Leukotriene synthesis during respiratory syncytial virus bronchiolitis: influence of age and atopy

Respiratory syncytial virus (RSV) infection is the most common cause of bronchiolitis in infants and an important risk factor for the development of recurrent wheezing and asthma. Cysteinyl leukotrienes were implicated in the pathophysiology of these diseases, and are being targeted for their diagnosis and therapy. We measured urinary leukotriene E4 (LTE4) in infants with RSV bronchiolitis in comparison with controls without respiratory infection, and investigated whether medical and family history, age, and passive exposure to tobacco smoke are related to urinary leukotriene excretion. We studied 33 infants with bronchiolitis and 25 controls, 1-12 months of age. Demographic and historical data were obtained from informed-consent forms and questionnaires completed by the parents. RSV was detected in nasal secretions by enzyme-linked immunoassay. Urine samples were collected on day of admission and were analyzed for LTE4 with an enzyme-linked immunoassay. Urinary LTE4 was 8-fold higher in infants with bronchiolitis than in controls. Leukotriene excretion was significantly higher in infected infants <6 months of age with a medical history of eczema or dry cough and/or family history of asthma. Multivariate analysis revealed that eczema and dry cough are independently associated with high LTE4 excretion during bronchiolitis. Exposure to tobacco smoke did not affect urinary LTE4. Our study shows that leukotriene synthesis during bronchiolitis is particularly elevated in younger infants with an atopic/asthmatic background. Urinary LTE4 may become a valuable, noninvasive marker for the identification of patients who will benefit most from therapy with leukotriene modifiers for management of bronchiolitis.