521. Helper-Dependent Adenovirus with Gene Switch Regulation May Provide an Optimal Vector of Therapeutic Gene Delivery for Treatment of Parkinson's Disease

Abstract

Gene therapy is considered one of the most promising approaches to developing a novel effective treatment for Pakinson[rsquo]s disease (PD). However, the potential unwanted side effect from viral vector or from the over expression of the transgenes are the major concerns for the future clinical applications. Thus, investigating the optimal vector for gene delivery with a controllable transgene expression mechanism is important. We had reported that helper-dependent adenovirus (hdAd), a novel adenoviral construct with full deletion of viral coding sequences, is an optimal vector to deliver the gene in the lateral ventricle with less immunogenecity and toxicity while offering extended transgene expression (Hum Gene Ther 2001;12). In present study, we injected this vector into the rat striatum to examine the transgene expression profile and the inflammatory response. We also have investigated whether mifepristone-mediated gene switch can be applied in regulating the transgene expression. HdAdv/LacZ vectors were constructed and amplified with the Cre/loxP system as described previously (Mol Ther 2000; 2). Three concentrations of hdAdv/LacZ (1X107, 1X108, and 1X109 particles/ul) were administrated into striatum of rats. After 3days, 7 days, 30days, 60days and 90days post-injection, hdAdv/LacZ expression was quantified by X-gal staining. For the gene switch studies, we have tested the mifepristone-regulated transgene expression in the CNS cell cultures and in animal model study. Different doses of mifepristone were administrated and the transgene expression levels were measured by transgene expression assays. Our results demonstrate that intrastriatal inoculation of hdAdv vector produced a potent transgene expression with minimal inflammatory responses. The hdAdv/lacZ can retrograde transport to the substantia nigra 3-day after intrastriatal injection and last for a long period. The potency of the transgene expression is dose dependent. In in vitro studies, we have found that mifepristone induced a 28-fold higher level of transgene expression in cultures transducted with the gene switch vector, compared with non-mifepristone-treated cultures. The transgene expression levels are mifepristone dose dependent. The results are also confirmed in in vivo study. The preliminary results suggest that mifepristone-induced gene switch system could efficiently induce transgene expression. HdAdv with gene switch system may provide an optimal vector for therapeutic gene delivery for treatment of PD. The next step is to study the therapeutic effects of intrastriatal delivery of hdAdv/GDNF with mifepristone induced gene switch element in PD animal models.