Mycoplasma pneumoniae infection increases airway collagen deposition in a murine model of allergic airway inflammation

The Impact of CC16 on Pulmonary Epithelial-Driven Host Responses during Mycoplasma pneumoniae Infection in Mouse Tracheal Epithelial Cells

Club Cell Secretory Protein (CC16) plays many protective roles within the lung; however, the complete biological functions, especially regarding the pulmonary epithelium during infection, remain undefined. We have previously shown that CC16-deficient (CC16-/-) mouse tracheal epithelial cells (MTECs) have enhanced Mp burden compared to CC16-sufficient (WT) MTECs; therefore, in this study, we wanted to further define how the pulmonary epithelium responds to infection in the context of CC16 deficiency. Using mass spectrometry and quantitative proteomics to analyze proteins secreted apically from MTECs grown at an air-liquid interface, we investigated the protective effects that CC16 elicits within the pulmonary epithelium during Mycoplasma pneumoniae (Mp) infection. When challenged with Mp, WT MTECs have an overall reduction in apical protein secretion, whereas CC16-/- MTECs have increased apical protein secretion compared to their unchallenged controls. Following Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) assessment, many of the proteins upregulated from CC16-/- MTECS (unchallenged and during Mp infection) were related to airway remodeling, which were not observed by WT MTECs. These findings suggest that CC16 may be important in providing protection within the pulmonary epithelium during respiratory infection with Mp, which is the major causative agent of community-acquired pneumoniae.

Exercise and Asthma

Asthma is a chronic lower respiratory disease that is very common worldwide, and its incidence is increasing year by year. Since the 1970s, asthma has become widespread, with approximately 300 million people affected worldwide and about 250,000 people have lost their lives. Asthma seriously affects people's physical and mental health, resulting in reduced learning efficiency, limited physical activities, and decreased quality of life. Therefore, raising awareness of the risk of asthma and how to effectively treat asthma have become important targets for the prevention and management of asthma in recent years. For patients with asthma, exercise training is a widely accepted adjunct to drug-based and non-pharmacological treatment. It has been recommended abroad that exercise prescriptions are an important part of asthma management.

Microbiome in Mechanisms of Asthma

The lung and gut microbiome are factors in asthma risk or protection. Relevant elements of the microbiome within both niches include the importance of the early life window for microbiome establishment, the diversity of bacteria, richness of bacteria, and effect of those bacteria on the local epithelium and immune system. Mechanisms of protection include direct anti-inflammatory action or induction of non-type 2 inflammation by certain bacterial colonies. The gut microbiome further impacts asthma risk through the contribution of metabolic products. This article reviews the mechanisms that connect the lung and gut microbiota to asthma development and severity.

Polydatin suppresses the development of lung inflammation and fibrosis by inhibiting activation of the NACHT domain-, leucine-rich repeat-, and pyd-containing protein 3 inflammasome and the nuclear factor-κB pathway after Mycoplasma pneumoniae infection

Mycoplasma pneumoniae (MP) can infect both the upper and lower respiratory tracts. Polydatin (PD), a traditional Chinese medicine, is known to have anti-inflammation and antifibrosis properties. However, the protective effects of PD against MP pneumonia (MPP) remain unclear. So, the aim of this study was to describe the therapeutic effects and underlying mechanisms of PD against MPP. BALB/c mice were assigned to three groups: a normal control group, MP infection group, or PD-treated MP infection group. BEAS-2B cells transfected with or without NACHT domain-, leucine-rich repeat-, and pyd-containing protein 3 (NLRP3) were used to confirm the protective mechanisms of PD. Immunohistochemical analysis, Western blot analysis, enzyme-linked immunosorbent assay, and flow cytometry were used in this study. The results showed that PD treatment suppressed MP-induced lung injury in mice by suppressing the expression of inflammatory factors and inhibiting the development of pulmonary fibrosis. Meanwhile, PD treatment inhibited activation of the NLRP3 inflammasome and nuclear factor κB (NF-κB) pathway. Overexpression of NLRP3 reversed the protective effect of PD against MP-induced injury of BEAS-2B cells. Taken together, these results indicate that PD treatment suppressed the inflammatory response and the development of pulmonary fibrosis by inhibiting the NLRP3 inflammasome and NF-κB pathway after MP infection.

The Protective Effect of Naringenin on Airway Remodeling after Mycoplasma Pneumoniae Infection by Inhibiting Autophagy-Mediated Lung Inflammation and Fibrosis

Our previous study has shown that Chinese medicine, Qingfei Tongluo formula (QTF), has a significantly therapeutic effect to Mycoplasma pneumoniae (MP) pneumonia (MPP). The aim of this study was to investigate the therapeutic effect and mechanism of naringenin (NRG) on MPP which was an important component of QTF. Here, we studied 124 children with or without MPP and compared inflammatory cytokines and fibrinogen-related protein expression with enzyme-linked immunosorbent assay. We also employed a BALB/c mouse model of MPP and divided the mice into three groups: ctrl (normal control mice), MPP (MP-infected mice), and MPP + NRG (MP-infected mice treated with NRG). BEAS-2B cells were used to confirm the relationship between autophagy, inflammation, and fibrosis. The results show proinflammatory cytokines (interleukin- [IL-] 6, IL-1β, and tumor necrosis factor-α), and transforming growth factor beta (TGF-β) expression was significantly increased after MP infection from both clinical and animal experiment. In vivo experimental confirmation showed that NRG treatment decreased MPP-induced lung injury in mice by inhibiting autophagy-mediated inflammatory cytokine expression and pulmonary fibrosis. In vitro experiments confirmed it. These results indicate that NRG treatment suppressed the inflammatory response and pulmonary fibrosis by inhibition of autophagy after MP infection.

Comparison of the ameliorative effects of Qingfei Tongluo formula and azithromycin on Mycoplasma pneumoniae pneumonia

Mycoplasma pneumoniae pneumonia (MPP) is a common disease in children. Qingfei Tongluo formula (QTF) has been used for the treatment of MPP clinically, but the therapeutic effect remains unclear compared to conventional treatments with Western medicines. Therefore, the aim of this study was to assess changes in the expression levels of relevant factors associated with microcirculation after MPP and to compare the therapeutic effect of QTF with that of azithromycin (AZM) on experimental mice with MPP. A total of 174 children admitted with clinical diagnoses of pneumonia (80 MPP and 94 non-MPP) were used to identify differences in the expression patterns of factors in the microcirculation using an enzyme-linked immunosorbent assay. A BALB/c mouse model of MPP infection was established to determine the therapeutic effect of QTF. The results showed that the expression level of thrombomodulin (TM), vascular endothelial growth factor (VEGF), d-dimer (D-D), interleukin (IL)-6, and IL-10 were upregulated after MPP both clinically in children and in the mouse model. After 3 days of therapy, the amount of total MPP DNA decreased, especially in the mid- and high-dose QTF treatment groups. The expression levels of VEGF, IL-6, and IL-10 also decreased in response to treatment with QTF or AZM. However, there was no influence on D-D levels. QTF treatment also decreased TM expression. In conclusion, QTF treatment inhibited the progression of MPP, reduced vascular permeability, and improved pulmonary microcirculation more effectively than conventional treatment with Western medicine.

Chronic Infection and Severe Asthma

Chronic bacterial infection is implicated in both the development and severity of asthma. The atypical bacteria Mycoplasma pneumoniae and Chlamydophila pneumoniae have been identified in the airways of asthmatics and correlated with clinical features such as adult onset, exacerbation risks, steroid sensitivity, and symptom control. Asthmatic patients with evidence of bacterial infection may benefit from antibiotic treatment directed towards these atypical organisms. Examination of the airway microbiome may identify microbial communities that confer risk for or protection from severe asthma.

The role of atypical infections and macrolide therapy in patients with asthma

For many years, the clinical benefit of macrolide use has been recognized in specific groups of patients with pulmonary disease. Dramatic improvement in survival of patients with diffuse panbronchiolitis is the most striking example of successful macrolide use as well as treatment of community acquired pneumonia caused by the atypical bacteria Mycoplasma, Chlamydophila, and Legionella. There also has been documentation of reduction in the exacerbation rate and of improvement in quality of life in patients with cystic fibrosis, bronchiectasis, chronic obstructive pulmonary disease, and reduction in post-lung transplantation bronchiolitis frequency. There has long been an interest in treating patients with severe asthma by using macrolides, but research results have not shown consistent clinical benefit in their use in the "general" population of patients with severe asthma. Rather, the successful use of macrolides seems to be in those patients with either documented Mycoplasma or Chlamydophila infection, or noneosinophilic asthma. Patients with neutrophil predominant phenotype severe asthma tend to show a decline in exacerbation rate, improved peak expiratory flows, and improved quality of life when treated with macrolides. This article will review the use of macrolides in the treatment of asthma.

Mycoplasma pneumoniae CARDS toxin exacerbates ovalbumin-induced asthma-like inflammation in BALB/c mice

Mycoplasma pneumoniae causes a range of airway and extrapulmonary pathologies in humans. Clinically, M. pneumoniae is associated with acute exacerbations of human asthma and a worsening of experimentally induced asthma in mice. Recently, we demonstrated that Community Acquired Respiratory Distress Syndrome (CARDS) toxin, an ADP-ribosylating and vacuolating toxin synthesized by M. pneumoniae, is sufficient to induce an asthma-like disease in BALB/cJ mice. To test the potential of CARDS toxin to exacerbate preexisting asthma, we examined inflammatory responses to recombinant CARDS toxin in an ovalbumin (OVA) murine model of asthma. Differences in pulmonary inflammatory responses between treatment groups were analyzed by histology, cell differentials and changes in cytokine and chemokine concentrations. Additionally, assessments of airway hyperreactivity were evaluated through direct pulmonary function measurements. Analysis of histology revealed exaggerated cellular inflammation with a strong eosinophilic component in the CARDS toxin-treated group. Heightened T-helper type-2 inflammatory responses were evidenced by increased expression of IL-4, IL-13, CCL17 and CCL22 corresponding with increased airway hyperreactivity in the CARDS toxin-treated mice. These data demonstrate that CARDS toxin can be a causal factor in the worsening of experimental allergic asthma, highlighting the potential importance of CARDS toxin in the etiology and exacerbation of human asthma.

Serial Changes in Serum Eosinophil-associated Mediators between Atopic and Non-atopic Children after Mycoplasma pneumoniae pneumonia

Purpose

Mycoplasma pneumoniae pneumonia (MP) is associated with the exacerbation, timing, and onset of asthma. The goal of this study was to elucidate the impact of MP on eosinophil-related hyper-reactive amplification in atopic children.

Methods

We studied 48 patients with MP (26 atopic, 22 non-atopic), between 3 and 12 years of age. Serial changes in blood eosinophil counts, serum interleukin-5 (IL-5), and serum eosinophil cationic protein (ECP) levels were measured in atopic and non-atopic children with MP upon admission, recovery, and at 2 months post-recovery. Serum IL-5 and ECP levels were measured by enzyme-linked immunosorbent assays; eosinophil counts were measured using an autoanalyzer.

Results

Serial changes in serum IL-5, ECP, and total eosinophil counts were significantly higher in atopic patients, relative to non-atopic controls (P≤0.001). Serum IL-5 and ECP levels were significantly higher in atopic patients at all three time points tested, while eosinophil counts were higher in the clinical recovery and follow-up phases, but not in the acute phase. Furthermore, among atopic patients, serum ECP levels were significantly higher in the recovery and follow-up phases than in the acute phase.

Conclusions

The present study demonstrated significant differences in eosinophil counts, serum IL-5, and serum ECP levels between atopic and non-atopic children with MP at admission, recovery, and 2 months after clinical recovery. These outcomes are suggestive of eosinophil-related hyperreactivity in atopic children, with this status maintained for at least 2 months after MP.

Antibiotics counteract the worsening of airway remodelling induced by infections in asthma

Asthma is associated with structural remodelling processes, including basement membrane thickening, increased vascularity and smooth muscle alterations. It is known that respiratory infections are associated with asthma exacerbation; infections can worsen asthma symptoms and influence susceptibility to asthma onset. How infections affect asthma is not fully elucidated. It is possible that the immune response, due to recurrent infections, leads to the pathogen's eradication but also increases bronchial inflammation, which induces airway remodelling in asthmatic subjects. We evaluated how infection affects lung remodelling and inflammatory responses and assessed the impact of antibiotic treatment in a murine model of asthma. Ovalbumin-sensitised BALB/c mice were divided into control, mild and chronic asthmatics. A subset of animals in each group was infected with Streptococcus pneumoniae and was treated with antibiotics. The results show an increase in key lung remodelling factors in mice with chronic asthma, particularly those infected with S. pneumoniae. Notably, antibiotic therapy attenuated these effects. These findings demonstrate for the first time that prompt antibiotic therapy may be useful to reduce lung remodelling progression in infected asthmatic subjects.

Bacterial superinfection following lung inflammatory disorders

The lung environment is designed to prevent innate responses to harmless commensal microorganisms and environmental antigens. Features of an intact respiratory epithelium are critical to this process. A damaged or altered lung epithelial surface will therefore remove or alter the suppressive signals delivered to local innate immune cells, and inflammation ensues. Timely resolution of inflammation is important to prevent bystander tissue damage. However, if resolving pathways themselves are prolonged or repeated, they too can cause undesirable consequences, including bacterial superinfections, which we discuss here.

Mycoplasma pneumoniae CARDS toxin induces pulmonary eosinophilic and lymphocytic inflammation

Mycoplasma pneumoniae causes acute and chronic lung infections in humans, leading to a variety of pulmonary and extrapulmonary sequelae. Of the airway complications of M. pneumoniae infection, M. pneumoniae-associated exacerbation of asthma and pediatric wheezing are emerging as significant sources of human morbidity. However, M. pneumoniae products capable of promoting allergic inflammation are unknown. Recently, we reported that M. pneumoniae produces an ADP-ribosylating and vacuolating toxin termed the community-acquired respiratory distress syndrome (CARDS) toxin. Here we report that naive mice exposed to a single dose of recombinant CARDS (rCARDS) toxin respond with a robust inflammatory response consistent with allergic disease. rCARDS toxin induced 30-fold increased expression of the Th-2 cytokines IL-4 and IL-13 and 70- to 80-fold increased expression of the Th-2 chemokines CCL17 and CCL22, corresponding to a mixed cellular inflammatory response comprised of a robust eosinophilia, accumulation of T cells and B cells, and mucus metaplasia. The inflammatory responses correlate temporally with toxin-dependent increases in airway hyperreactivity characterized by increases in airway restriction and decreases in lung compliance. Furthermore, CARDS toxin-mediated changes in lung function and histopathology are dependent on CD4(+) T cells. Altogether, the data suggest that rCARDS toxin is capable of inducing allergic-type inflammation in naive animals and may represent a causal factor in M. pneumoniae-associated asthma.

Models and approaches to understand the role of airway remodelling in disease

Airway remodelling is a collective term for changes in the amount or organisation of the cellular and molecular constituents of the airway wall. Remodelling occurs in and is associated with the pathophysiology of airways diseases including asthma and chronic obstructive pulmonary disease. The remodelling that occurs in these diseases exhibits both shared and distinct features. Remodelling is generally considered to be deleterious to airway function but recent studies also indicate potential protective effects. However, the true impact of different aspects of the remodelling process on lung function, both negative and positive, is poorly understood. In addition, the genetic susceptibility and processes by which environmental insults drive the cell and molecular events which result in airway remodelling and the potential for therapeutic reversibility are also incompletely understood. The last 10-15 years has seen the development of animal models of airway remodelling which have been refined and modified as new factors such as exacerbations and early life influences have been recognised as being of importance. In addition, invertebrate models have been put forward and complex in vitro culture systems and lung slice preparations developed. In parallel, imaging technology has developed to an extent where it is feasible using a combination of techniques to image structural components, cells and proteins in the airway wall as well as to analyse biological processes, cell and receptor activation non-invasively over time. The integration of data from in vivo and in vitro models together with use of imaging techniques in man and animals should allow validation of models, further our understanding of the pathophysiology of airway remodelling and potentially improve predictive accuracy for the translation of novel therapeutic agents into the clinic.

Effects of atypical infections with Mycoplasma and Chlamydia on asthma

Mycoplasma pneumoniae and Chlamydophila pneumoniae are atypical bacteria that are frequently found in patients with asthma. A definitive diagnosis of infection is often difficult to obtain because of limitations with sampling and detection. Numerous animal studies have outlined mechanisms by which these infections may promote allergic lung inflammation and airway remodeling. In addition, there is mounting evidence from human studies suggesting that atypical bacterial infections contribute to asthma exacerbations, chronic asthma, and disease severity. The role of antimicrobials directed against atypical bacteria in asthma is still under investigation.

Update on infection and antibiotics in asthma

Asthma pathogenesis seems to be a result of a complex mixture of genetic and environmental influences. There is evidence that Mycoplasma pneumoniae and Chlamydophila pneumoniae (formerly known as Chlamydia pneumoniae) play a role in promoting airway inflammation that could contribute to the onset and clinical course of asthma. Evidence also indicates that when antimicrobial therapy can eradicate or suppress these organisms, it may be possible to alter the course of the disease. Certain macrolide antibiotics have been shown to improve control of asthma symptoms and lung function in patients diagnosed with acute C. pneumoniae or M. pneumoniae infection. Positive polymerase chain reaction studies for C. pneumoniae or M. pneumoniae are needed to select asthma patients for chronic treatment. Macrolide antibiotics may also have independent anti-inflammatory activity that may be useful in the management of asthma and other inflammatory diseases.

[Asthma and Mycoplasma pneumoniae]

INTRODUCTION

A growing body of basic and clinical science implicates Mycoplasma pneumonia in asthma, but its exact contribution to asthma development, exacerbation and persistence is as yet unclear.

STATE OF THE ART

M. pneumoniae infection, with the induction of bronchial hyperresponsiveness, seems to be a precipitating factor for asthma development in predisposed subjects. M. pneumoniae has been seen both in acute exacerbation (18-20%) and in chronically infected adults with stable asthma, where it may be enhancing chronic airway inflammation.

PERSPECTIVES

If M. pneumoniae plays a role in the development or progression of asthma, its eradication might influence the clinical course of the disease and improve symptoms. Macrolide treatment, with antimicrobial and anti-inflammatory properties, could have a place in the management of asthma, especially steroid-dependent asthma.

CONCLUSIONS

M. pneumoniae infection seems to be important in asthma pathogenesis and the clinical course of the disease. Difficulty in detecting the pathogen complicates investigations. Ongoing research will further determine the place of macrolide antibiotics in asthma management.

Analysis of pulmonary inflammation and function in the mouse and baboon after exposure to Mycoplasma pneumoniae CARDS toxin

Mycoplasma pneumoniae produces an ADP-ribosylating and vacuolating toxin known as the CARDS (Community Acquired Respiratory Distress Syndrome) toxin that has been shown to be cytotoxic to mammalian cells in tissue and organ culture. In this study we tested the ability of recombinant CARDS (rCARDS) toxin to elicit changes within the pulmonary compartment in both mice and baboons. Animals responded to a respiratory exposure to rCARDS toxin in a dose and activity-dependent manner by increasing the expression of the pro-inflammatory cytokines IL-1α, 1β, 6, 12, 17, TNF-α and IFN-γ. There was also a dose-dependent increase in several growth factors and chemokines following toxin exposure including KC, IL-8, RANTES, and G-CSF. Increased expression of IFN-γ was observed only in the baboon; otherwise, mice and baboons responded to CARDS toxin in a very similar manner. Introduction of rCARDS toxin to the airways of mice or baboons resulted in a cellular inflammatory response characterized by a dose-dependent early vacuolization and cytotoxicity of the bronchiolar epithelium followed by a robust peribronchial and perivascular lymphocytic infiltration. In mice, rCARDS toxin caused airway hyper-reactivity two days after toxin exposure as well as prolonged airway obstruction. The changes in airway function, cytokine expression, and cellular inflammation correlate temporally and are consistent with what has been reported for M. pneumoniae infection. Altogether, these data suggest that the CARDS toxin interacts extensively with the pulmonary compartment and that the CARDS toxin is sufficient to cause prolonged inflammatory responses and airway dysfunction.

Bugs and asthma: a different disease?

The prevalence of asthma has dramatically increased in recent decades. Exacerbations of asthma are a large contributor to asthma-related costs, and are primarily caused by viral and atypical bacterial infections. Rhinoviruses (RVs) are the most common viruses detected after an asthma exacerbation. RVs, respiratory syncytial virus (RSV), and human metapneumovirus (hMPV) viral infections early in life can induce wheezing and are associated with the development of asthma later in life. Atypical bacterial infections from Mycoplasma pneumoniae and Chlamydia pneumoniae have also been linked to chronic asthma and potential asthma exacerbations. In this article, we will discuss recent developments in viral infections, specifically RV, RSV, and hMPV, and atypical bacterial infections as causes of asthma exacerbations, including new data focusing on the host immune response in airway epithelial cells and animal models of infection.

A low dose of Mycoplasma pneumoniae infection enhances an established allergic inflammation in mice: the role of the prostaglandin E2 pathway

BACKGROUND

Over 40% of chronic stable asthma patients have evidence of respiratory Mycoplasma pneumoniae (Mp) infection as detected by PCR, but not by serology and culture, suggesting that a low-level Mp is involved in chronic asthma. However, the role of such a low-level Mp infection in the regulation of allergic inflammation remains unknown.

OBJECTIVE

To determine the impact of a low-level Mp infection in mice with established airway allergic inflammation on allergic responses such as eosinophilia and chemokine eotaxin-2, and the underlying mechanisms [i.e. the prostaglandin E(2) (PGE(2)) pathway] since PGE(2) inhalation before an allergen challenge suppressed the eosinophil infiltration in human airways.

METHODS

BALB/c mouse models of ovalbumin (OVA)-induced allergic asthma with an ensuing low- or high-dose Mp were used to assess IL-4 expression, bronchoalveolar lavage (BAL) eosinophil, eotaxin-2 and PGE(2) levels, and lung mRNA levels of microsomal prostaglandin E synthase-1 (mPGES-1). Primary alveolar macrophages (pAMs) from naïve BALB/c mice were cultured to determine whether Mp-induced PGE(2) or exogenous PGE(2) down-regulates IL-4/IL-13-induced eotaxin-2.

RESULTS

Low-dose Mp in allergic mice significantly enhanced IL-4 and eotaxin-2, and moderately promoted lung eosinophilia, whereas high-dose Mp significantly reduced lung eosinophilia and tended to decrease IL-4 and eotaxin-2. Moreover, in both OVA-naïve and allergic mice, lung mPGES-1 mRNA and BAL PGE(2) levels were elevated in mice infected with high-dose, but not low-dose Mp. In pAMs, IL-4/IL-13 significantly increased eotaxin-2, which was reduced by Mp infection accompanied by dose-dependent PGE(2) induction. Exogenous PGE(2) inhibited IL-4/IL-13-induced eotaxin-2 in a dose-dependent manner.

CONCLUSIONS

This study highlights a novel concept on how different bacterial loads in the lung modify the established allergic airway inflammation and thus interact with an allergen to further induce Th2 responses. That is, unlike high-level Mp, low-level Mp fails to effectively induce PGE(2) to down-regulate allergic responses (e.g. eotaxin-2), thus maintaining or even worsening allergic inflammation in asthmatic airways.

The change of asthma-associated immunological parameters in children with Mycoplasma pneumoniae infection

BACKGROUND

Mycoplasma pneumoniae (M. pneumoniae), an atypical pathogen, is increasingly recognized as a common and important pathogen. Previous studies showed that M. pneumoniae infection may play a role in asthmatic mechanisms based on evidence collected from peripheral blood or sputum of patients or animal models. However, evidence reported from the airways of patients has been rare.

OBJECTIVE

To estimate the role of M. pneumoniae infection in asthma by measuring the immunological parameters from peripheral blood and bronchoalveolar lavage fluid (BALF) in pediatric patients with mycoplasma pneumonia.

METHODS

A total of 30 patients with mycoplasma pneumonia and 37 patients without M. pneumoniae infection undergoing fiberoptic bronchoscopy were reviewed. The peripheral blood cell count, immunoglobulins (Ig), BALF cell count, and other clinical and laboratory data were reviewed and analyzed.

RESULTS

There were significantly more patients with raised basophil counts in the M. pneumoniae group than that in the control group (p = 0.033). Serum immunoglobulin (Ig) A, IgM, and IgG levels in the M. pneumoniae group were significantly higher than those in the control group (p = 0.008, p = 0.011, and p = 0.019, respectively). The percentage of eosinophils in BALF cells was in the range 0 to 10% in M. pneumoniae patients, while it ranged between 0 and 4% in the control group with a significant difference (p = 0.043). In the M. pneumoniae group, we found that the percentage of eosinophils in the BALF cells was positively correlated with age, the percentage of peripheral eosinophils, and BALF lymphocytes (r = 0.298, p = 0.030; r = 0.341, p = 0.014; r = 0.387, p = 0.006; respectively) and negatively correlated with total peripheral white blood cell (r = -0.387, p = 0.005).

CONCLUSION

These results suggest that M. pneumonia infection is associated with the asthma mechanism, especially in older children.

Atypical bacteria and macrolides in asthma

: Chlamydophila pneumoniae and Mycoplasma pneumoniae are common pathogens causing acute illness in both the upper and lower airways. Several observations are supportive of a possible causative role of these pathogens in asthma; however, more evidence is required before this becomes meaningful in clinical practice. Atypical bacteria can enhance airway hyperresponsiveness and inflammation, both of which have been associated with exacerbations in patients with preexisting asthma. It is less clear whether the above mechanisms might also be responsible for the development of asthma. Difficulties in accurately diagnosing these infections contribute to such uncertainty. In the present report, evidence of the involvement of Chlamydophila and Mycoplasma infection in the development and the progression of asthma are reviewed.

Expression and arrangement of extracellular matrix proteins in the lungs of mice infected with Paracoccidioides brasiliensis conidia

Extracellular matrix (ECM) proteins are important modulators of migration, differentiation and proliferation for the various cell types present in the lungs; they influence the immune response as well as participate in the adherence of several fungi including Paracoccidioides brasiliensis. The expression, deposition and arrangement of ECM proteins such as laminin, fibronectin, fibrinogen, collagen and proteoglycans in the lungs of mice infected with P. brasiliensis conidia has been evaluated in this study, together with the elastic fibre system. Lungs of BALB/c mice infected with P. brasiliensis conidia were analysed for the different ECM proteins by histological and immunohistochemical procedures at different times of infection. In addition, laser scanning confocal microscopy and scanning electron microscopy were used. During the early periods, the lungs of infected animals showed an inflammatory infiltrate composed mainly of polymorphonuclear neutrophils (PMNs) and macrophages, while during the later periods, mice presented a chronic inflammatory response with granuloma formation. Re-arrangement and increased expression of all ECM proteins tested were observed throughout all studied periods, especially during the occurrence of inflammatory infiltration and formation of the granuloma. The elastic fibre system showed an elastolysis process in all experiments. In conclusion, this study provides new details of pulmonary ECM distribution during the course of paracoccidioidomycosis.

Asthma and atypical bacterial infection

A growing body of basic and clinical science implicates the atypical bacterial pathogens Mycoplasma pneumoniae and Chlamydophila (formerly Chlamydia) pneumoniae as potentially important factors in asthma, although their exact contribution to asthma development and/or persistence remains to be determined. Evidence from human studies links both M pneumoniae and C pneumoniae to new-onset wheezing, exacerbations of prevalent asthma, and long-term decrements in lung function, suggesting that these organisms can play an important role in the natural history of asthma. Furthermore, animal models of acute and chronic infection with these organisms indicate that they have the ability to modulate allergic sensitization and pulmonary physiologic and immune response to allergen challenge. These findings raise the possibility that, in at least some individuals with asthma, antibiotic therapy might have a role in long-term treatment. While antibiotics do not currently have a defined role in the treatment of stable patients with chronic asthma, there is emerging evidence that asthma symptoms and biomarkers of airway inflammation can improve when patients who have atypical bacterial infection as a cofactor in their asthma are treated with macrolide antibiotics. Ongoing research into the importance of atypical pathogens in asthma will further elucidate whether these infections are important in disease development or whether their prevalence is increased in asthmatic subjects due to chronic airway inflammation or other, yet unidentified, predisposing factors. Current studies will further define the role of macrolide antibiotics in the treatment of stable patients with asthma, ultimately determining whether these therapeutic agents have a place in asthma management.

Infections and asthma

A new paradigm is developing in regard to the interaction between infection and asthma. This paradigm comprises the acute exacerbations seen in asthma and also asthma chronicity. Viral infections have been commonly evaluated in acute exacerbations, but findings suggest viral-allergen and viral-bacterial interactions are important for chronicity. Most recently, studies are also invoking atypical bacterial infections, Mycoplasma pneumoniae and Chlamydia pneumoniae, as factors in both acute exacerbation and chronic asthma.

Mast cells protect mice from Mycoplasma pneumonia

RATIONALE

As the smallest free-living bacteria and a frequent cause of respiratory infections, mycoplasmas are unique pathogens. Mice infected with Mycoplasma pulmonis can develop localized, life-long airway infection accompanied by persistent inflammation and remodeling.

OBJECTIVE

Because mast cells protect mice from acute septic peritonitis and gram-negative pneumonia, we hypothesized that they defend against mycoplasma infection. This study tests this hypothesis using mast cell-deficient mice.

METHODS

Responses to airway infection with M. pulmonis were compared in wild-type and mast cell-deficient Kit(W-sh)/Kit(W-sh) mice and sham-infected control mice.

MEASUREMENTS AND MAIN RESULTS

Endpoints include mortality, body and lymph node weight, mycoplasma antibody titer, and lung mycoplasma burden and histopathology at intervals after infection. The results reveal that infected Kit(W-sh)/Kit(W-sh) mice, compared with other groups, lose more weight and are more likely to die. Live mycoplasma burden is greater in Kit(W-sh)/Kit(W-sh) than in wild-type mice at early time points. Four days after infection, the difference is 162-fold. Titers of mycoplasma-specific IgM and IgA appear earlier and rise higher in Kit(W-sh)/Kit(W-sh) mice, but antibody responses to heat-killed mycoplasma are not different compared with wild-type mice. Infected Kit(W-sh)/Kit(W-sh) mice develop larger bronchial lymph nodes and progressive pneumonia and airway occlusion with neutrophil-rich exudates, accompanied by angiogenesis and lymphangiogenesis. In wild-type mice, pneumonia and exudates are less severe, quicker to resolve, and are not associated with increased angiogenesis.

CONCLUSIONS

These findings suggest that mast cells are important for innate immune containment of and recovery from respiratory mycoplasma infection.