Proximal and Distal Bronchioles Contribute to the Pathogenesis of Non-Cystic Fibrosis Bronchiectasis

Non-Cystic Fibrosis Bronchiectasis in Adults: A Review

Importance

Non-cystic fibrosis (CF) bronchiectasis is a chronic lung condition caused by permanent bronchial dilatation and inflammation and is characterized by daily cough, sputum, and recurrent exacerbations. Approximately 500 000 people in the US have non-CF bronchiectasis.

Observations

Non-CF bronchiectasis may be associated with prior pneumonia, infection with nontuberculous mycobacteria or tuberculosis, genetic conditions (eg, α1-antitrypsin deficiency, primary ciliary dyskinesia), autoimmune diseases (eg, rheumatoid arthritis, inflammatory bowel disease), allergic bronchopulmonary aspergillosis, and immunodeficiency syndromes (eg, common variable immunodeficiency). Up to 38% of cases are idiopathic. According to US data, conditions associated with non-CF bronchiectasis include gastroesophageal reflux disease (47%), asthma (29%), and chronic obstructive pulmonary disease (20%). The prevalence of non-CF bronchiectasis increases substantially with age (7 per 100 000 in individuals 18-34 years vs 812 per 100 000 in those ≥75 years) and is more common in women than men (180 vs 95 per 100 000). Diagnosis is confirmed with noncontrast chest computed tomography showing dilated airways and often airway thickening and mucus plugging. Initial diagnostic evaluation involves blood testing (complete blood cell count with differential); immunoglobulin quantification testing (IgG, IgA, IgE, and IgM); sputum cultures for bacteria, mycobacteria, and fungi; and prebronchodilator and postbronchodilator spirometry. Treatment includes airway clearance techniques; nebulization of saline to loosen tenacious secretions; and regular exercise, participation in pulmonary rehabilitation, or both. Inhaled bronchodilators (β-agonists and antimuscarinic agents) and inhaled corticosteroids are indicated for patients with bronchiectasis who have asthma or chronic obstructive pulmonary disease. Exacerbations of bronchiectasis, which typically present with increased cough and sputum and worsened fatigue, are associated with progressive decline in lung function and decreased quality of life. Exacerbations should be treated with oral or intravenous antibiotics. Individuals with 3 or more exacerbations of bronchiectasis annually may benefit from long-term inhaled antibiotics (eg, colistin, gentamicin) or daily oral macrolides (eg, azithromycin). Lung transplant may be considered for patients with severely impaired pulmonary function, frequent exacerbations, or both. Among patients with non-CF bronchiectasis, mortality is higher for those with frequent and severe exacerbations, infection with Pseudomonas aeruginosa, and comorbidities, such as chronic obstructive pulmonary disease.

Conclusions and Relevance

Non-CF bronchiectasis is a chronic lung condition that typically causes chronic cough and daily sputum production. Exacerbations are associated with progressive decline in lung function and decreased quality of life. Management involves treatment of conditions associated with bronchiectasis, airway clearance techniques, oral or intravenous antibiotics for acute exacerbations, and consideration of long-term inhaled antibiotics or oral macrolides for patients with 3 or more exacerbations annually.

Pulmonary Nontuberculous Mycobacteria Infection in Bronchiectasis: A Narrative Review of Current Status and Future

Background and Aims

Pulmonary nontuberculous mycobacteria (NTM) infection and bronchiectasis are two distinct respiratory conditions, but bronchiectasis and pulmonary NTM infections are closely associated. NTM can cause bronchiectasis. However, bronchiectasis can create a favorable environment for NTM colonization and exacerbate the progression of NTM. Managing both conditions typically requires a comprehensive approach that addresses infection and the underlying structural lung damage.

Methods

To perform this review, the author retrieved and assessed relevant articles related to NTM and bronchiectasis that have been published to date from databases, including PubMed/MEDLINE, Scopus, and Google Scholar.

Results

In this review, the close relationship between pulmonary NTM and bronchiectasis is described from the viewpoints of diagnosis, epidemiology, Pseudomonas aeruginosa, host susceptibility, females and NTM, and treatment.

Conclusion

Timely diagnosis and management of NTM infections, especially in individuals with underlying risk factors, are essential to prevent disease progression and improve the quality of life of affected individuals.

Refractory phenotype of Aspergillus-sensitized asthma with bronchiectasis and allergic bronchopulmonary aspergillosis

Background

Sensitization to Aspergillus, mucus plugs, and bacterial colonization may coexist and relate to a refractory phenotype during follow-up in asthma with bronchiectasis and allergic bronchopulmonary aspergillosis (ABPA).

Objective

This study aimed to clarify the features of Aspergillus-sensitized refractory asthma with bronchiectasis and determine the refractory phenotype in this population and ABPA.

Methods

This study included cases of the oldest available Aspergillus fumigatus-specific IgE data and chest computed tomography images from a nationwide survey of refractory asthma with bronchiectasis. The characteristics of the A fumigatus-IgE positive (Af sIgE+) group were investigated and compared with its nonsensitized counterpart (Af sIgE-) and ABPA group. Cluster analysis was conducted to determine the refractory phenotype.

Results

The Af sIgE+ group (n = 35) demonstrated type 2 inflammation levels intermediate between the ABPA (n = 42) and Af sIgE- (n = 38) groups while exhibiting higher blood monocyte counts than the Af sIgE- group. Cluster analysis conducted in patients with ABPA and Af sIgE+ newly determined 2 clusters: one was characterized by a younger age of asthma onset with fungal detection in sputum, and the other was characterized by mucus plugs and inflammation with eosinophils and monocytes, which was significantly related to mucus plugs, airflow limitation, and trend to show exacerbation. In the latter cluster, mucus plugs persisted, and 30% yielded Pseudomonas aeruginosa in the sputum <5 years later.

Conclusion

The refractory phenotype with persistent mucus plugs was identified in Aspergillus-sensitized refractory asthma with bronchiectasis and ABPA. Mucus plug prevention is warranted.

Targeting neutrophil serine proteases in bronchiectasis

Persistent neutrophilic inflammation is a central feature in both the pathogenesis and progression of bronchiectasis. Neutrophils release neutrophil serine proteases (NSPs), such as neutrophil elastase (NE), cathepsin G and proteinase 3. When chronically high levels of free NSP activity exceed those of protective antiproteases, structural lung destruction, mucosal-related defects, further susceptibility to infection and worsening of clinical outcomes can occur. Despite the defined role of prolonged, high levels of NSPs in bronchiectasis, no drug that controls neutrophilic inflammation is licensed for the treatment of bronchiectasis. Previous methods of suppressing neutrophilic inflammation (such as direct inhibition of NE) have not been successful; however, an emerging therapy designed to address neutrophil-mediated pathology, inhibition of the cysteine protease cathepsin C (CatC, also known as dipeptidyl peptidase 1), is a promising approach to ameliorate neutrophilic inflammation, since this may reduce the activity of all NSPs implicated in bronchiectasis pathogenesis, and not just NE. Current data suggest that CatC inhibition may effectively restore the protease-antiprotease balance in bronchiectasis and improve disease outcomes as a result. Clinical trials for CatC inhibitors in bronchiectasis have reported positive phase III results. In this narrative review, we discuss the role of high NSP activity in bronchiectasis, and how this feature drives the associated morbidity and mortality seen in bronchiectasis. This review discusses therapeutic approaches aimed at treating neutrophilic inflammation in the bronchiectasis lung, summarising clinical trial outcomes and highlighting the need for more treatment strategies that effectively address chronic neutrophilic inflammation in bronchiectasis.

Toward better cures for Mycobacterium abscessus lung disease

SUMMARYThe opportunistic pathogen Mycobacterium abscessus (Mab) causes fatal lung infections that bear similarities-and notable differences-with tuberculosis (TB) pulmonary disease. In contrast to TB, no antibiotic is formally approved to treat Mab disease, there is no reliable cure, and the discovery and development pipeline is incredibly thin. Here, we discuss the factors behind the unsatisfactory cure rates of Mab disease, namely intrinsic resistance and persistence of the pathogen, and the use of underperforming, often parenteral and toxic, repurposed drugs. We propose preclinical strategies to build injectable-free sterilizing and safe regimens: (i) prioritize oral bactericidal antibiotic classes, with an initial focus on approved agents or advanced clinical candidates to provide immediate options for desperate patients, (ii) test drug combinations early, (iii) optimize novel leads specifically for M. abscessus, and (iv) consider pharmacokinetic-pharmacodynamic targets at the site of disease, the lung lesions in which drug tolerant bacterial populations reside. Knowledge and tool gaps in the preclinical drug discovery process are identified, including validated mouse models and computational platforms to enable in vitro mouse-human translation. We briefly discuss recent advances in clinical development, the need for readouts and biomarkers that correlate with cure, and clinical trial concepts adapted to the uniqueness of Mab patient populations for new regimen development. In an era when most pharmaceutical firms have withdrawn from antimicrobial drug discovery, the breakthroughs needed to fill the regimen development pipeline will likely come from partnerships between academia, biotech, pharma, non-profit organizations, and governments, with incentives that reward cooperation.

Comparison of Longitudinal Outcomes in Children with Primary Ciliary Dyskinesia and Cystic Fibrosis

Rationale: Primary ciliary dyskinesia (PCD) and cystic fibrosis (CF) are both genetic diseases of mucociliary clearance resulting in progressive lung disease with onset in early life. PCD is often considered to be milder than CF in childhood, based on minimal evidence. Similar to CF, genotype-phenotype associations exist in PCD; pathogenic variants in CCDC39 and CCDC40, causing inner dynein arm/microtubular defects (IDA/MTD), are associated with more severe disease. Objectives: To compare longitudinal outcomes in matched children with PCD and CF. We hypothesized that children with PCD with IDA/MTD defects would have lower lung function but better nutritional indices than matched children with CF with minimal function genotypes (i.e., those associated with pancreatic insufficiency). Methods: Children with PCD enrolled in a prospective, multicenter, observational study were matched with patients with CF from the Cystic Fibrosis Foundation Patient Registry by birth cohort, age, sex, race/ethnicity, and year of study visit. The association of disease group overall and by severity class (PCD-IDA/MTD vs. all other defects and CF-minimal vs. residual function) with longitudinal outcomes up to age 17 was evaluated with cubic spline mixed effects models. Results: Groups included 136 children with PCD (40 IDA/MTD, 96 other) and 476 with CF (446 minimal function, 30 residual function). Below age 14, the PCD group had similar or lower estimated mean forced expiratory volume in 1 second percent predicted compared with CF (e.g., at age 10, -5.4% predicted lower; 95% confidence interval [CI], -7.7, -3.1). Compared with the CF-minimal function (pancreatic insufficient) group, the PCD-IDA/MTD group had similar body mass index; estimated mean forced expiratory volume in 1 second percent predicted was significantly lower by age 10 (mean difference, -10.6%; 95% CI, -14.7, -6.4), increasing at age 14 (mean difference, -15.7%; 95% CI, -20.3, -11.2). The CF cohort had increased prevalence of Pseudomonas aeruginosa cultured on one or more occasions compared with children with PCD (67% vs. 27%; P < 0.001); there was no difference in the prevalence of P. aeruginosa between children with PCD-IDA/MTD and PCD-other. Conclusions: In childhood, average lung function abnormalities in PCD are not milder than CF, particularly for those with IDA/MTD ciliary defects. New guidelines and treatments to improve outcomes in PCD are urgently needed.

Rethinking bronchiectasis as an inflammatory disease

Bronchiectasis is understood to be the result of a complex interaction between infection, impaired mucociliary clearance, inflammation, and lung damage. Current therapeutic approaches to bronchiectasis are heavily focused on management of infection along with enhancing mucus clearance. Long-term antibiotics have had limited success in clinical trials, suggesting a need to re-evaluate the concept of bronchiectasis as an infective disorder. We invoke the example of asthma, for which treatment paradigms shifted away from targeting smooth muscle constriction, towards permanently suppressing airway inflammation, reducing risk and ultimately inducing remission with precision anti-inflammatory treatments. In this Review, we argue that bronchiectasis is primarily a chronic inflammatory disease, requiring early identification of at-risk individuals, and we introduce a novel concept of disease activity with important implications for clinical practice and future research. A new generation of novel anti-inflammatory treatments are under development and repurposing of anti-inflammatory agents from other diseases could revolutionise patient care.

Dysregulated Airway Host Defense in Hyper IgE Syndrome due to STAT3 Mutations

Rationale

Hyper IgE syndrome (STAT3-HIES), also known as Job's syndrome, is a rare immunodeficiency disease typically caused by dominant-negative STAT3 mutations. STAT3-HIES syndrome is characterized by chronic pulmonary infection and inflammation, suggesting impairment of pulmonary innate host defense.

Objectives

To identify airway epithelial host defense defects consequent to STAT3 mutations that, in addition to reported mutant STAT3 immunologic abnormalities, produce pulmonary infection.

Methods

STAT3-HIES sputum was evaluated for biochemical/biophysical properties. STAT3-HIES excised lungs were harvested for histology; bronchial brush samples were collected for RNA sequencing and in vitro culture. A STAT3-HIES-specific mutation (R382W), expressed by lentiviruses, and a STAT3 knockout, generated by CRISPR/Cas9, were maintained in normal human bronchial epithelia under basal or inflammatory (IL1β) conditions. Effects of STAT3 deficiency on transcriptomics, and epithelial ion channel, secretory, antimicrobial, and ciliary functions were assessed.

Measurements and Main Results

Mucus concentrations and viscoelasticity were increased in STAT3-HIES sputum. STAT3-HIES excised lungs exhibited mucus obstruction and elevated IL1β expression. STAT3 deficiency impaired CFTR-dependent fluid and mucin secretion, inhibited expression of antimicrobial peptides, cytokines, and chemokines, and acidified airway surface liquid at baseline and post-IL1β exposure in vitro. Notably, mutant STAT3 suppressed IL1R1 expression. STAT3 mutations also inhibited ciliogenesis in vivo and impaired mucociliary transport in vitro, a process mediated via HES6 suppression. Administration of a γ-secretase inhibitor increased HES6 expression and improved ciliogenesis in STAT3 R382W mutant cells.

Conclusions

STAT3 dysfunction leads to multi-component defects in airway epithelial innate defense, which, in conjunction with STAT3-HIES immune deficiency, contributes to chronic pulmonary infection.

Genetics of chronic respiratory disease

Chronic respiratory diseases, such as chronic obstructive pulmonary disease (COPD), asthma and interstitial lung diseases are frequently occurring disorders with a polygenic basis that account for a large global burden of morbidity and mortality. Recent large-scale genetic epidemiology studies have identified associations between genetic variation and individual respiratory diseases and linked specific genetic variants to quantitative traits related to lung function. These associations have improved our understanding of the genetic basis and mechanisms underlying common lung diseases. Moreover, examining the overlap between genetic associations of different respiratory conditions, along with evidence for gene-environment interactions, has yielded additional biological insights into affected molecular pathways. This genetic information could inform the assessment of respiratory disease risk and contribute to stratified treatment approaches.

Development of allergic bronchopulmonary aspergillosis in a patient with nontuberculous mycobacterial-pulmonary disease successfully treated with dupilumab: A case report and literature review

Pulmonary manifestations in patients with allergic bronchopulmonary aspergillosis (ABPA) and nontuberculous mycobacterial-pulmonary disease (NTM-PD) include bronchiectasis and mucus plugging. A 68-year-old woman, treated with antibiotics and inhaled corticosteroids for NTM-PD and asthma, presented with fever and wheezing. ABPA was diagnosed based on laboratory findings (elevated peripheral blood eosinophil counts and serum total IgE levels and positive Aspergillus-specific IgE and IgG) and imaging observation of a high-attenuation mucus plug. Systemic prednisolone was avoided to prevent NTM-PD progression. Dupilumab, a monoclonal antibody that blocks IL-4/13, was introduced to improve the clinical findings. Herein, we discuss the pathophysiological mechanisms underlying this rare comorbidity.

Pathophysiology and genomics of bronchiectasis

Bronchiectasis is a complex and heterogeneous inflammatory chronic respiratory disease with an unknown cause in around 30-40% of patients. The presence of airway infection together with chronic inflammation, airway mucociliary dysfunction and lung damage are key components of the vicious vortex model that better describes its pathophysiology. Although bronchiectasis research has significantly increased over the past years and different endotypes have been identified, there are still major gaps in the understanding of the pathophysiology. Genomic approaches may help to identify new endotypes, as has been shown in other chronic airway diseases, such as COPD.Different studies have started to work in this direction, and significant contributions to the understanding of the microbiome and proteome diversity have been made in bronchiectasis in recent years. However, the systematic application of omics approaches to identify new molecular insights into the pathophysiology of bronchiectasis (endotypes) is still limited compared with other respiratory diseases.Given the complexity and diversity of these technologies, this review describes the key components of the pathophysiology of bronchiectasis and how genomics can be applied to increase our knowledge, including the study of new techniques such as proteomics, metabolomics and epigenomics. Furthermore, we propose that the novel concept of trained innate immunity, which is driven by microbiome exposures leading to epigenetic modifications, can complement our current understanding of the vicious vortex. Finally, we discuss the challenges, opportunities and implications of genomics application in clinical practice for better patient stratification into new therapies.