METHODS: Children with exacerbation prone asthma and blood eosinophils ≥150/mm3 were enrolled and nasal lavage samples collected within 72 hours of initial URI symptoms. Nasal cell differentials were determined by cytospin and nasal gene expression assessed by RNA-sequencing. 145 URIs from 104 distinct individuals were analyzed; URIs leading to asthma exacerbation (n=45) were compared to URIs that resolved without exacerbation (n=100). Differential gene expression was assessed by cell deconvolution and modular analysis coupled with linear mixed effects modeling.
RESULTS: URIs that led to an exacerbation demonstrated differential expression of 11 gene set modules (false discovery rate<0.05) representing multiple interconnected molecular pathways. Nine were increased with exacerbation, 2 were decreased. Detectable effect sizes ranged from 1.15 to 1.53. Five of the increased modules were associated with epithelial cells and represent important epithelial functions including TGFB response and EGFR signaling. Two modules were associated with eosinophils and represent eosinophil-epithelial interaction and Th2-type inflammation. The magnitude of expression change in 5 of these modules was significantly correlated with decline in lung function during the exacerbation suggesting these findings are integrally connected with exacerbation pathogenesis.
CONCLUSIONS: We identified a network of interconnected molecular pathways activated during URIs that lead to exacerbation in children with severe asthma. This systems scale platform for monitoring immune responses in pediatric asthma can be used to directly investigate mechanisms of therapeutic interventions.