Purpose: Adenovirus-mediated arterial gene transfer is a promising tool in
the study of vascular biology and the development of vascular gene therapy.
However, intraluminal delivery of adenoviral vectors causes vascular infla
mmation and neointimal formation. Whether these complications could be avoi
ded and gene transfer efficiency maintained by means of delivering adenovir
al vectors via the adventitia was studied.
Methods: Replication-defective adenoviral vectors encoding a beta-galactosi
dase (beta-gal) gene (AdRSVnLacZ) or without a recombinant gene (AdNull) we
re infused into the lumen or the adventitia of rabbit carotid arteries. Two
days after infusion of either AdRSVnLacZ (n = 8 adventitial, n = 8 luminal
) or AdNull (n = 4 luminal), recombinant gene expression was quantitated by
histochemistry (performed on tissue sections) and with a beta-gal activity
assay (performed on vessel extracts). Inflammation caused by adenovirus in
fusion was assessed 14 days after infusion of either AdNull (n = 6) or vehi
cle (n = 6) into the carotid adventitia. Inflammation was assessed by means
of examination of histologic sections for the presence of neointimal forma
tion and infiltrating T cells and for the expression of markers of vascular
cell activation (ICAM-1 and VCAM-1). To measure the systemic immune respon
se to adventitial infusion of adenovirus, plasma samples (n = 3) were drawn
14 days after infusion of AdNull and assayed for neutralizing antibodies.
Results: Two days after luminal infusion of AdRSVnLacZ, approximately 30% o
f luminal endothelial cells expressed beta-gal. Similarly, 2 days after inf
usion of AdRSVnLacZ to the adventitia, approximately 30% of adventitial cel
ls expressed beta-gal. beta-gal expression was present in the carotid adven
titia, the internal jugular vein adventitia, and the vagus nerve perineuriu
m. Elevated beta-gal activity (50- to 80-fold more than background; P < .05
) was detected in extracts made from all AdRSVnLacZ-transduced arteries. Th
e amount of recombinant protein expression per vessel did not differ signif
icantly between vessels transduced via the adventitia (17.1 mU/mg total pro
tein [range, 8.1 to 71.5]) and those transduced via a luminal approach (10.
0 mU/mg total protein [range, 3.9 to 42.6]). Notably, adventitial delivery
of AdNull did not cause neointimal formation. In addition, vascular inflamm
ation in arteries transduced via the adventitia tie, T-cell infiltrates and
ICAM-1 expression) was confined to the adventitia, sparing both the intima
and media. Antiadenoviral neutralizing antibodies were present in all rabb
its after adventitial delivery of AdNull.
Conclusion: Infusion of adenoviral vectors into the carotid artery adventit
ia achieves recombinant gene expression at a level equivalent to that achie
ved by means of intraluminal vector infusion. Because adventitial gene tran
sfer can be performed by means of direct application during open surgical p
rocedures, this technically simple procedure may be more clinically applica
ble than intraluminal delivery. Moreover, despite the generation of a syste
mic immune response, adventitial infusion had no detectable pathologic effe
cts on the vascular intima or media. For these reasons, adventitial gene de
livery may be a particularly useful experimental and clinical tool.