(1213) Identification of Inflammatory Epithelial Cells in RSV Bronchiolitis

Introduction: Despite the prevalence of respiratory syncytial virus (RSV) bronchiolitis, mechanisms of disease severity remain poorly understood. Bulk RNA-sequencing of nasal mucosa from infants with critical RSV bronchiolitis shows that increased expression of ciliated cell genes and decreased expression of basal cell genes, evidence of epithelial damage, is associated with outcomes. Nasal viral load did not correlate with severity, but inflammatory signatures were seen in severe disease, suggesting immune dysregulation. Inflammatory epithelial cell subtypes have recently been observed in airway epithelium during SARS-CoV-2 infection. We aimed to determine if inflammatory epithelial cell subtypes emerge in the nasal mucosa of children with severe RSV bronchiolitis and if they are associated with outcomes.

Methods: Nasal mucosa samples were collected using scrape biopsies of the inferior nasal turbinate from children less than 2 years of age hospitalized with RSV bronchiolitis. We performed single cell transcriptional profiling and electronic medical record review to investigate cell types and gene expression profiles associated with disease severity.

Results: We collected and processed 26 nasal mucosa samples for single cell RNA sequencing (scRNAseq). After assessing cell count and viability, 11 of the 26 samples were suitable for complete sequencing and analysis. Participant age ranged from 1 to 20 months. Three participants received less than one day of respiratory support, five received between 2 and 3 days of respiratory support, and three received 4 or more days of respiratory support. Distinct epithelial and immune cell subtypes were identified in infants infected with RSV. We observed inflammatory goblet cells (MUC5AC+BPIFA1+) expressing interferon-stimulated genes, but not type I interferons.

Conclusions: Inflammatory epithelial cells are observed in the nasal mucosa of children hospitalized with RSV bronchiolitis that have been previously associated with severity of illness in viral infection. Improved understanding of the epithelial inflammatory response in severe RSV infection may identify mechanisms driving disease severity and provide potential therapeutic targets.