HIGH-EFFICIENCY GENE-TRANSFER TO THE CENTRAL-NERVOUS-SYSTEM OF RODENTS AND PRIMATES USING HERPES-VIRUS VECTORS LACKING FUNCTIONAL ICP27 ANDICP34.5

The safe and efficient use of herpes simplex virus (HSV)-based vectors to deliver genes of potentially therapeutic benefit to the central ne rvous system will require their effective disablement by the inactivat ion of viral genes required for lytic growth. Here we report that viru ses lacking functional genes for ICP27 (which is required for growth i n all cell types) and ICP34.5 (which is required for growth in nondivi ng cell types) can deliver a marker gene to both the rodent and primat e CNS with high efficiency whilst producing relatively minimal damage and having no effect on sodium currents in dorsal root ganglion neuron s. Such viruses paradoxically deliver genes at much higher efficiency that the less disabled single mutant lacking ICP34.5 alone and also, a s expected, produce less damage in vivo. Moreover, unlike the single m utant lacking ICP27 the double mutant viruses cannot revert to wild-ty pe by acquisition of complimenting gene sequence during growth of viru s stocks in vitro on dividing cells expressing ICP27 since artificial expression of ICP34.5 in these cells is not required. Such ICP27-; ICP 34.5- viruses thus offer a platform for the development of vectors whi ch are sufficiently safe for ultimate use in human gene therapy.