Abstract 405: Ultrasound-Targeted Microbubble Destruction augments Adeno-Associated Virus (AAV)-Mediated Cardiac Gene Transfer after Systemic Administration in Adult Rats
Background: AAV-6 or AAV-9 pseudotyped vectors are suitable for an efficient cardiac gene transfer upon intravenous injections in mice. However, a systemic application in larger organisms such as rats is limited by higher doses of vector. Furthermore, an intravenous delivery may lead to potential side-effects in other organs. Therefore, aim of our study was to analyse whether ultrasound-targeted microbubble destruction is able to target cardiac tranduction after intravenous vector administration in rats.
Material and Methods: The ability of AAV vectors to be loaded on lipid stabilized microbubbles was shown by localization of intact AAV particles on the bubble surface using immunofluourescence. In order to analyze efficiency and specificity of gene transfer, microbubbles loaded with 4x10(10) genomic particles of AAV6 or AAV9 harbouring a luciferase reporter gene under the control of a CMV-enhanced 1.5 kb myosin-light chain promoter were infused into the jugular vein of adult (250g) Sprague-Dawley rats. During the infusion, high mechanical index ultrasound was administered to the heart. After 4 weeks, organs were harvested and analyzed for reporter gene expression.
Results: In contrast to low cardiac expression after systemic transfer of the vector solution without ultrasound, ultrasound-mediated destruction of microbubbles significantly increased cardiac reporter activities between 6- and 20-fold. In contrast to previous observations in mice, no significant difference was found between AAV-6 and AAV-9 pseudotyped vectors. Specificity of gene transfer was also increased since background activities in extracardiac organs such as liver were similar with or without ultrasound. Analyzing the spatial distribution with 1011 genomic particles of AAV-9 vectors with an EGFP reporter gene, more than 20% EGFP positive cells in ventricular myocardium using this approach.
Conclusion: In conclusion, ultrasound-targeted microbubble destruction augments cardiac gene transfer with AAV-6 or AAV-9 serotype vectors in rats. This approach may be suitable also for increasing efficiency and specificity of AAV-mediated gene transfer in larger species and holds promise for human gene therapy.