227. Anatomical and Behavioral Effects of AAV2-Mediated Delivery of Neurturin to the Rat Striatum Prior to 6-Hydroxydopamine Induced Nigrostriatal Degeneration

Abstract

The cardinal symptoms of Parkinson's disease (PD) are due to striatal dopamine insufficiency secondary to degeneration of dopaminergic neurons in the substantia nigra (SN) pars compacta. Several reports indicate that delivery of glial cell line-derived neurotrophic factor (GDNF), and more recently neurturin (NTN), to the nigrostriatal system has neuroprotective and restorative effects in rodent and non-human primate models of PD. Viral vector mediated gene transfer represents a potentially safe and effective method of delivering neurotrophic factors to degenerating neurons. Accordingly, we are developing an adeno-associated virus type 2 (AAV2) vector encoding neurturin (CERE-120) for the treatment of PD. The present experiments examined both the anatomical and behavioral effects of CERE-120 delivery to the striatum in a rodent 6-hydroxydopamine (6-OHDA) model of PD. The AAV2 vector was selected to deliver NTN cDNA to the striatum based upon its affinity for neurons and its capacity to promote efficient and stable transgene expression in these cells. To promote efficient secretion of mature NTN from transduced cells, the natural prepro domain of the human NTN cDNA was replaced with that of the human β-nerve growth factor (NGF) as described in a separate abstract at this meeting (Ramirez et al). An initial experiment was conducted to assess the short-term anatomical effects of CERE-120 when delivered to the striatum 2 weeks prior to 6-OHDA. Twenty-six rats received unilateral intrastriatal injections of CERE-120, AAV2-GDNF (both 1 × 1012 vector genomes/mL; 4 × 109 total vector genomes per animal; n = 8), or formulation buffer (negative control; n = 10) to the striatum in two injections of 2 μL each. Two weeks following vector administration, all animals received a single dose of 20 μg of 6-OHDA in a volume of 5 μL directly into the striatum on the side ipsilateral to the vector or control injections. Animals were sacrificed 2 weeks later. A robust immunohistochemical signal for GDNF or NTN was observed in the striatum and SN of all vector-injected animals. A similar and significant sparing of tyrosine hydroxylase (TH) positive nigral neurons was also observed in both CERE-120 and AAV2-GDNF treated animals (62–68% of the intact side). A second, longer-term study employing an identical experimental design is currently in progress to further characterize the anatomical as well as the behavioral effects of CERE-120 administration in this 6-OHDA model of nigrostriatal degeneration. Behavioral and histological data will be presented. These findings will collectively provide further information about the potential utility of CERE-120 for therapeutic intervention in Parkinson's disease.