Increased levels of BAL cysteinyl leukotrienes in acute RSV bronchiolitis

Abstract Background: Cysteinyl leukotrienes (CysLTs), including LTC4, LTD4 and LTE4, are pivotal mediators in the pathophysiology of asthma. Aim: To determine whether CysLT levels are increased in the lower airways of children with respiratory syncytial virus (RSV) bronchiolitis, as they are in asthmatic children, and to investigate a possible heterogeneity in CysLT levels in children with RSV bronchiolitis. Methods:Bronchoalveolar lavage (BAL) fluids were obtained from children with acute RSV bronchiolitis (n=20), from children with acute asthma who had no identifiable virus infection (n=16) and from control subjects (n=14). BAL cell counts and differentials were determined, and the concentrations of CysLTs were measured by ELISA. Results: CysLT levels in the asthma (70.6±52.7 pg/ml, p < 0.001) and bronchiolitis groups (21.9±23.3 pg/ml, p < 0.05) were significantly higher than in the control group (8.7±5.2 pg/ml). Among bronchiolitis subjects, the eosinophil‐positive subgroup (n=6) showed significantly higher CysLT levels (49.0±26.7 pg/ml, p = 0.001) than the control group, but this was not observed in the eosinophil‐negative subgroup (n=14, 10.3±6.3 pg/ml, p = 0.47). Conclusion: CysLT levels are increased in the lower airways during RSV bronchiolitis, although their intensities are lower than those in acute asthma. Among bronchiolitis subjects, high CysLT producers could be distinguished from low CysLT producers by the presence of eosinophilia in BAL fluids, suggesting a pathophysiological heterogeneity in RSV bronchiolitis.