173. Adenovirus-Mediated Gene Transfer to Mouse and Dog Pancreas In Vivo

Abstract

Helper-dependent adenoviral vectors (HDAd) are attractive vectors for liver-directed gene therapy because they can mediate sustained, high level transgene expression with negligible long-term toxicity. However, high vector doses are required to achieve efficient hepatic transduction by peripheral intravenous injection due to a nonlinear dose response. Unfortunately, such high systemic doses result in wide spread vector dissemination and dose-dependent activation of the acute inflammatory response which can result in severe and lethal acute toxicity. We hypothesize that this problem can be surmounted by delivering the vector exclusively to the liver thereby permitting high efficiency hepatic transduction with low vector doses and with minimal systemic vector dissemination. To test this hypothesis, we injected HDAd directly into the surgically isolated liver via the portal vein in nonhuman primates. Total hepatic isolation was achieved by occluding hepatic blood inflow from the portal vein and hepatic artery and by occluding hepatic blood outflow at the vena cava. Prior to total hepatic isolation, saline was infused into the portal vein to flush blood out of the liver. The vector was then injected directly into the isolated liver via the portal vein and allowed to dwell for 30 min to prolong exposure to hepatocytes. Following the 30 min dwell time, unabsorbed vector was removed from the liver to minimize systemic dissemination. This was accomplished by infusing saline into the portal vein and collecting the unabsorbed vector from a vena cava catheter. We investigated the safety, feasibility and efficacy of this approach and our results revealed that the surgical procedure was well tolerated in nonhuman primates and that significantly higher hepatic transduction efficiencies can be achieved with relatively low vector doses as compared to those obtained by peripheral intravenous injection. This approach may increase the safety and efficacy of HDAd-mediated, liver-directed gene therapy by minimizing the dose required to achieve efficient hepatic transduction and by minimizing systemic vector dissemination.