Abstract 403: Direct Comparison Of Adeno-associated Viral Vectors Serotypes 1–9 Transduction In Mouse Heart After Cardiac Gene Delivery
Cardiac gene therapy is an attractive tool for developing novel heart disease treatments. Adeno-associated viral vectors (AAV) are widely used to mediate transgene expression in the heart and are being evaluated for human gene therapy. These small non-enveloped single-stranded DNA viruses have been associated with long duration expression in experimental animals, and this makes AAV serotypes ideal vectors for gene delivery. However, it is not clear which serotype displays the best tropism based on expression and selectivity for cardiac tissue. For this aim we have directly compared AAV serotypes 1–9 transduction efficiency in the mouse heart after indirect intra-coronary injection. AAV-CMV-luciferase serotypes 1–9 (1.3x1010 viral genomes) and saline (control) were injected in the left ventricular cavity of 10-week-old Balb/c mice after cross-clamping of the ascending aorta and pulmonary artery. An IVIS100 Imaging System was used to visualize luciferase expression at 3, 7, 21, 70, or 140 days post-injection. Basal and Stress Echocardiography were performed to evaluate cardiac function on day 140. Luciferase protein and genome copies of the different AAV-serotypes were assessed in heart, liver, lung, skeletal muscle, brain, kidney and testes at the end of the study. Potential AAV immunogenicity was evaluated on heart sections by staining for F4/80 (macrophages) and CD3 (T and B lymphocytes). Luciferase expression was already detectable on day 3 and it had a time-dependent increase up to day 140. Our data indicated that among the viral serotypes, AAV6 was the most cardio-selective with no detectable expression in other organs, whereas all the other serotypes showed ectopic expression, especially in the liver. None of the serotypes tested had any effect on cardiac function as evaluated with echocardiography, either basally or after stimulation with isoproterenol. In addition, AAV expression was not associated with cardiac inflammation. Taken together, our results show that AAV serotypes mediate long-term expression and, among the various serotypes tested, AAV6 has the best capability of achieving high transduction levels in the myocardium in a tissue-specific manner upon cardiac gene delivery.