Association of Mycoplasma pneumoniae infection with increased risk of asthma in children

Adjuvant-independent airway sensitization and infection mouse models leading to allergic asthma

Asthma is a chronic respiratory disease of global importance. Mouse models of allergic asthma have been instrumental in advancing research and novel therapeutic strategies for patients. The application of relevant allergens and physiological routes of exposure in such models has led to valuable insights into the complexities of asthma onset and development as well as key disease mechanisms. Furthermore, environmental microbial exposures and infections have been shown to play a fundamental part in asthma pathogenesis and alter disease outcome. In this review, we delve into physiological mouse models of allergic asthma and explore literature reports on most significant interplays between microbial infections and asthma development with relevance to human disease.

A Comprehensive Metagenome Study Identifies Distinct Biological Pathways in Asthma Patients: An In-Silico Approach

Asthma is a multifactorial disease with phenotypes and several clinical and pathophysiological characteristics. Besides innate and adaptive immune responses, the gut microbiome generates Treg cells, mediating the allergic response to environmental factors and exposure to allergens. Because of the complexity of asthma, microbiome analysis and other precision medicine methods are now widely regarded as essential elements of efficient disease therapy. An in-silico pipeline enables the comparative taxonomic profiling of 16S rRNA metagenomic profiles of 20 asthmatic patients and 15 healthy controls utilizing QIIME2. Further, PICRUSt supports downstream gene enrichment and pathway analysis, inferring the enriched pathways in a diseased state. A significant abundance of the phylum Proteobacteria, Sutterella, and Megamonas is identified in asthma patients and a diminished genus Akkermansia. Nasal samples reveal a high relative abundance of Mycoplasma in the nasal samples. Further, differential functional profiling identifies the metabolic pathways related to cofactors and amino acids, secondary metabolism, and signaling pathways. These findings support that a combination of bacterial communities is involved in mediating the responses involved in chronic respiratory conditions like asthma by exerting their influence on various metabolic pathways.

The Role of Macrophage Autophagy in Asthma: A Novel Therapeutic Strategy

Asthma is a chronic respiratory disease frequently associated with airway inflammation and remodeling. The development of asthma involves various inflammatory phenotypes that impact therapeutic effects, and macrophages are master innate immune cells in the airway that exert diverse functions including phagocytosis, antigen presentation, and pathogen clearance, playing an important role in the pathogeneses of asthma. Recent studies have indicated that autophagy of macrophages affects polarization of phenotype and regulation of inflammation, which implies that regulating autophagy of macrophages may be a potential strategy for the treatment of asthma. Thus, this review summarizes the signaling pathways and effects of macrophage autophagy in asthma, which will provide a tactic for the development of novel targets for the treatment of this disease.

Clinical Characteristics of Macrolide-Refractory Mycoplasma pneumoniae Pneumonia in Korean Children: A Multicenter Retrospective Study

Mycoplasma pneumoniae is a major causative pathogen of community-acquired pneumonia in children, and the treatment of choice is macrolides. There is an increasing trend in reports of refractory clinical responses despite macrolide treatment due to the emergence of macrolide-resistant M. pneumoniae. Early discrimination of macrolide-refractory M. pneumoniae pneumonia (MrMP) from macrolide-sensitive M. pneumoniae pneumonia (MSMP) is vital; however, testing for macrolide susceptibility at the time of admission is not feasible. This study aimed to identify the characteristics of MrMP in Korean children, in comparison with those of MSMP. In this multicenter study, board-certified pediatric pulmonologists at 22 tertiary hospitals reviewed the medical records from 2010 to 2015 of 5294 children who were hospitalized with M. pneumoniae pneumonia and administered macrolides as the initial treatment. One-way analysis of variance and the Kruskal-Wallis test were used to compare differences between groups. Of 5294 patients (mean age, 5.6 years) included in this analysis, 240 (4.5%), 925 (17.5%), and 4129 (78.0%) had MrMP, macrolide-less effective M. pneumoniae pneumonia, and MSMP, respectively. Compared with the MSMP group, the MrMP group had a longer fever duration, overall (13.0 days) and after macrolide use (8.0 days). A higher proportion of MrMP patients had respiratory distress, pleural effusion, and lobar pneumonia. The mean aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and C-reactive protein levels were the highest in the MrMP group, along with higher incidences of extrapulmonary manifestations and atelectasis (during and post infection). Pre-existing conditions were present in 17.4% (n = 725/4159) of patients, with asthma being the most common (n = 334/4811, 6.9%). This study verified that MrMP patients show more severe initial radiographic findings and clinical courses than MSMP patients. MrMP should be promptly managed by agents other than macrolides.

Mycoplasma pneumoniae infection and risk of childhood asthma: A systematic review and meta-analysis

The etiology of childhood asthma is multifactorial, atypical bacterial pathogens, including Mycoplasma pneumoniae, have been proposed as possible risk factors or contributors. This review aims to assess the possible association between M. pneumoniae infection and childhood asthma. We searched major international literature databases (up to January 10, 2021) to identify relevant studies. We used a random-effects meta-analysis (REM) model to generate the pooled odds ratio (OR) and 95% confidence intervals (CIs). Several subgroups analyses were performed concerning the IgG, IgM, and DNA detection of M. pneumoniae infection. We included 22 eligible studies; these studies involved a total of 5064 children. We found that there was a statistically significant association between M. pneumoniae infection, as determined by IgM serology (OR, 3.13; 95% CI, 1.78-5.48), and DNA detection (OR, 1.57; 95% CI, 1.25-1.97) with increased risk of any type of childhood asthma. Moreover, children with acute asthma had significantly higher seropositivity for anti- M. pneumoniae IgM antibodies (OR, 4.43; 95% CI, 2.80-7.02) than children with stable asthma. Although our findings indicate a positive association between M. pneumoniae infection and childhood asthma, well-designed and -controlled studies are need in the future to rigorously test this association and identify the underlying mechanisms.

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.

ORMDL3 modulates airway epithelial cell repair in children with asthma under glucocorticoid treatment via regulating IL-33

BACKGROUND

Study found that glucocorticoids, as first-line treatments for asthma, fails to prevent asthma recurrence. Orosomucoid-like (ORMDL) 3 is associated to childhood asthma onset and involved in the inflammation and repair of airway epithelium. We explored the functional role of ORMDL3 in glucocorticoid treatment for childhood asthma.

METHODS

Mice were sensitized with Ovalbumin (OVA) and treated with Dexamethasone (Dex), followed by OVA challenge to establish a mouse model of asthma. Histopathological changes in lung tissues were observed by hematoxylin-eosin and masson staining. Human bronchial epithelial (16HBE-14°) cells were transfected with ORMDL3 overexpression plasmid and siRNA-interleukin (IL)-33 alone or in combination, followed by Dex. Cell viability was measured by MTT assay. Cell migration was evaluated by wound healing assay. The expressions of E-cadherin and Vimentin and the activation of NF-κB and MAPK/ERK in 16HBE-14° cells were assessed by Western blot. The expressions of ORMDL3 and IL-33 in lung tissues and 16HBE-14° cells were analyzed by qRT-PCR or Western blot.

RESULTS

Dex treatment alleviated the histopathological abnormality and reversed the overexpressions of ORMDL3 and IL-33 in the lung tissues of asthmatic mice. Overexpressed ORMDL3 enhanced migration and viability, decreased E-cadherin level, increased the levels of IL-33 and Vimentin, and promoted the phosphorylation of NF-κB and MAPK/ERK in Dex-treated 16HBE-14° cells, thus reversing the effect of Dex treatment. However, siRNA-IL-33 inhibited viability and migration, increased E-cadherin level, decreased Vimentin level, and suppressed the phosphorylation of NF-κB and MAPK/ERK, thus reversing the effect of overexpressed ORMDL3 in Dex-treated 16HBE-14° cells.

CONCLUSION

ORMDL3 overexpression helped airway epithelial cellrepairin asthma via regulating IL-33 expression.

Detection of specific bacterial agents by quantitative PCR assays in the bronchoalveolar lavage fluid of dogs with eosinophilic bronchopneumopathy vs. dogs with chronic bronchitis and healthy dogs

In humans, Mycoplasma pneumoniae and Bordetella pertussis infections are suggested to trigger or exacerbate asthma. Whether Mycoplasma or Bordetella are associated with chronic inflammatory bronchial diseases in dogs has not been investigated. The aim of this study was to assess detection rates of Mycoplasma canis (M. canis), M. cynos and Bordetella bronchiseptica (Bb), in dogs with eosinophilic bronchopneumopathy (EBP) and chronic bronchitis (CB), compared with healthy dogs. Specific quantitative PCR (qPCR) analysis for M. canis, M. cynos and Bb were retrospectively performed on bronchoalveolar lavage fluid (BALF) collected from 24 dogs with EBP, 21 dogs with CB and 15 healthy dogs. Possible associations between qPCR results and age, BALF cytology or clinical severity scores (CSS) in dogs with EBP were investigated. There was no difference in M. canis, M. cynos and Bb detection rates in dogs with EBP (n=6, n=2 and n=6, respectively) and dogs with CB (n=2, n=2 and n=2, respectively) compared with control dogs (n=4, n=2 and n=2, respectively). In dogs with EBP, the proportion that were qPCR-positive for Bb was higher in dogs with higher CSS (P=0.014) and BALF from Bb-positive dogs had higher percentage of neutrophils (P<0.001). Among dogs that were qPCR-positive for Bb, moderate to high loads were only detected in dogs with EBP. M. canis and M. cynos detection was not associated with EBP or CB; higher Bb loads were only present in dogs with EBP and high CSS. A possible cause and effect relationship between Bb infection or load and EBP remains unclear and requires further investigation.