Allergen-specific immunotherapy induces the suppressive secretoglobin 1A1 in cells of the lower airways

Clara cell 10 (CC10) protein attenuates allergic airway inflammation by modulating lung dendritic cell functions

Allergic asthma is a complex inflammatory disorder predominantly orchestrated by T helper 2 (Th2) lymphocytes. The anti-inflammatory protein Clara Cell 10-kDa (CC10), also known as secretoglobin family 1A member 1 (SCGB1A1), shows promise in modulating respiratory diseases. However, its precise role in asthma remains unclear. This study examines the potential of CC10 to suppress allergic asthma inflammation, specifically assessing its regulatory effects on Th2 cell responses and dendritic cells (DCs). Lower CC10 levels in asthma were observed and correlated with increased IgE and lymphocytes. Cc10-/- mice exhibited exacerbated allergic airway inflammation marked by increased inflammatory cell infiltration, Th2 cytokines, serum antigen-specific IgE levels, and airway hyperresponsiveness (AHR) in house dust mite (HDM)-induced models. Conversely, recombinant CC10 significantly attenuated these inflammatory responses. Intriguingly, CC10 did not directly inhibit Th cell activation but significantly downregulated the population of CD11b+CD103- DCs subsets in lungs of asthmatic mice and modulated the immune activation functions of DCs through NF-κB signaling pathway. The mixed lymphocyte response assay revealed that DCs mediated the suppressive effect of CC10 on Th2 cell responses. Collectively, CC10 profoundly mitigates Th2-type allergic inflammation in asthma by modulating lung DC phenotype and functions, highlighting its therapeutic potential for inflammatory airway conditions and other related immunological disorders.

Role of sulfatide-reactive vNKT cells in promoting lung Treg cells via dendritic cell modulation in asthma models

Our previous studies have showed that sulfatide-reactive type II NKT (i.e. variant NKT, vNKT) cells inhibit the immunogenic maturation during the development of mature lung dendritic cells (LDCs), leading todeclined allergic airway inflammation in asthma. Nonetheless, the specific immunoregulatory roles of vNKT cells in LDC-mediated Th2 cell responses remain incompletely understood. Herein, we found that administration of sulfatide facilitated the generation of CD4+FoxP3+ regulatory T (Treg) cells in the lungs of wild-type mice, but not in CD1d-/- and Jα18-/- mice, after ovalbumin or house dust mite exposure. This finding implies that the enhancement of lung Treg cells by sulfatide requires vNKT cells, which dependent on invariant NKT (iNKT) cells. Furthermore, the CD4+FoxP3+ Treg cells induced by sulfatide-reactive vNKT cells were found to be associated with PD-L1 molecules expressed on LDCs, and this association was dependent on iNKT cells. Collectively, our findings suggest that in asthma-mimicking murine models, sulfatide-reactive vNKT cells facilitate the generation of lung Treg cells through inducing tolerogenic properties in LDCs, and this process is dependent on the presence of lung iNKT cells. These results may provide a potential therapeutic approach to treat allergic asthma.

Allergen immunotherapy combined with Notch pathway inhibitors improves HDM-induced allergic airway inflammation and inhibits ILC2 activation

Introduction

Group 2 innate lymphoid cells (ILC2s) play a crucial role in house dust mite (HDM)-induced allergic inflammation, and allergen immunotherapy (AIT) holds promise for treating the disease by reducing the frequency of ILC2s. Despite significant progress in AIT for allergic diseases, there remains a need to improve the control of allergic symptoms.

Methods

We investigated the synergistic effect of the Notch signaling pathway and subcutaneous immunotherapy (SCIT) in treating allergic airway inflammation in mice and their impact on the ratio of ILC2s in lung tissues. This was achieved by establishing the HDM-induced airway allergic disorders (HAAD) model and SCIT model. Additionally, we conducted in vitro investigations into the effect of the Notch signaling pathway on the secretory function of activated ILC2s using fluorescence-activated cell sorting. Furthermore, we explored the coactivation of the Notch signaling pathway with SCIT in vitro by sorting ILC2s from the lung tissues of mice after SCIT modeling.

Results

Previously, our group demonstrated that Notch signaling pathway inhibitors can reduce allergic airway inflammation in mice. Notch signaling induces lineage plasticity of mature ILC2s. In this study, we showed that AIT alleviates allergic airway inflammation and suppresses the frequency of ILC2s induced by HDM. Interestingly, AIT combined with a γ-secretase inhibitor (GSI), an inhibitor of the Notch signaling pathway, significantly inhibited the frequency of ILC2s, reduced airway inflammation, and suppressed Th2-type responses in a mouse model. Furthermore, lung ILC2s from HDM-challenged mice with or without AIT were treated with GSI in vitro, and we found that GSI dramatically reduced the secretion of type 2 inflammatory factors in ILC2s.

Discussion

These findings suggest that Notch signaling pathway inhibitors can be used as adjuvant therapy for AIT and may hold potential treatment value in the cooperative control of allergic airway inflammation during early AIT.

Probiotic Lactobacillus plantarum GUANKE effectively alleviates allergic rhinitis symptoms by modulating functions of various cytokines and chemokines

Background

Currently, the prevalence of allergic rhinitis (AR) remains high and there is a great need to develop better and safer ways to alleviate AR symptoms. The Lactobacillus plantarum GUANKE probiotic was reported as an immunomodulator through maintaining Th1/Th2 balance. This study aimed to determine the efficacy of GUANKE in AR subjects.

Methods

Adults aged from 18 to 60 years old and previously suffered from AR were recruited and received GUANKE probiotics treatment for 4 weeks. The questionnaires of Total nasal symptom scores (TNSS), total non-nasal symptom score (TNNSS), and rhinitis control assessment test (RCAT) were used to assess the effectiveness before and after treatment. The serum allergen-specific IgE and cytokines were also determined at baseline and after 4 weeks of probiotics administration.

Results

The results showed that TNSS and TNNSS were significantly reduced and the RCAT score was significantly increased compared to baseline. The sub-symptom score of rhinorrhea, itching, sneezing, and tearing in each questionnaire also showed significant changes, and the serum IgE level was markedly decreased. We further measured inflammatory-related proteins in serum and found that a total of 20 proteins (6 upregulated and 14 downregulated) were significantly changed compared to baseline, including IL-4, IL-7, IL-20, IL-33, CXCL1, CXCL5, CXCL6, CXCL11, CCL4, CCL23, TGF-alpha, LAP-TGF-beta-1, MMP-1, MMP-10, AXIN1, NT-3, OSM, SCF, CD6, and NRTN. Enrichment analysis showed that these significantly altered proteins were mainly enriched in cytokine and chemokine-related signaling pathways.

Conclusion

Taken together, this study demonstrated the Lactobacillus plantarum GUANKE can serve as an effective immunobiotic for the treatment of AR, which is realized through maintaining the Th1/Th2 balance by modulating the functions of various cytokines and chemokines.

Proinflammatory pattern in the lower airways of non-asthmatic obese adolescents

BACKGROUND

Obesity is known to be a pro-inflammatory condition affecting multiple organs. Obesity as a systemic pro-inflammatory state, might be associated with bronchial inflammation in non-smoking adolescents with a BMI ≥ 30 kg/m2 without evidence of concomitant chronic diseases.

MATERIALS AND METHODS

We studied non-asthmatic obese patients (n = 20; median age 15.8 years; BMI 35.0 kg/m2) compared to age matched healthy control subjects (n = 20; median age 17.5 years; BMI 21.5 kg/m2). Induced sputum differential cell counts and sputum mRNA levels were assessed for all study subjects. Serum levels of CRP, IL-6, and IL-8 were measured. Further, IL-5, IL-6, IL-8, IL-13, IL-17, TNF-α, IFN-γ, and IP-10 protein levels were analyzed in induced sputum was.

RESULTS

Serum CRP levels, sputum inflammatory cell load and sputum eosinophils differed significantly between obese and non-obese subjects, for sputum neutrophils, a correlation was shown with BMI ≥ 30 kg/m2. Differences were also observed for sputum mRNA expression of IL6, IL8, IL13, IL17, IL23, and IFN-γ, as well as the transcription factors T-bet, GATA3, and FoxP3.

CONCLUSIONS

Increased bronchial inflammation, triggered by systemic or local inflammatory effects of obesity itself, may account for the higher rates of airway disease in obese adolescents.

A Review on Novel Therapeutic Modalities and Evidence-based Drug Treatments against Allergic Rhinitis

Allergic rhinitis (AR) is an IgE-mediated atopic disease that occurs due to inhaled antigens in the immediate phase. Misdiagnosis, insufficient treatment, or no treatment at all are frequent problems associated with the widespread condition known as chronic allergic rhinitis. AR symptoms include runny, itchy, stuffy, and sneezing noses. Asthma and nasal polyps, for example, sometimes occur simultaneously in patients. In order for people living with AR to be as comfortable and productive as possible, treatment should center on reducing their symptoms. The online sources and literature, such as Pubmed, ScienceDirect, and Medline, were reviewed to gather information regarding therapeutic modalities of AR and evidence-based treatments for the disease as the objectives of the present study. An increasing number of people are suffering from AR, resulting in a heavy financial and medical burden on healthcare systems around the world. Undertreating AR frequently results in a decline in quality of life. Treatment compliance is a critical challenge in the administration of AR. Innovative therapies are needed for RA to provide patients with symptom alleviation that is less expensive, more effective, and longer duration of action. Evidence-based guidelines are helpful for managing AR illness. Treating AR according to evidence-based standards can help in disease management. AR treatment includes allergen avoidance, drug therapy, immunotherapy, patient education, and follow-up. However, AR treatment with intranasal corticosteroids is more popular. Hence, in this review article, treatment options for AR are discussed in depth. We also discussed the incidence, causes, and new treatments for this clinical condition.

T-helper cells and their cytokines in pathogenesis and treatment of asthma

Prosperous advances in understanding the cellular and molecular mechanisms of chronic inflammation and airway remodeling in asthma have been made over the past several decades. Asthma is a chronic inflammatory disease of the airways characterized by reversible airway obstruction that is self-resolving or remits with treatment. Around half of asthma patients are "Type-2-high" asthma with overexpression of type 2 inflammatory pathways and elevated type 2 cytokines. When stimulated by allergens, airway epithelial cells secrete IL-25, IL-33, and TSLP to derive a Th2 immune response. First ILC2 followed by Th2 cells produces a series of cytokines such as IL-4, IL-5, and IL-13. T_FH cells control IgE synthesis by secreting IL-4 to allergen-specific B cells. IL-5 promotes eosinophil inflammation, while IL-13 and IL-4 are involved in goblet cell metaplasia and bronchial hyperresponsiveness. Currently, "Type-2 low" asthma is defined as asthma with low levels of T2 biomarkers due to the lack of reliable biomarkers, which is associated with other Th cells. Th1 and Th17 are capable of producing cytokines that recruit neutrophils, such as IFN-γ and IL-17, to participate in the development of "Type-2-low" asthma. Precision medicine targeting Th cells and related cytokines is essential in the management of asthma aiming at the more appropriate patient selection and better treatment response. In this review, we sort out the pathogenesis of Th cells in asthma and summarize the therapeutic approaches involved as well as potential research directions.

Modulation of innate immunity in airway epithelium for host-directed therapy

Innate immunity of the mucosal surfaces provides the first-line defense from invading pathogens and pollutants conferring protection from the external environment. Innate immune system of the airway epithelium consists of several components including the mucus layer, mucociliary clearance of beating cilia, production of host defense peptides, epithelial barrier integrity provided by tight and adherens junctions, pathogen recognition receptors, receptors for chemokines and cytokines, production of reactive oxygen species, and autophagy. Therefore, multiple components interplay with each other for efficient protection from pathogens that still can subvert host innate immune defenses. Hence, the modulation of innate immune responses with different inducers to boost host endogenous front-line defenses in the lung epithelium to fend off pathogens and to enhance epithelial innate immune responses in the immunocompromised individuals is of interest for host-directed therapy. Herein, we reviewed possibilities of modulation innate immune responses in the airway epithelium for host-directed therapy presenting an alternative approach to standard antibiotics.

Long noncoding RNA antisense noncoding RNA in the INK4 locus inhibition alleviates airway remodeling in asthma through the regulation of the microRNA-7-5p/early growth response factor 3 axis

Asthma, a chronic inflammatory disease of the airways, clinically manifests as airway remodeling. The purpose of this study was to probe the potential role of long noncoding RNA (lncRNA) antisense noncoding RNA in the INK4 locus (lncRNA ANRIL) in the proliferation and migration of airway smooth muscle cell (ASMC) and to explore its potential mechanisms in asthma. Serum samples were obtained from 30 healthy volunteers and 30 patients with asthma. Additionally, platelet-derived growth factor-BB (PDGF-BB) was used to induce airway remodeling in ASMCs. The level of lncRNA ANRIL and microRNA (miR)-7-5p in serum samples were measured by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). TargetScan predicted the binding site of miR-7-5p to early growth response factor 3 (EGR3) and validated the results using a dual-luciferase reporter assay. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and Transwell assays were used to detect cellular proliferation and migration, respectively. Subsequently, changes in proliferation- and migration-related genes were verified using western blot analysis and qRT-PCR. These results indicate that lncRNA ANRIL was upregulated in the serum and PDGF-BB-induced ASMCs of patients with asthma, whereas miR-7-5p expression was reduced. EGR3 was a direct target of miR-7-5p. LncRNA ANRIL silencing inhibited the proliferation or migration of ASMCs induced by PDGF-BB through miR-7-5p upregulation. Mechanistic studies indicated that miR-7-5p inhibits the proliferation or migration of PDGF-BB-induced ASMCs by decreasing EGR3 expression. EGR3 upregulation reverses the role of miR-7-5p in airway remodeling. Thus, downregulation of lncRNA ANRIL inhibits airway remodeling through inhibiting the proliferation and migration of PDGF-BB-induced ASMCs by regulating miR-7-5p/EGR3 signaling.

Club Cell Secretory Protein in Lung Disease: Emerging Concepts and Potential Therapeutics

Club cell secretory protein (CCSP), also known as secretoglobin 1A1 (gene name SCGB1A1), is one of the most abundant proteins in the lung, primarily produced by club cells of the distal airway epithelium. At baseline, CCSP is found in large concentrations in lung fluid specimens and can also be detected in the blood and urine. Obstructive lung diseases are generally associated with reduced CCSP levels, thought to be due to decreased CCSP production or club cell depletion. Conversely, several restrictive lung diseases have been found to have increased CCSP levels both in the lung and in the circulation, likely related to club cell dysregulation as well as increasedlung permeability. Recent studies demonstrate multiple mechanisms by which CCSP dampens acute and chronic lung inflammation. Given these anti-inflammatory effects, CCSP represents a novel potential therapeutic modality in lung disease.

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.

Update on pathomechanisms and treatments in allergic rhinitis

Allergic rhinitis (AR) is a global health problem with increasing prevalence and association with an enormous medical and socioeconomic burden. New recognition of immune cells such as type 2 innate lymphocytes (ILC2s), T helper (Th2) 2 cells, follicular helper T cells, follicular regulatory T cells, regulatory T cells, B cells, dendritic cells, and epithelial cells in AR pathogenesis has been updated in this review paper. An in-depth understanding of the mechanisms underlying AR will aid the identification of biomarkers associated with disease and ultimately provide valuable parameters critical to guide personalized targeted therapy. As the only etiological treatment option for AR, allergen-specific immunotherapy (AIT) has attracted increasing attention, with evidence for effectiveness of AIT recently demonstrated in several randomized controlled trials and long-term real-life studies. The exploration of biologics as therapeutic options has only involved anti-IgE and anti-type 2 inflammatory agents; however, the cost-effectiveness of these agents remains to be elucidated precisely. In the midst of the currently on-going COVID-19 pandemic, a global life-threatening disease, although some studies have indicated that AR is not a risk factor for severity and mortality of COVID-19, this needs to be confirmed in multi-centre, real-life studies of AR patients from different parts of the world.

TAFA4-IL-10 axis potentiate immunotherapy for airway allergy by induction of specific regulatory T cells

Allergen-specific immunotherapy (AIT) is the main treatment for allergic diseases. The therapeutic efficacy of AIT has to be improved. Neuropeptides, such as TAFA4, have immune-regulating features. The objective of this study is to promote the efficacy of AIT in experimental allergic rhinitis (AR) by the concurrent use of TAFA chemokine as a family member 4 (TAFA4). In this study, an AR mouse model was developed using ovalbumin (OVA) as the specific antigen. The AR response was assessed in mice after treatment with AIT or/and TAFA4. We found that exposure to TAFA4 activated dendritic cells (DCs) in the airway tissues. Activation of DC by TAFA4 resulted in the expression of IL-10. TAFA4 also promoted the activities of c-Maf inducing protein. The FPR1-MyD88-AKT signal pathway was associated with the TAFA4-induced Il10 expression in the DCs. Co-administration of AIT/TAFA4 attenuated the AR response in mice by inducing antigen-specific Tr1 cells. In conclusion, TAFA4 induces the expression of IL-10 in DCs. Acting as an adjuvant, TAFA4 significantly improves AIT’s therapeutic efficacy against AR by inducing antigen-specific Tr1 cells.

Endogenous Adenosine 5'-Monophosphate, But Not Acetylcholine or Histamine, is Associated with Asthma Control, Quality of Life, and Exacerbations

OBJECTIVE

Endogenous adenosine 5'-monophosphate (AMP), acetylcholine (ACh), and histamine (HA) are known to be important in bronchial contraction, but their clinical relevance to asthma is poorly understood. We aimed to quantify endogenous AMP, ACh, and HA in induced sputum samples and explore their relationships with asthma control and exacerbations.

METHODS

20 healthy subjects and 112 asthmatics underwent clinical assessment, sputum induction, and blood sampling. The level of asthma control was determined by the asthma control test (ACT) questionnaire. Asthma exacerbation was evaluated according to the criteria of the American Thoracic Society/European Respiratory Society. Levels of AMP, ACh, and HA in sputum were measured by liquid chromatography coupled to tandem mass spectrometry. IL-β, IL-4, IL-5, IL-6, IL-8, IL-13, IL-17A, TNF-α, IFN-γ, and macrophage-derived chemokine (MDC) were also measured.

RESULTS

Compared to healthy controls, asthmatics had higher levels of HA, lower levels of ACh, and similar levels of AMP in induced sputum samples. Compared to controlled asthma (n = 54), uncontrolled asthma (n = 58) showed higher AMP levels (P = 0.002), but similar HA and ACh levels. AMP was negatively correlated with ACT scores (r = - 0.348) and asthma quality of life questionnaire scores (r = - 0.188) and positively correlated with blood monocytes percentage (r = 0.195), sputum MDC (r = 0.214), and IL-6 levels (r = 0.196). Furthermore, AMP was associated with an increased risk of exacerbations in the preceding year.

CONCLUSION

Endogenous AMP, but not ACh or HA, was associated with asthma control, quality of life, and exacerbations in the previous year, which indicates that AMP could be a clinically useful biomarker of asthma.

Role of microRNAs in type 2 diseases and allergen-specific immunotherapy

MicroRNAs (miRs) have gained scientific attention due to their importance in the pathophysiology of allergic diseases as well as their potential as biomarkers in allergen-specific treatment options. Their function as post-transcriptional regulators, controlling various cellular processes, is of high importance since any single miR can target multiple mRNAs, often within the same signalling pathway. MiRs can alter dysregulated expression of certain cellular responses and contribute to or cause, but in some cases prevent or repress, the development of various diseases. In this review article, we describe current research on the role of specific miRs in regulating immune responses in epithelial cells and specialized immune cells in response to various stimuli, in allergic diseases, and regulation in the therapeutic approach of allergen-specific immunotherapy (AIT). Despite the fact that AIT has been used successfully as a causative treatment option since more than a century, very little is known about the mechanisms of regulation and its connections with microRNAs. In order to fill this gap, this review aims to provide an overview of the current knowledge.

Distinct spatial and temporal roles for Th1, Th2, and Th17 cells in asthma

Immune response in the asthmatic respiratory tract is mainly driven by CD4⁺ T helper (Th) cells, represented by Th1, Th2, and Th17 cells, especially Th2 cells. Asthma is a heterogeneous and progressive disease, reflected by distinct phenotypes orchestrated by τh2 or non-Th2 (Th1 and Th17) immune responses at different stages of the disease course. Heterogeneous cytokine expression within the same Th effector state in response to changing conditions in vivo and interlineage relationship among CD4⁺ T cells shape the complex immune networks of the inflammatory airway, making it difficult to find one panacea for all asthmatics. Here, we review the role of three T helper subsets in the pathogenesis of asthma from different stages, highlighting timing is everything in the immune system. We also discuss the dynamic topography of Th subsets and pathogenetic memory Th cells in asthma.

Roles of type 1 regulatory T (Tr1) cells in allergen-specific immunotherapy

Allergen-specific immunotherapy (AIT) is the only causative treatment for allergic diseases by modification of the immune response to allergens. A key feature of AIT is to induce immunotolerance to allergens by generating antigen-specific regulatory T (Treg) cells in allergic patients. Type 1 regulatory T (Tr1) cells and forkhead box protein 3 (Foxp3)-expressing Treg cells are well known among Treg cell subsets. Foxp3 was identified as a master transcription factor of Treg cells, and its expression is necessary for their suppressive activity. In contrast to Foxp3⁺ Treg cells, the master transcription factor of Tr1 cells has not been elucidated. Nevertheless, Tr1 cells are generally considered as a distinct subset of Treg cells induced in the periphery during antigen exposure in tolerogenic conditions and can produce large amounts of anti-inflammatory cytokines such as interleukin-10 and transforming growth factor-β, followed by down-regulation of the function of effector immune cells independently of Foxp3 expression. Since the discovery of Tr1 cells more than 20 years ago, research on Tr1 cells has expanded our understanding of the mechanism of AIT. Although the direct precursors and true identity of these cells continues to be disputed, we and others have demonstrated that Tr1 cells are induced in the periphery by AIT, and the induced cells are re-activated by antigens, followed by suppression of allergic symptoms. In this review, we discuss the immune mechanisms for the induction of Tr1 cells by AIT and the immune-suppressive roles of Tr1 cells in AIT.

Bronchial inflammation biomarker patterns link humoral immunodeficiency with bronchiectasis-related small airway dysfunction

BACKGROUND

The progression of chronic destructive lung disease in patients with humoral immunodeficiency (ID) and concomitant development of bronchiectasis is difficult to prevent. Lung function tests in these patients typically show bronchial obstruction of the small airways in combination with increased air trapping in the distal airways, which is consistent with small airway dysfunction.

OBJECTIVE

The objective was to assess the grade of chronic lower airway inflammation and small airway dysfunction from induced sputum and the corresponding local pro-inflammatory mediator pattern to discriminate patients affected by bronchiectasis-related Small Airway Dysfunction (SAD).

METHODS

In a prospective design, 22 patients with ID (14 CVID, 3 XLA, 3 hyper-IgM syndrome, 1 hyper-IgE syndrome and low IgG levels due to treatment with rituximab and 1 SCID after BMT and persistent humoral defect) and 21 healthy controls were examined. Lung function, Fraction Expiratory Nitric Oxide (FeNO) and pro-inflammatory cytokine levels were compared in subsets of patients with (ID + BE) and without bronchiectasis (ID) pre-stratified using high-resolution computed tomography (HRCT) scans and control subjects.

RESULTS

Analysis of induced sputum showed significantly increased total cell counts and severe neutrophilic inflammation in ID. The concomitant SAD revealed higher total cell numbers compared to ID. Bronchial inflammation in ID is clearly mirrored by pro-inflammatory mediators IL-1β, IL-6 and CXCL-8, whilst TNF-α revealed a correlation with lung function parameters altered in the context of bronchiectasis-related Small Airway Dysfunction.

CONCLUSIONS

In spite of immunoglobulin substitution, bronchial inflammation was dominated by neutrophils and was highly increased in patients with ID + BE. Notably, the pro-inflammatory cytokines in patients with ID were significantly increased in induced sputum. The context-dependent cytokine pattern in relation to the presence of concomitant bronchiectasis associated with SAD in ID patients could be helpful in delimiting ID patient subgroups and individualizing therapeutic approaches.

The Present and Future of Allergen Immunotherapy in Personalized Medicine

Allergic diseases are particularly suitable for personalized medicine, because they meet the needs for therapeutic success, which include a known molecular mechanism of the disease, a diagnostic tool for that disease and a treatment that blocks this mechanism. A range of tools is available for personalized allergy diagnosis, including molecular diagnostics, treatable traits and omics (i.e., proteomics, epigenomics, metabolomics, transcriptomics and breathomics), to predict patient response to therapies, detect biomarkers and mediators and assess disease control status. Such tools enhance allergen immunotherapy. Higher diagnostic accuracy results in a significant increase (based on a greater performance achieved with personalized treatment) in efficacy, further increasing the known and unique characteristics of a treatment designed to work on allergy causes.

Role of Respiratory Epithelial Cells in Allergic Diseases

The airway epithelium provides the first line of defense to the surrounding environment. However, dysfunctions of this physical barrier are frequently observed in allergic diseases, which are tightly connected with pro- or anti-inflammatory processes. When the epithelial cells are confronted with allergens or pathogens, specific response mechanisms are set in motion, which in homeostasis, lead to the elimination of the invaders and leave permanent traces on the respiratory epithelium. However, allergens can also cause damage in the sensitized organism, which can be ascribed to the excessive immune reactions. The tight interaction of epithelial cells of the upper and lower airways with local and systemic immune cells can leave an imprint that may mirror the pathophysiology. The interaction with effector T cells, along with the macrophages, play an important role in this response, as reflected in the gene expression profiles (transcriptomes) of the epithelial cells, as well as in the secretory pattern (secretomes). Further, the storage of information from past exposures as memories within discrete cell types may allow a tissue to inform and fundamentally alter its future responses. Recently, several lines of evidence have highlighted the contributions from myeloid cells, lymphoid cells, stromal cells, mast cells, and epithelial cells to the emerging concepts of inflammatory memory and trained immunity.

The Role of Defective Epithelial Barriers in Allergic Lung Disease and Asthma Development

The respiratory epithelium constitutes the physical barrier between the human body and the environment, thus providing functional and immunological protection. It is often exposed to allergens, microbial substances, pathogens, pollutants, and environmental toxins, which lead to dysregulation of the epithelial barrier and result in the chronic inflammation seen in allergic diseases and asthma. This epithelial barrier dysfunction results from the disturbed tight junction formation, which are multi-protein subunits that promote cell-cell adhesion and barrier integrity. The increasing interest and evidence of the role of impaired epithelial barrier function in allergy and asthma highlight the need for innovative approaches that can provide new knowledge in this area. Here, we review and discuss the current role and mechanism of epithelial barrier dysfunction in developing allergic diseases and the effect of current allergy therapies on epithelial barrier restoration.

Mechanisms of allergen immunotherapy supporting its disease-modifying effect

Allergen immunotherapy (AIT) is considered the only disease-modifying treatment available at present for allergic disorders. Its main benefits include improvement of symptoms, decreased need for pharmacotherapy, prevention of new sensitizations and sustained effect after AIT completion. The key pillars of AIT-induced tolerance include a shift from Th2 to Th1 response, an increase of regulatory T and B cells, pro-inflammatory effector cell downregulation and IgE suppression, in addition to IgG4, IgA and IgD induction. AIT may also induce trained immunity, characterized by a durable decrease in group 2 of innate lymphoid cells (ILCs) and increased ILC1 and ILC3s. Understanding the immune mechanisms of AIT is essential for validating biomarkers for the prediction of AIT response and for achieving AIT success.

IL-37 regulates allergic inflammation by counterbalancing pro-inflammatory IL-1 and IL-33

BACKGROUND

Children with asthma have impaired production of interleukin (IL) 37; in mice, IL-37 reduces hallmarks of experimental allergic asthma (EAA). However, it remains unclear how IL-37 exerts its inhibitory properties in asthma. This study aimed to identify the mechanism(s) by which IL-37 controls allergic inflammation.

METHODS

IL-37 target cells were identified by single-cell RNA-seq of IL-1R5 and IL-1R8. Airway tissues were isolated by laser-capture microdissection and examined by microarray-based gene expression analysis. Mononuclear cells (MNC) and airway epithelial cells (AECs) were isolated and stimulated with allergen, IL-1β, or IL-33 together with recombinant human (rh) IL-37. Wild-type, IL-1R1- and IL-33-deficient mice with EAA were treated with rhIL-37. IL-1β, IL-33, and IL-37 levels were determined in sputum and nasal secretions from adult asthma patients without glucocorticoid therapy.

RESULTS

IL-37 target cells included AECs, T cells, and dendritic cells. In mice with EAA, rhIL-37 led to differential expression of >90 genes induced by IL-1β and IL-33. rhIL-37 reduced production of Th2 cytokines in allergen-activated MNCs from wild-type but not from IL-1R1-deficient mice and inhibited IL-33-induced Th2 cytokine release. Furthermore, rhIL-37 attenuated IL-1β- and IL-33-induced pro-inflammatory mediator expression in murine AEC cultures. In contrast to wild-type mice, hIL-37 had no effect on EAA in IL-1R1- or IL-33-deficient mice. We also observed that expression/production ratios of both IL-1β and IL-33 to IL-37 were dramatically increased in asthma patients compared to healthy controls.

CONCLUSION

IL-37 downregulates allergic airway inflammation by counterbalancing the disease-amplifying effects of IL-1β and IL-33.

Secretoglobins in the big picture of immunoregulation in airway diseases

The proteins of the secretoglobin (SCGB) family are expressed by secretory tissues of barrier organs. They are embedded in immunoregulatory and anti-inflammatory processes of airway diseases. This review particularly illustrates the immune regulation of SCGBs by cytokines and their implication in the pathophysiology of airway diseases. The biology of SCGBs is a complex topic of increasing importance, as they are highly abundant in the respiratory tract and can also be detected in malignant tissues and as elements of immune control. In addition, SCGBs react to cytokines, they are embedded in Th1 and Th2 immune responses, and they are expressed in a manner dependent on cell maturation. The big picture of the SCGB family identifies these factors as critical elements of innate immune control at the epithelial barriers and highlights their potential for diagnostic assessment of epithelial activity. Some members of the SCGB family have so far only been superficially examined, but have high potential for translational research.

TGF-β1 Drives Inflammatory Th Cell But Not Treg Cell Compartment Upon Allergen Exposure

TGF-β1 is known to have a pro-inflammatory impact by inducing Th9 and Th17 cells, while it also induces anti-inflammatory Treg cells (Tregs). In the context of allergic airway inflammation (AAI) its dual role can be of critical importance in influencing the outcome of the disease. Here we demonstrate that TGF-β is a major player in AAI by driving effector T cells, while Tregs differentiate independently. Induction of experimental AAI and airway hyperreactivity in a mouse model with inducible genetic ablation of the gene encoding for TGFβ-receptor 2 (Tgfbr2) on CD4⁺T cells significantly reduced the disease phenotype. Further, it blocked the induction of pro-inflammatory T cell frequencies (Th2, Th9, Th17), but increased Treg cells. To translate these findings into a human clinically relevant context, Th2, Th9 and Treg cells were quantified both locally in induced sputum and systemically in blood of allergic rhinitis and asthma patients with or without allergen-specific immunotherapy (AIT). Natural allergen exposure induced local and systemic Th2, Th9, and reduced Tregs cells, while therapeutic allergen exposure by AIT suppressed Th2 and Th9 cell frequencies along with TGF-β and IL-9 secretion. Altogether, these findings support that neutralization of TGF-β represents a viable therapeutic option in allergy and asthma, not posing the risk of immune dysregulation by impacting Tregs cells.

Interleukin-24 Immunobiology and Its Roles in Inflammatory Diseases

Interleukin (IL)-24 belongs to the IL-10 family and signals through two receptor complexes, i.e., IL-20RA/IL-20RB and IL-20RB/IL22RA1. It is a multifunctional cytokine that can regulate immune response, tissue homeostasis, host defense, and oncogenesis. Elevation of IL-24 is associated with chronic inflammation and autoimmune diseases, such as psoriasis, rheumatoid arthritis (RA), and inflammatory bowel disease (IBD). Its pathogenicity has been confirmed by inducing inflammation and immune cell infiltration for tissue damage. However, recent studies also revealed their suppressive functions in regulating immune cells, including T cells, B cells, natural killer (NK) cells, and macrophages. The tolerogenic properties of IL-24 were reported in various animal models of autoimmune diseases, suggesting the complex functions of IL-24 in regulating autoimmunity. In this review, we discuss the immunoregulatory functions of IL-24 and its roles in autoimmune diseases.

Airway Basal Cells, Protectors of Epithelial Walls in Health and Respiratory Diseases

The airway epithelium provides a critical barrier to the outside environment. When its integrity is impaired, epithelial cells and residing immune cells collaborate to exclude pathogens and to heal tissue damage. Healing is achieved through tissue-specific stem cells: the airway basal cells. Positioned near the basal membrane, airway basal cells sense and respond to changes in tissue health by initiating a pro-inflammatory response and tissue repair via complex crosstalks with nearby fibroblasts and specialized immune cells. In addition, basal cells have the capacity to learn from previous encounters with the environment. Inflammation can indeed imprint a certain memory on basal cells by epigenetic changes so that sensitized tissues may respond differently to future assaults and the epithelium becomes better equipped to respond faster and more robustly to barrier defects. This memory can, however, be lost in diseased states. In this review, we discuss airway basal cells in respiratory diseases, the communication network between airway basal cells and tissue-resident and/or recruited immune cells, and how basal cell adaptation to environmental triggers occurs.

Severe acute asthma at the pediatric intensive care unit: can we link the clinical phenotypes to immunological endotypes?

INTRODUCTION

The clinical phenotype of severe acute asthma at the pediatric intensive care unit (PICU) is highly heterogeneous. However, current treatment is still based on a 'one-size-fits-all approach'.

AREAS COVERED

We aim to give a comprehensive description of the clinical characteristics of pediatric patients with severe acute asthma admitted to the PICU and available immunological biomarkers, providing the first steps toward precision medicine for this patient population. A literature search was performed using PubMed for relevant studies on severe acute (pediatric) asthma.

EXPERT OPINION

Omics technologies should be used to investigate the relationship between cellular molecules and pathways, and their clinical phenotypes. Inflammatory phenotypes might guide bedside decisions regarding the use of corticosteroids, neutrophil modifiers and/or type of beta-agonist. A next step toward precision medicine should be inclusion of these patients in clinical trials on biologics.

Wheezing-Related Relevant Factors and the Role of Viral Bronchiolitis

Bronchiolitis is a virus-associated infection of the lower respiratory tract exhibiting signs and symptoms of airway obstruction. Respiratory Syncytial Virus (RSV) is responsible in most cases; however, different rhinoviruses have also been implicated. Specific viruses and time until the first infection, severity of the respiratory condition, and atopic status have a determinant role in the recurrence of wheezing and asthma development. Genetics, lung function, atopic condition, the role of microbiota and environment, pollution, and obesity are considered in the present review. Emergency room visits and hospitalizations because of severe wheezing and smoking during pregnancy among others were identified as risk factors for significant morbidity in our population. Approaching determinant conditions like genetics, allergy, antiviral immunity, and environmental exposures such as farm vs. urban and viral virulence provides an opportunity to minimize morbidity of viral illness and asthma in children.

Sputum microRNA-screening reveals Prostaglandin EP3 receptor as selective target in allergen-specific immunotherapy

BACKGROUND

Several microRNAs (miRs) have been described as potential biomarkers in liquid biopsies and in the context of allergic asthma, while therapeutic effects on the airway expression of miRs remain elusive. In this study, we investigated epigenetic miR-associated mechanisms in the sputum of grass pollen-allergic patients with and without allergen-specific immunotherapy (AIT).

METHODS

Induced sputum samples of healthy controls (HC), AIT-treated and -untreated grass pollen-allergic rhinitis patients with (AA) and without asthma (AR) were profiled using miR microarray and whole-transcriptome microarray analysis of the same samples. miR targets were predicted in silico and used to identify inverse regulation. Local PGE₂  levels were measured using ELISA.

RESULTS

Two hundred and fifty nine miRs were upregulated in the sputum of AA patients compared with HC, while only one was downregulated. The inverse picture was observed in induced sputum of AIT-treated patients: while 21 miRs were downregulated, only 4 miRs were upregulated in asthmatics upon AIT. Of these 4 miRs, miR-3935 stood out, as its predicted target PTGER3, the prostaglandin EP₃ receptor, was downregulated in treated AA patients compared with untreated. The levels of its ligand PGE₂ in the sputum supernatants of these samples were increased in allergic patients, especially asthmatics, and downregulated after AIT. Finally, local PGE₂  levels correlated with ILC2 frequencies, secreted sputum IL-13 levels, inflammatory cell load, sputum eosinophils and symptom burden.

CONCLUSIONS

While profiling the sputum of allergic patients for novel miR expression patterns, we uncovered an association between miR-3935 and its predicted target gene, the prostaglandin E₃ receptor, which might mediate AIT effects through suppression of the PGE₂ -PTGER3 axis.