Dysfunctional neutrophil Type 1 interferon responses in preschool children with recurrent wheezing and IL-4-mediated aeroallergen sensitization
The innate mechanisms associated with viral exacerbations in preschool children with recurrent wheezing are not understood.  We assessed differential gene expression in blood neutrophils from preschool children with recurrent wheezing, stratified by aeroallergen sensitization, at baseline and after exposure to polyinosinic-polycytidylic acid (poly(I:C)). We also examined whether poly(I:C)-stimulated blood neutrophils influenced airway epithelial gene expression. Blood neutrophils were purified and cultured overnight with poly(I:C) and underwent next-generation sequencing with Reactome pathway analysis. Primary human small airway epithelial cells were treated with poly(I:C)-treated neutrophil culture supernatants and were analyzed for Type 1 interferon gene expression with a targeted array. Symptoms and exacerbations were assessed in participants over 12 months. 436 genes were differently expressed in neutrophils from children with versus without aeroallergen sensitization at baseline, with significant downregulation of Type 1 interferons. These Type 1 interferons were significantly upregulated in sensitized children after poly(I:C) stimulation. Confirmatory experiments demonstrated similar upregulation of Type 1 interferons in IL-4 treated neutrophils stimulated with poly(I:C). Poly(I:C)-treated neutrophil supernatants from children with aeroallergen sensitization also induced a Type 1 interferon response in epithelial cells. Children with aeroallergen sensitization also had higher symptom scores during exacerbations and these symptom differences persisted for three days after prednisolone treatment.  We conclude that Type 1 interferon responses are dysregulated in preschool children with aeroallergen sensitization, which is in turn associated with exacerbation severity. Given the importance of Type 1 interferon signaling in viral resolution, additional studies of neutrophil Type 1 interferon responses are needed in this population. Overall design: Preschool children 12-59 months of age with recurrent wheezing and at least one wheezing episode treated with systemic corticosteroids in the previous 12 months were included in the study. Recurrent wheezing was defined as a lifetime history of two or more episodes of wheezing, with each episode lasting at least 24 hours and requiring repeated treatment with albuterol sulfate. Children were excluded if they had co-morbid disorders associated with wheezing (such as immune deficiency, cystic fibrosis, pulmonary aspiration, congenital airway anomalies, or premature birth before 35 weeks gestation) or if they had a significant developmental delay or failure to thrive. Preschool participants submitted blood samples for RNA-seq and determination of aeroallergen sensitization. Aeroallergen sensitization was determined by specific IgE testing with an inhalant allergen panel specific to the Atlanta region with twelve extracts: Dermatophagoides farinae, Dermatophagoides pteronyssinus, dog dander, cat dander, Blatella germanica, Alternaria tenuis, Aspergillus fumagatis, oak tree, pecan tree, Bermuda grass, Johnson grass, and common ragweed (Ambrosia artemisiifolia) (Greer® Laboratories, Lenoir, North Carolina). Tests were considered positive if specific IgE values were >0.35 kU/L.