FACS analysis of frozen RSV-infected HEp-2 cells. A) Flow cytometry evaluation of infectivity. Representative dot plots of forward scatter versus fluorescence of HEp-2 cells infected in vitro with RSV strain Long. A minimum of 10000 cells were acquired for each dot plot. The percentage of positive cells in the FACS analysis represents the percentage of RSV positive cells over the live cell population. This was calculated applying a forward and side-scatter gate to eliminate dead cells and debris from the analysis. B) Intracellular staining in HEP-2 cells infected with RSV strain Long. Histograms of fluorescence of cells stained intracellularly with mouse monoclonal [4 clone blend] to RSV. Controls included unstained cells and cells stained with antibody and uninfected cells stained with antibody.