IL-8 and neutrophil elastase levels in the respiratory tract of infants with RSV bronchiolitis

The aim of this study was to determine whether interleukin (IL)-8 is releas ed within the upper respiratory tract of infants during respiratory syncyti al virus (RSV) bronchiolitis and whether the large number of polymorphonucl ear neutrophils (PMNs) present in the respiratory tract of these infants ar e contributing to the inflammation through release of inflammatory mediator s. Twenty-seven infants,vith acute bronchiolitis were recruited during one win ter epidemic and 20 infant control subjects were recruited from a cohort pa rticipating in a community-based vaccine study. Samples of airways fluid we re obtained using nasal lavage. The lavage fluid was spun to remove the cel ls, and the supernatant was stored at -70 degrees C. The supernatants were subsequently assayed for the presence of IL-8, total human neutrophil elast ase (HNE) and neutrophil elastase activity. In the children with bronchiolitis compared with control infants, elevated levels of IL-8 (median (range) 1.53 (0-153) versus 0 (0-5.6) ng.mL(-1)) HNE (136 (32-694) versus 14 (0-516) ng.mL(-1)) and elastase activity (4 (1-220 ) versus 1 (0-339) mU.mL(-1)) were found. These results indicate that interleukin-8 is released in the upper respirat ory tract in response to respiratory syncytial virus infection and suggest that polymorphonuclear neutrophil products are playing an important role in the inflammatory response to respiratory syncytial virus infection in infa nts with acute bronchiolitis. This contrasts with the predominantly eosinop hilic response evident in atopic upper and lower respiratory tract disease.