Beyond T-Cells: Functional Characterization of CTLA-4 Expression in Immune and Non-Immune Cell Types

Antigen-experienced CXCR5- CD19low B cells are plasmablast precursors expanded in SLE

OBJECTIVES

Altered composition of the B cell compartment in the pathogenesis of systemic lupus erythematosus (SLE) is characterized by expanded plasmablast (PB) and IgD^- CD27^- double negative (DN) B cell populations. Previous studies showed that DN B cells represent a heterogeneous subset and further characterization is needed.

METHODS

Therefore, we analyzed two independent cohorts of healthy donors and SLE patients using a combined approach of flow (HD: n=16; SLE: n=28,) and mass cytometry (HD: n=18; SLE: n=24) and targeted RNA sequencing. To study B cell subsets formation in acute immune response versus autoimmunity we investigated HDs at various time points upon vaccination with BNT162b2 or during acute COVID-19 infection using flow cytometry.

RESULTS

We have found that IgD^- CD27⁺ switched and atypical IgD^- CD27^- memory B cells, which are increased in SLE, represent heterogeneous populations composed of three different subsets each. Populations of CXCR5⁺ CD19^int , CXCR5^- CD19^high and CXCR5^- CD19^low are found in both compartments suggesting their relationship. We characterize a hitherto unknown and antigen-experienced CXCR5^- CD19^low subset enhanced in SLE carrying a PB phenotype with diminished B cell receptor responsiveness and expression of CD38, CD95, CD71, PRDM1, XBP-1, and IRF4. CXCR5^- CD19^low subsets are increased and correlate with PB frequencies in SLE and upon BNT162b2-vaccination of HD suggesting their interrelationship and contribution to plasmacytosis. The demonstration of CXCR5^- CD19^low B cells amongst both CD27+ and CD27- cells questions the role of CD27 as reliable marker for B cell differentiation.

CONCLUSION

Our data suggest that CXCR5^- CD19^low B cells are precursors of plasmablasts, thus co-targeting this subset may have therapeutic value in SLE.

Immunomodulatory Properties of Immune Checkpoint Inhibitors-More than Boosting T-Cell Responses?

The approval of immune checkpoint inhibitors (ICI) that serve to enhance effector T-cell anti-tumor responses has strongly improved success rates in the treatment of metastatic melanoma and other tumor types. The currently approved ICI constitute monoclonal antibodies blocking cytotoxic T-lymphocyte-associated protein (CTLA)-4 and anti-programmed cell death (PD)-1. By this, the T-cell-inhibitory CTLA-4/CD80/86 and PD-1/PD-1L/2L signaling axes are inhibited. This leads to sustained effector T-cell activity and circumvents the immune evasion of tumor cells, which frequently upregulate PD-L1 expression and modulate immune checkpoint molecule expression on leukocytes. As a result, profound clinical responses are observed in 40-60% of metastatic melanoma patients. Despite the pivotal role of T effector cells for triggering anti-tumor immunity, mounting evidence indicates that ICI efficacy may also be attributable to other cell types than T effector cells. In particular, emerging research has shown that ICI also impacts innate immune cells, such as myeloid cells, natural killer cells and innate lymphoid cells, which may amplify tumoricidal functions beyond triggering T effector cells, and thus improves clinical efficacy. Effects of ICI on non-T cells may additionally explain, in part, the character and extent of adverse effects associated with treatment. Deeper knowledge of these effects is required to further develop ICI treatment in terms of responsiveness of patients to treatment, to overcome resistance to ICI and to alleviate adverse effects. In this review we give an overview into the currently known immunomodulatory effects of ICI treatment in immune cell types other than the T cell compartment.

Leveraging self-assembled nanobiomaterials for improved cancer immunotherapy

Nanomaterials and targeted drug delivery vehicles improve the therapeutic index of drugs and permit greater control over their pharmacokinetics, biodistribution, and bioavailability. Here, nanotechnologies applied to cancer immunotherapy are discussed with a focus on current and next generation self-assembling drug delivery systems composed of lipids and/or polymers. Topics covered include the fundamental design, suitability, and inherent properties of nanomaterials that induce anti-tumor immune responses and support anti-cancer vaccination. Established active and passive targeting strategies as well as newer "indirect" methods are presented together with insights into how nanocarrier structure and surface chemistry can be leveraged for controlled delivery to the tumor microenvironment while minimizing off-target effects.

DNA Damage Repair in Brain Tumor Immunotherapy

With the gradual understanding of tumor development, many tumor therapies have been invented and applied in clinical work, and immunotherapy has been widely concerned as an emerging hot topic in the last decade. It is worth noting that immunotherapy is nowadays applied under too harsh conditions, and many tumors are defined as “cold tumors” that are not sensitive to immunotherapy, and brain tumors are typical of them. However, there is much evidence that suggests a link between DNA damage repair mechanisms and immunotherapy. This may be a breakthrough for the application of immunotherapy in brain tumors. Therefore, in this review, first, we will describe the common pathways of DNA damage repair. Second, we will focus on immunotherapy and analyze the mechanisms of DNA damage repair involved in the immune process. Third, we will review biomarkers that have been or may be used to evaluate immunotherapy for brain tumors, such as TAMs, RPA, and other molecules that may provide a precursor assessment for the rational implementation of immunotherapy for brain tumors. Finally, we will discuss the rational combination of immunotherapy with other therapeutic approaches that have an impact on the DNA damage repair process in order to open new pathways for the application of immunotherapy in brain tumors, to maximize the effect of immunotherapy on DNA damage repair mechanisms, and to provide ideas and guidance for immunotherapy in brain tumors.

HLA-G and Other Immune Checkpoint Molecules as Targets for Novel Combined Immunotherapies

HLA-G is an HLA-class Ib molecule that is involved in the establishment of tolerance at the maternal/fetal interface during pregnancy. The expression of HLA-G is highly restricted in adults, but the de novo expression of this molecule may be observed in different hematological and solid tumors and is related to cancer progression. Indeed, tumor cells expressing high levels of HLA-G are able to suppress anti-tumor responses, thus escaping from the control of the immune system. HLA-G has been proposed as an immune checkpoint (IC) molecule due to its crucial role in tumor progression, immune escape, and metastatic spread. We here review data available in the literature in which the interaction between HLA-G and other IC molecules is reported, in particular PD-1, CTLA-4, and TIM-3, but also IDO and TIGIT. Clinical trials using monoclonal antibodies against HLA-G and other IC are currently ongoing with cancer patients where antibodies and inhibitors of PD-1 and CTLA-4 showed encouraging results. With this background, we may envisage that combined therapies using antibodies targeting HLA-G and another IC may be successful for clinical purposes. Indeed, such immunotherapeutic protocols may achieve a better rescue of effective anti-tumor immune response, thus improving the clinical outcome of patients.

Molecular Mechanisms of Tumor Immunomodulation in the Microenvironment of Colorectal Cancer

Colorectal cancer remains one of the most important health challenges in our society. The development of cancer immunotherapies has fostered the need to better understand the anti-tumor immune mechanisms at play in the tumor microenvironment and the strategies by which the tumor escapes them. In this review, we provide an overview of the molecular interactions that regulate tumor inflammation. We particularly discuss immunomodulatory cell-cell interactions, cell-soluble factor interactions, cell-extracellular matrix interactions and cell-microbiome interactions. While doing so, we highlight relevant examples of tumor immunomodulation in colorectal cancer.

Next generation of immune checkpoint molecules in maternal-fetal immunity

Successful pregnancy is a unique situation requires the maternal immune system to recognize and tolerate a semi-identical fetus and allow normal invasion of trophoblast cells. Although efforts have been made, the deep mechanisms of the maternal-fetal crosstalk have not yet been fully deciphered. Immune checkpoint molecules (ICMs) are a group of negative modulators of the immune response that avoid immune damage. They have been extensively studied in the fields of oncology and transplantation, while the latest evidence suggests that they are closely associated with pregnancy outcomes via multiple inhibitory mechanisms. Although studies have mostly demonstrated the regulatory role of the well-known PD-1, CTLA-4 at the maternal-fetal interface, what is unique about the newly discovered multiple ICMs remains a mystery. Here, we review the latest knowledge on ICMs, focusing on the first generation of checkpoints (PD-1, CTLA-4) and the next generation (Tim-3, Tigit, Lag-3, VISTA) highlighting their immunoregulatory roles in maternal-fetal tolerance and decidual vascular remodeling, and their involvement in pathological pregnancies. The content covers three aspects: the characteristics they possess, the dynamic expression profile of their expression at the maternal-fetal interface, and their involvement in pathological pregnancy. In immunotherapy strategies for pregnancy complications, upregulation of immune checkpoints may play a role. Meanwhile, the impact on pregnancy outcomes when using ICMs in clinical cancer treatment during pregnancy is a topic worth exploring. These may serve as a guide for future basic research and clinical applications of maternal-fetal immunity.

Inborn Errors of Immunity and Their Phenocopies: CTLA4 and PD-1

Elucidating links between genotype and phenotype in patients with rare inborn errors of immunity (IEIs) provides insights into mechanisms of immune regulation. In many autosomal dominant IEIs, however, variation in expressivity and penetrance result in complex genotype-phenotype relations, while some autosomal recessive IEIs are so rare that it is difficult to draw firm conclusions. Phenocopies arise when an environmental or non-genetic factor replicates a phenotype conferred by a specific genotype. Phenocopies can result from therapeutic antibodies or autoantibodies that target a protein to replicate aspects of the phenotype conferred by mutations in the gene encoding the same protein. Here, we consider IEIs arising from rare genetic variants in CTLA4 and PDCD1 and compare clinical and laboratory manifestations arising as drug-induced phenocopies (immune related adverse events, IRAEs) in cancer patients treated with immune checkpoint inhibitors (ICI) and identify outstanding questions regarding mechanism of disease.

Immune checkpoints and liver resection after neoadjuvant chemotherapy including bevacizumab in patients with microsatellite-stable colorectal liver metastases

BACKGROUND

The clinical value of immune checkpoint expression as prognostic biomarker in bevacizumab-pretreated patients with resected microsatellite-stable (MMS) colorectal liver metastases is unclear and was retrospectively investigated in this study.

METHODS

Expression analyses of IDO-1, PD-L1, and CTLA-4 were performed by immunohistochemistry in resected bevacizumab-pretreated colorectal liver metastases. Association of immune checkpoint expression in tumor cells and immune cells with response and clinical outcome was investigated. Expression profiles were compared with those of patients with anti-EGFR-targeted therapy and lung metastases, respectively.

RESULTS

One hundred thirty-six patients with MMS disease were investigated (79 (58.1%) male/57 (41.9%) female, median age 62.9 years (range 31.0-80.4)). High expression of IDO-1 in immune cells was associated with longer OS (not reached versus 44.8 months, HR 0.23 (95% CI 0.09, 0.55), P = 0.001). Low expression of CTLA-4 in tumor cells was associated with better histological response (26 major, 19 partial, 18 none versus 14 major, 23 partial, 30 none, P = 0.032). Expression profiles differed compared to patients with anti-EGFR-targeted therapy and patients with lung metastases.

CONCLUSION

Immune checkpoint expression was associated with response and survival. IDO-1 may serve as a novel prognostic and/or predictive biomarker in patients with MMS colorectal liver metastases.

Monoclonal Antibodies to CTLA-4 with Focus on Ipilimumab

The immune checkpoint cytotoxic T lymphocyte-associated antigen 4 (CTLA-4 or CD152) is a negative regulator of T-cell-mediated immune responses which plays a critical role in suppressing autoimmunity and maintaining immune homeostasis. Because of its inhibitory activity on T cells, CTLA-4 has been investigated as a drug target to induce immunostimulation, blocking the interaction with its ligands. The antitumor effects mediated by CTLA-4 blockade have been attributed to a sustained active immune response against cancer cells, due to the release of a brake on T cell activation. Ipilimumab (Yervoy, Bristol-Myers Squibb) is a fully human anti-CTLA-4 IgG1κ monoclonal antibody (mAb) that represents the first immune checkpoint inhibitor approved as monotherapy by FDA and EMA in 2011 for the treatment of unresectable/metastatic melanoma. In 2015, FDA also granted approval to ipilimumab monotherapy as adjuvant treatment of stage III melanoma to reduce the risk of tumour recurrence. The subsequent approved indications of ipilimumab for metastatic melanoma, regardless of BRAF mutational status, and other advanced/metastatic solid tumours always involve its use in association with the anti-programmed cell death protein 1 (PD-1) mAb nivolumab. Currently, ipilimumab is evaluated in ongoing clinical trials for refractory/advanced solid tumours mainly in combination with additional immunostimulating agents.

[Research Progress of Circular RNAs in Tumor Immunotherapy]

Tumor immunotherapy is a new therapy which developed in recent years, it has greatly changed the therapeutic schedules and brought new options for patients. However, not all patients can have obvious therapeutic effects after using immunotherapy. So selecting more suitable patients and raising immunotherapy effect are worthy to discuss. With the research of circular RNAs (circRNAs), circRNAs have been found that they not only play a significant role in the field of tumor markers, tumor progression and prognosis, but also can abnormally express in a variety of tumors and affect tumor immunity. Therefore, the circRNAs expression may not only can be used as a supplementary method for selecting patients, but also can be used to predict the efficacy of tumor immunotherapy. In this article, we summarize current knowledge on circRNAs abnormally expressed in many cancers, especially lung cancer which can affect tumor immunity, and discuss its potential effects in tumor immunotherapy, and we hope to provide more references for the clinical practice of circRNAs.
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PD-1-stimulated T cell subsets are transcriptionally and functionally distinct

Despite the obvious inhibitory outcome of PD-1 signaling, an additional series of functions are activated. We have observed that T cells stimulated through the T cell receptor (TCR) and PD-1 primarily do not proliferate; however, there is a population of cells that proliferates more than through TCR stimulation alone. In this study, we performed flow cytometry and RNA sequencing on individual populations of T cells and discovered that unlike naive T cells, which were inhibited following PD-1 ligation, T cells that proliferated more following PD-1 ligation were associated with effector and central memory phenotypes. We showed that these populations had different gene expression profiles following PD-1 ligation with PD-L1 compared to PD-L2. The presence of transcriptionally and functionally distinct T cell populations responsive to PD-1 ligation provides new insights into the biology of PD-1 and suggest the use of T cell subset-specific approaches to improve the clinical outcome of PD-1 blockade.

Tafazzin deficiency in mouse mesenchymal stem cells potentiates their immunosuppression and impairs activated B lymphocyte immune function

Barth Syndrome (BTHS) is a rare X-linked genetic disorder caused by mutation in the TAFAZZIN gene which encodes the cardiolipin (CL) transacylase tafazzin (Taz). Taz deficiency in BTHS patients results in reduced CL in their tissues and a neutropenia which contributes to the risk of infections. However, the impact of Taz deficiency in other cells of the immune system is poorly understood. Mesenchymal stem cells (MSCs) are well known for their immune inhibitory function. We examined whether Taz-deficiency in murine MSCs impacted their ability to modulate lipopolysaccharide (LPS)-activated wild type (WT) murine B lymphocytes. MSCs from tafazzin knockdown (TazKD) mice exhibited a 50% reduction in CL compared to wild type (WT) MSCs. However, mitochondrial oxygen consumption rate and membrane potential were unaltered. In contrast, TazKD MSCs exhibited increased glycolysis compared to WT MSCs and this was associated with elevated proliferation, phosphatidylinositol-3-kinase expression and expression of the immunosuppressive markers indoleamine-2,3-dioxygenase, cytotoxic T-lymphocyte-associated protein 4, interleukin-10, and cluster of differentiation 59. When co-cultured with LPS-activated WT B cells, TazKD MSCs inhibited B cell proliferation and growth rate and reduced B cell secretion of IgM to a greater extent than B cells co-cultured with WT MSCs. In addition, co-culture of LPS-activated WT B cells with TazKD MSCs induced B cell differentiation toward potent immunosuppressive phenotypes including interleukin-10 secreting plasma cells and B regulatory cells compared to activated B cells co-cultured with WT MSCs. These results indicate that Taz deficiency in MSCs enhances MSCs-mediated immunosuppression of activated B lymphocytes.

Regulatory mechanisms of immune checkpoints PD-L1 and CTLA-4 in cancer

The cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4)/B7 and programmed death 1 (PD-1)/ programmed cell death-ligand 1 (PD-L1) are two most representative immune checkpoint pathways, which negatively regulate T cell immune function during different phases of T-cell activation. Inhibitors targeting CTLA-4/B7 and PD1/PD-L1 pathways have revolutionized immunotherapies for numerous cancer types. Although the combined anti-CTLA-4/B7 and anti-PD1/PD-L1 therapy has demonstrated promising clinical efficacy, only a small percentage of patients receiving anti-CTLA-4/B7 or anti-PD1/PD-L1 therapy experienced prolonged survival. Regulation of the expression of PD-L1 and CTLA-4 significantly impacts the treatment effect. Understanding the in-depth mechanisms and interplays of PD-L1 and CTLA-4 could help identify patients with better immunotherapy responses and promote their clinical care. In this review, regulation of PD-L1 and CTLA-4 is discussed at the levels of DNA, RNA, and proteins, as well as indirect regulation of biomarkers, localization within the cell, and drugs. Specifically, some potential drugs have been developed to regulate PD-L1 and CTLA-4 expressions with high efficiency.

Identification of CTLA-4-Positive Cells in the Human Tonsil

CTLA-4 (cytotoxic T-lymphocyte-associated protein 4) was originally defined as a T-lymphocyte antigen and was used as a target in cancer immunotherapy. Unfortunately, the existence of CTLA-4 in cells other than T-lymphocytes is often overlooked. The goal of the present study was to analyze the distribution pattern of CTLA-4 in the human tonsils using a panel of anti-CTLA-4 antibodies of different clones. We found that CTLA-4 was expressed in T-lymphocyte cells of various geneses, including hematopoietic cells and their derivatives (monocytes, macrophages, dendritic, plasma cells, mast cells, and neutrophils), as well as stromal cells of mesodermal (mesenchymal) origin and reticular epithelial cells of ectodermal origin. The expression of CTLA-4 in cells of different origins supports the proposition that CTLA-4 is not restricted to the lymphoid cell lineage and can provide broader effects of CTLA-4 on immune regulation.

Immune Checkpoints in Pediatric Solid Tumors: Targetable Pathways for Advanced Therapeutic Purposes

The tumor microenvironment (TME) represents a complex network between tumor cells and a variety of components including immune, stromal and vascular endothelial cells as well as the extracellular matrix. A wide panel of signals and interactions here take place, resulting in a bi-directional modulation of cellular functions. Many stimuli, on one hand, induce tumor growth and the spread of metastatic cells and, on the other hand, contribute to the establishment of an immunosuppressive environment. The latter feature is achieved by soothing immune effector cells, mainly cytotoxic T lymphocytes and B and NK cells, and/or through expansion of regulatory cell populations, including regulatory T and B cells, tumor-associated macrophages and myeloid-derived suppressor cells. In this context, immune checkpoints (IC) are key players in the control of T cell activation and anti-cancer activities, leading to the inhibition of tumor cell lysis and of pro-inflammatory cytokine production. Thus, these pathways represent promising targets for the development of effective and innovative therapies both in adults and children. Here, we address the role of different cell populations homing the TME and of well-known and recently characterized IC in the context of pediatric solid tumors. We also discuss preclinical and clinical data available using IC inhibitors alone, in combination with each other or administered with standard therapies.

Targeting Impaired Antimicrobial Immunity in the Brain for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia and aging is the most common risk factor for developing the disease. The etiology of AD is not known but AD may be considered as a clinical syndrome with multiple causal pathways contributing to it. The amyloid cascade hypothesis, claiming that excess production or reduced clearance of amyloid-beta (Aβ) and its aggregation into amyloid plaques, was accepted for a long time as the main cause of AD. However, many studies showed that Aβ is a frequent consequence of many challenges/pathologic processes occurring in the brain for decades. A key factor, sustained by experimental data, is that low-grade infection leading to production and deposition of Aβ, which has antimicrobial activity, precedes the development of clinically apparent AD. This infection is chronic, low grade, largely clinically silent for decades because of a nearly efficient antimicrobial immune response in the brain. A chronic inflammatory state is induced that results in neurodegeneration. Interventions that appear to prevent, retard or mitigate the development of AD also appear to modify the disease. In this review, we conceptualize further that the changes in the brain antimicrobial immune response during aging and especially in AD sufferers serve as a foundation that could lead to improved treatment strategies for preventing or decreasing the progression of AD in a disease-modifying treatment.