Rational Design and Engineering of a Modified Adeno-Associated Virus (AAV1)-Based Vector System for Enhanced Retrograde Gene Delivery

BACKGROUND: After injection into muscle and peripheral nerves, a variety of viral vectors undergo retrograde transport to lower motor neurons. However, because of its attractive safety profile and durable gene expression, adeno-associated virus (AAV) remains the only vector to have been applied to the human nervous system for the treatment of neurodegenerative disease. Nonetheless, only a very small fraction of intramuscularly injected AAV vector arrives at the spinal cord. OBJECTIVE: To engineer a novel AAV vector by inserting a neuronal targeting peptide (Tet1), with binding properties similar to those of tetanus toxin, into the AAV1 capsid. METHODS: Integral to this approach was the use of structure-based design to increase the effectiveness of functional capsid engineering. This approach allowed the optimization of scaffolding regions for effective display of the foreign epitope while minimizing disruption of the native capsid structure. We also validated an approach by which low-titer tropism-modified AAV vectors can be rescued by particle mosaicism with unmodified capsid proteins. RESULTS: Importantly, our rationally engineered AAV1-based vectors exhibited markedly enhanced transduction of cultured motor neurons, diminished transduction of nontarget cells, and markedly superior retrograde delivery compared with unmodified AAV1 vector. CONCLUSION: This approach promises a significant advancement in the rational engineering of AAV vectors for diseases of the nervous system and other organs.