VISTA is a checkpoint regulator for naïve T cell quiescence and peripheral tolerance

Biomarkers to predict the benefits of immune‑checkpoint blockade‑based therapy in patients with malignant peritoneal mesothelioma (Review)

Malignant peritoneal mesothelioma (MPeM) is a type of rare and highly lethal tumor. Immune checkpoint blockade (ICB)-based therapy has shown encouraging clinical activity for MPeM. However, no definitive biomarkers have been identified for predicting which patients with MPeM will benefit from ICB-based therapy. At present, there are several novel potential biomarkers proposed for predicting the response to ICB-based therapy, and biomarkers available in MPeM cells and in the tumor microenvironment have been identified with the potential to predict the efficacy of ICB-based therapy in MPeM. According to the molecular characteristics of MPeM itself, the feasibility of biomarkers in practice, and the body of available evidence, we hypothesize that the following five types of biomarkers can be used to predict the response of ICB-based therapy in patients with MPeM: Tertiary lymphoid structures, immune checkpoints and their ligands, fusion gene neoantigen burden, BRCA1-associated protein-1 haploinsufficiency and transcriptome-based biomarkers. The present review discusses the value and limitations of each type of biomarker, and potential solutions to address the limitations are proposed. The aim of the present review is to provide a background for future studies on ICB-based therapy for MPeM.

Graves disease: latest understanding of pathogenesis and treatment options

Graves disease is the most common cause of hyperthyroidism in iodine-sufficient areas. The main responsible mechanism is related to autoantibodies that bind and activate the thyrotropin receptor (TSHR). Although Graves hyperthyroidism is relatively common, no causal treatment options are available. Established treatment modalities are antithyroid drugs, which reduce thyroid hormone synthesis, radioactive iodine and surgery. However, emerging drugs that target the main autoantigen (monoclonal antibodies, small molecules, peptides) or block the immune pathway have been recently tested in clinical trials. Graves disease can involve the thyroid exclusively or it can be associated with extrathyroidal manifestations, among which Graves orbitopathy is the most common. The presence of Graves orbitopathy can change the management of the disease. An established treatment for moderate-to-severe Graves orbitopathy is intravenous glucocorticoids. However, recent advances in understanding the pathogenesis of Graves orbitopathy have allowed the development of new target-based therapies by blocking pro-inflammatory cytokine receptors, lymphocytic infiltration or the insulin-like growth factor 1 receptor (IGF1R), with several clinical trials providing promising results. This article reviews the new discoveries in the pathogenesis of Graves hyperthyroidism and Graves orbitopathy that offer several important tools in disease management.

VISTA-mediated immune evasion in cancer

Over the past decade, V-domain immunoglobulin suppressor of T-cell activation (VISTA) has been established as a negative immune checkpoint molecule. Since the role of VISTA in inhibiting T-cell activation was described, studies have demonstrated other diverse regulatory functions in multiple immune cell populations. Furthermore, its relevance has been identified in human cancers. The role of VISTA in cancer immune evasion has been determined, but its mechanisms in the tumor microenvironment remain to be further elucidated. Understanding its contributions to cancer initiation, progression, and resistance to current treatments will be critical to its utility as a target for novel immunotherapies. Here, we summarize the current understanding of VISTA biology in cancer.

Targeting of immune checkpoint regulator V-domain Ig suppressor of T-cell activation (VISTA) with 89Zr-labelled CI-8993

BACKGROUND

CI-8993 is a fully human IgG1κ monoclonal antibody (mAb) that binds specifically to immune checkpoint molecule VISTA (V-domain Ig suppressor of T-cell activation). Phase I safety has been established in patients with advanced cancer (NCT02671955). To determine the pharmacokinetics and biodistribution of CI-8993 in patients, we aimed to develop 89Zr-labelled CI-8993 and validate PET imaging and quantitation in preclinical models prior to a planned human bioimaging trial.

METHODS

CI-8993 and human isotype IgG1 control were conjugated to the metal ion chelator p-isothiocyanatobenzyl-desferrioxamine (Df). Quality of conjugates were assessed by SE-HPLC, SDS-PAGE, and FACS. After radiolabelling with zirconium-89 (89Zr), radioconjugates were assessed for radiochemical purity, immunoreactivity, antigen binding affinity, and serum stability in vitro. [89Zr]Zr-Df-CI-8993 alone (1 mg/kg, 4.6 MBq) or in combination with 30 mg/kg unlabelled CI-8993, as well as isotype control [89Zr]Zr-Df-IgG1 (1 mg/kg, 4.6 MBq) were assessed in human VISTA knock-in female (C57BL/6 N-Vsirtm1.1(VSIR)Geno, huVISTA KI) or control C57BL/6 mice bearing syngeneic MB49 bladder cancer tumours; and in BALB/c nu/nu mice bearing pancreatic Capan-2 tumours.

RESULTS

Stable constructs with an average chelator-to-antibody ratio of 1.81 were achieved. SDS-PAGE and SE-HPLC showed integrity of CI-8993 was maintained after conjugation; and ELISA indicated no impact of conjugation and radiolabelling on binding to human VISTA. PET imaging and biodistribution in MB49 tumour-bearing huVISTA KI female mice showed specific localisation of [89Zr]Zr-Df-CI-8993 to VISTA in spleen and tumour tissues expressing human VISTA. Specific tumour uptake was also demonstrated in Capan-2 xenografted BALB/c nu/nu mice.

CONCLUSIONS

We radiolabelled and validated [89Zr]Zr-Df-CI-8993 for specific binding to huVISTA in vivo. Our results demonstrate that 89Zr-labelled CI-8993 is now suitable for targeting and imaging VISTA expression in human trials.

Discovery of Benzo[d]oxazoles as Novel Dual Small-Molecule Inhibitors Targeting PD-1/PD-L1 and VISTA Pathway

The blockers of programmed cell death-1 (PD-1)/programmed cell death-ligand 1 (PD-L1) pathway have achieved great clinical success. However, the limited efficacy and low tumor response rate of anti-PD-1/PD-L1 monotherapy limit the clinical application of PD-1/PD-L1 inhibitors. V-domain immunoglobulin suppressor of T-cell activation (VISTA), a novel checkpoint regulator, exhibits potential synergy with PD-1/PD-L1 in enhancing antitumor immunity. Herein, we report the discovery of benzo[d]oxazole B3 as novel dual small-molecule inhibitors targeting PD-1/PD-L1 and VISTA with high PD-1/PD-L1 inhibitory activity and VISTA binding affinity. B3 rescues the immunosuppression of T-cells mediated by PD-L1 and VISTA and activates antitumor immunity effectively. Moreover, B3 could induce degradation of PD-L1 and VISTA in tumor cell. Furthermore, B3 displays significant in vivo antitumor efficacy in a CT26 mouse model. Our results discover B3 as a promising dual PD-1/PD-L1 and VISTA inhibitor, providing a novel therapeutic strategy to overcome the limitations of current anti-PD-1/PD-L1 therapy.

The pharmacogenomic and immune landscape of snoRNAs in human cancers

Small nucleolar RNAs (snoRNAs) are a class of non-coding RNAs primarily known for their role in the chemical modification of other RNAs. Recent studies suggested that snoRNAs may play a broader role in anti-cancer treatments such as targeted therapies and immunotherapies. Despite these insights, the comprehensive landscape of snoRNA associations with drug response and immunotherapy outcomes remains unexplored. In this study, we identified 79,448 and 75,185 associations between snoRNAs and drug response using data from VAEN and CancerRxTissue, respectively. Additionally, we discovered 29,199 associations between snoRNAs and immune checkpoint genes and 47,194 associations between snoRNAs and immune cell infiltrations. Sixteen snoRNAs were significantly correlated with immunotherapy objective response rate (ORR), and 92 snoRNAs showed significantly differential expression between cancers with high and low ORR. Furthermore, we identified 17 snoRNAs with significantly differential expression between cancer types with high and low immune-related adverse event (irAE) reporting odds ratio (ROR). Several snoRNAs, such as SNORD92, and SNORD83B, may represent promising biomarkers or therapeutic targets that needs further investigation. To facilitate further research, we developed a user-friendly portal, Pharmacogenomic and Immune Landscape of SnoRNA (PISNO, https://hanlaboratory.com/PISNO/), enabling researchers to visualize, browse, and download multi-dimensional data. This study highlights the potential of snoRNAs as biomarkers or therapeutic targets, paving the way for more effective and personalized anti-cancer treatments.

Activation-Induced Marker Assay to Identify and Isolate HCV-Specific T Cells for Single-Cell RNA-Seq Analysis

Identification and isolation of antigen-specific T cells for downstream transcriptomic analysis is key for various immunological studies. Traditional methods using major histocompatibility complex (MHC) multimers are limited by the number of predefined immunodominant epitopes and MHC matching of the study subjects. Activation-induced markers (AIM) enable highly sensitive detection of rare antigen-specific T cells irrespective of the availability of MHC multimers. Herein, we have developed an AIM assay for the detection, sorting and subsequent single-cell RNA sequencing (scRNA-seq) analysis of hepatitis C virus (HCV)-specific T cells. We examined different combinations of the activation markers CD69, CD40L, OX40, and 4-1BB at 6, 9, 18 and 24 h post stimulation with HCV peptide pools. AIM+ CD4 T cells exhibited upregulation of CD69 and CD40L as early as 6 h post-stimulation, while OX40 and 4-1BB expression was delayed until 18 h. AIM+ CD8 T cells were characterized by the coexpression of CD69 and 4-1BB at 18 h, while the expression of CD40L and OX40 remained low throughout the stimulation period. AIM+ CD4 and CD8 T cells were successfully sorted and processed for scRNA-seq analysis examining gene expression and T cell receptor (TCR) usage. scRNA-seq analysis from this one subject revealed that AIM+ CD4 T (CD69+ CD40L+) cells predominantly represented Tfh, Th1, and Th17 profiles, whereas AIM+ CD8 T (CD69+ 4-1BB+) cells primarily exhibited effector and effector memory profiles. TCR analysis identified 1023 and 160 unique clonotypes within AIM+ CD4 and CD8 T cells, respectively. In conclusion, this approach offers highly sensitive detection of HCV-specific T cells that can be applied for cohort studies, thus facilitating the identification of specific gene signatures associated with infection outcome and vaccination.

Small-Molecule Radiotracers for Visualization of V-Domain Immunoglobulin Suppressor of T Cell Activation

V-domain immunoglobulin suppressor of T cell activation (VISTA) plays a critical role in regulating innate and adaptive immune responses within the tumor immune microenvironment. Quantifying VISTA expression is necessary to determine whether patients respond to a related combination immunotherapy. This study developed two 68Ga-labeled small-molecule probes ([68Ga]Ga-DCA and [68Ga]Ga-DNCA) for visualizing and differentiating VISTA expression. These probes exhibited excellent targeting capabilities for multiple tumor types (including B16-F10, 4T1, MC38, and CT26 tumors), consistent with the levels of VISTA expression determined by immunoblotting. Co-injection of inhibitor CA-170 led to decreased tumor uptake of both [68Ga]Ga-DCA and [68Ga]Ga-DNCA. [68Ga]Ga-DCA was used to verify the feasibility of monitoring VISTA expression in lung metastasis models. In summary, this study describes the use of 68Ga-labeled CA-170 analogues as small-molecule probes for imaging VISTA. This could provide a visual method and enable personalized immunotherapy in patients.

Precursor central memory versus effector cell fate and naïve CD4+ T cell heterogeneity

Upon antigenic stimulation, naïve CD4+ T cells can give rise to phenotypically distinct effector T helper cells and long-lived memory T cells. We computationally reconstructed the in vivo trajectory of CD4+ T cell differentiation during a type I inflammatory immune response and identified two distinct differentiation paths for effector and precursor central memory T cells arising directly from naïve CD4+ T cells. Unexpectedly, our studies revealed heterogeneity among naïve CD4+ T cells, which are typically considered homogeneous save for their diverse T cell receptor usage. Specifically, a previously unappreciated population of naïve CD4+ T cells sensing environmental type I IFN exhibited distinct activation thresholds, suggesting that naïve CD4+ T cell differentiation potential may be influenced by environmental cues. This population was expanded in human viral infection and type I IFN response-lined autoimmunity. Understanding the relevance of naïve T cell heterogeneity to beneficial and maladaptive T cell responses may have therapeutic implications for adoptive T cell therapies in cancer immunotherapy and vaccination.

Eliminating a barrier: Aiming at VISTA, reversing MDSC-mediated T cell suppression in the tumor microenvironment

Immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment by producing remarkable clinical outcomes for patients with various cancer types. However, only a subset of patients benefits from immunotherapeutic interventions due to the primary and acquired resistance to ICIs. Myeloid-derived suppressor cells (MDSCs) play a crucial role in creating an immunosuppressive tumor microenvironment (TME) and contribute to resistance to immunotherapy. V-domain Ig suppressor of T cell activation (VISTA), a negative immune checkpoint protein highly expressed on MDSCs, presents a promising target for overcoming resistance to current ICIs. This article provides an overview of the evidence supporting VISTA's role in regulating MDSCs in shaping the TME, thus offering insights into how to overcome immunotherapy resistance.

VISTA: A promising target for overcoming immune evasion in gynecologic cancers

Immune checkpoint blockade (ICB) therapy has revolutionized cancer treatment but has shown limited efficacy in gynecologic cancers. VISTA (V-domain Ig suppressor of T-cell activation), a member of the B7 family, is emerging as another checkpoint that regulates the anti-tumor immune responses within the tumor microenvironment. This paper reviews the structure, expression, and mechanism of action of VISTA. Furthermore, it highlights recent advances in VISTA-blocking therapies and their potential in improving outcomes for patients with gynecologic cancers. By understanding the role of VISTA in mediating the immune evasion of gynecologic tumors, we can develop more effective combinatory treatment strategies that could overcome resistance to current ICB therapies.

Immune checkpoint inhibitors in infectious disease

Following success in cancer immunotherapy, immune checkpoint blockade is emerging as an exciting potential treatment for some infectious diseases, specifically two chronic viral infections, HIV and hepatitis B. Here, we will discuss the function of immune checkpoints, their role in infectious disease pathology, and the ability of immune checkpoint blockade to reinvigorate the immune response. We focus on blockade of programmed cell death 1 (PD-1) to induce durable immune-mediated control of HIV, given that anti-PD-1 can restore function to exhausted HIV-specific T cells and also reverse HIV latency, a long-lived form of viral infection. We highlight several key studies and future directions of research in relation to anti-PD-1 and HIV persistence from our group, including the impact of immune checkpoint blockade on the establishment (AIDS, 2018, 32, 1491), maintenance (PLoS Pathog, 2016, 12, e1005761; J Infect Dis, 2017, 215, 911; Cell Rep Med, 2022, 3, 100766) and reversal of HIV latency (Nat Commun, 2019, 10, 814; J Immunol, 2020, 204, 1242), enhancement of HIV-specific T cell function (J Immunol, 2022, 208, 54; iScience, 2023, 26, 108165), and investigating the effects of anti-PD-1 and anti-CTLA-4 in vivo in people with HIV on ART with cancer (Sci Transl Med, 2022, 14, eabl3836; AIDS, 2021, 35, 1631; Clin Infect Dis, 2021, 73, e1973). Our future work will focus on the impact of anti-PD-1 in vivo in people with HIV on ART without cancer and potential combinations of anti-PD-1 with other interventions, including therapeutic vaccines or antibodies and less toxic immune checkpoint blockers.

Life history of a brain autoreactive T cell: From thymus through intestine to blood-brain barrier and brain lesion

Brain antigen-specific autoreactive T cells seem to play a key role in inducing inflammation in the central nervous system (CNS), a characteristic feature of human multiple sclerosis (MS). These T cells are generated within the thymus, where they escape negative selection and become integrated into the peripheral immune repertoire of immune cells. Typically, these autoreactive T cells rest in the periphery without attacking the CNS. When autoimmune T cells enter gut-associated lymphatic tissue (GALT), they may be stimulated by the microbiota and its metabolites. After activation, the cells migrate into the CNS through the blood‒brain barrier, become reactivated upon interacting with local antigen-presenting cells, and induce inflammatory lesions within the brain parenchyma. This review describes how microbiota influence autoreactive T cells during their life, starting in the thymus, migrating through the periphery and inducing inflammation in their target organ, the CNS.

Advances in immunotherapy for breast cancer and feline mammary carcinoma: From molecular basis to novel therapeutic targets

The role of inflammation in cancer is a topic that has been investigated for many years. As established, inflammation emerges as a defining characteristic of cancer, presenting itself as a compelling target for therapeutic interventions in the realm of oncology. Controlling the tumor microenvironment (TME) has gained paramount significance, modifying not only the effectiveness of immunotherapy but also modulating the outcomes and prognoses of standard chemotherapy and other anticancer treatments. Immunotherapy has surfaced as a central focus within the domain of tumor treatments, using immune checkpoint inhibitors as cancer therapy. Immune checkpoints and their influence on the tumor microenvironment dynamic are presently under investigation, aiming to ascertain their viability as therapeutic interventions across several cancer types. Cancer presents a significant challenge in humans and cats, where female breast cancer ranks as the most prevalent malignancy and feline mammary carcinoma stands as the third most frequent. This review seeks to summarize the data about the immune checkpoints cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), lymphocyte activation gene-3 (LAG-3), programmed cell death protein-1 (PD-1), V-domain Ig suppressor of T cell activation (VISTA), and T-cell immunoglobulin and mucin domain 3 (TIM-3) respective ongoing investigations as prospective targets for therapy for human breast cancer, while also outlining findings from studies reported on feline mammary carcinoma (FMC), strengthening the rationale for employing FMC as a representative model in the exploration of human breast cancer.

The amalgam of naive CD4+ T cell transcriptional states is reconfigured by helminth infection to dampen the amplitude of the immune response

Naive CD4+ T cells in specific pathogen-free (SPF) mice are characterized by transcriptional heterogeneity and subpopulations distinguished by the expression of quiescence, the extracellular matrix (ECM) and cytoskeleton, type I interferon (IFN-I) response, memory-like, and T cell receptor (TCR) activation genes. We demonstrate that this constitutive heterogeneity, including the presence of the IFN-I response cluster, is commensal independent insofar as being identical in germ-free and SPF mice. By contrast, Nippostrongylus brasiliensis infection altered this constitutive heterogeneity. Naive T cell-intrinsic transcriptional changes acquired during helminth infection correlated with and accounted for decreased immunization response to an unrelated antigen. These compositional and functional changes were dependent variables of helminth infection, as they disappeared at the established time point of its clearance in mice. Collectively, our results indicate that the naive T cell pool is subject to dynamic transcriptional changes in response to certain environmental cues, which in turn permutes the magnitude of the immune response.

Wriggly woes: Helminths stirring up T cell trouble

Understanding determinants of immune response variation is central to developing treatment options. Even et al. show that naive CD4+ T cell transcriptional heterogeneity is altered by helminth infection leading to impaired immune responses independent of commensals.

Single-cell RNA-Seq analysis reveals cell subsets and gene signatures associated with rheumatoid arthritis disease activity

Rheumatoid arthritis (RA) management leans toward achieving remission or low disease activity. In this study, we conducted single-cell RNA sequencing (scRNA-Seq) of peripheral blood mononuclear cells (PBMCs) from 36 individuals (18 patients with RA and 18 matched controls, accounting for age, sex, race, and ethnicity), to identify disease-relevant cell subsets and cell type-specific signatures associated with disease activity. Our analysis revealed 18 distinct PBMC subsets, including an IFN-induced transmembrane 3-overexpressing (IFITM3-overexpressing) IFN-activated monocyte subset. We observed an increase in CD4+ T effector memory cells in patients with moderate-high disease activity (DAS28-CRP ≥ 3.2) and a decrease in nonclassical monocytes in patients with low disease activity or remission (DAS28-CRP < 3.2). Pseudobulk analysis by cell type identified 168 differentially expressed genes between RA and matched controls, with a downregulation of proinflammatory genes in the γδ T cell subset, alteration of genes associated with RA predisposition in the IFN-activated subset, and nonclassical monocytes. Additionally, we identified a gene signature associated with moderate-high disease activity, characterized by upregulation of proinflammatory genes such as TNF, JUN, EGR1, IFIT2, MAFB, and G0S2 and downregulation of genes including HLA-DQB1, HLA-DRB5, and TNFSF13B. Notably, cell-cell communication analysis revealed an upregulation of signaling pathways, including VISTA, in both moderate-high and remission-low disease activity contexts. Our findings provide valuable insights into the systemic cellular and molecular mechanisms underlying RA disease activity.

Sequential immunotherapy: towards cures for autoimmunity

Despite major progress in the treatment of autoimmune diseases in the past two decades, most therapies do not cure disease and can be associated with increased risk of infection through broad suppression of the immune system. However, advances in understanding the causes of autoimmune disease and clinical data from novel therapeutic modalities such as chimeric antigen receptor T cell therapies provide evidence that it may be possible to re-establish immune homeostasis and, potentially, prolong remission or even cure autoimmune diseases. Here, we propose a 'sequential immunotherapy' framework for immune system modulation to help achieve this ambitious goal. This framework encompasses three steps: controlling inflammation; resetting the immune system through elimination of pathogenic immune memory cells; and promoting and maintaining immune homeostasis via immune regulatory agents and tissue repair. We discuss existing drugs and those in development for each of the three steps. We also highlight the importance of causal human biology in identifying and prioritizing novel immunotherapeutic strategies as well as informing their application in specific patient subsets, enabling precision medicine approaches that have the potential to transform clinical care.

Expression of VISTA regulated via IFN-γ governs endogenous T-cell function and exhibits correlation with the efficacy of CD19 CAR-T cell treated B-malignant mice

BACKGROUND

Despite continuous improvements in the new target and construction of chimeric antigen receptor (CAR)-T, relapse remains a significant challenge following CAR-T therapy. Tumor microenvironment (TME) strongly correlates with the efficacy of CAR-T therapy. V-domain Ig suppressor of T-cell activation (VISTA), which exerts a multifaceted and controversial role in regulating the TME, acts not only as a ligand on antigen-presenting cells but also functions as a receptor on T cells. However, the characteristics and underlying mechanisms governing endogenous T-cell activation by VISTA, which are pivotal for reshaping the TME, remain incompletely elucidated.

METHODS

The immunocompetent B acute lymphoblastic leukemia (B-ALL), lymphoma, and melanoma murine models were employed to investigate the characteristics of endogenous T cells within the TME following CD19 and hCAIX CAR-T cell therapy, respectively. Furthermore, we examined the role of VISTA controlled by interferon (IFN)-γ signaling in regulating endogenous T-cell activation and functionality in B-ALL mice.

RESULTS

We demonstrated that the administration of CD19 CAR-T or hCAIX CAR-T cell therapy elicited augmented immune responses of endogenous T cells within the TME of B-ALL, lymphoma, and melanoma mice, thereby substantiating the efficacy of CAR-T cell efficacy. However, in the TME lacking IFN-γ signaling, VISTA levels remained elevated, resulting in attenuated cytotoxicity of endogenous T cells and reduced B-ALL recipient survival. Mice treated with CD19 CAR-T cells exhibited increased proportions of endogenous memory T cells during prolonged remission, which possessed the tumor-responsive capabilities to protect against B-ALL re-challenge. Compared with wild-type (WT) CAR-T treated mice, the administration of IFN-γ-/- CAR-T to both WT and IFN-γ-/- recipients resulted in a reduction in the numbers of endogenous CD4+ and CD8+ effectors, while exhibiting increased populations of naïve-like CD4+ T and memory CD8+ T cells. VISTA expression consistently remained elevated in resting or memory CD4+ T cells, with distinct localization from programmed cell death protein-1 (PD-1) expressing T subsets. Blocking the VISTA signal enhanced dendritic cell-induced proliferation and cytokine production by syngeneic T cells.

CONCLUSION

Our findings confirm that endogenous T-cell activation and functionality are regulated by VISTA, which is associated with the therapeutic efficiency of CAR-T and provides a promising therapeutic strategy for relapse cases in CAR-T therapy.

VISTA Deficiency Exacerbates the Development of Pulmonary Fibrosis by Promoting Th17 Differentiation

Background

Interstitial lung disease (ILD), characterized by pulmonary fibrosis (PF), represents the end-stage of various ILDs. The immune system plays an important role in the pathogenesis of PF. V-domain immunoglobulin suppressor of T-cell activation (VISTA) is an immune checkpoint with immune suppressive functions. However, its specific role in the development of PF and the underlying mechanisms remain to be elucidated.

Methods

We assessed the expression of VISTA in CD4 T cells from patients with connective tissue disease-related interstitial lung disease (CTD-ILD). Spleen cells from wild-type (WT) or Vsir -/- mice were isolated and induced for cell differentiation in vitro. Additionally, primary lung fibroblasts were isolated and treated with interleukin-17A (IL-17A). Mice were challenged with bleomycin (BLM) following VISTA blockade or Vsir knockout. Moreover, WT or Vsir -/- CD4 T cells were transferred into Rag1 -/- mice, which were then challenged with BLM.

Results

VISTA expression was decreased in CD4 T cells from patients with CTD-ILD. Vsir deficiency augmented T-helper 17 (Th17) cell differentiation in vitro. Furthermore, IL-17A enhanced the production of inflammatory cytokines, as well as the differentiation and migration of lung fibroblasts. Both VISTA blockade and knockout of Vsir increased the percentage of IL-17A-producing Th17 cells and promoted BLM-induced PF. In addition, mice receiving Vsir -/- CD4 T cells exhibited a higher percentage of Th17 cells and more severe PF compared to those receiving WT CD4 T cells.

Conclusion

These findings demonstrate the significant role of VISTA in modulating the development of PF by controlling Th17 cell differentiation. These insights suggest that targeting VISTA could be a promising therapeutic strategy for PF.

Current and future immunotherapeutic approaches in pancreatic cancer treatment

Pancreatic cancer is a major cause of cancer-related death, but despondently, the outlook and prognosis for this resistant type of tumor have remained grim for a long time. Currently, it is extremely challenging to prevent or detect it early enough for effective treatment because patients rarely exhibit symptoms and there are no reliable indicators for detection. Most patients have advanced or spreading cancer that is difficult to treat, and treatments like chemotherapy and radiotherapy can only slightly prolong their life by a few months. Immunotherapy has revolutionized the treatment of pancreatic cancer, yet its effectiveness is limited by the tumor's immunosuppressive and hard-to-reach microenvironment. First, this article explains the immunosuppressive microenvironment of pancreatic cancer and highlights a wide range of immunotherapy options, including therapies involving oncolytic viruses, modified T cells (T-cell receptor [TCR]-engineered and chimeric antigen receptor [CAR] T-cell therapy), CAR natural killer cell therapy, cytokine-induced killer cells, immune checkpoint inhibitors, immunomodulators, cancer vaccines, and strategies targeting myeloid cells in the context of contemporary knowledge and future trends. Lastly, it discusses the main challenges ahead of pancreatic cancer immunotherapy.

Redundancy and absurd names in immunology

In this short review, examples of unnecessary multiple names of cell membrane molecules, for example, immune checkpoints and cytokines, are presented. Moreover, ridiculous or inaccurate names, such as 'Regulated on activation, normal T-cell expressed and secreted' and 'tissue factor', are discussed.

The war between the immune system and the tumor - using immune biomarkers as tracers

Nowadays, immunotherapy is one of the most promising anti-tumor therapeutic strategy. Specifically, immune-related targets can be used to predict the efficacy and side effects of immunotherapy and monitor the tumor immune response. In the past few decades, increasing numbers of novel immune biomarkers have been found to participate in certain links of the tumor immunity to contribute to the formation of immunosuppression and have entered clinical trials. Here, we systematically reviewed the oncogenesis and progression of cancer in the view of anti-tumor immunity, particularly in terms of tumor antigen expression (related to tumor immunogenicity) and tumor innate immunity to complement the cancer-immune cycle. From the perspective of integrated management of chronic cancer, we also appraised emerging factors affecting tumor immunity (including metabolic, microbial, and exercise-related markers). We finally summarized the clinical studies and applications based on immune biomarkers. Overall, immune biomarkers participate in promoting the development of more precise and individualized immunotherapy by predicting, monitoring, and regulating tumor immune response. Therefore, targeting immune biomarkers may lead to the development of innovative clinical applications.

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.

LRIG1 engages ligand VISTA and impairs tumor-specific CD8+ T cell responses

Immune checkpoint blockade is a promising approach to activate antitumor immunity and improve the survival of patients with cancer. V-domain immunoglobulin suppressor of T cell activation (VISTA) is an immune checkpoint target; however, the downstream signaling mechanisms are elusive. Here, we identify leucine-rich repeats and immunoglobulin-like domains 1 (LRIG1) as a VISTA binding partner, which acts as an inhibitory receptor by engaging VISTA and suppressing T cell receptor signaling pathways. Mice with T cell-specific LRIG1 deletion developed superior antitumor responses because of expansion of tumor-specific cytotoxic T lymphocytes (CTLs) with increased effector function and survival. Sustained tumor control was associated with a reduction of quiescent CTLs (TCF1+ CD62Lhi PD-1low) and a reciprocal increase in progenitor and memory-like CTLs (TCF1+ PD-1+). In patients with melanoma, elevated LRIG1 expression on tumor-infiltrating CD8+ CTLs correlated with resistance to immunotherapies. These results delineate the role of LRIG1 as an inhibitory immune checkpoint receptor and propose a rationale for targeting the VISTA/LRIG1 axis for cancer immunotherapy.

The role of quiescent thymic progenitors in TAL/LMO2-induced T-ALL chemotolerance

Relapse in T-cell acute lymphoblastic leukemia (T-ALL) may signify the persistence of leukemia-initiating cells (L-ICs). Ectopic TAL1/LMO expression defines the largest subset of T-ALL, but its role in leukemic transformation and its impact on relapse-driving L-ICs remain poorly understood. In TAL1/LMO mouse models, double negative-3 (DN3; CD4-CD8-CD25+CD44-) thymic progenitors harbored L-ICs. However, only a subset of DN3 leukemic cells exhibited L-IC activity, and studies linking L-ICs and chemotolerance are needed. To investigate L-IC heterogeneity, we used mouse models and applied single-cell RNA-sequencing and nucleosome labeling techniques in vivo. We identified a DN3 subpopulation with a cell cycle-restricted profile and heightened TAL1/LMO2 activity, that expressed genes associated with stemness and quiescence. This dormant DN3 subset progressively expanded throughout leukemogenesis, displaying intrinsic chemotolerance and enrichment in genes linked to minimal residual disease. Examination of TAL/LMO patient samples revealed a similar pattern in CD7+CD1a- thymic progenitors, previously recognized for their L-IC activity, demonstrating cell cycle restriction and chemotolerance. Our findings substantiate the emergence of dormant, chemotolerant L-ICs during leukemogenesis, and demonstrate that Tal1 and Lmo2 cooperate to promote DN3 quiescence during the transformation process. This study provides a deeper understanding of TAL1/LMO-induced T-ALL and its clinical implications in therapy failure.

Therapeutic induction of antigen-specific immune tolerance

The development of therapeutic approaches for the induction of robust, long-lasting and antigen-specific immune tolerance remains an important unmet clinical need for the management of autoimmunity, allergy, organ transplantation and gene therapy. Recent breakthroughs in our understanding of immune tolerance mechanisms have opened new research avenues and therapeutic opportunities in this area. Here, we review mechanisms of immune tolerance and novel methods for its therapeutic induction.

VISTA checkpoint inhibition by pH-selective antibody SNS-101 with optimized safety and pharmacokinetic profiles enhances PD-1 response

VISTA, an inhibitory myeloid-T-cell checkpoint, holds promise as a target for cancer immunotherapy. However, its effective targeting has been impeded by issues such as rapid clearance and cytokine release syndrome observed with previous VISTA antibodies. Here we demonstrate that SNS-101, a newly developed pH-selective VISTA antibody, addresses these challenges. Structural and biochemical analyses confirmed the pH-selectivity and unique epitope targeted by SNS-101. These properties confer favorable pharmacokinetic and safety profiles on SNS-101. In syngeneic tumor models utilizing human VISTA knock-in mice, SNS-101 shows in vivo efficacy when combined with a PD-1 inhibitor, modulates cytokine and chemokine signaling, and alters the tumor microenvironment. In summary, SNS-101, currently in Phase I clinical trials, emerges as a promising therapeutic biologic for a wide range of patients whose cancer is refractory to current immunotherapy regimens.

Viewing the immune checkpoint VISTA: landscape and outcomes across cancers

BACKGROUND

Optimizing immune checkpoint inhibitor (ICI) therapy may require identification of co-targetable checkpoint pathways via immune profiling. Herein, we analyzed the transcriptomic expression and clinical correlates of V-domain immunoglobulin suppressor of T-cell activation (VISTA), a promising targetable checkpoint.

PATIENTS AND METHODS

RNA sequencing was carried out on 514 tissues reflecting diverse advanced/metastatic cancers. Expression of eight immune checkpoint markers [lymphocyte-activation gene 3 (LAG-3), tumor necrosis factor receptor superfamily 14 (TNFRSF14), programmed cell death protein 1 (PD-1), programmed death-ligand 1 (PD-L1), programmed death-ligand 2 (PD-L2), B- and T-lymphocyte attenuator (BTLA), T-cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), cytotoxic T-lymphocyte antigen 4 (CTLA-4)], in addition to VISTA, was analyzed, along with clinical outcomes.

RESULTS

High VISTA RNA expression was observed in 32% of tumors (66/514) and was the most common highly expressed checkpoint among the nine assessed. High VISTA expression was independently correlated with high BTLA, TIM-3, and TNFRSF14, and with a diagnosis of pancreatic, small intestine, and stomach cancer. VISTA transcript levels did not correlate with overall survival (OS) from metastatic/advanced disease in the pan-cancer cohort or with immunotherapy outcome (progression-free survival and OS from the start of ICI) in 217 ICI-treated patients. However, in ICI-treated pancreatic cancer patients (n = 16), median OS was significantly shorter (from immunotherapy initiation) for the high- versus not-high-VISTA groups (0.28 versus 1.21 years) (P = 0.047); in contrast, VISTA levels were not correlated with OS in 36 pancreatic cancer patients who did not receive ICI.

CONCLUSION

High VISTA expression correlates with high BTLA, TIM-3, and TNFRSF14 checkpoint-related molecules and with poorer post-immunotherapy survival in pancreatic cancer, consistent with prior literature indicating that VISTA is prominently expressed on CD68+ macrophages in pancreatic cancers and requiring validation in larger prospective studies. Immunomic analysis may be important for individualized precision immunotherapy.

Expression and function of VISTA on myeloid cells

V-domain containing Ig Suppressor of T cell Activation (VISTA) is predominantly expressed on myeloid cells and functions as a ligand/receptor/soluble molecule. In inflammatory responses and immune responses, VISTA regulates multiple functions of myeloid cells, such as chemotaxis, phagocytosis, T cell activation. Since inflammation and immune responses are critical in many diseases, VISTA is a promising therapeutic target. In this review, we will describe the expression and function of VISTA on different myeloid cells, including neutrophils, monocytes, macrophages, dendritic cells (DCs), myeloid-derived suppressor cells (MDSCs). In addition, we will discuss whether the functions of VISTA on these cells impact the disease processing.

VISTA drives macrophages towards a pro-tumoral phenotype that promotes cancer cell phagocytosis yet down-regulates T cell responses

BACKGROUND

VISTA is a well-known immune checkpoint in T cell biology, but its role in innate immunity is less established. Here, we investigated the role of VISTA on anticancer macrophage immunity, with a focus on phagocytosis, macrophage polarization and concomitant T cell activation.

METHODS

Macrophages, differentiated from VISTA overexpressed THP-1 cells and cord blood CD34+ cell-derived monocytes, were used in phagocytosis assay using B lymphoma target cells opsonized with Rituximab. PBMC-derived macrophages were used to assess the correlation between phagocytosis and VISTA expression. qRT-PCR, flow cytometry, and enzyme-linked immunosorbent assay were performed to analyze the impact of VISTA on other checkpoints and M1/M2-like macrophage biology. Additionally, flow cytometry was used to assess the frequency of CD14+ monocytes expressing VISTA in PBMCs from 65 lymphoma patients and 37 healthy donors.

RESULTS

Ectopic expression of VISTA in the monocytic model cell line THP-1 or in primary monocytes triggered differentiation towards the macrophage lineage, with a marked increase in M2-like macrophage-related gene expression and decrease in M1-like macrophage-related gene expression. VISTA expression in THP-1 and monocyte-derived macrophages strongly downregulated expression of SIRPα, a prominent 'don't eat me' signal, and augmented phagocytic activity of macrophages against cancer cells. Intriguingly, expression of VISTA's extracellular domain alone sufficed to trigger phagocytosis in ∼ 50% of cell lines, with those cell lines also directly binding to recombinant human VISTA, indicating ligand-dependent and -independent mechanisms. Endogenous VISTA expression was predominantly higher in M2-like macrophages compared to M0- or M1-like macrophages, with a positive correlation observed between VISTA expression in M2c macrophages and their phagocytic activity. VISTA-expressing macrophages demonstrated a unique cytokine profile, characterized by reduced IL-1β and elevated IL-10 secretion. Furthermore, VISTA interacted with MHC-I and downregulated its surface expression, leading to diminished T cell activation. Notably, VISTA surface expression was identified in monocytes from all lymphoma patients but was less prevalent in healthy donors.

CONCLUSIONS

Collectively, VISTA expression associates with and drives M2-like activation of macrophages with a high phagocytic capacity yet a decrease in antigen presentation capability to T cells. Therefore, VISTA is a negative immune checkpoint regulator in macrophage-mediated immune suppression.

Design, Synthesis, and Antitumor Activity Evaluation of Novel VISTA Small Molecule Inhibitors

VISTA (V-domain Ig suppressor of T cell activation) is a novel immune checkpoint protein and represents a promising target for cancer immunotherapy. Here, we report the design, synthesis, and evaluation of a series of methoxy-pyrimidine-based VISTA small molecule inhibitors with potent antitumor activity. By employing molecular docking and microscale thermophoresis (MST) assay, we identified a lead compound A1 that binds to VISTA protein with high affinity and optimized its structure. A4 was then obtained, which exhibited the strongest binding ability to VISTA protein, with a KD value of 0.49 ± 0.20 μM. In vitro, A4 significantly activated peripheral blood mononuclear cells (PBMCs) induced the release of cytokines such as IFN-γ and enhanced the cytotoxicity of PBMCs against tumor cells. In vivo, A4 displayed potent antitumor activity and synergized with PD-L1 antibody to enhance the therapeutic effect against cancer. These results suggest that compound A4 is an effective VISTA small molecule inhibitor, providing a basis for the future development of VISTA-targeted drugs.

Small-molecule agents for cancer immunotherapy

Cancer immunotherapy, exemplified by the remarkable clinical benefits of the immune checkpoint blockade and chimeric antigen receptor T-cell therapy, is revolutionizing cancer therapy. They induce long-term tumor regression and overall survival benefit in many types of cancer. With the advances in our knowledge about the tumor immune microenvironment, remarkable progress has been made in the development of small-molecule drugs for immunotherapy. Small molecules targeting PRR-associated pathways, immune checkpoints, oncogenic signaling, metabolic pathways, cytokine/chemokine signaling, and immune-related kinases have been extensively investigated. Monotherapy of small-molecule immunotherapeutic drugs and their combinations with other antitumor modalities are under active clinical investigations to overcome immune tolerance and circumvent immune checkpoint inhibitor resistance. Here, we review the latest development of small-molecule agents for cancer immunotherapy by targeting defined pathways and highlighting their progress in recent clinical investigations.

Interferon autoantibodies as signals of a sick thymus

Type I interferons (IFN-I) are key immune messenger molecules that play an important role in viral defense. They act as a bridge between microbe sensing, immune function magnitude, and adaptive immunity to fight infections, and they must therefore be tightly regulated. It has become increasingly evident that thymic irregularities and mutations in immune genes affecting thymic tolerance can lead to the production of IFN-I autoantibodies (autoAbs). Whether these biomarkers affect the immune system or tissue integrity of the host is still controversial, but new data show that IFN-I autoAbs may increase susceptibility to severe disease caused by certain viruses, including SARS-CoV-2, herpes zoster, and varicella pneumonia. In this article, we will elaborate on disorders that have been identified with IFN-I autoAbs, discuss models of how tolerance to IFN-Is is lost, and explain the consequences for the host.

The B7:CD28 family and friends: Unraveling coinhibitory interactions

Immune responses must be tightly regulated to ensure both optimal protective immunity and tolerance. Costimulatory pathways within the B7:CD28 family provide essential signals for optimal T cell activation and clonal expansion. They provide crucial inhibitory signals that maintain immune homeostasis, control resolution of inflammation, regulate host defense, and promote tolerance to prevent autoimmunity. Tumors and chronic pathogens can exploit these pathways to evade eradication by the immune system. Advances in understanding B7:CD28 pathways have ushered in a new era of immunotherapy with effective drugs to treat cancer, autoimmune diseases, infectious diseases, and transplant rejection. Here, we discuss current understanding of the mechanisms underlying the coinhibitory functions of CTLA-4, PD-1, PD-L1:B7-1 and PD-L2:RGMb interactions and less studied B7 family members, including HHLA2, VISTA, BTNL2, and BTN3A1, as well as their overlapping and unique roles in regulating immune responses, and the therapeutic potential of these insights.

Repositioning baloxavir marboxil as VISTA agonist that ameliorates experimental asthma

V-type immunoglobulin domain-containing suppressor of T-cell activation (VISTA), a novel negative checkpoint regulator, plays an essential role in allergic pulmonary inflammation in mice. Treatment with a VISTA agonistic antibody could significantly improve asthma symptoms. Thus, for allergic asthma treatment, VISTA targeting may be a compelling approach. In this study, we examined the functional mechanism of VISTA in allergic pulmonary inflammation and screened the FDA-approved drugs for VISTA agonists. By using mass cytometry (CyTOF), we found that VISTA deficiency primarily increased lung macrophage infiltration in the OVA-induced asthma model, accompanied by an increased proportion of M1 macrophages (CD11b+F4/80+CD86+) and a decreased proportion of M2 macrophages (CD11b+F4/80+CD206+). Further in vitro studies showed that VISTA deficiency promoted M1 polarization and inhibited M2 polarization of bone marrow-derived macrophages (BMDMs). Importantly, we discovered baloxavir marboxil (BXM) as a VISTA agonist by virtual screening of FDA-approved drugs. The surface plasmon resonance (SPR) assays revealed that BXM (KD = 1.07 µM) as well as its active form, baloxavir acid (BXA) (KD = 0.21 µM), could directly bind to VISTA with high affinity. Notably, treatment with BXM significantly ameliorated asthma symptoms, including less lung inflammation, mucus secretion, and the generation of Th2 cytokines (IL-5, IL-13, and IL-4), which were dramatically attenuated by anti-VISTA monoclonal antibody treatment. BXM administration also reduced the pulmonary infiltration of M1 macrophages and raised M2 macrophages. Collectively, our study indicates that VISTA regulates pulmonary inflammation in allergic asthma by regulating macrophage polarization and baloxavir marboxil, and an old drug might be a new treatment for allergic asthma through targeting VISTA.

PD-1H/VISTA mediates immune evasion in acute myeloid leukemia

Acute myeloid leukemia (AML) presents a pressing medical need in that it is largely resistant to standard chemotherapy as well as modern therapeutics, such as targeted therapy and immunotherapy, including anti-programmed cell death protein (anti-PD) therapy. We demonstrate that programmed death-1 homolog (PD-1H), an immune coinhibitory molecule, is highly expressed in blasts from the bone marrow of AML patients, while normal myeloid cell subsets and T cells express PD-1H. In studies employing syngeneic and humanized AML mouse models, overexpression of PD-1H promoted the growth of AML cells, mainly by evading T cell-mediated immune responses. Importantly, ablation of AML cell-surface PD-1H by antibody blockade or genetic knockout significantly inhibited AML progression by promoting T cell activity. In addition, the genetic deletion of PD-1H from host normal myeloid cells inhibited AML progression, and the combination of PD-1H blockade with anti-PD therapy conferred a synergistic antileukemia effect. Our findings provide the basis for PD-1H as a potential therapeutic target for treating human AML.

Unraveling the potential of CD8, CD68, and VISTA as diagnostic and prognostic markers in patients with pancreatic ductal adenocarcinoma

Introduction

Pancreatic cancer is a truculent disease with limited treatment options and a grim prognosis. Immunotherapy has shown promise in treating various types of cancer, but its effectiveness in pancreatic cancer has been lacking. As a result, it is crucial to identify markers associated with immunological pathways in order to improve the treatment outcomes for this deadly cancer. The purpose of this study was to investigate the diagnostic and prognostic significance of three markers, CD8, CD68, and VISTA, in pancreatic ductal adenocarcinoma (PDAC), the most common subtype of pancreatic cancer.

Methods

We analyzed gene expression data from Gene Expression Omnibus (GEO) database using bioinformatics tools. We also utilized the STRING online tool and Funrich software to study the protein-protein interactions and transcription factors associated with CD8, CD68, and VISTA. In addition, tissue microarray (TMA) and immunohistochemistry (IHC) staining were performed on 228 samples of PDAC tissue and 10 samples of normal pancreatic tissue to assess the expression levels of the markers. We then correlated these expression levels with the clinicopathological characteristics of the patients and evaluated their survival rates.

Results

The analysis of the GEO data revealed slightly elevated levels of VISTA in PDAC samples compared to normal tissues. However, there was a significant increase in CD68 expression and a notable reduction in CD8A expression in pancreatic cancer. Further investigation identified potential protein-protein interactions and transcription factors associated with these markers. The IHC staining of PDAC tissue samples showed an increased expression of VISTA, CD68, and CD8A in pancreatic cancer tissues. Moreover, we found correlations between the expression levels of these markers and certain clinicopathological features of the patients. Additionally, the survival analysis revealed that high expression of CD8 was associated with better disease-specific survival and progression-free survival in PDAC patients.

Conclusion

These findings highlight the potential of CD8, CD68, and VISTA as diagnostic and prognostic indicators in PDAC.

Immune Inhibitory Molecule PD-1 Homolog (VISTA) Colocalizes with CD11b Myeloid Cells in Melanoma and Is Associated with Poor Outcomes

Tumors evade immunity through the overexpression of immune inhibitory molecules in the tumor microenvironment such as PD-L1/B7-H1. An immune inhibitory molecule named PD-1 homolog (also known as V-domain Ig-containing suppressor of T cell activation [VISTA]) functions to control both T cells and myeloid cells. Current clinical trials using anti-VISTA-blocking agents for treatment of cancer are ongoing. We sought to determine the extent of VISTA expression in primary cutaneous melanomas (n = 190), identify the critical cell types expressing VISTA, and correlate its expression with PD-L1 expression using multiplexed quantitative immunofluorescence. Within the tumor subcompartments, VISTA is most highly expressed on CD11b myeloid cells, and PD-L1 is most highly expressed on CD68 myeloid cells in our melanoma cohort. There is little correlation between VISTA and PD-L1 expression intensity, suggesting that individual tumors have distinct immunosuppressive tumor microenvironments. High levels of VISTA expression on CD11b myeloid cells but not PD-L1 expression were associated with greater melanoma recurrence and greater all-cause mortality. Our findings suggest that cell-specific VISTA expression may be a negative prognostic biomarker for melanoma and a future potential therapeutic target.

Imatinib and M351-0056 enhance the function of VISTA and ameliorate the development of SLE via IFN-I and noncanonical NF-κB pathway

V-domain immunoglobulin suppressor of T-cell activation (VISTA), an important negative checkpoint protein, participates in immunoregulation. Systemic lupus erythematosus (SLE) is an autoimmune disease in which patients exhibit high levels of autoantibodies and multi-organ tissue injury, primarily involving the kidney and skin. In wild-type (WT) mice and Vsir-/- mice with pristane-induced lupus-like disease, we found that VISTA deficiency exacerbated the lupus-like disease in mice, possibly through aberrant activation of type I interferon (IFN-I) signaling, CD4+ T cell, and noncanonical nuclear factor-κB (NF-κB) pathway. Surface plasmon resonance results showed that imatinib, an FDA-approved tyrosine kinase inhibitor, may have a high affinity for human VISTA-ECD with a KD value of 0.2009 μM. The biological activities of imatinib and VISTA agonist M351-0056 were studied in monocytes and T cells and in lupus-like disease murine model of chronic graft-versus-host disease (cGVHD) and lupus-prone MRL/lpr mice. VISTA small-molecule agonist reduced the cytokine production of peripheral blood mononuclear cells (PBMCs) and Jurkat cells and inhibited PBMCs proliferation. Moreover, they attenuated the levels of autoantibodies, renal injury, inflammatory cytokines, chemokines, and immune cell expansion in the cGVHD mouse model and MRL/lpr mice. Our findings also demonstrated that VISTA small-molecule agonist ameliorated the development of SLE through improving aberrantly activated IFN-I signaling and noncanonical NF-κB pathway. In conclusion, VISTA has a protective effect on the development and progression of SLE. VISTA agonist M351-0056 and imatinib have been firstly demonstrated to attenuate SLE, suggesting interventions to enhance VISTA function may be effective in treating SLE. VISTA deficiency exacerbates pristane-induced lupus-like disease in mice by promoting activation of the IFN-I and noncanonical NF-κB pathway. Imatinib was screened as a small-molecule VISTA agonist by molecular docking, SPR, and cellular level experiments. VISTA agonists (M351-0056 and imatinib) alleviated lupus-like disease progression in the cGVHD mouse model and MRL/lpr mice by inhibiting activation of IFN-I and noncanonical NF-κB pathway.

Effective Antitumor Immunity Can Be Triggered by Targeting VISTA in Combination with a TLR3-Specific Adjuvant

Resistance to anti-PD-1/PD-L1 treatment is often associated with accumulation of intratumoral inhibitory macrophages. V-domain immunoglobulin suppressor of T-cell activation (VISTA) is a nonredundant immune checkpoint that can induce both T-cell and myeloid-cell immunosuppression. In this study, we found that high levels of VISTA+ immune cells were associated with advanced stage bladder cancer and predicted poor survival in patients. A combination of high infiltration of VISTA+ immune cells and PD-L1+ immune cells or PD-1+ T cells predicted the worst survival. Flow cytometry and multiplex immunofluorescence analyses confirmed that VISTA expression was higher in macrophages than in T cells or neutrophils, and only VISTA+CD163+ macrophage density predicted poor prognosis in patients with bladder cancer. Toll-like receptor (TLR) agonists are known to trigger the innate immune response in macrophages. We found that the VISTA-specific mAb 13F3 augmented the ability of a TLR3-specific adjuvant to induce macrophage activation in vitro. In the MB49 syngeneic mouse model of bladder cancer, treatment with 13F3 curbed tumor growth and prolonged survival when combined with a TLR3-specific adjuvant. The combination treatment reduced the intratumoral frequency of CD206+ anti-inflammatory macrophages and levels of the immunosuppressive molecule TGFβ1, but it upregulated expression of immunostimulatory molecules (Ifna, Ifnb, and Trail) and increased the CD8+ T cell/regulatory T-cell ratio. These findings indicate that elevated VISTA expression in immune cells, particularly macrophages, is associated with an unfavorable prognosis in patients with bladder cancer and suggest that targeting VISTA in combination with a TLR3-specific adjuvant has translational potential.

Alternative immune checkpoints in immunoregulatory profile of cancer stem cells

Tumor-mediated bypass of immune checkpoint inhibitor (ICI) therapy with anti-programmed death-1 (PD-1), anti-programmed death-ligand 1 (PD-L1, also called B7-H1 or CD274) or anti-cytotoxic T lymphocyte associated antigen-4 (CTLA-4) is a challenge of current years in the area of cancer immunotherapy. Alternative immune checkpoints (AICs) are molecules beyond the common PD-1, PD-L1 or CTLA-4, and are upregulated in patients who show low/no ICI responses. These are members of B7 family including B7-H2 (ICOS-L), B7-H3 (CD276), B7-H4 (B7x), V-domain immunoglobulin suppressor of T cell activation (VISTA), B7-H6, HHLA2 (B7-H5/B7-H7) and catabolic enzymes like indoleamine 2,3-dioxygenase 1 (IDO1), and others that are also contributed to the regulation of tumor immune microenvironment (TIME). There is also strong evidence supporting the implication of AICs in regulation of cancer stemness and expanding the population of cancer stem cells (CSCs). CSCs display immunoregulatory capacity and represent multiple immune checkpoints either on their surface or inside. Besides, they are active promoters of resistance to the common ICIs. The aim of this review is to investigate interrelations between AICs with stemness and differentiation profile of cancer. The key message of this paper is that targeted checkpoints can be selected based on their impact on CSCs along with their effect on immune cells. Studies published so far mainly focused on immune cells as a target for anti-checkpoints. Ex vivo engineering of extracellular vesicles (EVs) equipped with CSC-targeted anti-checkpoint antibodies is without a doubt a key therapeutic target that can be under consideration in future research.

Advances in immune checkpoint-based immunotherapies for multiple sclerosis: rationale and practice

Beyond the encouraging results and broad clinical applicability of immune checkpoint (ICP) inhibitors in cancer therapy, ICP-based immunotherapies in the context of autoimmune disease, particularly multiple sclerosis (MS), have garnered considerable attention and hold great potential for developing effective therapeutic strategies. Given the well-established immunoregulatory role of ICPs in maintaining a balance between stimulatory and inhibitory signaling pathways to promote immune tolerance to self-antigens, a dysregulated expression pattern of ICPs has been observed in a significant proportion of patients with MS and its animal model called experimental autoimmune encephalomyelitis (EAE), which is associated with autoreactivity towards myelin and neurodegeneration. Consequently, there is a rationale for developing immunotherapeutic strategies to induce inhibitory ICPs while suppressing stimulatory ICPs, including engineering immune cells to overexpress ligands for inhibitory ICP receptors, such as program death-1 (PD-1), or designing fusion proteins, namely abatacept, to bind and inhibit the co-stimulatory pathways involved in overactivated T-cell mediated autoimmunity, and other strategies that will be discussed in-depth in the current review. Video Abstract.

VISTA and its ligands: the next generation of promising therapeutic targets in immunotherapy

V-domain immunoglobulin suppressor of T cell activation (VISTA) is a novel negative checkpoint receptor (NCR) primarily involved in maintaining immune tolerance. It has a role in the pathogenesis of autoimmune disorders and cancer and has shown promising results as a therapeutic target. However, there is still some ambiguity regarding the ligands of VISTA and their interactions with each other. While V-Set and Immunoglobulin domain containing 3 (VSIG-3) and P-selectin glycoprotein ligand-1(PSGL-1) have been extensively studied as ligands for VISTA, the others have received less attention. It seems that investigating VISTA ligands, reviewing their functions and roles, as well as outcomes related to their interactions, may allow an understanding of their full functionality and effects within the cell or the microenvironment. It could also help discover alternative approaches to target the VISTA pathway without causing related side effects. In this regard, we summarize current evidence about VISTA, its related ligands, their interactions and effects, as well as their preclinical and clinical targeting agents.

VISTA Expression on Cancer-Associated Endothelium Selectively Prevents T-cell Extravasation

Cancers evade T-cell immunity by several mechanisms such as secretion of anti-inflammatory cytokines, down regulation of antigen presentation machinery, upregulation of immune checkpoint molecules, and exclusion of T cells from tumor tissues. The distribution and function of immune checkpoint molecules on tumor cells and tumor-infiltrating leukocytes is well established, but less is known about their impact on intratumoral endothelial cells. Here, we demonstrated that V-domain Ig suppressor of T-cell activation (VISTA), a PD-L1 homolog, was highly expressed on endothelial cells in synovial sarcoma, subsets of different carcinomas, and immune-privileged tissues. We created an ex vivo model of the human vasculature and demonstrated that expression of VISTA on endothelial cells selectively prevented T-cell transmigration over endothelial layers under physiologic flow conditions, whereas it does not affect migration of other immune cell types. Furthermore, endothelial VISTA correlated with reduced infiltration of T cells and poor prognosis in metastatic synovial sarcoma. In endothelial cells, we detected VISTA on the plasma membrane and in recycling endosomes, and its expression was upregulated by cancer cell-secreted factors in a VEGF-A-dependent manner. Our study reveals that endothelial VISTA is upregulated by cancer-secreted factors and that it regulates T-cell accessibility to cancer and healthy tissues. This newly identified mechanism should be considered when using immunotherapeutic approaches aimed at unleashing T cell-mediated cancer immunity.

Novel targets for immune-checkpoint inhibition in cancer

Immune-checkpoint inhibitors have revolutionized cancer therapy, yet many patients either do not derive any benefit from treatment or develop a resistance to checkpoint inhibitors. Intrinsic resistance can result from neoantigen depletion, defective antigen presentation, PD-L1 downregulation, immune-checkpoint ligand upregulation, immunosuppression, and tumor cell phenotypic changes. On the other hand, extrinsic resistance involves acquired upregulation of inhibitory immune-checkpoints, leading to T-cell exhaustion. Current data suggest that PD-1, CTLA-4, and LAG-3 upregulation limits the efficacy of single-agent immune-checkpoint inhibitors. Ongoing clinical trials are investigating novel immune-checkpoint targets to avoid or overcome resistance. This review provides an in-depth analysis of the evolving landscape of potentially targetable immune-checkpoints in cancer. We highlight their biology, emphasizing the current understanding of resistance mechanisms and focusing on promising strategies that are under investigation. We also summarize current results and ongoing clinical trials in this crucial field that could once again revolutionize outcomes for cancer patients.

13C tracer analysis reveals the landscape of metabolic checkpoints in human CD8+ T cell differentiation and exhaustion

Introduction

Naïve T cells remain in an actively maintained state of quiescence until activation by antigenic signals, upon which they start to proliferate and generate effector cells to initiate a functional immune response. Metabolic reprogramming is essential to meet the biosynthetic demands of the differentiation process, and failure to do so can promote the development of hypofunctional exhausted T cells.

Methods

Here we used 13C metabolomics and transcriptomics to study the metabolism of CD8+ T cells in their complete course of differentiation from naïve over stem-like memory to effector cells and in exhaustion-inducing conditions.

Results

The quiescence of naïve T cells was evident in a profound suppression of glucose oxidation and a decreased expression of ENO1, downstream of which no glycolytic flux was detectable. Moreover, TCA cycle activity was low in naïve T cells and associated with a downregulation of SDH subunits. Upon stimulation and exit from quiescence, the initiation of cell growth and proliferation was accompanied by differential expression of metabolic enzymes and metabolic reprogramming towards aerobic glycolysis with high rates of nutrient uptake, respiration and lactate production. High flux in anabolic pathways imposed a strain on NADH homeostasis, which coincided with engagement of the proline cycle for mitochondrial redox shuttling. With acquisition of effector functions, cells increasingly relied on glycolysis as opposed to oxidative phosphorylation, which was, however, not linked to changes in mitochondrial abundance. In exhaustion, decreased effector function concurred with a reduction in mitochondrial metabolism, glycolysis and amino acid import, and an upregulation of quiescence-associated genes, TXNIP and KLF2, and the T cell suppressive metabolites succinate and itaconate.

Discussion

Overall, these results identify multiple metabolic features that regulate quiescence, proliferation and effector function, but also exhaustion of CD8+ T cells during differentiation. Thus, targeting these metabolic checkpoints may be a promising therapeutic strategy for both prevention of exhaustion and promotion of stemness of anti-tumor T cells.

Combinatorial blockade for cancer immunotherapy: targeting emerging immune checkpoint receptors

The differentiation, survival, and effector function of tumor-specific CD8+ cytotoxic T cells lie at the center of antitumor immunity. Due to the lack of proper costimulation and the abundant immunosuppressive mechanisms, tumor-specific T cells show a lack of persistence and exhausted and dysfunctional phenotypes. Multiple coinhibitory receptors, such as PD-1, CTLA-4, VISTA, TIGIT, TIM-3, and LAG-3, contribute to dysfunctional CTLs and failed antitumor immunity. These coinhibitory receptors are collectively called immune checkpoint receptors (ICRs). Immune checkpoint inhibitors (ICIs) targeting these ICRs have become the cornerstone for cancer immunotherapy as they have established new clinical paradigms for an expanding range of previously untreatable cancers. Given the nonredundant yet convergent molecular pathways mediated by various ICRs, combinatorial immunotherapies are being tested to bring synergistic benefits to patients. In this review, we summarize the mechanisms of several emerging ICRs, including VISTA, TIGIT, TIM-3, and LAG-3, and the preclinical and clinical data supporting combinatorial strategies to improve existing ICI therapies.

PSGL-1: a novel immune checkpoint driving T-cell dysfunction in obstructive sleep apnea

Introduction

Although higher incidence of cancer represents a major burden for obstructive sleep apnea (OSA) patients, the molecular pathways driving this association are not completely understood. Recently, the adhesion receptor P-selectin glycoprotein-1 (PSGL 1) has been identified as a novel immune checkpoint, which are recognized major hallmarks in several types of cancer and have revolutionized cancer therapy.

Methods

The expression of PSGL-1 and its ligands VISTA and SIGLEC-5 was assessed in the leucocytes of OSA patients and control subjects exploring the role of intermittent hypoxia (IH) using in vitro models. In addition, PSGL-1 impact on T-cells function was evaluated by ex vivo models.

Results

Data showed PSGL-1 expression is upregulated in the T-lymphocytes from patients with severe OSA, indicating a relevant role of hypoxemia mediated by intermittent hypoxia. Besides, results suggest an inhibitory role of PSGL-1 on T-cell proliferation capacity. Finally, the expression of SIGLEC-5 but not VISTA was increased in monocytes from OSA patients, suggesting a regulatory role of intermittent hypoxia.

Discussion

In conclusion, PSGL-1 might constitute an additional immune checkpoint leading to T-cell dysfunction in OSA patients, contributing to the disruption of immune surveillance, which might provide biological plausibility to the higher incidence and aggressiveness of several tumors in these patients.

The role of interferon in the thymus

Interferons (IFNs) are a family of proteins that are generated in response to viral infection and induce an antiviral response in many cell types. The COVID-19 pandemic revealed that patients with inborn errors of type-I IFN immunity were more prone to severe infections, but also found that many patients with severe COVID-19 had anti-IFN autoantibodies that led to acquired defects in type-I IFN immunity. These findings revealed the previously unappreciated finding that central immune tolerance to IFN is essential to immune health. Further evidence has also highlighted the importance of IFN within the thymus and its impact on T-cell development. This review will highlight what is known of IFN's role in T-cell development, T-cell central tolerance, and the impact of IFN on the thymus.