title: Reduced PRF1 enhancer methylation in children with a history of severe RSV bronchiolitis in infancy: an association study.
abstract: Acute lower respiratory tract infection is the commonest disease affecting children under five worldwide. Respiratory syncytial virus (RSV) is among the most common causative pathogens. Epidemiological data suggest an association between severe viral respiratory infections in infancy and increased incidence of childhood wheeze and asthma. DNA methylation is involved in immune cell differentiation and identity. It provides an avenue for environmental influences on the genome and therefore has potential as a marker for sustained effects of infectious insults. In this study we investigated the association between DNA methylation patterns in the perforin gene (PRF1) in childhood and a history of hospitalisation for severe RSV disease in the first two years of life.
  
  
  
  In this retrospective study, we explored patterns of whole blood DNA methylation at a methylation sensitive region of the proximal PRF1 enhancer in a group of children with a record of hospitalisation for severe RSV disease during infancy (n = 43) compared to healthy controls matched for age and sex with no similar hospitalisation history, no allergy and no persistent wheeze (n = 43). Univariate and bivariate conditional logistic regression analyses were conducted to test the association between PRF1 enhancer methylation and record of hospitalisation for RSV disease.
  
  
  
  Children with a record of hospitalisation for severe RSV bronchiolitis demonstrated markedly lower levels of DNA methylation at two cytosine-phosphate-guanine dinucleotide (CpG) loci of the PRF1 proximal enhancer, corresponding to a signal transducer and activator of transcription 5 (STAT5) responsive element, compared to controls, adjusted odds ratios of 0.82 (95% confidence interval [CI] 0.71, 0.94) and 0.73 (95% CI 0.58, 0.92) for each 1% increase in DNA methylation. Smoking in the household showed a significant influence on DNA methylation at the assayed positions.
  
  
  
  Our findings support an association between childhood DNA methylation patterns in PRF1 and a record of severe RSV infection in infancy. Longitudinal studies are required to establish the utility of PRF1 methylation as a marker of severe RSV disease.
authors.affiliation: Center for Chronic Immunodeficiency, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Breisacherstr. 115 4, Freiburg, D-79106, Germany.
authors.forename: Magdeldin
authors.initials: M
authors.lastname: Elgizouli
authors.affiliation: Institute of Epidemiology and Medical Biometry, Ulm University, Ulm, Germany.
authors.forename: Chad
authors.initials: C
authors.lastname: Logan
authors.affiliation: Department of Pediatrics and Adolescent Medicine, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
authors.forename: Ruth
authors.initials: R
authors.lastname: Grychtol
authors.affiliation: Institute of Epidemiology and Medical Biometry, Ulm University, Ulm, Germany.
authors.forename: Dietrich
authors.initials: D
authors.lastname: Rothenbacher
authors.affiliation: Center for Chronic Immunodeficiency, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Breisacherstr. 115 4, Freiburg, D-79106, Germany. alexandra.nieters@uniklinik-freiburg.de.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Nieters
authors.affiliation: Department of Pediatrics and Adolescent Medicine, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Heinzmann
mesh_terms: D001990:Bronchiolitis, Viral / Q000235:genetics*; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D019175:DNA Methylation; D004742:Enhancer Elements, Genetic; D005260:Female; D005819:Genetic Markers; D006760:Hospitalization; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016015:Logistic Models; D008297:Male; D054353:Perforin / Q000235:genetics*; D018357:Respiratory Syncytial Virus Infections / Q000235:genetics*; D012189:Retrospective Studies; D012720:Severity of Illness Index
chemical_list: D005819:Genetic Markers; C510468:PRF1 protein, human; D054353:Perforin
keywords: DNA methylation; Infant bronchiolitis; PRF1; Perforin; Respiratory syncytial virus