncology modalities for the benefit of patients.

Increased levels of circulating soluble CD226 in multiple sclerosis

BACKGROUND

The glycoprotein CD226 plays a key role in regulating immune cell function. Soluble CD226 (sCD226) is increased in sera of patients with several chronic inflammatory diseases but its levels in neuroinflammatory diseases such as multiple sclerosis (MS) are unknown.

OBJECTIVE

To investigate the presence and functional implications of sCD226 in persons with multiple sclerosis (pwMS) and other neurological diseases.

METHODS

The mechanisms of sCD226 production were first investigated by analyzing CD226 surface expression levels and supernatants of CD3/CD226-coactivated T cells. The role of sCD226 on dendritic cell maturation was evaluated. The concentration of sCD226 in the sera from healthy donors (HD), pwMS, neuromyelitis optica (NMO), and Alzheimer's disease (AD) was measured.

RESULTS

CD3/CD226-costimulation induced CD226 shedding. Addition of sCD226 to dendritic cells during their maturation led to an increased production of the pro-inflammatory cytokine interleukin (IL)-23. We observed a significant increase in sCD226 in sera from pwMS and NMO compared to HD and AD. In MS, levels were increased in both relapsing-remitting multiple sclerosis (RRMS) and secondary-progressive multiple sclerosis (SPMS) compared to clinically isolated syndrome (CIS).

CONCLUSION

Our data suggest that T-cell activation leads to release of sCD226 that could promote inflammation and raises the possibility of using sCD226 as a biomarker for neuroinflammation.

Unleashing the power of immune checkpoints: Post-translational modification of novel molecules and clinical applications

Immune checkpoint molecules play a pivotal role in the initiation, regulation, and termination of immune responses. Tumor cells exploit these checkpoints to dampen immune cell function, facilitating immune evasion. Clinical interventions target this mechanism by obstructing the binding of immune checkpoints to their ligands, thereby restoring the anti-tumor capabilities of immune cells. Notably, therapies centered on immune checkpoint inhibitors, particularly PD-1/PD-L1 and CTLA-4 blocking antibodies, have demonstrated significant clinical promise. However, a considerable portion of patients still encounter suboptimal efficacy and develop resistance. Recent years have witnessed an exponential surge in preclinical and clinical trials investigating novel immune checkpoint molecules such as TIM3, LAG3, TIGIT, NKG2D, and CD47, along with their respective ligands. The processes governing immune checkpoint molecules, from their synthesis to transmembrane deployment, interaction with ligands, and eventual degradation, are intricately tied to post-translational modifications. These modifications encompass glycosylation, phosphorylation, ubiquitination, neddylation, SUMOylation, palmitoylation, and ectodomain shedding. This discussion proceeds to provide a concise overview of the structural characteristics of several novel immune checkpoints and their ligands. Additionally, it outlines the regulatory mechanisms governed by post-translational modifications, offering insights into their potential clinical applications in immune checkpoint blockade.

CD155 as an emerging target in tumor immunotherapy

CD155 is an immunoglobulin-like protein overexpressed in almost all the tumor cells, which not only promotes proliferation, adhesion, invasion, and migration of tumor cells, but also regulates immune responses by interacting with TIGIT, CD226 or CD96 receptors expressed on several immune cells, thereby modulating the functionality of these cellular subsets. As a novel immune checkpoint, the inhibition of CD155/TIGIT, either as a standalone treatment or in conjunction with other immune checkpoint inhibitors, has demonstrated efficacy in managing advanced solid malignancies. In this review, we summarize the intricate relationship between on tumor surface CD155 and its receptors, with further discussion on how they regulate the occurrence of tumor immune escape. In addition, novel therapeutic strategies and clinical trials targeting CD155 and its receptors are summarized, providing a strong rationale and way forward for the development of next-generation immunotherapies.

Genetic Variant of DNAM-1 rs763361 C>T Is Associated with Ankylosing Spondylitis in a Mexican Population

DNAM-1 (CD226) is an activating receptor expressed in CD8+ T cells, NK cells, and monocytes. It has been reported that two SNPs in the DNAM-1 gene, rs763361 C>T and rs727088 G>A, have been associated with different autoimmune diseases; however, the role of DNAM-1 in ankylosing spondylitis has been less studied. For this reason, we focused on the study of these two SNPs in association with ankylosing spondylitis. For this, 34 patients and 70 controls were analyzed using endpoint PCR with allele-specific primers. Our results suggest that rs763361 C>T is involved as a possible protective factor under the CT co-dominant model (OR = 0.34, 95% CI = 0.13-0.88, p = 0.022) and the CT + TT dominant model (OR = 0.39, 95% CI = 0.17-0.90, p = 0.025), while rs727088 G>A did not show an association with the disease in any of the inheritance models. When analyzing the relationships of the haplotypes, we found that the T + A haplotype (OR = 0.31, 95% CI = 0.13-0.73, p = 0.0083) is a protective factor for developing the disease. In conclusion, the CT and CT + TT variants of rs763361 C>T and the T + A haplotype were considered as protective factors for developing ankylosing spondylitis.

Structural basis of hepatitis B virus receptor binding

Hepatitis B virus (HBV), a leading cause of developing hepatocellular carcinoma affecting more than 290 million people worldwide, is an enveloped DNA virus specifically infecting hepatocytes. Myristoylated preS1 domain of the HBV large surface protein binds to the host receptor sodium-taurocholate cotransporting polypeptide (NTCP), a hepatocellular bile acid transporter, to initiate viral entry. Here, we report the cryogenic-electron microscopy structure of the myristoylated preS1 (residues 2-48) peptide bound to human NTCP. The unexpectedly folded N-terminal half of the peptide embeds deeply into the outward-facing tunnel of NTCP, whereas the C-terminal half formed extensive contacts on the extracellular surface. Our findings reveal an unprecedented induced-fit mechanism for establishing high-affinity virus-host attachment and provide a blueprint for the rational design of anti-HBV drugs targeting virus entry.

T cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domain as a promising immune checkpoint target for the treatment of SLE

Immune checkpoints (ICs) play a pivotal role in orchestrating immune regulation, crucial for the maintenance of immune tolerance and prevention of autoimmune diseases. One noteworthy example among these immune regulators is T cell immunoglobulin (Ig) and immunoreceptor tyrosine-based inhibitory motif (ITIM) domain (TIGIT). The TIGIT pathway's inhibition or the absence of TIGIT has been linked to the hyperactivation and excessive proliferation of T cells, rendering individuals more susceptible to autoimmune diseases and exacerbating inflammatory responses. Conversely, the activation of TIGIT has exhibited promising outcomes in ameliorating autoimmune disorders, as observed in murine models of systemic lupus erythematosus (SLE). Consequently, a judicious exploration of the co-inhibitory axis appears warranted for the effective management of pathogenic immune responses in SLE. In light of compelling evidence, this review undertakes a comprehensive examination of TIGIT's characteristics within the context of autoimmunity, offering insights into its potential as a therapeutic target for SLE.

Increased proportion of CD226 + CD14 + monocytes correlates with clinical features and laboratory parameters in patients with primary Sjögren's syndrome

OBJECTIVES

CD226 is widely expressed on the surface of immune cells as a co-stimulatory receptor, which is involved in the development of many autoimmune diseases. The purpose of this study was to investigate the proportion of CD226 on CD14 + monocytes in the peripheral circulation of patients with primary Sjögren's syndrome (pSS) and the clinical significance of pSS.

METHODS

The proportion of CD226 on the surface of CD14 + monocytes was measured by flow cytometry in 45 pSS patients and 25 healthy controls (HC). The correlations between the proportion of CD226 + CD14 + monocytes and the clinical features and laboratory parameters of pSS were analyzed. Meanwhile, we analyzed the change in proportion of CD226 + CD14 + monocytes before and after treatment, and the clinical significance of pSS was evaluated.

RESULTS

The proportion of CD226 on CD14 + monocytes markedly increased in pSS patients compared to HC (p < .01). We found the proportion of CD226 + CD14 + monocytes was positively correlated with the disease activity and severity of pSS patients. The proportion of CD226 + CD14 + monocytes in pSS patients with decayed tooth, fatigue, interstitial lung disease (ILD), low WBC, high IgG, anti-Ro60, and anti-SSB positive increased compared to that in negative patients (p < .05). Furthermore, the proportion of CD226 + CD14 + monocytes was significantly higher in active patients than in nonactive patients (p < .01). Additionally, the proportion of CD226 + CD14 + monocytes decreased in seven pSS patients after treatment (p < .01).

CONCLUSION

Our study suggested that an increased CD226 proportion on CD14 + monocytes was associated with the clinical manifestations, disease activity, and prognosis of pSS patients. CD226+ CD14 + monocytes may present a potential target and a biomarker for the prognosis and therapy of pSS patients.

CD226 maintains regulatory T cell phenotype stability and metabolism by the mTOR/Myc pathway under inflammatory conditions

Regulatory T (Treg) cells exhibit immunosuppressive phenotypes and particular metabolic patterns with certain degrees of plasticity. Previous studies of the effects of the co-stimulatory molecule CD226 on Treg cells are controversial. Here, we show that CD226 primarily maintains the Treg cell stability and metabolism phenotype under inflammatory conditions. Conditional deletion of CD226 within Foxp3+ cells exacerbates symptoms in murine graft versus host disease models. Treg cell-specific deletion of CD226 increases the Treg cell percentage in immune organs but weakens their immunosuppressive function with a T helper 1-like phenotype conversion under inflammation. CD226-deficient Treg cells exhibit reduced oxidative phosphorylation and increased glycolysis rates, which are regulated by the adenosine 5'-monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR)/myelocytomatosis oncogene (Myc) pathway, and inhibition of Myc signaling restores the impaired functions of CD226-deficient Treg cells in an inflammatory disease model of colitis. This study reveals an Myc-mediated CD226 regulation of Treg cell phenotypic stability and metabolism, providing potential therapeutic strategies for targeted interventions of Treg cell-specific CD226 in inflammatory diseases.

Dysregulation of DNAM-1-Mediated NK Cell Anti-Cancer Responses in the Tumor Microenvironment

NK cells play a pivotal role in anti-cancer immune responses, thanks to the expression of a wide array of inhibitory and activating receptors that regulate their cytotoxicity against transformed cells while preserving healthy cells from lysis. However, NK cells exhibit severe dysfunction in the tumor microenvironment, mainly due to the reduction of activating receptors and the induction or increased expression of inhibitory checkpoint receptors. An activating receptor that plays a central role in tumor recognition is the DNAM-1 receptor. It recognizes PVR and Nectin2 adhesion molecules, which are frequently overexpressed on the surface of cancerous cells. These ligands are also able to trigger inhibitory signals via immune checkpoint receptors that are upregulated in the tumor microenvironment and can counteract DNAM-1 activation. Among them, TIGIT has recently gained significant attention, since its targeting results in improved anti-tumor immune responses. This review aims to summarize how the recognition of PVR and Nectin2 by paired co-stimulatory/inhibitory receptors regulates NK cell-mediated clearance of transformed cells. Therapeutic approaches with the potential to reverse DNAM-1 dysfunction in the tumor microenvironment will be also discussed.

DNAM-1 Immunoreceptor Protects Mice from Concanavalin A-Induced Acute Liver Injury by Reducing Neutrophil Infiltration

DNAX accessory molecule-1 (DNAM-1; CD226) is an activating immunoreceptor on T cells and NK cells. The interaction of DNAM-1 with its ligand CD155 expressed on hematopoietic and nonhematopoietic cells plays an important role in innate and adaptive immune responses. In this study, we investigated the role of the DNAM-1-CD155 axis in the pathogenesis of T cell-mediated Con A-induced acute liver injury. Unexpectedly, DNAM-1-deficient (Cd226-/-) mice exhibited more severe acute liver injury and higher concentrations of IL-6 and TNF-α than did wild-type (WT) mice after Con A injection. We found that a larger number of neutrophils infiltrated into the liver of Cd226-/- mice compared with WT mice after Con A injection. Depletion of neutrophils ameliorated liver injury and decreased IL-6 and TNF-α in Cd226-/- mice after Con A injection, suggesting that neutrophils exacerbate the liver injury in Cd226-/- mice. Hepatocytes produced more significant amounts of CXCL1, a chemoattractant for neutrophils, in Cd226-/- mice than in WT mice after Con A injection. In the coculture of hepatocytes with liver lymphocytes, either DNAM-1 deficiency in liver lymphocytes or CD155 deficiency in hepatocytes promoted CXCL1 production by hepatocytes. These results suggest that the interaction of DNAM-1 with CD155 inhibits CXCL1 production by hepatocytes, leading to ameliorating acute liver injury.

Co-inhibition of TIGIT and PD-1/PD-L1 in Cancer Immunotherapy: Mechanisms and Clinical Trials

Over the past decade, immune checkpoint inhibitors (ICIs) have emerged as a revolutionary cancer treatment modality, offering long-lasting responses and survival benefits for a substantial number of cancer patients. However, the response rates to ICIs vary significantly among individuals and cancer types, with a notable proportion of patients exhibiting resistance or showing no response. Therefore, dual ICI combination therapy has been proposed as a potential strategy to address these challenges. One of the targets is TIGIT, an inhibitory receptor associated with T-cell exhaustion. TIGIT has diverse immunosuppressive effects on the cancer immunity cycle, including the inhibition of natural killer cell effector function, suppression of dendritic cell maturation, promotion of macrophage polarization to the M2 phenotype, and differentiation of T cells to regulatory T cells. Furthermore, TIGIT is linked with PD-1 expression, and it can synergize with PD-1/PD-L1 blockade to enhance tumor rejection. Preclinical studies have demonstrated the potential benefits of co-inhibition of TIGIT and PD-1/PD-L1 in enhancing anti-tumor immunity and improving treatment outcomes in several cancer types. Several clinical trials are underway to evaluate the safety and efficacy of TIGIT and PD-1/PD-L1 co-inhibition in various cancer types, and the results are awaited. This review provides an overview of the mechanisms of TIGIT and PD-1/PD-L1 co-inhibition in anti-tumor treatment, summarizes the latest clinical trials investigating this combination therapy, and discusses its prospects. Overall, co-inhibition of TIGIT and PD-1/PD-L1 represents a promising therapeutic approach for cancer treatment that has the potential to improve the outcomes of cancer patients treated with ICIs.

Nectin Family Ligands Trigger Immune Effector Functions in Health and Autoimmunity

The superfamily of immunoglobulin cell-adhesion molecules (IgCAMs) is a well-known family of cell-adhesion molecules used for immune-cell extravasation and cell-cell interaction. Amongst others, this family includes DNAX accessory molecule 1 (DNAM-1/CD226), class-I-restricted T-cell-associated molecule (CRTAM/CD355), T-cell-activated increased late expression (Tactile/CD96), T-cell immunoreceptor with Ig and ITIM domains (TIGIT), Nectins and Nectin-like molecules (Necls). Besides using these molecules to migrate towards inflammatory sites, their interactions within the immune system can support the immunological synapse with antigen-presenting cells or target cells for cytotoxicity, and trigger diverse effector functions. Although their role is generally described in oncoimmunity, this review emphasizes recent advances in the (dys)function of Nectin-family ligands in health, chronic inflammatory conditions and autoimmune diseases. In addition, this review provides a detailed overview on the expression pattern of Nectins and Necls and their ligands on different immune-cell types by focusing on human cell systems.

Extracellular CIRP Induces Novel Nectin-2+ (CD112+) Neutrophils to Promote Th1 Differentiation in Sepsis

Neutrophil heterogeneity represents different subtypes, states, phenotypes, and functionality of neutrophils implicated in sepsis pathobiology. Extracellular cold-inducible RNA-binding protein (eCIRP) is a damage-associated molecular pattern that promotes inflammation and alters neutrophil phenotype and function through TLR4. Nectin-2 or CD112 is an Ig-like superfamily member. CD112 serves as the ligand for DNAM-1 (CD226), which induces Th1 differentiation in naive CD4+ T cells. Th1 cells produce IFN-γ to fuel inflammation. CD112 is expressed mainly on APCs, but its expression in neutrophils is unknown. We hypothesize that eCIRP induces CD112 expression in neutrophils, promoting Th1 differentiation in sepsis. Incubation of neutrophils with recombinant murine (rm)CIRP significantly increased the gene and protein expression of CD112 in neutrophils. Anti-TLR4 Ab-treated neutrophils significantly decreased CD112+ neutrophils compared with controls upon rmCIRP stimulation. After 4 h of rmCIRP injection in mice, CD112+ neutrophils were significantly increased in the blood and spleen. At 20 h after cecal ligation and puncture-induced sepsis, CD112+ neutrophils were also significantly increased. Blood and splenic CD112+ neutrophils in septic CIRP-/- mice were much lower than in septic wild-type mice. Coculture of naive CD4 T cells with rmCIRP-treated (CD112+) neutrophils significantly increased IFN-γ-producing Th1 cells compared with coculture with PBS-treated neutrophils. CD112 Ab significantly attenuated Th1 differentiation induced by rmCIRP-treated neutrophils. Thus, eCIRP increases CD112 expression in neutrophils via TLR4 to promote Th1 differentiation in sepsis. Targeting eCIRP may attenuate sepsis by reducing Th1-promoting CD112+ neutrophils.

Receptors of immune cells mediates recognition for tumors

Over the last few decades, the immune system has been steered toward eradication of cancer cells with the help of cancer immunotherapy. T cells, B cells, monocytes/macrophages, dendritic cells, T-reg cells, and natural killer (NK) cells are some of the numerous immune cell types that play a significant part in cancer cell detection and reduction of inflammation, and the antitumor response. Briefly stated, chimeric antigen receptors, adoptive transfer and immune checkpoint modulators are currently the subjects of research focus for successful immunotherapy-based treatments for a variety of cancers. This chapter discusses ongoing investigations on the mechanisms and recent developments by which receptors of immune cells especially that of lymphocytes and monocytes/macrophages regulate the detection of immune system leading to malignancies. We will also be looking into the treatment strategies based on these mechanisms.

Advances in therapeutic targeting of immune checkpoints receptors within the CD96-TIGIT axis: clinical implications and future perspectives

INTRODUCTION

The development of therapeutic antibodies targeting immune checkpoint molecules (ICMs) that induce long-term remissions in cancer patients has revolutionized cancer immunotherapy. However, a major drawback is that relapse after an initial response may be attributed to innate and acquired resistance. Additionally, these treatments are not beneficial to all patients. Therefore, the discovery and targeting of novel ICMs and their combination with other immunotherapeutics are urgently needed.

AREAS COVERED

There has been increasing evidence of the CD96-TIGIT axis as ICMs in cancer immunotherapy in the last five years. This review will highlight and discuss the current knowledge about the role of CD96 and TIGIT in hematological and solid tumor immunotherapy in the context of empirical studies and clinical trials, and provide a comprehensive list of ongoing cancer clinical trials on the blockade of these ICMs, as well as the rationale behind combinational therapies with anti-PD-1/PD-L1 agents, chemotherapy drugs, and radiotherapy. Moreover, we share our perspectives on anti-CD96/TIGIT-related combination therapies.

EXPERT OPINION

CD96-TIGIT axis regulates anti-tumor immune responses. Thus, the receptors within this axis are the potential candidates for cancer immunotherapy. Combining the inhibition of CD96-TIGIT with anti-PD-1/PD-L1 mAbs and chemotherapy drugs has shown relatively effective results in the context of preclinical studies and tumor models.

Role of PARP Inhibitors in Cancer Immunotherapy: Potential Friends to Immune Activating Molecules and Foes to Immune Checkpoints

Poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) induce cytotoxic effects as single agents in tumors characterized by defective repair of DNA double-strand breaks deriving from BRCA1/2 mutations or other abnormalities in genes associated with homologous recombination. Preclinical studies have shown that PARPi-induced DNA damage may affect the tumor immune microenvironment and immune-mediated anti-tumor response through several mechanisms. In particular, increased DNA damage has been shown to induce the activation of type I interferon pathway and up-regulation of PD-L1 expression in cancer cells, which can both enhance sensitivity to Immune Checkpoint Inhibitors (ICIs). Despite the recent approval of ICIs for a number of advanced cancer types based on their ability to reinvigorate T-cell-mediated antitumor immune responses, a consistent percentage of treated patients fail to respond, strongly encouraging the identification of combination therapies to overcome resistance. In the present review, we analyzed both established and unexplored mechanisms that may be elicited by PARPi, supporting immune reactivation and their potential synergism with currently used ICIs. This analysis may indicate novel and possibly patient-specific immune features that might represent new pharmacological targets of PARPi, potentially leading to the identification of predictive biomarkers of response to their combination with ICIs.

A novel cuproptosis-related immune checkpoint gene signature identification and experimental validation in hepatocellular carcinoma

Copper-induced death, also termed cuproptosis, is a novel form of programmed cell death and is promising as a new strategy for cancer therapeutics. Elevated copper levels in tumor cells are positively associated with high PD-L1 expression. Nonetheless, the prognostic significance of cuproptosis-related immune checkpoint genes (CRICGs) in hepatocellular carcinoma remains to be further clarified. This study aimed to construct the prognostic CRICG signature to predict the immunotherapy response and outcomes of HCC patients. The co-expressed CRICGs were first screened through Pearson correlation analysis. Based on the least absolute shrinkage and selection operator-COX regression analyses, we identified a prognostic 5-CRICGs model, which closely correlates with poor outcomes, cancer development, and immune response to hepatocellular carcinoma. External validation was conducted using the GSE14520 dataset. Lastly, qRT-PCR was performed to determine the expression of the CRICGs in HCC. In summary, we developed and validated a novel prognostic CRICG model based on 5 CRICGs. This prognostic signature could effectively forecast the outcomes and immune response of HCC patients, which may serve as biomarkers for anticancer therapy.

G307S DNAM-1 Mutation Exacerbates Autoimmune Encephalomyelitis via Enhancing CD4+ T Cell Activation

Although rs763361, which causes a nonsynonymous glycine-to-serine mutation at residue 307 (G307S mutation) of the DNAX accessory molecule-1 (DNAM-1) immunoreceptor, is a single-nucleotide polymorphism associated with autoimmune disease susceptibility, little is known about how the single-nucleotide polymorphism is involved in pathogenesis. In this study, we established human CD4+ T cell transfectants stably expressing wild-type (WT) or G307S DNAM-1 and showed that the costimulatory signal from G307S DNAM-1 induced greater proinflammatory cytokine production and cell proliferation than that from wild-type DNAM-1. The G307S mutation also enhanced the recruitment of the tyrosine kinase Lck and augmented p-Tyr322 of DNAM-1. We also established a mouse myelin Ag-specific CD4+ T cell transfectant stably expressing the chimeric DNAM-1 (chDNAM-1) consisting of the extracellular, transmembrane, and a part of intracellular regions of mouse DNAM-1 (residues 1-285) fused with the part of the intracellular region (residues 286-336) of human WT or G307S chDNAM-1. Adoptive transfer of the mouse T cell transfectant expressing the G307S chDNAM-1 into mice exacerbated experimental autoimmune encephalomyelitis compared with the transfer of cells expressing the WT chDNAM-1. These findings suggest that rs763361 is a gain-of-function mutation that enhances DNAM-1-mediated costimulatory signaling for proinflammatory responses.

The immune synapses reveal aberrant functions of CD8 T cells during chronic HIV infection

Chronic HIV infection causes persistent low-grade inflammation that induces premature aging of the immune system including senescence of memory and effector CD8 T cells. To uncover the reasons of gradually diminished potency of CD8 T cells from people living with HIV, here we expose the T cells to planar lipid bilayers containing ligands for T-cell receptor and a T-cell integrins and analyze the cellular morphology, dynamics of synaptic interface formation and patterns of the cellular degranulation. We find a large fraction of phenotypically naive T cells from chronically infected people are capable to form mature synapse with focused degranulation, a signature of a differentiated T cells. Further, differentiation of aberrant naive T cells may lead to the development of anomalous effector T cells undermining their capacity to control HIV and other pathogens that could be contained otherwise.

CD226 Deficiency Alleviates Murine Allergic Rhinitis by Suppressing Group 2 Innate Lymphoid Cell Responses

Allergic rhinitis (AR) is an immunoglobulin E-mediated type 2 inflammation of the nasal mucosa that is mainly driven by type 2 helper T cells (Th2) and type 2 innate lymphoid cells (ILC2s). CD226 is a costimulatory molecule associated with inflammatory response and is mainly expressed on T cells, natural killer cells, and monocytes. This study is aimed at elucidating the role of CD226 in allergic inflammatory responses in murine AR using global and CD4+ T cell-specific Cd226 knockout (KO) mice. AR nasal symptoms were assessed based on the frequency of nose rubbing and sneezing. Hematoxylin and eosin and periodic acid–Schiff staining and quantitative real-time PCR methods were used to determine eosinophils, goblet cells, and ILC2-associated mRNA levels in the nasal tissues of mice. CD226 levels on ILC2s were detected using flow cytometry, and an immunofluorescence double staining assay was employed to determine the number of ILC2s in the nasal mucosa. The results showed that global Cd226 KO mice, but not CD4+ T cell-specific Cd226 KO mice, exhibited attenuated AR nasal symptoms. Eosinophil recruitment, goblet cell proliferation, and Th2-inflammatory cytokines were significantly reduced, which resulted in the alleviation of allergic and inflammatory responses. ILC2s in the murine nasal mucosa expressed higher levels of CD226 after ovalbumin stimulation, and CD226 deficiency led to a reduction in the proportion of nasal ILC2s and ILC2-related inflammatory gene expression. Hence, the effect of CD226 on the AR mouse model may involve the regulation of ILC2 function rather than CD4+ T cells.

Structural insights into the HBV receptor and bile acid transporter NTCP

Around 250 million people are infected with hepatitis B virus (HBV) worldwide¹, and 15 million may also carry the satellite virus hepatitis D virus (HDV), which confers even greater risk of severe liver disease². The HBV receptor has been identified as sodium taurocholate co-transporting polypeptide (NTCP), which interacts directly with the first 48 amino acid residues of the N-myristoylated N-terminal preS1 domain of the viral large protein³. Despite the pressing need for therapeutic agents to counter HBV, the structure of NTCP remains unsolved. This 349-residue protein is closely related to human apical sodium-dependent bile acid transporter (ASBT), another member of the solute carrier family SLC10. Crystal structures have been reported of similar bile acid transporters from bacteria^4,5, and these models are believed to resemble closely both NTCP and ASBT. Here we have used cryo-electron microscopy to solve the structure of NTCP bound to an antibody, clearly showing that the transporter has no equivalent of the first transmembrane helix found in other SLC10 proteins, and that the N terminus is exposed on the extracellular face. Comparison of our structure with those of related proteins indicates a common mechanism of bile acid transport, but the NTCP structure displays an additional pocket formed by residues that are known to interact with preS1, presenting new opportunities for structure-based drug design.

Cryo-electron structures of the hepatitis B virus receptor NTCP show a distinct membrane topology compared with other SLC10 proteins, but a common bile acid transport mechanism that is shared with related mammalian and bacterial proteins.

Functional Impact of Risk Gene Variants on the Autoimmune Responses in Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disease that develops in the interplay between genetic and environmental factors. A majority of individuals who develop T1D have a HLA make up, that accounts for 50% of the genetic risk of disease. Besides these HLA haplotypes and the insulin region that importantly contribute to the heritable component, genome-wide association studies have identified many polymorphisms in over 60 non-HLA gene regions that also contribute to T1D susceptibility.

Combining the risk genes in a score (T1D-GRS), significantly improved the prediction of disease progression in autoantibody positive individuals. Many of these minor-risk SNPs are associated with immune genes but how they influence the gene and protein expression and whether they cause functional changes on a cellular level remains a subject of investigation. A positive correlation between the genetic risk and the intensity of the peripheral autoimmune response was demonstrated both for HLA and non-HLA genetic risk variants. We also observed epigenetic and genetic modulation of several of these T1D susceptibility genes in dendritic cells (DCs) treated with vitamin D3 and dexamethasone to acquire tolerogenic properties as compared to immune activating DCs (mDC) illustrating the interaction between genes and environment that collectively determines risk for T1D. A notion that targeting such genes for therapeutic modulation could be compatible with correction of the impaired immune response, inspired us to review the current knowledge on the immune-related minor risk genes, their expression and function in immune cells, and how they may contribute to activation of autoreactive T cells, Treg function or β-cell apoptosis, thus contributing to development of the autoimmune disease.

The Effect of CD226 on the Balance between Inflammatory Monocytes and Small Peritoneal Macrophages in Mouse Ulcerative Colitis

Ulcerative colitis (UC) is a refractory and recurring inflammatory bowel disease (IBD). Monocytes and macrophages are major components of the mononuclear phagocyte system (MPS), and the balance between inflammatory monocytes and small peritoneal macrophages plays important roles in UC. However, the mechanisms governing the balance between inflammatory monocytes and small peritoneal macrophages in UC need to be clarified further. Here, we found that the expression levels of CD226 on different subsets of monocytes/macrophages are varied in UC mice. The expression levels of CD226 on patrolling monocytes (pMos) and small peritoneal macrophages (SPMs) were markedly increased, while the expression levels of CD226 on inflammatory monocytes (iMos) were decreased in UC mice. Significantly, the percentage of iMos was enhanced while the percentage of SPMs were decreased in CD226 knockout UC mice compared with that in wildtype UC mice. Moreover, CD226 deficiency suppressed the migration capacity of macrophages. Therefore, our data suggest that CD226 plays critical roles in regulating the function and balance of monocytes/macrophages in mouse UC and targeting CD226 in MPS may be developed as a potent therapy for UC.

Different subpopulations of regulatory T cells in human autoimmune disease, transplantation, and tumor immunity

CD4⁺CD25⁺ regulatory T cells (Tregs), a subpopulation of naturally CD4⁺ T cells that characteristically express transcription factor Forkhead box P3 (FOXP3), play a pivotal role in the maintenance of immune homeostasis and the prevention of autoimmunity. With the development of biological technology, the understanding of plasticity and stability of Tregs has been further developed. Recent studies have suggested that human Tregs are functionally and phenotypically diverse. The functions and mechanisms of different phenotypes of Tregs in different disease settings, such as tumor microenvironment, autoimmune diseases, and transplantation, have gradually become hot spots of immunology research that arouse extensive attention. Among the complex functions, CD4⁺CD25⁺FOXP3⁺ Tregs possess a potent immunosuppressive capacity and can produce various cytokines, such as IL‐2, IL‐10, and TGF‐β, to regulate immune homeostasis. They can alleviate the progression of diseases by resisting inflammatory immune responses, whereas promoting the poor prognosis of diseases by helping cells evade immune surveillance or suppressing effector T cells activity. Therefore, methods for targeting Tregs to regulate their functions in the immune microenvironment, such as depleting them to strengthen tumor immunity or expanding them to treat immunological diseases, need to be developed. Here, we discuss that different subpopulations of Tregs are essential for the development of immunotherapeutic strategies involving Tregs in human diseases.

TIGIT-CD226-PVR axis: advancing immune checkpoint blockade for cancer immunotherapy

Recent advances in understanding the roles of immune checkpoints in allowing tumors to circumvent the immune system have led to successful therapeutic strategies that have fundamentally changed oncology practice. Thus far, immunotherapies against only two checkpoint targets have been approved, CTLA-4 and PD-L1/PD-1. Antibody blockade of these targets enhances the function of antitumor T cells at least in part by relieving inhibition of the T cell costimulatory receptor CD28. These successes have stimulated considerable interest in identifying other pathways that may bte targeted alone or together with existing immunotherapies. One such immune checkpoint axis is comprised of members of the PVR/nectin family that includes the inhibitory receptor T cell immunoreceptor with Ig and immunoreceptor tyrosine-based inhibitory domains (TIGIT). Interestingly, TIGIT acts to regulate the activity of a second costimulatory receptor CD226 that works in parallel to CD28. There are currently over two dozen TIGIT-directed blocking antibodies in various phases of clinical development, testament to the promise of modulating this pathway to enhance antitumor immune responses. In this review, we discuss the role of TIGIT as a checkpoint inhibitor, its interplay with the activating counter-receptor CD226, and its status as the next advance in cancer immunotherapy.

Single-nucleotide polymorphisms as important risk factors of diabetes among Middle East population

Diabetes is a chronic metabolic disorder that leads to the dysfunction of various tissues and organs, including eyes, kidneys, and cardiovascular system. According to the World Health Organization, diabetes prevalence is 8.8% globally among whom about 90% of cases are type 2 diabetes. There are not any significant clinical manifestations in the primary stages of diabetes. Therefore, screening can be an efficient way to reduce the diabetic complications. Over the recent decades, the prevalence of diabetes has increased alarmingly among the Middle East population, which has imposed exorbitant costs on the health care system in this region. Given that the genetic changes are among the important risk factors associated with predisposing people to diabetes, we examined the role of single-nucleotide polymorphisms (SNPs) in the pathogenesis of diabetes among Middle East population. In the present review, we assessed the molecular pathology of diabetes in the Middle East population that paves the way for introducing an efficient SNP-based diagnostic panel for diabetes screening among the Middle East population. Since, the Middle East has a population of 370 million people; the current review can be a reliable model for the introduction of SNP-based diagnostic panels in other populations and countries around the world.

Horizontal mtDNA transfer between cells is common during mouse development

Cells transmit their genomes vertically to daughter cells during cell divisions. Here, we demonstrate the occurrence and extent of horizontal mitochondrial (mt)DNA acquisition between cells that are not in a parent-offspring relationship. Extensive single-cell sequencing from various tissues and organs of adult chimeric mice composed of cells carrying distinct mtDNA haplotypes showed that a substantial fraction of individual cardiomyocytes, neurons, glia, intestinal, and spleen cells captured donor mtDNA at high levels. In addition, chimeras composed of cells with wild-type and mutant mtDNA exhibited increased trafficking of wild-type mtDNA to mutant cells, suggesting that horizontal mtDNA transfer may be a compensatory mechanism to restore compromised mitochondrial function. These findings establish the groundwork for further investigations to identify mtDNA donor cells and mechanisms of transfer that could be critical to the development of novel gene therapies.

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Individual cells in adult mouse chimeras acquire donor mtDNA horizontally

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Significant percentage of cardiomyocytes, neurons, and glia were heteroplasmic

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Donor mtDNA heteroplasmy in these cells can reach up to 50%

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Pathogenic mtDNA mutations may potentiate horizontal acquisition of wild-type mtDNA

Mechanistic convergence of the TIGIT and PD-1 inhibitory pathways necessitates co-blockade to optimize anti-tumor CD8+ T cell responses

Dual blockade of the PD-1 and TIGIT coinhibitory receptors on T cells shows promising early results in cancer patients. Here, we studied the mechanisms whereby PD-1 and/or TIGIT blockade modulate anti-tumor CD8⁺ T cells. Although PD-1 and TIGIT are thought to regulate different costimulatory receptors (CD28 and CD226), effectiveness of PD-1 or TIGIT inhibition in preclinical tumor models was reduced in the absence of CD226. CD226 expression associated with clinical benefit in patients with non-small cell lung carcinoma (NSCLC) treated with anti-PD-L1 antibody atezolizumab. CD226 and CD28 were co-expressed on NSCLC infiltrating CD8⁺ T cells poised for expansion. Mechanistically, PD-1 inhibited phosphorylation of both CD226 and CD28 via its ITIM-containing intracellular domain (ICD); TIGIT's ICD was dispensable, with TIGIT restricting CD226 co-stimulation by blocking interaction with their common ligand PVR (CD155). Thus, full restoration of CD226 signaling, and optimal anti-tumor CD8⁺ T cell responses, requires blockade of TIGIT and PD-1, providing a mechanistic rationale for combinatorial targeting in the clinic.

Crosstalk between macrophages and natural killer cells in the tumor microenvironment

The tumor microenvironment (TME) is jointly constructed by a variety of cell types, including tumor cells, immune cells, fibroblasts, and epithelial cells, among others. The cells within the TME interact with each other and with tumor cells to influence tumor development and progression. As the most abundant immune cells in the TME, macrophages regulate the immune network by not only secreting a large amount of versatile cytokines but also expressing a series of ligands or receptors on the surface to interact with other cells directly. Due to their strong plasticity, they exert both immunostimulatory and immunosuppressive effects in the complex TME. The major effector cells of the immune system that directly target cancer cells include but are not limited to natural killer cells (NKs), dendritic cells (DCs), macrophages, polymorphonuclear leukocytes, mast cells, and cytotoxic T lymphocytes (CTLs). Among them, NK cells are the predominant innate lymphocyte subsets that mediate antitumor and antiviral responses. The activation and inhibition of NK cells are regulated by cytokines and the balance between activating and inhibitory receptors. There is an inextricable regulatory relationship between macrophages and NK cells. Herein, we systematically elaborate on the regulatory network between macrophages and NK cells through soluble mediator crosstalk and cell-to-cell interactions. We believe that a better understanding of the crosstalk between macrophages and NKs in the TME will benefit the development of novel macrophage- or NK cell-focused therapeutic strategies with superior efficacies in cancer therapy.

Nectin cell adhesion molecule-4 (NECTIN-4): A potential target for cancer therapy

NECTIN-4 [a poliovirus receptor-related-4 (pvrl-4) encoded protein] is a Ca2+ independent immunoglobulin-like protein. Along with other Nectins (Nectin-1, -2 and -3), it is primarily involved in cell-cell adhesion. In contrast to other Nectins, Nectin-4 is specifically enriched in the embryonic and placental tissues but its expression significantly declines in adult life. In recent years, it has been found that Nectin-4 is especially overexpressed and served as a tumor associated inducer in various malignant tumors including breast, lung, colorectal, pancreatic, ovarian cancers etc. Over-expression of Nectin-4 is associated with various aspects of tumor progression like proliferation, angiogenesis, epithelial to mesenchymal transition, metastasis, DNA repair, tumor relapse, poor prognosis in several types of cancer. This review systematically highlights the implications of Nectin-4 in every possible aspect of cancer and the molecular mechanism of Nectin-4 mediated cancer progression. We have further emphasized on the therapeutic strategies that are being proposed to specifically target Nectin-4.

Role of Nectin‑4 protein in cancer (Review)

The Nectin cell adhesion molecule (Nectin) family members are Ca2+‑independent immunoglobulin‑like cellular adhesion molecules (including Nectins 1‑4), involved in cell adhesion via homophilic/heterophilic interplay. In addition, the Nectin family plays a significant role in enhancing cellular viability and movement ability. In contrast to enrichment of Nectins 1‑3 in normal tissues, Nectin‑4 is particularly overexpressed in a number of tumor types, including breast, lung, urothelial, colorectal, pancreatic and ovarian cancer. Moreover, the upregulation of Nectin‑4 is an independent biomarker for overall survival in numerous cancer types. A large number of studies have revealed that high expression of Nectin‑4 is closely related to tumor occurrence and development in various cancer types, but the manner in which Nectin‑4 protein contributes to the onset and development of these malignancies is yet unknown. The present review summarizes the molecular mechanisms and functions of Nectin‑4 protein in the biological processes and current advances with regard to its expression and regulation in various cancer types.

Inverted CD8 T-Cell Exhaustion and Co-Stimulation Marker Balance Differentiate Aviremic HIV-2-Infected From Seronegative Individuals

HIV-2 is less pathogenic compared to HIV-1. Still, disease progression may develop in aviremic HIV-2 infection, but the driving forces and mechanisms behind such development are unclear. Here, we aimed to reveal the immunophenotypic pattern associated with CD8 T-cell pathology in HIV-2 infection, in relation to viremia and markers of disease progression. The relationships between pathological differences of the CD8 T-cell memory population and viremia were analyzed in blood samples obtained from an occupational cohort in Guinea-Bissau, including HIV-2 viremic and aviremic individuals. For comparison, samples from HIV-1- or dually HIV-1/2-infected and seronegative individuals were obtained from the same cohort. CD8 T-cell exhaustion was evaluated by the combined expression patterns of activation, stimulatory and inhibitory immune checkpoint markers analyzed using multicolor flow cytometry and advanced bioinformatics. Unsupervised multidimensional clustering analysis identified a cluster of late differentiated CD8 T-cells expressing activation (CD38+, HLA-DR^int/high), co-stimulatory (CD226+/-), and immune inhibitory (2B4+, PD-1^high, TIGIT^high) markers that distinguished aviremic from viremic HIV-2, and treated from untreated HIV-1-infected individuals. This CD8 T-cell population displayed close correlations to CD4%, viremia, and plasma levels of IP-10, sCD14 and beta-2 microglobulin in HIV-2 infection. Detailed analysis revealed that aviremic HIV-2-infected individuals had higher frequencies of exhausted TIGIT+ CD8 T-cell populations lacking CD226, while reduced percentage of stimulation-receptive TIGIT-CD226+ CD8 T-cells, compared to seronegative individuals. Our results suggest that HIV-2 infection, independent of viremia, skews CD8 T-cells towards exhaustion and reduced co-stimulation readiness. Further knowledge on CD8 T-cell phenotypes might provide help in therapy monitoring and identification of immunotherapy targets.

DNAM-1 versus TIGIT: competitive roles in tumor immunity and inflammatory responses

The co-stimulatory and co-inhibitory immunoreceptors DNAX accessory molecule-1 (DNAM-1) and T cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domains (TIGIT) are paired activating and inhibitory receptors on T cells and natural killer (NK) cells. They share the ligands poliovirus receptor (PVR, CD155) and its family member nectin-2 (CD112), which are highly expressed on antigen-presenting cells (APCs), tumors and virus-infected cells. Upon ligation with the ligands, DNAM-1 and TIGIT show reciprocal functions; whereas DNAM-1 promotes activation, proliferation, cytokine production and cytotoxic activity in effector lymphocytes, including CD4 + T-helper cells, CD8 + cytotoxic T lymphocytes and NK cells, TIGIT inhibits these DNAM-1 functions. On the other hand, DNAM-1 competes with TIGIT on regulatory T (Treg) cells in binding to CD155 and therefore regulates TIGIT signaling to down-regulate Treg cell function. Thus, whereas DNAM-1 enhances anti-tumor immunity and inflammatory responses by augmenting effector lymphocyte function and suppressing Treg cell function, TIGIT reciprocally suppresses these immune responses by suppressing effector lymphocyte function and augmenting Treg cell function. Thus, blockade of DNAM-1 and TIGIT function would be potential therapeutic approaches for patients with inflammatory diseases and those with cancers and virus infection, respectively.

DNAM-1 promotes inflammation-driven tumor development via enhancing IFN-γ production

DNAM-1 is an activating immunoreceptor on T cells and natural killer (NK) cells. Expression levels of its ligands, CD155 and CD112, are upregulated on tumor cells. The interaction of DNAM-1 on CD8 + T cells and NK cells with the ligands on tumor cells plays an important role in tumor immunity. We previously reported that mice deficient in DNAM-1 showed accelerated growth of tumors induced by the chemical carcinogen 7,12-dimethylbenz[a]anthracene (DMBA). Contrary to those results, we show here that tumor development induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) together with DMBA was suppressed in DNAM-1-deficient mice. In this model, DNAM-1 enhanced IFN-γ secretion from conventional CD4 + T cells to promote inflammation-related tumor development. These findings suggest that, under inflammatory conditions, DNAM-1 contributes to tumor development via conventional CD4 + T cells.

The CD112R/CD112 axis: a breakthrough in cancer immunotherapy

The recent discovery of immune checkpoint inhibitors is a significant milestone in cancer immunotherapy research. However, some patients with primary or adaptive drug resistance might not benefit from the overall therapeutic potential of immunotherapy in oncology. Thus, it is becoming increasingly critical for oncologists to explore the availability of new immune checkpoint inhibitors. An emerging co-inhibitory receptor, CD112R (also called PVRIG), is most commonly expressed on natural killer (NK) and T cells. It binds to its ligand (CD112 or PVRL2/nectin-2) and inhibits the strength with which T cells and NK cells respond to cancer. Therefore, CD112R is being presented as a new immune checkpoint inhibitor with high potential in cancer immunotherapy. CD112 is easily detectable on antigen-presenting or tumor cells, and its high level of expression has been linked with tumor progression and poor outcomes in most cancer patients. This review explores the molecular and functional relationship between CD112R, TIGIT, CD96, and CD226 in T cell responses. In addition, this review comprehensively discusses the recent developments of CD112R/CD112 immune checkpoints in cancer immunotherapy and prognosis.

TIGIT Can Exert Immunosuppressive Effects on CD8+ T Cells by the CD155/TIGIT Signaling Pathway for Hepatocellular Carcinoma In Vitro

Supplemental Digital Content is available in the text.

The efficacy of adoptive cellular immunotherapy against cancer cells is limited due to the presence of immunosuppressive cells within the solid tumor microenvironment. The upregulation of certain coinhibitory receptors may lead to exhaustion of the immune effector cells. T-cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domain (TIGIT) is an immune inhibitory receptor expressed by regulatory T cells and activated T cells and natural killer cells. The aim of this study was to determine the immunosuppressive effects of CD155/TIGIT signaling on CD8⁺ T cells of adoptive cellular immunotherapy in hepatocellular carcinoma (HCC). Our studies found that CD155 was overexpressed in HCC, and CD155^hi HCC cells upregulated TIGIT on CD8⁺ T cells, which decreased the secretion of interferon-γ, tumor necrosis factor-α, and interleukin-17A and increased that of interleukin-10 from the effector cells. However, TIGIT blockade or CD155-knockdown reversed the inhibitory effect of HCC cells on CD8⁺ T-cell effector function. These results indicate that TIGIT can exert an immunosuppressive effect on CD8 T cells by modulating cytokine production through CD155, and is a promising target to optimize adoptive cellular immunotherapy against HCC.

Poliovirus receptor (PVR)-like protein cosignaling network: new opportunities for cancer immunotherapy

Immune checkpoint molecules, also known as cosignaling molecules, are pivotal cell-surface molecules that control immune cell responses by either promoting (costimulatory molecules) or inhibiting (coinhibitory molecules) a signal. These molecules have been studied for many years. The application of immune checkpoint drugs in the clinic provides hope for cancer patients. Recently, the poliovirus receptor (PVR)-like protein cosignaling network, which involves several immune checkpoint receptors, i.e., DNAM-1 (DNAX accessory molecule-1, CD226), TIGIT (T-cell immunoglobulin (Ig) and immunoreceptor tyrosine-based inhibitory motif (ITIM)), CD96 (T cell activation, increased late expression (TACLILE)), and CD112R (PVRIG), which interact with their ligands CD155 (PVR/Necl-5), CD112 (PVRL2/nectin-2), CD111 (PVRL1/nectin-1), CD113 (PVRL3/nectin-3), and Nectin4, was discovered. As important components of the immune system, natural killer (NK) and T cells play a vital role in eliminating and killing foreign pathogens and abnormal cells in the body. Recently, increasing evidence has suggested that this novel cosignaling network axis costimulates and coinhibits NK and T cell activation to eliminate cancer cells after engaging with ligands, and this activity may be effectively targeted for cancer immunotherapy. In this article, we review recent advances in research on this novel cosignaling network. We also briefly outline the structure of this cosignaling network, the signaling cascades and mechanisms involved after receptors engage with ligands, and how this novel cosignaling network costimulates and coinhibits NK cell and T cell activation for cancer immunotherapy. Additionally, this review comprehensively summarizes the application of this new network in preclinical trials and clinical trials. This review provides a new immunotherapeutic strategy for cancer treatment.

Asynchronous blockade of PD-L1 and CD155 by polymeric nanoparticles inhibits triple-negative breast cancer progression and metastasis

PD-L1/PD-1 blockade therapy shows durable responses to triple-negative breast cancer (TNBC), but the response rate is low. CD155 promotes tumor metastasis intrinsically and modulates the immune response extrinsically as the ligand of DNAM-1 (costimulatory receptor) and TIGIT/CD96 (coinhibitory receptors). Herein, we verified that TNBC cells coexpressed PD-L1 and CD155. By examining the receptors of PD-L1 and CD155 on TNBC tumor-infiltrating lymphocytes (TILs) over time, we observed that PD-1 and DNAM-1 were upregulated early, whereas CD96 and TIGIT were upregulated late in CD8⁺ TILs. Based on these findings, we developed CD155 siRNA (siCD155)-loaded mPEG-PLGA-PLL (PEAL) nanoparticles (NPs) coated with PD-L1 blocking antibodies (P/PEAL_siCD155) to asynchronously block PD-L1 and CD155 in a spatiotemporal manner. P/PEAL_siCD155 maximized early-stage CD8⁺ T cell immune surveillance against 4T1 tumor, whereas reversed inhibition status of the late stage CD8⁺ T cells to prevent 4T1 tumor immune escape. In addition, the combination of P/PEAL_siCD155 and tumor-specific CD8 T cells induced immunogenic cell death (ICD) of 4T1 cells to further boost immune checkpoint therapy. Most importantly, P/PEAL_siCD155 displayed excellent TNBC targeting and induced CD8⁺ TILs-dominant intratumor antitumor immunity to efficiently inhibit TNBC progression and metastasis with excellent safety in a syngeneic 4T1 orthotopic TNBC tumor model.