Abstract 402: Cardiac-Specific Gene Expression after Systemic Administration to Adult Mice Using Pseudotyped AAV Vectors and the Cardiac Troponin-T Promoter: Comparison with Direct Injection
Introduction: AAV serotypes 8 and 9 provide robust, early-onset, cardiac-specific gene expression after direct injection into the adult murine heart. We hypothesized that gene expression could also be restricted to the heart after intravenous (IV) injection in adult mice using a cardiac-specific promoter.
Methods: An AAV-2 ITR based vector carrying firefly luciferase under the control of the cardiac troponin-T promoter was packaged into capsids from AAV serotypes 8 & 9 (AAV2/8 & 2/9). AAV vectors were injected directly into the LV wall (IM) of adult mice (5E+10 viral particles/mouse; n=4) or IV via jugular vein (1E+11 virus particles/mouse; n=4). Transgene expression was monitored by in vivo bioluminescence (IVIS, Xenogen Corp) and in vitro luciferase assays.
Results: Light output was largely restricted to the left side of the chest irrespective of injection route or AAV serotype used (Panel A). In all groups, light output reached half-max by day 7 and steady-state by 3– 4 weeks. After direct injection, little difference in light output was observed by IVIS between AAV2/8 and AAV2/9. However, light output after IV injection at day 14 was 1.9 fold higher with AAV2/9 than AAV2/8 (p<0.05). Multi-organ ex vivo IVIS imaging and in vitro luciferase assays at 6 weeks confirmed that luciferase expression was largely restricted to the heart. In vitro assays showed cardiac luciferase activity with AAV2/9 was 1.6-fold higher by IM and 2.5-fold higher by IV than with AAV2/8 (*p<0.05 vs AAV2/8).
Conclusion: The use of tissue-restricted promoters in combination with highly efficient AAV9 capsids further enhances the potential of AAV vectors for animal experiments and human gene therapy protocols.