996-13 Inflammation Following Adenovirus-mediated Direct Gene Transfer into Porcine Coronary Arteries and Strategies for Its Control

The vascular response to any given combination of gene transfer vector and catheter delivery system is an important factor to consider in developing gene therapy strategies for preventing coronary restenosis. In order to study the vascular response to adenoviral (Ad5) vectors following transluminal delivery by perforated balloon catheter, we constructed a replicationdeficient Ad5 expressing a nuclear-localized, β -galactosidase and deployed it in porcine coronary arteries using Wolinsky Infusion Catheters (USCI, Billerica, MA). Viral infections were performed under fluoroscopy by infusing 4 ml (2 × 10 10 pfu) of the virus into the coronary arteries of intubated swine at 8 atm of pressure. Three days later, the arteries were removed and fixed prior to a 6 hr incubation in X-gal. The nuclear localization of the indigo reaction product provided for unambiguous detection of Ad5-infected smooth muscle cells in the media; however, specific staining of cells in the near adventitia was also noted suggesting distribution of virus by the vasa vasorum. The endothelial denudation and medial disorganization observed in Ad5-infected arteries were similar to that found in balloon-injured and vehicle-infused control arteries. The most remarkable histologic finding was a pronounced cellular infiltrate in the adventitia and periadventitia of the Ad5-infected arteries that was absent in the vehicle-infused controls. Immunohistochemical staining of arterial cross-sections using a monoclonal antibody directed against the porcine lymphocyte homing receptor (CD44) identified the infiltrating cells as leukocytes. These results suggest that Ad5-mediated gene transfer to the coronary arteries of Hanford miniature swine elicits an inflammatory response mediated by cytotoxic T-cells, monocytes/macrophages, andlor natural killer cells. The natural response of the host to viral infection may therefore contribute to the precipitous decline in Ad5-mediated gene expression observed in this animal model and others. Potential strategies for controlling the inflammatory response to Ad5 vectors will be discussed, including immunosuppression of the host. modifications to the Ad5-genome, and the long-term possibility of using synthetic complexes to emulate vital gene transfer without eliciting inflammation.