49. AAV Vector-Mediated Gene Delivery of Aromatic L-Amino Acid Decarboxylase Restored L-DOPA Efficacy in a Primate Bilateral Model of Parkinson's Disease

Abstract

Activity dependent neurotropic factor (ADNF) occurs endogenously in astrocytes, and both ADNF and the fragment, ADNF-9, exert potent neuroprotective properties (Brenneman et al., JPET:285,619,1998). Recently, Haberman et al. (Nat. Med.9:1076,2003) showed that the fibronectin secretory signal sequence (FIB) could be used to constitutively secrete an active gene product from neurons transduced by adeno-associated virus vectors(AAV) in vivo. Given the extraordinary potency of ADNF (femtomolar range), we conducted a study to determine if linking the FIB to the ADNF-9 coding sequence would prove sufficient to protect substantia nigra neurons from striatal infusions of the neurotoxin, 6-OHDA. Rats first received a 2 microliter unilateral striatal infusion of AAV-FIB-ADNF and one week later, received two unilateral striatal infusions of 6-OHDA (3.5 micrograms/ 1 microliter per infusion). Two weeks later, the rats were perfused, and the presence of tyrosine hydroxylase (TH) was determined immunohistochemically. In the striatum 6-OHDA treatment caused a significant loss of TH containing terminals both in the control and AAV-FIB-ADNF treated rats. In the substantia nigra, the control 6-OHDA rats exhibited a 47±5% decrease in TH positive cells compared to the untreated side. However, no decrease in TH containing cells was observed in the AAV-FIB-ADNF treated group. Thus, striatal infusion of AAV-FIB-ADNF protected substantia nigra TH containing neurons from 6-OHDA-induced cell death, a finding likely attributible to retrograde transport of the AAV-FIB-ADNF from the striatum to the substantia nigra. These findings illustrate the utility of AAV mediated expression and secretion of neuroprotective gene products in vivo.