Improved vascular gene transfer with a helper-dependent adenoviral vector

Abstract

Background-Adenoviral vectors are the most widely used agents for vascular gene transfer. However, the utility of adenoviral vectors for vascular gene transfer is limited by brevity of expression and by the induction of a significant host inflammatory response. Third-generation or "helper- dependent" adenoviral vectors have achieved prolonged recombinant gene expression in liver and muscle with minimal associated inflammation; however, they have never been tested for vascular gene transfer. Methods and Results-We constructed a helper-dependent adenoviral vector expressing rabbit urokinase plasminogen activator (HD-AduPA). HD-AduPA was compared, in a rabbit model of carotid gene transfer, with a first-generation adenovirus, also expressing rabbit uPA (FG-AduPA). uPA expression and vector DNA were measured in arteries harvested from 3 to 56 days after gene transfer. Vector-specific mRNA, vascular inflammation, and neointimal formation were assessed 14 days after gene transfer. uPA expression was lost, and vector DNA declined rapidly in arteries infused with FG-AduPA. In contrast, uPA expression and vector DNA persisted in HD-AduPA arteries for ≥56 days, with stable expression from 14 to 56 days. Increased uPA expression in HD-AduPA arteries was accompanied by high levels of vector-specific uPA mRNA. Moreover, HD-AduPA arteries had significantly less inflammation and neointimal formation than FG-AduPA arteries. Conclusions-Helper-dependent adenoviral vectors can stably express a therapeutic gene in the vascular wall for ≥8 weeks, with minimal associated inflammation. Helper-dependent adenoviral vectors will be useful agents for vascular gene transfer and gene therapy.