Gene Therapy in Lung Transplantation: Feasibility of Ex Vivo Adenovirus-Mediated Gene Transfer to the Graft

Abstract

Lung transplantation is associated with complications such as reperfusion injury and graft rejection. Gene therapy targeted to the graft offers a promising approach to the prevention of these complications. Because adenovirus vectors can transfer genes in vivo to the lung vasculature, we evaluated the feasibility of adenovirus-mediated gene transfer to the lung graft in a porcine model of left lung allotransplantation. Following removal of the donor lung, an adenovirus vector encoding the β-galactosidase (β-Gal) gene was injected ex vivo into the lumen of the upper lobe pulmonary artery of the graft. After 2 hr of incubation at 10°C, the lung graft was implanted into the recipient animal. Three days later, the animals were sacrificed and the lung graft was evaluated for β-Gal activity. No β-Gal activity was detected in the left lower lobe used as a control. In contrast, β-Gal activity was detected in endothelial cells of the left upper lobe pulmonary circulation, and was also observed in airway and alveoli epithelial cells. However, less than 1% of cells of the graft expressed β-Gal. In vitro experiments showed that this may be explained in part by the low temperature and the short duration of adenovirus incubation within the graft, and by the low susceptibility of porcine cells to human adenovirus. Furthermore, expression of the exogenous gene occurred in several organs of recipient animals. Thus, adenovirus-mediated gene transfer to the lung graft is feasible ex vivo, but several parameters limit gene transfer efficiency and need to be improved before clinical application is attempted.

Overview summary

Adenovirus vectors may be an appropriate transfection vehicle for transplanted lungs because they are efficient in transferring genes in vivo to lung vasculature. We evaluated adenovirus-mediated transfer of a reporter gene ex vivo in a model of pig left lung allotransplantation. Gene transfer was feasible in both vascular and epithelial cells of lung graft, but gene transfer efficiency was low, and expression of the exogenous gene occurred in several organs of recipient animals. Variables affecting gene transfer efficiency were evaluated in vitro. These observations underline the potential and the present limits of adenoviruses as tools for gene therapy of lung transplantation.