PAF receptor expression on the cell surface is upregulated during RSV infection in A549 cells [26] . The RSV-induced upregulation of the PAF receptor was significantly suppressed by CAM and PDTC in a dose-dependent manner ( Figure 3 ). The degree of suppression by CAM was slightly less than that by PDTC. Suppression of the PAF receptor expression was also observed when A549 cells were posttreated with CAM (4 or 12 h after RSV infection) (data not shown). We examined the adhesion of FITC-labeled S. pneumoniae cells to A549 cells by fluorescence microscopy (Figure 4 ) and flow cytometry ( Figure 5 ). RSV infection significantly enhanced the adhesion of S. pneumoniae to A549 cells, and this enhancement was suppressed by adding a PAF receptor antagonist (Figures 4 and 5) or anti-PAF receptor monoclonal antibody (data not shown). This result indicated that the RSV-induced S. pneumoniae adhesion occurs via the PAF receptor on A549 cells. The bacterial adhesion was significantly suppressed by CAM, as well as PDTC.