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

Bacterial sepsis causes more dramatic pathogenetic changes in the Th1 pathway than does viral (COVID-19) sepsis: a prospective observational study of whole blood transcriptomes

OBJECTIVES

This study aimed to comprehensively compare host responses of patients with bacterial sepsis and those with viral (COVID-19) sepsis by analyzing messenger RNA (mRNA) and microRNA (miRNA) profiles to shed light on their distinct pathophysiological mechanisms.

DESIGN

Prospective observational study.

SETTING

Whole blood RNA sequencing was used to analyze mRNA and miRNA profiles of patients diagnosed as having bacterial sepsis or viral (COVID-19) sepsis at the Department of Trauma and Emergency Medicine, Osaka University Graduate School of Medicine.

PATIENTS

Twenty-two bacterial sepsis patients, 35 viral (COVID-19) sepsis patients, and 15 healthy subjects admitted to the department were included. We diagnosed bacterial sepsis patients according to the sepsis-3 criterion that the Sequential Organ Failure Assessment score must increase to 2 points or more among patients with suspected infections. Viral (COVID-19) sepsis patients were diagnosed using SARS-CoV-2 RT-PCR testing, and presence of pneumonia was assessed through chest computed tomography scans.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

For RNA sequencing, 14,500 mRNAs, 1121 miRNAs, and 2556 miRNA-targeted mRNAs were available for analysis in the bacterial sepsis patients. Numbers of genes showing upregulated: downregulated gene expression (false discovery rate < 0.05, |log2 fold change| > 1.5) were 256:2887 for mRNA, 53:5 for miRNA, and 49:2507 for miRNA-targeted mRNA. Similarly, in viral (COVID-19) sepsis patients, 14,500 mRNAs, 1121 miRNAs, and 327 miRNA-targeted mRNAs were analyzed, with numbers of genes exhibiting upregulated: downregulated gene expression of 672:1147 for mRNA, 3:4 for miRNA, and 165:162 for miRNA-targeted mRNA. This analysis revealed significant differences in the numbers of upregulated and downregulated genes expressed and pathways between the bacterial sepsis and viral (COVID-19) sepsis patients. Bacterial sepsis patients showed activation of the PD-1 and PD-L1 cancer immunotherapy signaling pathway and concurrent suppression of Th1 signaling.

CONCLUSION

Our study illuminated distinct molecular variances between bacterial sepsis and viral (COVID-19) sepsis. Bacterial sepsis patients had a greater number of upregulated and downregulated genes and pathways compared to viral (COVID-19) sepsis patients. Especially, bacterial sepsis caused more dramatic pathogenetic changes in the Th1 pathway than did viral (COVID-19) sepsis.

CAR-NKT Cells in Asthma: Use of NKT as a Promising Cell for CAR Therapy

NKT cells, unique lymphocytes bridging innate and adaptive immunity, offer significant potential for managing inflammatory disorders like asthma. Activating iNKT induces increasing IFN-γ, TGF-β, IL-2, and IL-10 potentially suppressing allergic asthma. However, their immunomodulatory effects, including granzyme-perforin-mediated cytotoxicity, and expression of TIM-3 and TRAIL warrant careful consideration and targeted approaches. Although CAR-T cell therapy has achieved remarkable success in treating certain cancers, its limitations necessitate exploring alternative approaches. In this context, CAR-NKT cells emerge as a promising approach for overcoming these challenges, potentially achieving safer and more effective immunotherapies. Strategies involve targeting distinct IgE-receptors and their interactions with CAR-NKT cells, potentially disrupting allergen-mast cell/basophil interactions and preventing inflammatory cytokine release. Additionally, targeting immune checkpoints like PDL-2, inducible ICOS, FASL, CTLA-4, and CD137 or dectin-1 for fungal asthma could further modulate immune responses. Furthermore, artificial intelligence and machine learning hold immense promise for revolutionizing NKT cell-based asthma therapy. AI can optimize CAR-NKT cell functionalities, design personalized treatment strategies, and unlock a future of precise and effective care. This review discusses various approaches to enhancing CAR-NKT cell efficacy and longevity, along with the challenges and opportunities they present in the treatment of allergic asthma.

The Exploitation of the Glycosylation Pattern in Asthma: How We Alter Ancestral Pathways to Develop New Treatments

Asthma has reached epidemic levels, yet progress in developing specific therapies is slow. One of the main reasons for this is the fact that asthma is an umbrella term for various distinct subsets. Due to its high heterogeneity, it is difficult to establish biomarkers for each subset of asthma and to propose endotype-specific treatments. This review focuses on protein glycosylation as a process activated in asthma and ways to utilize it to develop novel biomarkers and treatments. We discuss known and relevant glycoproteins whose functions control disease development. The key role of glycoproteins in processes integral to asthma, such as inflammation, tissue remodeling, and repair, justifies our interest and research in the field of glycobiology. Altering the glycosylation states of proteins contributing to asthma can change the pathological processes that we previously failed to inhibit. Special emphasis is placed on chitotriosidase 1 (CHIT1), an enzyme capable of modifying LacNAc- and LacdiNAc-containing glycans. The expression and activity of CHIT1 are induced in human diseased lungs, and its pathological role has been demonstrated by both genetic and pharmacological approaches. We propose that studying the glycosylation pattern and enzymes involved in glycosylation in asthma can help in patient stratification and in developing personalized treatment.

Haplotype function score improves biological interpretation and cross-ancestry polygenic prediction of human complex traits

We propose a new framework for human genetic association studies: at each locus, a deep learning model (in this study, Sei) is used to calculate the functional genomic activity score for two haplotypes per individual. This score, defined as the Haplotype Function Score (HFS), replaces the original genotype in association studies. Applying the HFS framework to 14 complex traits in the UK Biobank, we identified 3619 independent HFS-trait associations with a significance of p < 5 × 10-8. Fine-mapping revealed 2699 causal associations, corresponding to a median increase of 63 causal findings per trait compared with single-nucleotide polymorphism (SNP)-based analysis. HFS-based enrichment analysis uncovered 727 pathway-trait associations and 153 tissue-trait associations with strong biological interpretability, including 'circadian pathway-chronotype' and 'arachidonic acid-intelligence'. Lastly, we applied least absolute shrinkage and selection operator (LASSO) regression to integrate HFS prediction score with SNP-based polygenic risk scores, which showed an improvement of 16.1-39.8% in cross-ancestry polygenic prediction. We concluded that HFS is a promising strategy for understanding the genetic basis of human complex traits.

Mononuclear cell composition and activation in blood and mucosal tissue of eosinophilic esophagitis

Introduction

Eosinophilic esophagitis (EoE) is a chronic, inflammatory, antigen-driven disease of the esophagus. Tissue EoE pathology has previously been extensively characterized by novel transcriptomics and proteomic platforms, however the majority of surface marker determination and screening has been performed in blood due to mucosal tissue size limitations. While eosinophils, CD4+ T cells, mast cells and natural killer (NK) T cells were previously investigated in the context of EoE, an accurate picture of the composition of peripheral blood mononuclear cells (PBMC) and their activation is missing.

Methods

In this study, we aimed to comprehensively analyze the composition of peripheral blood mononuclear cells and their activation using surface marker measurements with multicolor flow cytometry simultaneously in both blood and mucosal tissue of patients with active EoE, inactive EoE, patients with gastroesophageal reflux disease (GERD) and controls. Moreover, we set out to validate our data in co-cultures of PBMC with human primary esophageal epithelial cells and in a novel inducible mouse model of eosinophilic esophagitis, characterized by extensive IL-33 secretion in the esophagus.

Results

Our results indicate that specific PBMC populations are enriched, and that they alter their surface expression of activation markers in mucosal tissue of active EoE. In particular, we observed upregulation of the immunomodulatory molecule CD38 on CD4+ T cells and on myeloid cells in biopsies of active EoE. Moreover, we observed significant upregulation of PD-1 on CD4+ and myeloid cells, which was even more prominent after corticosteroid treatment. With co-culture experiments we could demonstrate that direct cell contact is needed for PD-1 upregulation on CD4+ T cells. Finally, we validated our findings of PD-1 and CD38 upregulation in an inducible mouse model of EoE.

Discussion

Herein we show significant alterations in the PBMC activation profile of patients with active EoE in comparison to inactive EoE, GERD and controls, which could have potential implications for treatment. To our knowledge, this study is the first of its kind expanding the multi-color flow cytometry approach in different patient groups using in vitro and in vivo translational models.

Evaluation of PD-1 T lymphocytes in bronchoalveolar lavage in lung cancer compared to benign lung diseases

The expression of the programmed cell death protein 1 (PD-1) has been shown to be markedly increased in tumor-infiltrating lymphocytes. However, the proportion of PD-1 + T cells in the bronchoalveolar lavage (BAL) of lung cancer patients has not been sufficiently evaluated so far. In this prospective study, the proportion of PD-1 + CD4 + as well as PD-1 + CD8 + T cells in BAL samples, isolated from patients with lung cancer, asthma or interstitial lung disease (ILD), were determined via flow cytometry and compared for differences. Bronchoalveolar lavage was performed in 34 patients (14 patients with lung cancer, 10 patients with asthma, 10 patients with ILD). The highest median proportion of PD-1 + CD4 + or PD-1 + CD8 + T cells were found in patients with ILD (83.1% [IQR 72.1; 87.5] and 73.8% [IQR 60.3; 86.3]) followed by patients with lung cancer (66.4% [IQR 59; 69] and 77.1% [IQR 35.8; 82.3]) and patients with asthma (61.3% [IQR 57.4; 70.5] and 57.3% [IQR 46; 65]). Thereby, the difference in the proportion of PD-1 + CD3 + CD4 + BAL cells between ILD patients and asthmatics was significantly different (p = 0.04). The proportion of PD-1 + CD4 + and PD-1 + CD8 + T cells in the BAL of patients with lung cancer did not differ significantly to patients with benign lung diseases. The highest proportion was observed in ILD patients suggesting further research to evaluate the role of the PD-1/PD-L1 pathway in ILD patients.

Recent advances in epicutaneous immunotherapy and potential applications in food allergy

Given the potent immunological properties of the skin, epicutaneous immunotherapy (EPIT) emerges as a promising treatment approach for inducing immune tolerance, particularly for food allergies. Targeting the highly immunocompetent, non-vascularized epidermis allows for the application of microgram amounts of allergen while significantly reducing the risk of allergen passage into the bloodstream, thus limiting systemic allergen exposure and distribution. This makes EPIT highly suitable for the treatment of potentially life-threatening allergies such as food allergies. Multiple approaches to EPIT are currently under investigation for the treatment of food allergy, and these include the use of allergen-coated microneedles, application of allergen on the skin pretreated by tape stripping, abrasion or laser-mediated microperforation, or the application of allergen on the intact skin using an occlusive epicutaneous system. To date, the most clinically advanced approach to EPIT is the Viaskin technology platform. Viaskin is an occlusive epicutaneous system (patch) containing dried native allergen extracts, without adjuvants, which relies on frequent application for the progressive passage of small amounts of allergen to the epidermis through occlusion of the intact skin. Numerous preclinical studies of Viaskin have demonstrated that this particular approach to EPIT can induce potent and long-lasting T-regulatory cells with broad homing capabilities, which can exert their suppressive effects in multiple organs and ameliorate immune responses from different routes of allergen exposure. Clinical trials of the Viaskin patch have studied the efficacy and safety for the treatment of life-threatening allergies in younger patients, at an age when allergic diseases start to occur. Moreover, this treatment approach is designed to provide a non-invasive therapy with no restrictions on daily activities. Taken together, the preclinical and clinical data on the use of EPIT support the continued investigation of this therapeutic approach to provide improved treatment options for patients with allergic disorders in the near future.

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.

T cell co-stimulatory and co-inhibitory pathways in atopic dermatitis

The use of immune checkpoint inhibitors (ICIs) targeting the T cell inhibitory pathways has revolutionized cancer treatment. However, ICIs might induce progressive atopic dermatitis (AD) by affecting T cell reactivation. The critical role of T cells in AD pathogenesis is widely known. T cell co-signaling pathways regulate T cell activation, where co-signaling molecules are essential for determining the magnitude of the T cell response to antigens. Given the increasing use of ICIs in cancer treatment, a timely overview of the role of T cell co-signaling molecules in AD is required. In this review, we emphasize the importance of these molecules involved in AD pathogenesis. We also discuss the potential of targeting T cell co-signaling pathways to treat AD and present the unresolved issues and existing limitations. A better understanding of the T cell co-signaling pathways would aid investigation of the mechanism, prognosis evaluation, and treatment of AD.

Oral pretreatment with β-lactoglobulin derived peptide and CpG co-encapsulated in PLGA nanoparticles prior to sensitizations attenuates cow's milk allergy development in mice

Cow's milk allergy is a common food allergy among infants. Improved hygiene conditions and loss of microbial diversity are associated with increased risk of allergy development. The intestinal immune system is essential for oral tolerance induction. In this respect, bacterial CpG DNA is known to drive Th1 and regulatory T-cell (Treg) development via Toll-Like-Receptor 9 (TLR-9) signaling, skewing away from the allergic Th2 phenotype. We aimed to induce allergen specific tolerance via oral delivery of poly (lactic-co-glycolic acid) nanoparticles (NP) co-encapsulated with a selected β-lactoglobulin derived peptide (BLG-Pep) and TLR-9 ligand CpG oligodeoxynucleotide (CpG). In vivo, 3-4-week-old female C3H/HeOuJ mice housed in individually ventilated cages received 6-consecutive-daily gavages of either PBS, whey, BLG-Pep/NP, CpG/NP, a mixture of BLG-Pep/NP plus CpG/NP or co-encapsulated BLG-Pep+CpG/NP, before 5-weekly oral sensitizations with whey plus cholera toxin (CT) or only CT (sham) and were challenged with whey 5 days after the last sensitization. The co-encapsulated BLG-Pep+CpG/NP pretreatment, but not BLG-Pep/NP, CpG/NP or the mixture of BLG-Pep/NP plus CpG/NP, prevented the whey-induced allergic skin reactivity and prevented rise in serum BLG-specific IgE compared to whey-sensitized mice. Importantly, co-encapsulated BLG-Pep+CpG/NP pretreatment reduced dendritic cell (DC) activation and lowered the frequencies of PD-L1+ DC in the mesenteric lymph nodes compared to whey-sensitized mice. By contrast, co-encapsulated BLG-Pep+CpG/NP pretreatment increased the frequency of splenic PD-L1+ DC compared to the BLG-Pep/NP plus CpG/NP recipients, in association with lower Th2 development and increased Treg/Th2 and Th1/Th2 ratios in the spleen. Oral administration of PLGA NP co-encapsulated with BLG-Pep and CpG prevented rise in serum BLG-specific IgE and symptom development while lowering splenic Th2 cell frequency in these mice which were kept under strict hygienic conditions.

Immune checkpoint molecules in prevention and development of asthma

Allergic asthma is a respiratory disease initiated by type-2 immune responses characterized by secretion of alarmins, interleukin-4 (IL-4), IL-5, and IL-13, eosinophilic inflammation, and airway hyperresponsiveness (AHR). Immune checkpoints (ICPs) are inhibitory or stimulatory molecules expressed on different immune cells, tumor cells, or other cell types that regulate immune system activation and maintain immune homeostasis. Compelling evidence indicates a key role for ICPs in both the progression and prevention of asthma. There is also evidence of asthma development or exacerbation in some cancer patients receiving ICP therapy. The aim of this review is to provide an updated overview of ICPs and their roles in asthma pathogenesis, and to assess their implications as therapeutic targets in asthma.

Revisiting PD-1/PD-L pathway in T and B cell response: Beyond immunosuppression

The regulation of T cell response depends on co-inhibitory pathways that serve to control immune-mediated tissue damage and resolve inflammation by modulating the magnitude and duration of immune response. In this process, the axis of T-cell-expressed programmed death-1 (PD-1) and its ligands (PD-L1 and PD-L2) play a key role. While the PD-1/PD-L pathway has received considerable attention for its role in the maintenance of T cell exhaustion in cancer and chronic infection, the PD-1/PD-L pathway also plays diverse roles in regulating host immunity beyond T cell exhaustion. In this review, we will discuss emerging concepts in co-stimulatory functions of PD-1/PD-L pathway on T cell- and B cell response and explore the potential underlying mechanisms. In addition, based on the elevated expression of PD-1 and its ligands in local inflamed tissues, we further discussed the role of PD-1/PD-L pathway in autoimmune diseases.

Short-Chain Fatty Acids Augment Differentiation and Function of Human Induced Regulatory T Cells

Regulatory T cells (Tregs) control immune system activity and inhibit inflammation. While, in mice, short-chain fatty acids (SCFAs) are known to be essential regulators of naturally occurring and in vitro induced Tregs (iTregs), data on their contribution to the development of human iTregs are sparse, with no reports of the successful SCFAs-augmented in vitro generation of fully functional human iTregs. Likewise, markers undoubtedly defining human iTregs are missing. Here, we aimed to generate fully functional human iTregs in vitro using protocols involving SCFAs and to characterize the underlying mechanism. Our target was to identify the potential phenotypic markers best characterizing human iTregs. Naïve non-Treg CD4⁺ cells were isolated from the peripheral blood of 13 healthy adults and cord blood of 12 healthy term newborns. Cells were subjected to differentiation toward iTregs using a transforming growth factor β (TGF-β)-based protocol, with or without SCFAs (acetate, butyrate, or propionate). Thereafter, they were subjected to flow cytometric phenotyping or a suppression assay. During differentiation, cells were collected for chromatin-immunoprecipitation (ChIP)-based analysis of histone acetylation. The enrichment of the TGF-β-based protocol with butyrate or propionate potentiated the in vitro differentiation of human naïve CD4⁺ non-Tregs towards iTregs and augmented the suppressive capacity of the latter. These seemed to be at least partly underlain by the effects of SCFAs on the histone acetylation levels in differentiating cells. GITR, ICOS, CD39, PD-1, and PD-L1 were proven to be potential markers of human iTregs. Our results might boost the further development of Treg-based therapies against autoimmune, allergic and other chronic inflammatory disorders.