HLA-DQ strikes again: genome-wide association study further confirms HLA-DQ in the diagnosis of asthma among adults

BACKGROUND

Asthma is a common chronic respiratory disease in children and adults. An important genetic component to asthma susceptibility has long been recognized, most recently through the identification of several genes (e.g., ORMDL3, PDE4D, HLA-DQ, and TLE4) via genome-wide association studies.

OBJECTIVE

To identify genetic variants associated with asthma affection status using genome-wide association data.

METHODS

We describe results from a genome-wide association study on asthma performed in 3855 subjects using a panel of 455 089 single nucleotide polymorphisms (SNPs).

RESULT

The genome-wide association study resulted in the prioritization of 33 variants for immediate follow-up in a multi-staged replication effort. Of these, a common polymorphism (rs9272346) localizing to within 1 Kb of HLA-DQA1 (chromosome 6p21.3) was associated with asthma in adults (P-value = 2.2E-08) with consistent evidence in the more heterogeneous group of adults and children (P-value = 1.0E-04). Moreover, some genes identified in prior asthma GWAS were nominally associated with asthma in our populations.

CONCLUSION

Overall, our findings further replicate the HLA-DQ region in the pathogenesis of asthma. HLA-DQA1 is the fourth member of the HLA family found to be associated with asthma, in addition to the previously identified HLA-DRA, HLA-DQB1 and HLA-DQA2.

Use of biological markers of airway inflammation to detect the efficacy of nurse-delivered asthma education

OBJECTIVE

The purpose of this study was to determine whether analysis of the constituents of induced sputum could be used to document the efficacy of a nurse-delivered patient education intervention and whether changes in the biological markers of inflammation in sputum would correlate with improvements in pulmonary function and symptoms.

DESIGN

The study design was prospective, open trial with repeated measures.

SETTING

The study took place at a West Coast academic medical center laboratory.

SUBJECTS

Subjects included 12 nonsmoking persons with asthma, ages 23 to 51 years, on prescribed daily anti-inflammatory inhaled therapy who had not required oral prednisone in the previous 4 weeks of enrollment.

METHOD

The effect of one 30-minute asthma education session on spirometry, peak flow, symptoms, and biological markers of inflammation in sputum was tested for 8 weeks to determine whether biological markers reflect the efficacy of educational interventions.

RESULTS

Mean symptom scores decreased and lung function increased slightly over 8 weeks. Markers of eosinophil degranulation decreased by 50% and albumin by 25% from baseline to 8 weeks. Eosinophil percentages dropped 20% over time but did not change consistently at all time points. Clinical markers of asthma control correlated in the low-to-moderate range with biological markers of airway inflammation.

CONCLUSION

The results of this study show the effects of a patient education intervention can be detected in both clinical and biological outcomes. Individual education may influence self-care of asthma including adherence to inhaled corticosteroid therapy and thereby suppress airway inflammation.

Targets for asthma therapy

Most asthma is allergic in origin, the disease involves four distinct phases of response: the sensitization phase and the activation phase, followed by the effector phase, initiated by the release of pharmacologically active agents, the growth and repair phase, characterized by proliferation of tissues as "remodeling" of the airway wall, altering structure and function.

Use of mucin antibodies and cDNA probes to quantify hypersecretion in vivo in human airways

Mucus hypersecretion is a prominent feature of the airway's response to injury. The ability to quantitatively detect mucin and mucin mRNA in vivo in human airways would facilitate the determination of safe exposure levels to various air pollutants and the identification of drugs capable of attenuating mucus hypersecretion. To this end, we have developed two assays: an enzyme-linked immunosorbent assay (ELISA) quantifying mucin-like molecules and a polymerase chain reaction (PCR)-based assay quantifying mucin mRNA. These tests are performed on bronchial lavage fluid and epithelial cells brushed from the surfaces of human airways at bronchoscopy. The PCR data are normalized to eliminate potentially confounding effects of nonepithelial cells in the samples. In a study of six smokers and six nonsmokers, the ELISA detected significantly more mucin-like material in the airways of the smokers than of the nonsmokers. The median mucin concentration for the smokers was 52.2 micrograms/ml (range, 16.3 to 4,860.0), whereas that for the nonsmokers was 12.7 micrograms/ml (range, 4.5 to 22.9). The difference between smokers and nonsmokers was statistically significant (P < or = 0.01). The PCR-based test showed a trend for RNA samples from smokers to be enriched (vis-à-vis nonsmokers) in mucin mRNA.

Effects of nedocromil sodium on the bronchomotor response to sulfur dioxide in asthmatic patients

It is known that cromolym sodium and nedocromil sodium share similar antiallergic properties. This study examined whether nedocromil sodium, a pyranoquinoline dicarboxylic acid, could inhibit sulfur dioxide (SO2) bronchoconstriction in a dose-dependent manner in 10 men with mild asthma. Previous studies have shown that cromolyn sodium produces such inhibition in allergic monkeys and asthmatic subjects. Subjects in this double-blind, placebo-controlled study were nonsmoking men between the ages of 23 and 40 years (mean age, 30.7 years). The study took place over 5 days within a 3-week period. On the first of 5 days, each subject had a history taken and physical examination, SO2 baseline test, laboratory testing, and a methacoline dose-response test. On each of 4 test days, the subjects received pretreatment with either placebo or a 2, 4, or 8 mg dose of nedocromil sodium in a randomized, double-blind sequence, followed after 30 minutes by an SO2 dose-response test. Results showed that maximum bronchoconstriction response to SO2 was significantly attenuated (p < 0.01) by all three doses of nedocromil sodium, with small differences noted between dose levels. We concluded that nedocromil sodium inhibited SO2-induced bronchospasm at dose levels as low as 2 mg.