Live cell imaging fails to support viral-protein-mediated intercellular trafficking.

The herpes simplex virus type I protein VP22 has been reported to have the property of intercellular trafficking. However, there is little direct evidence to demonstrate that VP22 can shuttle freely between living cells. Here, we employ a novel and simple assay using live cell fluorescence microscopy to investigate the intercellular transport property. Our results demonstrated that VP22, bovine herpesvirus-1 VP22, HSV-1 US11 and HIV Tat could not shuttle into neighboring cells via direct contact.