Convection-Enhanced Delivery of AAV Vector in Parkinsonian Monkeys; In Vivo Detection of Gene Expression and Restoration of Dopaminergic Function Using Pro-drug Approach

Abstract

Using an approach that combines gene therapy with aromatic L-amino acid decarboxylase (AADC) gene and a pro-drug (L-dopa), dopamine, the neurotransmitter involved in Parkinson's disease, can be synthesized and regulated. Striatal neurons infected with the AADC gene by an adeno-associated viral vector can convert peripheral L-dopa to dopamine and may therefore provide a buffer for unmetabolized L-dopa. This approach to treating Parkinson's disease may reduce the need for L-dopa/carbidopa, thus providing a better clinical response with fewer side effects. In addition, the imbalance in dopamine production between the nigrostriatal and mesolimbic dopaminergic systems can be corrected by using AADC gene delivery to the striatum. We have also demonstrated that a fundamental obstacle in the gene therapy approach to the central nervous system, i.e., the ability to deliver viral vectors in sufficient quantities to the whole brain, can be overcome by using convection-enhanced delivery. Finally, this study demonstrates that positron emission tomography and the AADC tracer, 6-[ 18 F]fluoro-Lm-tyrosine, can be used to monitor gene therapy in vivo. Our therapeutic approach has the potential to restore dopamine production, even late in the disease process, at levels that can be maintained during continued nigrostriatal degeneration.

Intracranial Delivery of CLN2 Reduces Brain Pathology in a Mouse Model of Classical Late Infantile Neuronal Ceroid Lipofuscinosis

“…This is also supported by a dose-response study that showed loss of axonal transport with decreasing titers of AAV vectors (Kaspar et al, 2003). Alternatively, widespread AAV distribution may be achieved with pressure-mediated, convection-enhanced delivery (Bankiewicz et al, 2000;Nguyen et al, 2001). Coinjection of AAV with hyperosmotic agents or molecules that bind to their receptors may also provide broader distribution (Mastakov et Comparison of TPP1 activity in AAV2 CU hCLN2-or AAV5 CU hCLN2-treated brains at 13 weeks after injection.…”

Delayed delivery of AAV-GDNF prevents nigral neurodegeneration and promotes functional recovery in a rat model of Parkinson's disease

“…14 Previous studies, including our own, have demonstrated that AAV vector-mediated delivery of dopamine-synthesizing enzymes results in efficient long-term expression of the transgene in the striatum. [14][15][16] The present study used the Sauer and Oertel partial PD model. 17 In this model, intrastriatal injection of 6-OHDA induces progressive retrograde degeneration of DA neurons that starts between 1 to 2 weeks after lesioning and continues over 8 to 16 weeks.…”

Focal striatal dopamine may potentiate dyskinesias in parkinsonian monkeys

“…In one vector formulation that included an excess of empty AAV capsids produced by a column purification method, we observed reduction of AADC distribution associated with highly focal AADC expression determined by postmortem histochemical examination (Eberling et al, 2003). Diffuse expression of AADC is ordinarily generated by convection-enhanced delivery (CED) of CsCl-purified vector (Bankiewicz et al, 2000). The association of the appearance of severe LID with focal delivery of AADC has led to the insight that highly focal delivery of AADC activity could be used to as a research tool to probe the neural mechanisms underlying dyskinesias.…”

“…Transduced with this vector, striatal neurons gain the ability to produce DA from exogenous L-dopa, a dopamine precursor. Briefly, expression of AADC in the striatum of parkinsonian rodents and monkeys greatly enhanced the efficacy of exogenously supplied L-dopa (Bankiewicz et al, 2000;Sanchez-Pernaute et al, 2001). In PD, it is primarily the loss of L-dopa conversion efficiency that underlies the progressive wearing off of L-dopa responsiveness.…”