Quantitative Analysis of Repeat Adenovirus-Mediated Gene Transfer Into Injured Canine Femoral Arteries

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Abstract
We quantitatively evaluated the effectiveness of a repeat administration of a recombinant adenoviral vector expressing bacterial Escherichia coli lacZ into the same arterial site of a relatively large animal, the dog. The replication-defective adenoviral vector was introduced percutaneously into balloon-injured femoral arteries through a double-balloon catheter. After a single dose of adenoviral vector, up to 90% of surface (73±16%, n=7) and smooth muscle cells in multiple layers of the media showed transgene expression as evaluated by 5-bromo-4-chloro-3-indoyl β- d -galactopyranoside histostaining without extralocal expression, as assessed by polymerase chain reaction. High-level expression (measured as β-galactosidase activity) peaked 7 days after transfer and was transient, although it was retained for a month. Second doses of the same adenovirus to the same arterial site were given 1, 2, 5, or 8 weeks after the first administration. At 1 week the second dose significantly enhanced lacZ expression. At 2, 5, or 8 weeks the second dose reinduced lacZ expression at 25% to 30% of the full expression. lacZ expression was also detected in preimmuned dogs, although the expression levels correlated inversely to the titer of neutralizing antibodies in their serum. These results demonstrate that arterial gene expression can be enhanced by a second administration of the same adenovirus after a short interval and that a repeat dose after a long interval partially but significantly reinduces gene expression despite the presence of an immune response. These data may provide an additional scientific foundation for the use of adenovirus-mediated arterial gene transfer in future clinical practice.