Next we determined the status of virus replication in the viable and non-adherent cells. Cells collected at six days post-infection were analyzed by flow cytometry for expression of the cHV68 glycoprotein, gp150, which is expressed during the lytic transcription program on the surface of infected cells [19] . Cell viability was also determined using propidium iodide (PI), a cell impermeant dye that is excluded from intact cell membranes. In these experiments we also included the S11E cell line, a mouse B cell lymphoma line which harbors latent cHV68, and therefore is negative for gp150 surface expression [20] . The majority of MB114 endothelial cells and 3T12 fibroblasts were positive for surface gp150 expression (Fig. 2C ). While 3T12 fibroblasts were mostly PI positive, MB114 endothelial cells excluded PI. These data indicated that endothelial cells which remained viable at six days post-infection were undergoing the lytic transcription program and were not latent or uninfected.