Investigating paediatric airways by non-bronchoscopic lavage: normal cellular data

Breastfeeding in infants who aspirate may increase risk of pulmonary inflammation

OBJECTIVE

To evaluate management strategies and pulmonary outcomes for breastfed infants with oropharyngeal dysphagia.

STUDY DESIGN

We performed a retrospective cohort study of breastfed infants diagnosed with oropharyngeal dysphagia with documented aspiration or laryngeal penetration on videofluoroscopic swallow study (VFSS). Medical records were reviewed for VFSS results and speech-language pathologist recommendations following VFSS, results of chest x-ray, results of bronchoalveolar lavage (BAL) within 1 year of VFSS, and aspiration-related hospitalizations occurring before or within 1 year of VFSS. Subjects were categorized as cleared or not cleared to breastfeed based on the VFSS. Proportions were compared with Chi-square and Fisher's exact tests and means with Student's t-tests.

RESULTS

Seventy-six infants (4.7 ± 0.4 months old) were included; 50% (38) had aspiration and 50% (38) had laryngeal penetration. After VFSS, 70% (53) were cleared to breastfeed while 30% (23) were not cleared to breastfeed. Patients with aspiration were less likely to be cleared to breastfeed (p = .006); however, 55% (21/38) of those with aspiration were still cleared to breastfeed. Infants cleared to breastfeed had significantly more pulmonary hospitalizations (p = .04) and were also at increased risk of elevated neutrophil count (p = .02) and culture growth on BAL (p = .01). Significantly increased abnormal neutrophil count was also found in those cleared to breastfeed with laryngeal penetration (p = .01).

CONCLUSIONS

Infants with oropharyngeal dysphagia counseled to continue breastfeeding had increased risk of BAL inflammation and more pulmonary hospitalizations compared to those that were told to stop breastfeeding.

Bronchoalveolar lavage profiles in uncontrolled wheezy children compared by asthma predictive index

OBJECTIVE

The asthma predictive index (API) predicts later asthma in preschoolers with frequent wheeze. We hypothesized that airway cytology differs between API positive (API+)/negative (API-) children with uncontrolled/recurrent wheezing with dominance of eosinophils in API+ and neutrophils in API- groups respectively. The main objective of this study is to compare bronchoalveolar lavage (BAL) cell profiles in API+/API- children with recurrent wheezing unresponsive to inhaled corticosteroids (ICS).

DESIGN

Retrospective analysis of BAL in 43 children, 3-36 months (median: 14 months) receiving ICS (31 API+, 12 API-). BAL cell differential counts, bacterial/viral cultures, and lipid-laden macrophage percentages were analyzed. Cell counts presented as median (range).

RESULTS

Neutrophil percentages were increased in both groups (API- 16% [1%-76%]; API+ 42% [1%-95%]; p = NS). Cell percentages were similar for lymphocytes (API- 12% [1%-30%]; API+ 7% [1%-37%]), and macrophages (API- 67.5% [12%-97%]; API+ 41% [2%-94%]). Eosinophil percentages were low in both groups (API- 1% [1%-2%]; API+ 1% [1%-11%]). There was no difference in cellular distributions using absolute cell counts comparing API groups. Bacterial cultures were positive in 18 (60%) API+ and 5 (41%) API- patients (p = 0.10).

CONCLUSION

Cell profiles do not differ between API groups in children ≤36 months with recurrent wheezing unresponsive to ICS. Neutrophil percentages and total granulocyte count correlate with positive bacterial cultures independent of API status. Persistent bacterial bronchitis likely plays an important role in the persistence of symptoms unresponsive to ICS therapy regardless of API status with a trend to more positive cultures in API positive children.

Emerging Human Coronavirus Infections (SARS, MERS, and COVID-19): Where They Are Leading Us

Coronavirus infections are responsible for mild, moderate, and severe infections in birds and mammals. These were first isolated in humans as causal microorganisms responsible for common cold. The 2002-2003 SARS epidemic caused by SARS-CoV and 2012 MERS epidemic (64 countries affected) caused by MERS-CoV showed their acute and fatal side. These two CoV infections killed thousands of patients infected worldwide. However, WHO has still reported the MERS case in December 2019 in middle-eastern country (Saudi Arabia), indicating the MERS epidemic has not ended completely yet. Although we have not yet understood completely these two CoV epidemics, a third most dangerous and severe CoV infection has been originated in the Wuhan city, Hubei district of China in December 2019. This CoV infection called COVID-19 or SARS-CoV2 infection has now spread to 210 countries and territories around the world. COVID-19 has now been declared a pandemic by the World Health Organization (WHO). It has infected more than 16.69 million people with more than 663,540 deaths across the world. Thus the current manuscript aims to describe all three (SARS, MERS, and COVID-19) in terms of their causal organisms (SARS-CoV, MERS-CoV, and SARS-CoV2), similarities and differences in their clinical symptoms, outcomes, immunology, and immunopathogenesis, and possible future therapeutic approaches.

Leukotriene A4 Hydrolase Activation and Leukotriene B4 Production by Eosinophils in Severe Asthma

Asthma is associated with the overproduction of leukotrienes (LTs), including LTB4. Patients with severe asthma can be highly responsive to 5-lipoxygenase (5-LO) inhibition, which blocks production of both the cysteinyl LTs and LTB4. Production of LTB4 has traditionally been ascribed to neutrophils, mononuclear phagocytes, and epithelial cells, and acts as a chemoattractant for inflammatory cells associated with asthma. The source of LTB4 is unclear, especially in eosinophilic asthma. We speculated that the benefit of 5-LO inhibition could be mediated in part by inhibition of eosinophil-derived LTB4. LTB4 concentrations were assayed in BAL fluid from patients with severe asthma characterized by isolated neutrophilic, eosinophilic, and paucigranulocytic inflammation. Expression of LTA4 hydrolase (LTA4H) by airway eosinophils was determined by immunohistochemistry (IHC). Subsequently, peripheral blood eosinophils were activated and secreted LTB4 was quantified by enzyme immunoassay. Blood eosinophil LTA4H expression was determined by flow cytometry, qPCR, and IHC. LTB4 concentrations were elevated in BAL fluid from patients with severe asthma, including those with isolated eosinophilic inflammation, and these eosinophils displayed LTA4H via IHC. LTA4H expression by blood eosinophils was confirmed by flow cytometry, IHC, and qPCR. Robust LTB4 production by blood eosinophils was observed in response to some, but not all, stimuli. We demonstrated that eosinophils express LTA4H transcripts and protein, and can be stimulated to secrete LTB4. We speculate that in many patients with asthma, eosinophil-derived LTB4 is increased, and this may contribute to the efficacy of 5-LO inhibition.

Lung Lavage Granulocyte Patterns and Clinical Phenotypes in Children with Severe, Therapy-Resistant Asthma

BACKGROUND

Children with severe asthma have frequent exacerbations despite guidelines-based treatment with high-dose corticosteroids. The importance of refractory lung inflammation and infectious species as factors contributing to poorly controlled asthma in children is poorly understood.

OBJECTIVE

To identify prevalent granulocyte patterns and potential pathogens as targets for revised treatment, 126 children with severe asthma underwent clinically indicated bronchoscopy.

METHODS

Diagnostic tests included bronchoalveolar lavage (BAL) for cell count and differential, bacterial and viral studies, spirometry, and measurements of blood eosinophils, total IgE, and allergen-specific IgE. Outcomes were compared among 4 BAL granulocyte patterns.

RESULTS

Pauci-granulocytic BAL was the most prevalent granulocyte category (52%), and children with pauci-granulocytic BAL had less postbronchodilator airflow limitation, less blood eosinophilia, and less detection of BAL enterovirus compared with children with mixed granulocytic BAL. Children with isolated neutrophilia BAL were differentiated by less blood eosinophilia than those with mixed granulocytic BAL, but greater prevalence of potential bacterial pathogens compared with those with pauci-granulocytic BAL. Children with isolated eosinophilia BAL had features similar to those with mixed granulocytic BAL. Children with mixed granulocytic BAL took more maintenance prednisone, and had greater blood eosinophilia and allergen sensitization compared with those with pauci-granulocytic BAL.

CONCLUSIONS

In children with severe, therapy-resistant asthma, BAL granulocyte patterns and infectious species are associated with novel phenotypic features that can inform pathway-specific revisions in treatment. In 32% of children evaluated, BAL revealed corticosteroid-refractory eosinophilic infiltration amenable to anti-T_H2 biological therapies, and in 12%, a treatable bacterial pathogen.

Postnatal Innate Immune Development: From Birth to Adulthood

It is well established that adaptive immune responses are deficient in early life, contributing to increased mortality and morbidity. The developmental trajectories of different components of innate immunity are only recently being explored. Individual molecules, cells, or pathways of innate recognition and signaling, within different compartments/anatomical sites, demonstrate variable maturation patterns. Despite some discrepancies among published data, valuable information is emerging, showing that the developmental pattern of cytokine responses during early life is age and toll-like receptor specific, and may be modified by genetic and environmental factors. Interestingly, specific environmental exposures have been linked both to innate function modifications and the occurrence of chronic inflammatory disorders, such as respiratory allergies. As these conditions are on the rise, our knowledge on innate immune development and its modulating factors needs to be expanded. Improved understanding of the sequence of events associated with disease onset and persistence will lead toward meaningful interventions. This review describes the state-of-the-art on normal postnatal innate immune ontogeny and highlights research areas that are currently explored or should be further addressed.

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.

The effect of lead acetate on oxidative stress and antioxidant status in rat bronchoalveolar lavage fluid and lung tissue

Despite the wide spread of lead environmental pollution, the effect of this heavy metal on respiratory disease was not shown yet. In respect to increased oxidative stress is an important mechanism in the pathogenesis of respiratory disease, the present study was designed to examine the association between lead toxicity and lung disease via measuring oxidative stress biomarkers in bronchoalveolar lavage fluid (BALF) and lung tissue of rat. For this aim, 32 rats were divided into the following groups of eight animals each: control, three lead tested (received lead acetate in the drinking water for a period of 14 d at concentrations of 250, 500 and 1000 ppm) groups. At the end of the 2 week period, malondialdehyde (MDA), nitric oxide (NO) and reduced glutathione (GSH) contents were measured to assess free radical activity in the BALF and lung tissue. Superoxide dismutase (SOD) was also determined. A significant dose-dependent increase in the BALF supernatant and lung homogenate levels of MDA and NO with decrease GSH level and SOD activity were observed in the lead-treated groups compared with the control group (p < 0.05). Thus, lead acetate may be contributed to respiratory disorders via increased oxidative stress.

Does airway allergic inflammation pre-exist before late onset wheeze in children?

Epidemiological studies show that some children develop wheezing after 3 yr of age which tends to persist. It is unknown how this starts or whether there is a period of asymptomatic inflammation. The aim of this study is to determine whether lower airway allergic inflammation pre-exists in late onset childhood wheeze (LOCW). Follow-up study of children below 5 yr who had a non-bronchoscopic bronchoalveolar lavage (BAL) performed during elective surgery. The children had acted as normal controls. A modified ISAAC questionnaire was sent out at least 7 yr following the initial BAL, and this was used to ascertain whether any children had subsequently developed wheezing or other atopic disease (eczema, allergic rhinitis). Cellular and cytokine data from the original BAL were compared between those who never wheezed (NW) and those who had developed LOCW. Eighty-one normal non-asthmatic children were recruited with a median age of 3.2. Of the 65 children contactable, 9 (16.7%) had developed wheeze, 11 (18.5%) developed eczema and 14 (22.2%) developed hay fever. In five patients, wheeze symptoms developed mean 3.3-yr (range: 2-5 yr) post-BAL. Serum IgE and blood eosinophils were not different in the LOCW and NW, although the blood white cell count was lower in the LOCW group. The median BAL eosinophil % was significantly increased in the patients with LOCW (1.55%, IQR: 0.33 to 3.92) compared to the children who never wheezed, NW (0.1, IQR: 0.0 to 0.3, p = 0.01). No differences were detected for other cell types. There were no significant differences in BAL cytokine concentrations between children with LOCW and NW children. Before late onset childhood wheezing developed, we found evidence of elevated eosinophils in the airways. These data suggest pre-existent airways inflammation in childhood asthma some years before clinical presentation.

Respiratory viral infection in lower airways of asymptomatic children

Aim:  The aim of this study was to determine if asthmatic children have viruses more commonly detected in lower airways during asymptomatic periods than normal children.

Methods:  Fifty‐five asymptomatic children attending elective surgical procedures (14 with stable asthma, 41 normal controls) underwent non‐bronchoscopic bronchoalveolar lavage. Differential cell count and PCR for 13 common viruses were performed.

Results:  Nineteen (35%) children were positive for at least one virus, with adenovirus being most common. No differences in the proportion of viruses detected were seen between asthmatic and normal ‘control’ children. Viruses other than adenovirus were associated with higher neutrophil counts, suggesting that they caused an inflammatory response in both asthmatics and controls (median BAL neutrophil count, 6.9% for virus detected vs. 1.5% for virus not detected, p = 0.03).

Conclusions:  Over one‐third of asymptomatic children have a detectable virus (most commonly adenovirus) in the lower airway; however, this was not more common in asthmatics. Viruses other than adenovirus were associated with elevated neutrophils suggesting that viral infection can be present during relatively asymptomatic periods in asthmatic children.

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.

Proteomic Analysis of Two Non-Bronchoscopic Methods of Sampling the Lungs of Patients with the Acute Respiratory Distress Syndrome (ARDS)

Objective

The collection of lung fluid using a suction catheter (s-Cath) and non-bronchoscopic bronchoalveolar lavage (mini-BAL) are two minimally invasive methods of sampling the distal airspaces in patients with the acute respiratory distress syndrome (ARDS). The objective of this study was to determine the similarity of the lung fluid samples recovered by these methods using proteomic analysis.

Methods

Distal lung fluid samples were collected from seven mechanically ventilated patients with ARDS using both s-Cath and mini-BAL in each patient and compared using two-dimensional difference gel electrophoresis. Protein spots of interest were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Main Results

An average of 2,164 spots was detected in the s-Cath and mini-BAL samples. Of these, 68.4% of the protein spots were similar between the s-Cath and mini-BAL samples, 13.2% were increased in s-Cath compared to mini-BAL, and 18.4% were decreased in s-Cath compared to mini-BAL. For each of the seven subjects, overabundance analysis showed that the actual number of differentially expressed spots in the mini-BAL and s-Cath sample was more than the expected number if the samples were identical. There were nine proteins that were consistently differentially expressed between the mini-BAL and s-Cath samples. Of these nine proteins, five are abundantly found in neutrophils or airway epithelial cells, suggesting that the s-Cath may sample the bronchial airways to a greater extent than mini-BAL.

Conclusion

Proteomic analysis of mini-BAL and s-Cath samples shows for the first time that, although these two methods for sampling the lungs of critically ill patients are generally similar, the s-Cath method oversamples the distal airways compared to the mini-BAL method.

Immunology

The concept of forbidden foods that should not be eaten goes back to the Garden of Eden and apart from its religious meanings it may also have foreshadowed the concept of foods that can provoke adverse reactions. Thus we could say that allergic diseases have plagued mankind since the beginning of life on earth. The prophet Job was affected by a condition that following the rare symptoms described by the Holy Bible might be identified as a severe form of atopic dermatitis (AD). The earliest record of an apparently allergic reaction is 2621 B.C., when death from stinging insects was first described by hieroglyphics carved into the walls of the tomb of Pharaoh Menes depicting his death following the sting of a wasp. In 79 A.D., the death of the Roman admiral Pliny the Elder was ascribed to the SO₂-rich gases emanating from the eruption of Mount Vesuvius. Hippocrates (460–377 B.C.) was probably the first to describe how cow’s milk (CM) could cause gastric upset and hives, proposing dietetic measures including both treatment and prevention for CM allergy.

Severe respiratory syncytial virus bronchiolitis in infants is associated with reduced airway interferon gamma and substance P

Background

Severe human respiratory syncytial virus (hRSV) bronchiolitis in previously well infants may be due to differences in the innate immune response to hRSV infection. Aim: to determine if factors mediating proposed mechanisms for severe bronchiolitis differ with severity of disease.

Methodology/Principle Findings

197 infants admitted to hospital with hRSV bronchiolitis were recruited and grouped according to no oxygen requirement (n = 27), oxygen dependence (n = 114) or mechanical ventilation (n = 56). We collected clinical data, nasopharyngeal aspirate (NPA) and if ventilated bronchoalveolar lavage (BAL). Interferon-gamma (IFN-γ), substance P (SP), interleukin 9 (IL-9), urea and hRSV load, were measured in cell free supernatant from NPA and BAL. Multivariate analysis compared independent effects of clinical, virological and immunological variables upon disease severity. IFN-γ and SP concentrations were lower in NPA from infants who required oxygen or mechanical ventilation. Viral load and IL-9 concentrations were high but did not vary with severity of disease. Independent predictors of severe disease (in diminishing size of effect) were low weight on admission, low gestation at birth, low NPA IFN-γ and NPA SP. Nasal airway sampling appears to be a useful surrogate for distal airway sampling since concentrations of IFN-γ, SP, IL-9 and viral load in NPA correlate with the same in BAL.

Conclusions

Our data support two proposed mechanisms for severe hRSV disease; reduced local IFN-γ response and SP mediated inflammation. We found large amounts of hRSV and IL-9 in airways secretions from the upper and lower respiratory tract but could not associate these with disease severity.

Comparison of atopic and nonatopic children with chronic cough: bronchoalveolar lavage cell profile

Chronic cough is a common complaint in children and its relationship with asthma is controversial. The aim of the present study was to determine the pattern of airway inflammation in atopic and nonatopic children with chronic cough, and to investigate whether atopy is a predictive factor for eosinophilic inflammation in cough. Bronchoalveolar lavage (BAL; three aliquots of 1 ml/kg saline) was performed in the right middle lobe of 24 (11 atopic and 13 nonatopic) children with persistent cough (8 females, 16 males), mean age 4.7 years (range: 1-11). Atopy was defined as an elevated total serum IgE or a positive RAST test. Both atopic and nonatopic children with persistent cough had an increase in total cells/ml in BAL (atopic: median 39 x 10(4), range: 20-123; nonatopic: median 22 x 10(4), range: 17-132) compared to nonatopic controls (median 11 x 10(4), range 9-30). The increases were mainly in neutrophils (atopic: median 17%, range 2.5-88.5%; nonatopic: median 6%, range 1.0-55.0%) compared to controls (median 1.55%, range 0.5-7.0%; atopics vs. controls, P < 0.005). There were no significant increases in eosinophils, lymphocytes, epithelial cells, or mast cells. Eosinophils were elevated in only 5/11 atopic and none of the nonatopic children. The increased percentage of neutrophils in the BAL fluid of atopic and nonatopic children with persistent cough could be due to an underlying inflammatory process driving the cough, or even conceivably, due to the effect of coughing itself. In this highly selected series, the absence of eosinophilic inflammation in the majority suggests that most would be predicted not to respond to inhaled corticosteroid therapy. This study underscores the need to be cautious about treating coughing children with inhaled corticosteroids, even in the context of a tertiary referral practice.

Airway inflammation in asymptomatic children with episodic wheeze

Airway pathologies have been comprehensively researched in adult asthma, but in children, the extent of airway inflammation associated with episodic wheeze, often diagnosed as asthma, has not been fully characterized. It is not clear whether persistent airway inflammation is present in the absence of wheezing symptoms, and there is controversy regarding the role of age and atopy. This study assessed cellular and cytokine markers of airway inflammation in asymptomatic children with a history of episodic wheeze. Children with a history of episodic wheeze and cough (study group) and nonasthmatic patients requiring elective surgery (control group) were recruited. All subjects in the study group had a history of significant episodic wheezing (>2 episodes per year), and used only as-needed beta-agonist treatment. Bronchoalveolar lavage (BAL) was obtained using bronchoscopic lavage (study group) and nonbronchoscopic lavage (control group). Differential cell counts of BAL and flow cytometry were performed to identify T-lymphocyte phenotypes, and intracellular cytokine profiles were measured after phorbol-12-myristate 13-acetate (PMA) stimulation of BAL fluid T-cells. Twenty-one children with a history of 2-12 episodes of wheeze per year and 21 nonasthmatic subjects without respiratory symptoms were recruited. Study and control subjects were matched for age (median age, 5 years) and demographic characteristics. Study subjects had higher IgE levels, but their measurements were still within normal range. No significant differences in BAL differential cell counts were noted, and in both groups, the majority of T-cells were CD3+ CD8+, with a median CD4:CD8 ratio of 0.6. There was no significant difference in T-cell expression of the activation markers HLA-DR and CD25 (IL-2 receptor), or in PMA-induced production of the intracellular cytokines IFN-gamma, IL-2, IL-4, IL-5, and IL-10. The results of this study suggest that significant T-cell-driven airway inflammation is absent in mild or nonatopic, asymptomatic children of this age group who have episodic wheeze. Our findings support asthma management guidelines that do not recommend long-term treatment of this group of patients with anti-inflammatory medications.

Role of nonbronchoscopic lavage for investigating alveolar inflammation and permeability in acute respiratory distress syndrome

OBJECTIVE

Nonbronchoscopic bronchoalveolar lavage is often used as an alternative to bronchoscopic bronchoalveolar lavage in the diagnosis of ventilator-associated pneumonia. We have previously reported an improved safety profile for nonbronchoscopic lavage in patients with lung injury, suggesting that this may be a better technique in this patient group. The objective of this study was to determine whether nonbronchoscopic lavage could be used as an alternative to bronchoscopic lavage for the assessment of alveolar permeability and inflammation in patients at risk for acute respiratory distress syndrome (ARDS) or with ARDS.

DESIGN

Prospective randomized crossover trial.

PATIENTS

Intubated patients with ARDS or at risk of ARDS.

INTERVENTIONS

Bronchoscopic and nonbronchoscopic lavage in the same patient, 15 mins apart.

MEASUREMENTS AND MAIN RESULTS

Twenty-one patients with ARDS and 20 patients at risk of ARDS were recruited and underwent nonbronchoscopic and bronchoscopic lavage in randomized order. Despite similar volumes of lavage fluid, nonbronchoscopic lavage had fewer cells and an increased ratio of bronchial epithelial cells to macrophages. Although average concentrations of myeloperoxidase and total protein, the protein permeability index, and the epithelial-lining fluid volume were similar with the two techniques and demonstrated moderate linear associations, Bland and Altman analysis revealed poor comparability, with substantial side-to-side variability and wide 95% limits of agreement. Furthermore, unlike bronchoscopic lavage, nonbronchoscopic lavage was unable to differentiate between patients with ARDS and those at risk of ARDS.

CONCLUSIONS

Nonbronchoscopic lavage is not comparable to bronchoscopic lavage and as such cannot be used as an alternative to bronchoscopic lavage for assessing alveolar inflammation in patients with ARDS.

The wheezy infant -- immunological and molecular considerations

Most of the data on the pathogenesis of asthma is based on information obtained through bronchial biopsies and bronchoalveolar lavage in adults and young adults. Ethical considerations linked to the invasive nature of airway endoscopy have limited the studies on the pathophysiology of asthma in infancy and early childhood. Although there is evidence that an asthma-like inflammation, with increased inflammatory cells and thickening of the lung basement membrane, may be present also at a very early age, clinical and epidemiologic studies suggest that asthma manifestations in preschool children may significantly differ from those observed in older subjects. In western countries, the vast majority of infants and young children has episodic (or intermittent) asthma, and the exacerbations generally defined "wheezing episodes" occur more frequently with a seasonal pattern being usually related to acute viral infections. There is strong epidemiological evidence that approximately 2/3 of all children who wheeze because of viral infections in early life (and are not atopic) have a transient condition that tends to disappear during early school years. All respiratory viruses may be implicated in the wheezing episodes, the principal being respiratory syncytial virus (RSV) and, with a lower frequency, adenovirus and parainfluenza viruses during the first 3 years of life, and rhinoviruses after that age. Infants and preschool children have on average 6-8 "colds" per year, but the illness tends to be limited to the upper respiratory tract alone in a considerable proportion of individuals, without causing symptomatic involvement of the lower respiratory tract. The variety of factors determining the different outcomes are only partially known, but complex interactions between the intrinsic pathogenicity of the virus and host factors, including the socio-economic conditions of the family, are central to define the type of manifestations and the severity of the process.

Interleukin-4 and interleukin-4 soluble receptor alpha levels in bronchoalveolar lavage from children with asthma

BACKGROUND

In asthma there is increased expression of the Th2-type cytokine interleukin-4 (IL-4). IL-4 is important in immunoglobulin isotype switching to immunoglobulin E and adhesion of eosinophils to endothelium.

OBJECTIVE

We hypothesized that levels of IL-4 in bronchoalveolar lavage (BAL) fluid would be increased in stable, atopic asthmatic children compared with controls and that levels of its physiologic inhibitor IL-4 soluble receptor alpha (IL-4sR alpha) would be correspondingly decreased.

METHODS

One hundred sixteen children attending a children's hospital for elective surgery were recruited. A nonbronchoscopic BAL was performed, and IL-4 and IL-4sR alpha were measured in the BAL supernatants.

RESULTS

There was no significant difference in IL-4 concentrations between atopic asthmatic children, atopic normal controls, and nonatopic normal controls [0.13 pg/mL (0.13 to 0.87) vs 0.13 pg/mL (0.13 to 0.41) vs 0.13 pg/mL (0.13 to 0.5), P = 0.65]. IL-4sR alpha levels were significantly increased in asthmatic patients compared with atopic controls [6.4 pg/mL (5.0 to 25.5) vs 5.0 pg/mL (5.0 to 9.9), P = 0.018], but not when compared with the nonatopic controls [5.2 pg/mL (5.0 to 10.6), P = 0.19].

CONCLUSIONS

Contrary to expectation, IL-4sR alpha levels are increased in BAL from stable asthmatic children compared with nonatopic controls, and we speculate that IL-4sR alpha is released by inflammatory cells in the airways to limit the proinflammatory effects of IL-4.

Neutrophils in asthma pathophysiology

Although the role of eosinophils, mast cells, and T cells in asthma has long been recognized, several reports suggest that neutrophils may also be involved. In most studies of people with mild asthma, neutrophil numbers in the airways are not different from controls. However, in severe asthma, including asthma deaths, neutrophils are usually raised. Furthermore, most pediatric studies suggest that neutrophils are raised in some children, in particular in the young or infantile wheeze group. Measurements of inflammatory mediators in the airways of asthmatic subjects suggest that neutrophils are activated.

Antioxidants and oxidative stress in BAL fluid of atopic asthmatic children

Earlier studies in adults have indicated that increased oxidative stress may occur in the blood and airways of asthmatic subjects. Therefore the aim of this study was to compare the concentrations of antioxidants and protein carbonyls in bronchoalveolar lavage fluid of clinically stable atopic asthmatic children (AA, n = 78) with our recently published reference intervals for nonasthmatic children (C, n = 124). Additionally, lipid peroxidation products (malondialdehyde) in bronchoalveolar lavage fluid and several antioxidants in plasma were determined. Bronchoalveolar lavage concentrations (median and interquartile range) of ascorbate [AA: 0.433 (0.294-0.678) versus C: 0.418 (0.253-0.646) micromol/L], urate [AA: 0.585 (0.412-0.996) versus C: 0.511 (0.372-0.687) micromol/L], alpha-tocopherol [AA: 0.025 (0.014-0.031) versus C: 0.017 (0.017-0.260) micromol/L], and oxidized proteins as reflected by protein carbonyls [AA: 1.222 (0.970-1.635) versus C: 1.243 (0.813-1.685) nmol/mg protein] were similar in both groups (p > 0.05 in all cases). The concentration of protein carbonyls correlated significantly with the number of eosinophils, mast cells, and macrophages in AA children only. Concentrations of oxidized proteins and lipid peroxidation products (malondialdehyde) correlated significantly in AA children (r = 0.614, n = 11, p = 0.044). Serum concentrations of ascorbate, urate, retinol, alpha-tocopherol, beta-carotene, and lycopene were similar in both groups whereas alpha-carotene was significantly reduced in asthmatics. Overall, increased bronchoalveolar lavage eosinophils indicate ongoing airway inflammation, which may increase oxidatively modified proteins as reflected by increased protein carbonyl concentrations.

Suppression of autologous peripheral blood mononuclear cell proliferation by alveolar macrophages from young infants

Maintenance of lung homeostasis involves a complex interaction between T lymphocytes and alveolar macrophages (AM), in which AM suppress pulmonary T cell proliferation to antigenic stimuli. To assess whether AM-mediated suppression is attenuated in healthy young infants, AM and peripheral blood mononuclear cells (PBMC) were sampled prior to elective surgery. Children were divided into <4 months of age (Group I) and >4 months (Group II). Autologous PBMC and AM were co-cultured in vitro with phytohaemaglutinin (PHA) at AM : PBMC ratios ranging from 2:1 to 1 : 5. Methyl-tritiated thymidine was added after 48 h and uptake determined at 72 h. Percentage suppression or enhancement of PBMC proliferation by AM was determined relative to proliferation of PBMC with PHA. To determine the role of soluble factors of suppression, cell-free supernatants from paediatric AM and PBMC co-cultures were added to PHA-stimulated adult PBMC. The median age was 3 months for Group I (n = 9) and 7 years 2 months (n = 13) for Group II. Percentage suppression of PBMC proliferation was attenuated in Group I (versus Group II) at AM : PBMC ratios of 2:1 (median 78 versus 92, P< 0 x 05) and 1 : 1 (45 versus 87, P< 0 x 01). Cell-free supernatants from Groups I and II suppressed proliferation of adult PBMC, but there was no difference in suppression between the age groups. We conclude that suppression of autologous PHA-stimulated PBMC proliferation by AM is attenuated in young infants, and this immaturity is not explained by reduced release of soluble factors.

Antioxidants and protein carbonyls in bronchoalveolar lavage fluid of children: normal data

Antioxidant-oxidant imbalances in bronchoalveolar lavage fluid (BAL) are thought to contribute to oxidative stress in respiratory disease. However, normal reference ranges for BAL antioxidants and oxidized proteins in children are not available. In this study, we recruited 124 children attending for elective surgery for a noninflammatory condition; 83 were nonasthmatic, nonatopic (N) and 41 were nonasthmatic, atopic (NA). A nonbronchoscopic lavage was performed and ascorbate, uric acid, alpha-tocopherol, and protein carbonyl (as a measure of oxidative damage) concentrations were determined in BAL fluid. The 95% reference range was 0.112-1.897 micromol/L for ascorbate, 0.149-2.163 micromol/L for urate, 0.0029-0.066 micromol/L for alpha-tocopherol, and 0.280-4.529 nmol/mg for protein carbonyls in BAL fluid. Age, gender, and exposure to environmental tobacco smoke did not affect the concentration of ascorbate, urate, alpha-tocopherol, or protein carbonyls. However, in multiple linear regression analyses, the type of home heating (glass-fronted fires or oil-fired central heating) was found to influence ascorbate and urate concentrations in the BAL fluid (ss-coefficient for ascorbate: 0.445, p = 0.031; for urate: 0.114, p = 0.001). There was no significant difference between the N and NA group in BAL fluid concentrations of ascorbate, urate, or protein carbonyls. The alpha-tocopherol concentration was significantly increased in the NA group (p = 0.037). Uric acid and alpha-tocopherol concentrations in BAL fluid and serum were not correlated. Intriguingly, serum and BAL ascorbate concentrations were significantly correlated (r = 0.297, p = 0.018, n = 63), which may offer an explanation for why supplementing the diet with vitamin C can improve asthma symptoms. Further studies will investigate the role of BAL antioxidant concentrations in children with inflammatory respiratory diseases.

Issues in understanding childhood asthma

Asthma and related allergic disorders in childhood have increased considerably in prevalence over the last few decades. During the same period of increasing morbidity from childhood asthma in the community, there have been dramatic advances in understanding of the basic immunopathologic features of the disease and consequently the development of a far more rational approach to its treatment. The immunopathologic condition of eosinophil-mediated airway inflammation is established very early in the evolution of asthma in childhood. It may even antedate the onset of symptoms. The present state of the art dictates that early intervention with potent therapies cannot be justified on the basis of symptoms alone and may in any case have no influence on the natural history of the condition. This means that current cautious therapeutic guidelines should continue to be followed. However, with the development of more accurate markers predicting ongoing disease, it will be possible to evaluate a whole range of early interventions in the future. Much evidence, though indirect, points to the possibility that the only true prophylaxis that will affect the natural history of asthma will need to be commenced before clinical features are manifest.

Serum eosinophilic cationic protein and blood eosinophil counts for the prediction of the presence of airways inflammation in children with wheezing

BACKGROUND

Serum eosinophilic cationic protein (ECP) concentrations may be useful noninvasive markers of airways inflammation in atopic asthma. However, the usefulness of serum ECP measurement for the prediction of airways inflammation in children with a history of wheezing is unknown.

OBJECTIVE

To determine the test accuracy of serum ECP and blood eosinophil percentage as noninvasive markers of eosinophilic airways inflammation.

METHODS

Bronchoalveolar lavage (BAL) fluid and peripheral blood samples for eosinophil percentages and serum ECP were obtained from children undergoing elective surgery and who gave a history of wheezing in the previous year. Sensitivity, specificity and likelihood ratios (LH) and the area under the curve (AUC) for the receiver operator characteristic (ROC) curve were calculated for each blood marker for the prediction of airways inflammation defined by a BAL eosinophil percentage > 0.86. Data were analysed on the basis of how recently symptoms had occurred.

RESULTS

Seventy-seven children (median age 6.75 years) were studied. An AUC of 0.75 (log serum ECP concentration) and 0.76 (log blood eosinophil percentage) was obtained for predicting airways inflammation. A serum ECP > 13 microg/L yielded a LH of 4.4, whereas using a cutoff blood eosinophils > 4% yielded a LH of 1.9, for the prediction of elevated eosinophils in BAL. Serum ECP and eosinophil percentages in BAL and blood were lowest (not statistically significant) when last symptoms had occurred more than 12 weeks previously.

CONCLUSIONS

Serum ECP and blood eosinophil percentages are useful markers for predicting eosinophilic airways inflammation in wheezing children.

Bronchoalveolar lavage fluid cellularity and soluble intercellular adhesion molecule-1 in children with colds

Viral colds are an important cause of respiratory symptoms in normal children. Studies in adults suggest that inflammation in the lower respiratory tract is associated with viral colds, but there are no data regarding inflammation and viral infection in the lower airway of normal children with colds. We, therefore, studied the lower airway of two groups of children: Group I, those with active coryzal symptoms and a respiratory virus isolated from bronchoalveolar lavage fluid (BALF); and Group II: asymptomatic children who had had a clinical cold within the previous 2 weeks and no respiratory virus in BALF. Both groups were compared to age- and weight-matched normal noninfected controls, who had had no coryzal symptoms for at least 8 weeks. Viruses isolated from BALF of Group I (n = 7) were: respiratory syncytial virus (n = 2), rhinovirus (n = 3), parainfluenza I (n = 1), and echovirus 11 (n = 1). Compared to normal controls, Group I had an increased BALF lymphocyte and neutrophil differential count (P < 0.05), a concomitant depressed alveolar macrophage differential count (P < 0.05), and increased BALF concentrations of soluble intercellular adhesion molecule-1 (sICAM-1) (P < 0.05, n = 6), total protein (P < 0.05, n = 6) and albumin (P < 0.05, n = 7). Similar changes were seen in Group II (n = 22), with an increased BALF neutrophil (P < 0.05) and lymphocyte (P < 0.01) differential count, and increased concentrations of sICAM-1 (P < 0.01, n = 15), total protein (P < 0.0001, n = 9) and albumin (P = 0.05, n = 17). Our results suggest that inflammation and viral infection in the lower airway are present during active colds, and that inflammation is also present during the convalescent period.

Is childhood asthma an inflammatory disease?

There is now extensive evidence that asthma results from inflammation in large and small airways, and that the degree of inflammation reflects the clinical severity of the disease. Most of this evidence, however, has come from studies in adult patients. Evidence in children comes largely from indirect studies such as measurements of peripheral blood cells and inflammatory markers, rather than from direct bronchoscopic examination. Studies in adults show that inflammation in asthma is characterized by eosinophilia, epithelial damage, and bronchial hyperresponsiveness, and that activation of allergen-specific T cells plays an important role in orchestrating the inflammatory process. In children, indirect evidence of inflammation comes from the observation that anti-inflammatory agents such as inhaled corticosteroids improve symptoms and bronchial hyperresponsiveness, reduce the number of asthma exacerbations, and limit the progressive decline in lung function. Further evidence comes from measurements of nitric oxide and hydrogen peroxide (potential inflammatory markers) in exhaled air, and of inflammatory mediators in plasma and urine. As in adults, there is evidence that lymphocytes play an important role in orchestrating the inflammatory process. The immunologic profile appears to shift from a Th1-type cytokine profile to an allergen-related Th2-type profile prior to birth. Such a Th2 predominance constitutes a risk factor for the subsequent development of bronchial hyperresponsiveness and asthma in response to allergen.

Bronchoalveolar cell profiles in children with asthma, infantile wheeze, chronic cough, or cystic fibrosis

Differential cell counts of bronchoalveolar lavage (BAL) have been reported in normal children but few data on cellular profiles in bronchial diseases in childhood are available. We determined the BAL cell profiles of 72 children divided into 5 groups: asthma (n = 14), chronic cough (n = 12), infantile wheeze (n = 26), cystic fibrosis (n = 10), and control (n = 10). The highest total cell, eosinophil, and neutrophil counts were found in children with cystic fibrosis. The cell profile of children with chronic cough was similar to that of control children. Asthma and infantile wheeze were characterized by a high median ratio of eosinophils (3%) and neutrophils (12%), respectively. In both diseases, epithelial shedding was suggested by an elevated epithelial cell count, 13.5 and 12%, respectively. Lymphocyte subset analysis showed a higher proportion of CD8 cells (58 versus 40%) and therefore a lower CD4/CD8 ratio (0.266 versus 0. 455) in children with asthma compared with infantile wheezers (p = 0. 02). Irrespective of the presence or absence of radiological abnormalities, a proportion of neutrophils > 10%, was found in one-third of the children with asthma and in half of the infantile wheezers, and was related to symptom severity. We suggest that neutrophil-mediated inflammation, with or without bacterial infection, may contribute to symptoms of asthma in childhood. Chronic cough, however, is not associated with the cell profiles suggestive of asthma and in isolation should not be treated with prophylactic antiasthma drugs.

Inflammatory mediators in bronchoalveolar lavage samples from children with and without asthma

BACKGROUND

We investigated whether eosinophils and mast cells, found in the airways of children with wheeze, were activated during relatively asymptomatic periods.

METHODS

A nonbronchoscopic bronchoalveolar lavage (BAL) procedure was performed on children presenting for an elective surgical procedure. Eosinophil-derived (eosinophil cationic protein, ECP) and mast cell-derived (histamine/tryptase) mediator concentrations were measured in the BAL fluid. A detailed history and serum immunoglobulin E were used to classify the children into four groups: atopic with and without asthma, viral-associated wheeze and normal controls.

RESULTS

The ECP concentrations in BAL from atopic asthmatic subjects were significantly higher than those measured in BAL from normal controls (P < 0.01), no other groups differed significantly. Histamine concentrations were elevated in both the atopic asthmatic and viral-associated wheeze groups compared with controls (P < 0.02) and additionally higher concentrations were obtained in atopics with asthma compared with atopics without asthma (P < 0.03). Tryptase concentrations did not differ between groups, although the tryptase and histamine concentrations correlated significantly (r = 0.78, P < 0.0001).

CONCLUSIONS

Elevated histamine concentrations were found in children with wheeze regardless of the aetiology, whereas ECP was only elevated in those asthmatics with atopy. This suggests that even in relatively quiescent periods, there is some on going activation of airway eosinophils in children with atopic asthma.

Inflammatory mechanisms in childhood asthma

There is now a reasonable body of data that would suggest that the immunopathology of asthma is similar, if not identical, in childhood asthmatics compared with adult asthmatics. Indeed, we now have evidence that much of the immunopathology is established within the airways of asthmatics very early after the onset of symptoms and, given the lack of correlation with duration of symptoms, may even antedate the first manifestations. There are, however, some differences with neutrophil recruitment being somewhat more prominent than has been recorded from adult observations. The utility of any inflammation parameter in identifying the real future asthmatics has yet to be studied in sufficient detail to define sensitivity, specificity and predictive value. Such studies will be an essential prerequisite to establishing very early intervention strategies, particularly if these involve the use of inhaled and/or oral corticosteroid.

Glutathione and neonatal lung disease

Glutathione (GSH) was measured using HPLC-electrochemical detection in bronchoalveolar lavage fluid from 28 neonates for up to 21 days after birth. GSH levels varied from 0.1-11.2 mumol l-1 (with a geometric mean concentration of 1.3 mumol l-1). GSH in epithelial lining fluid was estimated using the urea dilution method at 15.0 mumol l-1 (range 0.5-196 mumol l-1), which is significantly lower than observed in adult subjects. There was an L shaped relationship between GSH and the two markers of oxygen therapy, oxygen index and FiO2. The lowest GSH levels were associated with the group of infants with the most severe airways problems who required high oxygen.

Bronchoalveolar lavage findings suggest two different forms of childhood asthma

BACKGROUND

It seems plausible that children with atopy and persistent asthma symptoms will, like their adult counterparts, have chronic airways inflammation. However, many young children with no other atopic features have episodic wheezing that is triggered solely by viral respiratory infections. Little is known as to whether airways inflammation occurs in these two asthma patterns during relatively asymptomatic periods.

METHODS

Using a non-bronchoscopic bronchoalveolar lavage (BAL) procedure on children presenting for an elective surgical procedure, this study has investigated the cellular constituents of BAL fluid in children with a history of atopic asthma (AA) non-asthmatic atopic children (NAA) or viral associated wheeze (VAW).

RESULTS

A total of 95 children was studied: 52 with atopic asthma (8.0 years, range 1.1-15.3, 36 male), 23 with non-asthmatic atopy (median age 8.3 years, range 1.7-13.6, 11 male) and 20 with VAW (3.1 years, range 1.0-8.2, 13 male). No complications were observed during the lavage procedure and no adverse events were noted post-operatively. Total lavage fluid recovered was similar in all groups and the total cell numbers were higher in the VAW group. Eosinophil (P < or = 0.005) and mast cell (P < or = 0.05) numbers were significantly elevated in the group with atopic asthma.

CONCLUSIONS

During relatively asymptomatic periods there is on-going airways inflammation, as demonstrated by eosinophil and mast cell recruitment, in children with asthma and atopy but not in children with viral associated wheeze or atopy alone. This strongly suggests that there are different underlying pathophysiological mechanisms in these two groups of children who wheeze.