Calcium phosphate precipitates augment adenovirus-mediated gene transfer to blood vessels in vitro and in vivo

Adenovirus (Ad)-mediated gene transfer to blood vessels is relatively ineff icient, probably because binding of adenovirus to the endothelium and adven titia seems to be limited. Association of calcium phosphate (CaPi) precipit ates with adenovirus improves efficiency of gene transfer to some cells in culture and to mouse lung in vivo. In this study, we tested the hypothesis that CaPi is useful for adenovirus-mediated gene transfer to blood vessels. In fibroblast and endothelial cells in culture, Ad:CaPi coprecipitates gre atly increased transgene expression. Ad:CaPi also enhanced transgene expres sion in both adventitia and endothelium of carotid arteries and aortae from rabbits studied ex vivo. After injection of Ad:CaPi into the cisterna magn a of rabbits in vivo, the transgene product was markedly increased in lepto meninges of the ventral brain stem, including the adventitia of the basilar artery. We also examined mechanisms of enhanced gene transfer. Binding of adenovirus to fibroblast and endothelial cells in culture, and to the basil ar artery in vivo, as determined using Southern blot analysis, was augmente d by CaPi. Antibody to adenoviral fiber knob did not inhibit augmented tran sgene expression by Ad:CaPi. The finding suggests that improved adenoviral binding occurs primarily via a fiber-independent pathway. Thus, CaPi precip itates are useful for improvement of adenovirus-mediated gene transfer to b lood Vessels in vitro and in vivo.