A multi-mutant herpes simplex virus vector has minimal cytotoxic effects on the distribution of filamentous actin, α-actinin 2 and a glutamate receptor in differentiated PC12 cells

To develop effective gene therapy techniques that target populations of neurons in the spinal cord, suitable vectors must be developed that will undergo efficient, retrograde transport from an appropriate peripheral site and will not be cytotoxic. Our previous work (LeVatte ef al, 1998a) has demonstrated that a replication defective herpes simplex virus vector 14H Delta 3vhsZ, that has been substantially detoxified, is retrogradely transported from peripheral sites and can infect large numbers of the targeted spinal neurons. We plan to develop targeted gene therapy approaches designed to modulate the excitatory glutamatergic methyl-D-aspartate (NMDA) receptor in spinal cord neurons as a means of ameliorating a form of episodic high blood pressure that occurs after spinal cord injury. In this report, we demonstrate that, in differentiated PC12 cells, a neuronal-like cell line, the virus vector does not appear to alter aspects of the cytoskeletal architecture important to the proper distribution of the NMDA receptor. In turn, the distribution of endogenous NMDA receptor 1 subunit protein (NMDAR1) or a transfected NMDAR1-green fluorescent fusion protein was also found to be unaltered after vector infection. However, whereas endogenous NMDAR1 distribution was maintained, vector infection did tend to reduce the level of its expression. This drop in endogenous NMDAR1 expression coincided with the expression of the HSV immediate early genes ICP0 and ICP27 over the first 24-48 h. These results indicate that the 14H Delta 3vhsZ herpes simplex virus vector is suitable to use in future strategies to alter the level of gene expression in targeted populations of spinal cord neurons.