Activation of CD4+ T cells, increased TH2-type cytokine mRNA expression, and eosinophil recruitment in bronchoalveolar lavage after allergen inhalation challenge in patients with atopic asthma

The Late Asthmatic Reaction Is in Part Independent from the Early Asthmatic Reactions

House dust mites (HDM) are the world's most important cause of allergic asthma. It is unclear why some patients with HDM allergy develop an early asthmatic reaction (EAR) only, whereas others react with a dual asthmatic reaction-EAR plus late asthmatic reaction (LAR). In patients with LAR, the symptoms and bronchial inflammation are more severe, and the current knowledge suggests that the EAR always precedes the LAR. The aim of the present study was to investigate whether a LAR can occur separately even without a significant EAR. In a pilot study of 20 patients with asthma and HDM allergy, a bronchial allergen challenge (BAC) was performed on three separate occasions with a tapered allergen dose. Before and 24 h later, exhaled NO (eNO), eosinophils and miRNAs were measured as markers of bronchial inflammation. Compared to BAC1, at BAC2 there was a significant decrease in the EAR from mean 39.25 ± 13.37% to mean 33.55 ± 5.25% (p < 0.01), whereas the LAR remained unchanged: mean 28.10 ± 10.95% to mean 30.31 ± 7.77% (n.s.). At BAC3, both the EAR and the LAR were significantly attenuated compared to the first and second BAC. In 3 (15%) patients, even the tapered allergen dose induced a dual asthmatic reaction. In 10 (50%) patients, the allergen dose was too low to trigger a significant EAR and LAR. In 7 (35%) patients, there was no EAR, but a significant LAR (mean max fall FEV1 20.5 + 4.7%) recorded. Significant correlations (p < 0.05) were found between distinct miRNAs (miR-15a-5p, miR-15b-5p and miR-374a-p5), eNO, and the decline in lung function and the presence of a LAR (p < 0.01). We can demonstrate that a LAR is induced in some patients without an EAR to low allergen exposure. This leads to a strong inflammatory reaction with an increase in eNO and a decrease in FEV1 and distinct miRNAs. Accordingly, these individuals are at greater risk of asthmatic symptoms and remodeling with loss of lung function than patients who do not have a LAR.

Biologic Medications for Severe Asthma: Implications for Understanding Pathogenic Heterogeneity and Endotypes

Asthma is a chronic inflammatory disease of the airways long known for phenotypic heterogeneity. Phenotyping studies in asthma have led to a better characterization of disease pathogenesis, yet further work is needed to pair available treatments with disease endotypes. In this review, the biology of targeted pathways is discussed along with the efficacy of biologic therapies targeting those pathways. Results of asthma clinical trials are included, as well as results of trials in related diseases. This review then analyzes how biologics help to inform the complex immunobiology of asthma and further guide their use while identifying areas for future research.

Deletion of Miro1 in airway club cells potentiates allergic asthma phenotypes

Mitochondria are multifaceted organelles necessary for numerous cellular signaling and regulatory processes. Mitochondria are dynamic organelles, trafficked and anchored to subcellular sites depending upon the cellular and tissue requirements. Precise localization of mitochondria to apical and basolateral membranes in lung epithelial cells is important for key mitochondrial processes. Miro1 is an outer mitochondrial membrane GTPase that associates with adapter proteins and microtubule motors to promote intracellular movement of mitochondria. We show that deletion of Miro1 in lung epithelial cells leads to perinuclear clustering of mitochondria. However, the role of Miro1 in epithelial cell response to allergic insults remains unknown. We generated a conditional mouse model to delete Miro1 in Club Cell Secretory Protein (CCSP) positive lung epithelial cells to examine the potential roles of Miro1 and mitochondrial trafficking in the lung epithelial response to the allergen, house dust mite (HDM). Our data show that Miro1 suppresses epithelial induction and maintenance of the inflammatory response to allergen, as Miro1 deletion modestly induces increases in pro-inflammatory signaling, specifically IL-6, IL-33, CCL20 and eotaxin levels, tissue reorganization, and airway hyperresponsiveness. Furthermore, loss of Miro1 in CCSP+ lung epithelial cells blocks resolution of the asthmatic insult. This study further demonstrates the important contribution of mitochondrial dynamic processes to the airway epithelial allergen response and the pathophysiology of allergic asthma.

Usage of celery root exosome as an immune suppressant; Lipidomic characterization of apium graveolens originated exosomes and its suppressive effect on PMA/ionomycin mediated CD4+ T lymphocyte activation

Diseases such as autoimmune, cancer, neurodegenerative diseases or obesity have a serious impact on the lives of patients all rise from a common point; the immune system. Various in vitro and in vivo studies on regulating the immune system have been made to correct these diseases. As one of the key effector cells of the immune system, T lymphocytes are the focus of many of these studies. In this study, exosomes isolated from a known anti-inflammatory plant, celery, were used to suppress the inflammatory response of T lymphocytes. Celery-derived exosomes (C-Exo) were isolated using an aqueous two-phase isolation method. The size distribution, morphology, particle concentration, and GC-FAME-based lipidomic analysis were determined for the isolated C-Exo. T lymphocytes were stimulated using Phorbol 12-myristate 13-acetate (PMA)/ionomycin, and treated with various doses of C-Exo. T lymphocyte responses were measured using qPCR and capillary Western blots. According to the results, C-Exo suppressed T lymphocytes in a dose-dependent manner in in vitro conditions. These findings show the potential of C-Exo as a therapeutic agent for immune disorders. PRACTICAL APPLICATION: Excessive immune response in the body adversely affects the treatment mechanism and process of many diseases such as autoimmune disorders, neurodegenerative diseases and GDHV. In this preliminary study, the role of extracellular vesicles obtained from celery roots in suppressing this high immune response was investigated. The suppressive effect of celery exosome was observed by creating an immune response in T cells and PBMC cells, which play a leading role in the immune response. The role of these vesicles in immune suppression, obtained from the root part of the celery plant and characterized, was determined by measuring both mRNA, intracellular protein and extracellular cytokine levels. Celery exosome suppressed activated T lymphocyte cells and PBMC cells in a dose-dependent manner. These vesicles, which can be used as an edible, can be used in many areas as immunosuppressants.

Understanding Immune Responses to Viruses-Do Underlying Th1/Th2 Cell Biases Predict Outcome?

Emerging and re-emerging viral diseases have increased in number and geographical extent during the last decades. Examples include the current COVID-19 pandemic and the recent epidemics of the Chikungunya, Ebola, and Zika viruses. Immune responses to viruses have been well-characterised within the innate and adaptive immunity pathways with the outcome following viral infection predominantly attributed to properties of the virus and circumstances of the infection. Perhaps the belief that the immune system is often considered as a reactive component of host defence, springing into action when a threat is detected, has contributed to a poorer understanding of the inherent differences in an individual's immune system in the absence of any pathology. In this review, we focus on how these host factors (age, ethnicity, underlying pathologies) may skew the T helper cell response, thereby influencing the outcome following viral infection but also whether we can use these inherent biases to predict patients at risk of a deviant response and apply strategies to avoid or overcome them.

Allergen Provocation Tests in Respiratory Research: Building on 50 Years of Experience

Allergen provocation test is an established model of allergic airway diseases, including asthma and allergic rhinitis, allowing the study of allergen-induced changes in respiratory physiology and inflammatory mechanisms in sensitised individuals as well as their associations. In the upper airways, allergen challenge is focused on the clinical and pathophysiological sequelae of the early allergic response and applied both as a diagnostic tool and in research settings. In contrast, the bronchial allergen challenge has almost exclusively served as a research tool in specialised research settings with a focus on the late asthmatic response and the underlying type 2 inflammation. The allergen-induced late asthmatic response is also characterised by prolonged airway narrowing, increased non-specific airway hyperresponsiveness and features of airway remodelling including the small airways, and hence, allows the study of several key mechanisms and features of asthma. In line with these characteristics, the allergen challenge has served as a valued tool to study the crosstalk of the upper and lower airways and in proof of mechanism studies of drug development. In recent years, several new insights into respiratory phenotypes and endotypes including the involvement of the upper and small airways, innovative biomarker sampling methods and detection techniques, refined lung function testing as well as targeted treatment options, further shaped the applicability of the allergen provocation test in precision medicine. These topics, along with descriptions of subject populations and safety, in line with the updated GINA2021, will be addressed in this paper.

Role of Exercise Intensity on Th1/Th2 Immune Modulations During the COVID-19 Pandemic

The COVID-19 pandemic has led to several pioneering scientific discoveries resulting in no effective solutions with the exception of vaccination. Moderate exercise is a significant non-pharmacological strategy, to reduce the infection-related burden of COVID-19, especially in patients who are obese, elderly, and with additional comorbidities. The imbalance of T helper type 1 (Th1) or T helper type 2 (Th2) cells has been well documented among populations who have suffered as a result of the COVID-19 pandemic, and who are at maximum risk of infection and mortality. Moderate and low intensity exercise can benefit persons at risk from the disease and survivors by favorable modulation in Th1/Th2 ratios. Moreover, in COVID-19 patients, mild to moderate intensity aerobic exercise also increases immune system function but high intensity aerobic exercise may have adverse effects on immune responses. In addition, sustained hypoxia in COVID-19 patients has been reported to cause organ failure and cell death. Hypoxic conditions have also been highlighted to be triggered in COVID-19-susceptible individuals and COVID-19 survivors. This suggests that hypoxia inducible factor (HIF 1α) might be an important focus for researchers investigating effective strategies to minimize the effects of the pandemic. Intermittent hypoxic preconditioning (IHP) is a method of exposing subjects to short bouts of moderate hypoxia interspersed with brief periods of normal oxygen concentrations (recovery). This methodology inhibits the production of pro-inflammatory factors, activates HIF-1α to activate target genes, and subsequently leads to a higher production of red blood cells and hemoglobin. This increases angiogenesis and increases oxygen transport capacity. These factors can help alleviate virus induced cardiopulmonary hemodynamic disorders and endothelial dysfunction. Therefore, during the COVID-19 pandemic we propose that populations should engage in low to moderate exercise individually designed, prescribed and specific, that utilizes IHP including pranayama (yoga), swimming and high-altitude hiking exercise. This would be beneficial in affecting HIF-1α to combat the disease and its severity. Therefore, the promotion of certain exercises should be considered by all sections of the population. However, exercise recommendations and prescription for COVID-19 patients should be structured to match individual levels of capability and adaptability.

Role of CD4+ T Cells in Allergic Airway Diseases: Learning from Murine Models

The essential contribution of CD4⁺ T cells in allergic airway diseases has been demonstrated, especially by using various murine models of antigen-induced airway inflammation. In addition to antigen-immunized mouse models employing mast cell-deficient mice and CD4⁺ T cell-depleting procedure, antigen-specific CD4⁺ T cell transfer models have revealed the possible development of allergic inflammation solely dependent on CD4⁺ T cells. Regardless of the classical Th1/Th2 theory, various helper T cell subsets have the potential to induce different types of allergic inflammation. T cell receptor (TCR)-transgenic (Tg) mice have been used for investigating T cell-mediated immune responses. Besides, we have recently generated cloned mice from antigen-specific CD4⁺ T cells through somatic cell nuclear transfer. In contrast to TCR-Tg mice that express artificially introduced TCR, the cloned mice express endogenously regulated antigen-specific TCR. Upon antigen exposure, the mite antigen-reactive T cell-cloned mice displayed strong airway inflammation accompanied by bronchial hyperresponsiveness in a short time period. Antigen-specific CD4⁺ T cell-cloned mice are expected to be useful for investigating the detailed role of CD4⁺ T cells in various allergic diseases and for evaluating novel anti-allergic drugs.

T cells modulate IL-4 expression by eosinophil recruitment within decellularized scaffolds to repair nerve defects

Decellularized nerve, or acellular nerve allografts (ANAs), are an increasingly used alternative to nerve autografts to repair nerve gaps to facilitate regeneration. The adaptive immune system, specifically T cells, plays a role in promoting regeneration upon these ANA scaffolds. However, how T cells promote regeneration across ANAs is not clear. Here, we show that T cells accumulate within ANAs repairing nerve gaps resulting in regulation of cytokine expression within the ANA environment. This in turn ultimately leads to robust nerve regeneration and functional recovery. Nerve regeneration across ANAs and functional recovery in Rag1KO mice was limited compared to wild-type (WT) mice. Prior to appreciable nerve regeneration, ANAs from Rag1KO mice contained fewer eosinophils and reduced IL-4 expression compared to ANAs from WT mice. During this period, both T cells and eosinophils regulated IL-4 expression within ANAs. Eosinophils represented the majority of IL-4 expressing cells within ANAs, while T cells regulated IL-4 expression. Finally, an essential role for IL-4 during nerve regeneration across ANAs was confirmed as nerves repaired using ANAs had reduced regeneration in IL-4 KO mice compared to WT mice. Our data demonstrate T cells regulate the expression of IL-4 within the ANA environment via their effects on eosinophils. STATEMENT OF SIGNIFICANCE: The immune system has been emerging as a critical component for tissue regeneration, especially when regeneration is supported upon biomaterials. The role of T cells, and their roles in the regeneration of nerve repaired with biomaterials, is still unclear. We demonstrated that when nerves are repaired with decellularized nerve scaffolds, T cells contribute to regeneration by regulating cytokines. We focused on their regulation of cytokine IL-4. Unexpectedly, T cells do not produce IL-4, but instead regulate IL-4 by recruiting eosinophils, which are major cellular sources of IL-4 within these scaffolds. Thus, our work demonstrated how IL-4 is regulated in a model biomaterial, and has implications for improving the design of biomaterials and understanding immune responses to biomaterials.

Are We Meeting the Promise of Endotypes and Precision Medicine in Asthma?

While the term asthma has long been known to describe heterogeneous groupings of patients, only recently have data evolved which enable a molecular understanding of the clinical differences. The evolution of transcriptomics (and other 'omics platforms) and improved statistical analyses in combination with large clinical cohorts opened the door for molecular characterization of pathobiologic processes associated with a range of asthma patients. When linked with data from animal models and clinical trials of targeted biologic therapies, emerging distinctions arose between patients with and without elevations in type 2 immune and inflammatory pathways, leading to the confirmation of a broad categorization of type 2-Hi asthma. Differences in the ratios, sources, and location of type 2 cytokines and their relation to additional immune pathway activation appear to distinguish several different (sub)molecular phenotypes, and perhaps endotypes of type 2-Hi asthma, which respond differently to broad and targeted anti-inflammatory therapies. Asthma in the absence of type 2 inflammation is much less well defined, without clear biomarkers, but is generally linked with poor responses to corticosteroids. Integration of "big data" from large cohorts, over time, using machine learning approaches, combined with validation and iterative learning in animal (and human) model systems is needed to identify the biomarkers and tightly defined molecular phenotypes/endotypes required to fulfill the promise of precision medicine.

The neuro-immune interaction in airway inflammation through TRPA1 expression in CD4+ T cells of asthmatic mice

Asthma is an inflammatory disorder of the airways dominated by a Th2-type pattern. Recently, an emerging interest arises whether transient receptor potential ankyrin 1 (TRPA1) plays a potential role in the adaptive immune response. In this study, the role of TRPA1 in the development and exacerbation of asthma was explored. The classic OVA-induced asthma and OVA plus PM2.5-induced exacerbated asthma model were used. The CD4+ T cells were sorted from spleen in asthmatic and exacerbated asthmatic mice. In the BALB/c mice treated with OVA, the increased phenotype of asthma was obtained, accompanied by the high expression of TRPA1 in lung tissue and levels of IL-4, IL-13, NGF, PGD₂ in BAL. In contrast, genetic deletion or pharmacological inhibition of TRPA1 alleviated the phenotype of asthma. Similarly, in wild type (WT) C57BL/6 mice treated with OVA, the high expression of TRPA1 in lung tissues was obtained, and the levels of IL-4, IL-13, NGF, PGD₂ in BAL remarkably increased when compared with those in the TRPA1 deleted mice. Furthermore, high expression of TRPA1 was detected in CD4+ T cells of OVA-treated WT C57BL/6 mice. Additional detection in the asthmatic mice exacerbated by OVA plus PM2.5 also showed high TRPA1 expression in lung tissue and CD4+ T cells. All evidence confirmed that TRPA1 is essential for the development and exacerbation of asthma. More importantly, the expression of TRPA1 in CD4+ T cells of different asthmatic mice suggested that it might be involved in neuro-immune interactions in airway inflammation of asthmatic mice.

Identification of a novel splice variant for mouse and human interleukin-5

Expression of interleukins and their receptors is often regulated by alternative splicing. Alternative isoform of IL-5 receptor α-chain is well studied; however, no data on functional alternative splice variants of IL-5 has been reported up today. In the present study, we describe a novel splice variant for the mouse and human IL-5. The new form was found during analysis of PCR-products amplified from different mouse lymphoid tissues with a pair of primers designed to clone full-length mIL-5 ORF. A single short isoform of mIL-5 was detected along with the canonical full-length mRNA in ConA-stimulated lymphoid cells isolated from spleen, thymus, lymph nodes and blood. It was 30-40 nt shorter, and less abundant than classical form. The sequence analysis of an additional form of mIL-5 revealed that it lacks exon-2 (δ2). Using RT-PCR with the splice-specific primers we obtained an additional evidence for δ2 form expression. To verify whether mIL-5δ2 transcript is translated into protein, the coding sequences corresponding to full and δ2 forms of mIL-5 were cloned into an expression plasmid. After transfection into the human 293T cell line, we found that the short form of mIL-5 protein is expressed in cells and secreted into the supernatant, but at the reduced level than that detected for full isoform of mIL-5. Fluorescence microscopy examination revealed a partial translocation of mIL-5δ2 into cytoplasm, whereas mIL-5 resided mostly within endoplasmic reticulum. This can explain why the level of δ2 protein expression was reduced. Using a similar set of experimental approaches, we received the evidence that the human IL-5 mRNA has the δ2 splice form (hIL-5δ2) as well. It can be firmly detected by RT-PCR in PHA-activated mononuclear cells isolated from peripheral blood of healthy persons or patients with asthma. Altogether, our results showed that the human and mouse IL-5 have an alternative mRNA splice isoform, which loses exon-2, but nevertheless is expressed at protein level. However, more comprehensive studies will be required for evaluation of IL-5δ2 expression, regulation, biological function and clinical significance.

Proinflammatory Pathways in the Pathogenesis of Asthma

There are multiple proinflammatory pathways in the pathogenesis of asthma. These include both innate and adaptive inflammation, in addition to inflammatory and physiologic responses mediated by eicosanoids. An important component of the innate allergic immune response is ILC2 activated by interleukin (IL)-33, thymic stromal lymphopoietin, and IL-25 to produce IL-5 and IL-13. In terms of the adaptive T-lymphocyte immunity, CD4+ Th2 and IL-17-producing cells are critical in the inflammatory responses in asthma. Last, eicosanoids involved in asthma pathogenesis include prostaglandin D₂ and the cysteinyl leukotrienes that promote smooth muscle constriction and inflammation that propagate allergic responses.

CD8+ Tc2 cells: underappreciated contributors to severe asthma

The complexity of asthma is underscored by the number of cell types and mediators implicated in the pathogenesis of this heterogeneous syndrome. Type 2 CD4⁺ T-cells (Th2) and more recently, type 2 innate lymphoid cells dominate current descriptions of asthma pathogenesis. However, another important source of these type 2 cytokines, especially interleukin (IL)-5 and IL-13, are CD8⁺ T-cells, which are increasingly proposed to play an important role in asthma pathogenesis, because they are abundant and are comparatively insensitive to corticosteroids. Many common triggers of asthma exacerbations are mediated via corticosteroid-resistant pathways involving neutrophils and CD8⁺ T-cells. Extensive murine data reveal the plasticity of CD8⁺ T-cells and their capacity to enhance airway inflammation and airway dysfunction. In humans, Tc2 cells are predominant in fatal asthma, while in stable state, severe eosinophilic asthma is associated with greater numbers of Tc2 than Th2 cells in blood, bronchoalveolar lavage fluid and bronchial biopsies. Tc2 cells strongly express CRTH2, the receptor for prostaglandin D2, the cysteinyl leukotriene receptor 1 and the leukotriene B4 receptor. When activated, these elicit Tc2 cell chemotaxis and production of chemokines and type 2 and other cytokines, resulting directly or indirectly in eosinophil recruitment and survival. These factors position CD8⁺ Tc2 cells as important and underappreciated effector cells contributing to asthma pathogenesis. Here, we review recent advances and new insights in understanding the pro-asthmatic functions of CD8⁺ T-cells in eosinophilic asthma, especially corticosteroid-resistant asthma, and the molecular mechanisms underlying their pathologic effector function.

Alongside Th2 and ILC2 cells, CD8⁺ T-cells are a cellular source of type 2 cytokines. We review recent findings and insights into the pathologic effector functions of type 2 CD8⁺ T-cells in eosinophilic asthma, especially steroid-resistant disease.http://bit.ly/2KbVGL2

Novel Biological Therapies in Severe Asthma: Targeting the Right Trait

Asthma is a heterogeneous disease characterized by chronic airway inflammation that results in a wide spectrum of clinical manifestations. Patients with severe asthma represent a substantial share of consumption of healthcare resources and hospitalization. Moreover, these patients are at risk of increased morbidity and mortality. Recently, several phenotypes and endotypes of asthma have been identified. The identification of specific subtypes of asthma is fundamental for optimizing the clinical benefit of novel treatments. Although in most patients the disease can be controlled by some combination of pharmacologic agents, in some 5-10% of patients the disease remains uncontrolled. Several monoclonal antibodies (mAbs) targeting pathogenetic molecules (e.g., IgE, IL-5, IL- 5Rα, IL-4, IL-13, TSLP) are currently available or under development for the treatment of different forms of severe type 2 asthma. The identification of diagnostic and predictive biomarkers (e.g., IgE, blood eosinophil count, FeNO, periostin, etc.) has revolutioned the field of targeted therapy in severe asthma. Monoclonal antibodies targeting Th2-driven inflammation are generally safe in adult patients with moderate-to-severe asthma. The long-term safety of these biologics is a relevant issue that should be addressed. Unfortunately, little is known about non-type 2 asthma. Further studies are needed to identify biomarkers to guide targeted therapies of different forms of non-type 2 asthma.

TLRs in pulmonary diseases

Toll-like receptors (TLRs) comprise a clan of proteins involved in identification and triggering a suitable response against pathogenic attacks. As lung is steadily exposed to multiple infectious agents, antigens and host-derived danger signals, the inhabiting stromal and myeloid cells of the lung express an aggregate of TLRs which perceive the endogenously derived damage-associated molecular patterns (DAMPs) along with pathogen associated molecular patterns (PAMPs) and trigger the TLR-associated signalling events involved in host defence. Thus, they form an imperative component of host defence activation in case of microbial infections as well as non-infectious pulmonary disorders such as interstitial lung disease, acute lung injury and airways disease, such as COPD and asthma. They also play an equally important role in lung cancer. Targeting the TLR signalling network would pave ways to the design of more reliable and effective vaccines against infectious agents and control deadly infections, desensitize allergens and reduce inflammation. Moreover, TLR agonists may act as adjuvants by increasing the efficiency of cancer vaccines, thereby contributing their role in treatment of lung cancer too. Overall, TLRs present a compelling and expeditiously bolstered area of research and addressing their signalling events would be of significant use in pulmonary diseases.

Smoldering and flaming biomass wood smoke inhibit respiratory responses in mice

Background: Acute and chronic exposures to biomass wildfire smoke pose significant health risks to firefighters and impacted communities. Susceptible populations such as asthmatics may be particularly sensitive to wildfire effects. We examined pulmonary responses to biomass smoke generated from combustion of peat, oak, or eucalyptus in control and house dust mite (HDM)-allergic mice. Methods: Mice were exposed 1 h/d for 2 consecutive days to emissions from each fuel type under smoldering or flaming conditions (∼40 or ∼3.3 mg PM/m³, respectively) while maintaining comparable CO levels (∼60-120 ppm). Results: Control and allergic mice reduced breathing frequency during exposure to all biomass emissions compared with pre-exposure to clean air. Smoldering eucalyptus and oak, but not peat, further reduced frequency compared to flaming conditions in control and allergic groups, while also reducing minute volume and peak inspiratory flow in control mice. Several biochemical and cellular markers of lung injury and inflammation were suppressed by all biomass emission types in both HDM-allergic and control mice. Control mice exposed to flaming eucalyptus at different PM concentrations (C) and times (T) with the same C × T product had a greater decrease in breathing frequency with high concentration acute exposure compared with lower concentration episodic exposure. This decrease was ameliorated by PM HEPA filtration, indicating that the respiratory changes were partially mediated by biomass smoke particles. Conclusion: These data show that exposure to smoldering eucalyptus or oak smoke inhibits respiratory responses to a greater degree than peat smoke. Anti-inflammatory effects of CO may possibly contribute to smoke-induced suppression of allergic inflammatory responses.

Relationship between various cytokines implicated in asthma

Asthma is a complex disorder involving immunologic, environmental, genetic and other factors. Today, asthma is the most common disease encountered in clinical medicine in both children and adults worldwide. Asthma is characterized by increased responsiveness of the tracheobronchial tree resulting in chronic swelling and inflammation of the airways recognized to be controlled by the T-helper 2 (Th2) lymphocytes, which secrete cytokines to increase the production of IgE by B cells. There are many cytokines implicated in the development of the chronic inflammatory processes that are often observed in asthma. Ultimately, these cytokines cause the release of mediators such as histamine and leukotrienes (LT), which in turn promote airway remodeling, bronchial hyperresponsiveness and bronchoconstriction. The CD4⁺ T-lymphocytes from the airways of asthmatics express a panel of cytokines that represent the Th2 cells. The knowledge derived from numerous experimental and clinical studies have allowed physicians and scientists to understand the normal functions of these cytokines and their roles in the pathogenesis of asthma. The main focus of this review is to accentuate the relationship between various cytokines implicated in human asthma. However, some key findings from animal models will be highlighted to support the discoveries from clinical studies.

A Multicentre, Randomized, Double-Blind, Placebo-Controlled, Crossover Study To Investigate the Efficacy, Safety, Tolerability, and Pharmacokinetics of Repeat Doses of Inhaled Nemiralisib in Adults with Persistent, Uncontrolled Asthma

Phosphoinositide 3-kinase δ (PI3Kδ) is a lipid kinase involved in leukocyte recruitment and activation. Activation of PI3Kδ has been linked to airway inflammation and asthma pathogenesis. This randomized, double-blind, placebo-controlled, crossover study investigated the efficacy, safety, tolerability, and pharmacokinetics of a PI3Kδ inhibitor, nemiralisib (GSK2269557), in patients with persistent, uncontrolled asthma. Patients (n = 50) received once-daily inhaled nemiralisib (1000 µg) or placebo for 28 days, with a crossover to the alternative treatment following a 4-week washout period. Spirometry demonstrated no discernible difference in trough forced expiratory volume in 1 second (FEV1) from baseline (adjusted posterior median 7 ml; 95% credible interval -83, 102 ml) between nemiralisib and placebo treatment at day 28 (primary endpoint). These results were supported by most secondary endpoints, including weighted mean FEV1 (0-4 hours) and change in trough forced vital capacity at day 28. Nemiralisib was generally well-tolerated, with few side effects except for post-inhalation cough (nemiralisib: 35%; placebo: 9%). At day 14, sputum interleukin (IL)-5, IL-13, IL-6, and IL-8 levels were reduced by a median of 17%, 7%, 15%, and 8%, respectively, when comparing nemiralisib with placebo [n = 15 (IL-5, IL-8) or 16 (IL-6, IL-13); posterior probability of a true ratio >0%: 78%, 64%, 76%, and 63%, respectively]. These results suggest that nemiralisib inhibited PI3Kδ locally; however, this did not translate into meaningful clinical improvement. Further studies will investigate the potential efficacy of nemiralisib in patients with asthma with other specific more severe phenotypes, including those who are colonized with bacteria and frequently exacerbate.

Messing with the Sentinels-The Interaction of Staphylococcus aureus with Dendritic Cells

Staphylococcus aureus (S. aureus) is a dangerous pathogen as well as a frequent colonizer, threatening human health worldwide. Protection against S. aureus infection is challenging, as the bacteria have sophisticated strategies to escape the host immune response. To maintain equilibrium with S. aureus, both innate and adaptive immune effector mechanisms are required. Dendritic cells (DCs) are critical players at the interface between the two arms of the immune system, indispensable for inducing specific T cell responses. In this review, we highlight the importance of DCs in mounting innate as well as adaptive immune responses against S. aureus with emphasis on their role in S. aureus-induced respiratory diseases. We also review what is known about mechanisms that S. aureus has adopted to evade DCs or manipulate these cells to its advantage.

Modeling TH 2 responses and airway inflammation to understand fundamental mechanisms regulating the pathogenesis of asthma

In this review, we highlight experiments conducted in our laboratories that have elucidated functional roles for CD4⁺ T-helper type-2 lymphocytes (T_H 2 cells), their associated cytokines, and eosinophils in the regulation of hallmark features of allergic asthma. Notably, we consider the complexity of type-2 responses and studies that have explored integrated signaling among classical T_H 2 cytokines (IL-4, IL-5, and IL-13), which together with CCL11 (eotaxin-1) regulate critical aspects of eosinophil recruitment, allergic inflammation, and airway hyper-responsiveness (AHR). Among our most important findings, we have provided evidence that the initiation of T_H 2 responses is regulated by airway epithelial cell-derived factors, including TRAIL and MID1, which promote T_H 2 cell development via STAT6-dependent pathways. Further, we highlight studies demonstrating that microRNAs are key regulators of allergic inflammation and potential targets for anti-inflammatory therapy. On the background of T_H 2 inflammation, we have demonstrated that innate immune cells (notably, airway macrophages) play essential roles in the generation of steroid-resistant inflammation and AHR secondary to allergen- and pathogen-induced exacerbations. Our work clearly indicates that understanding the diversity and spatiotemporal role of the inflammatory response and its interactions with resident airway cells is critical to advancing knowledge on asthma pathogenesis and the development of new therapeutic approaches.

Safety of humanized monoclonal antibodies against IL-5 in asthma: focus on reslizumab

INTRODUCTION

Reslizumab, a humanized mAb against IL-5, reduces the number of eosinophils in the blood and lungs. Based on efficacy and safety data from pivotal RCTs, reslizumab had been approved for use as an add-on maintenance treatment of severe asthma with an eosinophilic phenotype in adults who have a history of exacerbations despite receiving their current asthma medicines. Areas covered: Current literature on reslizumab has been reviewed with a specific focus on its safety profile in the treatment of severe asthma. Expert opinion: Large pivotal and supportive trials reinforce the view that reslizumab is well tolerated, with an acceptable safety profile in patients exposed for longer than 2 years. However, no or few data concerning safety in special populations such as smokers, those with immune- and cellular senescence, patients with comorbidities and those receiving multi-drug treatments are available as yet. Furthermore, we need to fully elucidate some fundamental issues such as the risk of anaphylaxis and the long-term risk-benefit ratio of the impact of depletion of eosinophils and the potential risk of malignancies induced by a treatment with this anti-IL-5 agent.

Enhanced antigen presenting and T cell functions during late-phase allergic responses in the lung

BACKGROUND

Allergic inflammation is a common feature of asthma and may contribute to both development and perpetuation of disease. The interaction of antigen-presenting cells (APC) with sensitized helper T lymphocytes (TC) producing Th2 cytokines may determine the inflammatory response. Recruitment of APC and TC to the lung during allergic responses has been demonstrated, but functional studies in humans have been limited.

OBJECTIVE

This study examined the function of APC and TC accumulating at sites of inflammation after segmental allergen challenge (SAC).

METHODS

Fifteen allergic patients underwent SAC, and cells from bronchoalveolar lavage (BAL) were collected after 24 hours. APC and TC from the blood and BAL were purified based on expression of the monocyte marker, CD14; the plasmacytoid dendritic cell (pDC) marker, BDCA4, identifying neuropilin-1 (NRP1); and the helper T cell marker, CD4. Functional activity was assessed using allergen-induced T cell proliferation. Flow cytometry identified cells expressing CD14 and NRP1.

RESULTS

SAC resulted in a 12-fold increase in mononuclear cells having the morphologic appearance of blood monocytes. Most of these cells co-expressed CD14 and NRP1. After saline challenge, BAL mononuclear cells demonstrated little APC function. Following SAC, BAL mononuclear cells showed function equal to pDC from blood and greater than blood monocytes. Purified NRP1⁺ cells from BAL had even greater function than pDC cells from blood (P = .008). Using consistent sources of APC, enhanced proliferation of TC from lung compared to blood was also demonstrated (P = .002).

CONCLUSIONS

The marked increase in APC function for allergen-specific TC proliferation during allergic inflammation is largely due to the recruitment of monocytes and dendritic cells. There is also an enhanced response in the lung TC population, consistent with recruitment of allergen-specific T cells. Interactions between recruited APC and TC may occur as an early event promoting allergic airway inflammation.

The effect of allergen-induced bronchoconstriction on concentration of 5-oxo-ETE in exhaled breath condensate of house dust mite-allergic patients

BACKGROUND

Arachidonic acid metabolites regulate several aspects of airway function including inflammation, muscle contraction and mucous secretion.

OBJECTIVE

The aim of this study was to evaluate concentration of selected 5-lipoxygenase- and cyclooxygenase-derived eicosanoids in exhaled breath condensate (EBC) during allergen-induced bronchoconstriction.

METHODS

The study was performed on 24 allergic rhinitis/asthma patients sensitized to a house dust mite (HDM) Dermatophagoides pteronyssinus (Dp) and 13 healthy controls (HCs). Bronchial challenge with Dp extract was performed only in the allergic patients. EBC samples were collected before (T₀ ) and during Dp-induced bronchoconstriction (T_EAR ). Eicosanoid concentration was measured using HPLC-tandem mass spectrometry.

RESULTS

Significant bronchoconstriction after Dp challenge was demonstrated in 15 patients (Rs), while in 9 patients (NRs) no asthmatic response could be detected. At T₀ the most abundant eicosanoids in EBC of HDM-allergic patients were LTB₄ and 5-oxo-ETE, while in HCs EBC concentration of LTB₄ was significantly greater than that of 5-oxo-ETE. Allergen challenge resulted in significant increase in EBC concentration of 5-oxo-ETE, LTD₄ and 8-iso-PGE₂ only in Rs. At T_EAR , the relative change of 5-oxo-ETE concentration in EBC correlated with decrease of peripheral blood eosinophilia (R = -0.774; P = .0012). Moreover, the relative increase of 5-oxo-ETE in EBC at T_EAR significantly correlated with the severity of the subsequent late asthmatic response (R = 0.683, P = .007).

CONCLUSION

Our study demonstrates significant up-regulation of 5-oxo-ETE synthesis in HDM-allergic patients and indicates possible involvement of that mediator in the pathogenesis of allergic asthma.

miR-155 contributes to Df1-induced asthma by increasing the proliferative response of Th cells via CTLA-4 downregulation

Allergen-induced airway inflammation is characterized by Th2-mediated eosinophilic inflammation in the lungs. While the molecular mechanisms leading to this abnormal Th2 response remain unclear. Recent studies have demonstrated that MicroRNAs (miRNAs) modulate allergic airway inflammation. In this study, the role of miRNAs in allergic asthma pathogenesis was examined. Differentially expressed miRNAs were identified via miRNA microarray, with miR-155 being among the most highly expressed in asthma mice lungs. Examination of miR-155 overexpression resulted in enhanced inflammation and mucus hypersecretion in the lungs of allergen-challenged mice compared with control animals. Furthermore, CTLA-4, an important negative regulator of T-cell activation, was identified as a direct miR-155 target. Moreover, miR-155 overexpression in CD4⁺ T cells resulted in decreased CTLA-4 levels and a subsequent increased proliferative response. Collectively, these findings suggest that miR-155 might contribute to allergic asthma by increasing the proliferative response of Th cells via CTLA-4 downregulation and thus may be a potential therapeutic target for allergic asthma.

Clinical potential of oligonucleotide-based therapeutics in the respiratory system

The discovery of an ever-expanding plethora of coding and non-coding RNAs with nodal and causal roles in the regulation of lung physiology and disease is reinvigorating interest in the clinical utility of the oligonucleotide therapeutic class. This is strongly supported through recent advances in nucleic acids chemistry, synthetic oligonucleotide delivery and viral gene therapy that have succeeded in bringing to market at least three nucleic acid-based drugs. As a consequence, multiple new candidates such as RNA interference modulators, antisense, and splice switching compounds are now progressing through clinical evaluation. Here, manipulation of RNA for the treatment of lung disease is explored, with emphasis on robust pharmacological evidence aligned to the five pillars of drug development: exposure to the appropriate tissue, binding to the desired molecular target, evidence of the expected mode of action, activity in the relevant patient population and commercially viable value proposition.

Cytokine production by PBMC and serum from allergic and non-allergic subjects following in vitro histamine stimulation to test fexofenadine and osthole anti-allergic properties

FXF is a third-generation antihistamine drug and osthole is assumed a natural antihistamine alternative. This paper compares peripheral blood mononuclear cell (PBMC) incubation with FXF and osthole, by studying FXF, osthole and histamine cytokine secretion in PBMC in vitro cultures. Mabtech kits determined the interleukins IL-1β, IL-4, IL-10, IL-13 and TNF-α. The influence of the above active substances on cytokine secretion in PBMC's and serum was assessed: cytokines were IL-1β, IL-4, IL-10, IL-13 and TNF-α; and cytokine levels secreted by untreated PBMCs in pure culture medium formed the absolute control (ctrl). We determined that osthole affects PBMC cytokine secretion to almost precisely the same extent as FXF (IL-1β, IL-4, IL-10 and TNF). In addition osthole had greater IL-13 blocking ability than FXF. Moreover, we observed significantly decreased IL-4 level in histamine/osthole theatment compared to histamine alone. Meanwhile, FXF not significantly decrease the level of IL-4 increased by histamine. This data indicates osthole's strong role in allergic inflamation. All results confirm our hypothesis that osthole is a natural histamine antagonist and therefore can be beneficially used in antihistamine treatment of conditions such as allergies.

Schoolchildren's antioxidation genotypes are susceptible factors for reduced lung function and airway inflammation caused by air pollution

BACKGROUND

We recently reported the relationship between exposure to ambient air pollutants and changes in lung function and nasal inflammation among schoolchildren. A study was conducted to investigate whether antioxidation genotypes influence these associations.

METHODS

A follow-up study of 97 schoolchildren was conducted in New Taipei City, Taiwan. A structured respiratory health questionnaire was administered in September 2007, followed by monthly spirometry and measurement of nasal inflammation from October 2007 to November 2009. During the study period, complete daily monitoring data for air pollutants were obtained from the Environmental Protection Administration monitoring station and Aerosol Supersite. The genotypes of glutathione S-transferase (GST) subunits M1, T1, P1 and superoxide dismutases subunit 2 (SOD2) were characterized. Mixed-effects models were used, adjusting for known confounders.

RESULT

GSTM1 null children had significant PM2.5-related increment in leukocyte (8.52%; 95% confidence interval (CI): 3.13-13.92%) and neutrophil (9.68%; 95% CI: 4.51-14.85%) in nasal lavage. Ozone levels were significantly and inversely associated with forced expiratory flow at 25% of forced vital capacity (FEF25%) (-0.43L/s; 95% CI: -0.58,-0.28L/s) in SOD2 Ala16 variant children.

CONCLUSION

In this longitudinal study of schoolchildren. Our data provide evidence that antioxidation genotype modifies the airway inflammation caused by PM2.5. Antioxidation genotype also acts as an effect modifier, but not strong, in ozone-related small airway function response.

Prostaglandin D2 receptor antagonists in early development as potential therapeutic options for asthma

INTRODUCTION

Asthma is a chronic inflammatory disease characterized by bronchial hyper-reactivity. Although many currently available treatment regimens are effective, poor symptom control and refractory severe disease still represent major unmet needs. In the last years, numerous molecular therapeutic targets that interfere with the innate inflammatory response in asthma have been identified. Promising preliminary results concern the signaling cascade promoted by prostaglandin D2 (PGD2) and its receptor antagonists.

AREAS COVERED

The aim of this review is to provide the most recent clinical and preclinical data on the efficacy and safety of newly developed compounds for the treatment of allergic asthma. The authors will present an overview of the pathogenetic molecular mechanisms sustaining the chronic inflammatory response in asthma; the focus will be then directed on the mediators of the PGD2 pathway, the chemoattractant receptor-homologous molecule expressed on TH2 cells, and their latest antagonists developed.

EXPERT OPINION

Bronchodilators and corticosteroids are not sufficient to achieve a satisfactory management of all asthmatic patients; the development of new specific treatments appears therefore essential. The good results in terms of cellular, functional and clinical outcomes, together with an acceptable safety of the CRTh2 antagonists represent a promising start for a tailored management of allergic asthma.

Anti-asthmatic and anxiolytic effects of Herissantia tiubae, a Brazilian medicinal plant

Herissantia tiubae (HtE) is a Brazilian plant used in folk medicine to treat inflammatory diseases. Our aim was to determine whether the HtE has anti-inflammatory and anxiolytic effects in a murine model of asthma. Ovalbumin (OVA)-sensitized BALB/c mice were treated with HtE (50, 100, or 200 mg/kg) or dexamethasone before each OVA challenge. After the last challenge, animals were subjected to anxiety tests and respiratory measurements. Following euthanasia, we quantified immune cells in the bronchoalveolar lavage (BAL), serum IgE titer and cytokine levels, cellular infiltration and mucus content in the lung tissues, and cellular composition of the mediastinal lymph nodes. OVA challenge in sensitized animals caused: (1) reduction of mean respiratory and dominant respiratory rate (from 398 ± 12 to 286 ± 20 cicles per minute (cpm) and from 320 ± 14 to 162 ± 15 cpm, respectively); (2) increase in behavioral markers of anxiety tests; (3) substantial pro-inflammatory effects, including rise in OVA-specific IgE titer (from 0 to 1:2048) and these inflammatory effect diminished the titer to 1:512 after HtE treatment; rise in plasma IL-13 (from 13 ng/mL in saline to 227 ng/mL in OVA and HtE treatment restored to 1.29 ng/mL; rise in total BAL cell count (from 0.742 cells/mL in saline to 11.77 cells/mL in OVA), with prominent eosinophilia. H. tiubae extract affected respiratory parameters similarly to aminophylline, behavioral changes comparable to diazepam, and inflammation being as efficient as dexamethasone. H. tiubae extract (HtE) possesses both anti-inflammatory and anxiolytic properties in the murine model of asthma.

Efficacy and Safety of Benralizumab, a Monoclonal Antibody against IL-5Rα, in Uncontrolled Eosinophilic Asthma

Nonresponders to maximal guideline-based therapies of asthma account for most of the morbidity, mortality, and economic burden of the disease. Because eosinophils are key effector cells in asthmatic airway inflammation, blocking IL-5, the main cytokine responsible for its survival and activation, seems to be a rational strategy. While previous monoclonal antibodies against the IL-5 ligand resulted in inconsistent improvements in asthma outcomes, benralizumab has shown promise. Benralizumab is a monoclonal antibody against IL-5 receptor, and has an enhanced antibody dependent cell-mediated cytotoxicity function. In this article, we review the theoretical advantages of benralizumab compared to previous compounds, as well as current status of the clinical development of benralizumab in asthma. Lastly, we briefly discuss the potential role of benralizumab in chronic obstructive pulmonary disease.

CD4⁺ and CD8⁺ T cells play a central role in a HDM driven model of allergic asthma

Background

The incidence of asthma is increasing at an alarming rate and while the current available therapies are effective in the majority of patients they fail to adequately control symptoms at the more severe end of the disease spectrum. In the search to understand disease pathogenesis and find effective therapies animal models are often employed. As exposure to house dust mite (HDM) has a causative link, it is thought of as the allergen of choice for modelling asthma.

The objective was to develop a HDM driven model of asthmatic sensitisation and characterise the role of key allergic effector cells/mediators.

Methods

Mice were sensitised with low doses of HDM and then subsequently challenged. Cellular inflammation, IgE and airway responsiveness (AHR) was assessed in wild type mice or CD4⁺/CD8⁺ T cells, B cells or IgE knock out mice.

Results

Only those mice sensitised with HDM responded to subsequent low dose topical challenge. Similar to the classical ovalbumin model, there was no requirement for systemic alum sensitisation. Characterisation of the role of effector cells demonstrated that the allergic cellular inflammation and AHR was dependent on CD4⁺ and CD8⁺ T cells but not B cells or IgE. Finally, we show that this model, unlike the classic OVA model, appears to be resistant to developing tolerance.

Conclusions

This CD4⁺/CD8⁺ T cell dependent, HDM driven model of allergic asthma exhibits key features of asthma. Furthermore, we suggest that the ability to repeat challenge with HDM means this model is amenable to studies exploring the effect of therapeutic dosing in chronic, established disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-016-0359-y) contains supplementary material, which is available to authorized users.

Pristimerin attenuates ovalbumin-induced allergic airway inflammation in mice

Pristimerin has been shown to possess antiinflammatory activity. However, its potential use for asthma induced by airway inflammation has not yet been studied. First, we established a ovalbumin (OVA)-induced allergic asthma mice model. BALB/c mice were immunized and challenged by OVA. Treatment with pristimerin caused a marked reduction in the levels of OVA-specific IgE, immune cells, and IL-4, IL-5, IL-13 secretion. Histological studies using H&E staining were used to study the alterations in lung tissue. These results were similar to those obtained with dexamethasone treatment. We then investigated which signal transduction mechanisms could be implicated in pristimerin activity by Western blot. The data showed that pristimerin could inhibit MAPKs and NF-κB inflammatory pathways.

Interleukin-5 pathway inhibition in the treatment of eosinophilic respiratory disorders: evidence and unmet needs

PURPOSE OF REVIEW

Human eosinophils were first identified and named by Paul Ehrlich in 1879 on the basis of the cell's granular uptake of eosin. Although eosinophils represent approximately 1% of peripheral blood leukocytes, they have the propensity to leave the blood stream and migrate into inflamed tissues. Eosinophils and their mediators are critical effectors to asthma and eosinophilic granulomatosis with polyangiitis (EGPA). Eosinophils are equipped with a large number of cell-surface receptors and produce specific cytokines and chemokines.

RECENT FINDINGS

Eosinophils are the major source of interleukin-5 and highly express the interleukin-5Rα on their surface. Clinical trials evaluating monoclonal antibodies to interleukin-5 (mepolizumab and reslizumab) and its receptor interleukin-5Rα (benralizumab) have been or are underway in patients with eosinophilic asthma, EGPA and chronic obstructive pulmonary disease (COPD). Overall, targeting interleukin-5/interleukin-5Rα is associated with a marked decrease in blood and sputum eosinophilia, the number of exacerbations and improvement of some clinical parameters in adult patients with severe eosinophilic asthma. Pilot studies suggest that mepolizumab might be a glucocorticoid-sparing treatment in patients with EGPA. A preliminary study found that benralizumab did not reduce the exacerbations and did modify lung function in patients with eosinophilic COPD.

SUMMARY

The review examines recent advances in the biology of eosinophils and how targeting the interleukin-5 pathway might offer benefit to some patients with severe asthma, EGPA, and COPD. Interleukin-5/interleukin-5Rα-targeted treatments offer promises to patients with eosinophilic respiratory disorders.

CpG Oligodeoxynucleotide Inhibits Cockroach-Induced Asthma via Induction of IFN-γ⁺ Th1 Cells or Foxp3⁺ Regulatory T Cells in the Lung

Purpose

CpG oligodeoxynucleotide (CpG-ODN), a TLR9 agonist, activates innate immunity and induces Th1 response. Although the immune modulatory effect of CpG-ODN has been extensively studied, its function in cockroach extract-induced allergic asthma has not been studied. Here, we investigated the inhibitory function of CpG-ODN in cockroach extract-induced asthma in mice with different treatment schemes.

Methods

Scheme 1: BALB/C mice were intra-nasally co-administered by cockroach extract and CpG-ODN twice a week for 3 weeks; Scheme 2: The mice were intra-nasally pre-treated with CpG-ODN at day 0 and cockroach allergen challenge was performed from day 3 as in scheme 1. Scheme 3: Cockroach allergen challenge was performed as in scheme 1 and CpG-ODN was post-treated at day 21. Then, BAL cell count, flow cytometric analysis of alveolar macrophages, regulatory T cells, and lung tissue histology, Th1 and Th2 cytokines, serum IgE, cockroach specific IgE, IgG1/IgG2a ratio, and airway hyper-responsiveness were evaluated.

Results

Mice with repeated intra-nasal exposure to CpG-ODN showed a dramatic decrease in eosinophilic inflammation, goblet cell hyperplasia, and airway hyper-responsiveness with reduction of IL-13, IL-5, and serum IgE, cockroach specific IgE and IgG1/IgG2a ratio. This inhibitory function might be related to the up-regulation of IL-10 and CD4⁺Foxp3⁺ regulatory T cells in the lung. Interestingly, one-time challenge of CpG-ODN either prior or posterior to cockroach extract exposure could modulate airway inflammation and hyper-responsiveness via increase of Th1 response.

Conclusions

Collectively, our data suggest that CpG-ODN treatment modulates Th2 inflammation in the lung by induction of regulatory T cells or Th1 response in a cockroach-induced asthma model.

Mepolizumab in the treatment of severe eosinophilic asthma

IL-5 is crucial in the pathogenesis and evolution of eosinophilic asthma. Mepolizumab is a high-affinity humanized monoclonal antibody of the IgG1/k subtype that inhibits the binding of IL-5 to its receptor expressed on eosinophils, thereby inducing significant reduction in eosinophil circulation, as well as asthma exacerbations and corticosteroid treatment. This review deals with the currently available studies of mepolizumab in the treatment of patients with severe eosinophilic asthma.

The past, present, and future of monoclonal antibodies to IL-5 and eosinophilic asthma: a review

Asthma is a heterogeneous syndrome that might be better described as a constellation of phenotypes or endotypes, each with distinct cellular and molecular mechanisms, rather than as a singular disease. One of these phenotypes is eosinophilic asthma. As the development of eosinophilic inflammation is categorically dependent on the biological activity of Interleukin (IL)-5, IL-5 antagonism became an obvious target for therapy in this phenotype. Early trials of monoclonal antibodies targeting the biological activity of IL-5, including reslizumab, mepolizumab, and benralizumab, were performed on asthmatics with no concern for evidence of eosinophilia. These trials were largely unsuccessful. However, during these trials, researchers recognized the need to quantify eosinophilia in asthma subjects in order to identify those asthmatics in whom these medications would be more likely to improve symptoms and lung function. Using biomarkers, such as sputum and blood eosinophilia, recent studies of these medications have shown improvements in blood and sputum eosinophilia, forced expiratory volume in 1 second, and quality of life assessments as well as reducing occurrences of exacerbations. Moving forward, better and less invasive biomarkers of eosinophilia are necessary to ensure that the correct patients are chosen to receive these medications to receive maximal benefit.

CD8+ T Cells Mediate Female-Dominant IL-4 Production and Airway Inflammation in Allergic Asthma

The prevalence and severity of bronchial asthma are higher in females than in males after puberty. Although antigen-specific CD8+ T cells play an important role in the development of asthma through their suppressive effect on cytokine production, the contribution of CD8+ T cells to sex differences in asthmatic responses remains unclear. In the present study, we investigated the sex-specific effect of CD8+ T cells in the suppression of asthma using an ovalbumin mouse model of asthma. The number of inflammatory cells in bronchoalveolar lavage (BAL) fluid, lung type 2 T-helper cytokine levels, and interleukin-4 (IL-4) production by bronchial lymph node cells were significantly higher in female wild-type (WT) mice compared with male mice, whereas no such sex differences were observed between male and female cd8α-disrupted mice. The adaptive transfer of male, but not female, CD8+ T cells reduced the number of inflammatory cells in the recovered BAL fluid of male recipient mice, while no such sex difference in the suppressive activity of CD8+ T cells was observed in female recipient mice. Male CD8+ T cells produced higher levels of IFN-γ than female CD8+ T cells did, and this trend was associated with reduced IL-4 production by male, but not female, CD4+ T cells. Interestingly, IFN-γ receptor expression on CD4+ T cells was significantly lower in female mice than in male mice. These results suggest that female-dominant asthmatic responses are orchestrated by the reduced production of IFN-γ by CD8+ T cells and the lower expression of IFN-γ receptor on CD4+ T cells in females compared with males.

Nebulized fluticasone propionate, a viable alternative to systemic route in the management of childhood moderate asthma attack: A double-blind, double-dummy study

BACKGROUND

In this study, we compared the clinical and immunological efficacy of nebulized corticosteroid (CS) to systemic route during treatment of moderate asthma attack in children.

METHODS

In this randomized, placebo-controlled, double-blind, double-dummy, prospective study, 81 children aged 12 months to 16 years experiencing asthma attack randomized into two treatment groups to receive, either; nebulized fluticasone propionate (n = 39, 2000 mcg/day) or oral methylprednisolone (n = 41, 1 mg/kg/day). Pulmonary index scores (PIS) were assessed at admission and at 1st, 4th, 8th, 12th, 24th, 48th hours, as well as, on day 7 and peak expiratory flow (PEF) at baseline and at the 7th day. Daily symptom and medication scores were recorded for all subjects. Immunological studies included phytohemagglutinin induced peripheral blood mononuclear cells culture supernatant for cytokine responses and CD4(+) CD25(+) FOXP3(+) T regulatory cell (T reg) percentage at baseline and day 7.

RESULTS

The changes in PIS and PEF were similar in both treatment groups, with a significant improvement in both values at the 7th day, when compared to baseline. In both groups, significant reductions in symptom and medication scores were observed during the treatment period with no significant difference between the groups. At day 7 of intervention, phytohemagglutinin induced IL-4 level was significantly decreased only in the nebulized group compared to baseline (p = 0.01). Evaluation of cytokine responses by means of fold increase (stimulated (S)/unstimulated (US) ratio) revealed a significant reduction in IL-4, IL-5 and IL-17 only in nebulized group (p = 0.01, 0.01, 0.02; respectively). The fold increase value of IL-5 was significantly lower at 7th day in nebulized group when compared to systemic one (p = 0.02). At 7th day, although in both treatment groups the percentage of T reg cells was suppressed, it remained significantly higher in the nebule one when compared to systemic route (p = 0.04).

CONCLUSION

In the management of moderate acute asthma attack, nebulized CS (2000 mcg daily) was found to be as effective as systemic route with regard to clinical improvement. In addition, immunological parameters were more in favor of nebulized route which may imply a salutary effect of local CS usage.

The importance of TSLP in allergic disease and its role as a potential therapeutic target

Thymic stromal lymphopoietin (TSLP) is an epithelial-derived cytokine similar to IL- 7, whose gene is located on chromosome 5q22.1 and it exerts its biological function through the TSLP-Receptor (TSLP-R). TSLP is expressed primarily by epithelial cells at barrier surfaces such as the skin, gut and lung in response to danger signals. Since it was cloned in 1994, there has been accumulating evidence that TSLP is crucial for the maturation of antigen presenting cells and hematopoietic cells. TSLP genetic variants and its dysregulated expression have been linked to atopic diseases such as atopic dermatitis, asthma, allergic rhinitis and eosinophilic esophagitis.

CARMA3 Is Critical for the Initiation of Allergic Airway Inflammation

Innate immune responses to allergens by airway epithelial cells (AECs) help initiate and propagate the adaptive immune response associated with allergic airway inflammation in asthma. Activation of the transcription factor NF-κB in AECs by allergens or secondary mediators via G protein-coupled receptors (GPCRs) is an important component of this multifaceted inflammatory cascade. Members of the caspase recruitment domain family of proteins display tissue-specific expression and help mediate NF-κB activity in response to numerous stimuli. We have previously shown that caspase recruitment domain-containing membrane-associated guanylate kinase protein (CARMA)3 is specifically expressed in AECs and mediates NF-κB activation in these cells in response to stimulation with the GPCR agonist lysophosphatidic acid. In this study, we demonstrate that reduced levels of CARMA3 in normal human bronchial epithelial cells decreases the production of proasthmatic mediators in response to a panel of asthma-relevant GPCR ligands such as lysophosphatidic acid, adenosine triphosphate, and allergens that activate GPCRs such as Alternaria alternata and house dust mite. We then show that genetically modified mice with CARMA3-deficient AECs have reduced airway eosinophilia and proinflammatory cytokine production in a murine model of allergic airway inflammation. Additionally, we demonstrate that these mice have impaired dendritic cell maturation in the lung and that dendritic cells from mice with CARMA3-deficient AECs have impaired Ag processing. In conclusion, we show that AEC CARMA3 helps mediate allergic airway inflammation, and that CARMA3 is a critical signaling molecule bridging the innate and adaptive immune responses in the lung.

Exacerbation of atopic dermatitis on grass pollen exposure in an environmental challenge chamber

BACKGROUND

It has frequently been speculated that pruritus and skin lesions develop after topical exposure to aeroallergens in sensitized patients with atopic dermatitis (AD).

OBJECTIVE

We sought to study cutaneous reactions to grass pollen in adult patients with AD with accompanying clear IgE sensitization to grass allergen in an environmental challenge chamber using a monocenter, double-blind, placebo-controlled study design.

METHODS

Subjects were challenged on 2 consecutive days with either 4000 pollen grains/m(3) of Dactylis glomerata pollen or clean air. The severity of AD was assessed at each study visit up to 5 days after challenge by (objective) scoring of AD (SCORAD). Additionally, air-exposed and non-air-exposed skin areas were each scored using local SCORAD scoring and investigator global assessments. Levels of a series of serum cytokines and chemokines were determined by using a Luminex-based immunoassay. The primary end point of the study was the change in objective SCORAD scores between prechallenge and postchallenge values.

RESULTS

Exposure to grass pollen induced a significant worsening of AD. A pronounced eczema flare-up of air-exposed rather than covered skin areas occurred. In grass pollen-exposed subjects a significantly higher increase in CCL17, CCL22, and IL-4 serum levels was observed.

CONCLUSIONS

This study demonstrates that controlled exposure to airborne allergens of patients with a so-called extrinsic IgE-mediated form of AD induced a worsening of cutaneous symptoms.

Protective effect of emodin against airway inflammation in the ovalbumin-induced mouse model

OBJECTIVE

To investigate whether emodin exerts protective effects on mouse with allergic asthma.

METHODS

A mouse model of allergic airway inflflammation was employed. The C57BL/6 mice sensitized and challenged with ovalbumin (OVA) were intraperitoneally administered 10 or 20 mg/kg emodin for 3 days during OVA challenge. Animals were sacrificed 48 h after the last challenge. Inflammatory cell count in the bronchoalveolar lavage fluid (BALF) was measured. The levels of interleukin (IL)-4, IL-5, IL-13 and eotaxin in BALF and level of immunoglobulin E (IgE) in serum were measured with enzyme-linked immuno sorbent assay kits. The mRNA expressions of IL-4, IL-5, heme oxygenase (HO)-1 and matrix metalloproteinase-9 (MMP-9) were determined by real-time quantitative polymerase chain reaction.

RESULTS

Emodin induced significant suppression of the number of OVA-induced total inflammatory cells in BALF. Treatment with emodin led to significant decreases in the levels of IL-4, IL-5, IL-13 and eotaxin in BALF and total IgE level in serum. Histological examination of lung tissue revealed marked attenuation of allergen-induced lung eosinophilic inflammation. Additionally, emodin suppressed IL-4, IL-5 and MMP-9 mRNA expressions and induced HO-1 mRNA expression.

CONCLUSION

Emodin exhibits anti-inflammatory activity in the airway inflammation mouse model, supporting its therapeutic potential for the treatment of allergic bronchial asthma.

Increased frequency of dual-positive TH2/TH17 cells in bronchoalveolar lavage fluid characterizes a population of patients with severe asthma

BACKGROUND

TH2 cells can further differentiate into dual-positive TH2/TH17 cells. The presence of dual-positive TH2/TH17 cells in the airways and their effect on asthma severity are unknown.

OBJECTIVE

We sought to study dual-positive TH2/TH17 cells in bronchoalveolar lavage (BAL) fluid from asthmatic patients, examine their response to glucocorticoids, and define their relevance for disease severity.

METHODS

Bronchoscopy and lavage were performed in 52 asthmatic patients and 25 disease control subjects. TH2 and TH2/TH17 cells were analyzed by using multicolor flow cytometry and confocal immunofluorescence microscopy. Cytokines were assayed by means of ELISA.

RESULTS

Dual-positive TH2/TH17 cells were present at a higher frequency in BAL fluid from asthmatic patients compared with numbers seen in disease control subjects. High-level IL-4 production was typically accompanied by high-level IL-17 production and coexpression of GATA3 and retinoic acid receptor-related orphan receptor γt. Increased presence of TH2/TH17 cells was associated with increased IL-17 production in lavage fluid. TH2/TH17 cell counts and IL-17 production correlated with PC20 for methacholine, eosinophil counts, and FEV1. TH2/TH17 cells, unlike TH2 cells, were resistant to dexamethasone-induced cell death. They expressed higher levels of mitogen-activated protein-extracellular signal-regulated kinase kinase 1, a molecule that induces glucocorticoid resistance. On the basis of the dominance of BAL fluid TH2 or TH2/TH17 cells, we identified 3 subgroups of asthma: TH2(predominant), TH2/TH17(predominant), and TH2/TH17(low). The TH2/TH17(predominant) subgroup manifested the most severe form of asthma, whereas the TH2/TH17(low) subgroup had the mildest asthma.

CONCLUSION

Asthma is associated with a higher frequency of dual-positive TH2/TH17 cells in BAL fluid. The TH2/TH17(predominant) subgroup of asthmatic patients manifested glucocorticoid resistance in vitro. They also had the greatest airway obstruction and hyperreactivity compared with the TH2(predominant) and TH2/TH17(low) subgroups.