Intercellular delivery of a herpes simplex virus VP22 fusion protein from cells infected with lentiviral vectors

Effective gene therapy depends on the efficient transfer of therapeutic gen es and their protein products to target cells. Lentiviral vectors appear pr omising for virus-mediated gene delivery and longterm expression in nondivi ding cells. The herpes simplex virus type 1 tegument protein VP22 has recen tly been shown to mediate intercellular transport of proteins, raising the possibility that it may he helpful in a setting where the global delivery o f therapeutic proteins is desired, To investigate the effectiveness of lent iviral vectors to deliver genes encoding proteins fused to VP22, and to tes t whether the system is sufficiently potent to allow protein delivery from transduced cells in vitro and in vivo, fusion constructs of VP22 and the en hanced green fluorescent protein (EGFP) were prepared and delivered into ta rget cells by using HIV-l-based lentiviral vectors. To follow the spread of VP22-EGFP to other cells, transduced COS-7 cells were coplated with a numb er of different cell types, including brain choroid plexus cells, human end othelial cells, H9 cells, and HeLa cells. We found that VP22-EGFP fusion pr oteins were transported from transduced cells to recipient cells and that s uch fusion proteins accumulated in the nucleus and in the cytoplasm of such cells. To determine the ability to deliver fusion proteins in vivo, we inj ected transduced H9 cells as well as the viral vector directly into the bra in of mice. We present evidence that VP22-EGFP fusion proteins were transpo rted effectively from lentivirus transduced cells in vivo. We also show tha t the VP22-EGFP fusion protein encoded by the lentivirus is transported bet ween cells. Our data indicate that such fusion proteins are present in the nucleus and in the cytoplasm of neighboring cells. Therefore, lentiviral ve ctors may provide a potent biological system for delivering genes encoding therapeutic proteins fused to VP22.