Correction of the Biochemical and Functional Deficits in Fabry Mice Following AAV8–mediated Hepatic Expression of α-galactosidase A

The advent of novel adeno-associated virus (AAV) serotype vectors with higher transduction activity has encouraged a re-evaluation of the merits of this delivery platform for a variety of diseases. We report here that administration of a recombinant AAV8–based serotype vector encoding human α -galactosidase A into Fabry mice facilitated more rapid and significantly higher levels of production of the enzyme than an AAV2 vector. This translated into improved clearance of globotriaosylceramide, the glycosphingolipid that accumulates in the lysosomes of affected Fabry cells, and to correction of the peripheral neuropathy shown associated with this disease. The higher levels of α -galactosidase A expression also allowed for a more rapid induction of immunotolerance to the enzyme. Recombinant AAV8 vectors that facilitated hepatic–restricted expression of high levels of α -galactosidase A conferred immunotolerance to the expressed enzyme as early as 30 days post-treatment. Animals expressing lower levels of the hydrolase, such as those treated with an AAV2–based vector or with lower doses of the AAV8–based vector, were also able to develop immunotolerance, but only after a more extended time period. Adoptive transfer of T cells isolated from the spleens of immunotolerized mice suppressed the formation of antibodies in naive recipient animals, suggesting the possible role of regulatory T cells in effecting this state.