Using the same surface staining model, but with a permeabilisation step (Figure 3B, schematic model), we followed the intracellular trafficking of membrane CD155 by confocal microscopy and found that a significant portion of plasma membrane-stained CD155 (PM-CD155) 20 hr post-infection (p.i.)resided in the AP-1 compartment in MCMV-infected cells, confirming the membrane origin of the intracellularly accumulated CD155 (Figure 3B, upper panel). This evidence concerns the gene PVR and infection.