Herpes Simplex Virus (HSV-1) vectors are being developed for gene therapy of aging disorders such as Parkinson's Disease (PD). The long range goal of the project is to use HSV-1 vectors to deliver the genes responsible for monamine synthesis directly into striatal neurons and glia, in the adult mammalian brain, for human gene therapy of the aging disorder, PD. Thus, this project will also serve as a model for gene therapy approaches to other aging disorders. We have established that a HSV-1 vector expressing human tyrosine hydroxylase (TH) can cause regulated release of both L-Dopa and dopamine from cultured striatal neurons. The overall goal of this proposal is to use the striatal culture expression system, that is already established, to characterize multiple vectors, in order to develop an optimum vector for use in animal studies (Our colleagues are currently performing parallel studies in the rat model of PD, not part of this proposal.). Among the parameters that will be examined are first, the optimum striatal cell type for TH expression: This will be approached by limiting TH expression to striatal neurons, or glia, or cholinergic neurons, by constructing and characterizing vectors that express TH from the i) human neurofilament L, ii) rat GFAP, and iii) rat choline acetyl transferase promoters. Second, we will construct and characterize vectors that coexpress TH and aromatic amino acid decarboxylase (ADDC) in the same cell, to determine if coexpression of TH and AADC causes efficient production of dopamine. Lastly, we will improve the defective HSV-L vector packaging system to support use in humans.