Acute viral bronchiolitis (NMS)

Background: A subset of infants are hyper-susceptible to severe/acute viral bronchiolitis (AVB), for reasons unknown. Purpose: To characterise the cellular/molecular mechanisms underlying infant AVB in circulating cells/local airways tissues. Methods: PBMC and nasal mucosal scrapings (NMS) were obtained from Infants (<18mths) and children (1.5-5yrs) during AVB and post-convalescence. Immune response patterns were profiled by multiplex analysis of plasma cytokines, flow cytometry, and transcriptomics (RNA-Seq). Molecular profiling of group-level data utilised a combination of upstream regulator and coexpression network analysis, followed by individual subject-level data analysis employing personalised N-of-1-pathways methodology. Results: Group-level analyses demonstrated that infant PBMC responses were dominated by monocyte-associated hyper-upregulated type I interferon signalling/pro-inflammatory pathways (drivers: TNF, IL6, TREM1, IL1B), versus a combination of inflammation (PTGER2, IL6) plus growth/repair/remodelling pathways (ERBB2, TGFB1, AREG, HGF) coupled with Th2 and NK-cell signalling in children. Age-related differences were not attributable to differential steroid usage or variations in underlying viral pathogens. Nasal mucosal responses were comparable qualitatively in infants/children, dominated by interferon types I-III, but the magnitude of upregulation was higher in infants (range 6-48-fold) than children (5-17-fold). N-of-1-pathways analysis confirmed differential upregulation of innate immunity in infants and NK cell networks in children, and additionally demonstrated covert AVB response sub-phenotypes that were independent of chronological age. Conclusions: Dysregulated expression of interferon-dependent pathways following respiratory viral infections is a defining immunophenotypic feature of AVB-susceptible infants and a subset of children. Susceptible subjects appear to represent a discrete subgroup who cluster based on (slow) kinetics of postnatal maturation of innate immune competence. Overall design: The study design consisted of PBMC from infants (<18months, n=15 pairs) and pre-school children (2-5yrs, n=16 pairs) sampled during severe acute viral bronchiolitis (acute visit = AV) and following recovery during convalescence (convalescent visit = CV). RNA-Seq profiles were generated by sequencing llumina HiSeq2500, 50bp single-end reads, v4 chemistry. Samples were sequenced across two lanes and collapsed prior analysis.

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Jones AC, Anderson D, Galbraith S, Fantino E, Gutierrez Cardenas D, Read JF, Serralha M, Holt BJ, Strickland DH, Sly PD, Bosco A, Holt PG