Ex Vivo Intracoronary Gene Transfer of Adeno Associated Virus Serotype 2 Is Superior to Serotypes 8 and 9 in Transfecting Heart Transplants in the Rat

Purpose Comparison of transgene expression, localization, kinetics, and efficiency of adeno-associated virus 2 (AAV2) and novel AAV8 and AAV9 in syngenic heart transplants. Methods and Materials After harvest, the coronary arteries of donor hearts were perfused with AAV2, AAV8 or AAV9 vectors encoding firefly luciferase (Luc). The recipients were subjected to non-invasive bioluminescent imaging (IVIS) from 2 days up to 24 weeks after transplantation. Luciferase expression was quantified with Living Image 2.50 software. RT-PCR and luminometer analysis was used to localize transgene expression ex vivo. Results Luciferase expression peaked at 4 to 8 weeks and remained stable for 6 months. IVIS revealed that the luciferase signal was 10x stronger in the AAV9 group compared to AAV2, and mainly localized to the recipient abdominal region ( Figure 1 A). However, ex vivo PCR- and luminometer analysis of syngraft samples revealed that cardiac luciferase DNA, mRNA and protein activity was far greater in the AAV2 group than in the AAV9 and AAV8 group ( Figure 1 B-D). Conclusions Ex vivo intracoronary delivery of AAV2 results in efficient transgene expression in cardiac syngrafts, whereas AAV9 transfects adjacent tissues. These results highlight the importance of delivery route on heart transplant gene therapy, and underline the weaknesses of bioluminiscent imaging in transgene localization. Also, we have shown that intracoronary delivery of AAV2, -8 or -9 does not induce pro-inflammatory or pro-fibrotic changes in syngrafts. Our ongoing research will investigate how these vectors behave in an allogenic heart transplantation model.