Elevated serum IgE, oral corticosteroid dependence and IL-17/22 expression in highly neutrophilic asthma

Asthma Pathogenesis: Phenotypes, Therapies, and Gaps: Summary of the Aspen Lung Conference 2023

Although substantial progress has been made in our understanding of asthma pathogenesis and phenotypes over the nearly 60-year history of the Aspen Lung Conferences on asthma, many ongoing challenges exist in our understanding of the clinical and molecular heterogeneity of the disease and an individual patient's response to therapy. This report summarizes the proceedings of the 2023 Aspen Lung Conference, which was organized to review the clinical and molecular heterogeneity of asthma and to better understand the impact of genetic, environmental, cellular, and molecular influences on disease susceptibility, heterogeneity, and severity. The goals of the conference were to review new information about asthma phenotypes, cellular processes, and cellular signatures underlying disease heterogeneity and treatment response. The report concludes with ongoing gaps in our understanding of asthma pathobiology and provides some recommendations for future research to better understand the clinical and basic mechanisms underlying disease heterogeneity in asthma and to advance the development of new treatments for this growing public health problem.

Airway remodelling in asthma and the epithelium: on the edge of a new era

Asthma is a chronic, heterogeneous disease of the airways, often characterised by structural changes known collectively as airway remodelling. In response to environmental insults, including pathogens, allergens and pollutants, the epithelium can initiate remodelling via an inflammatory cascade involving a variety of mediators that have downstream effects on both structural and immune cells. These mediators include the epithelial cytokines thymic stromal lymphopoietin, interleukin (IL)-33 and IL-25, which facilitate airway remodelling through cross-talk between epithelial cells and fibroblasts, and between mast cells and airway smooth muscle cells, as well as through signalling with immune cells such as macrophages. The epithelium can also initiate airway remodelling independently of inflammation in response to the mechanical stress present during bronchoconstriction. Furthermore, genetic and epigenetic alterations to epithelial components are believed to influence remodelling. Here, we review recent advances in our understanding of the roles of the epithelium and epithelial cytokines in driving airway remodelling, facilitated by developments in genetic sequencing and imaging techniques. We also explore how new and existing therapeutics that target the epithelium and epithelial cytokines could modify airway remodelling.

Dectin-1 aggravates neutrophil inflammation through caspase-11/4-mediated macrophage pyroptosis in asthma

BACKGROUND

The pattern recognition receptor Dectin-1 was initially discovered to play a pivotal role in mediating pulmonary antifungal immunity and promoting neutrophil-driven inflammation. Recent studies have revealed that Dectin-1 is overexpressed in asthma, but the specific mechanism remains elusive. Additionally, Dectin-1 has been implicated in promoting pyroptosis, a hallmark of severe asthma airway inflammation. Nevertheless, the involvement of the non-classical pyroptosis signal caspase-11/4 and its upstream regulatory mechanisms in asthma has not been completely explored.

METHODS

House dust mite (HDM)-induced mice was treated with Dectin-1 agonist Curdlan, Dectin-1 inhibitor Laminarin, and caspase-11 inhibitor wedelolactone separately. Subsequently, inflammatory cells in bronchoalveolar lavage fluid (BALF) were analyzed. Western blotting was performed to measure the protein expression of caspase-11 and gasdermin D (GSDMD). Cell pyroptosis and the expression of chemokine were detected in vitro. The correlation between Dectin-1 expression, pyroptosis factors and neutrophils in the induced sputum of asthma patients was analyzed.

RESULTS

Curdlan appeared to exacerbate neutrophil airway inflammation in asthmatic mice, whereas wedelolactone effectively alleviated airway inflammation aggravated by Curdlan. Moreover, Curdlan enhanced the release of caspase-11 activation fragments and N-terminal fragments of gasdermin D (GSDMD-N) stimulated by HDM both in vivo or in vitro. In mouse alveolar macrophages (MH-S cells), Curdlan/HDM stimulation resulted in vacuolar degeneration and elevated lactate dehydrogenase (LDH) release. In addition, there was an upregulation of neutrophil chemokines CXCL1, CXCL3, CXCL5 and their receptor CXCR2, which was suppressed by wedelolactone. In asthma patients, a positive correlation was observed between the expression of Dectin-1 on macrophages and caspase-4 (the human homology of caspase-11), and the proportion of neutrophils in induced sputum.

CONCLUSION

Dectin-1 activation in asthma induced caspase-11/4 mediated macrophage pyroptosis, which subsequently stimulated the secretion of chemokines, leading to the exacerbation of airway neutrophil inflammation.

New targets for type 2-low asthma

Asthma is characterized by airway obstruction and inflammation, and presents significant diagnostic and treatment challenges. The concept of endotypes has improved understanding of the mechanisms of asthma and has stimulated the development of effective treatment strategies. Sputum profiles may be used to classify asthma into two major inflammatory types: type 2-high (T2H) and type 2-low (T2L) asthma. T2H, characterized by elevated type 2 inflammation, has been extensively studied and several effective biologic treatments have been developed. However, managing T2L is more difficult due to the lack of reliable biomarkers for accurate diagnosis and classification. Additionally, conventional anti-inflammatory therapy does not completely control the symptoms of T2L; therefore, further research is needed to identify effective biologic treatments. This review provides new insights into the clinical characteristics and underlying mechanisms of severe T2L and investigates potential therapeutic approaches to control the disease.

Asthma Inflammatory Phenotypes: How Can We Distinguish Them?

BACKGROUND AND OBJECTIVES

induced sputum is used to assess different inflammatory phenotypes in asthma, but is not used routinely. We aimed to determine the proportion of inflammatory asthma phenotypes based on induced sputum, to find biomarkers that can discriminate between phenotypes, and to evaluate biomarkers in patients with and without biological therapy in different inflammatory asthma phenotypes.

MATERIALS AND METHODS

this cross-sectional study investigated clinical characteristics, asthma control tests, skin prick test, impulse oscillometry (IOS), spirometry, induced sputum, biomarkers (IgE, eosinophils, fractional exhaled nitric oxide (FeNO), serum periostin, IL-5, IL-6, IL-8, IL-17A, IL-33) in 80 asthmatics. A total of 17/80 patients were treated with biologics (10 with omalizumab, 7 with benralizumab).

RESULTS

a total of 31% of patients had eosinophilic asthma (EA), 30% had mixed granulocytic asthma (MGA), 24% had paucigranulocytic asthma (PGA), and 15% had neutrophilic asthma (NA). The difference was found in blood eosinophils (p = 0.002), the highest observed in EA. The cut-off ≥ 240/μL eosinophils, with 64% sensitivity and 72.7% specificity, identified EA (AUC = 0.743, p = 0.001). A higher IL-8 level was associated with NA (p = 0.025). In 63 non-biologic asthma group, eosinophils were higher in EA than in NA, MGA, and PGA (p = 0.012, p = 0.028, and p = 0.049, respectively). A higher IL-17A was associated with EA without biologics (p = 0.004). A significantly higher IL-5 was found in EA treated with biologics, in comparison with EA without biologics (p = 0.043). The number of leucocytes and neutrophils was higher in MGA without biologics (p = 0.049, p = 0.019), while IL-5, IL-6, and IL-8 levels were higher in MGA treated with biologics (p = 0.012, p = 0.032, p = 0.038, respectively).

CONCLUSIONS

EA and MGA were the most prevalent asthma phenotypes. Blood eosinophils can identify EA, both in patients with and without biologics. Apart from the clinical profile, a broad spectrum of biomarkers for assessing inflammatory phenotypes is necessary for an adequate therapy approach to patients with asthma.

Serum Allergen-Specific Immunoglobulin E in Cats with Inflammatory Bronchial Disease

The etiology of feline inflammatory bronchial disease is poorly understood. This study compares the degree of allergen-specific serum IgE responses between cats with feline asthma, chronic bronchitis, mixed inflammation, and clinically healthy cats (HCs). The retrospective case-control study used serum from eighteen cats with eosinophilic inflammation (EI), ten with neutrophilic inflammation (NI), six with mixed inflammation (MI), and fourteen HCs. Affected cats were categorized into groups based on bronchoalveolar lavage cytology. The measurement of IgE for 34 different allergens including fungal organisms, weeds, grasses, trees, mites, and insects was performed using an indirect ELISA. Positive reactions to allergens were detected in the serum of 17/18 cats with EI, 8/10 with NI, 6/6 with MI, and 11/14 HCs (p = 0.364). When overall positive reactions were compared between groups, cats with MI (p = <0.01) had significantly more positive reactions against mite allergens than HCs. Blood eosinophils inversely correlated with the absolute amount of allergen-specific serum IgE expressed in ELISA absorbance units (EAs) (p = 0.014). Sensitization against dust mites seems to be more prevalent in cats with MI. However, positive IgE reactions can be observed in healthy and diseased cats, and, therefore, need to be interpreted in the light of clinical findings and environmental conditions of individual patients.

Smoking, immunity, and cardiovascular prognosis: a study of plasma IgE concentration in patients with acute myocardial infarction

Background

Immunoglobulin E (IgE) is implicated in the pathogenesis of acute myocardial infarction (AMI), and smokers often exhibit elevated plasma IgE levels. However, it remains uncertain whether the role of smoking in the development and prognosis of AMI is influenced by IgE levels. This study aimed to investigate the potential contribution of IgE in mediating the association between smoking and AMI.

Methods

We conducted a prospective study involving 348 consecutive patients with chest discomfort who underwent coronary angiography. Plasma cotinine, an alkaloid present in tobacco, and IgE levels were measured. The patients were followed up for mean 39-months to assess their long-term prognosis based on major adverse cardiac and cerebrovascular events (MACCE).

Results

Our findings indicate that patients with AMI had higher plasma levels of cotinine and IgE. Univariate analyses demonstrated a positive association between plasma cotinine (OR = 1.7, 95% CI: 1.27-2.26, P < 0.001) and IgE (OR = 2.8, 95% CI: 1.75-4.39, P < 0.001) with AMI. Receiver operating characteristics analyses showed that the combined use of cotinine and IgE (AUC: 0.677) had a larger predictive performance compared to cotinine alone (AUC: 0.639) or IgE alone (AUC: 0.657), although the improvement did not reach statistical significance. Multivariable logistic regression revealed a positive association between plasma cotinine and AMI (OR = 1.70, 95% CI: 1.04-2.78, P = 0.036). Furthermore, the inclusion of plasma IgE in the regression model led to a decrease in the OR and 95% CI of plasma cotinine (OR = 1.66, 95% CI: 1.01-2.73, P = 0.048). Process mediation analyses showed a significant indirect effect of plasma cotinine on AMI mediated through increased plasma IgE. Kaplan-Meier analysis during a mean 39-months follow-up revealed that higher plasma levels of IgE were associated with an increased risk of MACCE following AMI (P = 0.047). However, in the context of the COX regression analysis, no significant correlation was observed between IgE, cotinine and AMI.

Conclusion

Cotinine exhibits a positive association with AMI, wherein IgE plays a mediating role. Elevated plasma levels of IgE was positively associated with AMI and poor prognosis, which further confirms the adverse role of smoking on the incidence of AMI and prognosis. (Clinical trial registration: ChiCTR2100053000).

Phenotype overlap in the natural history of asthma

The heterogeneity of asthma makes it challenging to unravel the pathophysiologic mechanisms of the disease. Despite the wealth of research identifying diverse phenotypes, many gaps still remain in our knowledge of the disease's complexity. A crucial aspect is the impact of airborne factors over a lifetime, which often results in a complex overlap of phenotypes associated with type 2 (T2), non-T2 and mixed inflammation. Evidence now shows overlaps between the phenotypes associated with T2, non-T2 and mixed T2/non-T2 inflammation. These interconnections could be induced by different determinants such as recurrent infections, environmental factors, T-helper plasticity and comorbidities, collectively resulting in a complex network of distinct pathways generally considered as mutually exclusive. In this scenario, we need to abandon the concept of asthma as a disease characterised by distinct traits grouped into static segregated categories. It is now evident that there are multiple interplays between the various physiologic, cellular and molecular features of asthma, and the overlap of phenotypes cannot be ignored.

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.

T2-Low Asthma: A Discussed but Still Orphan Disease

Asthma affects 10% of the worldwide population; about 5% of cases are severe with the need for target therapies such as biologics. All the biologics approved for asthma hit the T2 pathway of inflammation. T2-high asthma is classified as allergic and non-allergic, whereas T2-low asthma can be further defined as paucigranulocytic asthma, Type 1 and Type-17 inflammation and the neutrophilic form that accounts for 20-30% of all patients with asthma. Neutrophilic asthma's prevalence is even higher in patients with severe or refractory asthma. We searched Medline and PubMed archives from the past ten years for articles with the subsequent titles: "neutrophilic asthma", "non-type 2 asthma" and "paucigranulocytic asthma". We identified 177 articles; 49 were considered relevant by the title and 33 by the reading of the abstract. Most of these articles are reviews (n = 19); only 6 are clinical trials. No study identified an effective treatment. We used the literature reported by these articles to search for further biologic treatments that target pathways different from T2. We identified 177 articles, 93 of which were considered relevant for the review and included in the present article. In conclusion, T2-low asthma remains poorly investigated in terms of biomarkers, especially as a therapeutic orphan disease.

MAIT cells and the microbiome

Mucosal associated invariant T (MAIT) cells are innate-like T lymphocytes, strikingly enriched at mucosal surfaces and characterized by a semi-invariant αβ T cell receptor (TCR) recognizing microbial derived intermediates of riboflavin synthesis presented by the MHC-Ib molecule MR1. At barrier sites MAIT cells occupy a prime position for interaction with commensal microorganisms, comprising the microbiota. The microbiota is a rich source of riboflavin derived antigens required in early life to promote intra-thymic MAIT cell development and sustain a life-long population of tissue resident cells. A symbiotic relationship is thought to be maintained in health whereby microbes promote maturation and homeostasis, and in turn MAIT cells can engage a TCR-dependent "tissue repair" program in the presence of commensal organisms conducive to sustaining barrier function and integrity of the microbial community. MAIT cell activation can be induced in a MR1-TCR dependent manner or through MR1-TCR independent mechanisms via pro-inflammatory cytokines interleukin (IL)-12/-15/-18 and type I interferon. MAIT cells provide immunity against bacterial, fungal and viral pathogens. However, MAIT cells may have deleterious effects through insufficient or exacerbated effector activity and have been implicated in autoimmune, inflammatory and allergic conditions in which microbial dysbiosis is a shared feature. In this review we summarize the current knowledge on the role of the microbiota in the development and maintenance of circulating and tissue resident MAIT cells. We also explore how microbial dysbiosis, alongside changes in intestinal permeability and imbalance between pro- and anti-inflammatory components of the immune response are together involved in the potential pathogenicity of MAIT cells. Whilst there have been significant improvements in our understanding of how the microbiota shapes MAIT cell function, human data are relatively lacking, and it remains unknown if MAIT cells can conversely influence the composition of the microbiota. We speculate whether, in a human population, differences in microbiomes might account for the heterogeneity observed in MAIT cell frequency across mucosal sites or between individuals, and response to therapies targeting T cells. Moreover, we speculate whether manipulation of the microbiota, or harnessing MAIT cell ligands within the gut or disease-specific sites could offer novel therapeutic strategies.

Exploring proteomic plasma biomarkers in eosinophilic and neutrophilic asthma

BACKGROUND

Few biomarkers identify eosinophilic and neutrophilic asthma beyond cell concentrations in blood or sputum. Finding novel biomarkers for asthma endotypes could give insight about disease mechanisms and guide tailored treatment. Our aim was to investigate clinical characteristics and inflammation-related plasma proteins in relation to blood eosinophil and neutrophil concentrations in subjects with and without asthma.

METHODS

We included 24-26-year-old subjects (n = 2063) from the Swedish population-based cohort BAMSE. Subjects with asthma (n = 239) and without asthma (n = 1824) were subdivided based on blood eosinophil and neutrophil concentrations (cut-offs 0.3 × 10⁹ /L and 5.0 × 10⁹ /L, respectively). We measured the levels of 92 plasma proteins using Olink Proseek Multiplex Inflammation Panel Assay. Group statistics tests were used to analyse the data, as well as adjusted multiple logistic regression models.

RESULTS

Among subjects with asthma, 21.8% had eosinophilic asthma and 20.5% neutrophilic asthma. Eosinophilic asthma, but not neutrophilic asthma, was associated with a distinct clinical phenotype with, for example, higher proportions of eczema and sensitization. Most plasma proteins that associated with high eosinophil and/or neutrophil blood concentrations in subjects with asthma showed similar associations in subjects without asthma. However, out of these proteins, MMP10 levels were associated with eosinophilic asthma and were significantly higher as compared to controls with high eosinophilic concentration, while CCL4 levels associated with high neutrophil concentration only in subjects with asthma.

CONCLUSIONS

Eosinophilic asthma was associated with a clear clinical phenotype. With our definitions, we identified MMP10 as a possible plasma biomarker for eosinophilic asthma and CCL4 was linked to neutrophilic asthma. These proteins should be evaluated further in clinical settings and using sputum granulocytes to define the asthma endotypes.

Transcriptome-wide association study of circulating IgE levels identifies novel targets for asthma and allergic diseases

Measurement of circulating immunoglobulin E (IgE) concentration is helpful for diagnosing and treating asthma and allergic diseases. Identifying gene expression signatures associated with IgE might elucidate novel pathways for IgE regulation. To this end, we performed a discovery transcriptome-wide association study to identify differentially expressed genes associated with circulating IgE levels in whole-blood derived RNA from 5,345 participants in the Framingham Heart Study across 17,873 mRNA gene-level transcripts. We identified 216 significant transcripts at a false discovery rate <0.05. We conducted replication using the meta-analysis of two independent external studies: the Childhood Asthma Management Program (n=610) and the Genetic Epidemiology of Asthma in Costa Rica Study (n=326); we then reversed the discovery and replication cohorts, which revealed 59 significant genes that replicated in both directions. Gene ontology analysis revealed that many of these genes were implicated in immune function pathways, including defense response, inflammatory response, and cytokine production. Mendelian randomization (MR) analysis revealed four genes (CLC, CCDC21, S100A13, and GCNT1) as putatively causal (p<0.05) regulators of IgE levels. GCNT1 (beta=1.5, p=0.01)-which is a top result in the MR analysis of expression in relation to asthma and allergic diseases-plays a role in regulating T helper type 1 cell homing, lymphocyte trafficking, and B cell differentiation. Our findings build upon prior knowledge of IgE regulation and provide a deeper understanding of underlying molecular mechanisms. The IgE-associated genes that we identified-particularly those implicated in MR analysis-can be explored as promising therapeutic targets for asthma and IgE-related diseases.

The Pathology of Asthma: What Is Obstructing Our View?

Despite the advent of sophisticated and efficient new biologics to treat inflammation in asthma, the disease persists. Even following treatment, many patients still experience the well-known symptoms of wheezing, shortness of breath, and coughing. What are we missing? Here we examine the evidence that mucus plugs contribute to a substantial portion of disease, not only by physically obstructing the airways but also by perpetuating inflammation. In this way, mucus plugs may act as an immunogenic stimulus even in the absence of allergen or with the use of current therapeutics. The alterations of several parameters of mucus biology, driven by type 2 inflammation, result in sticky and tenacious sputum, which represents a potent threat, first due to the difficulties in expectoration and second by acting as a platform for viral, bacterial, or fungal colonization that allows exacerbations. Therefore, in this way, mucus plugs are an overlooked but critical feature of asthmatic airway disease.

Tiotropium Bromide Improves Neutrophilic Asthma by Recovering Histone Deacetylase 2 Activity

BACKGROUND

The value of tiotropium bromide (TIO) in neutrophilic asthma was meaningful in previous study. We hypothesized that TIO's mechanism of action is associated with histone deacetylase 2 (HDAC2) activity, which is key for controlling the transcription of inflammatory cytokines and usually downregulated in neutrophilic asthma.

METHODS

The effects of TIO and dexamethasone (DEX) on HDAC2 activity, nuclear factor kappa B (NF-κB), and C-X-C motif chemokine ligand 1 (CXCL1) were evaluated in neutrophilic asthma mouse model (C57BL, 6-week-old). An in-vitro study was conducted using primary human bronchial/tracheal epithelial (HBE) cells from asthma patients. Western blot analyses were performed for phospho-phospholipase Cγ-1 (PLCγ-1) and inositol trisphosphate (IP₃) receptors (IP₃R) with treating lipopolysaccharide (LPS) and TIO.

RESULTS

Ovalbumin was used to induce eosinophilic inflammation in this study. After neutrophilic asthma was induced by LPS (O+L group), HDAC2 activity was diminished with increased NF-κB activity and CXCL1 compared to the control group. TIO significantly improved NF-κB activity, CXCL1, and HDAC2 activity compared with the O+L group in in-vivo study (P < 0.05, each). Western blot analyses showed that LPS treated HBE cells from asthma patients increased PLCγ-1 and diminished IP₃ receptor levels. After TIO treatment, recovery of IP₃R and improved PLCγ-1 levels were observed.

CONCLUSION

These results support the hypothesis that TIO modulates inflammation by recovering HDAC2 activity from the acetylcholine-stimulated inflammation cascade in neutrophilic asthma. The detailed inflammation cascade of recovering HDAC2 activity by TIO might be associated with PLCγ-1-IP₃-IP₃R mediated intracellular calcium ion pathway.

Non-typeable Haemophilus influenzae airways infection: the next treatable trait in asthma?

Asthma is a complex, heterogeneous condition that affects over 350 million people globally. It is characterised by bronchial hyperreactivity and airways inflammation. A subset display marked airway neutrophilia, associated with worse lung function, higher morbidity and poor response to treatment. In these individuals, recent metagenomic studies have identified persistent bacterial infection, particularly with non-encapsulated strains of the Gram-negative bacterium Haemophilus influenzae. Here we review knowledge of non-typeable H. influenzae (NTHi) in the microbiology of asthma, the immune consequences of mucosal NTHi infection, various immune evasion mechanisms, and the clinical implications of NTHi infection for phenotyping and targeted therapies in neutrophilic asthma. Airway neutrophilia is associated with production of neutrophil chemokines and proinflammatory cytokines in the airways, including interleukin (IL)-1β, IL-6, IL-8, IL-12, IL-17A and tumour necrosis factor. NTHi adheres to and invades the lower respiratory tract epithelium, inducing the NLR family pyrin domain containing 3 (NLRP3) and absent in melanoma 2 (AIM2) inflammasomes. NTHi reduces expression of tight-junction proteins, impairing epithelial integrity, and can persist intracellularly. NTHi interacts with rhinoviruses synergistically via upregulation of intracellular cell adhesion molecule 1 and promotion of a neutrophilic environment, to which NTHi is adapted. We highlight the clinical relevance of this emerging pathogen and its relevance for the efficacy of long-term macrolide therapy in airways diseases, we identify important unanswered questions and we propose future directions for research.

IL-17 Cytokines and Chronic Lung Diseases

IL-17 cytokines are expressed by numerous cells (e.g., gamma delta (γδ) T, innate lymphoid (ILC), Th17, epithelial cells). They contribute to the elimination of bacteria through the induction of cytokines and chemokines which mediate the recruitment of inflammatory cells to the site of infection. However, IL-17-driven inflammation also likely promotes the progression of chronic lung diseases, such as chronic obstructive pulmonary disease (COPD), lung cancer, cystic fibrosis, and asthma. In this review, we highlight the role of IL-17 cytokines in chronic lung diseases.

Identifying Bacterial Airways Infection in Stable Severe Asthma Using Oxford Nanopore Sequencing Technologies

Previous metagenomic studies in asthma have been limited by inadequate sequencing depth for species-level bacterial identification and by heterogeneity in clinical phenotyping. We hypothesize that chronic bacterial airways infection is a key "treatable trait" whose prevalence, clinical phenotype and reliable biomarkers need definition. In this study, we have applied a method for Oxford Nanopore sequencing for the unbiased metagenomic characterization of severe asthma. We optimized methods to compare performance of Illumina MiSeq, Nanopore sequencing, and RT-qPCR on total sputum DNA extracts against culture/MALDI-TOF for analysis of induced sputum samples from highly phenotyped severe asthma during clinical stability. In participants with severe asthma (n = 23) H. influenzae was commonly cultured (n = 8) and identified as the dominant bacterial species by metagenomic sequencing using an optimized method for Illumina MiSeq and Oxford Nanopore. Alongside superior operational characteristics, Oxford Nanopore achieved near complete genome coverage of H. influenzae and demonstrated a high level of agreement with Illumina MiSeq data. Clinically significant infection was confirmed with validated H. influenzae plasmid-based quantitative PCR assay. H. influenzae positive patients were found to have sputum neutrophilia and lower FeNO. In conclusion, using an optimized method of direct sequencing of induced sputum samples, H. influenzae was identified as a clinically relevant pathogen in severe asthma and was identified reliably using metagenomic sequencing. Application of these protocols in ongoing analysis of large patient cohorts will allow full characterization of this clinical phenotype. IMPORTANCE The human airways were once thought sterile in health. Now metagenomic techniques suggest bacteria may be present, but their role in asthma is not understood. Traditional culture lacks sensitivity and current sequencing techniques are limited by operational problems and limited ability to identify pathogens at species level. We optimized a new sequencing technique-Oxford Nanopore technologies (ONT)-for use on human sputum samples and compared it with existing methods. We found ONT was effective for rapidly analyzing samples and could identify bacteria at the species level. We used this to show Haemophilus influenzae was a dominant bacterium in the airways in people with severe asthma. The presence of Haemophilus was associated with a "neutrophilic" form of asthma - a subgroup for which we currently lack specific treatments. Therefore, this technique could be used to target chronic antibiotic therapy and in research to characterize the full breadth of bacteria in the airways.

Chemokine Expression-Based Endotype Clustering of Chronic Rhinosinusitis

Chronic rhinosinusitis (CRS) with (CRSwNP) or without nasal polyps (CRSsNP) is a persistent, heterogeneous inflammatory condition affecting the upper respiratory tract. The present study aimed to improve the characterization of CRS endotypes based on the chemokine and cytokine expression pattern in the CRS tissues. Concentrations of chemokines and cytokines were measured in tissues from nasal biopsies obtained from 66 CRS patients and 25 control subjects using multiplexing or single analyte technologies. Cluster analysis based on the concentration of type-1 (MCP-3/CCL7, MIP-1 α/CCL3), type-2 (IL-5, MCP-3/CCL7, MIP-1 α/CCL3, TARC/CCL17, PARC/CCL18, IP-10/CXCL10, ECP), and type-3 (IL-22) chemokines and cytokines identified six CRS endotypes (clusters). Cluster 1 (type-3) and 2 (type-1) were associated with a low prevalence of nasal polyps, Cluster 3 (type-1, -2, -3) and Cluster 4 (type-2, -3, medium IL-22) with medium, and Cluster 5 (type-2, -3, high Il-22) and Cluster 6 (type-2) with high prevalence of nasal polyps. Asthma was highly prevalent in Cluster-6. Our findings add to the existing knowledge of CRS endotypes and may be useful for the clinical decision-making process. The advancement of biologics therapy for upper respiratory tract disorders rationalizes the personalized diagnostic approach to warrant a successful treatment and monitoring of CRS.

Innate Lymphoid Cells Are Required to Induce Airway Hyperreactivity in a Murine Neutrophilic Asthma Model

Rationale

Non-allergic asthma is driven by multiple endotypes of which neutrophilic and pauci-granulocytic asthma have been best established. However, it is still puzzling what drives inflammation and airway hyperreactivity (AHR) in these patients and how it can be treated effectively. Recently, a potential role of the innate immune system and especially the innate lymphoid cells (ILC) has been proposed.

Objective

In this study, we investigated the effects of LPS inhalation on airway inflammation and AHR as a potential model for elucidating the pathogenesis of non-allergic asthma.

Methods

Wild-type (BALB/c), SCID, IL-17A^-/-, and Rag2^-/- γC^-/- mice were endonasally exposed to lipopolysaccharide (LPS, 2 µg) on four consecutive days. Twenty-four hours after the last exposure, AHR to methacholine was assessed. Cytokine levels and ILC subpopulations were determined in lung tissue. Cellular differential analysis was performed in BAL fluid.

Main Results

In this study, we developed a murine model for non-allergic neutrophilic asthma. We found that repeated endonasal applications of low-dose LPS in BALB/c mice led to AHR, BAL neutrophilia, and a significant increase in lung ILC3 as well as a significant increase in lung chemokines KC and MIP-2 and cytokines IL-1β, IL-17A, IL-22, and TNF. The adoptive transfer of ILC in Rag2^-/- γC^-/- mice showed that ILC played a causal role in the induction of AHR in this model. Antagonising IL-1β, but not IL-17A or neutrophils, resulted in a partial reduction in LPS-induced AHR.

Conclusion

In conclusion, we report here a murine model for neutrophilic asthma where ILC are required to induce airway hyperreactivity.

Role of Th17 Cytokines in Airway Remodeling in Asthma and Therapy Perspectives

Airway remodeling is a frequent pathological feature of severe asthma leading to permanent airway obstruction in up to 50% of cases and to respiratory disability. Although structural changes related to airway remodeling are well-characterized, immunological processes triggering and maintaining this phenomenon are still poorly understood. As a consequence, no biotherapy targeting cytokines are currently efficient to treat airway remodeling and only bronchial thermoplasty may have an effect on bronchial nerves and smooth muscles with uncertain clinical relevance. Th17 cytokines, including interleukin (IL)-17 and IL-22, play a role in neutrophilic inflammation in severe asthma and may be involved in airway remodeling. Indeed, IL-17 is increased in sputum from severe asthmatic patients, induces the expression of "profibrotic" cytokines by epithelial, endothelial cells and fibroblasts, and provokes human airway smooth muscle cell migration in in vitro studies. IL-22 is also increased in asthmatic samples, promotes myofibroblast differentiation, epithelial-mesenchymal transition and proliferation and migration of smooth muscle cells in vitro. Accordingly, we also found high levels of IL-17 and IL-22 in a mouse model of dog-allergen induced asthma characterized by a strong airway remodeling. Clinical trials found no effect of therapy targeting IL-17 in an unselected population of asthmatic patients but showed a potential benefit in a sub-population of patients exhibiting a high level of airway reversibility, suggesting a potential role on airway remodeling. Anti-IL-22 therapies have not been evaluated in asthma yet but were demonstrated efficient in severe atopic dermatitis including an effect on skin remodeling. In this review, we will address the role of Th17 cytokines in airway remodeling through data from in vitro, in vivo and translational studies, and examine the potential place of Th17-targeting therapies in the treatment of asthma with airway remodeling.

TH17 cells and corticosteroid insensitivity in severe asthma

Asthma is classically described as having either a type 2 (T2) eosinophilic phenotype or a non-T2 neutrophilic phenotype. T2 asthma usually responds to classical bronchodilation therapy and corticosteroid treatment. Non-T2 neutrophilic asthma is often more severe. Patients with non-T2 asthma or late-onset T2 asthma show poor response to the currently available anti-inflammatory therapies. These therapeutic failures result in increased morbidity and cost associated with asthma and pose a major health care problem. Recent evidence suggests that some non-T2 asthma is associated with elevated T_H17 cell immune responses. T_H17 cells producing Il-17A and IL-17F are involved in the neutrophilic inflammation and airway remodeling processes in severe asthma and have been suggested to contribute to the development of subsets of corticosteroid-insensitive asthma. This review explores the pathologic role of T_H17 cells in corticosteroid insensitivity of severe asthma and potential targets to treat this endotype of asthma.

FGF2 is overexpressed in asthma and promotes airway inflammation through the FGFR/MAPK/NF-κB pathway in airway epithelial cells

BACKGROUND

Airway inflammation is the core pathological process of asthma, with the key inflammatory regulators incompletely defined. Recently, fibroblast growth factor 2 (FGF2) has been reported to be an inflammatory regulator; however, its role in asthma remains elusive. This study aimed to investigate the immunomodulatory role of FGF2 in asthma.

METHODS

First, FGF2 expression was characterised in clinical asthma samples and the house dust mite (HDM)-induced mouse chronic asthma model. Second, recombinant mouse FGF2 (rm-FGF2) protein was intranasally delivered to determine the effect of FGF2 on airway inflammatory cell infiltration. Third, human airway epithelium-derived A549 cells were stimulated with either HDM or recombinant human interleukin-1β (IL-1β) protein combined with or without recombinant human FGF2. IL-1β-induced IL-6 or IL-8 release levels were determined using enzyme-linked immunosorbent assay, and the involved signalling transduction was explored via Western blotting.

RESULTS

Compared with the control groups, the FGF2 protein levels were significantly upregulated in the bronchial epithelium and alveolar areas of clinical asthma samples (6.70 ± 1.79 vs. 16.32 ± 2.40, P = 0.0184; 11.20 ± 2.11 vs. 21.00 ± 3.00, P = 0.033, respectively) and HDM-induced asthmatic mouse lung lysates (1.00 ± 0.15 vs. 5.14 ± 0.42, P < 0.001). Moreover, FGF2 protein abundance was positively correlated with serum total and anti-HDM IgE levels in the HDM-induced chronic asthma model (R² = 0.857 and 0.783, P = 0.0008 and 0.0043, respectively). Elevated FGF2 protein was mainly expressed in asthmatic bronchial epithelium and alveolar areas and partly co-localised with infiltrated inflammatory cell populations in HDM-induced asthmatic mice. More importantly, intranasal instillation of rm-FGF2 aggravated airway inflammatory cell infiltration (2.45 ± 0.09 vs. 2.88 ± 0.14, P = 0.0288) and recruited more subepithelial neutrophils after HDM challenge [(110.20 ± 29.43) cells/mm² vs. (238.10 ± 42.77) cells/mm², P = 0.0392] without affecting serum IgE levels and Th2 cytokine transcription. In A549 cells, FGF2 was upregulated through HDM stimulation and promoted IL-1β-induced IL-6 or IL-8 release levels (up to 1.41 ± 0.12- or 1.44 ± 0.14-fold change vs. IL-1β alone groups, P = 0.001 or 0.0344, respectively). The pro-inflammatory effect of FGF2 is likely mediated through the fibroblast growth factor receptor (FGFR)/mitogen-activated protein kinase (MAPK)/nuclear factor kappa B (NF-κB) pathway.

CONCLUSION

Our findings suggest that FGF2 is a potential inflammatory modulator in asthma, which can be induced by HDM and acts through the FGFR/MAPK/NF-κB pathway in the airway epithelial cells.

Mapping atopic dermatitis and anti-IL-22 response signatures to type 2-low severe neutrophilic asthma

BACKGROUND

Transcriptomic changes in patients who respond clinically to biological therapies may identify responses in other tissues or diseases.

OBJECTIVE

We sought to determine whether a disease signature identified in atopic dermatitis (AD) is seen in adults with severe asthma and whether a transcriptomic signature for patients with AD who respond clinically to anti-IL-22 (fezakinumab [FZ]) is enriched in severe asthma.

METHODS

An AD disease signature was obtained from analysis of differentially expressed genes between AD lesional and nonlesional skin biopsies. Differentially expressed genes from lesional skin from therapeutic superresponders before and after 12 weeks of FZ treatment defined the FZ-response signature. Gene set variation analysis was used to produce enrichment scores of AD and FZ-response signatures in the Unbiased Biomarkers for the Prediction of Respiratory Disease Outcomes asthma cohort.

RESULTS

The AD disease signature (112 upregulated genes) encompassing inflammatory, T-cell, TH2, and TH17/TH22 pathways was enriched in the blood and sputum of patients with asthma with increasing severity. Patients with asthma with sputum neutrophilia and mixed granulocyte phenotypes were the most enriched (P < .05). The FZ-response signature (296 downregulated genes) was enriched in asthmatic blood (P < .05) and particularly in neutrophilic and mixed granulocytic sputum (P < .05). These data were confirmed in sputum of the Airway Disease Endotyping for Personalized Therapeutics cohort. IL-22 mRNA across tissues did not correlate with FZ-response enrichment scores, but this response signature correlated with TH22/IL-22 pathways.

CONCLUSIONS

The FZ-response signature in AD identifies severe neutrophilic asthmatic patients as potential responders to FZ therapy. This approach will help identify patients for future asthma clinical trials of drugs used successfully in other chronic diseases.

Which Therapy for Non-Type(T)2/T2-Low Asthma

Currently, the asthmatic population is divided into Type 2-high and non-Type 2/Type 2-low asthmatics, with 50% of patients belonging to one of the two groups. Differently from T2-high, T2-low asthma has not been clearly defined yet, and the T2-low patients are identified on the basis of the absence or non-predominant expression of T2-high biomarkers. The information about the molecular mechanisms underpinning T2-low asthma is scarce, but researchers have recognized as T2-low endotypes type 1 and type 3 immune response, and remodeling events occurring without inflammatory processes. In addition, the lack of agreed biomarkers reprents a challenge for the research of an effective therapy. The first-choice medication is represented by inhaled corticosteroids despite a low efficacy is reported for/in T2-low patients. However, macrolides and long-acting anti-muscarinic drugs have been recognized as efficacious. In recent years, clinical trials targeting biomarkers playing key roles in T3 and T1 immune pathways, alarmins, and molecules involved in neutrophil recruitment have provided conflicting results probably misleading (or biased) in patients' selection. However, further studies are warranted to achieve a precise characterization of T2-low asthma with the aim of defining a tailored therapy for each single asthmatic patient.

Systemic and local cytokine profile and risk factors for persistent allergic airway inflammation in patients sensitised to house dust mite allergens

Objective

To evaluate cytokine profile, vitamin D status, symptom score and quality of life in patients with persistent allergic airway diseases sensitised to house dust mites (HDM) in comparison with healthy individuals.

Material and methods

Patients sensitized to HDM with persistent AR and having symptoms for at least 2 years with or without AA were involved into the study. Measurements of vitamin D level in serum and IL-10, IL-13, IL-17, IL-22, IL-33 and IFN-gamma in serum and nasal lavage were performed by ELISA.

Results

Eighty-one subjects were involved into the study. Serum IL-10 concentration was higher in patients with AR than in patients with AR and AA (6.71 ± 1.73 vs. 1.98 ± 0.24, p < 0.05). IFN-gamma level in nasal lavage was higher in patients with AR and AA than in patients with AR (p < 0.01) and healthy individuals (p < 0.05) (7.50 ± 0.37 vs. 6.80 ± 0.99 vs. 6.50 ± 0.22). Serum IL-22 negatively correlated with IL-22 in nasal lavage, whereas serum IFN-gamma positively correlated with IFN-gamma in nasal lavage. Positive correlation between serum IL-17 and total IgE and negative correlation between IL-17 in nasal lavage and eosinophils in nasal smear were found in patients with AR and AA. Serum IFN-gamma decreased the risk of AR for healthy individuals. Serum IL-10 and vitamin D decreased risk for development of AA for patients with AR. IL-22 in serum and IL-10 and IL-33 in nasal lavage increased this risk.

Conclusion

Novel cytokines such as IL-22, IL-17 and IL-33 and vitamin D may be involved in pathogenesis of persistent airway inflammation in patients sensitized to HDM.

Pulmonary Eosinophils at the Center of the Allergic Space-Time Continuum

Eosinophils are typically a minority population of circulating granulocytes being released from the bone-marrow as terminally differentiated cells. Besides their function in the defense against parasites and in promoting allergic airway inflammation, regulatory functions have now been attributed to eosinophils in various organs. Although eosinophils are involved in the inflammatory response to allergens, it remains unclear whether they are drivers of the asthma pathology or merely recruited effector cells. Recent findings highlight the homeostatic and pro-resolving capacity of eosinophils and raise the question at what point in time their function is regulated. Similarly, eosinophils from different physical locations display phenotypic and functional diversity. However, it remains unclear whether eosinophil plasticity remains as they develop and travel from the bone marrow to the tissue, in homeostasis or during inflammation. In the tissue, eosinophils of different ages and origin along the inflammatory trajectory may exhibit functional diversity as circumstances change. Herein, we outline the inflammatory time line of allergic airway inflammation from acute, late, adaptive to chronic processes. We summarize the function of the eosinophils in regards to their resident localization and time of recruitment to the lung, in all stages of the inflammatory response. In all, we argue that immunological differences in eosinophils are a function of time and space as the allergic inflammatory response is initiated and resolved.

Interleukin-22 attenuates allergic airway inflammation in ovalbumin-induced asthma mouse model

BACKGROUND

Allergic asthma is a chronic airway inflammatory disease with a number of cytokines participating in its pathogenesis and progress. Interleukin (IL)-22, which is derived from lymphocytes, acts on epithelial cells and play a role in the chronic airway inflammation. However, the actual role of IL-22 in allergic asthma is still unclear. Therefore, we explored the effect of IL-22 on allergic airway inflammation and airway hyperresponsiveness (AHR) in an ovalbumin (OVA)-induced asthma mouse model.

METHODS

To evaluate the effect of IL-22 in an allergic asthma model, BALB/c mice were sensitized and challenged with OVA; then the recombinant mouse IL-22 was administered intranasally 24 h prior to each challenge. The IL-22 levels in lung homogenates and bronchoalveolar lavage fluid (BALF) were measured by enzyme linked immunosorbent assay, respectively. AHR was evaluated through indicators including airways resistance (Rrs), elastance (Ers) and compliance (Crs); the inflammatory cell infiltration was assessed by quantification of differential cells counts in BALF and lung tissues stained by hematoxylin and eosin (H&E); IL-22 specific receptors were determined by immunohistochemistry staining.

RESULTS

The concentration of IL-22 was significantly elevated in the OVA-induced mice compared with the control mice in lung homogenates and BALF. In the OVA-induced mouse model, IL-22 administration could significantly attenuate AHR, including Rrs, Ers and Crs, decrease the proportion of eosinophils in BALF and reduce inflammatory cell infiltration around bronchi and their concomitant vessels, compared with the OVA-induced group. In addition, the expression of IL-22RA1 and IL-10RB in the lung tissues of OVA-induced mice was significantly increased compared with the control mice, while it was dramatically decreased after the treatment with IL-22, but not completely attenuated in the IL-22-treated mice when compared with the control mice.

CONCLUSION

Interleukin-22 could play a protective role in an OVA-induced asthma model, by suppressing the inflammatory cell infiltration around bronchi and their concomitant vessels and airway hyperresponsiveness, which might associate with the expression of its heterodimer receptors. Thus, IL-22 administration might be an effective strategy to attenuate allergic airway inflammation.

Characterization of T2-Low and T2-High Asthma Phenotypes in Real-Life

Asthma is a heterogeneous and complex condition characterized by chronic airway inflammation, which may be clinically stratified into three main phenotypes: type 2 (T2) low, T2-high allergic, and T2-high non-allergic asthma. This real-world study investigated whether phenotyping patients with asthma using non-invasive parameters could be feasible to characterize the T2-low and T2-high asthma phenotypes in clinical practice. This cross-sectional observational study involved asthmatic outpatients (n = 503) referring to the Severe Asthma Centre of the San Luigi Gonzaga University Hospital. Participants were stratified according to the patterns of T2 inflammation and atopic sensitization. Among outpatients, 98 (19.5%) patients had T2-low asthma, 127 (25.2%) T2-high non-allergic, and 278 (55.3%) had T2-high allergic phenotype. In comparison to T2-low, allergic patients were younger (OR 0.945, p < 0.001) and thinner (OR 0.913, p < 0.001), had lower smoke exposure (OR 0.975, p < 0.001) and RV/TLC% (OR 0.950, p < 0.001), higher prevalence of asthma severity grade 5 (OR 2.236, p < 0.05), more frequent rhinitis (OR 3.491, p < 0.001) and chronic rhinosinusitis with (OR 2.650, p < 0.001) or without (OR 1.919, p < 0.05) nasal polyps, but less common arterial hypertension (OR 0.331, p < 0.001). T2-high non-allergic patients had intermediate characteristics. Non-invasive phenotyping of asthmatic patients is possible in clinical practice. Identifying characteristics in the three main asthma phenotypes could pave the way for further investigations on useful biomarkers for precision medicine.

The Role of Innate Lymphoid Cells in Chronic Respiratory Diseases

The lung is a vital mucosal organ that is constantly exposed to the external environment, and as such, its defenses are continuously under threat. The pulmonary immune system has evolved to sense and respond to these danger signals while remaining silent to innocuous aeroantigens. The origin of the defense system is the respiratory epithelium, which responds rapidly to insults by the production of an array of mediators that initiate protection by directly killing microbes, activating tissue-resident immune cells and recruiting leukocytes from the blood. At the steady-state, the lung comprises a large collection of leukocytes, amongst which are specialized cells of lymphoid origin known as innate lymphoid cells (ILCs). ILCs are divided into three major helper-like subsets, ILC1, ILC2 and ILC3, which are considered the innate counterparts of type 1, 2 and 17 T helper cells, respectively, in addition to natural killer cells and lymphoid tissue inducer cells. Although ILCs represent a small fraction of the pulmonary immune system, they play an important role in early responses to pathogens and facilitate the acquisition of adaptive immunity. However, it is now also emerging that these cells are active participants in the development of chronic lung diseases. In this mini-review, we provide an update on our current understanding of the role of ILCs and their regulation in the lung. We summarise how these cells and their mediators initiate, sustain and potentially control pulmonary inflammation, and their contribution to the respiratory diseases chronic obstructive pulmonary disease (COPD) and asthma.

Reduced CCR6+IL-17A+Treg Cells in Blood and CCR6-Dependent Accumulation of IL-17A+Treg Cells in Lungs of Patients With Allergic Asthma

Human regulatory T (Treg) cells play a central role in controlling allergic inflammation in the airways. A reduced number of peripheral Treg cells and decreased suppressive function have been previously reported in the pathogenesis of allergic asthma. However, the characteristic role of specific Treg cell subsets and their mechanisms in the pathogenesis of allergic asthma remain unclear. In this study, we examined the proportion of different Treg cell subsets in both healthy subjects and patients with allergic asthma using flow cytometry and single-cell RNA sequencing. The migration function of the cells was compared using cell sorting and Transwell experiments. Furthermore, two allergen-challenged mouse models and a cell transfer experiment were used to examine the role of these Treg subsets. We found that the proportion of CD25⁺Foxp3⁺CD127^- Treg cells in the peripheral blood of patients with allergic asthma was lower than in those of healthy subjects. Furthermore, the circulating Treg cells expressed lower levels of CCR6 and IL-17 compared with healthy subjects. The chemokine from the airway mucosa, CCL20, was abundantly expressed, and Transwell experiments further proved that this chemokine promoted CCR6⁺ Treg cell migration in vitro. A mouse model induced by house dust mite (HDM) revealed that the number of CCR6⁺ Treg cells in the lung tissue increased remarkably. The incidence of allergic asthma may be related to an increase in Treg cells secreting IL-17 in the lung tissue. Recruited CCR6⁺ Treg cells are likely to differentiate into Th17-like cells under the Th17 environment present in the lungs. IL-17 derived from Th17-like cells could be associated with the pathology of allergic asthma by promoting Th17 responses, thereby favoring HDM-induced asthma exacerbations.

Pharmacological Rationale for Targeting IL-17 in Asthma

Asthma is a respiratory disease that currently affects around 300 million people worldwide and is defined by coughing, shortness of breath, wheezing, mucus overproduction, chest tightness, and expiratory airflow limitation. Increased levels of interleukin 17 (IL-17) have been observed in sputum, nasal and bronchial biopsies, and serum of patients with asthma compared to healthy controls. Patients with higher levels of IL-17 have a more severe asthma phenotype. Biologics are available for T helper 2 (Th2)-high asthmatics, but the Th17-high subpopulation has a relatively low response to these treatments, rendering it a rather severe asthma phenotype to treat. Several experimental models suggest that targeting the IL-17 pathway may be beneficial in asthma. Moreover, as increased activation of the Th17/IL-17 axis is correlated with reduced inhaled corticosteroids (ICS) sensitivity, targeting the IL-17 pathway might reverse ICS unresponsiveness. In this review, we present and discuss the current knowledge on the role of IL-17 in asthma and its interaction with the Th2 pathway, focusing on the rationale for therapeutic targeting of the IL-17 pathway.

Increased day-to-day fluctuations in exhaled breath profiles after a rhinovirus challenge in asthma

Background

Early detection/prediction of flare‐ups in asthma, commonly triggered by viruses, would enable timely treatment. Previous studies on exhaled breath analysis by electronic nose (eNose) technology could discriminate between stable and unstable episodes of asthma, using single/few time‐points. To investigate its monitoring properties during these episodes, we examined day‐to‐day fluctuations in exhaled breath profiles, before and after a rhinovirus‐16 (RV16) challenge, in healthy and asthmatic adults.

Methods

In this proof‐of‐concept study, 12 atopic asthmatic and 12 non‐atopic healthy adults were prospectively followed thrice weekly, 60 days before, and 30 days after a RV16 challenge. Exhaled breath profiles were detected using an eNose, consisting of 7 different sensors. Per sensor, individual means were calculated using pre‐challenge visits. Absolute deviations (|%|) from this baseline were derived for all visits. Within‐group comparisons were tested with Mann‐Whitney U tests and receiver operating characteristic (ROC) analysis. Finally, Spearman's correlations between the total change in eNose deviations and fractional exhaled nitric oxide (FeNO), cold‐like symptoms, and pro‐inflammatory cytokines were examined.

Results

Both groups had significantly increased eNose fluctuations post‐challenge, which in asthma started 1 day post‐challenge, before the onset of symptoms. Discrimination between pre‐ and post‐challenge reached an area under the ROC curve of 0.82 (95% CI = 0.65–0.99) in healthy and 0.97 (95% CI = 0.91–1.00) in asthmatic adults. The total change in eNose deviations moderately correlated with IL‐8 and TNFα (ρ ≈ .50–0.60) in asthmatics.

Conclusion

Electronic nose fluctuations rapidly increase after a RV16 challenge, with distinct differences between healthy and asthmatic adults, suggesting that this technology could be useful in monitoring virus‐driven unstable episodes in asthma.

Biomarkers of asthma

Biomarkers may be diagnostic of asthma, they may predict or reflect response to therapy or they may identify patients at risk of asthma exacerbation. A biomarker is most often measured in biologic fluids that are sampled using relatively non-invasive sampling techniques such as blood, sputum, urine or exhaled breath. Biomarkers should be stable, readily quantifiable and their measurement should be reproducible and not confounded by other host factors, or the presence of comorbidities. However, asthma comprises multiple molecular endotypes and single, sensitive, specific, biomarkers reflecting these endotypes may not exist. Combining biomarkers may improve their predictive capability in asthma. The most well-established endotypes are those described as Type2 and non-Type2 asthma. Clinical trials established the fraction of exhaled nitric oxide (FeNO) and blood eosinophil counts as key biomarkers of response to corticosteroid or targeted anti-inflammatory therapy in Type2 asthma. However, these biomarkers may have limited value in the management of asthma in real-life settings or routine clinical practise. Biomarkers for Type2 asthma are not well described or validated and more research is needed. Breathomics has provided evidence to propose a number of exhaled volatile organic compounds (VOCs) as surrogate biomarkers for airway inflammatory phenotypes, disease activity and adherence to therapy. Analysis of urinary eicosanoids has identified eicosanoids related to Type2 and non-Type2 inflammation. Future clinical trials will be important in determining how exhaled VOCs or urinary eicosanoid profiles can be used to direct precision treatments. Their future clinical use will also depend on developing simplified instrumentation for biomarker analysis at the point-of-care.

Infection-Associated Mechanisms of Neuro-Inflammation and Neuro-Immune Crosstalk in Chronic Respiratory Diseases

Chronic obstructive airway diseases are characterized by airflow obstruction and airflow limitation as well as chronic airway inflammation. Especially bronchial asthma and chronic obstructive pulmonary disease (COPD) cause considerable morbidity and mortality worldwide, can be difficult to treat, and ultimately lack cures. While there are substantial knowledge gaps with respect to disease pathophysiology, our awareness of the role of neurological and neuro-immunological processes in the development of symptoms, the progression, and the outcome of these chronic obstructive respiratory diseases, is growing. Likewise, the role of pathogenic and colonizing microorganisms of the respiratory tract in the development and manifestation of asthma and COPD is increasingly appreciated. However, their role remains poorly understood with respect to the underlying mechanisms. Common bacteria and viruses causing respiratory infections and exacerbations of chronic obstructive respiratory diseases have also been implicated to affect the local neuro-immune crosstalk. In this review, we provide an overview of previously described neuro-immune interactions in asthma, COPD, and respiratory infections that support the hypothesis of a neuro-immunological component in the interplay between chronic obstructive respiratory diseases, respiratory infections, and respiratory microbial colonization.

IL-13 and FOXO3 genes polymorphisms regulate IgE levels in asthmatic patients

Immunoglobulin E (IgE) serves a crucial role in the pathogenesis of several allergic disorders, and elevated levels of total serum IgE have been associated with asthma. IgE is responsible for the release of several asthma-associated inflammatory mediators from mast cells, such as histamine and prostaglandins. The aim of the present study was to assess the association of interleukin (IL)-13 single nucleotide polymorphism (SNP) rs20541 and forkhead box O3a (FOXO3a) SNP rs13217795 with IgE levels in asthmatic patients and a healthy control group. Genetic polymorphism analysis of SNPs was performed using PCR/restriction fragment length polymorphism. Total serum IgE levels were measured using an ELISA kit. Genotypes were grouped into three models: Co-dominant, dominant and recessive. Major and minor alleles for IL-13 SNP rs20541 and FOXO3a SNP rs13217795 were C and T, whereas for IL-13, they were G and A, respectively. There was a significant association between the IL-13 rs20541 SNP and the total IgE serum levels, in which pure minor alleles were associated with a significant reduction (~5x lower) in IgE serum levels compared with the major alleles in asthmatic subjects and to a lesser extent in the control subjects. Additionally, the FOXO3a rs13217795 SNP was associated with a significant increase in total IgE levels (~5x higher) in the asthmatic patients compared with the control subjects. In conclusion, the present study confirmed that there was a significant association between the IL-13 SNP rs20541 and asthma, and an association between the FOXO3a SNP rs13217795 with asthma pathogenicity in Jordanian subjects.

Biologics in asthma management - Are we out of breath yet?

The biologics authorized for the add-on therapy of severe asthma are monoclonal antibodies (mAbs). Before they are considered for therapy intensification, the patient’s asthma endotype is determined on the basis of phenotypic characteristics. So far, 5 biologics are available that target the signaling pathways of the “T_H2-high” asthma endotype, in which cytokines of the inflammation cascade mediated by type 2 T-helper cells are upregulated. The corresponding phenotype of this inflammatory endotype is severe eosinophilic asthma, with elevated eosinophils, immunoglobulin E, and fractional exhaled nitric oxide (FeNO). In contrast, the heterogeneous “T_H2-low” endotype is not yet sufficiently understood. Frequently described in this variant is an increase of sputum neutrophils and an increased expression of the T_H17-mediated interleukin-17 signaling pathway. There are numerous biologics currently in clinical trials, the thymic stromal lymphopoietin (TSLP) mAbs in particular have shown promising results independent of the asthma phenotype.

Regulation of Immune Responses by Nonhematopoietic Cells in Asthma

Nonhematopoietic cells are emerging as important contributors to many inflammatory diseases, including allergic asthma. Recent advances have led to a deeper understanding of how these cells interact with traditional immune cells, thereby modulating their activities in both homeostasis and disease. In addition to their well-established roles in gas exchange and barrier function, lung epithelial cells express an armament of innate sensors that can be triggered by various inhaled environmental agents, leading to the production of proinflammatory molecules. Advances in cell lineage tracing and single-cell RNA sequencing have expanded our knowledge of rare, but immunologically important nonhematopoietic cell populations. In parallel with these advances, novel reverse genetic approaches are revealing how individual genes in different lung-resident nonhematopoietic cell populations contribute to the initiation and maintenance of asthma. This knowledge is already revealing new pathways that can be selectively targeted to treat distinct forms of asthma.

Serum immunoglobulin E responses to aeroallergens in cats with naturally occurring airway eosinophilia compared to unaffected control cats

BACKGROUND

Eosinophilic airway disease in cats is sometimes described as allergic in origin, but controversy exists in the documentation of allergy in cats and the utility of allergy testing for respiratory tract diseases.

OBJECTIVE

To examine serum immunoglobulin E (IgE) response to aeroallergens in cats with airway eosinophilia.

ANIMALS

Fifteen cats with idiopathic eosinophilic airway inflammation and 9 control cats.

METHODS

Prospective, case-control study. Surplus serum from cats with airway eosinophilia documented by bronchoscopic bronchoalveolar lavage was submitted for IgE measurement using ELISA polyclonal antibody methodology. Responses for regional allergens (fungal organisms, weeds, grasses, trees, mites, insects) were assessed. Results were reported as ELISA absorbance units with scores 0 to 79 considered negative, scores between 80 and 300 considered intermediate, and scores >300 considered positive.

RESULTS

Cats with airway eosinophilia had significantly more positive serum IgE responses (25/720) than did healthy controls (5/432, P = .02); however, the number of cats with positive IgE responses (5/15) did not differ from controls (1/9, P = .35). The allergen that most commonly resulted in positive serum IgE response in cats with airway eosinophilia was dust mite (n = 4) followed by 2 types of storage mites (n = 3 each). No control cat tested positive for these allergens.

CONCLUSIONS AND CLINICAL IMPORTANCE

Serum IgE production against aeroallergens was found in some cats with eosinophilic airway inflammation, but the number of affected cats with positive results did not differ from controls. Further investigation in cats with eosinophilic, mixed, and neutrophilic airway disease in comparison to control cats is warranted.

Targeting neutrophils in asthma: A therapeutic opportunity?

Suppression of airway inflammation with inhaled corticosteroids has been the key therapeutic approach for asthma for many years. Identification of inflammatory phenotypes in asthma has moreover led to important breakthroughs, e.g. with specific targeting of the IL-5 pathway as add-on treatment in difficult-to-treat eosinophilic asthma. However, the impact of interfering with the neutrophilic component in asthma is less documented and understood. This review provides an overview of established and recent insights with regard to the role of neutrophils in asthma, focusing on research in humans. We will describe the main drivers of neutrophilic responses in asthma, the heterogeneity in neutrophils and how they could contribute to asthma pathogenesis. Moreover we will describe findings from clinical trials, in which neutrophilic inflammation was targeted. It is clear that neutrophils are important actors in asthma development and play a role in exacerbations. However, more research is required to fully understand how modulation of neutrophil activity could lead to a significant benefit in asthma patients with airway neutrophilia.

Multidimensional Assessment of Asthma Identifies Clinically Relevant Phenotype Overlap: A Cross-Sectional Study

BACKGROUND

Asthma is a heterogeneous disease with multiple phenotypes; however, the relevance of phenotype overlap remains largely unexplored.

OBJECTIVE

To examine the relationship between phenotype overlap and clinical and inflammatory profiles of asthma.

METHODS

In this cross-sectional study, adult participants with stable asthma (n = 522) underwent multidimensional assessments. The 10 most common phenotypes of asthma were defined and then classified into those commonly associated with Type (T) 2 or non-T2 inflammation. Furthermore, phenotype overlap scores (POS), representing the cumulative concomitant phenotypes, were used to analyze its association with clinical and inflammatory asthmatic profiles.

RESULTS

Among the 522 participants, 73.4% (n = 383) had phenotype overlap, and mixed T2 and non-T2 inflammation coexisted in 47.5% (n = 248). T2 POS was positively associated with eosinophils, IgE, and fractional exhaled nitric oxide (FeNO), and negatively with Asthma Quality of Life Questionnaire (AQLQ), sputum neutrophils, IL-17A, IL-8, and TNF-α. Non-T2 POS was positively associated with Asthma Control Questionnaire, neutrophils and sputum IL-8, and negatively with AQLQ, forced expiratory volume in 1 s, blood eosinophils, IgE, and FeNO (all P < .05). Patients with phenotypes that are associated with mixed T2 and non-T2 inflammation had elevated T2 inflammation biomarkers but worse asthma control. Both T2 (adjusted β = -0.191, P = .035) and non-T2 (adjusted β = 0.310, P < .001) POS were significantly associated with severe exacerbations.

CONCLUSIONS

Phenotype overlap is extremely common in asthmatic patients and significantly associated with clinical and inflammatory profiles. Patients with phenotypes associated with mixed T2 and non-T2 inflammation might be unresponsive to medications owing to increased non-T2 inflammation. Multidimensional asthma assessment identifies clinically relevant phenotype overlap.

Clinical Characterization of the Frequent Exacerbator Phenotype in Asthma

Background: Asthma exacerbation is episodic worsening of respiratory symptoms in conjunction with the deterioration of lung function, which may occur independently from the asthma severity hampering asthmatics’ quality of life. This study aimed to characterize the patient phenotype more prone to asthma exacerbation (oral corticosteroid burst ≥2 per year) to allow the proper identification of such patients. Methods: This real-life, observational, cross-sectional study evaluated 464 asthmatic patients stratified according to the asthma exacerbations experienced in the previous year. Clinical, functional, and blood parameters were retrieved from chart data and were representative of patients in stable conditions. Results: The frequent asthma exacerbator was more commonly female, suffered from chronic rhinosinusitis with nasal polyposis, had reduced lung function and peripheral oxygen saturation, and had increased daily activity limitations. These patients often had severe asthma and more frequently needed hospitalization in their lives. Furthermore, the frequent asthma exacerbator had higher concentrations of serum immunoglobulin E (IgE) and exhaled nitric oxide with cut-off risk values of 107.5 kU/L (OR = 4.1) and 43.35 ppb (OR = 3.8), respectively. Conclusions: This study illustrates the clinical features of the frequent asthma exacerbator phenotype. Nevertheless, serum IgE and exhaled nitric oxide could allow the identification of this phenotype and the establishment of an appropriate therapeutic approach.

A Network of Sputum MicroRNAs Is Associated with Neutrophilic Airway Inflammation in Asthma

Rationale: MicroRNAs are potent regulators of biologic systems that are critical to tissue homeostasis. Individual microRNAs have been identified in airway samples. However, a systems analysis of the microRNA-mRNA networks present in the sputum that contribute to airway inflammation in asthma has not been published.Objectives: Identify microRNA and mRNA networks in the sputum of patients with asthma.Methods: We conducted a genome-wide analysis of microRNA and mRNA in the sputum from patients with asthma and correlated expression with clinical phenotypes. Weighted gene correlation network analysis was implemented to identify microRNA networks (modules) that significantly correlate with clinical features of asthma and mRNA expression networks. MicroRNA expression in peripheral blood neutrophils and lymphocytes and in situ hybridization of the sputum were used to identify the cellular sources of microRNAs. MicroRNA expression obtained before and after ozone exposure was also used to identify changes associated with neutrophil counts in the airway.Measurements and Main Results: Six microRNA modules were associated with clinical features of asthma. A single module (nely) was associated with a history of hospitalizations, lung function impairment, and numbers of neutrophils and lymphocytes in the sputum. Of the 12 microRNAs in the nely module, hsa-miR-223-3p was the highest expressed microRNA in neutrophils and was associated with increased neutrophil counts in the sputum in response to ozone exposure. Multiple microRNAs in the nely module correlated with two mRNA modules enriched for TLR (Toll-like receptor) and T-helper cell type 17 (Th17) signaling and endoplasmic reticulum stress. hsa-miR-223-3p was a key regulator of the TLR and Th17 pathways in the sputum of subjects with asthma.Conclusions: This study of sputum microRNA and mRNA expression from patients with asthma demonstrates the existence of microRNA networks and genes that are associated with features of asthma severity. Among these, hsa-miR-223-3p, a neutrophil-derived microRNA, regulates TLR/Th17 signaling and endoplasmic reticulum stress.

Majie cataplasm provides a shield against asthmatic punch from the neuroimmune system

Asthma poses a threat to human health, and its pathogenesis is closely related to the neuroimmune system. Majie cataplasm can not only regulate the immune system but also the nervous system in asthma patients for its components. We speculate that Majie cataplasm may relieve asthmatic patients with sensitivity to hormone or not by regulating the body's neuroimmune system.

Methods

In this experiment, a mouse model of asthma was well established by ovalbumin. The lung function of animals was examined and pathological changes in the lung tissue were assessed by hematoxylin-eosin staining. Serum immunoglobulin E (IgE), calcitonin gene-related peptide (CGRP) and neurokinin A (NKA) were measured by ELISA. The location of CGRP, CD3 and neutrophil in lung tissue and their expressions were detected by immunofluorescence staining. In addition, contents of CGRP mRNA, Substance P (SP) mRNA, interleukin (IL)-17 mRNA and interleukin(IL)-13 mRNA were detected by quantitative polymerase chain reaction.

Results

Compared with the asthma model group, Majie cataplasm and dexamethasone can not only equivalently relieve airway hyperresponsiveness, but also make the content of serum IgE reduced. In addition, they can lower the content of serum CGRP and NKA after OVA stimulation, and this effect was more obvious for Majie cataplasm. Our results also showed that Majie Cataplasm and dexamethasone could inhibit the secretion of CGRP and the infiltration of T lymphocytes together with neutrophils in lung tissue and reduce expressions of CGRP mRNA, SP mRNA, IL-17 mRNA and IL-13 mRNA in lung tissue.

Conclusion

Majie cataplasm effectively relieves expressions of neuropeptides such as CGRP, reduces the infiltration of immune cells in lung tissue, regulates the body's neuroimmune system, and has a therapeutic potential for both Th2 asthma and neutrophilic asthma.

Resolution of allergic asthma

Allergic asthma is an inflammatory disease of the airways characterized by recurrent episodes of wheezing and bronchoconstriction. Chronic inflammation may finally lead to structural damage followed by airway remodeling. Various studies in recent years contributed to unravel important aspects of the immunopathogenesis of asthma and adapted new pharmaceutical developments. Here, I consider some novel insights into the immunopathogenesis of asthma and the protective and pathogenic roles of some innate and adaptive immune cells as well as the function of soluble mediators such as cytokines. Particular attention will be given to new concepts on resolution of chronic airway inflammation for prevention of airway structural damage.