Abstract 713: High-Efficiency, Cardiac-Specific Gene Expression from a Single Intravenous Injection using an AAV-2 Vector Pseudotyped with AAV-1 and -6 Capsids in Combination with the Cardiac Troponin-T Promoter
Introduction: AAV serotype 1 and 6 capsids are known to provide for transgene expression throughout the body after IV injection. We hypothesized that expression could be restricted to the heart by packaging an AAV2 vector carrying the cardiac troponin-T promoter into capsids from AAV1 & 6.
Methods: AAV2 vectors carrying the firefly luciferase gene under control of the cardiac troponin-T (AcTnTLuc) or CMV promoters (ACMVLuc) were packaged into capsids from AAV1, 2 or 6. A total of 1E+11 vector particles were injected into 16 neonatal mice (4 groups of n = 4/group) via jugular vein. Luciferase expression was monitored for 28 days using in vivo bioluminescence imaging (IVIS, Xenogen) followed by ex vivo bioluminescence imaging and in vitro luciferase assays.
Results: Luciferase expression was evident within 3 days after AAV2/1 or 2/6 injection. The ubiquitous CMV promoter yielded luciferase expression throughout the body (Panel A, 2/6ACMVLuc) with highest levels in muscle and liver (Panel B). In contrast, luciferase expression was largely restricted to the heart in mice that received AcTnTLuc (Panel A, 2/6AcTnTLuc, Panel B). In vivo imaging and in vitro luciferase assays showed that AAV1 & 6 capsids were equally efficient, yielding 30-fold more cardiac light output than AAV2 capsids.
Conclusions: Capsids from AAV-1 and 6 deliver genes to the heart more efficiently than conventional AAV-2. When used in combination with a cardiac-specific promoter (e.g., cardiac troponin-T) gene expression from these highly-efficient serotypes can be largely restricted to the mammalian heart to further enhance the potential of AAV vectors for gene transfer experiments and human gene therapy protocols.