Respiratory syncytial virus infection enhances neutrophil and eosinophil adhesion to cultured respiratory epithelial cells. Roles of CD18 and intercellular adhesion molecule-1

Abstract

Respiratory syncytial virus (RSV) infections in children precipitate acute episodes of respiratory obstruction that are associated with influx of inflammatory cells into the airway. Since RSV can induce the expression of adhesion molecules, particularly intercellular adhesion molecule-1 (ICAM-1), by the respiratory epithelium, the hypothesis has been proposed that ICAM-1 expression contributes to airway inflammation by supporting adhesion and retention of infiltrating inflammatory leukocytes. To test this hypothesis, A549 cells (an immortalized human alveolar epithelial type II cell-like fine) were infected with RSV, and the ability of these infected monolayers to support adhesion by human neutrophils (NEUT) and eosinophils (EOS) was measured. RSV infection significantly increased ICAM-1 expression by A549 monolayers (p < 0.001). Although NEUT adhesion to A549 monolayers was significantly enhanced following RSV infection (p < 0.001), infection alone resulted in little change in EOS adherence. However, if EOS were first activated with phorbol ester (PMA), adhesion to both control and RSV-infected A549 cells was enhanced, with greater levels of adhesion supported by RSV-infected cultures (p < 0.001). The requirement for EOS activation (but not for NEUT activation) before adhesion remained when NEU and EOS were prepared and compared from the same donor. Despite this difference, NEUT and EOS adhesion was reduced by blocking Abs to epithelial ICAM-1 or granulocyte CD18 adhesion proteins (p < 0.01). However, only NEUT adhesion was blocked by Ab to CD11a. Our results show that RSV infections of respiratory epithelial monolayers can promote inflammatory cell adherence which could, in turn, potentially contribute to the airway injury and obstruction that accompanies bronchiolitis.