Intercellular spread of GFP-VP22.

The herpes simplex virus type 1 (HSV-1) VP22 polypeptide has been reported to mediate intercellular trafficking of heterologous proteins fused to its C- or N-terminus, a feature making it a useful tool in bystander cell-targeted gene therapy. Here we show, by detection of Green Fluorescent Protein (GFP) fused to VP22, its subcellular distribution in living producer (transfected) and recipient (non-transfected) cells as well as in cells after fixation. Four cell lines from different species were used. Different fractions of translocated GFP-VP22 fusion protein could be detected in fixed recipient cells by two different methods of fixation. Functional GFP in live recipient cells could not be detected. Our study indicates that the VP22-chimeric protein transfer in its present form is suboptimal in terms of protein function. However, after fixation, the GFP signal in 100% of cells in a monolayer can be detected even at moderate transfection efficiency.