Genome-wide association study to identify genetic determinants of severe asthma.

BACKGROUND: The genetic basis for developing asthma has been extensively studied. However, association studies to date have mostly focused on mild to moderate disease and genetic risk factors for severe asthma remain unclear. OBJECTIVE: To identify common genetic variants affecting susceptibility to severe asthma. METHODS: A genome-wide association study was undertaken in 933 European ancestry individuals with severe asthma based on Global Initiative for Asthma (GINA) criteria 3 or above and 3346 clean controls. After standard quality control measures, the association of 480 889 genotyped single nucleotide polymorphisms (SNPs) was tested. To improve the resolution of the association signals identified, non-genotyped SNPs were imputed in these regions using a dense reference panel of SNP genotypes from the 1000 Genomes Project. Then replication of SNPs of interest was undertaken in a further 231 cases and 1345 controls and a meta-analysis was performed to combine the results across studies. RESULTS: An association was confirmed in subjects with severe asthma of loci previously identified for association with mild to moderate asthma. The strongest evidence was seen for the ORMDL3/GSDMB locus on chromosome 17q12-21 (rs4794820, p=1.03×10((-8)) following meta-analysis) meeting genome-wide significance. Strong evidence was also found for the IL1RL1/IL18R1 locus on 2q12 (rs9807989, p=5.59×10((-8)) following meta-analysis) just below this threshold. No novel loci for susceptibility to severe asthma met strict criteria for genome-wide significance. CONCLUSIONS: The largest genome-wide association study of severe asthma to date was carried out and strong evidence found for the association of two previously identified asthma susceptibility loci in patients with severe disease. A number of novel regions with suggestive evidence were also identified warranting further study.

Profiling of sputum inflammatory mediators in asthma and chronic obstructive pulmonary disease.

BACKGROUND: Asthma and chronic obstructive pulmonary disease (COPD) display features of overlap in airway physiology and airway inflammation. Whether inflammatory phenotypes in airway disease describe similar mediator expression is unknown. OBJECTIVES: To explore the relationship of airway inflammation and cytokine and chemokine expression in asthma and COPD. METHODS: Subjects with asthma and COPD (n = 54 and n = 49) were studied. Clinical characteristics and sputum were collected at entry into the study. A 2-step sputum processing method was performed for supernatant and cytospin preparation. Meso Scale Discovery and Luminex platforms were used to measure cytokines, chemokines and matrix metalloproteinase levels. RESULTS: Analytes sensitive to dithiothreitol (DTT) that had increased recovery in the 2-step sputum process were IL-1ß, 4, 5, 10, 13, IFN-γ, TNFRI, GM-CSF, CCL2, 3, 4, 5, 13 and 17. There was a differential expression in IL-8, TNFRI and TNFRII between asthma and COPD [mean fold difference (95% CI): IL-8, 2.6 (1.3-5.4), p = 0.01; TNFRI, 2.1 (1.3-5.4), p = 0.03; TNFRII, 2.6 (1.2-5.6), p = 0.02]. In neutrophilic and eosinophilic airway inflammation, TNFα, TNFRI, TNFRII, IL-6, IL-8 and IL-5 could differentiate between these phenotypes. However, these phenotypes were unrelated to the diagnosis of asthma or COPD. CONCLUSION: Recovery of sputum mediators sensitive to DTT can be improved using the described sputum processing technique. Within airway inflammatory sub-phenotypes there is a differential pattern of mediator expression that is independent of disease. Whether these inflammatory phenotypes in asthma and COPD confer distinct pathogeneses, therapeutic responses and clinical phenotypes needs to be further evaluated.

Sputum IL-5 concentration is associated with a sputum eosinophilia and attenuated by corticosteroid therapy in COPD.

BACKGROUND: Airway inflammation in chronic obstructive pulmonary disease (COPD) is predominately neutrophilic, but some subjects demonstrate eosinophilic airway inflammation. Whether these inflammatory phenotypes have differential cytokine and chemokine expression is unknown. OBJECTIVES: To assess the sputum concentrations of cytokines and chemokines and their response to oral corticosteroid therapy in COPD subjects with or without a sputum eosinophilia. METHODS: Cytokine and chemokine concentrations were measured using the meso-scale device platform. To assess validity, recovery of exogenous spikes was examined. The concentrations of the validated mediators were measured in COPD sputum from subjects with or without a sputum eosinophilia. In a subgroup with a sputum eosinophilia, the response to oral prednisolone 10 mg for 1 month was examined. RESULTS: The recovery in sputum of exogenous spiked mediators was >80% in 11/26 cytokines and chemokines. In supernatants from eosinophilic (n = 39) versus non-eosinophilic (n = 59) sputa, the geometric mean (95% CI) concentration was increased for IL-5 [9.0 (4.5-18) pg/ml vs. 3.6 (2.7-6.3) pg/ml, p = 0.03]. IL-5 alone was correlated with sputum eosinophil counts (r = 0.33, p = 0.001), and was attenuated following treatment with prednisolone [n = 9; mean difference 2.3 pg/ml (0.2-4.3), p = 0.032]. CONCLUSION: We have validated the use of the meso-scale device platform for cytokine and chemokine measurements in the sputum supernatants in COPD. Sputum IL-5 was associated with a sputum eosinophilia and was attenuated following oral corticosteroid therapy. Whether this cytokine is important in the pathogenesis of COPD in a subgroup of patients warrants further investigation.

The acute wheezy adult with airways disease in the emergency department: a retrospective case-note review of exacerbations of COPD.

Introduction: There has been an increase in interest in the peripheral blood eosinophil count as a biomarker in COPD. Few studies have examined the eosinophil count in patients attending the emergency department (ED) with acute exacerbations of COPD (AECOPD). We investigated the relationship between the blood eosinophil and other variables collected routinely at ED presentation and outcomes. Methods: Retrospective case note review of patients attending the ED with an AECOPD over 18 months. Demographic, clinical and pharmacological data were analyzed at the time of presentation, and clinical outcomes relating to hospital admission, length of hospital stay and mortality were investigated. Results: There were 743 AECOPD index events in 537 patients. Over half (57%) of all attendees were admitted to hospital. They were older, reported an increased number of exacerbations and higher levels of total leukocytes and neutrophils. Length of stay was shorter in patients with a blood eosinophil count ≥2% compared to <2% (median (IQR) 3 days (1-7) vs 4 days (2-8) respectively, p<0.05). Length of stay correlated with peripheral blood neutrophils (r=0.12, p=0.021), peripheral blood absolute and relative eosinophils (r=-0.12, p=0.024 and r=-0.11, p=0.035, respectively) and CRP (r=0.16, p=0.027). Non-eosinophilic AECOPD were associated with an increased risk of mortality during an exacerbation (χ2 5.9, OR 3.08, 95% CI 1.19-7.96, p=0.015). Conclusion: In exacerbations of COPD presenting to ED, a higher blood eosinophil count is associated with a shorter length of stay and reduced mortality.