Investigation of the relationship between IL-6 and type 2 biomarkers in patients with severe asthma

Investigation of lactotransferrin messenger RNA expression levels as an anti-type 2 asthma biomarker

BACKGROUND

Lactotransferrin (LTF) has an immunomodulatory function, and its expression levels are associated with asthma susceptibility.

OBJECTIVES

We sought to investigate LTF messenger RNA (mRNA) expression levels in human bronchial epithelial cells (BECs) as an anti-type 2 (T2) asthma biomarker.

METHODS

Association analyses between LTF mRNA expression levels in BECs and asthma-related phenotypes were performed in the Severe Asthma Research Program (SARP) cross-sectional (n = 155) and longitudinal (n = 156) cohorts using a generalized linear model. Correlation analyses of mRNA expression levels between LTF and all other genes were performed by Spearman correlation.

RESULTS

Low LTF mRNA expression levels were associated with asthma susceptibility and severity (P < .025), retrospective and prospective asthma exacerbations, and low lung function (P < 8.3 × 10-3). Low LTF mRNA expression levels were associated with high airway T2 inflammation biomarkers (sputum eosinophils and fractional exhaled nitric oxide; P < 8.3 × 10-3) but were not associated with blood eosinophils or total serum IgE. LTF mRNA expression levels were negatively correlated with expression levels of TH2 or asthma-associated genes (POSTN, NOS2, and MUC5AC) and eosinophil-related genes (IL1RL1, CCL26, and IKZF2) and positively correlated with expression levels of TH1 and inflammation genes (IL12A, MUC5B, and CC16) and TH17-driven cytokines or chemokines for neutrophils (CXCL1, CXCL6, and CSF3) (P < 3.5 × 10-6).

CONCLUSIONS

Low LTF mRNA expression levels in BECs are associated with asthma susceptibility, severity, and exacerbations through upregulation of airway T2 inflammation. LTF is a potential anti-T2 biomarker, and its expression levels may help determine the balance of eosinophilic and neutrophilic asthma.

Multivariate Cluster Analyses to Characterize Asthma Heterogeneity and Benralizumab Responsiveness

BACKGROUND

An improved understanding of how severe asthma heterogeneity affects response could inform treatment decisions.

OBJECTIVES

Characterize heterogeneity and benralizumab responsiveness in patients grouped by predefined Severe Asthma Research Program clusters using a multivariate approach.

METHODS

In post-hoc analyses of the randomized, double-blind, placebo-controlled phase III SIROCCO (NCT01928771) and CALIMA (NCT01914757) studies, patients with severe asthma who received benralizumab or placebo were assigned to clusters using an established discriminant function to analyze 11 clinical characteristics simultaneously. The annualized asthma exacerbation rate, exacerbation incidence, and lung function were analyzed across clusters.

RESULTS

Patients (n = 2,281) met criteria for four of five clusters: cluster 2 (early-onset moderate asthma, n = 393), cluster 4 (early-onset severe asthma, n = 386), cluster 3 (late-onset severe asthma, n = 641), and cluster 5 (late-onset severe, obstructed asthma, n = 861); no patients met cluster 1 criteria. Exacerbation rate reductions were significant in late-onset severe asthma (-48% [95% CI, -61% to -31%]; P < .0001) and late-onset severe, obstructed asthma (-50% [95% CI, -59% to -38%]; P < .0001), with nonsignificant reductions in early-onset clusters. These differences could not be fully explained by blood eosinophil count differences. Values for improvements in FEV1 were significant in late-onset severe asthma (+133 mL [95% CI, 66-200]; P = .0001) and late-onset severe, obstructed asthma (+160 mL [95% CI, 85-235]; P < .0001) while maintaining acute bronchodilator responsiveness.

CONCLUSIONS

Benralizumab reduced exacerbations and improved lung function, primarily in late-onset asthma clusters. This multivariate approach to identify subphenotypes, potentially reflecting pathobiological mechanisms, can guide therapy beyond univariate approaches.

Circulating Biomarkers, Fraction of Exhaled Nitric Oxide, and Lung Function in Patients With Human Immunodeficiency Virus and Tuberculosis

BACKGROUND

Identification of proinflammatory factors responding to Mycobacterium tuberculosis is important to reduce long-term sequelae of pulmonary tuberculosis (TB).

METHODS

We examined the association between plasma biomarkers, the fraction of exhaled nitric oxide (FeNO), and lung function among a prospective cohort of 105 adults newly diagnosed with TB/human immunodeficiency virus (HIV) in South Africa. Participants were followed for 48 weeks from antiretroviral therapy (ART) initiation with serial assessments of plasma biomarkers, FeNO, lung function, and respiratory symptoms. Linear regression and generalized estimating equations were used to examine the associations at baseline and over the course of TB treatment, respectively.

RESULTS

At baseline, higher FeNO levels were associated with preserved lung function, whereas greater respiratory symptoms and higher interleukin (IL)-6 plasma levels were associated with worse lung function. After ART and TB treatment initiation, improvements in lung function were associated with increases in FeNO (rate ratio [RR] = 86 mL, 95% confidence interval [CI] = 34-139) and decreases in IL-6 (RR = -118 mL, 95% CI = -193 to -43) and vascular endothelial growth factor ([VEGF] RR = -178 mL, 95% CI = -314 to -43).

CONCLUSIONS

Circulating IL-6, VEGF, and FeNO are associated with lung function in adults being treated for TB/HIV. These biomarkers may help identify individuals at higher risk for post-TB lung disease and elucidate targetable pathways to modify the risk of chronic lung impairment among TB survivors.

Genetic relationships between high blood eosinophil count, asthma susceptibility, and asthma severity

OBJECTIVE

Genetic relationships between blood eosinophil count (BEC), asthma susceptibility, and severity are unclear. We sought to identify the genetic difference between type 2 (T2) and nontype 2 (non-T2) asthma (defined by BEC) and investigate genetic relationships between high BEC, asthma susceptibility, and severity.

METHODS

Genome-wide association studies (GWASs) were performed for T2 (n = 9,064; BEC ≥ 300 cells/μL) versus non-T2 asthma (n = 14,379; BEC < 150 cells/μL) and asthma susceptibility (37,227 asthmatics vs. 124,132 nonasthma controls) in the UK Biobank and asthma severity (moderate-to-severe asthma [n = 2,153] vs. mild asthma [n = 5165]) in the All of Us Research Program (AoURP). Genetic causality between BEC, asthma susceptibility, and severity were dissected using Mendelian randomization (MR).

RESULTS

High BEC was associated with asthma and decreased pulmonary function. GWASs revealed four sets of genetic variants (p < 5 × 10-8): genes associated with only BEC or asthma and genes associated with high BEC and asthma in the same or opposite direction. The C allele of rs653178 in ATXN2 was associated with high BEC, risk for autoimmune diseases, and protection for asthma. Genetic variants associated with BEC or asthma were not associated with asthma severity. MR indicated high BEC and asthma were in bidirectional causal relationship (p < .001); however, they were not causal for asthma severity.

CONCLUSIONS

Genetic variants associated with asthma or BEC and asthma severity are distinctive. High BEC is a risk factor for asthma; however, it is neither necessary nor sufficient for asthma susceptibility and severity.

Dupilumab Efficacy in Patients with Type 2 Asthma with and without Elevated Blood Neutrophils

Introduction

Elevated neutrophil counts in blood, sputum, or lung have been associated with poor clinical outcomes and more severe disease in patients with type 2 asthma. In the phase 3 LIBERTY ASTHMA QUEST (NCT02414854), add-on dupilumab 200 and 300 mg every 2 weeks compared with matched placebo significantly reduced severe asthma exacerbations and improved forced expiratory volume in 1 s (FEV1) in patients with uncontrolled, moderate-to-severe asthma. This post hoc analysis explored the efficacy of dupilumab in patients with type 2 asthma enrolled in QUEST with or without elevated blood neutrophil counts.

Methods

Annualized severe exacerbation rates during the 52-week treatment period and least-squares mean change from baseline in FEV1 over time were evaluated for patients with elevated type 2 biomarkers at baseline (blood eosinophils ≥ 150 cells/µL or fractional exhaled nitric oxide (FeNO) ≥ 20 ppb; and eosinophils ≥ 300 cells/µL or FeNO ≥ 50 ppb) and low (<4,000 cells/µL) or high (≥4,000 cells/µL) neutrophil counts.

Results

Dupilumab significantly reduced annualized severe exacerbation rates compared with placebo during the 52-week treatment period in patients with elevated type 2 biomarkers, irrespective of baseline neutrophil count (P < 0.0001 for all comparisons). Significant improvements in FEV1 versus placebo were observed as early as Week 2 and over the 52-week treatment period, irrespective of baseline neutrophil count (P < 0.001 for all comparisons). Safety findings were similar across all subgroups, regardless of neutrophil counts at baseline.

Conclusions

Dupilumab treatment significantly reduced annualized severe exacerbation rates and improved lung function in patients with uncontrolled, moderate-to-severe, type 2 asthma, irrespective of baseline blood neutrophil count. This trial is registered with NCT02414854.

Investigations of a combination of atopic status and age of asthma onset identify asthma subphenotypes

OBJECTIVE

Subphenotypes of asthma may be determined by age onset and atopic status. We sought to characterize early or late onset atopic asthma with fungal or non-fungal sensitization (AAFS or AANFS) and non-atopic asthma (NAA) in children and adults in the Severe Asthma Research Program (SARP). SARP is an ongoing project involving well-phenotyped patients with mild to severe asthma.

METHODS

Phenotypic comparisons were performed using Kruskal-Wallis or chi-square test. Genetic association analyses were performed using logistic or linear regression.

RESULTS

Airway hyper-responsiveness, total serum IgE levels, and T2 biomarkers showed an increasing trend from NAA to AANFS and then to AAFS. Children and adults with early onset asthma had greater % of AAFS than adults with late onset asthma (46% and 40% vs. 32%; P < 0.00001). In children, AAFS and AANFS had lower % predicted FEV1 (86% and 91% vs. 97%) and greater % of patients with severe asthma than NAA (61% and 59% vs. 43%). In adults with early or late onset asthma, NAA had greater % of patients with severe asthma than AANFS and AAFS (61% vs. 40% and 37% or 56% vs. 44% and 49%). The G allele of rs2872507 in GSDMB had higher frequency in AAFS than AANFS and NAA (0.63 vs. 0.55 and 0.55), and associated with earlier age onset and asthma severity.

CONCLUSIONS

Early or late onset AAFS, AANFS, and NAA have shared and distinct phenotypic characteristics in children and adults. AAFS is a complex disorder involving genetic susceptibility and environmental factors.

Genetic analyses of chr11p15.5 region identify MUC5AC-MUC5B associated with asthma-related phenotypes

OBJECTIVE

Genome-wide association studies (GWASs) have identified single nucleotide polymorphisms (SNPs) in chr11p15.5 region associated with asthma and idiopathic interstitial pneumonias (IIPs). We sought to identify functional genes for asthma by combining SNPs and mRNA expression in bronchial epithelial cells (BEC) in the Severe Asthma Research Program (SARP).

METHODS

Correlation analyses of mRNA expression of six candidate genes (AP2A2, MUC6, MUC2, MUC5AC, MUC5B, and TOLLIP) and asthma phenotypes were performed in the longitudinal cohort (n = 156) with RNAseq in BEC, and replicated in the cross-sectional cohort (n = 155). eQTL (n = 114) and genetic association analysis of asthma severity (426 severe vs. 531 non-severe asthma) were performed, and compared with previously published GWASs of IIPs and asthma.

RESULTS

Higher expression of AP2A2 and MUC5AC and lower expression of MUC5B in BEC were correlated with asthma, asthma exacerbations, and T2 biomarkers (P < 0.01). SNPs associated with asthma and IIPs in previous GWASs were eQTL SNPs for MUC5AC, MUC5B, or TOLLIP, however, they were not in strong linkage disequilibrium. The risk alleles for asthma or protective alleles for IIPs were associated with higher expression of MUC5AC and lower expression of MUC5B. rs11603634, rs12788104, and rs28415845 associated with moderate-to-severe asthma or adult onset asthma in previous GWASs were not associated with asthma severity (P > 0.8).

CONCLUSIONS

SNPs associated with asthma in chr11p15.5 region are not associated with asthma severity neither with IIPs. Higher expression of MUC5AC and lower expression of MUC5B are risk for asthma but protective for IIPs.

Genomics of Treatable Traits in Asthma

The astounding number of genetic variants revealed in the 15 years of genome-wide association studies of asthma has not kept pace with the goals of translational genomics. Moving asthma diagnosis from a nonspecific umbrella term to specific phenotypes/endotypes and related traits may provide insights into features that may be prevented or alleviated by therapeutical intervention. This review provides an overview of the different asthma endotypes and phenotypes and the genomic findings from asthma studies using patient stratification strategies and asthma-related traits. Asthma genomic research for treatable traits has uncovered novel and previously reported asthma loci, primarily through studies in Europeans. Novel genomic findings for asthma phenotypes and related traits may arise from multi-trait and specific phenotyping strategies in diverse populations.

Controversies in Allergy: Are Biologic Treatment Responses in Severe Asthma the Same in Adults and Children?

The availability of biologic agents for patients with severe asthma has increased dramatically over the last several decades. The absence of direct head-to-head comparative data and relative lack of biomarkers to predict response can make it difficult to choose the right biologic medication for a given patient. Selecting a biologic agent for the pediatric population presents further challenges due to more limited approved biologic agents and fewer clinical trials in children. In addition, the outcome data that are currently available suggest that treatment responses for a given biologic may be different between adult and pediatric patients. To better understand this possible difference in treatment response, this review focuses on the available efficacy data for biologics evaluated in adult and pediatric patients with severe asthma in addition to other considerations when choosing a biologic agent. Finally, this review discusses how asthma phenotypes differ across age groups and their contributions to the responses to biologic treatment across age groups.

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.

Low CC16 mRNA Expression Levels in Bronchial Epithelial Cells Are Associated with Asthma Severity

Rationale: CC16 is a protein mainly produced by nonciliated bronchial epithelial cells (BECs) that participates in host defense. Reduced CC16 protein concentrations in BAL and serum are associated with asthma susceptibility. Objectives: Few studies have investigated the relationship between CC16 and asthma progression, and none has focused on BECs. In this study, we sought to determine if CC16 mRNA expression levels in BECs are associated with asthma severity. Methods: Association analyses between CC16 mRNA expression levels in BECs (242 asthmatics and 69 control subjects) and asthma-related phenotypes in Severe Asthma Research Program were performed using a generalized linear model. Measurements and Main Results: Low CC16 mRNA expression levels in BECs were significantly associated with asthma susceptibility and asthma severity, high systemic corticosteroids use, high retrospective and prospective asthma exacerbations, and low pulmonary function. Low CC16 mRNA expression levels were significantly associated with high T2 inflammation biomarkers (fractional exhaled nitric oxide and sputum eosinophils). CC16 mRNA expression levels were negatively correlated with expression levels of Th2 genes (IL1RL1, POSTN, SERPINB2, CLCA1, NOS2, and MUC5AC) and positively correlated with expression levels of Th1 and inflammation genes (IL12A and MUC5B). A combination of two nontraditional T2 biomarkers (CC16 and IL-6) revealed four asthma endotypes with different characteristics of T2 inflammation, obesity, and asthma severity. Conclusions: Our findings indicate that low CC16 mRNA expression levels in BECs are associated with asthma susceptibility, severity, and exacerbations, partially through immunomodulation of T2 inflammation. CC16 is a potential nontraditional T2 biomarker for asthma development and progression.

Serum exosome inflamma-miRs are surrogate biomarkers for asthma phenotype and severity

BACKGROUND

Asthma is a heterogeneous disease with several phenotypes, endotypes and severity degrees, in which different T-cell subpopulations are involved. These cells express specific miRNAs (i.e. inflamma-miRs) that can be released to serum in exosomes after activation and be used as biomarkers of underlying inflammation. Thus, we aim to evaluate specific T-cell miRNA signatures in serum exosomes from different subgroups of asthmatic patients.

METHODS

Samples from healthy donors (N = 30) and patients (N = 119) with different asthma endotypes (T2^high -Atopic/T2^high -Non-atopic/T2^low ) and severity degrees (mild/MA and moderate-severe/MSA) were used. Demographic, clinical, haematological and biochemical characteristics were collected. Twelve miRNAs previously associated with different Th subsets were preselected and their levels in serum exosome samples were measured using RTqPCR.

RESULTS

We detected five miRNAs with high confidence in serum exosomes: miR-16-5p, miR-21-5p, miR-126-3p, miR146a-5p and miR-215-5p. All of them, except miR-16-5p were upregulated in MSA patients compared to MA. A logistic regression model including each of these miRNAs was created to discriminate both conditions, rendering a ROC curve AUC of 0.896 (0.830-0.961). miR-21-5p and miR-126-3p, both involved in Th1/Th2 differentiation, were specifically augmented in T2^high -Atopic patients. Of note, all these changes were found in samples collected in autumn. On the contrary, IL-6^high patients with MSA, which were more obese, older, with higher neutrophil and basophil counts and TNF levels, displayed a decrease of miR-21-5p, miR-126-3p and miR-146a-5p.

CONCLUSION

Immune-related miRNAs, including miR-21-5p, miR-126-3p, miR-146a-5p and miR-215-5p, can be used as clinically relevant non-invasive biomarkers of the phenotype/endotype and severity of asthma.

Systemic corticosteroids in asthma: A call to action from World Allergy Organization and Respiratory Effectiveness Group

Systemic corticosteroids (SCS) are a highly effective treatment for acute exacerbations and long-term symptom control in asthma. Long-term SCS use is highly prevalent across all asthma severities, occurring in over 20% of patients with severe or uncontrolled disease globally. It is now well known that exposure to both long-term and repeated acute courses of SCS is associated with a high risk of serious adverse effects (AEs), such as osteoporosis, and metabolic and cardiovascular complications, especially when prescribed onto a background of other corticosteroids. The aim of this call-to-action article, endorsed by the World Allergy Organization and the Respiratory Effectiveness Group, is to review the accumulating evidence on the burden of SCS on patients with asthma and provide an overview of potential strategies for implementing SCS Stewardship. Primary prevention of exacerbations and improvement of asthma control is a key first step in achieving SCS Stewardship, by optimizing maintenance asthma medications and addressing modifiable risk factors, such as adherence and inhaler technique. Other key elements of SCS Stewardship include increasing appropriate specialist referrals for multidisciplinary review, assessment of biomarkers, and consideration of oral corticosteroid-sparing add-on therapies (eg, biologics). In cases where SCS use is deemed clinically justified, it should be tapered to the lowest possible dose. In addition, patients receiving long-term SCS or frequent acute courses should be closely monitored for emergence of SCS-related AEs. Because of the extensive data available on the costly and burdensome AEs associated with SCS use, as well as the range of treatment options now available, there is a need for healthcare providers (HCPs) to carefully evaluate whether the benefits of SCS outweigh the potential harms, to adopt SCS-sparing and Stewardship strategies, and to consider alternative therapies where possible. Development of a structured and collaborative SCS Stewardship approach is urgently required to protect patients from the potential harm of SCS use.

Associations Between Allergies, Walking, Sedentary Time, and Low Back Pain

PURPOSE

To examine associations between allergies, low back pain (LBP), walking, and sedentary time in a representative sample of adults aged 50 years and older.

DESIGN

A cross-sectional, correlational study.

METHODS

We used the 2014-2015 Korean National Health and Nutrition Examination Survey. Allergies of interest included allergic rhinitis, asthma, and atopic dermatitis. Adequate walking was defined as walking five or more days per week. Sedentary time was categorized as <7 h vs. ≥7 h. Logistic regression was performed to examine the association between allergies and LBP, controlling for demographics and lifestyle. Subgroup analyses were conducted to investigate the role of walking and sedentary lifestyle in LBP among those with or without allergies.

RESULTS

Of 4,897 respondents, 23.1% reported LBP. After controlling for covariates, individuals with allergies were 1.68 times more likely to have LBP than those without allergies. In the non-allergy group, those with inadequate walking and sedentary lifestyles were nearly twice as likely to report LBP than those with adequate walking and without sedentary lifestyles. However, this trend was not observed in the patients with allergy diagnoses.

CONCLUSIONS

We confirmed associations between lifetime allergy diagnosis and LBP. A protective role of physical activity and non-sedentary lifestyle in LBP remained only among those without allergies.

CLINICAL IMPLICATIONS

Nurses should emphasize the impact of allergies on LBP. The advantages of walking and non-sedentary lifestyles for preventing or relieving chronic conditions should be routinely included in patient education; however, their preventive role in LBP should be underscored for those without allergies.

The Impact of Insulin Resistance on Loss of Lung Function and Response to Treatment in Asthma

Rationale: The role of obesity-associated insulin resistance (IR) in airflow limitation in asthma is uncertain. Objectives: Using data in the Severe Asthma Research Program 3 (SARP-3), we evaluated relationships between homeostatic measure of IR (HOMA-IR), lung function (cross-sectional and longitudinal analyses), and treatment responses to bronchodilators and corticosteroids. Methods: HOMA-IR values were categorized as without (<3.0), moderate (3.0-5.0), or severe (>5.0). Lung function included FEV1 and FVC measured before and after treatment with inhaled albuterol and intramuscular triamcinolone acetonide and yearly for 5 years. Measurements and Main Results: Among 307 participants in SARP-3, 170 (55%) were obese and 140 (46%) had IR. Compared with patients without IR, those with IR had significantly lower values for FEV1 and FVC, and these lower values were not attributable to obesity effects. Compared with patients without IR, those with IR had lower FEV1 responses to β-adrenergic agonists and systemic corticosteroids. The annualized decline in FEV1 was significantly greater in patients with moderate IR (-41 ml/year) and severe IR (-32 ml/year,) than in patients without IR (-13 ml/year, P < 0.001 for both comparisons). Conclusions: IR is common in asthma and is associated with lower lung function, accelerated loss of lung function, and suboptimal lung function responses to bronchodilator and corticosteroid treatments. Clinical trials in patients with asthma and IR are needed to determine if improving IR might also improve lung function.

Allergic and eosinophilic asthma in the era of biomarkers and biologics: similarities, differences and misconceptions

OBJECTIVE

Severe asthma is associated with substantial personal and economic burden; maintaining disease control is the key management goal. Increased understanding of asthma heterogeneity and development of type 2 (T2)-targeting biologics has substantially advanced disease management and outcomes; however, despite both being driven by T2 inflammation, allergic and eosinophilic asthma have different treatment recommendations. We sought to better understand the similarities and differences between allergic and eosinophilic asthma and highlight where misconceptions may arise.

DATA SOURCES

Published articles, pivotal trials, post hoc analyses, and asthma clinical guidelines sourced from PubMed.

STUDY SELECTIONS

Sources reporting allergic and eosinophilic asthma classifications, disease mechanisms, and biomarkers associated with treatment response.

RESULTS

This review highlights that severe allergic and eosinophilic asthma are both driven by T2 inflammation with eosinophils playing a cardinal role. Despite this overlap, treatment recommendations differ based on asthma classification. T2 cytokine gene expression is a reasonably well-established research tool, but not a well-established biomarker in clinical practice, unlike blood eosinophil counts, fractional exhaled nitric oxide, and immunoglobulin E; the clinical relevance of immunoglobulin E as a predictive biomarker remains unclear.

CONCLUSION

Asthma classifications that can be easily characterized at patient level to ensure accurate diagnosis, predict disease trajectory, and treatment response are required. The current dichotomy of allergic and eosinophilic asthma classifications is likely too simplistic, given the similar eosinophil-mediated disease pathophysiology in both classifications. Our results provide future directions to guide clinically meaningful interpretation of asthma endophenotypes, which may improve understanding of severe asthma characterization and aid future advances in defining responders more precisely with personalized medicine approaches.

2021 year in review: Spotlight on eosinophils

This review highlights recent advances in the understanding of eosinophils and eosinophilic diseases, particularly eosinophilic gastrointestinal diseases during the last year. The increasing incidence of diseases marked by eosinophilia has been documented and highlighted the need to understand eosinophil biology and eosinophilic contributions to disease. Significant insight into the nature of eosinophilic diseases has been achieved using next-generation sequencing technologies, proteomic analysis, and machine learning to analyze tissue biopsies. These technologies have elucidated mechanistic underpinnings of eosinophilic inflammation, delineated patient endotypes, and identified patient responses to therapeutic intervention. Importantly, recent clinical studies using mAbs that interfere with type 2 cytokine signaling or deplete eosinophils point to multiple and complex roles of eosinophils in tissues. Several studies identified distinct activation features of eosinophils in different tissues and disease states. The confluence of these studies supports a new paradigm of tissue-resident eosinophils that have pro- and anti-inflammatory immunomodulatory roles in allergic disease. Improved understanding of unique eosinophil activation states is now poised to identify novel therapeutic targets for eosinophilic diseases.

Clinical relevance of Alternaria alternata sensitization in patients within type 2-high and type 2-low asthma

Alternaria sensitization is correlated with persistent asthma. Type 2 (T2)-asthma endotypes are characterized by the release of eosinophils. However, the prevalence and sensitization patterns in patients with Alternaria asthma between T2-high and T2-low endotypes are unknown. We retrospectively reviewed 582 patients with Alternaria asthma and divided them into T2-high (n = 376) and T2-low (n = 206) groups with a threshold of 300 cells/µL in blood eosinophil counts. Data for basic information, skin test or IgE detection results, and blood eosinophil counts were collected. The age of patients in the T2-high group (13.66 ± 13.23) was lower than that of the T2-low group (18.02 ± 15.03). Patients with T2-high asthma had relatively higher rates of taking inhaled corticosteroids (ICS) and positive family history than the T2-low group. Pet keepers and allergen immunotherapy (AIT) patients were comparable between these groups, In the T2-high group, patients had higher levels of total serum IgE (T-IgE) and showed a significant positive correlation with eosinophil counts (r = 0.166, P = 0.001), followed by higher Alternaria-specific IgE (sIgE) levels (median, 13.7; range, 4.86-25.3). Compared to the T2-low group, the frequency of poly-sensitized patients and the rate of each allergen among the nine common allergens were all higher in the T2-high group; the statistical differences mainly focused on pollens such as birch (P = 0.005), firmiana (P = 0.004), and mugwort (P = 0.005). Young, male patients had a high prevalence of T2-high Alternaria asthma, along with higher rates of T-IgE, sIgE levels, and poly-sensitized patterns.

Treatment approaches for the patient with T2 low asthma

OBJECTIVE

To identify treatment approaches that can be used in the management of patients with asthma who lack significant type 2 inflammation, also called T2 low asthma.

DATA SOURCES

Recent expert guideline updates on the management of asthma, recent journal articles and review articles, and foundational journal articles are referenced.

STUDY SELECTIONS

This review cites clinical cohort studies of highly characterized patients with asthma, clinical interventional trials of high impact, mechanistic studies relevant to T2 low asthma, and emerging work in this area.

RESULTS

T2 low asthma accounts for approximately one-third to one-half of individuals with asthma. Characteristics of participants with T2 low asthma include higher body mass index, cigarette smoking/smoke exposure, relative lack of responsiveness to steroids, less bronchodilator reversibility, and often the presence of neutrophilic inflammation. Multiple available interventions target these characteristics, including standard inhalers, azithromycin, and lifestyle interventions of weight loss and smoking cessation.

CONCLUSION

Treatment of T2 low asthma should involve currently available approaches and will benefit from improved definition and understanding of disease pathobiology.

JAK inhibitors for asthma

Asthma is an inflammatory disease of the airways characterized by intermittent episodes of wheezing, chest tightness, and cough. Many of the inflammatory pathways implicated in asthma involve cytokines and growth factors that activate Janus kinases (JAKs). The discovery of the JAK/signal transducer and activator of transcription (STAT) signaling pathway was a major breakthrough that revolutionized our understanding of cell growth and differentiation. JAK inhibitors are under active investigation for immune and inflammatory diseases, and they have demonstrated clinical efficacy in diseases such as rheumatoid arthritis and atopic dermatitis. Substantial preclinical data support the idea that inhibiting JAKs will ameliorate airway inflammation and hyperreactivity in asthma. Here, we review the rationale for use of JAK inhibitors in different asthma endotypes as well as the preclinical and early clinical evidence supporting such use. We review preclinical data from the use of systemic and inhaled JAK inhibitors in animal models of asthma and safety data based on the use of JAK inhibitors in other diseases. We conclude that JAK inhibitors have the potential to usher in a new era of anti-inflammatory treatment for asthma.

Cytokine antibody array-based analysis of IL-37 treatment effects in asthma

Asthma is driven by group 2 innate lymphoid cells, antigen-specific CD4+ T helper type 2 cells and their cytokines such as interleukin (IL)-4, IL-5, IL-13. IL-37 is decreased in asthma and negatively related to Th2 cytokines and other pro-inflammatory cytokines. Our study showed that IL-37 level in asthmatic peripheral blood mononuclear cells was lower than in healthy. Further, IL-37 was negatively correlated with exhaled nitric oxide, asthma control test score, atopy and rhinitis history in asthmatics. Then an OVA-induced asthma mice model treated with rhIL-37 was established. An antibody array was employed to uncover altered cytokines induced by IL-37 in mice lung tissue. 20 proteins differentially expressed after rhIL-37 treatment and five of them were validated in asthmatic peripheral blood mononuclear cells. Consistent with cytokine antibody array, CCL3, CCL4, CCL5 decreased after IL-37 administration. While CXCL9 and CXCL13 were no change. We concluded that IL-37 reduce asthmatic symptoms by inhibit pro-inflammatory cytokine such as CCL3, CCL4, CCL5.

Interleukin-6 promotes ferroptosis in bronchial epithelial cells by inducing reactive oxygen species-dependent lipid peroxidation and disrupting iron homeostasis

Asthma occurs accompanied by the ferroptosis in bronchial epithelial cells, during which Interleukin-6 (IL-6) plays a key role. However, the associations between IL-6, ferroptosis and asthma have not been reported. Bronchial epithelial cells BEAS-2B cells were induced by different concentrations of IL-6 and cell viability was detected by MTT assay. The TBARS production rate was detected by corresponding kit. The expression of oxidative stress-related indexes was detected by ELISA. The Iron Assay Kits detected total iron levels and ferrous ion (Fe²⁺) levels. Labile iron pool assay was used to detect the cell unstable iron pool. The expression of ferroptosis-related proteins was detected by Western blot. To further examine the mechanism of action, ferroptosis inhibitor Ferrostatin 1 (Fer-1), antioxidant NAC, and the iron supplement Fe were added. We found that IL-6 decreased the activity, promoted lipid peroxidation, disrupted iron homeostasis of BEAS-2B cells, and induced iron death in bronchial epithelial BEAS-2B cells. However, pretreatment with Ferrostatin-1 (Fer-1) and antioxidant NAC partially reversed the effect of IL-6 on lipid peroxidation and ferroptosis in BEAS-2B cells, while Fe augmented the effect. Overall, IL-6 promotes ferroptosis in bronchial epithelial cells by inducing reactive oxygen species (ROS)-dependent lipid peroxidation and disrupting iron homeostasis.

Circulating miRNA expression in asthmatics is age-related and associated with clinical asthma parameters, respiratory function and systemic inflammation

Background

The course of asthma may differ between elderly asthmatics (EA) and non-elderly asthmatics (nEA), which may be partially associated with an age-dependent aberrant immune response. The aim of the study was to determine the influence of serum miRNA expression on asthma characteristics and systemic inflammation markers in EA and nEA.

Methods

Control and severity of asthma, pulmonary function and FeNO were assessed in 28 EA and 31 nEA patients. The control group included 59 elderly and non-elderly healthy individuals. The expression of selected miRNAs in serum was measured with rt-PCR, and proinflammatory cytokine activity was assayed by ELISA or flow cytometry.

Results

No difference in serum miRNA expression was observed between the asthmatics and healthy controls. EA demonstrated lower expression of miRNA-106a and miRNA-126a than nEA (p = 0.003 and p = 0.02) and EC had lower expression of miRNA-146a, -126a, -106a and 19b than nEC (p = 0.001, p = 0.003, p = 0.005 and p < 0.001 respectively). Only nEA demonstrated a relationship between the expression of selected miRNAs and the level of asthma control (assessed with ACT) and with airway inflammation, measured by FeNO level. All patients with asthma demonstrated elevated TNFα, IL-6 and sTNF RI levels compared to controls (p = 0.026, p = 0.03 and p < 0.001 respectively). EA demonstrated a higher TNFα level than EC (p < 0.001), and EA had a higher level of sTNF RI than nEA (p < 0.001). A significant correlation was observed between serum levels of proinflammatory cytokines and selected miRNAs.

Conclusion

Serum miRNA expression was found to correlate with clinical characteristics of asthma and systemic inflammation in an age-dependent fashion, suggesting that miRNA may differentially contribute to asthma pathogenesis in elderly and non-elderly patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01769-x.

The Predictive Role of Biomarkers and Genetics in Childhood Asthma Exacerbations

Asthma exacerbations are associated with significant childhood morbidity and mortality. Recurrent asthma attacks contribute to progressive loss of lung function and can sometimes be fatal or near-fatal, even in mild asthma. Exacerbation prevention becomes a primary target in the management of all asthmatic patients. Our work reviews current advances on exacerbation predictive factors, focusing on the role of non-invasive biomarkers and genetics in order to identify subjects at higher risk of asthma attacks. Easy-to-perform tests are necessary in children; therefore, interest has increased on samples like exhaled breath condensate, urine and saliva. The variability of biomarker levels suggests the use of seriate measurements and composite markers. Genetic predisposition to childhood asthma onset has been largely investigated. Recent studies highlighted the influence of single nucleotide polymorphisms even on exacerbation susceptibility, through involvement of both intrinsic mechanisms and gene-environment interaction. The role of molecular and genetic aspects in exacerbation prediction supports an individual-shaped approach, in which follow-up planning and therapy optimization take into account not only the severity degree, but also the risk of recurrent exacerbations. Further efforts should be made to improve and validate the application of biomarkers and genomics in clinical settings.

Mixed Sputum Granulocyte Longitudinal Impact on Lung Function in the Severe Asthma Research Program

Rationale: Some reports indicate longitudinal variability in sputum differential cell counts, whereas others describe stability. Highly variable sputum eosinophil percentages are associated with greater lung function loss than persistently elevated eosinophil percentages, but elevated neutrophils are linked to more severe asthma.Objectives: To examine sputum granulocyte stability or variability longitudinally and associations with important clinical characteristics.Methods: The SARP III (Severe Asthma Research Program III) cohort underwent comprehensive phenotype characterization at baseline and annually over 3 years. Adult subjects with acceptable sputum levels were assigned to one of three longitudinal sputum groups: eosinophils predominantly <2%, eosinophils predominantly ≥2%, or highly variable eosinophil percentages (>2 SDs determined from independent, repeated baseline eosinophil percentages). Subjects were similarly assigned to one of three longitudinal neutrophil groups with a 50% cut point.Measurements and Main Results: The group with predominantly <2% sputum eosinophils had the highest lung function (prebronchodilator FEV₁% predicted, P < 0.01; FEV₁/FVC ratio, P < 0.001) at baseline and throughout 3 years compared with other eosinophil groups. Healthcare use did not differ, although the highly variable eosinophil group reported more asthma exacerbations at Year 3. Longitudinal neutrophil groups showed few differences. However, a combination of predominantly ≥2% eosinophil and ≥50% neutrophil groups resulted in the lowest prebronchodilator FEV₁% predicted (P = 0.049) compared with the combination with predominantly <2% eosinophils and<50% neutrophils.Conclusions: Subjects with predominantly ≥2% sputum eosinophils in combination with predominantly ≥50% neutrophils showed greater loss of lung function, whereas those with highly variable sputum eosinophils had greater healthcare use.

Blood tryptase and thymic stromal lymphopoietin levels predict the risk of exacerbation in severe asthma

Some patients with severe asthma experience exacerbations despite receiving multiple therapy. The risk of exacerbation and heterogeneous response to treatment may be associated with specific inflammatory molecules that are responsive or resistant to corticosteroids. We aimed to identify the independent factors predictive for the future risk of exacerbation in patients with severe asthma. In this multi-center prospective observational study, 132 patients with severe asthma were enrolled and divided into exacerbation (n = 52) and non-exacerbation (n = 80) groups on the basis of exacerbation rate after a 1-year follow-up period. We found that previous history of severe-to-serious exacerbation, baseline blood eosinophil counts (≥ 291cells/μL), and serum tryptase (≤ 1448 pg/mL) and thrymic stromal lymphopoietin (TSLP) levels (≥ 25 pg/mL) independently predicted the future development of exacerbation with adjusted odds ratios (AOR) of 3.27, 6.04, 2.53 and 8.67, respectively. Notably, the patients with high blood eosinophil counts and low tryptase levels were likely to have more exacerbations than those with low blood eosinophil counts and high tryptase levels (AOR 16.9). TSLP potentially played the pathogenic role across different asthma phenotypes. TSLP and tryptase levels may be implicated in steroid resistance and responsiveness in the asthma inflammatory process. High blood eosinophil counts and low serum tryptase levels predict a high probability of future asthma exacerbation.

Relationship of Soluble Interleukin-6 Receptors With Asthma: A Mendelian Randomization Study

Purpose: Emerging evidence suggests a potential role of interleukin-6 pathways—trans-signaling with soluble interleukin-6 receptors—in the asthma pathobiology. Despite the evidence for their associations with asthma, the causal role of soluble interleukin-6 receptors remains uncertain. We investigated the relations of soluble interleukin-6 receptors with asthma and its major phenotypes.

Methods: We conducted a two-sample Mendelian randomization study. As genetic instruments, we selected 33 independent cis-acting variants strongly associated with the level of plasma soluble interleukin-6 receptor in the INTERVAL study. To investigate the association of variants with asthma and its phenotypes, we used genome-wide association study data from the UK Biobank. We combined variant-specific causal estimates by the inverse-variance weighted method for each outcome.

Results: Genetically-instrumented soluble interleukin-6 receptor level was associated with a significantly higher risk of overall asthma (OR per one standard deviation increment in inverse-rank normalized soluble interleukin-6 receptor level, 1.02; 95%CI, 1.01–1.03; P = 0.004). Sensitivity analyses demonstrated consistent results and indicated no directional pleiotropy—e.g., MR-Egger (OR, 1.03; 95%CI, 1.01–1.05; P = 0.002; P_intercept =0.37). In the stratified analysis, the significant association persisted across asthma phenotypes—e.g., childhood asthma (OR, 1.05; 95%CI, 1.02–1.08; P < 0.001) and obese asthma (OR, 1.02; 95%CI 1.01–1.03; P = 0.007). Sensitivity analysis using 16 variants selected with different thresholds also demonstrated significant associations with overall asthma and its phenotypes.

Conclusion: Genetically-instrumented soluble interleukin-6 receptor level was causally associated with modestly but significantly higher risks of asthma and its phenotypes. Our observations support further investigations into identifying specific endotypes in which interleukin-6 pathways may play major roles.

The basic immunology of asthma

In many asthmatics, chronic airway inflammation is driven by IL-4-, IL-5-, and IL-13-producing Th2 cells or ILC2s. Type 2 cytokines promote hallmark features of the disease such as eosinophilia, mucus hypersecretion, bronchial hyperresponsiveness (BHR), IgE production, and susceptibility to exacerbations. However, only half the asthmatics have this "type 2-high" signature, and "type 2-low" asthma is more associated with obesity, presence of neutrophils, and unresponsiveness to corticosteroids, the mainstay asthma therapy. Here, we review the underlying immunological basis of various asthma endotypes by discussing results obtained from animal studies as well as results generated in clinical studies targeting specific immune pathways.

Increased IL-6 and Potential IL-6 trans-signalling in the airways after an allergen challenge

BACKGROUND

In asthma, IL-6 is a potential cause of enhanced inflammation, tissue damage and airway dysfunction. IL-6 signalling is regulated by its receptor, which is composed of two proteins, IL-6R and GP130. In addition to their membrane form, these two proteins may be found as extracellular soluble forms. The interaction of IL-6 with soluble IL-6R (sIL-6R) can trigger IL-6 trans-signalling in cells lacking IL-6R. Conversely, the soluble form of GP130 (sGP130) competes with its membrane form to inhibit IL-6 trans-signalling.

OBJECTIVES

We aimed to analyse IL-6 trans-signalling proteins in the airways of subjects after an allergen challenge.

METHODS

We used a model of segmental bronchoprovocation with an allergen (SBP-Ag) in human subjects with allergy. Before and 48 h after SBP-Ag, bronchoalveolar lavages (BALs) allowed for the analysis of proteins in BAL fluids (BALFs) by ELISA, and membrane proteins on the surface of BAL cells by flow cytometry. In addition, we performed RNA sequencing (RNA-seq) and used proteomic data to further inform on the expression of the IL-6R subunits by eosinophils, bronchial epithelial cells and lung fibroblasts. Finally, we measured the effect of IL-6 trans-signalling on bronchial fibroblasts, in vitro.

RESULTS

IL-6, sIL-6R, sGP130 and the molar ratio of sIL-6R/sGP130 increased in the airways after SBP-Ag, suggesting the potential for enhanced IL-6 trans-signalling activity. BAL lymphocytes, monocytes and eosinophils displayed IL-6R on their surface and were all possible providers of sIL-6R, whereas GP130 was highly expressed in bronchial epithelial cells and lung fibroblasts. Finally, bronchial fibroblasts activated by IL-6 trans-signalling produced enhanced amounts of the chemokine, MCP-1 (CCL2).

CONCLUSION AND CLINICAL RELEVANCE

After a bronchial allergen challenge, we found augmentation of the elements of IL-6 trans-signalling. Allergen-induced IL-6 trans-signalling activity can activate fibroblasts to produce chemokines that can further enhance inflammation and lung dysfunction.

Mechanisms of non-type 2 asthma

Non-type 2 inflammation (Non-T2)-mediated asthma is difficult to define due to lack of signature biomarkers. It exists in the absence of T2-high or eosinophilic inflammation and includes neutrophilic and paucigranulocytic subtypes. Several cell types and cytokines, including Th1, Th17, IL-6, and IL-17, contribute to mechanisms of non-T2 asthma. Neutrophil extracellular traps (NETs) and inflammasome activation likely play a role in severe neutrophilic asthma. Several mechanisms lead to uncoupling of airway hyperresponsiveness and remodeling from airway inflammation in paucigranulocytic asthma. Recent research on transcriptomics and proteomics in non-T2 asthma is discussed in this review. Investigations of specific drug therapies for non-T2 asthma have been disappointing, and remain an important area for future clinical studies.

Biomarkers for Overweight in Adult-Onset Asthma

Purpose

Overweight and obesity are associated with one of the severe phenotypes of asthma, with an increased rate of exacerbations, low level of lung function, and reduced response to corticosteroid therapy. The present study focused on identifying useful biomarkers of severity in overweight patients with adult-onset asthma using real-world data.

Patients and Methods

A total of 56 patients with adult-onset asthma who visited Saga University Hospital between 2018 and 2019 were retrospectively reviewed. Overweight was defined as a body mass index (BMI) greater than 25 kg/m². Blood eosinophils, cytokines, and chemokines were compared between non-overweight asthma and overweight asthma patients.

Results

Overweight asthma patients had a higher annual exacerbation rate, lower pulmonary function even when treated frequently with high-dose inhaled corticosteroids, and a significantly lower percentage of eosinophils and lower eosinophil count compared to non-overweight asthma patients (p<0.01, p=0.03). Moreover, the percentage of eosinophils was significantly negatively correlated with BMI (ρ=−0.38, p<0.01) (Figure 1). On serum cytokine and chemokine analyses, the overweight asthma group included significantly more patients with a lower level of tissue growth factor α (TGF-α) (1.1 pg/mL) and higher levels of hsIL-6 (2.5 pg/mL), RANTES/CCL5 (298.5 pg/mL), and vascular endothelial growth factor A (VEGF-A) (63.7 pg/mL), than the non-overweight asthma group (p=0.02, p<0.01, p=0.02, p=0.01, respectively).

Conclusion

The present study showed that overweight patients with adult-onset asthma were characterized by a higher rate of annual exacerbations and worse lung function despite treatment with high-dose inhaled corticosteroids and lower blood eosinophil counts than non-overweight patients with asthma. On blood cytokine and chemokine analyses, a low level of TGF-α and high levels of hsIL-6, RANTES/CCL5, and VEGF-A might be biomarkers reflecting the pathophysiology in overweight patients with asthma.

Type 2-high asthma is associated with a specific indoor mycobiome and microbiome

Background

The links between microbial environmental exposures and asthma are well documented, but no study has combined deep sequencing results from pulmonary and indoor microbiomes of patients with asthma with spirometry, clinical, and endotype parameters.

Objective

The goal of this study was to investigate the links between indoor microbial exposures and pulmonary microbial communities and to document the role of microbial exposures on inflammatory and clinical outcomes of patients with severe asthma (SA).

Methods

A total of 55 patients with SA from the national Cohort of Bronchial Obstruction and Asthma cohort were enrolled for analyzing their indoor microbial flora through the use of electrostatic dust collectors (EDCs). Among these patients, 22 were able to produce sputum during “stable” or pulmonary “exacerbation” periods and had complete pairs of EDC and sputum samples, both collected and analyzed. We used amplicon targeted metagenomics to compare microbial communities from EDC and sputum samples of patients according to type 2 (T2)-asthma endotypes.

Results

Compared with patients with T2-low SA, patients with T2-high SA exhibited an increase in bacterial α-diversity and a decrease in fungal α-diversity of their indoor microbial florae, the latter being significantly correlated with fraction of exhaled nitric oxide levels. The β-diversity of the EDC mycobiome clustered significantly according to T2 endotypes. Moreover, the proportion of fungal taxa in common between the sputum and EDC samples was significantly higher when patients exhibited acute exacerbation.

Conclusion

These results illustrated, for the first time, a potential association between the indoor mycobiome and clinical features of patients with SA, which should renew interest in deciphering the interactions between indoor environment, fungi, and host in asthma.

Therapeutic efficacy of IL-17A neutralization with corticosteroid treatment in a model of antigen-driven mixed-granulocytic asthma

Many mouse models of allergic asthma exhibit eosinophil-predominant cellularity rather than the mixed-granulocytic cytology in steroid-unresponsive severe disease. Therefore, we sought to implement a novel mouse model of antigen-driven, mixed-granulocytic, severe allergic asthma to determine biomarkers of the disease process and potential therapeutic targets. C57BL/6J wild-type, interleukin-6 knockout (IL-6-/-), and IL-6 receptor knockout (IL-6R-/-), mice were injected with an emulsion of complete Freund's adjuvant and house dust mite antigen (CFA/HDM) on day 1. Dexamethasone, a lymphocyte-depleting biological, or anti-IL-17A was administered during the intranasal HDM challenge on days 19-22. On day 23, the CFA/HDM model elicited mixed bronchoalveolar lavage (BAL) cellularity (typically 80% neutrophils and 10% eosinophils), airway hyperresponsiveness (AHR) to methacholine, diffusion impairment, lung damage, body weight loss, corticosteroid resistance, and elevated levels of serum amyloid A (SAA), pro-inflammatory cytokines, and T helper type 1/ T helper type 17 (Th1/Th17) cytokines compared with eosinophilic models of HDM-driven allergic airway disease. BAL cells in IL-6- or IL-6R-deficient mice were predominantly eosinophilic and associated with elevated T helper type 2 (Th2) and reduced Th1/Th17 cytokine production, along with an absence of SAA. Nevertheless, AHR remained in IL-6-deficient mice even when dexamethasone was administered. However, combined administration of anti-IL-17A and systemic corticosteroid significantly attenuated both overall and neutrophilic airway inflammation and also reduced AHR and body weight loss. Inhibition of IL-17A combined with systemic corticosteroid treatment during antigen-driven exacerbations may provide a novel therapeutic approach to prevent the pathological pulmonary and constitutional changes that greatly impact patients with the mixed-granulocytic endotype of severe asthma.

Beyond type 2 cytokines in asthma - new insights from old clinical trials

Introduction: Human asthma is a heterogeneous disorder on molecular, pathological, and clinical levels. The paradigm of asthma as an allergic process driven by type 2 cytokines and mediators has led to targeted biologic therapies resulting in some clinical benefit in patient subsets. However, some patient subsets and clinical manifestations do not benefit from these interventions, thus redefining unmet needs. Clinical studies of type 2 directed therapies have identified new targets under investigation in clinical development; these include epithelial alarmins, non-type 2 cytokines, cytokine receptor signaling, mast cells and neuroinflammation.Areas covered: We consider lessons learned concerning asthma pathogenesis from observational studies and clinical trials of biologic agents that target type 2 mediators. We also provide a perspective on emerging therapeutic hypotheses to target processes independent of or orthogonal to type 2 inflammation in asthma.Expert opinion: Type 2 inflammation is continuous, not discrete, and is likely a modifier of underlying dysregulated airway physiology. Non-type 2 inflammatory mediators (e.g., IL17, IL6, IFNs), microbiome, alarmins (e.g., TSLP, IL33), mast cells and sensory neurons may represent orthogonal targets to type 2 mediators. There is a need to better match targets and outcome measures in biologically defined patient populations to appropriately test hypotheses in the clinic.