An HSV‐1 Vector Expressing Tyrosine Hydroxylase Causes Production and Release of l‐DOPA from Cultured Rat Striatal Cells

Abstract: In this report we demonstrate that a defective herpes simplex virus type one (HSV‐1) vector can express enzymatically active tyrosine hydroxylase in cultured striatal cells that are thereby converted into l‐DOPA‐producing cells. A human tyrosine hydroxylase cDNA (form II) was inserted into an HSV‐1 vector (pHSVth) and packaged into virus particles using an HSV‐1 strain 17 mutant in the immediate early 3 gene (either ts K or D30EBA) as helper virus. Cultured fibroblasts were infected with pHSVth and 1 day later tyrosine hydroxylase immunoreactivity and tyrosine hydroxylase enzyme activity were observed. The tyrosine hydroxylase enzyme activity directed the production of l‐DOPA. pHSVth infection of striatal cells in dissociated cell culture resulted in expression of tyrosine hydroxylase RNA and tyrosine hydroxylase immunoreactivity. Release of l‐DOPA and low levels of dopamine were observed from cells in pHSVth‐infected striatal cultures. Expression of tyrosine hydroxylase and release of catecholamines were maintained for at least 1 week after infection.