AAV8-U6-shRNA-tdTOMATO

AAV is a single-stranded DNA virus that is commonly used as a non-pathogenic recombinant vector for gene delivery. Over the past two decades, AAV-based gene therapy has rapidly developed for use in many planned or ongoing clinical trials. Twelve AAV serotypes and more than 100 variants (including many genetically engineered mutants) have been identified and used as gene delivery vectors. These AAV vectors have been extensively studied in a variety of animal models, including rodents, dogs, and non-human primates. In animal model studies, different AAV serotypes show different tropisms for tissues and organs. Identifying the appropriate AAV vector for a specific tissue or cell is critical for successful gene therapy.

The success of AAV as a leading gene delivery modality is based on a number of factors: (i) even wild-type AAV has not been shown to cause any disease, (ii) in contrast to other currently available gene delivery methods, AAV results in long-term expression of therapeutic payloads in non-dividing or very slowly dividing cells, even though AAV vector DNA is primarily present as extrachromosomal episomes, and (iii) AAV vectors are not strongly immunogenic, most likely because the only viral elements in the therapeutic AAV genome are two inverted terminal repeats. As a result, AAV vectors do not express any viral proteins, which greatly reduces the presentation of viral peptides on the MHCI complex, thereby greatly reducing the incidence and magnitude of cellular immune responses against transduced cells.