rAAV-Mediated Gene Transfer For Study of Pathological Mechanisms and Therapeutic Intervention in Canavan's Disease: A Dissertation

Canavan’s Disease is a fatal Central Nervous System disorder caused by genetic defects in the enzyme – aspartoacylase and currently has no effective treatment options. We report additional phenotypes in a stringent preclinical aspartoacylase knockout mouse model. Using this model, we developed a gene therapy strategy with intravenous injections of the aspartoacylase gene packaged in recombinant adeno associated viruses (rAAVs). We first investigated the CNS gene transfer abilities of rAAV vectors that can cross the blood-brain-barrier in neonatal and adult mice and subsequently used different rAAV serotypes such as rAAV9, rAAVrh.8 and rAAVrh.10 for gene replacement therapy. A single intravenous injection rescued lethality, extended survival and corrected several disease phenotypes including motor dysfunctions. For the first time we demonstrated the existence of a therapeutic time window in the mouse model. In order to limit off-target effects of viral delivery we employed a synthetic strategy using microRNA mediated posttranscriptional detargeting to restrict rAAV expression in the CNS. We followed up with another approach to limit peripheral tissue distribution. Strikingly, we demonstrate that intracerebroventricular administration of a 50-fold lower vectors dose can rescue lethality and extend survival but not motor functions. We also study the contributions of several peripheral tissues in a primarily CNS disorder and examine several molecular attributes behind pathogenesis of Canavan’s disease using primary neural cell cultures. In summary, this thesis describes the potential of novel rAAV-mediated gene replacement therapy in Canavan’s disease and the use of rAAVs as a tool to tease out its pathological mechanism.