102. Catheter-Based Intrahepatic rAAV Gene Delivery: Influence of Infusion Flow Rate and Volume on Uptake

Abstract

Catheter-based, fluoroscopy-aided interventional radiology approaches have been utilized in a variety of clinical applications. Safe, consistent and efficient methods for liver directed gene delivery need to be developed. In this study, we examined the effects of infusion flow rate and infusion volume on intrahepatic catheter-based delivery of recombinant adeno-assocated virus 2 vectors (rAAV2) in dogs. To study the efficiency of intrahepatic gene transfer, vector (rAAV-lac Z (nonfunctional promoter)) was delivered through the hepatic artery with an occlusion balloon catheter with a protocol mimicking the clinical angiography procedure of an ongoing clinical gene transfer study in hemophilia B subjects. Three groups of beagle dogs (n=5/group) utilizing three different intrahepatic injection parameters were utilized: A) 8 ml injected at 0.1 ml/min/kg (most similar to ongoing clinical trial), B) 8 ml injected at 8 ml/min/kg and C) 40 ml injected at 8 ml/min/kg. Reproducibility and extent of gene transfer was studied by determining vector distribution and vector copy number in the liver, including individual lobes, 4 weeks post injection. Quantitative PCR using linearized standards was employed to examine vector levels in the liver. Liver histology, serum chemistries and hematology parameters were also examined in all animals over the course of 4 weeks to determine the safety of the various delivery parameters. The results indicate that intrahepatic transgene delivery was influenced by the infusion rate. On average, the rAAV2 copy number per hepatocyte with fast infusion was twice that of slow infusion (e.g. 2.8 copy/cell group B vs 1.4 copy/cell group A). Likewise, vector copy numbers per liver were approximately two times higher in the fast infusion groups (p=0.04, one-way ANOVA). Groups B (higher rate) and C (higher rate and higher volume) did not significantly differ. AAV2 vector tended to be more evenly distributed in individual livers in the fast infusion groups. No changes in chemistries nor hematology values were detected in any dogs over the course of study. Histological analysis of the liver for capsid immunoflourescence is ongoing. This study demonstrates that the infusion flow rate, in particular, can be an important variable in efficient and safe hepatic delivery of AAV.