Bacteria in sputum of stable severe asthma and increased airway wall thickness

Identification and validation of three potential biomarkers and immune microenvironment for in severe asthma in microarray and single-cell datasets

Objective: The aim of this study was to identify genetic biomarkers and cellular communications associated with severe asthma in microarray data sets and single cell data sets. The potential gene expression levels were verified in a mouse model of asthma.Methods: We identified differentially expressed genes from the microarray datasets (GSE130499 and GSE63142) of severe asthma, and then constructed models to screen the most relevant biomarkers to severe asthma by machine learning algorithms (LASSO and SVM-RFE), with further validation of the results by GSE43696. Single-cell datasets (GSE193816 and GSE227744) were identified for potential biomarker-specific expression and intercellular communication. Finally, The expression levels of potential biomarkers were verified with a mouse model of asthma.Results: The 73 genes were differentially expressed between severe asthma and normal control. LASSO and SVM-RFE recognized three genes BCL3, DDIT4 and S100A14 as biomarkers of severe asthma and had good diagnostic effect. Among them, BCL3 transcript level was down-regulated in severe asthma, while S100A14 and DDIT4 transcript levels were up-regulated. The transcript levels of the three genes were confirmed in the mouse model. Infiltration of neutrophils and mast cells were found to be increased in severe asthma and may be associated with bronchial epithelial cells through BMP and NRG signalingConclusions: We identified three differentially expressed genes (BCL3, DDIT4 and S100A14) of diagnostic significance that may be involved in the development of severe asthma and these gene expressions could be serviced as biomarker of severe asthma and investigating the function roles could bring new insights into the underlying mechanisms.

Antimicrobial resistance of Pseudomonas aeruginosa: navigating clinical impacts, current resistance trends, and innovations in breaking therapies

Pseudomonas aeruginosa, a Gram-negative bacterium, is recognized for its adaptability and opportunistic nature. It poses a substantial challenge in clinical settings due to its complicated antibiotic resistance mechanisms, biofilm formation, and capacity for persistent infections in both animal and human hosts. Recent studies revealed a potential zoonotic transmission of P. aeruginosa between animals, the environment, and human populations which highlights awareness of this microbe. Implementation of the One Health approach, which underscores the connection between human, animal, and environmental health, we aim to offer a comprehensive perspective on the current landscape of P. aeruginosa management. This review presents innovative strategies designed to counteract P. aeruginosa infections. Traditional antibiotics, while effective in many cases, are increasingly compromised by the development of multidrug-resistant strains. Non-antibiotic avenues, such as quorum sensing inhibition, phage therapy, and nanoparticle-based treatments, are emerging as promising alternatives. However, their clinical application encounters obstacles like cost, side effects, and safety concerns. Effectively addressing P. aeruginosa infections necessitates persistent research efforts, advancements in clinical development, and a comprehension of host-pathogen interactions to deal with this resilient pathogen.

An integrated metabo-lipidomics profile of induced sputum for the identification of novel biomarkers in the differential diagnosis of asthma and COPD

BACKGROUND

Due to their complexity and to the presence of common clinical features, differentiation between asthma and chronic obstructive pulmonary disease (COPD) can be a challenging task, complicated in such cases also by asthma-COPD overlap syndrome. The distinct immune/inflammatory and structural substrates of COPD and asthma are responsible for significant differences in the responses to standard pharmacologic treatments. Therefore, an accurate diagnosis is of central relevance to assure the appropriate therapeutic intervention in order to achieve safe and effective patient care. Induced sputum (IS) accurately mirrors inflammation in the airways, providing a more direct picture of lung cell metabolism in comparison to those specimen that reflect analytes in the systemic circulation.

METHODS

An integrated untargeted metabolomics and lipidomics analysis was performed in IS of asthmatic (n = 15) and COPD (n = 22) patients based on Ultra-High-Pressure Liquid Chromatography-Mass Spectrometry (UHPLC-MS) and UHPLC-tandem MS (UHPLC-MS/MS). Partial Least Squares-Discriminant Analysis (PLS-DA) was applied to resulting dataset. The analysis of main enriched metabolic pathways and the association of the preliminary metabolites/lipids pattern identified to clinical parameters of asthma/COPD differentiation were explored. Multivariate ROC analysis was performed in order to determine the discriminatory power and the reliability of the putative biomarkers for diagnosis between COPD and asthma.

RESULTS

PLS-DA indicated a clear separation between COPD and asthmatic patients. Among the 15 selected candidate biomarkers based on Variable Importance in Projection scores, putrescine showed the highest score. A differential IS bio-signature of 22 metabolites and lipids was found, which showed statistically significant variations between asthma and COPD. Of these 22 compounds, 18 were decreased and 4 increased in COPD compared to asthmatic patients. The IS levels of Phosphatidylethanolamine (PE) (34:1), Phosphatidylglycerol (PG) (18:1;18:2) and spermine were significantly higher in asthmatic subjects compared to COPD.

CONCLUSIONS

This is the first pilot study to analyse the IS metabolomics/lipidomics signatures relevant in discriminating asthma vs COPD. The role of polyamines, of 6-Hydroxykynurenic acid and of D-rhamnose as well as of other important players related to the alteration of glycerophospholipid, aminoacid/biotin and energy metabolism provided the construction of a diagnostic model that, if validated on a larger prospective cohort, might be used to rapidly and accurately discriminate asthma from COPD.

The Link between Periodontal Disease and Asthma: How Do These Two Diseases Affect Each Other?

A growing body of evidence suggests that the effects of poor oral hygiene extend beyond the oral cavity and are associated with a variety of systemic diseases, including asthma. Asthma, which results in symptoms of cough, wheezing, and dyspnoea, and is characterized by airflow limitation with variability and (partial or complete) reversibility, is amongst the most prevalent respiratory diseases with approximately 262 million patients worldwide, and its prevalence and disease burden is on the increase. While asthma can occur at a young age, it can also develop later in life and affects a variety of age groups. Both of these diseases have a chronic course, and various researchers have suggested a link between the two. In this article, we aim to provide a literature review focusing on the association between the two diseases. The results demonstrate that medications (primarily, inhaler medicine), hypoxia induced by asthma, and the breathing behaviour of patients potentially trigger periodontal disease. In contrast, oral periodontopathogenic microorganisms and the inflammatory mediators produced by them may be involved in the onset and/or exacerbation of asthma. Common contributing factors, such as smoking, gastro-oesophageal reflux, and type-2 inflammation, should also be considered when evaluating the relationship between the two diseases.

Redefining the Role of Bronchoscopy in the Workup of Severe Uncontrolled Asthma in the Era of Biologics: A Prospective Study

BACKGROUND

Severe uncontrolled asthma (SUA) is frequently treated with biologic therapy if a T2 phenotype is found. Bronchoscopy is not routinely recommended in these patients unless a specific indication to rule out comorbidities is present.

RESEARCH QUESTION

Is routine bronchoscopy safe and useful in phenotyping and endotyping patients with SUA before the indication of a biologic therapy?

STUDY DESIGN AND METHODS

Prospective study of consecutive patients with SUA who were referred to a specialized asthma clinic to assess the indication of a biologic therapy. Patients were clinically phenotyped as T2-allergic, T2-eosinophilic, and non-T2. All patients underwent bronchoscopy, and systematic data collection of endoscopic findings, microbiology of bronchial aspirate, and presence of eosinophils in bronchial biopsy were recorded and compared between asthma phenotypes. Cluster analysis was performed accordingly.

RESULTS

One hundred patients were recruited and classified as T2-allergic (28%), T2-eosinophilic (64%), and non-T2 (8%). On bronchoscopy, signs of gastroesophageal reflux disease were detected in 21%, vocal cord dysfunction in 5%, and tracheal abnormalities in 3%. Bronchial aspirate culture isolated bacteria in 27% of patients and fungi in 14%. Three clusters were identified: nonspecific, upper airway, and infection, the latter being less frequently associated with submucosal eosinophilia. Eosinophils were detected in 91% of bronchial biopsies. Despite a correlation to blood eosinophils, five patients with T2-phenotypes showed no eosinophils in bronchial biopsy, and three patients with non-T2 showed eosinophils in bronchial biopsy. Only one patient had moderate bleeding.

INTERPRETATION

Routine bronchoscopy in SUA eligible for biologic therapy is a safe procedure that can help to better phenotype and personalize asthma management.

Exploring the role of neutrophils in infectious and noninfectious pulmonary disorders

With the change in global environment, respiratory disorders are becoming more threatening to the health of people all over the world. These diseases are closely linked to performance of immune system. Within the innate arm of immune system, Neutrophils are an important moiety to serve as an immune defense barrier. They are one of the first cells recruited to the site of infection and plays a critical role in pathogenesis of various pulmonary diseases. It is established that the migration and activation of neutrophils can lead to inflammation either directly or indirectly and this inflammation caused is very crucial for the clearance of pathogens and resolution of infection. However, the immunopathological mechanisms involved to carry out the same is very complex and not well understood. Despite there being studies concentrating on the role of neutrophils in multiple respiratory diseases, there is still a long way to go in order to completely understand the complexity of the participation of neutrophils and mechanisms involved in the development of these respiratory diseases. In the present article, we have reviewed the literature to comprehensively provide an insight in the current development and advancements about the role of neutrophils in infectious respiratory disorders including viral respiratory disorders such as Coronavirus disease (COVID-19) and bacterial pulmonary disorders with a focused review on pulmonary tuberculosis as well as in noninfectious disorders like Chronic obstructive pulmonary disease (COPD) and asthma. Also, future directions into research and therapeutic targets have been discussed for further exploration.

Microbiome and Asthma: Microbial Dysbiosis and the Origins, Phenotypes, Persistence, and Severity of Asthma

The importance of the microbiome, and of the gut-lung axis in the origin and persistence of asthma, is an ongoing field of investigation. The process of microbial colonisation in the first three years of life is fundamental for health, with the first hundred days of life being critical. Different factors are associated with early microbial dysbiosis, such as caesarean delivery, artificial lactation and antibiotic therapy, among others. Longitudinal cohort studies on gut and airway microbiome in children have found an association between microbial dysbiosis and asthma at later ages of life. A low α-diversity and relative abundance of certain commensal gut bacterial genera in the first year of life are associated with the development of asthma. Gut microbial dysbiosis, with a lower abundance of Phylum Firmicutes, could be related with increased risk of asthma. Upper airway microbial dysbiosis, especially early colonisation by Moraxella spp., is associated with recurrent viral infections and the development of asthma. Moreover, the bacteria in the respiratory system produce metabolites that may modify the inception of asthma and is progression. The role of the lung microbiome in asthma development has yet to be fully elucidated. Nevertheless, the most consistent finding in studies on lung microbiome is the increased bacterial load and the predominance of proteobacteria, especially Haemophilus spp. and Moraxella catarrhalis. In this review we shall update the knowledge on the association between microbial dysbiosis and the origins of asthma, as well as its persistence, phenotypes, and severity.

The understanding of asthma pathogenesis in the era of precision medicine

Asthma is a syndrome with extremely diverse clinical phenotypes in which the onset, severity, and response to treatment are defined by the complex interplay of many genetic and environmental factors. Environmental factors epigenetically affect gene expression, and the disease is driven by a multidimensional dynamic network involving RNA and protein molecules derived from gene expression, as well as various metabolic products. In other words, specific pathophysiological mechanisms or endotypes are dynamic networks that arise in response to individual genotypes and the various environmental factors to which individuals have been exposed since before birth, such as diet, infection, air pollution, smoking, antibiotic use, and the bacterial flora of the intestinal tract, skin, and lungs. A key feature of asthma genome scans is their potential to reveal the molecular pathways that lead to pathogenesis. Endotypes that drive the disease have a significant impact on the phenotypes of asthma patients, including their drug responsiveness. Understanding endotypes will lead to not only the implementation of therapies that are tailored to the specific molecular network(s) underlying the patient's condition, but also to the development of therapeutic strategies that target individual endotypes, as well as to precision health, which will enable the prediction of disease onset with high accuracy from an early stage and the implementation of preventive strategies based on endotypes. Understanding of endotypes will pave the way for the practice of precision medicine in asthma care, moving away from 'one-size-fits-all' medicine and population-based prevention approaches that do not take individuals' susceptibility into account.

Bacteriophage: A new therapeutic player to combat neutrophilic inflammation in chronic airway diseases

Persistent respiratory bacterial infections are a clinical burden in several chronic inflammatory airway diseases and are often associated with neutrophil infiltration into the lungs. Following recruitment, dysregulated neutrophil effector functions such as increased granule release and formation of neutrophil extracellular traps (NETs) result in damage to airway tissue, contributing to the progression of lung disease. Bacterial pathogens are a major driver of airway neutrophilic inflammation, but traditional management of infections with antibiotic therapy is becoming less effective as rates of antimicrobial resistance rise. Bacteriophages (phages) are now frequently identified as antimicrobial alternatives for antimicrobial resistant (AMR) airway infections. Despite growing recognition of their bactericidal function, less is known about how phages influence activity of neutrophils recruited to sites of bacterial infection in the lungs. In this review, we summarize current in vitro and in vivo findings on the effects of phage therapy on neutrophils and their inflammatory mediators, as well as mechanisms of phage-neutrophil interactions. Understanding these effects provides further validation of their safe use in humans, but also identifies phages as a targeted neutrophil-modulating therapeutic for inflammatory airway conditions.

Preclinical Evaluation of Recombinant Microbial Glycoside Hydrolases as Antibiofilm Agents in Acute Pulmonary Pseudomonas aeruginosa Infection

The bacterium Pseudomonas aeruginosa can colonize the airways of patients with chronic lung disease. Within the lung, P. aeruginosa forms biofilms that can enhance resistance to antibiotics and immune defenses. P. aeruginosa biofilm formation is dependent on the secretion of matrix exopolysaccharides, including Pel and Psl. In this study, recombinant glycoside hydrolases (GHs) that degrade Pel and Psl were evaluated alone and in combination with antibiotics in a mouse model of P. aeruginosa infection. Intratracheal GH administration was well tolerated by mice. Pharmacokinetic analysis revealed that, although GHs have short half-lives, administration of two GHs in combination resulted in increased GH persistence. Combining GH prophylaxis and treatment with the antibiotic ciprofloxacin resulted in greater reduction in pulmonary bacterial burden than that with either agent alone. This study lays the foundation for further exploration of GH therapy in bacterial infections.

Non-invasive diagnostics of pathogenic bacteria using a breath sampler in children with cystic fibrosis

Cystic fibrosis is a common autosomal recessive disease causing thick, viscous secretions leading to pulmonary infections with pathogenic bacteria. As part of routine patient care, colonization and infection with these bacteria is monitored with cough swab or sputum cultures and sometimes bronchoalveolar lavage. In this cross-sectional proof-of-concept study in a cohort of CF patients we collected swabs or sputa and exhaled breath samples with the Modular Breath Sampler (MBS), a newly developed two-way non-rebreathing sampling device. Pathogen specific polymerase chain reactions (PCRs) were performed on the MBS samples and compared with the results obtained with conventional diagnostics (i.e. culturing of swabs and sputa). A control group of stable asthma patients was used as negative control for the MBS measurements. The pathogens detected using MBS and conventional culturing differed: Staphylococcus aureus was found more often in swab or sputum samples whereas Pseudomonas aeruginosa and Streptococcus pneumoniae were found more often in MBS samples. We hypothesize that this is due to sampling of different compartments, MBS samples are derived from the lower respiratory tract while cultures from cough swabs and sputa are dominated by pathogens residing in the upper respiratory tract. Another important difference is the readout, i.e. culture versus PCR. The majority of CF patients in whom Pseudomonas aeruginosa was found did not have recent positive cultures suggesting higher sensitivity of MBS-based than conventional diagnostics. The majority of parents / patients found the MBS easy to use and less of a burden than respiratory sampling.

Clinical and cytokine patterns of uncontrolled asthma with and without comorbid chronic rhinosinusitis: a cross-sectional study

Background

Asthma is significantly related to chronic rhinosinusitis (CRS) both in prevalence and severity. However, the clinical patterns of uncontrolled asthma with and without comorbid CRS are still unclear. This study aimed to explore the clinical characteristics and cytokine patterns of patients with uncontrolled asthma, with and without comorbid CRS.

Methods

22 parameters associated with demographic characteristics, CRS comorbidity, severity of airflow obstruction and airway inflammation, and inflammation type of asthma were collected and assessed in 143 patients with uncontrolled asthma. Different clusters were explored using two-step cluster analysis. Sputum samples were collected for assessment of Th1/Th2/Th17 and epithelium-derived cytokines.

Results

Comorbid CRS was identified as the most important variable for prediction of different clusters, followed by pulmonary function parameters and blood eosinophil level. Three clusters of patients were determined: Cluster 1 (n = 46) characterized by non-atopic patients with non-eosinophilic asthma without CRS, demonstrating moderate airflow limitation; Cluster 2 (n = 54) characterized by asthma patients with mild airflow limitation and CRS, demonstrating higher levels of blood eosinophils and immunoglobulin E (IgE) than cluster 1; Cluster 3 (n = 43) characterized by eosinophilic asthma patients with severe airflow limitation and CRS (46.5% with nasal polyps), demonstrating worst lung function, lowest partial pressure of oxygen (PaO₂), and highest levels of eosinophils, fraction of exhaled nitric oxide (FeNO) and IgE. Sputum samples from Cluster 3 showed significantly higher levels of Interleukin (IL)-5, IL-13, IL-33, and tumor necrosis factor (TNF)-α than the other two clusters; and remarkably elevated IL-4, IL-17 and interferon (IFN)-γ compared with cluster 2. The levels of IL-10 and IL-25 were not significantly different among the three clusters.

Conclusions

Uncontrolled asthma may be endotyped into three clusters characterized by CRS comorbidity and inflammatory cytokine patterns. Furthermore, a united-airways approach may be especially necessary for management of asthma patients with Type 2 features.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02028-3.

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

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

Oncostatin M expression induced by bacterial triggers drives airway inflammatory and mucus secretion in severe asthma

[Figure: see text].

Corticosteroid insensitivity persists in the absence of STAT1 signaling in severe allergic airway inflammation

Corticosteroid insensitivity in asthma limits the ability to effectively manage severe asthma, which is characterized by persistent airway inflammation, airway hyperresponsiveness (AHR), and airflow obstruction despite corticosteroid treatment. Recent reports indicate that corticosteroid insensitivity is associated with increased interferon-γ (IFN-γ) levels and T-helper (Th) 1 lymphocyte infiltration in severe asthma. Signal transducer and activator of transcription 1 (STAT1) activation by IFN-γ is a key signaling pathway in Th1 inflammation; however, its role in the context of severe allergic airway inflammation and corticosteroid sensitivity remains unclear. In this study, we challenged wild-type (WT) and Stat1^-/- mice with mixed allergens (MA) augmented with c-di-GMP [bis-(3'-5')-cyclic dimeric guanosine monophosphate], an inducer of Th1 cell infiltration with increased eosinophils, neutrophils, Th1, Th2, and Th17 cells. Compared with WT mice, Stat1^-/- had reduced neutrophils, Th1, and Th17 cell infiltration. To evaluate corticosteroid sensitivity, mice were treated with either vehicle, 1 or 3 mg/kg fluticasone propionate (FP). Corticosteroids significantly reduced eosinophil infiltration and cytokine levels in both c-di-GMP + MA-challenged WT and Stat1^-/- mice. However, histological and functional analyses show that corticosteroids did not reduce airway inflammation, epithelial mucous cell abundance, airway smooth muscle mass, and AHR in c-di-GMP + MA-challenged WT or Stat1^-/- mice. Collectively, our data suggest that increased Th1 inflammation is associated with a decrease in corticosteroid sensitivity. However, increased airway pathology and AHR persist in the absence of STAT1 indicate corticosteroid insensitivity in structural airway cells is a STAT1 independent process.

Antibacterial Resistance Pattern in Clinical and Non-clinical Bacteria by Phenotypic and Genotypic Assessment

Bacterial infections represent a very serious problem that threatens human health, antibiotics were designed to attack the causative agents of infectious diseases, but some bacterial pathogens became virulent and resistant to antibiotics by different mechanisms, resistance genes represented one of those mechanisms. This study attempts to screen the existence of five different resistance genes (mecA, TEM, FemA, MexD, and AmpC) among 25 bacterial isolates divided into two groups the first was non-clinical bacterial type strains including Bacillus subtilis, Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa, Salmonella typhi, and the other group includes some clinical bacterial isolates. Evaluation of their susceptibilities to different 12 antibiotic discs and attempting to find the relationship between genotype and phenotype assessment. Different responses were reported which varied from slightly susceptible to multidrug-resistant such as P. aeruginosa and K. pneumonia which could be considered as multidrug-resistant strains. Therefore, detection of resistance gene became crucial and critical to recognize the mechanism of resistance, five pairs of primers were included to investigate five responsible genes belonging to beta-lactamases, efflux pump, and methicillin resistance. Conclusively, the PCR technique is a very accurate tool to check the genetic resistance whether being expressed to phenotype or not. Moreover, the clinical bacterial isolates appeared more resistant that reflecting the impact of the surrounding environment on bacterial behavior.

The Role of CD4+ T Cells and Microbiota in the Pathogenesis of Asthma

Asthma, a chronic respiratory disease involving variable airflow limitations, exhibits two phenotypes: eosinophilic and neutrophilic. The asthma phenotype must be considered because the prognosis and drug responsiveness of eosinophilic and neutrophilic asthma differ. CD4+ T cells are the main determinant of asthma phenotype. Th2, Th9 and Tfh cells mediate the development of eosinophilic asthma, whereas Th1 and Th17 cells mediate the development of neutrophilic asthma. Elucidating the biological roles of CD4+ T cells is thus essential for developing effective asthma treatments and predicting a patient's prognosis. Commensal bacteria also play a key role in the pathogenesis of asthma. Beneficial bacteria within the host act to suppress asthma, whereas harmful bacteria exacerbate asthma. Recent literature indicates that imbalances between beneficial and harmful bacteria affect the differentiation of CD4+ T cells, leading to the development of asthma. Correcting bacterial imbalances using probiotics reportedly improves asthma symptoms. In this review, we investigate the effects of crosstalk between the microbiota and CD4+ T cells on the development of asthma.

Emerging cellular and molecular interactions between the lung microbiota and lung diseases

With the discovery of the lung microbiota, its study in both pulmonary health and disease has become a vibrant area of emerging research interest. Thus far, most studies have described the lung microbiota composition in lung disease quite well, and some of these studies indicated alterations in lung microbial communities related to the onset and development of lung disease and vice versa. However, the underlying mechanisms, particularly the cellular and molecular links, are still largely unknown. In this review, we highlight the current progress in the complex cellular and molecular mechanisms by which the lung microbiome interacts with immune homeostasis and pulmonary disease pathogenesis to advance our understanding of the elaborate function of the lung microbiota in lung disease. We hope that this work can attract more attention to this still-young yet very promising field to facilitate the identification of new therapeutic targets and provide more innovative therapies. Additional accurate standard-based methodologies and technological breakthroughs are critical to propel the field forward to ultimately achieve the goal of maintaining respiratory health.

The Relationship Between Lower Respiratory Tract Microbiome and Allergic Respiratory Tract Diseases in Children

Similar to those in the upper respiratory tract, there are microbes present in the healthy human lower respiratory tract (LRT), including the lungs and bronchus. To evaluate the relationship between LRT microbiome and allergic respiratory diseases in children, we enrolled 68 children who underwent bronchoscopy from January 2018 to December 2018 in the affiliated hospital of the Capital Institute of Pediatrics. Using the total IgE (TIgE) values, children were divided into two groups: allergy sensitivity (AS) group and non-allergy sensitivity (NAS) group. Nucleic acid was extracted from samples of bronchoalveolar lavage fluid (BALF) from the two groups of children taken during bronchoscopy treatment and the 16S rDNA gene was sequenced and analyzed. The results showed that Haemophilus, Moraxella, Streptococcus, Prevotella, Neisseria, and Rothia were detected in all patients. There was a statistically significant difference in the composition and distribution of microbiota between the AS and NAS groups (p < 0.01). Analysis of the correlation of clinical indices and microbiome showed that TIgE was positively correlated with Bacteroidetes and negatively correlated with Streptococcus. Absolute lymphocyte count showed a relationship with Streptococcus, and the absolute neutrophil count or percentage of neutrophils showed a relationship with Cardiobacterium. The LRT microbiome functioned similarly to the intestinal microbiome. That is, the decrease in microbial diversity and the change in composition could lead to an increase in allergic symptoms. The microbiome of the LRT in children, especially that of Bacteriodetes and Streptococcus, showed a correlation with respiratory allergic diseases.

The Action of Shenmai Injection on the Inflammation and Proliferation of Smooth Muscle Cells of the Airway in Asthmatic Rats

To observe the effect of transient receptor potential ankyrin 1 (TRPA1) channel on the proliferation and inflammation of airway smooth muscle cells (SMC) in asthmatic rats, the rats were randomly allocated into three treatment groups: control, asthma, and Shenmai injection (SMI), with 15 rats in each group. Asthmatic rat models were induced by ovalbumin (OVA) inhalation. Rats in the control and asthma groups were intraperitoneally injected 2 mL NS daily, whereas rats in the SMI treatment group were intraperitoneally injected with 2 mL SMI daily. RT-qPCR and western blotting were used to test for TRPA1 and proliferating cell nuclear antigen (PCNA) mRNA and protein expression. ELISA was used to test the expression of interleukin-4 (IL-4), interleukin-5 (IL-5), and interleukin-13 (IL-13) in the serum. Compared with the control group, there were significantly higher levels of TRPA1 and PCNA mRNA and protein, as well as of IL-4, IL-5, and IL-13 in asthmatic rats (P< 0.05). After SMI treatment, there was significantly lower expression of TRPA1, PCNA, IL-4, IL-5, and IL-13 compared to the levels in asthmatic rats (P < 0.05). TRPA1, IL-4, IL-5, and IL-13 were highly expressed in the tracheal SMC of asthmatic rats. Inhibiting TRPA1, IL-4, IL-5, and IL-13 using SMI may be one of the mechanisms that can intervene chronic airway inflammation and asthma proliferation.

Cyclic-di-GMP Induces STING-Dependent ILC2 to ILC1 Shift During Innate Type 2 Lung Inflammation

Type 2 inflammation is found in most forms of asthma, which may co-exist with recurrent viral infections, bacterial colonization, and host cell death. These processes drive the accumulation of intracellular cyclic-di-nucleotides such as cyclic-di-GMP (CDG). Group 2 innate lymphoid cells (ILC2s) are critical drivers of type 2 lung inflammation during fungal allergen exposure in mice; however, it is unclear how CDG regulates lung ILC responses during lung inflammation. Here, we show that intranasal CDG induced early airway type 1 interferon (IFN) production and dramatically suppressed CD127+ST2+ ILC2s and type 2 lung inflammation during Alternaria and IL-33 exposure. Further, CD127-ST2-Thy1.2+ lung ILCs, which showed a transcriptomic signature consistent with ILC1s, were expanded and activated by CDG combined with either Alternaria or IL-33. CDG-mediated suppression of type 2 inflammation occurred independent of IL-18R, IL-12, and STAT6 but required the stimulator of interferon genes (STING) and type 1 IFN signaling. Thus, CDG potently suppresses ILC2-driven lung inflammation and promotes ILC1 responses. These results suggest potential therapeutic modulation of STING to suppress type 2 inflammation and/or increase anti-viral responses during respiratory infections.

Interactions of Bacteriophages and Bacteria at the Airway Mucosa: New Insights Into the Pathophysiology of Asthma

The airway epithelium is the primary site where inhaled and resident microbiota interacts between themselves and the host, potentially playing an important role on allergic asthma development and pathophysiology. With the advent of culture independent molecular techniques and high throughput technologies, the complex composition and diversity of bacterial communities of the airways has been well-documented and the notion of the lungs' sterility definitively rejected. Recent studies indicate that the microbial composition of the asthmatic airways across the spectrum of disease severity, differ significantly compared with healthy individuals. In parallel, a growing body of evidence suggests that bacterial viruses (bacteriophages or simply phages), regulating bacterial populations, are present in almost every niche of the human body and can also interact directly with the eukaryotic cells. The triptych of airway epithelial cells, bacterial symbionts and resident phages should be considered as a functional and interdependent unit with direct implications on the respiratory and overall homeostasis. While the role of epithelial cells in asthma pathophysiology is well-established, the tripartite interactions between epithelial cells, bacteria and phages should be scrutinized, both to better understand asthma as a system disorder and to explore potential interventions.

Impact of Pseudomonas aeruginosa Infection on Patients with Chronic Inflammatory Airway Diseases

Pseudomonas aeruginosa (P. aeruginosa) is a ubiquitous and opportunistic microorganism and is considered one of the most significant pathogens that produce chronic colonization and infection of the lower respiratory tract, especially in people with chronic inflammatory airway diseases such as asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), and bronchiectasis. From a microbiological viewpoint, the presence and persistence of P. aeruginosa over time are characterized by adaptation within the host that precludes any rapid, devastating injury to the host. Moreover, this microorganism usually develops antibiotic resistance, which is accelerated in chronic infections especially in those situations where the frequent use of antimicrobials facilitates the selection of “hypermutator P. aeruginosa strain”. This phenomenon has been observed in people with bronchiectasis, CF, and the “exacerbator” COPD phenotype. From a clinical point of view, a chronic bronchial infection of P. aeruginosa has been related to more severity and poor prognosis in people with CF, bronchiectasis, and probably in COPD, but little is known on the effect of this microorganism infection in people with asthma. The relationship between the impact and treatment of P. aeruginosa infection in people with airway diseases emerges as an important future challenge and it is the most important objective of this review.

Interaction of Staphylococcus aureus and Host Cells upon Infection of Bronchial Epithelium during Different Stages of Regeneration

The primary barrier that protects our lungs against infection by pathogens is a tightly sealed layer of epithelial cells. When the integrity of this barrier is disrupted as a consequence of chronic pulmonary diseases or viral insults, bacterial pathogens will gain access to underlying tissues. A major pathogen that can take advantage of such conditions is Staphylococcus aureus, thereby causing severe pneumonia. In this study, we investigated how S. aureus responds to different conditions of the human epithelium, especially nonpolarization and fibrogenesis during regeneration using an in vitro infection model. The infective process was monitored by quantification of the epithelial cell and bacterial populations, fluorescence microscopy, and mass spectrometry. The results uncover differences in bacterial internalization and population dynamics that correlate with the outcome of infection. Protein profiling reveals that, irrespective of the polarization state of the epithelial cells, the invading bacteria mount similar responses to adapt to the intracellular milieu. Remarkably, a bacterial adaptation that was associated with the regeneration state of the epithelial cells concerned the early upregulation of proteins controlled by the redox-responsive regulator Rex when bacteria were confronted with a polarized cell layer. This is indicative of the modulation of the bacterial cytoplasmic redox state to maintain homeostasis early during infection even before internalization. Our present observations provide a deeper insight into how S. aureus can take advantage of a breached epithelial barrier and show that infected epithelial cells have limited ability to respond adequately to staphylococcal insults.

The Interactions of Airway Bacterial and Fungal Communities in Clinically Stable Asthma

Dysbiotic airway microbiota play important roles in the inflammatory progression of asthma, and exploration of airway microbial interactions further elucidates asthma pathogenesis. However, little is known regarding the airway bacterial-fungal interactions in asthma patients. We conducted a cross-sectional survey of the sputum bacterial and fungal microbiota from 116 clinically stable asthma patients and 29 healthy controls using 16S rRNA gene and ITS1 sequencing. Compared with healthy individuals, asthma patients exhibited a significantly altered microbiota and increased bacterial and fungal alpha diversities in the airway. Microbial genera Moraxella, Capnocytophaga, and Ralstonia (bacteria) and Schizophyllum, Candida, and Phialemoniopsis (fungi) were more abundant in the asthma airways, while Rothia, Veillonella and Leptotrichia (bacteria) and Meyerozyma (fungus) were increased in healthy controls. The Moraxellaceae family and their genus Moraxella were significantly enriched in asthma patients compared with healthy controls (80.5-fold, P = 0.007 and 314.7-fold, P = 0.027, respectively). Moreover, Moraxellaceae, along with Schizophyllum, Candida, and Aspergillus (fungal genera), were positively associated with fungal alpha diversity. Correlation networks revealed 3 fungal genera (Schizophyllum, Candida, and Aspergillus) as important airway microbes in asthma that showed positive correlations with each other and multiple co-exclusions with other common microbiota. Moraxellaceae members were positively associated with asthma-enriched fungal taxa but negatively related to several healthy-enriched bacterial taxa. Collectively, our findings revealed an altered microbiota and complex microbial interactions in the airways of asthma patients. The Moraxellaceae family and their genus Moraxella, along with 3 important fungal taxa, showed significant interactions with the airway microbiota, providing potential insights into the novel pathogenic mechanisms of asthma.

The Link between Asthma and Bronchiectasis: State of the Art

The nonrecognition of asthma-associated comorbidities is often responsible for the therapeutic failure and the worsening of symptoms, and it is associated with frequent exacerbations, higher disease severity, and increased health costs. Bronchiectasis, one of the most frequent asthma-associated comorbidities, can increase airways inflammation and exacerbation rates and cause respiratory functional impairment. The aim of this article is to review the interactions between bronchiectasis and asthma, in order to better identify patients in the overlap between the 2 diseases and to select an "ad hoc" therapy. A literature search on PubMed/MEDLINE was performed using the following search terms: bronchiectasis in asthma, the association between asthma and bronchiectasis, comorbidities in asthma, and severe asthma. This review analyzed the following items: incorrect or underestimated diagnosis of asthma and bronchiectasis, prevalence of bronchiectasis in asthma, the impact of bronchiectasis in asthma, radiological imaging features of the 2 diseases, etiopathogenesis, and common causes (such as gastroesophageal reflux disease, immune deficits, chronic rhinosinusitis and allergic bronchopulmonary aspergillosis, and treatment of asthma and bronchiectasis). The concomitant presence of bronchiectasis and asthma should be suspected and investigated in patients with severe asthma, frequent exacerbations, and not responding to standard therapy. This clinical phenotype, characterized by a more severe disease, worse outcomes, and functional decline, must be readily recognized in order to choose the most appropriate therapeutic approach, able to potentially improve the management of bronchial asthma, to prevent the onset of exacerbations as well the functional decline, and to reduce health costs.

Anti-asthmatic effects of lepidii seu Descurainiae Semen plant species in ovalbumin-induced asthmatic mice

ETHNOPHARMACOLOGICAL EVIDENCE

Lepidii seu Descurainiae Semen (LDS) is used as a traditional herbal medicine in northeast Asia, mainly in Korea, Japan, and China to treat lung disorders including coughs and phlegm caused by acute and chronic airway inflammation.

AIM OF THE STUDY

Recently, interest regarding health problems incurred by air pollution has rapidly grown. Herbal medicines are being considered as alternative agents to treat various diseases. In the present study, we evaluated and compared the anti-inflammatory effects of LDS, which is derived from Lepidium apetalum Willd. extracts (LAE) and Descurainia sophia (L.) Webb ex Prantl extracts (DSE), on allergic airway inflammation.

MATERIALS AND METHODS

We established an ovalbumin-induced asthmatic mouse model to evaluate the efficacy of LDS extracts. We performed histological examination and measured relevant inflammatory mediators and cells in bronchoalveolar lavage fluid and lung. Furthermore, we conducted an in vitro T helper 2 (Th2) polarization assay, flow cytometry, and western blot analysis.

RESULTS

Asthmatic phenotypes were attenuated by LDS extract treatments. LDS extract administration significantly reduced mucus production, inflammatory cell infiltration into airways, and eosinophil activation. Furthermore, LDS extracts reduced the expression of type 2 cytokines and inhibited differentiation and activation of Th2 cells.

CONCLUSION

LDS alleviated eosinophilic inflammation by inhibiting Th2 cell differentiation, and DSE was more effective in attenuating allergic lung inflammation than LAE.

Cromolyn, a New Hope for Limited Treatment of Neutrophilic Asthma: a Phase II Randomized Clinical Trial

BACKGROUND

In this study, we aimed to determine the effects of cromolyn on the clinical outcomes and neutrophilic inflammation in patients with resistant cough-variant asthma.

MATERIALS AND METHODS

Patients with cough-variant asthma, with normal physical examination and spirometry results, were treated by inhaled corticosteroids, antileukotrienes, antibiotics, and proton-pump inhibitors according to the Global Initiative for Asthma (GINA) guidelines. Seventy patients, who were resistant to these treatments, were enrolled in this double-blind randomized clinical trial. After randomization, eligible subjects received a cromolyn metered dose inhaler (MDI) or a placebo MDI, which was completely similar in appearance to the cromolyn inhaler. The primary outcomes included cough and Asthma Control Test (ACT) score.

RESULTS

Based on the findings, cough significantly decreased with cromolyn therapy, compared to the placebo group. Other clinical findings, including dyspnea, sputum production, and nocturnal symptoms, also improved. The ACT score significantly improved to a nearly normal level (23.53±2.25) in the cromolyn group. Moreover, fractional exhaled nitric oxide (FeNO) significantly decreased with cromolyn treatment (14±9.31 ppm after treatment vs. 28.88±27.39 before treatment). The neutrophil count significantly decreased in the cromolyn group (from 44±24.2% before the trial to 34.08±16.7% after the trial), while it increased in the placebo group (from 39.67±26.47% to 56.71±27.22%).

CONCLUSION

Cromolyn improved the clinical findings of resistant cough-variant asthma and could suppress neutrophilic inflammation.

Elevated serum Activin A in chronic obstructive pulmonary disease with skeletal muscle wasting

OBJECTIVE

Muscle wasting contributes to the reduced quality of life and increased mortality in chronic obstructive pulmonary disease (COPD). Muscle atrophy in mice with cachexia was caused by Activin A binding to ActRIIB. The role of circulating Activin A leading to muscle atrophy in COPD remains elusive.

METHODS

In the present study, we evaluated the relationship between serum levels of Activin A and skeletal muscle wasting in COPD patients. The expression levels of serum Activin A were measured in 78 stable COPD patients and in 60 healthy controls via ELISA, which was also used to determine the expression of circulating TNF-α levels. Total skeletal muscle mass (SMM) was calculated according to a validated formula by age and anthropometric measurements. The fat-free mass index (FFMI) was determined as the fat-free mass (FFM) corrected for body surface area.

RESULTS

Compared to the healthy controls, COPD patients had upregulated Activin A expression. The elevated levels of Activin A were correlated with TNF-α expression, while total SMM and FFMI were significantly decreased in COPD patients. Furthermore, serum Activin A expression in COPD patients was negatively associated with both FFMI and BMI.

CONCLUSION

The above results showed an association between increased circulating Activin A in COPD patients and the presence of muscle atrophy. Given our previous knowledge, we speculate that Activin A contributes to skeletal muscle wasting in COPD.

Potential Role of the Lung Microbiome in Shaping Asthma Phenotypes

The introduction of 16s ribosomal RNA sequencing as a nonculture technique has led to the discovery of the presence of microbiota in the lower airways of healthy individuals. These bacterial communities may originate from the mouth and nasopharynx or from the environment by inhalation. The microbial composition of the lower airways may be modulated by dietary factors, antibiotic therapy, and microbial infections, particularly in early life. In addition, circulatory products from gut microbiota may influence the lung microbiota to maintain mucosal immunity. Recent studies have revealed that, in asthma, the lower airway microbiota show reduced diversity and community composition that is linked to severity and inflammatory phenotype. There is also a greater prevalence of proteobacteria, including Haemophilus, in symptomatic asthma. Microbial dysbiosis may contribute to both the inception and progression of asthma in infants and children, and to corticosteroid resistance in asthma. A better understanding of the regulation of the lung and gut microbiota in asthma may pave the way for targeting microbiota to prevent and treat asthma.

Clinical approaches towards asthma and chronic obstructive pulmonary disease based on the heterogeneity of disease pathogenesis

Asthma and chronic obstructive pulmonary disease (COPD) are each heterogeneous disease classifications that include several clinical and pathophysiological phenotypes. This heterogeneity complicates characterization of each disease and, in some cases, hinders the selection of appropriate treatment. Therefore, in recent years, emphasis has been placed on improving our understanding of the various phenotypes of asthma and of COPD and identifying biomarkers for each phenotype. Likewise, the concept of the endotype has been gaining acceptance; an endotype is a disease subtype that is defined by unique or distinctive functional or pathophysiological mechanisms. Endotypes of asthma or COPD may be primarily characterized by increased susceptibility to type 2 inflammation, increased susceptibility to viral infections, bacterial colonization or impaired lung development. The 'Dutch hypothesis' is as follows: gene variants underlying particular endotypes interact with detrimental environmental stimuli (e.g. smoking, viral infection and air pollution) and contribute to the ultimate development of asthma, COPD or both. Novel approaches that involve multidimensional assessment should facilitate identification and management of the components that generate this heterogeneity. Ultimately, patients with chronic inflammatory lung diseases may be treated based on these endotypes as determined by the respective biomarkers that correspond to individual endotypes instead of on disease labels such as asthma, COPD or even asthma-COPD overlap syndrome (ACOS).

Pathogenic CD4+ T cells in patients with asthma

Asthma encompasses a variety of clinical phenotypes that involve distinct T cell-driven inflammatory processes. Improved understanding of human T-cell biology and the influence of innate cytokines on T-cell responses at the epithelial barrier has led to new asthma paradigms. This review captures recent knowledge on pathogenic CD4+ T cells in asthmatic patients by drawing on observations in mouse models and human disease. In patients with allergic asthma, TH2 cells promote IgE-mediated sensitization, airway hyperreactivity, and eosinophilia. Here we discuss recent discoveries in the myriad molecular pathways that govern the induction of TH2 differentiation and the critical role of GATA-3 in this process. We elaborate on how cross-talk between epithelial cells, dendritic cells, and innate lymphoid cells translates to T-cell outcomes, with an emphasis on the actions of thymic stromal lymphopoietin, IL-25, and IL-33 at the epithelial barrier. New concepts on how T-cell skewing and epitope specificity are shaped by multiple environmental cues integrated by dendritic cell "hubs" are discussed. We also describe advances in understanding the origins of atypical TH2 cells in asthmatic patients, the role of TH1 cells and other non-TH2 types in asthmatic patients, and the features of T-cell pathogenicity at the single-cell level. Progress in technologies that enable highly multiplexed profiling of markers within a single cell promise to overcome barriers to T-cell discovery in human asthmatic patients that could transform our understanding of disease. These developments, along with novel T cell-based therapies, position us to expand the assortment of molecular targets that could facilitate personalized treatments.

Neutrophilic Inflammation in Asthma and Association with Disease Severity

Asthma is a chronic inflammatory disorder of the airways. While the local infiltration of eosinophils and mast cells, and their role in the disease have long been recognized, neutrophil infiltration has also been assessed in many clinical studies. In these studies, airway neutrophilia was associated with asthma severity. Importantly, neutrophilia also correlates with asthma that is refractory to corticosteroids, the mainstay of asthma treatment. However, it is now increasingly recognized that neutrophils are a heterogeneous population, and a more precise phenotyping of these cells may help delineate different subtypes of asthma. Here, we review current knowledge of the role of neutrophils in asthma and highlight future avenues of research in this field.

Phenotype-Driven Therapeutics in Severe Asthma

Inhaled corticosteroids are the mainstay of asthma treatment using a step-up approach with incremental dosing and additional controller medications in order to achieve symptom control and prevent exacerbations. While most patients respond well to this treatment approach, some patients remain refractory despite high doses of inhaled corticosteroids and a long-acting β-agonist. The problem lies in the heterogeneity of severe asthma, which is further supported by the emergence of severe asthma phenotypes. This heterogeneity contributes to the variability in treatment response. Randomized controlled trials involving add-on therapies in poorly controlled asthma have challenged the idea of a "one size fits all" approach targeting specific phenotypes in their subject selection. This review discusses severe asthma phenotypes from unbiased clustering approaches and the most recent scientific evidence on novel treatments to provide a guide in personalizing severe asthma treatment.

Investigation of bronchiectasis in severe uncontrolled asthma

INTRODUCTION

The presence of bronchiectasis in patients with asthma varies in different reports, while a clear aetiological relation has not been precisely established.

OBJECTIVES

To investigate the presence of bronchiectasis in patients with severe uncontrolled asthma and examine whether they contribute to the severity of asthma.

METHODS

Patients with severe asthma were prospectively recruited. HRCT of the chest was performed to identify and grade bronchiectasis using the 'Smith' radiology scale. Investigation of the underlying cause was carried out for patients with bronchiectasis in order to exclude aetiologies other than asthma. The Statistical Package for the Social Sciences (SPSS), version 21, was used.

RESULTS

Forty patients were studied, 28 women, mean age (±SD) 57.9 years (±12.4). Mean ACT score was 14.2(±4.9). Main symptoms were: wheezing (95%), cough (92%), dysponea (92%) and sputum production (72%). Mean duration of asthma was 16.5(±11.5) years, exacerbations: 4.4(±2.7)/year. In 27 patients (67.5%) bronchiectasis was diagnosed. In nine patients (22.5%) pathogens were cultured in sputum (mainly Pseudomonas aeruginosa, Haemophilus influenzae). Patients with sputum production and pathogens in sputum cultures had a higher Smith score compared to those without expectoration and without pathogens, respectively (P = .005, P < .0001). No correlation was found between the extent of bronchiectasis and lung function. The radiological severity of bronchiectasis was correlated with the antibiotic courses/year (P = .002).

CONCLUSION

Bronchiectasis is common in patients with severe asthma. Sputum production and pathogen isolation in sputum may indicate the presence of bronchiectasis which seems to contribute to the severity of asthma.

Addressing unmet needs in understanding asthma mechanisms: From the European Asthma Research and Innovation Partnership (EARIP) Work Package (WP)2 collaborators

Asthma is a heterogeneous, complex disease with clinical phenotypes that incorporate persistent symptoms and acute exacerbations. It affects many millions of Europeans throughout their education and working lives and puts a heavy cost on European productivity. There is a wide spectrum of disease severity and control. Therapeutic advances have been slow despite greater understanding of basic mechanisms and the lack of satisfactory preventative and disease modifying management for asthma constitutes a significant unmet clinical need. Preventing, treating and ultimately curing asthma requires co-ordinated research and innovation across Europe. The European Asthma Research and Innovation Partnership (EARIP) is an FP7-funded programme which has taken a co-ordinated and integrated approach to analysing the future of asthma research and development. This report aims to identify the mechanistic areas in which investment is required to bring about significant improvements in asthma outcomes.

[The interactions between microorganisms and the small airways. A paediatric focus]

The spectrum of respiratory viruses is expanding and emerging diseases have been described regularly over the last fifteen years. The origin of these emerging respiratory viruses may be zoonotic (by crossing species barrier, after changes to RNA viruses such as avian influenza virus type A or coronaviruses), or related to the use of new identification techniques (metapneumovirus, bocavirus). The relationship between bronchiolitis and asthma is now better understood thanks to prospective follow up of birth cohorts. The role of rhinovirus has become predominant with respect to respiratory syncytial virus. The identification of predisposing factors immunological, functional, atopic and genetic, for the onset of asthma after rhinovirus infection suggests that viral infection reveals a predisposition rather than itself being a cause of asthma. The role of bacteria in the natural history of asthma is also beginning to be better understood. The results of the COPSAC Danish cohort have shown the frequency of bacterial identification during wheezy episodes before 3 years, and the impact of bacterial colonization at the age of one month on the onset of asthma by age 5 years. The role of bacterial infections in severe asthma in young children is also discussed.

Airway Microbiota in Severe Asthma and Relationship to Asthma Severity and Phenotypes

BACKGROUND

The lower airways harbor a community of bacterial species which is altered in asthma.

OBJECTIVES

We examined whether the lower airway microbiota were related to measures of asthma severity.

METHODS

We prospectively recruited 26 severe asthma, 18 non-severe asthma and 12 healthy subjects. DNA was extracted from induced sputum and PCR amplification of the V3-V5 region of bacterial 16S rRNA gene was performed.

RESULTS

We obtained 138,218 high quality sequences which were rarefied at 133 sequences/sample. Twenty OTUs had sequences ≥1% of total. There were marked differences in the distribution of Phyla between groups (P = 2.8x10-118). Bacteroidetes and Fusobacteria were reduced in non-severe and severe asthmatic groups. Proteobacteria were more common in non-severe asthmatics compared to controls (OR = 2.26; 95% CI = 1.94-2.64) and Firmicutes were increased in severe asthmatics compared to controls (OR = 2.15; 95%CI = 1.89-2.45). Streptococcal OTUs amongst the Firmicutes were associated with recent onset asthma, rhinosinusitis and sputum eosinophilia.

CONCLUSIONS

Sputum microbiota in severe asthma differs from healthy controls and non-severe asthmatics, and is characterized by the presence of Streptococcus spp with eosinophilia. Whether these organisms are causative for the pathophysiology of asthma remains to be determined.

Involvement of Toll-like receptor 2 and epidermal growth factor receptor signaling in epithelial expression of airway remodeling factors

Staphylococcus aureus (SA) colonization and infection is common, and may promote allergic or inflammatory airway diseases, such as asthma, cystic fibrosis, and chronic rhinosinusitis by interacting with airway epithelial cells. Airway epithelial cells not only comprise a physical barrier, but also play key roles in immune, inflammatory, repair, and remodeling responses upon encounters with pathogens. To elucidate the impact of SA on epithelial-mediated remodeling of allergic airways, we tested the hypothesis that SA can enhance the remodeling process. Normal human bronchial epithelial (NHBE) cells were stimulated with heat-killed SA (HKSA) or transforming growth factor (TGF) α. Cell extracts were collected to measure mRNA (real-time RT-PCR) and signaling molecules (Western blot); supernatants were collected to measure protein (ELISA) after 24 hours of stimulation. Epidermal growth factor receptor (EGFR) signaling inhibition experiments were performed using a specific EGFR kinase inhibitor (AG1478) and TGF-α was blocked with an anti-TGF-α antibody. HKSA induced both mRNA and protein for TGF-α and matrix metalloproteinase (MMP) 1 from NHBE cells by a Toll-like receptor 2-dependent mechanism. Recombinant human TGF-α also induced mRNA and protein for MMP-1 from NHBE cells; anti-TGF-α antibody inhibited HKSA-induced MMP-1, suggesting that endogenous TGF-α mediates the MMP-1 induction by HKSA. HKSA-induced MMP-1 expression was suppressed when a specific EGFR kinase inhibitor was added, suggesting that EGFR signaling was mediating the HKSA-induced MMP-1 release. Exposure or colonization by SA in the airway may enhance the remodeling of tissue through a TGF-α-dependent induction of MMP-1 expression, and may thereby promote remodeling in airway diseases in which SA is implicated, such as asthma and chronic rhinosinusitis.

Asthma phenotyping: a necessity for improved therapeutic precision and new targeted therapies

Asthma is a common heterogeneous disease with a complex pathophysiology that carries a significant mortality rate and high morbidity. Current therapies based on inhaled corticosteroids and long-acting β-agonists remain effective in a large proportion of patients with asthma, but ~10% (considered to have 'severe asthma') do not respond to these treatments even at high doses or with the use of oral corticosteroids. Analytical clustering methods have revealed phenotypes that include dependence on high-dose corticosteroid treatment, severe airflow obstruction and recurrent exacerbations associated with an allergic background and late onset of disease. One severe phenotype is eosinophilic inflammation-predominant asthma, with late-onset disease, rhinosinusitis, aspirin sensitivity and exacerbations. Blood and sputum eosinophilia have been used to distinguish patients with high Th2 inflammation and to predict therapeutic response to treatments targeted towards Th2-associated cytokines. New therapies in the form of humanized antibodies against Th2 targets, such as anti-IgE, anti-IL4Rα, anti-IL-5 and anti-IL-13 antibodies, have shown encouraging results in terms of reduction in exacerbations and improvement in airflow in patients with a 'Th2-high' expression profile and blood eosinophilia. Research efforts are now focusing on elucidating the phenotypes underlying the non-Th2-high (or Th2-low) group, which constitutes ~50% of severe asthma cases. There is an increasing need to use biomarkers to indicate the group of patients who will respond to a specifically targeted treatment. The use of improved tools to measure activity of disease, a better definition of severe asthma and the delineation of inflammatory pathways with omics analyses using computational tools, will lead to better-defined phenotypes for specific therapies.

Host-microbe interactions in distal airways: relevance to chronic airway diseases

This article is the summary of a workshop, which took place in November 2013, on the roles of microorganisms in chronic respiratory diseases. Until recently, it was assumed that lower airways were sterile in healthy individuals. However, it has long been acknowledged that microorganisms could be identified in distal airway secretions from patients with various respiratory diseases, including cystic fibrosis (CF) and non-CF bronchiectasis, chronic obstructive pulmonary disease, asthma and other chronic airway diseases (e.g. post-transplantation bronchiolitis obliterans). These microorganisms were sometimes considered as infectious agents that triggered host immune responses and contributed to disease onset and/or progression; alternatively, microorganisms were often considered as colonisers, which were considered unlikely to play roles in disease pathophysiology. These concepts were developed at a time when the identification of microorganisms relied on culture-based methods. Importantly, the majority of microorganisms cannot be cultured using conventional methods, and the use of novel culture-independent methods that rely on the identification of microorganism genomes has revealed that healthy distal airways display a complex flora called the airway microbiota. The present article reviews some aspects of current literature on host–microbe (mostly bacteria and viruses) interactions in healthy and diseased airways, with a special focus on distal airways.

Understanding host–microbe interactions in distal airways may lead to novel therapies for chronic airway diseaseshttp://ow.ly/HfENz

Airway dysbiosis: Haemophilus influenzae and Tropheryma in poorly controlled asthma

Asthma is a chronic inflammatory disorder of the airways where bacteria may act as protagonists of chronic inflammation. Little is known about the relation of airway inflammation to the presence of specific bacterial taxa. We sought to describe the sputum microbiome in adults with poorly controlled asthma.DNA was extracted from induced sputum and microbial communities were profiled using 16S rRNA pyrosequencing. Bacterial species were characterised, and the relationship between microbial populations, asthma inflammatory subtypes and other covariates was explored. Real-time PCR was used to identify Tropheryma whipplei and Haemophilus influenzae in sputum.Adults with neutrophilic asthma had reduced bacterial diversity and species richness. Tropheryma was identified and confirmed with real-time PCR in 12 (40%) participants. Haemophilus occurred most often in a group of younger atopic males with an increased proportion of neutrophils. PCR confirmed the presence of H. influenzae in 35 (76%) participants with poorly controlled asthma.There are phenotype-specific alterations to the airway microbiome in asthma. Reduced bacterial diversity combined with a high prevalence of H. influenzae was observed in neutrophilic asthma, whereas eosinophilic asthma had abundant T. whipplei.

[The lung microbiome in 2015: a window on chronic lung diseases]

Recent development of high-throughput sequencing methods has shown that the human respiratory tract (including lower airways) is not sterile as formerly thought, but composed of a previously unappreciated complex microbial community referred as the lung microbiome and composed of bacteria, viruses and fungi. However, many questions remain unresolved, especially in terms of lung microbiome role, its interactions with host but also with environmental pathogens. Although data are still limited, links have already been demonstrated between lung microbiome and chronic respiratory diseases (such as asthma, chronic obstructive pulmonary disease or cystic fibrosis). This lung microbiome appears to play an important role both in disease genesis and evolution, and consequently offers an emerging research field.

Infection in severe asthma exacerbations and critical asthma syndrome

In chronic persistent asthma and severe acute exacerbations of bronchial asthma, infectious agents are the predominant triggers that drive disease and airway pathobiology. In acute exacerbations of bronchial asthma (AEBA) including near fatal and fatal asthma, viral agents, particularly human rhinovirus-C, respiratory syncytial virus and influenza A appear to be the more prevalent and recurring threats. Both viral, and to a lesser extent bacterial agents, can play a role, and co-infection may also be present and worsen prognosis in hospitalized patients, placing a portion at risk for critical asthma syndrome. During severe acute exacerbations, infectious agents must be treated empirically, but the initial treatment regimens can vary and viral coverage may also vary based on seasonality and patient age. Early treatment with ceftriaxone and azithromycin, along with oseltamivir in winter months, should be initiated with all cases of severe exacerbations where infection is suspected, and definitely in critical asthma syndrome until infection is excluded by appropriate diagnostic testing. In this manuscript we will outline the impact of the major viral agents on severe asthma including the data from the 2009 H1N1 influenza pandemic. The role of bacterial infections in acute exacerbations of asthma will also be reviewed as well as the benefit of empiric antibiotics and the role of macrolides in both acute and chronic asthma.

Clinical phenotypes of asthma should link up with disease mechanisms

PURPOSE OF REVIEW

Asthma is a common disease which presents in various clinical forms and levels of severity. The current 'one size fits all' approach to treatment is suboptimal. Using unbiased cluster analysis has identified several asthma phenotypes. Understanding the underlying mechanisms driving these clusters may lead to better patient-orientated medicines.

RECENT FINDINGS

Clustering was initially performed on clinical features only, but the addition of biomarkers that characterize sputum and blood cellular profiles has enabled the prediction of responses to targeted therapies. Clusters of severe asthma include those on high-dose corticosteroid treatment associated with severe airflow obstruction and those with discordance between symptoms and sputum eosinophilia. Sputum eosinophilia can predict therapeutic responses to T-helper type 2 cytokine blockade. Further molecular phenotyping or endotyping of asthma will be necessary to determine new treatment strategies. Low T-helper type 2 expression may be predictive of poor therapeutic response to inhaled corticosteroids, but much less is known about this type of asthma.

SUMMARY

Phenotype-driven treatment of asthma will be further boosted by the integration of genetic, transcriptomic and proteomic technologies to defining distinct severe asthma phenotypes and biomarkers of therapeutic responses. This will lead towards stratified medicine for asthma.

Causes of chronic productive cough: An approach to management

A chronic 'productive' or 'wet' cough is a common presenting complaint for patients attending the adult respiratory clinic. Most reviews and guidelines suggest that the causes of a productive cough are the same as those of a non-productive cough and as such the same diagnostic pathway should be followed. We suggest a different diagnostic approach for patients with a productive cough, focussing on the conditions that are the most likely causes of this problem. This review is intended to briefly summarise the epidemiology, clinical features, pathophysiology and treatment of a number of conditions which are often associated with chronic productive cough to aid decision making when encountering a patient with this often distressing symptom. The conditions discussed include bronchiectasis, chronic bronchitis, asthma, eosinophilic bronchitis and immunodeficiency. We also propose an adult version of the paediatric diagnosis of protracted bacterial bronchitis (PBB) in patients with idiopathic chronic productive cough who appear to respond well to low dose macrolide therapy.

The changing face of asthma and its relation with microbes

During the past 50 years, the prevalence of asthma has increased and this has coincided with our changing relation with microorganisms. Asthma is a complex disease associated with local tissue inflammation of the airway that is determined by environmental, immunological, and host genetic factors. In a subgroup of sufferers, respiratory infections are associated with the development of chronic disease and more frequent inflammatory exacerbations. Recent studies suggest that these infections are polymicrobial in nature. Furthermore, there is increasing evidence that the recently discovered asthma airway microbiota may play a critical role in pathophysiological processes associated with the disease. Here, we discuss the current data regarding a possible role for infection in chronic asthma with a particular focus on the role bacteria may play. We discuss recent advances that are beginning to elucidate the complex relations between the microbiota and the immune response in asthma patients. We also highlight the clinical implications of these recent findings in regards to the development of novel therapeutic strategies.

High IFN-γ and low SLPI mark severe asthma in mice and humans

Severe asthma (SA) is a challenge to control, as patients are not responsive to high doses of systemic corticosteroids (CS). In contrast, mild-moderate asthma (MMA) is responsive to low doses of inhaled CS, indicating that Th2 cells, which are dominant in MMA, do not solely orchestrate SA development. Here, we analyzed broncholalveolar lavage cells isolated from MMA and SA patients and determined that IFN-γ (Th1) immune responses are exacerbated in the airways of individuals with SA, with reduced Th2 and IL-17 responses. We developed a protocol that recapitulates the complex immune response of human SA, including the poor response to CS, in a murine model. Compared with WT animals, Ifng-/- mice subjected to this SA model failed to mount airway hyperresponsiveness (AHR) without appreciable effect on airway inflammation. Conversely, AHR was not reduced in Il17ra-/- mice, although airway inflammation was lower. Computer-assisted pathway analysis tools linked IFN-γ to secretory leukocyte protease inhibitor (SLPI), which is expressed by airway epithelial cells, and IFN-γ inversely correlated with SLPI expression in SA patients and the mouse model. In mice subjected to our SA model, forced SLPI expression decreased AHR in the absence of CS, and it was further reduced when SLPI was combined with CS. Our study identifies a distinct immune response in SA characterized by a dysregulated IFN-γ/SLPI axis that affects lung function.