Abstract 4904: Comparative Anti-atherogenic Effects of a Single Intravenous Injection of rAAV8 Or rAAV2 Encoding Apo A-IMilano Gene
Background: We previously reported potent anti-atherogenic effects of gene transfer of Apo A-IMilano through transplant of retrovirally transduced bone marrow. In anticipation of potential evaluation of Apo A-IMilano gene transfer in human atherosclerosis, we evaluated the comparative anti- atherogenic efficacy of Apo A-IMilano gene transfer using intravenous injection of type-2 and type-8 recombinant adeno-associated viruses (rAAV2 and rAAV8) as vectors in Apo A-I/apo E null mice.
Methods: Mice received one intravenous injection of 1.2×1012 vector genome copies of rAAV2 -Milano or rAAV2 -Control or rAAV8 -Milano or rAAV8 -Control (12 mice per group). Four weeks after injection mice were placed on high fat diet. Twenty weeks later mice were euthanized to analyze Apo A-IMilano gene expression and quantitative extent of aortic atherosclerosis after oil-red O staining. ELISA analysis of blood samples and real-time PCR analysis of target organs was used to determine the Apo A-IMilano gene expression. Blood was analyzed for cholesterol levels.
Results: The circulating cholesterol levels were comparably elevated among the 4 groups. Serum Apo A-IMilano levels were significantly higher in rAAV8 -Milano injected mice compared to rAAV2 -Milano injected mice at 4 weeks (71 ± 31 ng/ml vs. 31 ± 21ng/ml) 12 weeks (92 ± 61 ng/ml vs. 30 ± 27), and at 24 weeks (45 ± 32 ng/ml vs. 7.6 ± 6 ng/ml) (P <0.001 all groups). Real time PCR showed a significantly higher level of transgene expression in the heart (122 ± 36 fold), liver (32 ± 25 fold) and the brain (14 ± 0.39 fold) with rAAV8 -Milano compared to rAAV2 -Milano. Compared to rAAV8 -Control, the mean aortic lesion area was reduced by 42% by rAAV8 -Milano (7.7 ± 0.06% vs 13.4 ± 1.1 % of aorta; p = 0.001). Compared to rAAV2-Control, the mean aortic lesion area was reduced by 16% by rAAV2 -Milano (12.6 ± 0.8 vs 10.6 ± 0.8 % of aorta; p = NS). rAAV8 -Milano reduced lesion area by 27% compared to rAAV2 -Milano (p = 0.01).
Conclusions: Intravenous rAAV8 -Milano results in higher in-vivo transgene expression and a significantly greater reduction in aortic atherosclerosis compared to vector control or rAAV2 -Milano.