Microbes and asthma: the missing cellular and molecular links

The nasal mycobiome of individuals with allergic rhinitis and asthma differs from that of healthy controls in composition, structure and function

Allergic rhinitis (AR) and asthma (AS) are two of the most common chronic respiratory diseases and a major public health concern. Multiple studies have demonstrated the role of the nasal bacteriome in AR and AS, but little is known about the airway mycobiome and its potential association to airway inflammatory diseases. Here we used the internal transcriber spacers (ITS) 1 and 2 and high-throughput sequencing to characterize the nasal mycobiome of 339 individuals with AR, AR with asthma (ARAS), AS and healthy controls (CT). Seven to ten of the 14 most abundant fungal genera (Malassezia, Alternaria, Cladosporium, Penicillium, Wallemia, Rhodotorula, Sporobolomyces, Naganishia, Vishniacozyma, and Filobasidium) in the nasal cavity differed significantly (p ≤ 0.049) between AS, AR or ARAS, and CT. However, none of the same genera varied significantly between the three respiratory disease groups. The nasal mycobiomes of AR and ARAS patients showed the highest intra-group diversity, while CT showed the lowest. Alpha-diversity indices of microbial richness and evenness only varied significantly (p ≤ 0.024) between AR or ARAS and CT, while all disease groups showed significant differences (p ≤ 0.0004) in microbial structure (i.e., beta-diversity indices) when compared to CT samples. Thirty metabolic pathways (PICRUSt2) were differentially abundant (Wald's test) between AR or ARAS and CT patients, but only three of them associated with 5-aminoimidazole ribonucleotide (AIR) biosynthesis were over abundant (log2 Fold Change >0.75) in the ARAS group. AIR has been associated to fungal pathogenesis in plants. Spiec-Easi fungal networks varied among groups, but AR and ARAS showed more similar interactions among their members than with those in the CT mycobiome; this suggests chronic respiratory allergic diseases may disrupt fungal connectivity in the nasal cavity. This study contributes valuable fungal data and results to understand the relationships between the nasal mycobiome and allergy-related conditions. It demonstrates for the first time that the nasal mycobiota varies during health and allergic rhinitis (with and without comorbid asthma) and reveals specific taxa, metabolic pathways and fungal interactions that may relate to chronic airway disease.

Characterization of the oral mycobiome of Portuguese with allergic rhinitis and asthma

Allergic rhinitis and asthma are two prevailing chronic airway diseases and serious public health concerns. Previous research has already described the role of the airway bacteriome in these two diseases, but almost no study so far has explored the mycobiome and its possible association to airway inflammation. Here we sequenced the internal transcribed spacers (ITS) 1 and 2 to characterize the oral mycobiome of 349 Portuguese children and young adults with allergic rhinitis alone (AR) or with asthma (ARAS), asthmatics (AS) and healthy controls (HC). Our genomic analyses showed that the two most abundant fungal phyla (Ascomycota and Basidiomycota) and 3-5 of the 14 most abundant fungal genera (Cladosporium, Aspergillus, Aleurina, Candida and Rhodotorula) in the mouth differed significantly (P ≤ 0.04) between both rhinitic groups and HC. However, none of the same taxa varied significantly between the three respiratory disease groups (AR, ARAS and AS). The oral mycobiomes of respiratory ill patients showed the highest intra-group diversity (microbial richness and evenness), while HC showed the lowest, with all alpha-diversity indices varying significantly (P ≤ 0.0424) between them. Similarly, all disease groups showed significant differences (P ≤ 0.0052) in microbial structure (i.e., beta-diversity indices) when compared to HC samples. Thirty metabolic pathways (PICRUSt2) were differentially abundant (Wald's test) between AR or ARAS and HC patients, but only one of them (D-galactose degradation I) was over abundant (log2 Fold Change >0.75) in the ARAS group. Spiec-Easi fungal networks varied greatly among groups, which suggests chronic respiratory allergic diseases may alter fungal connectivity in the mouth. This study increases our comprehension of the role of the oral mycobiome in allergy-related conditions. It shows for the first time that the oral mycobiota changes during health and allergic rhinitis (with and without asthma comorbidity) and highlights specific taxa, metabolic pathways and fungal interactions that may relate to chronic airway disease.

Nasal Bacteriomes of Patients with Asthma and Allergic Rhinitis Show Unique Composition, Structure, Function and Interactions

Allergic rhinitis and asthma are major public health concerns and economic burdens worldwide. However, little is known about nasal bacteriome dysbiosis during allergic rhinitis, alone or associated with asthma comorbidity. To address this knowledge gap we applied 16S rRNA high-throughput sequencing to 347 nasal samples from participants with asthma (AS = 12), allergic rhinitis (AR = 53), allergic rhinitis with asthma (ARAS = 183) and healthy controls (CT = 99). One to three of the most abundant phyla, and five to seven of the dominant genera differed significantly (p < 0.021) between AS, AR or ARAS and CT groups. All alpha-diversity indices of microbial richness and evenness changed significantly (p < 0.01) between AR or ARAS and CT, while all beta-diversity indices of microbial structure differed significantly (p < 0.011) between each of the respiratory disease groups and controls. Bacteriomes of rhinitic and healthy participants showed 72 differentially expressed (p < 0.05) metabolic pathways each related mainly to degradation and biosynthesis processes. A network analysis of the AR and ARAS bacteriomes depicted more complex webs of interactions among their members than among those of healthy controls. This study demonstrates that the nose harbors distinct bacteriotas during health and respiratory disease and identifies potential taxonomic and functional biomarkers for diagnostics and therapeutics in asthma and rhinitis.

Volatile Organic Compounds, Bacterial Airway Microbiome, Spirometry and Exercise Performance of Patients after Surgical Repair of Congenital Diaphragmatic Hernia

The aim of this study was to analyze the exhaled volatile organic compounds (VOCs) profile, airway microbiome, lung function and exercise performance in congenital diaphragmatic hernia (CDH) patients compared to healthy age and sex-matched controls. A total of nine patients (median age 9 years, range 6-13 years) treated for CDH were included. Exhaled VOCs were measured by GC-MS. Airway microbiome was determined from deep induced sputum by 16S rRNA gene sequencing. Patients underwent conventional spirometry and exhausting bicycle spiroergometry. The exhaled VOC profile showed significantly higher levels of cyclohexane and significantly lower levels of acetone and 2-methylbutane in CDH patients. Microbiome analysis revealed no significant differences for alpha-diversity, beta-diversity and LefSe analysis. CDH patients had significantly lower relative abundances of Pasteurellales and Pasteurellaceae. CDH patients exhibited a significantly reduced Tiffeneau Index. Spiroergometry showed no significant differences. This is the first study to report the VOCs profile and airway microbiome in patients with CDH. Elevations of cyclohexane observed in the CDH group have also been reported in cases of lung cancer and pneumonia. CDH patients had no signs of impaired physical performance capacity, fueling controversial reports in the literature.

The profile of respiratory pathogens in induced sputum of elderly and non-elderly asthmatics

Introduction

Respiratory pathogens are thought to be involved in the pathogenesis and exacerbations of asthma at all ages; however, little is known about the airway microbiome in the elderly.

Aim of the study

To identify respiratory pathogens in the induced sputum (IS) of elderly asthmatics, and to determine the association between pathogens and the markers of asthma activity.

Material and methods

Twenty-nine subjects with stable asthma, 15 above 65 years of age and 14 aged 30-49 years, underwent clinical evaluation, fractional exhaled nitric oxide measurement, and sputum induction. Pathogens were detected by multiplex reverse transcription polymerase chain reaction. The periostin concentration of IS supernatants was measured by enzyme-linked immunosorbent assay. Serum eosinophil cationic protein and total IgE levels were measured by Immun^oCAP.

Results

Elderly patients, as compared to non-elderly, had significantly higher eosinophilia in IS, although other markers of eosinophilic inflammation were comparable. Half of the subjects were positive for Haemophilus influenzae. Chlamydophila pneumoniae was found in two subjects. Respiratory viruses were detected in more than 70% of patients. The detection rates and profiles of atypical bacteria and respiratory viruses were similar in both groups. Only in the elderly asthmatics was influenza A positivity associated with lower predicted FVC%, RSV A positivity connected with decreased tIgE concentration, and RSV B positivity related to a lower percentage of lymphocytes in IS.

Conclusions

Despite the existence of differences in some clinical and inflammatory characteristics of asthma between elderly and non-elderly asthmatics, the pathogen detection rates in the IS from the two groups are similar.

Nasal microbiota and symptom persistence in acute respiratory tract infections in infants

Acute respiratory tract infections (ARI) in infancy have been implicated in the development of chronic respiratory disease, but the complex interplay between viruses, bacteria and host is not completely understood. We aimed to prospectively determine whether nasal microbiota changes occur between the onset of the first symptomatic ARI in the first year of life and 3 weeks later, and to explore possible associations with the duration of respiratory symptoms, as well as with host, environmental and viral factors.

Nasal microbiota of 167 infants were determined at both time-points by 16S ribosomal RNA-encoding gene PCR amplification and subsequent pyrosequencing. Infants were clustered based on their nasal microbiota using hierarchical clustering methods at both time-points.

We identified five dominant infant clusters with distinct microbiota at the onset of ARI but only three clusters after 3 weeks. In these three clusters, symptom persistence was overrepresented in the Streptococcaceae-dominated cluster and underrepresented in the cluster dominated by “Others” (p<0.001). Duration of symptoms was not associated with the type of respiratory virus.

Infants with prolonged respiratory symptoms after their first ARI tend to exhibit distinct microbial compositions, indicating close microbiota–host interactions that seem to be of importance for symptom persistence and recovery.

Nasal microbiota in infants is associated with symptom persistence after acute symptomatic respiratory infections.http://ow.ly/3Mhh30mC1wJ

Pediatric asthma comprises different phenotypic clusters with unique nasal microbiotas

BACKGROUND

Pediatric asthma is the most common chronic childhood disease in the USA, currently affecting ~ 7 million children. This heterogeneous syndrome is thought to encompass various disease phenotypes of clinically observable characteristics, which can be statistically identified by applying clustering approaches to patient clinical information. Extensive evidence has shown that the airway microbiome impacts both clinical heterogeneity and pathogenesis in pediatric asthma. Yet, so far, airway microbiotas have been consistently neglected in the study of asthma phenotypes. Here, we couple extensive clinical information with 16S rRNA high-throughput sequencing to characterize the microbiota of the nasal cavity in 163 children and adolescents clustered into different asthma phenotypes.

RESULTS

Our clustering analyses identified three statistically distinct phenotypes of pediatric asthma. Four core OTUs of the pathogenic genera Moraxella, Staphylococcus, Streptococcus, and Haemophilus were present in at least 95% of the studied nasal microbiotas. Phyla (Proteobacteria, Actinobacteria, and Bacteroidetes) and genera (Moraxella, Corynebacterium, Dolosigranulum, and Prevotella) abundances, community composition, and structure varied significantly (0.05 < P ≤ 0.0001) across asthma phenotypes and one of the clinical variables (preterm birth). Similarly, microbial networks of co-occurrence of bacterial genera revealed different bacterial associations across asthma phenotypes.

CONCLUSIONS

This study shows that children and adolescents with different clinical characteristics of asthma also show different nasal bacterial profiles, which is indicative of different phenotypes of the disease. Our work also shows how clinical and microbial information could be integrated to validate and refine asthma classification systems and develop biomarkers of disease.

Novel human microbe-disease associations inference based on network consistency projection

Increasing evidence shows that microbes are closely related to various human diseases. Obtaining a comprehensive and detailed understanding of the relationships between microbes and diseases would not only be beneficial to disease prevention, diagnosis and prognosis, but also would lead to the discovery of new drugs. However, because of a lack of data, little effort has been made to predict novel microbe-disease associations. To date, few methods have been proposed to solve the problem. In this study, we developed a new computational model based on network consistency projection to infer novel human microbe-disease associations (NCPHMDA) by integrating Gaussian interaction profile kernel similarity of microbes and diseases, and symptom-based disease similarity. NCPHMDA is a non-parametric and global network based model that combines microbe space projection and disease space projection to achieve the final prediction. Experimental results demonstrated that the integrated space projection of microbes and diseases, and symptom-based disease similarity played roles in the model performance. Cross validation frameworks and case studies further illustrated the superior predictive performance over other methods.

Atopy Is Associated with Age at Asthma Onset in Elderly Patients

BACKGROUND

Asthma in the elderly population (60 years of age and older) is frequently underdiagnosed, as well as atopy. Atopy, although more prevalent in younger patients, can be a major cause of asthma in the elderly. Chronic obstructive pulmonary disease (COPD) and cardiovascular disease are common differential diagnoses, especially in elderly smokers.

OBJECTIVE

The objective of this study was to assess atopy and comorbidities in elderly patients with asthma.

METHODS

This was an observational and retrospective study involving elderly asthmatic patients followed up at a tertiary center. Patients were assessed for severity of asthma, frequency of atopy, and frequency of comorbidities concomitant with asthma. Then, they were classified according to their age at asthma onset and the groups compared with each other for atopy, spirometric parameters, and comorbidities.

RESULTS

This study included 243 elderly asthmatic patients, 71.8% of them presenting severe disease and 82.3% forced expiratory volume in 1 second (FEV₁) < 80%. Gastroesophageal reflux disease, obesity, and asthma-COPD overlap syndrome were observed, respectively, in 64%, 37%, and 13% of these patients. Atopy was observed in 63%, mainly in those with early onset disease, and its frequency decreased as the age of asthma onset increased (P < .05). Total serum IgE was higher for allergic patients and FEV₁ values were lower for patients with long-term asthma. Aspirin-exacerbated respiratory disease was more frequent in patients with nonallergic asthma.

CONCLUSIONS

Most elderly asthmatic patients followed up in our tertiary center were atopic and higher values of total serum IgE suggest atopy. Atopy was inversely correlated with age of asthma onset. The diagnosis of allergic asthma in the elderly population is essential to treat patients more properly, improving their quality of life and decreasing asthma morbidity and mortality.

Comparative Clinical, Physiological, and Inflammatory Characteristics of Elderly Subjects With or Without Asthma and Young Subjects With Asthma

BACKGROUND

Asthma seems to present in the elderly as a specific phenotype that remains to be further described. In this prospective observational study, we aimed to assess the multidimensional aspects of asthma in the elderly.

METHODS

In young (18 to 35 years old) subjects with mild to moderate asthma and elderly subjects (aged ≥60 years) either with or without mild to moderate asthma, we compared asthma control, health care and medication use, lung function, markers of airway and systemic inflammation, and adherence to therapy.

RESULTS

Fifty subjects were recruited in each group. Elderly people with asthma showed more marked airway obstruction compared with young people with asthma and elderly people without asthma. They also had poorer asthma control, mainly associated with a lower FEV₁, compared with young people with asthma, although airway responsiveness, health care use, prescribed doses of inhaled corticosteroids, and adherence to treatment were similar in both groups. Elderly subjects had an increase in some markers of systemic inflammation and bronchial epithelial dysfunction compared with young people with asthma. Blood eosinophils were higher in both asthma groups, particularly in elderly people with asthma. Sputum neutrophils were increased in both groups of elderly subjects and sputum eosinophils were increased in elderly people with asthma compared with the other two groups.

CONCLUSIONS

Asthma in the elderly presents as a specific phenotype associated with increased airway obstruction and mixed airway inflammation in addition to signs of systemic inflammation.

Increased Systemic Cytokine/Chemokine Expression in Asthmatic and Non-asthmatic Patients with Bacterial, Viral or Mixed Lung Infection

This study was aimed to determine the profiles of serum cytokines (IL-1β, TNF-α, IL-4, IL-5) and chemokines (MCP-1: monocyte chemoattract protein-1 and RANTES: regulated on activation normal T cell expressed and secreted) in individuals with an asthmatic versus a non-asthmatic background with bacterial, viral or mixed acute respiratory infection. Asthmatic (n = 14) and non-asthmatic (n = 29) patients with acute viral, bacterial or mixed (bacterial and viruses) respiratory infection were studied. Patients were also analysed as individuals with pneumonia or bronchitis. Healthy individuals with similar age and sex (n = 10) were used as controls. Cytokine/chemokine content in serum was determined by ELISA. Increased cytokine/chemokine concentration in asthmatic and non-asthmatic patients was observed. However, higher concentrations of chemokines (MCP-1 and RANTES) in asthmatic patients infected by viruses, bacteria or bacteria and viruses (mixed) than in non-asthmatic patients were observed. In general, viral and mixed infections were better cytokine/chemokine inducers than bacterial infection. Cytokine/chemokine expression was similarly increased in both asthmatic and non-asthmatic patients with pneumonia or bronchitis, except that RANTES remained at normal levels in bronchitis. Circulating cytokine profiles induced by acute viral, bacterial or mixed lung infection were not related to asthmatic background, except for chemokines that were increased in asthmatic status.

Nasopharyngeal Microbiome Diversity Changes over Time in Children with Asthma

BACKGROUND

The nasopharynx is a reservoir for pathogens associated with respiratory illnesses such as asthma. Next-generation sequencing (NGS) has been used to characterize the nasopharyngeal microbiome of infants and adults during health and disease; less is known, however, about the composition and temporal dynamics (i.e., longitudinal variation) of microbiotas from children and adolescents. Here we use NGS technology to characterize the nasopharyngeal microbiomes of asthmatic children and adolescents (6 to 18 years) and determine their stability over time.

METHODS

Two nasopharyngeal washes collected 5.5 to 6.5 months apart were taken from 40 children and adolescents with asthma living in the Washington D.C. area. Sequence data from the 16S-V4 rRNA gene region (~250 bp) were collected from the samples using the MiSeq platform. Raw data were processed in mothur (SILVA123 reference database) and Operational Taxonomic Units (OTU)-based alpha- and beta-diversity metrics were estimated. Relatedness among samples was assessed using PCoA ordination and Procrustes analyses. Differences in microbial diversity and taxon mean relative proportions were assessed using linear mixed effects models. Core microbiome analyses were also performed to identify stable and consistent microbes of the nasopharynx.

RESULTS AND DISCUSSION

A total of 2,096,584 clean 16S sequences corresponding to an average of 167 OTUs per sample were generated. Representatives of Moraxella*, Staphylococcus*, Dolosigranulum, Corynebacterium, Prevotella, Streptococcus*, Haemophilus*, Fusobacterium* and a Neisseriaceae genus accounted for 86% of the total reads. These nine genera have been previously found in the nasopharynxes of both infants and adults, but in different proportions. OTUs from the five genera highlighted (*) above defined the nasopharyngeal core microbiome at the 95% level. No significant differences in alpha- and beta-diversity were observed between seasons, but bacterial mean relative proportions of Haemophilus, Moraxella, Staphylococcus and Corynebacterium varied significantly between summer-fall and age groups (inter-patient variation). Additionally, OTUs varied significantly within patients between time points in 35 of the 40 patients analyzed. Future cross-sectional studies should be mindful of the temporal dynamics of the nasopharyngeal microbiota.

Toll-like receptors, triggering receptor expressed on myeloid cells family members and receptor for advanced glycation end-products in allergic airway inflammation

Asthma is a chronic disorder of the airways characterized by cellular infiltration, airway hyper-responsive and airway inflammation. Innate immune cells are the first line of defense against endogenous and exogenous signals in the airways and as such possess a diverse array of pattern recognition receptors. Toll-like receptors are crucial sentinels which when activated, can either promote or ameliorate the inflammatory response in predisposed individuals. The recently discovered triggering receptor expressed on myeloid cells family members are emerging mediators of inflammation. These receptors are believed to modulate inflammatory responses by collaborating with classic PRRs. Endogenous signals like HMGB-1, signaling through the receptor for advanced glycation end products, also promotes inflammation, however, its contribution to inflammation in the airways is not well known. Here, we discuss the role of each receptor in airway inflammation and highlight potential synergistic mechanisms, which contribute to disease pathogenesis in allergic asthma.

The respiratory microbiota during health and disease: a paediatric perspective

Recent studies investigating the relationship between the microbiota and disease are demonstrating novel concepts that could significantly alter the way we treat disease and promote health in the future. It is suggested that the microbiota acquired during childhood may shape the microbial community and affect immunological responses for later life, and could therefore be important in the susceptibility towards disease. Several diseases, including asthma, pneumonia, and otitis media, are associated with changes in composition and diversity of the respiratory microbiota. This review summarises current literature, focusing on the composition and development of the respiratory microbiota in children and its relationship with respiratory diseases.

The respiratory microbiome and innate immunity in asthma

PURPOSE OF REVIEW

The purpose of this study is to summarize recent studies of the lower respiratory microbiome in asthma, the role of innate immunity in asthma and strategies to understand complex microbiome-immune interactions in asthma.

RECENT FINDINGS

Recent evidence indicates that the composition of lower respiratory microbiota in asthmatic individuals, across a spectrum of disease severity, is altered compared with healthy individuals. Attributes of this altered airway microbiome have been linked to clinical and inflammatory features of asthma. The importance of innate immune cells and mucosal defense systems in asthma is increasingly appreciated and may be dysregulated in the disease.

SUMMARY

Interactions between the respiratory microbiome and innate mucosal immunity in asthma are complex and a challenge to dissect. Multiple avenues of investigation, leveraging a variety of methodologies, will need to be pursued to understand functional relationships to clinical and inflammatory phenotypes seen in asthma.

Dual Transcriptomic Profiling of Host and Microbiota during Health and Disease in Pediatric Asthma

BACKGROUND

High-throughput sequencing (HTS) analysis of microbial communities from the respiratory airways has heavily relied on the 16S rRNA gene. Given the intrinsic limitations of this approach, airway microbiome research has focused on assessing bacterial composition during health and disease, and its variation in relation to clinical and environmental factors, or other microbiomes. Consequently, very little effort has been dedicated to describing the functional characteristics of the airway microbiota and even less to explore the microbe-host interactions. Here we present a simultaneous assessment of microbiome and host functional diversity and host-microbe interactions from the same RNA-seq experiment, while accounting for variation in clinical metadata.

METHODS

Transcriptomic (host) and metatranscriptomic (microbiota) sequences from the nasal epithelium of 8 asthmatics and 6 healthy controls were separated in silico and mapped to available human and NCBI-NR protein reference databases. Human genes differentially expressed in asthmatics and controls were then used to infer upstream regulators involved in immune and inflammatory responses. Concomitantly, microbial genes were mapped to metabolic databases (COG, SEED, and KEGG) to infer microbial functions differentially expressed in asthmatics and controls. Finally, multivariate analysis was applied to find associations between microbiome characteristics and host upstream regulators while accounting for clinical variation.

RESULTS AND DISCUSSION

Our study showed significant differences in the metabolism of microbiomes from asthmatic and non-asthmatic children for up to 25% of the functional properties tested. Enrichment analysis of 499 differentially expressed host genes for inflammatory and immune responses revealed 43 upstream regulators differentially activated in asthma. Microbial adhesion (virulence) and Proteobacteria abundance were significantly associated with variation in the expression of the upstream regulator IL1A; suggesting that microbiome characteristics modulate host inflammatory and immune systems during asthma.

The Intestinal Microbiota in Acute Anorexia Nervosa and During Renourishment: Relationship to Depression, Anxiety, and Eating Disorder Psychopathology

OBJECTIVE

The relevance of the microbe-gut-brain axis to psychopathology is of interest in anorexia nervosa (AN), as the intestinal microbiota plays a critical role in metabolic function and weight regulation.

METHODS

We characterized the composition and diversity of the intestinal microbiota in AN, using stool samples collected at inpatient admission (T1; n = 16) and discharge (T2; n = 10). At T1, participants completed the Beck Depression and Anxiety Inventories and the Eating Disorder Examination-Questionnaire. Patients with AN were compared with healthy individuals who participated in a previous study (healthy comparison group; HCG). Genomic DNA was isolated from stool samples, and bacterial composition was characterized by 454 pyrosequencing of the 16S rRNA gene. Sequencing results were processed by the Quantitative Insights Into Microbial Ecology pipeline. We compared T1 versus T2 samples, samples from both points were compared with HCG (n = 12), and associations between psychopathology and T1 samples were explored.

RESULTS

In patients with AN, significant changes emerged between T1 and T2 in taxa abundance and beta (between-sample) diversity. Patients with AN had significantly lower alpha (within-sample) diversity than did HCG at both T1 (p = .0001) and T2 (p = .016), and differences in taxa abundance were found between AN patients and HCG. Levels of depression, anxiety, and eating disorder psychopathology at T1 were associated with composition and diversity of the intestinal microbiota.

CONCLUSIONS

We provide evidence of an intestinal dysbiosis in AN and an association between mood and the enteric microbiota in this patient population. Future directions include mechanistic investigations of the microbe-gut-brain axis in animal models and association of microbial measures with metabolic changes and recovery indices.

Corticosteroids in the treatment of acute asthma

Asthma is a prevalent chronic disease of the respiratory system and acute asthma exacerbations are among the most common causes of presentation to the emergency department (ED) and admission to hospital particularly in children. Bronchial airways inflammation is the most prominent pathological feature of asthma. Inhaled corticosteroids (ICS), through their anti-inflammatory effects have been the mainstay of treatment of asthma for many years. Systemic and ICS are also used in the treatment of acute asthma exacerbations. Several international asthma management guidelines recommend the use of systemic corticosteroids in the management of moderate to severe acute asthma early upon presentation to the ED. On the other hand, ICS use in the management acute asthma has been studied in different contexts with encouraging results in some and negative in others. This review sheds some light on the role of systemic and ICS in the management of acute asthma and discusses the current evidence behind their different ways of application particularly in relation to new developments in the field.

Reversible control by vitamin D of granulocytes and bacteria in the lungs of mice: an ovalbumin-induced model of allergic airway disease

Vitamin D may be essential for restricting the development and severity of allergic diseases and asthma, but a direct causal link between vitamin D deficiency and asthma has yet to be established. We have developed a 'low dose' model of allergic airway disease induced by intraperitoneal injection with ovalbumin (1 µg) and aluminium hydroxide (0.2 mg) in which characteristics of atopic asthma are recapitulated, including airway hyperresponsiveness, antigen-specific immunoglobulin type-E and lung inflammation. We assessed the effects of vitamin D deficiency throughout life (from conception until adulthood) on the severity of ovalbumin-induced allergic airway disease in vitamin D-replete and -deficient BALB/c mice using this model. Vitamin D had protective effects such that deficiency significantly enhanced eosinophil and neutrophil numbers in the bronchoalveolar lavage fluid of male but not female mice. Vitamin D also suppressed the proliferation and T helper cell type-2 cytokine-secreting capacity of airway-draining lymph node cells from both male and female mice. Supplementation of initially vitamin D-deficient mice with vitamin D for four weeks returned serum 25-hydroxyvitamin D to levels observed in initially vitamin D-replete mice, and also suppressed eosinophil and neutrophil numbers in the bronchoalveolar lavage fluid of male mice. Using generic 16 S rRNA primers, increased bacterial levels were detected in the lungs of initially vitamin D-deficient male mice, which were also reduced by vitamin D supplementation. These results indicate that vitamin D controls granulocyte levels in the bronchoalveolar lavage fluid in an allergen-sensitive manner, and may contribute towards the severity of asthma in a gender-specific fashion through regulation of respiratory bacteria.

Lung dendritic cell developmental programming, environmental stimuli, and asthma in early periods of life

Dendritic cells (DCs) are important cells of our innate immune system. Their role is critical in inducing adaptive immunity, tolerance, or allergic response in peripheral organs—lung and skin. The lung DCs are not developed prenatally before birth. The DCs develop after birth presumably during the first year of life; exposures to any foreign antigen or infectious organisms during this period can significantly affect DC developmental programming and generation of distinct DC phenotypes and functions. These changes can have both short-term and long-term health effects which may be very relevant in childhood asthma and predisposition for a persistent response in adulthood. An understanding of DC development at molecular and cellular levels can help in protecting neonates and infants against problematic environmental exposures and developmental immunotoxicity. This knowledge can eventually help in designing novel pharmacological modulators to skew the DC characteristics and immune responses to benefit the host across a lifetime.

The microbiome of the lung

Investigation of the lung microbiome is a relatively new field. Although the lungs were classically believed to be sterile, recently published investigations have identified microbial communities in the lungs of healthy humans. At the present time, there are significant methodologic and technical hurdles that must be addressed in ongoing investigations, including distinguishing the microbiota of the upper and lower respiratory tracts. However, characterization of the lung microbiome is likely to provide important pathogenic insights into cystic fibrosis, respiratory disease of the newborn, chronic obstructive pulmonary disease, and asthma. In addition to characterization of the lung microbiome, the microbiota of the gastrointestinal tract have profound influence on the development and maintenance of lung immunity and inflammation. Further study of gastrointestinal-respiratory interactions is likely to yield important insights into the pathogenesis of pulmonary diseases, including asthma. As this field advances over the next several years, we anticipate that studies using larger cohorts, multicenter designs, and longitudinal sampling will add to our knowledge and understanding of the lung microbiome.

Gut microbiota, immune development and function

The microbiota of Westerners is significantly reduced in comparison to rural individuals living a similar lifestyle to our Paleolithic forefathers but also to that of other free-living primates such as the chimpanzee. The great majority of ingredients in the industrially produced foods consumed in the West are absorbed in the upper part of small intestine and thus of limited benefit to the microbiota. Lack of proper nutrition for microbiota is a major factor under-pinning dysfunctional microbiota, dysbiosis, chronically elevated inflammation, and the production and leakage of endotoxins through the various tissue barriers. Furthermore, the over-comsumption of insulinogenic foods and proteotoxins, such as advanced glycation and lipoxidation molecules, gluten and zein, and a reduced intake of fruit and vegetables, are key factors behind the commonly observed elevated inflammation and the endemic of obesity and chronic diseases, factors which are also likely to be detrimental to microbiota. As a consequence of this lifestyle and the associated eating habits, most barriers, including the gut, the airways, the skin, the oral cavity, the vagina, the placenta, the blood-brain barrier, etc., are increasingly permeable. Attempts to recondition these barriers through the use of so called 'probiotics', normally applied to the gut, are rarely successful, and sometimes fail, as they are usually applied as adjunctive treatments, e.g. in parallel with heavy pharmaceutical treatment, not rarely consisting in antibiotics and chemotherapy. It is increasingly observed that the majority of pharmaceutical drugs, even those believed to have minimal adverse effects, such as proton pump inhibitors and anti-hypertensives, in fact adversely affect immune development and functions and are most likely also deleterious to microbiota. Equally, it appears that probiotic treatment is not compatible with pharmacological treatments. Eco-biological treatments, with plant-derived substances, or phytochemicals, e.g. curcumin and resveratrol, and pre-, pro- and syn-biotics offers similar effects as use of biologicals, although milder but also free from adverse effects. Such treatments should be tried as alternative therapies; mainly, to begin with, for disease prevention but also in early cases of chronic diseases. Pharmaceutical treatment has, thus far, failed to inhibit the tsunami of endemic diseases spreading around the world, and no new tools are in sight. Dramatic alterations, in direction of a paleolithic-like lifestyle and food habits, seem to be the only alternatives with the potential to control the present escalating crisis. The present review focuses on human studies, especially those of clinical relevance.

Respiratory viral infections in children with asthma: do they matter and can we prevent them?

BACKGROUND

Asthma is a major public health problem with a huge social and economic burden affecting 300 million people worldwide. Viral respiratory infections are the major cause of acute asthma exacerbations and may contribute to asthma inception in high risk young children with susceptible genetic background. Acute exacerbations are associated with decreased lung growth or accelerated loss of lung function and, as such, add substantially to both the cost and morbidity associated with asthma.

DISCUSSION

While the importance of preventing viral infection is well established, preventive strategies have not been well explored. Good personal hygiene, hand-washing and avoidance of cigarette smoke are likely to reduce respiratory viral infections. Eating a healthy balanced diet, active probiotic supplements and bacterial-derived products, such as OM-85, may reduce recurrent infections in susceptible children. There are no practical anti-viral therapies currently available that are suitable for widespread use.

SUMMARY

Hand hygiene is the best measure to prevent the common cold. A healthy balanced diet, active probiotic supplements and immunostimulant OM-85 may reduce recurrent infections in asthmatic children.

The prevalence and identity of Chlamydia-specific IgE in children with asthma and other chronic respiratory symptoms

Background

Recent studies have confirmed the presence of viable Chlamydia in the bronchoalveolar lavage (BAL) fluid of pediatric patients with airway hyperresponsiveness. While specific IgG and IgM responses to C. pneumoniae are well described, the response and potential contribution of Ag-specific IgE are not known. The current study sought to determine if infection with Chlamydia triggers the production of pathogen-specific IgE in children with chronic respiratory diseases which might contribute to inflammation and pathology.

Methods

We obtained BAL fluid and serum from pediatric respiratory disease patients who were generally unresponsive to corticosteroid treatment as well as sera from age-matched control patients who saw their doctor for wellness checkups. Chlamydia-specific IgE was isolated from BAL and serum samples and their specificity determined by Western blot techniques. The presence of Chlamydia was confirmed by species-specific PCR and BAL culture assays.

Results

Chlamydial DNA was detected in the BAL fluid of 134/197 (68%) patients. Total IgE increased with age until 15 years old and then decreased. Chlamydia-specific IgE was detected in the serum and/or BAL of 107/197 (54%) patients suffering from chronic respiratory disease, but in none of the 35 healthy control sera (p < 0.0001). Of the 74 BAL culture-positive patients, 68 (91.9%, p = 0.0001) tested positive for Chlamydia-specific IgE. Asthmatic patients had significantly higher IgE levels compared to non-asthmatics (p = 0.0001). Patients who were positive for Chlamydia DNA or culture had significantly higher levels of serum IgE compared to negative patients (p = 0.0071 and p = 0.0001 respectively). Only 6 chlamydial antigens induced Chlamydia-specific IgE and patients with C. pneumoniae-specific IgE had significantly greater levels of total IgE compared to C. pneumoniae-specific IgE negative ones (p = 0.0001).

Conclusions

IgE antibodies play a central role in allergic inflammation; therefore production of Chlamydia-specific IgE may prove significant in the exacerbation of chronic, allergic airway diseases, thus highlighting a direct role for Chlamydia in asthma pathogenesis.