Longitudinal Outcomes of Severe Asthma: Real-World Evidence of Multidimensional Analyses

Immune Cell-Mediated Autoimmune Responses in Severe Asthma

Severe asthma (SA) has heterogeneous inflammatory phenotypes characterized by persistent airway inflammation (eosinophilic and/or neutrophilic inflammation) and remodeling. Various immune cells (eosinophils, neutrophils, and macrophages) become more activated and release inflammatory mediators and extracellular traps, damaging the protective barrier of airway epithelial cells and further activating other immune and structural cells. These cells play a role in autoimmune responses in asthmatic airways, where the adaptive immune system generates autoantibodies, inducing immunoglobulin G-dependent airway inflammation. Recent studies have suggested that adult asthmatics had high titers of autoantibodies associated with asthma severity, although pathogenic factors or diagnostic criteria are not well-defined. This challenge is further compounded by asthmatics with the autoimmune responses showing therapy insensitivity or failure to current pharmacological and biological treatment. This review updates emerging mechanisms of autoimmune responses in asthmatic airways and provides insights into their roles, proposing potential biomarkers and therapeutic targets for SA.

Predictors of persistent poor control and validation of ASSESS score: Longitudinal 5-year follow-up of severe asthma cohort

Background

Longitudinal predictors of persistent poor asthma control in severe asthma (SA) cohort remain scarce. The predictive value of the asthma severity scoring system (ASSESS) in the SA cohort outside the original study and in the Asian population is unknown.

Objective

We sought to determine the 5-year longitudinal outcome of patients with SA and validate the use of ASSESS score in predicting future outcomes in SA.

Methods

A prospective longitudinal observational study of patients with SA attending the multidisciplinary specialist SA clinic of the Singapore General Hospital from 2011 to 2021 was conducted. The number of exacerbations and asthma control test results were recorded yearly for 5 consecutive years. The ASSESS score was computed at baseline, and the area under the receiver-operating characteristic curve for predicting persistent poor asthma control was generated.

Results

Of the 489 patients recruited into the study, 306 patients with 5-year follow-up data were analyzed. Seventy-three percent had type 2 inflammation with increased overall exacerbations over 5 years (rate ratio, 2.55; 95% CI, 1.31-4.96; P = .006) relative to non-type 2 SA. In the multivariate model, bronchiectasis, gastroesophageal reflux disease, and an asthma control test score of less than 20 were significantly associated with persistent poor asthma control over 5 years. ASSESS scores were good at predicting persistent poor asthma control with an area under the receiver-operating characteristic curve of 0.71 (95% CI, 0.57-0.84).

Conclusions

Bronchiectasis and gastroesophageal reflux disease are predictors for persistent poor asthma control and targeted traits for precision medicine in SA. The ASSESS score has a good prediction for persistent poor asthma control over 5 years.

Contribution of monocyte and macrophage extracellular traps to neutrophilic airway inflammation in severe asthma

BACKGROUND

Increased blood/sputum neutrophil counts are related to poor clinical outcomes of severe asthma (SA), where we hypothesized that classical monocytes (CMs)/CM-derived macrophages (Mφ) are involved. We aimed to elucidate the mechanisms of how CMs/Mφ induce the activation of neutrophils/innate lymphoid cells (ILCs) in SA.

METHODS

Serum levels of monocyte chemoattractant protein-1 (MCP-1) and soluble suppression of tumorigenicity 2 (sST2) were measured from 39 patients with SA and 98 those with nonsevere asthma (NSA). CMs/Mφ were isolated from patients with SA (n = 19) and those with NSA (n = 18) and treated with LPS/interferon-gamma. Monocyte/M1Mφ extracellular traps (MoETs/M1ETs) were evaluated by western blotting, immunofluorescence, and PicoGreen assay. The effects of MoETs/M1ETs on neutrophils, airway epithelial cells (AECs), ILC1, and ILC3 were assessed in vitro and in vivo.

RESULTS

The SA group had significantly higher CM counts with increased migration as well as higher levels of serum MCP-1/sST2 than the NSA group. Moreover, the SA group had significantly greater production of MoETs/M1ETs (from CMs/M1Mφ) than the NSA group. The levels of MoETs/M1ETs were positively correlated with blood neutrophils and serum levels of MCP-1/sST2, but negatively correlated with FEV1%. In vitro/in vivo studies demonstrated that MoETs/M1ETs could activate AECs, neutrophils, ILC1, and ILC3 by increased migration as well as proinflammatory cytokine production.

CONCLUSIONS

CM/Mφ-derived MoETs/M1ETs could contribute to asthma severity by enhancing neutrophilic airway inflammation in SA, where modulating CMs/Mφ may be a potential therapeutic option.

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.

Long-term clinical outcomes of aspirin-exacerbated respiratory disease: Real-world data from an adult asthma cohort

BACKGROUND

Aspirin-exacerbated respiratory disease (AERD) is a phenotype of severe asthma, but its disease course has not been well documented compared with that of aspirin-tolerant asthma (ATA).

OBJECTIVES

This study aimed to investigate the long-term clinical outcomes between AERD and ATA.

METHODS

AERD patients were identified by the diagnostic code and positive bronchoprovocation test in a real-world database. Longitudinal changes in lung function, blood eosinophil/neutrophil counts, and annual numbers of severe asthma exacerbations (AEx) were compared between the AERD and the ATA groups. Within a year after baseline, two or more severe AEx events indicated severe AERD, whereas less than two AEx events indicated nonsevere AERD.

RESULTS

Among asthmatics, 353 had AERD in which 166 and 187 patients had severe and nonsevere AERD, respectively, and 717 had ATA. AERD patients had significantly lower FEV1%, higher blood neutrophil counts, and higher sputum eosinophils (%) (all p < .05) as well as higher levels of urinary LTE4 and serum periostin, and lower levels of serum myeloperoxidase and surfactant protein D (all p < .01) than those with ATA. In a 10-year follow-up, the severe AERD group maintained lower FEV1% with more severe AEs than the nonsevere AERD group.

CONCLUSION AND CLINICAL RELEVANCE

We demonstrated that AERD patients presented poorer long-term clinical outcomes than ATA patients in real-world data analyses.

Tissue Inhibitor of Metalloproteinase-1 Enhances Eosinophilic Airway Inflammation in Severe Asthma

PURPOSE

Severe asthma (SA) is characterized by persistent airway inflammation and remodeling, followed by lung function decline. The present study aimed to evaluate the role of tissue inhibitor of metalloproteinase-1 (TIMP-1) in the pathogenesis of SA.

METHODS

We enrolled 250 adult asthmatics (54 with SA and 196 with non-SA) and 140 healthy controls (HCs). Serum TIMP-1 levels were determined by enzyme-linked immunosorbent assay. The release of TIMP-1 from airway epithelial cells (AECs) in response to stimuli as well as the effects of TIMP-1 on the activations of eosinophils and macrophages were evaluated in vitro and in vivo.

RESULTS

Significantly higher levels of serum TIMP-1 were noted in asthmatics than in HCs, in the SA group than in non-SA group, and in the type 2 SA group than in non-type 2 SA group (P < 0.01 for all). A negative correlation between serum TIMP-1 and FEV₁% values (r = -0.400, P = 0.003) was noted in the SA group. In vitro study demonstrated that TIMP-1 was released from AECs in response to poly I:C, IL-13, eosinophil extracellular traps (EETs) and in coculture with eosinophils. TIMP-1-stimulated mice showed eosinophilic airway inflammation, which was not completely suppressed by steroid treatment. In vitro and in vivo functional studies showed that TIMP-1 directly activated eosinophils and macrophages, and induced the release of EETs and macrophages to polarize toward M2 subset, which was suppressed by anti-TIMP-1 antibody.

CONCLUSIONS

These findings suggest that TIMP-1 enhances eosinophilic airway inflammation and that serum TIMP-1 may be a potential biomarker and/or therapeutic target for type 2 SA.

Relationships Between High-Resolution Computed Tomographic Features and Lung Function Trajectory in Patients With Asthma

PURPOSE

A subset of asthmatics suffers from persistent airflow limitation, known as remodeled asthma, despite optimal treatment. Typical quantitative scoring methods to evaluate structural changes of airway remodeling on high-resolution computed tomography (HRCT) are time-consuming and laborious. Thus, easier and simpler methods are required in clinical practice. We evaluated the clinical usefulness of a simple, semi-quantitative method based on 8 HRCT parameters by comparing asthmatics with a persistent decline of post-bronchodilator (BD)-FEV1 to those with a BD-FEV1 that normalized over time and evaluated the relationships of the parameters with BD-FEV1.

METHODS

Asthmatics (n = 59) were grouped into 5 trajectories (Trs) according to the changes of BD-FEV1 over 1 year. After 9-12 months of guideline-based treatment, HRCT parameters including emphysema, bronchiectasis, anthracofibrosis, bronchial wall thickening (BWT), fibrotic bands, mosaic attenuation on inspiration, air-trapping on expiration, and centrilobular nodules were classified as present (1) or absent (0) in 6 zones.

RESULTS

The Tr5 group (n = 11) was older and exhibited a persistent decline in BD-FEV1. The Tr5 and Tr4 groups (n = 12), who had a lower baseline BD-FEV1 that normalized over time, had longer durations of asthma, frequent exacerbations, and higher doses of steroid use compared to the Tr1-3 groups (n = 36), who had a normal baseline BD-FEV1. The Tr5 group had higher emphysema and BWT scores than the Tr4 (P = 8.25E-04 and P = 0.044, respectively). Scores for the other 6 parameters were not significantly different among the Tr groups. BD-FEV1 was inversely correlated with the emphysema and BWT scores in multivariate analysis (P = 1.70E-04, P = 0.006, respectively).

CONCLUSIONS

Emphysema and BWT are associated with airway remodeling in asthmatics. Our simple, semi-quantitative scoring system based on HRCT may be an easy-to-use method for estimating airflow limitation.

Investigational approaches for unmet need in severe asthma

INTRODUCTION

Molecular antibodies (mAb) targeting inflammatory mediators are effective in T2-high asthma. The recent approval of Tezepelumab presents a novel mAb therapeutic option to those with T2-low asthma.

AREAS COVERED

We discuss a number of clinical problems pertinent to severe asthma which are less responsive to current therapies, such as persistent airflow obstruction and airway hyperresponsiveness. We discuss selected investigational approaches, including a number of candidate therapies under investigation in two adaptive platform trials currently in progress, with particular reference to this unmet need, as well as their potential in phenotypes such as neutrophilic asthma and obese asthma, which may or may not overlap with a T2-high phenotype.

EXPERT OPINION

The application of discrete targeting approaches to T2-low molecular phenotypes, including those phenotypes in which inflammation may not arise within the airway, has yielded variable results to date. Endotypes associated with T2-low asthma are likely to be diverse but await validation. Investigational therapeutic approaches must, likewise, be diverse if the goal of remission is to become attainable for all those living with asthma.

Serum Amyloid A1: A Biomarker for Neutrophilic Airway Inflammation in Adult Asthmatic Patients

Purpose

We evaluated the role of serum amyloid A1 (SAA1) in the pathogenesis of airway inflammation according to the phenotype of asthma.

Methods

One hundred twenty-two asthmatic patients and 60 healthy control subjects (HCs) were enrolled to measure SAA1 levels. The production of SAA1 from airway epithelial cells (AECs) and its effects on macrophages and neutrophils were investigated in vitro and in vivo.

Results

The SAA1 levels were significantly higher in sera of asthmatic patients than in those of HCs (P = 0.014); among asthmatics, patients with neutrophilic asthma (NA) showed significantly higher SAA1 levels than those with non-NA (P < 0.001). In vitro, polyinosinic:polycytidylic acid (Poly I-C) treatment markedly enhanced the production of SAA1 from AECs, which was further augmented by neutrophils; SAA1 could induce the production of interleukin (IL)-6, IL-8, and S100 calcium-binding protein A9 from AECs. Additionally, SAA1 activated neutrophils and macrophages isolated from peripheral blood of asthmatics, releasing neutrophil extracellular traps (NETs) and secreting proinflammatory cytokines presenting M1 phenotype, respectively. In ovalbumin-induced asthma mice, Poly I-C treatment significantly increased SAA1 levels as well as IL-17A/interferon-gamma/IL-33 levels in bronchoalveolar lavage fluid (BALF), leading to airway hyperresponsiveness and inflammation. The highest levels of SAA1 and neutrophilia were noted in the BALF and sera of the NA mouse model, followed by the mixed granulocytic asthma (MA) model. Especially, SAA1 induced IL-17/retinoic acid receptor-related orphan receptor γt expression from activated CD4+ T lymphocytes in asthmatic mice.

Conclusions

The results show that SAA1 could induce neutrophilic airway inflammation by activating neutrophils along with NET formation, M1 macrophages, and Th2/Th17 predominant cells, contributing to the phenotype of NA or MA.

Biomarkers for Severe Asthma: Lessons From Longitudinal Cohort Studies

Severe asthma (SA) is a heterogeneous disease characterized by uncontrolled symptoms, frequent exacerbations, and lung function decline. The discovery of phenotypes and endotypes of SA significantly improves our understanding of its pathophysiology and allows the advent of biologics blocking multiple molecular targets. The advances have mainly been made in type 2-high asthma associated with elevated type 2 inflammatory biomarkers such as immunoglobulin E (IgE), interleukins (IL)-4, IL-5, and IL-13. Previous clinical trials have demonstrated that type 2 biomarkers, including blood/sputum eosinophils and the fraction of exhaled nitric oxide (FeNO), were correlated to severe airway inflammation, persistent symptoms, frequent exacerbations, and the clinical efficacy of these biomarkers in predicting treatment outcomes of type 2-targeting biologics. However, it is well known that type 2 inflammation is partially attributable to the pathogenesis of SA. Although some recent studies have suggested that type 2-low and mixed phenotypes of asthma are important contributors to the heterogeneity of SA, many questions about these non-type 2 asthma phenotypes remain to be solved. Consequently, many efforts to investigate and find novel biomarkers for SA have also made in their methods. Many cross-sectional experimental studies in large-scale cohorts and randomized clinical trials have proved their value in understanding SA. More recently, real-world cohort studies have been in the limelight for SA research, which is unbiased and expected to give us an answer to the unmet needs of the heterogeneity of SA.