Percutaneous Transendocardial Delivery of Self-complementary Adeno-associated Virus 6 Achieves Global Cardiac Gene Transfer in Canines

Abstract

Achieving efficient cardiac gene transfer in a large animal model has proven to be technically challenging. Prior strategies have employed cardio-pulmonary bypass or dual catheterization with the aid of vasodilators to deliver vectors, such as adenovirus, adeno-associated virus or plasmid DNA. While single stranded adeno-associated virus vectors have shown the greatest promise, they suffer from delayed expression, which might be circumvented by using self-complementary vectors. We sought to optimize cardiac gene transfer using a percutaneous transendocardial injection catheter to deliver adeno-associated virus vectors to the canine myocardium. Four vectors were evaluated—single stranded adeno-associated virus 9, self-complementary adeno-associated virus 9, self-complementary adeno-associated virus 8, self-complementary adeno-associated virus 6—so that comparison could be made between single stranded and self complementary vectors as well as among serotypes 9, 8, and 6. We demonstrate that self-complementary adeno-associated virus is superior to single stranded adeno-associated virus and that adeno-associated virus 6 is superior to other serotypes evaluated. Biodistribution studies revealed that vector genome copies were 15 to 4000 times more abundant in the heart than in any other organ for self-complementary adeno-associated virus 6. Percutaneous transendocardial injection of self-complementary adeno-associated virus 6 is a safe, effective method for achieving efficient cardiac gene transfer.

microRNA122-regulated transgene expression increases specificity of cardiac gene transfer upon intravenous delivery of AAV9 vectors

“…A breakthrough in cardiac gene transfer was achieved with the finding that AAV vectors based on AAV serotypes 6 and 9 allow an efficient cardiac transduction in rodents. 3,10,[12][13][14][15]34 By selection of an AAV cap gene library generated by DNA shuffling of different AAV serotype capsid genes, a novel AAV vector (AAVM41) was identified whose capsid is composed by elements of AAV1, 6, 7 and 8. This vector revealed a similar transgene expression efficiency in murine myocardium as AAV9 but significantly reduced gene transfer into the liver.…”

Adeno-Associated Virus Vectors as Therapeutic and Investigational Tools in the Cardiovascular System

“…92 The same method has recently allowed efficient scAAV6 delivery to the canine heart under fluoroscopic guidance. 93 This approach, however, still holds several limitations, including patchy transduction of a limited number of myocytes and vector delivery to organs other than the heart, because of significant spillage of vectors into the systemic circulation. 93 Because of these overall pitfalls, the most substantial value of intramyocardial injection continues to lie in animal research.…”

Potential of gene therapy as a treatment for heart failure

“…In addition, by avoiding exposure to the blood, deactivation of the vectors by circulating DNases or neutralizing antibodies can be prevented. Furthermore, there is minimal exposure of the vector to off-target organs, although local administration cannot completely avoid some systemic vector distribution (29,30). Low volumes at high vector concentrations may increase the vector retention in the myocardium (29).…”

“…The endocardial approach requires a catheter with a retractable injection needle and imaging guidance modality for determining the injection site (30). This includes electrical mapping systems (32), fluoroscopy (33), echocardiography (34), and magnetic resonance imaging (35).…”