No 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.

No abstract

No abstract

Adeno-associated virus type 2 (AAV2)-based vectors are promising transgene carriers for experimental gene therapy treatments of brain diseases. However, detailed evaluation of transgene distribution, trafficking, and transport within the brain is of the utmost importance before applying any type of gene therapy in humans. We examined the distribution of AAV2-thymidine kinase (AAV2-TK) and AAV2-aromatic L-amino acid decarboxylase (AAV2-AADC) in monkey brain after convection-enhanced delivery (CED). The AADC group consisted of two 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned monkeys that received unilateral infusions of AAV2-AADC into six sites in the right hemisphere. The TK group consisted of three monkeys that received bilateral CED infusion of AAV2-TK into the putamen; one side in all three monkeys was coinfused with heparin. Six weeks after AAV delivery, the brains were collected and processed for immunohistochemical staining. Volumetric measurement of TK distribution showed that at least 75% of the putamen could be covered by a single infusion of the vector; however, no effects of heparin coadministration were found, most likely because of the already robust gene transfer achieved by CED. Interestingly, TK- and AADCimmunoreactive cells were also present outside the striatum, in the globus pallidus, subthalamic nucleus, thalamus, and substantia nigra. CED proved to be an efficient method for delivery of the AAV2 vector. Detection of the transgenes in brain structures distant from the site of injection emphasizes the potential for gene transport, and the advantages and disadvantages of CED for gene therapy deserve further study.