Reduced toll-like receptor 4 and substance P gene expression is associated with airway bacterial colonization in children

Infection-Associated Mechanisms of Neuro-Inflammation and Neuro-Immune Crosstalk in Chronic Respiratory Diseases

Chronic obstructive airway diseases are characterized by airflow obstruction and airflow limitation as well as chronic airway inflammation. Especially bronchial asthma and chronic obstructive pulmonary disease (COPD) cause considerable morbidity and mortality worldwide, can be difficult to treat, and ultimately lack cures. While there are substantial knowledge gaps with respect to disease pathophysiology, our awareness of the role of neurological and neuro-immunological processes in the development of symptoms, the progression, and the outcome of these chronic obstructive respiratory diseases, is growing. Likewise, the role of pathogenic and colonizing microorganisms of the respiratory tract in the development and manifestation of asthma and COPD is increasingly appreciated. However, their role remains poorly understood with respect to the underlying mechanisms. Common bacteria and viruses causing respiratory infections and exacerbations of chronic obstructive respiratory diseases have also been implicated to affect the local neuro-immune crosstalk. In this review, we provide an overview of previously described neuro-immune interactions in asthma, COPD, and respiratory infections that support the hypothesis of a neuro-immunological component in the interplay between chronic obstructive respiratory diseases, respiratory infections, and respiratory microbial colonization.

Pathophysiology, causes and genetics of paediatric and adult bronchiectasis

Bronchiectasis has historically been considered to be irreversible dilatation of the airways, but with modern imaging techniques it has been proposed that 'irreversible' be dropped from the definition. The upper limit of normal for the ratio of airway to arterial development increases with age, and a developmental perspective is essential. Bronchiectasis (and persistent bacterial bronchitis, PBB) is a descriptive term and not a diagnosis, and should be the start not the end of the patient's diagnostic journey. PBB, characterized by airway infection and neutrophilic inflammation but without significant airway dilatation may be a precursor of bronchiectasis, and there are many commonalities in the microbiology and the pathology, which are reviewed in this article. A high index of suspicion is essential, and a history of chronic wet or productive cough for more than 4-8 weeks should prompt investigation. There are numerous underlying causes of bronchiectasis, although in many cases no cause is found. Causes include post-infectious, especially after tuberculosis, adenoviral or pertussis infection; aspiration syndromes; defects in host defence, which may solely affect the airways (cystic fibrosis, not considered in this review, and primary ciliary dyskinesia); and primary ciliary dyskinesia or be systemic, such as common variable immunodeficiency; genetic syndromes; and anatomical defects such as intraluminal airway obstruction (e.g. foreign body), intramural obstruction (e.g. complete cartilage rings) and external airway compression (e.g. by tuberculous lymph nodes). Identification of the underlying cause is important, because some of these conditions have specific treatments and others genetic implications for the family.

ERS statement on protracted bacterial bronchitis in children

This European Respiratory Society statement provides a comprehensive overview on protracted bacterial bronchitis (PBB) in children. A task force of experts, consisting of clinicians from Europe and Australia who manage children with PBB determined the overall scope of this statement through consensus. Systematic reviews addressing key questions were undertaken, diagrams in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement constructed and findings of relevant studies summarised. The final content of this statement was agreed upon by all members.The current knowledge regarding PBB is presented, including the definition, microbiology data, known pathobiology, bronchoalveolar lavage findings and treatment strategies to manage these children. Evidence for the definition of PBB was sought specifically and presented. In addition, the task force identified several major clinical areas in PBB requiring further research, including collecting more prospective data to better identify the disease burden within the community, determining its natural history, a better understanding of the underlying disease mechanisms and how to optimise its treatment, with a particular requirement for randomised controlled trials to be conducted in primary care.

Protracted bacterial bronchitis: The last decade and the road ahead

Cough is the single most common reason for primary care physician visits and, when chronic, a frequent indication for specialist referrals. In children, a chronic cough (>4 weeks) is associated with increased morbidity and reduced quality of life. One common cause of childhood chronic cough is protracted bacterial bronchitis (PBB), especially in children aged <6 years. PBB is characterized by a chronic wet or productive cough without signs of an alternative cause and responds to 2 weeks of appropriate antibiotics, such as amoxicillin-clavulanate. Most children with PBB are unable to expectorate sputum. If bronchoscopy and bronchoalveolar lavage are performed, evidence of bronchitis and purulent endobronchial secretions are seen. Bronchoalveolar lavage specimens typically reveal marked neutrophil infiltration and culture large numbers of respiratory bacterial pathogens, especially Haemophilus influenzae. Although regarded as having a good prognosis, recurrences are common and if these are frequent or do not respond to antibiotic treatments of up to 4-weeks duration, the child should be investigated for other causes of chronic wet cough, such as bronchiectasis. The contribution of airway malacia and pathobiologic mechanisms of PBB remain uncertain and, other than reduced alveolar phagocytosis, evidence of systemic, or local immune deficiency is lacking. Instead, pulmonary defenses show activated innate immunity and increased gene expression of the interleukin-1β signalling pathway. Whether these changes in local inflammatory responses are cause or effect remains to be determined. It is likely that PBB and bronchiectasis are at the opposite ends of the same disease spectrum, so children with chronic wet cough require close monitoring.

Translational research in pediatrics III: bronchoalveolar lavage

The role of flexible bronchoscopy and bronchoalveolar lavage (BAL) for the care of children with airway and pulmonary diseases is well established, with collected BAL fluid most often used clinically for microbiologic pathogen identification and cellular analyses. More recently, powerful analytic research methods have been used to investigate BAL samples to better understand the pathophysiological basis of pediatric respiratory disease. Investigations have focused on the cellular components contained in BAL fluid, such as macrophages, lymphocytes, neutrophils, eosinophils, and mast cells, as well as the noncellular components such as serum molecules, inflammatory proteins, and surfactant. Molecular techniques are frequently used to investigate BAL fluid for the presence of infectious pathologies and for cellular gene expression. Recent advances in proteomics allow identification of multiple protein expression patterns linked to specific respiratory diseases, whereas newer analytic techniques allow for investigations on surfactant quantification and function. These translational research studies on BAL fluid have aided our understanding of pulmonary inflammation and the injury/repair responses in children. We review the ethics and practices for the execution of BAL in children for translational research purposes, with an emphasis on the optimal handling and processing of BAL samples.

Serum level of substance P in patients with lung injuries due to sulfur mustard

Background:

Chronic bronchiolitis is the most important problems of chemical victims of mustard gas. Diverse studies suggest that substance P (SP) as a member of tachykinin neuropeptides, has a significant role in the neurogenic inflammation processes of the airways and lungs. We aimed to determine the serum level of SP in chemical victims of mustard gas and compare it with normal subjects.

Materials and Methods:

The chemical victims were divided into the 2 groups of 30:A group with mild to moderate pulmonary symptoms and other group with moderate to severe symptoms and compared with 3^rd group as healthy controls. After preparing our samples and using the SP kit, final analysis was performed with enzyme-linked immunosorbent assay reader.

Results:

The Concentration of circulatory SP levels in the chemical patients was 2.86 ± 1.47 ng/ml and had not a significant difference with the control group (3.15 ± 1.03 ng/ml) (P > 0.05). The circulatory SP levels were 2.48 ± 0.92 ng/ml and 3.28 ± 1.73 ng/ml in patients with moderate to severe symptoms and mild to moderates (P < 0.05) respectively.

Conclusion:

The SP may have a role in pulmonary complications of mustard gas. The lower level of SP in the moderate to severe patients may be due to corticosteroid consumption in such severe cases. However, further studies are needed to clarify the roles and mechanism of SP in this setting.

Changes in urine levels of substance P, vasoactive intestinal peptide and calcitonin-gene-related peptide in patients with urinary tract infections

Urinary tract infections (UTI) are important health problems and predisposing causes of UTI are not entirely known. Neuro-immune interactions play an important role in human health and disease. Capsaicin-sensitive sensory nerves which in nerve bladder extensively regulate immune system through neuropeptides such as substance P (SP), calcitonin-gene related peptide (CGRP) and vasoactive intestinal peptide (VIP). In addition these neuropeptides also have anti-bacterial effects. To determine how the levels of these peptides changes during UTI, 67 patients (50-90 years-old) diagnosed with UTI in Akdeniz University Faculty of Medicine Hospital were compared with 37 healthy people 50 years or older as the control group. Additionally, 7 patients with UTI symptoms (dysuria, urgency) but with sterile pyuria were also included in the study. Urine samples from 15 patients, whose symptoms regressed with control urine cultures being sterile, were taken after completion of the treatments. Urine neuropeptide levels were determined by ELISA. CGRP levels are significantly higher in patients with UTI, but did not associate with pyuria whereas SP and VIP levels were significantly lower in patients with sterile pyuria, indicating sensory nerve deficiency. Since CGRP exerts immunosuppressive effects, increased levels of the peptide may predispose to UTI. Furthermore, the connection between the observed sensory nerve deficiency and sterile pyuria warrants further studies.

Direct and indirect antimicrobial activities of neuropeptides and their therapeutic potential

As global resistance to conventional antibiotics rises we need to develop new strategies to develop future novel therapeutics. In our quest to design novel anti-infectives and antimicrobials it is of interest to investigate host-pathogen interactions and learn from the complexity of host defense strategies that have evolved over millennia. A myriad of host defense molecules are now known to play a role in protection against human infection. However, the interaction between host and pathogen is recognized to be a multifaceted one, involving countless host proteins, including several families of peptides. The regulation of infection and inflammation by multiple peptide families may represent an evolutionary failsafe in terms of functional degeneracy and emphasizes the significance of host defense in survival. One such family is the neuropeptides (NPs), which are conventionally defined as peptide neurotransmitters but have recently been shown to be pleiotropic molecules that are integral components of the nervous and immune systems. In this review we address the antimicrobial and anti-infective effects of NPs both in vitro and in vivo and discuss their potential therapeutic usefulness in overcoming infectious diseases. With improved understanding of the efficacy of NPs, these molecules could become an important part of our arsenal of weapons in the treatment of infection and inflammation. It is envisaged that targeted therapy approaches that selectively exploit the anti-infective, antimicrobial and immunomodulatory properties of NPs could become useful adjuncts to our current therapeutic modalities.

Effects of Rhinovirus Infection on Nasopharyngeal Bacterial Colonization in Infants With Wild or Variant Types of Mannose-Binding Lectin and Toll-Like Receptors 3 and 4

BACKGROUND

Development of respiratory tract infections is determined by interactions between viruses, bacteria, and the host innate immune response. We investigated the impact of natural rhinovirus infection on nasopharyngeal bacterial colonization in infants with or without gene polymorphisms of mannose-binding lectin (MBL) and Toll-like receptors (TLRs) 3 and 4.

METHODS

Rhinoviruses were detected by reverse transcription-polymerase chain reaction and bacteria by culture of nasopharyngeal specimens from 2- to 3-month-old infants. Gene polymorphisms in MBL at codons 52, 54, and 57, TLR3 Leu412Phe, and TLR4 Asp299Gly were detected by pyrosequencing.

RESULTS

Of 337 infants, 61 were positive for rhinovirus and 187 were colonized by Streptococcus pneumoniae, Moraxella catarrhalis, Haemophilus influenzae, or Staphylococcus aureus. Gene polymorphisms of MBL were detected in 32%, TLR3 in 51%, and TLR4 in 18% of subjects. Presence of rhinovirus was associated with increased colonization by S pneumoniae in children with MBL polymorphisms (8 of 20 [40%] with rhinovirus, vs 9 of 87 [10%] without rhinovirus; P = .003), but not in those with wild-type MBL. In logistic regression analyses, S pneumoniae colonization associated with MBL variant (P = .035) and with the interaction between rhinovirus and MBL variant (P = .004), and M catarrhalis colonization associated with the detection of rhinovirus (P = .033).

CONCLUSIONS

The association between rhinovirus infection and nasopharyngeal pneumococcal colonization in early infancy is linked to genetic variations of MBL.

An inactivated Pseudomonas aeruginosa medicament inhibits airway allergic inflammation and improves epithelial functions

The features of asthma are airway hyperresponsiveness (AHR), excess production of Th2 cytokines, and eosinophil accumulation in the lungs. To investigate the antiasthmatic potential of an inactivated Pseudomonas aeruginosa medicament (PPA), as well as the underlying mechanism involved, we studied the effects of PPA on airway and epithelial functions. Airway resistance, cell enumeration, and IL-4, IFN-γ, and IL-17 secretion in bronchoalveolar lavage fluid were assayed on an OVA-sensitized AHR animal model. Flow cytometry was used to observe the effects of PPA on cell proliferation, real-time PCR was used to test the expressions of toll like receptor 4 and 5, and Th17 signal molecules Act1, NF-kB negative regulator A20, and western blot were used to detect NF-kB expression on cultured human bronchial epithelial cells (BECs). PPA-treated animals had suppressed airway resistance, eosinophil and lymphocytes infiltration, and IL-4 and IL-17 secretion. PPA can stimulate toll-like receptor-4 and 5 expressions, promote cell proliferation in normal and OVA-treated BECs, significantly decrease Act1 and NF-kB, and increase A20 expression in BECs treated by OVA. Our data suggest the therapeutic mechanism by which PPA effectively treats allergic inflammation on reductions of airway responsiveness, eosinophil infiltration, IL-4 and IL-17 secretion, and improvements of epithelial functions.

Pulmonary innate immunity in children with protracted bacterial bronchitis

OBJECTIVE

To determine bronchoalveolar lavage (BAL) levels of 3 innate immunity components (human β-defensin-2 [hBD2], mannose-binding lectin [MBL], and surfactant protein-A [SP-A]), the relationship with airway neutrophilia and infection, and cytokine production of stimulated BAL cells in children with current protracted bacterial bronchitis (PBB), children with resolved PBB (PBB well), and controls.

STUDY DESIGN

BAL of 102 children (mean age 2.8 years) fulfilling predefined criteria of current PBB (n = 61), PBB well (n = 20), and controls (n = 21) was cultured (quantitative bacteriology) and viruses examined by polymerase chain reaction. hBD2, MBL, and SP-A were measured, and cytokine production by lipopolysaccharide-stimulated BAL cells was determined.

RESULTS

Median hBD2 and MBL levels were significantly higher in the current PBB group (hBD2 = 164.4, IQR 0-435.5 pg/mL; MBL = 1.7, 0.4-4 ng/mL) than in the PBB well group (hBD2 = 0, IQR 0-85.2; MBL = 0.6, IQR 0.03-2.9) and controls (hBD2 = 3.6, IQR 0-126; MBL = 0.4, IQR 0.02-79). hBD2 was significantly higher in children with airway infection (n = 54; median 76.9, IQR 0-397.3) compared with those without (n = 48; 0, IQR 0-236.3), P= .04. SP-A levels and cytokine production of stimulated BAL cells were similar between groups.

CONCLUSION

In children's airways, hBD2, but not MBL and SP-A, relates to inflammation and infection. In children with PBB, mechanisms involving airway hBD2 and MBL are augmented. These pulmonary innate immunity components and the ability of BAL cells to respond to stimuli are unlikely to be deficient.

Airway microbiology and host defences in paediatric non-CF bronchiectasis

Bronchiectasis in children without cystic fibrosis is most common in socioeconomically disadvantaged communities. Recurrent pneumonia in early childhood and defective pulmonary defences are important risk factors. These help establish a 'vicious cycle' of impaired mucociliary clearance, infection, airway inflammation and progressive lung injury. Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis and Pseudomonas aeruginosa are the main infecting pathogens. H. influenzae predominates across all ages, while P. aeruginosa is found in older children with advanced disease. It is uncertain whether viruses and upper airway commensal bacteria play an important aetiological role. Overall, the microbiological data are limited however and there are difficulties obtaining reliable respiratory specimens from young children. Bronchiectasis is a complex disorder resulting from susceptibility to pulmonary infection and poorly regulated respiratory innate and adaptive immunity. Airway inflammatory responses are excessive and persist, even once infection is cleared. Improved specimen collection, molecular techniques and biomarkers are needed to enhance management.

Substance P primes lipoteichoic acid- and Pam3CysSerLys4-mediated activation of human mast cells by up-regulating Toll-like receptor 2

Substance P (SP) is a neuropeptide with neuroimmunoregulatory activity that may play a role in susceptibility to infection. Human mast cells, which are important in innate immune responses, were analysed for their responses to pathogen-associated molecules via Toll-like receptors (TLRs) in the presence of SP. Human cultured mast cells (LAD2) were activated by SP and TLR ligands including lipopolysaccharide (LPS), Pam3CysSerLys4 (Pam3CSK4) and lipoteichoic acid (LTA), and mast cell leukotriene and chemokine production was assessed by enzyme-linked immunosorbent assay (ELISA) and gene expression by quantitative PCR (qPCR). Mast cell degranulation was determined using a β-hexosaminidase (β-hex) assay. SP treatment of LAD2 up-regulated mRNA for TLR2, TLR4, TLR8 and TLR9 while anti-immunoglobulin E (IgE) stimulation up-regulated expression of TLR4 only. Flow cytometry and western blot confirmed up-regulation of TLR2 and TLR8. Pretreatment of LAD2 with SP followed by stimulation with Pam3CSK4 or LTA increased production of leukotriene C4 (LTC(4) ) and interleukin (IL)-8 compared with treatment with Pam3CSK4 or LTA alone (>2-fold; P<0·01). SP alone activated 5-lipoxygenase (5-LO) nuclear translocation but also augmented Pam3CSK4 and LTA-mediated 5-LO translocation. Pam3CSK4, LPS and LTA did not induce LAD2 degranulation. SP primed LTA and Pam3CSK4-mediated activation of JNK, p38 and extracellular-signal-regulated kinase (ERK) and activated the nuclear translocation of c-Jun, nuclear factor (NF)-κB, activating transcription factor 2 (ATF-2) and cyclic-AMP-responsive element binding protein (CREB) transcription factors. Pretreatment with SP followed by LTA stimulation synergistically induced production of chemokine (C-X-C motif) ligand 8 (CXCL8)/IL-8, chemokine (C-C motif) ligand 2 (CCL2)/monocyte chemotactic protein 1 (MCP-1), tumour necrosis factor (TNF) and IL-6 protein. SP primes TLR2-mediated activation of human mast cells by up-regulating TLR expression and potentiating signalling pathways associated with TLR. These results suggest that neuronal responses may influence innate host defence responses.

Monocytes from children with clinically stable cystic fibrosis show enhanced expression of Toll-like receptor 4

Lung disease in patients with cystic fibrosis (CF) is characterized by recurrent bacterial respiratory infections and intense airway inflammation. Pattern recognition receptors such as Toll-like receptor 2 (TLR2) and TLR4 identify bacterial pathogens and activate the innate immune response. We therefore hypothesized that increased expression of these receptors would be found on circulating immune cells from children with CF. A cohort of 66 young children (median age 3 years) with CF was studied and compared to both healthy controls (n = 14) and children without CF who were being investigated for recurrent respiratory infections (non-CF disease controls; n = 17) of a similar age. Surface expression of TLR2 and TLR4 on peripheral blood monocytes was analyzed using flow cytometry. TLR4 expression was significantly higher in patients with CF compared to healthy controls (P = 0.017) and non-CF disease controls (P = 0.025) but did not vary according to the presence or absence of pulmonary infection with Gram-negative or Gram-positive bacteria (P = 0.387) in the CF group. In contrast, TLR2 expression was similar across all three study groups (P = 0.930). The increased surface expression of TLR4 seen in young children with CF appears to be related to having CF per se and not related to current pulmonary infection.

Immune responses of airway neutrophils are impaired in asthma

Neutrophilic inflammation is a key effector arm of the innate immune response. Neutrophils may contribute significantly to airway inflammation in certain asthma subtypes. The objective of this study is to investigate the innate immune responses of isolated airway and circulating neutrophils in asthma. Participants with asthma (n = 17) and healthy volunteers (n = 11) underwent induced sputum and blood collection. Neutrophils were isolated from dispersed selected sputum and blood granulocytes using magnetic cell separation. Neutrophils were cultured with or without lipopolysaccharide (100 ng/mL) for 24 hours. Innate immune mediators were measured by enzyme-linked immunosorbent assay (ELISA) and real-time polymerase chain reaction (PCR). Airway neutrophils from participants with asthma spontaneously released lower levels of interleukin (IL)-8, IL-1beta and tumor necrosis factor-alpha proteins, and had lower levels of cytokine gene expression compared to healthy controls. Toll-like receptor 4 (TLR4) gene expression was significantly decreased in airway neutrophils from participants with asthma compared to healthy volunteers. Resting and lipopolysaccharide (LPS)-stimulated circulating neutrophils had lower levels of TLR2 and IL-1beta gene expression in asthma, but were otherwise similar to healthy controls. No differences were seen for matrix metalloproteinase (MMP)-9 release in asthma. Innate immune responses of airway neutrophil cells are impaired in asthmatic subjects on prophylactic therapy and may impact on susceptibility to, and severity of, airway infections.

Asthma and protracted bronchitis: who fares better during an acute respiratory infection?

AIM

Acute respiratory infections (ARI) are common in children, and symptoms range from days to weeks. The aim of this study was to determine if children with asthma have more severe ARI episodes compared with children with protracted bronchitis and controls.

METHODS

Parents prospectively scored their child's next ARI using the Canadian acute respiratory illness and flu scale (CARIFS) and a validated cough diary (on days 1-7, 10 and 14 of illness). Children were age- and season-matched.

RESULTS

On days 10 and 14 of illness, children with protracted bronchitis had significantly higher median CARIFS when compared with children with asthma and healthy controls. On day 14, the median CARIFS were: asthma = 4.1 (interquartile range (IQR) 4.0), protracted bronchitis = 19.6 (IQR 25.8) and controls = 4.1 (IQR 5.25). The median cough score was significantly different between groups on days 1, 7, 10 and 14 (P < 0.001). A significantly higher proportion of children with protracted bronchitis (63%) were still coughing at day 14 in comparison with children with asthma (24%) and healthy controls (26%).

CONCLUSION

Children with protracted bronchitis had the most severe ARI symptoms and higher percentage of respiratory morbidity at day 14 in comparison with children with asthma and healthy controls.

Prospective assessment of protracted bacterial bronchitis: airway inflammation and innate immune activation

Protracted bacterial bronchitis (PBB) is a common cause of paediatric chronic moist cough. PBB is defined as the presence of isolated chronic moist cough which resolves with antibiotic therapy within 2 weeks and an absence of pointers suggesting alternative diagnoses. Our aim was to describe the clinical profile and examine the airway cellularity and likely promoters of neutrophilic inflammation in the bronchoalveolar lavage (BAL) of children with PBB compared with chronic cough due to other causes and controls. We explored the innate immune signaling receptors, toll-like receptors (TLR)-2 and TLR-4, as well as relevant effector molecules. A cross-sectional comparison was made of 100 children median age 2.58 years (with either PBB, coughing due to another cause or no cough controls) who underwent flexible bronchoscopy with lavage. BAL was evaluated for airway cytology, microbiology, inflammatory mediators interleukin 8 (IL-8) and active matrix metalloproteinase 9 (MMP-9) and TLR-2 and TLR-4 messenger RNA (mRNA) expression. Children with PBB had marked airway neutrophilia and increased median cytokine levels when compared to those with cough that resolved naturally and no cough controls: IL-8 0.67 versus 0.07 and 0.06 ng/ml (P < 0.005) and active MMP-9 7.25 versus 1.35 and 0.38 ng/ml (P < 0.005). The values for TLR-2 and TLR-4 mRNA expression were significantly elevated in children with PBB when compared to the control group. PBB is a paediatric condition which presents with chronic moist cough and its airway profile is characterized by intense neutrophilic airway inflammation with marked inflammatory mediator response and evidence of innate immune activation.

Disease surveillance using bronchoalveolar lavage

The role of pulmonary infection and inflammation in the pathogenesis of destructive lung disease in cystic fibrosis (CF) is undisputed. The use of bronchoscopy and bronchoalveolar lavage (BAL) has demonstrated that these processes may begin early in life and be present in the absence of overt clinical symptoms. Some children diagnosed following newborn screening can be infected with Pseudomonas aeruginosa in infancy. Studies using BAL have demonstrated a relationship between lower airway inflammation and bacterial load in the lungs; however, inflammation may occur in the absence of obvious current infection. BAL has the potential to provide a greater understanding of the pathogenesis of CF lung disease and microbiological surveillance provides the opportunity for early detection and eradication of P. aeruginosa. Lack of standardization inhibits the ability to compare data from different centres and to optimize treatment strategies. This review discusses the recommendations from a workshop held in early 2007 aimed at achieving a standardized approach to BAL in infants and young children with CF.

Chronic wet cough: Protracted bronchitis, chronic suppurative lung disease and bronchiectasis

The role of persistent and recurrent bacterial infection of the conducting airways (endobronchial infection) in the causation of chronic respiratory symptoms, particularly chronic wet cough, has received very little attention over recent decades other than in the context of cystic fibrosis (CF). This is probably related (at least in part) to the (a) reduction in non-CF bronchiectasis in affluent countries and, (b) intense focus on asthma. In addition failure to characterize endobronchial infections has led to under-recognition and lack of research. The following article describes our current perspective of inter-related endobronchial infections causing chronic wet cough; persistent bacterial bronchitis (PBB), chronic suppurative lung disease (CSLD) and bronchiectasis. In all three conditions, impaired muco-ciliary clearance seems to be the common risk factor that provides organisms the opportunity to colonize the lower airway. Respiratory infections in early childhood would appear to be the most common initiating event but other conditions (e.g., tracheobronchomalacia, neuromuscular disease) increases the risk of bacterial colonization. Clinically these conditions overlap and the eventual diagnosis is evident only with further investigations and long term follow up. However whether these conditions are different conditions or reflect severity as part of a spectrum is yet to be determined. Also misdiagnosis of asthma is common and the diagnostic process is further complicated by the fact that the co-existence of asthma is not uncommon. The principles of managing PBB, CSLD and bronchiectasis are the same. Further work is required to improve recognition, diagnosis and management of these causes of chronic wet cough in children.

Alveolar macrophage phagocytosis is impaired in children with poorly controlled asthma

BACKGROUND

Lower respiratory tract infection is a differentiating feature of children with poorly controlled asthma.

OBJECTIVE

Given the role of alveolar macrophages (AMs) in innate immunity, we hypothesized that AM phagocytosis might be impaired in poorly controlled asthma.

METHODS

Bronchoalveolar lavage fluid AMs were isolated from 28 asthmatic children (moderate asthma, n = 12; severe asthma, n = 16), 10 nonasthmatic children with chronic cough treated with inhaled corticosteroids, and 10 healthy adult control subjects. AMs were stimulated with LPS and exposed to fluorescein isothiocyanate-conjugated Staphylococcus aureus for 2 hours. Phagocytosis was quantified by using a phagocytic index (PI) calculated from the percentage of phagocytic cells multiplied by the relative fluorescence (RFU) units of S. aureus per cell. Apoptosis was determined from the percentage of cells positive for poly (adenosine diphosphate-ribose) polymerase.

RESULTS

Phagocytosis as measured by using the unstimulated PI was decreased in subjects with poorly controlled asthma (healthy control subjects, 9330 +/- 3992 RFU; chronic cough, 9042 +/- 5976 RFU; moderate asthma, 4361 +/- 2536 RFU; severe asthma, 3153 +/- 1886 RFU; P < .001) and remained unchanged with LPS stimulation. Children with severe asthma also had increased AM apoptosis, both the unstimulated and LPS-simulated states (P < .001), which correlated with the PI.

CONCLUSIONS

AM function is compromised in children with poorly controlled asthma and is characterized by decreased phagocytosis and increased apoptosis.