Modified infusion procedures affect recombinant adeno-associated virus vector type 2 transduction in the liver

Recombinant adeno-associated virus (rAAV) vectors have therapeutic potential for the treatment of several types of liver diseases including hepato-deficiency disorders. Most of the preclinical and clinical applications involve the use of adeno-associated vector serotype 2 (AAV-2). However, when this vector is delivered at high doses into the portal vein or hepatic artery, a relatively small number of hepatocytes are stably transduced. We elected to determine if the route of vector administration and altering the vascular delivery route within the liver influenced the relative level of transduction. First, we delivered an AAV vector expressing the human factor IX gene from a liver-specific promoter into the hepatic artery, portal vein, or general circulation of rats. Transgene expression was equal with hepatic artery and portal vein infusion, which was higher than vector administered via peripheral venous infusion. Next, we determined how localized perfusion or changing the vector dwell time affected AAV transduction in vivo. To do this, we infused an AAV vector lacking a functional expression and quantified transduction by quantifying the number of double-stranded vector DNA genomes. By increasing vector dwell time in the liver to 5 min, vector transduction was enhanced approximately 4- to 5-fold. To establish if gene transduction could be restricted to a specific anatomic location in the liver, we delivered vector into specific liver lobes by clamping the venous inflow to the middle and left liver lobes (noninfused lobes) and infusing vector into the right two liver lobes through the hepatic artery followed by vector circulation between the two right lobes and general circulation for 5 min. With this selective infusion, 40 to 120 times higher vector genome was observed in the perfused lobes than the nonperfused lobes. All the procedures described in this study were performed without detectable liver injury or toxicity. In all, the present study clearly demonstrated that hepatic arterial infusion of rAAV is effective for liver-directed gene therapy and that other parameters related to blood flow can be adjusted to further optimize gene transfer.