Meyers, Deborah A.

Rationale Immunoglobulin A (IgA) deficiency, a rare, highly heritable trait, is associated with frequent pulmonary infections, emphysema, airway changes and low lung function; however, it is unclear if reduced IgA levels may affect lung structure and function. Methods Serum IgA, IgA1 and galactose-deficient IgA1 (Gd-IgA1) levels were measured in the population-based Multi-Ethnic Study on Atherosclerosis (MESA). The MESA Lung Study measured percent emphysema on cardiac CT and airway dimensions on chest CT, and performed spirometry. Regression models were evaluated after adjustment for demographic and CT factors. Mendelian randomisation (MR) analyses were conducted using genetic variants from the Trans-Omics for Precision Medicine (TOPMed) programme. A replication analysis was performed in the SubPopulations and InteRmediate Outcome Measures In COPD Study (SPIROMICS). Measurements and main results Among 5497 participants, lower log-normalised serum IgA levels were associated with greater percent emphysema (β=−0.084; 95% CI −0.14 to –0.026; p=0.005), which was confirmed on MR (β=−0.79; 95% CI −1.4 to –0.18; p=0.011). Greater log-normalised serum Gd-IgA1 levels were associated with airway wall thickness (β=0.0079; 95% CI 0.0017 to 0.014; p=0.012; n=2580) and decline in the forced expiratory volume in one second (FEV1) (β=−0.012; 95% CI −0.021 to –0.0036; p=0.0055; n=2778) and FEV1/forced vital capacity (FVC) ratio (β=−0.0028; 95% CI −0.0048 to –0.00084; p=0.0054; n=2778). Conclusion Lower serum IgA levels were associated with greater percent emphysema. Additionally, higher Gd-IgA1 levels were associated with airway wall thickness and lung function decline. These findings support a protective role of IgA in emphysema pathogenesis and possible deleterious role of Gd-IgA1 in airway diseases.

Abstract Rationale Reliable data about the natural history of lung function decline in alpha-1 antitrypsin (AAT)-deficient Pi*MZ heterozygotes is largely missing. Objectives We hypothesized that, in adults with a tobacco smoking history, lung function deteriorates faster in Pi*MZ compared with the Pi*MM genotype. Methods We identified 1,856 Pi*MM and 79 Pi*MZ participants with ⩾20 pack-years tobacco smoking history from the SPIROMICS (Subpopulations and Intermediate Outcomes Measures in COPD Study) cohort by DNA sequencing and followed them over a median of 4.8 years, comparing radiographic and clinical characteristics between the two groups over time using regression models. Results Adjusted for age, sex, race, smoking pack-year history, and smoking status, Pi*MZ participants had a lower baseline percent predicted forced expiratory volume in 1 second (FEV1) (65.4% vs. 75.1%; difference 95% confidence interval [CI], −15.4% to −3.9%), more radiographic emphysema (<−950 Hounsfield units%, 12.9% vs. 7.8%; difference 95% CI, 2.8% to 7.5%), and nonsignificantly lower lung density. In the longitudinal analysis, the FEV1 annual rate of decline was similar in both groups over the course of the study (−34.5 ml/yr vs. −34.6 ml/yr for Pi*MZ and Pi*MM; difference 95% CI, −16.9 to 17.1 ml/yr). There were no significant differences between Pi*MZ and Pi*MM individuals in the annualized change in lung density, emphysema, patient-reported outcomes, exacerbations, or survival. The proportion with faster FEV1 decline (annual loss ⩾40 ml) was similar in Pi*MZ and Pi*MM groups. In both groups, faster FEV1 decline was associated with more air trapping and small airway disease at baseline. In Pi*MZ only, faster decline was associated with higher blood eosinophil counts (310 vs. 220 cells/μl; difference 95% CI, 30 to 140 cells/μl). In the subgroup analysis limited to a small number of currently smoking participants, no significant differences in longitudinal outcomes were found. Conclusions Despite a lower FEV1 and more emphysema at enrollment, the longitudinal analysis did not demonstrate significantly greater lung function decline or lung density loss in Pi*MZ compared with Pi*MM participants with tobacco smoking history. Limited sample size and duration of longitudinal follow-up constrain generalizability of our findings, thus prohibiting the conclusion that longitudinal trajectories did not differ between these groups. However, our results may suggest that earlier life events could be responsible for more extensive lung disease at enrollment in Pi*MZ compared with Pi*MM tobacco-exposed individuals.

Abstract Asthma is a heterogeneous disease with variable presentation and characteristics. There is a critical need to identify underlying molecular endotypes of asthma. We performed the largest transcriptomic analysis of 808 bronchial epithelial cell samples across 11 independent cohorts, including 3 cohorts from the Severe Asthma Research Program. Using seven datasets (218 patients with asthma, 148 healthy control subjects) as discovery cohorts, we identified 505 differentially expressed genes, which we validated in the remaining four datasets. Unsupervised clustering using the 505 differentially expressed genes identified four reproducible clusters of patients with asthma across all datasets, corresponding to healthy control subjects, patients with mild/moderate asthma, and patients with severe asthma with significant differences in several clinical markers of severity, including pulmonary function, Type 2 inflammation, fractional exhaled nitric oxide, and maximum bronchodilator reversibility. Importantly, we found the same clusters in pediatric patients using nasal lavage fluid cells, demonstrating the gene signature and clusters are not confounded by age and are conserved in both lower and upper airways. The four asthma clusters may represent a unifying framework for understanding the molecular heterogeneity of asthma. Further study could potentially enable a precision medicine approach of matching therapies with patients with asthma most likely to benefit.