Discovery of naturally selected human cardiac tropic Adeno Associated Virus to overcome translational barriers for the use in Cardiac Gene Therapy

Abstract

Cardiac gene therapy has faced a translational barrier since the first clinical trial, as the AAV serotype optimal for pre-clinical studies did not show the same therapeutic benefit in patients. Although the natural adeno-associated virus (AAV) serotypes used in clinical trials are isolated from primates, their isolation methods were through laboratory milieu and further verifications to identify optimal AAV serotypes tends to rely on pre-clinical animals and human cell lines. These conditions might alter the AAV characteristics. Therefore, investigating AAV isolates directly from target human tissues would provide valuable insights into the understanding of human cardiotropic AAV variants and their potential use as clinical vectors. This study aimed to identify latent AAV capsid genomes directly from human ventricular heart tissues due to natural infection, investigate their cellular tropism, and predict their AAV biology for future vector engineering. We identified 14 novel naturally occurring AAV variants from healthy donor hearts using PCR-based screening method. Notably, few of these latent viral genomes remained at levels in human heart tissues that exceeded the therapeutic levels seen in preclinical studies targeting in SERCA2a. Those naturally AAV variants exhibited low transduction in immature human induced pluripotent cells (hiPSC)-derived cardiac cells and targets the same range of cell types as engineered and other natural serotypes. By harnessing machine learning, we predicted important residues associated with high level of latency in human ventricular tissues. These residues located mainly on VP1u and VP1/VP2 common region, which is responsible for AAV infectivity, and may be potential targets for AAV engineering to enhance transduction efficacy as clinical vectors. Although further studies are required to assess these natural AAV isolates as potential clinical vectors, this study represents a step toward targeted cardiac gene therapy.