Cell-Specific Expression of RANTES, MCP-1, and MIP-1a by Lower Airway Epithelial Cells and Eosinophils Infected with Respiratory Syncytial Virus

Respiratory syncytial virus (RSV) is the major cause of acute bronchiolitis in infancy, a syndrome characterized by wheezing, respiratory distress, and the pathologic findings of peribronchial mononuclear cell infiltration and release of inflammatory mediators by basophil and eosinophil leukocytes. Composition and activation of this cellular response are thought to rely on the discrete target cell selectivity of C-C chemokines. We demonstrate that infection in vitro of human epithelial cells of the lower respiratory tract by RSV induced doseand time-dependent increases in mRNA and protein secretion for RANTES (regulated upon activation, normal T-cell expressed and presumably secreted), monocyte chemotactic protein-1 (MCP-1), and macrophage inflammatory protein-1a (MIP-1a). Production of MCP-1 and MIP-1a was selectively localized only in epithelial cells of the small airways and lung. Exposure of epithelial cells to gamma interferon (IFN-g), in combination with RSV infection, induced a significant increase in RANTES production that was synergistic with respect to that obtained by RSV infection or IFN-g treatment alone. Epithelial cell-derived chemokines exhibited a strong chemotactic activity for normal human blood eosinophils. Furthermore, eosinophils were susceptible to RSV and released RANTES and MIP-1a as a result of infection. Therefore, the inflammatory process in RSV-induced bronchiolitis appears to be triggered by the infection of epithelial cells and further amplified via mechanisms driven by IFN-g and by the secretion of eosinophil chemokines.