217. Comparison of Hepatic Vein and Peripheral Vein Delivery of an AAV2/8 Vector Encoding Human a-Galactosidase A to Rhesus Macaques

In murine models of lysosomal storage diseases, sustained hepatocyte-restricted expression and secretion of the therapeutic enzyme is capable of correcting the peripheral pathology associated with the storage product. For example, systemic delivery of a recombinant AAV8 vector encoding human alpha-galactosidase A to Fabry mice resulted in complete clearance of the glycosphingolipid storage product in peripherally affected tissues when sustained serum alpha-galactosidase A levels were in excess of 1 ug/ml. In humans, transient blood levels of human FIX have been obtained after hepatocyte transduction with an AAV2 vector. The abbreviatedexpression was attributed to cytotoxic lymphocyte (CTL) recognition of viral capsid epitopes on the transduced cells. In view of these potential immune-based limitations on expression, we have asked whether we could generate prolonged circulating levels of human alpha-galactosidase A following delivery of an AAV2/8 vector encoding human alpha-galactosidase A under control of a hepatocyte-restricted promoter to immune suppressed rhesus macaques. We have compared systemic delivery using a peripheral vein approach and local delivery using a hepatic vein approach that was developed in a rabbit model. The hepatic vein approach uses a balloon catheter to isolate a lobe of the liver and block blood flow into the vena cava. We then flush the vasculature of the lobe retrograde to blood flow to reduce the concentration of any resident anti-viral antibodies and to allow the viral vector to |[ldquo]|dwell|[rdquo]| within the lobe for a defined period after delivery. A three month immune suppression regime was used to blunt any neutralizing immune responses to virally-transduced cells or human alpha-galactosidase A. After removing immune suppression, animals will be challenged with purified human alpha- galactosidase A to assess their degree of tolerance to this foreign protein. Although this experiment is not yet complete, we will present up-to-date expression and toxicity data comparing the two delivery techniques.