Intercellular trafficking of VP22-GFP fusion proteins is not observed in cultured mammalian cells

Herpes simplex virus type 1 (HSV-1) VP22 was recently reported to mediate intercellular trafficking of a protein fused to the C-terminus of VP22. To explore the application of such trafficking, we constructed plasmids expressing green fluorescent protein (GFP) fused to the C-terminus of either wild-type VP22 or a 160 amino acid peptide from VP22. In vitro studies showed that the majority of both fused proteins were localized to the nuclei of transfected cells. Quantitative analysis of GFP-positive cells, however, showed no significant increase in intercellular protein trafficking for cells transfected with either fusion protein compared with a lacZ-expressing plasmid. Our results suggest that the use of HSV-1 VP22 for mediating intercellular trafficking of transgene products is limited.