Hui-Leng Tan

The Th17 pathway in cystic fibrosis lung disease.

RATIONALE Cystic fibrosis (CF) is characterized by bronchoalveolar neutrophilia and submucosal lymphocytosis. We hypothesized that Th17 lymphocytes are part of this submucosal infiltrate. OBJECTIVES Quantification and phenotyping of the lymphocytic infiltrate in the bronchial submucosa of patients with CF (n = 53, of which 20 were newly diagnosed), non-CF bronchiectasis (n = 17), and healthy control subjects (n = 13). METHODS We measured IL-17 levels in bronchoalveolar lavage and CD4(+), CD8(+), and IL-17(+) cell counts in endobronchial biopsies. Correlations were made with infection status and other inflammatory markers. Potential cellular sources of IL-17 were determined by double staining. MEASUREMENTS AND MAIN RESULTS IL-17(+) cell counts (median [interquartile range] cells/mm(2)) were significantly higher in patients with established CF (205 [115-551]) and non-CF bronchiectasis (245 [183-436]) than in control subjects (53 [12-82]) (P < 0.01 for both). Patients with newly diagnosed CF had intermediate counts (171 [91-252]). IL-17-positive CD4(+) T cells, γδT cells, natural killer T cells, and neutrophils were identified. Bronchoalveolar lavage IL-17 levels (pg/ml) were highest in established CF (14.6 [2.2-38.4]), low in newly diagnosed CF and control subjects (1.7 [1.7-1.74]; 1.7 [1.7-3]), and intermediate in non-CF bronchiectasis (9.1 [1.7-34] pg/ml) (Kruskal-Wallis P = 0.001). There was a significant correlation between IL-17 and neutrophil counts (P < 0.001, R = 0.6) as well as IL-4 (P < 0.001, R = 0.84). CONCLUSIONS Th17 lymphocytes are present in the airway submucosa in CF, even in a young, newly diagnosed group. Other IL-17(+) cells include neutrophils, γδ T cells, and natural killer T cells.

High Rhinovirus Burden in Lower Airways of Children With Cystic Fibrosis

BACKGROUND Rhinovirus (RV)-induced pulmonary exacerbations are common in cystic fibrosis (CF) and have been associated with impaired virus clearance by the CF airway epithelium in vitro. Here, we assess in vivo the association of RV prevalence and load with antiviral defense mechanisms, airway inflammation, and lung function parameters in children with CF compared with a control group and children with other chronic respiratory diseases. METHODS RV presence and load were measured by real-time reverse transcription-polymerase chain reaction in BAL samples and were related to antiviral and inflammatory mediators measured in BAL and to clinical parameters. RESULTS BAL samples were obtained from children with CF (n = 195), non-CF bronchiectasis (n = 40), or asthma (n = 29) and from a control group (n = 35) at a median (interquartile range [IQR]) age of 8.2 (4.0-11.7) years. RV was detected in 73 samples (24.4%). RV prevalence was similar among groups. RV load (median [IQR] x 10(3) copies/mL) was higher in children with CF (143.0 [13.1-1530.0]), especially during pulmonary exacerbations, compared with children with asthma (3.0 [1.3-25.8], P = .006) and the control group (0.5 [0.3-0.5], P < .001), but similar to patients with non-CF bronchiectasis (122.1 [2.7-4423.5], P = not significant). In children with CF, RV load was negatively associated with interferon (IFN)- b and IFN- l , IL-1ra levels, and FEV 1 , and positively with levels of the cytokines CXCL8 and CXCL10. CONCLUSIONS RV load in CF BAL is high, especially during exacerbated lung disease. Impaired production of antiviral mediators may lead to the high RV burden in the lower airways of children with CF. Whether high RV load is a cause or a consequence of inflammation needs further investigation in longitudinal studies.

Distinct patterns of inflammation in the airway lumen and bronchial mucosa of children with cystic fibrosis

Background Studies in cystic fibrosis (CF) generally focus on inflammation present in the airway lumen. Little is known about inflammation occurring in the airway wall, the site ultimately destroyed in end-stage disease. Objective To test the hypothesis that inflammatory patterns in the lumen do not reflect those in the airway wall of children with CF. Methods Bronchoalveolar lavage (BAL) fluid and endobronchial biopsies were obtained from 46 children with CF and 16 disease-free controls. BAL cell differential was assessed using May-Gruenwald-stained cytospins. Area profile counts of bronchial tissue immunopositive inflammatory cells were determined. Results BAL fluid from children with CF had a predominance of neutrophils compared with controls (median 810×103/ml vs 1×103/ml, p<0.0001). In contrast, subepithelial bronchial tissue from children with CF was characterised by a predominance of lymphocytes (median 961 vs 717 cells/mm2, p=0.014), of which 82% were (CD3) T lymphocytes. In chest exacerbations, BAL fluid from children with CF had more inflammatory cells of all types compared with those with stable disease whereas, in biopsies, only the numbers of lymphocytes and macrophages, but not of neutrophils, were higher. A positive culture of Pseudomonas aeruginosa was associated with higher numbers of T lymphocytes in subepithelial bronchial tissue (median 1174 vs 714 cells/mm2, p=0.029), but no changes were seen in BAL fluid. Cell counts in BAL fluid and biopsies were positively correlated with age but were unrelated to each other. Conclusion The inflammatory response in the CF airway is compartmentalised. In contrast to the neutrophil-dominated inflammation present in the airway lumen, the bronchial mucosa is characterised by the recruitment and accumulation of lymphocytes.

Long term non-invasive ventilation in children: impact on survival and transition to adult care.

Background The number of children receiving domiciliary ventilatory support has grown over the last few decades driven largely by the introduction and widening applications of non-invasive ventilation. Ventilatory support may be used with the intention of increasing survival, or to facilitate discharge home and/or to palliate symptoms. However, the outcome of this intervention and the number of children transitioning to adult care as a consequence of longer survival is not yet clear. Methods In this retrospective cohort study, we analysed the outcome in children (<17 years) started on home NIV at Royal Brompton Hospital over an 18 year period 1993-2011. The aim was to establish for different diagnostic groups: survival rate, likelihood of early death depending on diagnosis or discontinuation of ventilation, and the proportion transitioning to adult care. Results 496 children were commenced on home non invasive ventilation; follow-up data were available in 449 (91%). Fifty six per cent (n=254) had neuromuscular disease. Ventilation was started at a median age (IQR) 10 (3-15) years. Thirteen percent (n=59) were less than 1 year old. Forty percent (n=181) have transitioned to adult care. Twenty four percent (n=109) of patients have died, and nine percent (n=42) were able to discontinue ventilatory support. Conclusion Long term ventilation is associated with an increase in survival in a range of conditions leading to ventilatory failure in children, resulting in increasing numbers surviving to adulthood. This has significant implications for planning transition and adult care facilities.

Update on paediatric obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is one of the most common causes of sleep-disordered breathing (SDB) in children. It is associated with significant morbidity, potentially impacting on long-term neurocognitive and behavioural development, as well as cardiovascular outcomes and metabolic homeostasis. The low grade systemic inflammation and increased oxidative stress seen in this condition are believed to underpin the development of these OSA-related morbidities. The significant variance in degree of end organ morbidity in patients with the same severity of OSA highlights the importance of the interplay of genetic and environmental factors in determining the overall OSA phenotype. This review seeks to summarize the current understanding of the aetiology and mechanisms underlying OSA, its risk factors, diagnosis and treatment.

Sleep disordered breathing and ventilatory support in children with Down syndrome

Obstructive sleep apnoea (OSAS) in children with Down syndrome (DS) is now well recognized, but other forms of sleep disordered breathing (SDB) in this population are less well described. Anecdotally, respiratory support for SDB treatment in this population is not easily tolerated. We aimed to characterize the types of SDB in children with DS referred to a tertiary respiratory center and to assess the effectiveness and adherence to respiratory support.

Detection of early nocturnal hypoventilation in neuromuscular disorders

Objective Nocturnal hypoventilation (NH) is a complication of respiratory involvement in neuromuscular disorders (NMD) that can evolve into symptomatic daytime hypercapnia if not treated proactively with non-invasive ventilation. This study aimed to assess whether NH can be detected in the absence of other signs of nocturnal altered gas exchange. Methods We performed nocturnal transcutaneous coupled (tc) pCO2/SpO2 monitoring in 46 consecutive cases of paediatric-onset NMD with a restrictive respiratory defect (forced vital capacity < 60%). Nocturnal hypoventilation was defined as tcPCO2 > 50 mmHg for > 25% of recorded time, and hypoxemia as tcSpO2 < 88% for > 5 minutes. Daytime symptoms and bicarbonate were recorded after overnight monitoring. Results Twenty-nine of 46 consecutive patients showed NH. Twenty-three patients did not have nocturnal hypoxemia and 18 were clinically asymptomatic. In 20 patients, PaCO2 in daytime blood samples was normal. Finally, 13/29 patients with NH had isolated nocturnal hypercapnia without nocturnal hypoxia, clinical NH symptoms, or daytime hypercapnia. Conclusions Paediatric patients with NMD can develop NH in the absence of clinical symptoms or significant nocturnal desaturation. Therefore, monitoring of NH should be included among nocturnal respiratory assessments of these patients as an additional tool to determine when to commence non-invasive ventilation.

Sleep disordered breathing in children with primary ciliary dyskinesia (PCD)

PCD patients may be prone to sleep disordered breathing (SDB), due to upper and lower airway disease. We hypothesized that SDB would be associated with more severe PCD, and aimed to determine whether particular subgroups would be at higher risk. We investigated 84 children with confirmed PCD (48 girls, age 10.1 ± 4.4 years) for SDB and PCD severity. Patients underwent overnight attended polysomnography (n=62) or polygraphy (n=22) self-ventilating in room air, HRCT, spirometry, and lung clearance index (LCI). Results are summarized in Table 1. Whilst the majority of patients had flow limitation on the nasal pressure transducer, suggestive of increased upper airways resistance, only 1 patient had evidence of mild OSA with an obstructive apnoea-hypopnoea-index (OAHI) of 2/ hours total sleep time (hTST). 23 patients (27%) had a mildly raised AHI (1.5 [1.1-2.1], median [IQR]) / hTST mainly due to central apnoeas. Transcutaneous CO2 was normal in all. 7 had mean SpO2 In summary, we found only mild SDB in children with PCD. We could not delineate a high risk group for SDB based on parameters of lung disease. We conclude that routine screening for SDB is not indicated in children with PCD.

P71 Reduced airway beta-defensin 2 levels in children with cystic fibrosis and vitamin D-deficiency

Vitamin D (vD) levels have been reported to correlate with (a) lung function in healthy populations and (b) disease severity in pulmonary TB, COPD and asthma. The proposed mechanism, supported by in vitro studies, relates to vD response elements in the promoter regions of genes encoding molecules involved in innate immunity such as defensins and cathelicidin (LL-37). As patients with CF are at risk of fat and fat-soluble vitamin malabsorption, we sought to explore this relationship in a cohort of CF children. Frozen serum and bronchoalveolar (BAL) fluid samples, which had been donated for research at the time of a clinically-indicated bronchoscopy were available from 49 children with CF. Mean age at the time of the procedure was 6.8 years (range 0.03–15.99). 44 (90%) were biochemically pancreatic insufficient and were prescribed pancreatic enzyme supplementation and fat-soluble mulitvitamins. Serum 25OH vD3 was measured using HPLC and mass spectrometry. BALF human beta defensin-2 (hbD2) and LL-37 were quantified using ELISA. vD deficiency was defined as <20 ng/ml based on internationally-accepted criteria. Deficient and sufficient groups were compared with Mann–Whitney tests and Spearmans correlations were performed. 16 (33%) children were vD-deficient (including two of the five pancreatic sufficient patients); they did not differ in age from the vD sufficient group. BALF hbD2 was significantly lower than in the vD sufficient group (median (range) 185.3 (7.8–615.7) pg/ml vs 385.5 (7.8–1002) pg/ml; p<0.05). In contrast, no relationship was observed between serum vD and BAL LL-37. As this molecule is known to be highly sensitive to proteolysis, we considered the possibility that degradation could be masking an effect of vD on LL-37 expression. However, no inverse relationship with neutrophil elastase or MMP-9 was found to support this hypothesis. Children with CF are at risk of low vD levels even if they are clinically pancreatic sufficient or if vitamin supplements are being prescribed. vD deficiency is associated with low levels of antimicrobial defence molecules within the airway. Whether this is a clinically important phenomenon leading to susceptibility to infection and increased inflammation will be the focus of future work.