Inverse correlation of soluble programmed cell death-1 ligand-1 (sPD-L1) with eosinophil count and clinical severity in allergic rhinitis patients

The role of PD-1 signaling in health and immune-related diseases

Programmed cell death 1 receptor (PD-1) and its ligands constitute an inhibitory pathway to mediate the mechanism of immune tolerance and provide immune homeostasis. Significantly, the binding partners of PD-1 and its associated ligands are diverse, which facilitates immunosuppression in cooperation with other immune checkpoint proteins. Accumulating evidence has demonstrated the important immunosuppressive role of the PD-1 axis in the tumor microenvironment and in autoimmune diseases. In addition, PD-1 blockades have been approved to treat various cancers, including solid tumors and hematological malignancies. Here, we provide a comprehensive review of the PD-1 pathway, focusing on the structure and expression of PD-1, programmed cell death 1 ligand 1 (PD-L1), and programmed cell death 1 ligand 2 (PD-L2); the diverse biological functions of PD-1 signaling in health and immune-related diseases (including tumor immunity, autoimmunity, infectious immunity, transplantation immunity, allergy and immune privilege); and immune-related adverse events related to PD-1 and PD-L1 inhibitors.

Soluble TIM-3 as a biomarker of progression and therapeutic response in cancers and other of human diseases

Immune checkpoints inhibition is a privileged approach to combat cancers and other human diseases. The TIM-3 (T cell immunoglobulin and mucin-domain containing-3) inhibitory checkpoint expressed on different types of immune cells is actively investigated as an anticancer target, with a dozen of monoclonal antibodies in (pre)clinical development. A soluble form sTIM-3 can be found in the plasma of patients with cancer and other diseases. This active circulating protein originates from the proteolytic cleavage by two ADAM metalloproteases of the membrane receptor shared by tumor and non-tumor cells, and extracellular vesicles. In most cancers but not all, overexpression of mTIM-3 at the cell surface leads to high level of sTIM-3. Similarly, elevated levels of sTIM-3 have been reported in chronic autoimmune diseases, inflammatory gastro-intestinal diseases, certain viral and parasitic diseases, but also in cases of organ transplantation and in pregnancy-related pathologies. We have analyzed the origin of sTIM-3, its methods of dosage in blood or plasma, its presence in multiple diseases and its potential role as a biomarker to follow disease progression and/or the treatment response. In contrast to sPD-L1 generated by different classes of proteases and by alternative splicing, sTIM-3 is uniquely produced upon ADAM-dependent shedding, providing a more homogenous molecular entity and a possibly more reliable molecular marker. However, the biological functionality of sTIM-3 remains insufficiently characterized. The review shed light on pathologies associated with an altered expression of sTIM-3 in human plasma and the possibility to use sTIM-3 as a diagnostic or therapeutic marker.

Association of PD-L1 gene polymorphisms and circulating sPD-L1 levels with HBV infection susceptibility and related liver disease progression

Soluble molecules of programmed death ligand 1 (sPD-L1) are known to modulate T-cell depletion, an important mechanism of hepatitis B virus (HBV) persistence and liver disease progression. In addition, PD-L1 polymorphisms in the 3'-UTR can influence PD-L1 expression and have been associated with cancer risk, although not definitively. The purpose of this study was to investigate the association of PD-L1 polymorphisms and circulating levels of sPD-L1 in HBV infection and live disease progression. In this study, five hundred fifty-one HBV infected patients of the three clinically well-defined subgroups chronic hepatitis B (CHB, n = 186), liver cirrhosis (LC, n = 142) and hepatocellular carcinoma (HCC, n = 223) and 240 healthy individuals (HC) were enrolled. PD-L1 polymorphisms (rs2297136 and rs4143815) were genotyped by in-house validated ARMS assays. Logistic regression models were applied in order to determine the association of PD-L1 polymorphisms with HBV infection as well as with progression of related liver diseases. Plasma sPD-L1 levels were quantified by ELISA assays. The PD-L1 rs2297136 AA genotype was associated with HBV infection susceptibility (HBV vs. HC: OR = 1.6; 95%CI = 1.1-2.3; p = 0.0087) and disease progression (LC vs. CHB: OR = 1.8; 95%CI = 1.1-2.9; p = 0.018). Whereas, the rs2297136 GG genotype was a protective factor for HCC development. Plasma sPD-L1 levels were significantly high in HBV patients (p < 0.0001) and higher in the LC followed by CHB and HCC groups. High sPD-L1 levels correlated with increased liver enzymes and with advanced liver disease progression (Child-pugh C > B > A, p < 0.0001) and BCLC classification (BCLC D > C > B > A, p = 0.031). We could, for the first time, conclude that PD-L1 rs2297136 polymorphism and plasma sPD-L1 protein levels associate with HBV infection and HBV-related liver disease progression.

New Insights into the Role of PD-1 and Its Ligands in Allergic Disease

Programmed cell death 1 (PD-1) and its ligands PD-L1 and PD-L2 are receptors that act in co-stimulatory and coinhibitory immune responses. Signaling the PD-1/PD-L1 or PD-L2 pathway is essential to regulate the inflammatory responses to infections, autoimmunity, and allergies, and it has been extensively studied in cancer. Allergic diseases include asthma, rhinoconjunctivitis, atopic dermatitis, drug allergy, and anaphylaxis. These overactive immune responses involve IgE-dependent activation and increased CD4+ T helper type 2 (Th2) lymphocytes. Recent studies have shown that PD-L1 and PD-L2 act to regulate T-cell activation and function. However, the main role of PD-1 and its ligands is to balance the immune response; however, the inflammatory process of allergic diseases is poorly understood. These immune checkpoint molecules can function as a brake or a kick-start to regulate the adaptive immune response. These findings suggest that PD-1 and its ligands may be a key factor in studying the exaggerated response in hypersensitivity reactions in allergies. This review summarizes the current understanding of the role of PD-1 and PD-L1 and PD-L2 pathway regulation in allergic diseases and how this immunomodulatory pathway is currently being targeted to develop novel therapeutic immunotherapy.

Successful management of severe bronchial asthma exacerbated by anti-PD-L1 treatment: A report of two cases

Immune checkpoint inhibitors (ICIs) have been used for various carcinomas. However, immune-related adverse events have been observed. There have been few reports of treatment with biologics for severe bronchial asthma induced by ICI; therefore, their efficacy is unknown. We report two cases of severe bronchial asthma requiring systemic steroid administration while using anti-programmed death-ligand 1 (PD-L1) antibody for advanced non-small-cell lung cancer. The anti-interleukin-5 antibody, mepolizumab, was introduced, resulting in the discontinuation of systemic prednisolone and good asthma control. These reports suggest that treatment with biologics may be effective in severe cases of poorly controlled bronchial asthma during ICI therapy.

Adiponectin and Asthma: Knowns, Unknowns and Controversies

Adiponectin is an adipokine associated with the healthy obese phenotype. Adiponectin increases insulin sensitivity and has cardio and vascular protection actions. Studies related to adiponectin, a modulator of the innate and acquired immunity response, have suggested a role of this molecule in asthma. Studies based on various asthma animal models and on the key cells involved in the allergic response have provided important insights about this relation. Some of them indicated protection and others reversed the balance towards negative effects. Many of them described the cellular pathways activated by adiponectin, which are potentially beneficial for asthma prevention or for reduction in the risk of exacerbations. However, conclusive proofs about their efficiency still need to be provided. In this article, we will, briefly, present the general actions of adiponectin and the epidemiological studies supporting the relation with asthma. The main focus of the current review is on the mechanisms of adiponectin and the impact on the pathobiology of asthma. From this perspective, we will provide arguments for and against the positive influence of this molecule in asthma, also indicating the controversies and sketching out the potential directions of research to complete the picture.

PD-L1 in Systemic Immunity: Unraveling Its Contribution to PD-1/PD-L1 Blockade Immunotherapy

The use of monoclonal antibodies targeting PD-1/PD-L1 axis completely changed anticancer treatment strategies. However, despite the significant improvement in overall survival and progression-free survival of patients undergoing these immunotherapy treatments, the only clinically accepted biomarker with some prediction capabilities for the outcome of the treatment is PD-L1 expression in tumor biopsies. Nevertheless, even when having PD-L1-positive tumors, numerous patients do not respond to these treatments. Considering the high cost of these therapies and the risk of immune-related adverse events during therapy, it is necessary to identify additional biomarkers that would facilitate stratifying patients in potential responders and non-responders before the start of immunotherapies. Here, we review the utility of PD-L1 expression not only in tumor cells but in immune system cells and their influence on the antitumor activity of immune cell subsets.

The blockade of PD-1/PD-L1 pathway promotes the apoptosis of CD19+ CD25+ Bregs and suppresses the secretion of IL-10 in patients with allergic rhinitis

PD-1/PD-L1 pathway is crucial to immune regulation by controlling the balance between T cell tolerance and activation. However, the association between PD-1/PD-L1 pathway and regulatory B cells has not been fully investigated in allergic rhinitis. In this study, we detected the number of peripheral CD19⁺ CD25⁺ Bregs and the expression of IL-10 on this cell subset in healthy control and patients with allergic rhinitis using flow cytometry. Then, we evaluated the level of PD-L1 in CD19⁺ CD25⁺ Bregs and investigated the correlation between PD-L1 and CD4⁺ follicular T helper cells. Finally, we studied the effects of anti-PD-L1 on the apoptosis of Bregs and the production of IL-10. Comparing with healthy controls, the percentage of CD19⁺ CD25⁺ Bregs and the expression of IL-10 were both significantly decreased in AR group. In addition, the expression of PD-L1 on CD19⁺ CD25⁺ Bregs was also lower in allergic rhinitis patients. Interestingly, a negative correlation was found between the expression of PD-L1⁺ Bregs and CD4⁺ CXCR5⁺ follicular T helper cells. In vitro assay revealed that anti-PD-L1 promoted Bregs apoptosis and inhibited the expression of IL-10 in CD19⁺ CD25⁺ Bregs. Collectively, these results suggest that PD-L1 expressed on CD19⁺ CD25⁺ Bregs may be a potential regulator in the treatment of allergic rhinitis. Blockade of PD-1/PD-L1 pathway might be a valuable pathogenic target for allergic rhinitis through inhibiting the secretion of immunosuppressive cytokine and promoting CD19⁺ CD25⁺ Bregs apoptosis.

Liquid biopsy in the era of immuno-oncology: is it ready for prime-time use for cancer patients?

The emergence of immunotherapy in oncology requires the discovery, validation and subsequent adoption of robust, sensitive and specific predictive and prognostic biomarkers for daily practice. Until now, anti-PD-L1 immunohistochemistry (IHC) on tissue sections has been the only validated companion diagnostic test for first-line immunotherapy for advanced and metastatic cancer, notably non-small-cell lung cancer (NSCLC). However, detection of this biomarker presents limitations that have stimulated the development of other biomarkers and other approaches. Within this context, the use of a liquid biopsy (LB) could provide an important complementary or alternative added value to PD-L1 IHC. In this review, we discuss how LBs have been used in the field of immuno-oncology (I-O) to predict response, relapse or adverse advents for patients undergoing immune-checkpoint inhibitor (ICI) therapy (anti-PD-1/PD-L1 and CTLA-4) and we highlight recent developments. Circulating tumor cells (CTCs), cell-free DNA (cfDNA), proteins and cytokines detected in plasma as well as circulating T-lymphocytes are discussed as potential sources for developing new I-O biomarkers. The quantification of cfDNA as a predictive biomarker, as well as its sequencing for the determination of tumor mutational burden, is already well advanced. Additionally, the quantification of PD-L1 from CTCs, bound on exosomes or free in plasma, as well as the determination of cytokines, are also being actively investigated with promising results having recently been published. Lastly, analysis of T-lymphocytes, especially by analyzing the T-cell receptor, has recently emerged as a valuable biomarker that might become relevant for the prediction of response to ICIs. While LBs have not yet been implemented in routine I-O clinical practice, recent promising data and rapidly advancing technologies indicate that this approach has the potential to soon personalize the clinical management of cancer patients receiving ICIs.

The relationship between B7 homologous 1 with interleukin-4, interleukin-17 and interferon gamma in patients with allergic rhinitis

Background: The etiology of allergic rhinitis includes an increase in cytokine levels, including IL- 4, IL-13, IL-17, and reduction in B7 homologous 1 (B7-H1) or programmed cell death-1 ligand-1 (PD-L1), a new member of the CD28: B7 stimulant molecule family. The aim of this study was to determine the relationship between cytokines and PD-L1. Methods: In this experimental study, 80 patients with allergic rhinitis were enrolled according to inclusion and exclusion criteria. The severity and stage of the disease were determined by a specialist physician. A 5 cc venous blood sample was collected from the patients. IL-4, IL-17, INFγ and PD-L1 were measured using ELISA technique. Results: There was a significant correlation between SPD-L1 and INFγ, IL-4 and IL-17 in allergic rhinitis patients (P < 0.05). Statistical analysis based on the severity of the disease (Mild, Moderate and Severe) showed a significant positive correlation between the SPD-L1 and INFγ in all three levels (P < 0.001). There was also a significant negative correlation between SPD-L1 and two cytokines IL-4 and IL-17 (P < 0.001). Conclusion: PD-L1 may have a protective role against allergic rhinitis, although the precise mechanism requires further detailed studies.

Soluble immune checkpoints in cancer: production, function and biological significance

Immune checkpoints play important roles in immune regulation, and blocking immune checkpoints on the cell membrane is a promising strategy in the treatment of cancer. Based on this, monoclonal antibodies are having much rapid development, such as those against CTLA-4 (cytotoxic T lymphocyte antigen 4) and PD-1 (programmed cell death protein 1).But the cost of preparation of monoclonal antibodies is too high and the therapeutic effect is still under restrictions. Recently, a series of soluble immune checkpoints have been found such as sCTLA-4 (soluble CTLA-4) and sPD-1 (soluble PD-1). They are functional parts of membrane immune checkpoints produced in different ways and can be secreted by immune cells. Moreover, these soluble checkpoints can diffuse in the serum. Much evidence has demonstrated that these soluble checkpoints are involved in positive or negative immune regulation and that changes in their plasma levels affect the development, prognosis and treatment of cancer. Since they are endogenous molecules, they will not induce immunological rejection in human beings, which might make up for the deficiencies of monoclonal antibodies and enhance the utility value of these molecules. Therefore, there is an increasing need for investigating novel soluble checkpoints and their functions, and it is promising to develop relevant therapies in the future. In this review, we describe the production mechanisms and functions of various soluble immune checkpoint receptors and ligands and discuss their biological significance in regard to biomarkers, potential candidate drugs, therapeutic targets, and other topics.