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A - Viral Vector Development -> AAV Vectors – Virology and Vectorology

Evolving AAV Capsids with Broad Biodistribution in Deep Brain Structures in Adult Rhesus Macaques

Type: Oral Abstract Session

Presentation Details
Session Title: Late-Breaking Abstracts II
Location: Ballroom C
Start Time: 5/18/2022 9:15
End Time: 5/18/2022 9:30

Huntington’s disease (HD) is a hereditary neurodegenerative disease that primarily affects an interconnected network of brain areas including the basal ganglia and cerebral cortex. While we and others have developed adeno-associated virus (AAV) gene therapy approaches for HD, current state-of-the-art AAV capsids do not sufficiently target all primate brain areas critical for HD therapy. To overcome this challenge, we performed a screen of tens of millions of peptide-modified AAV capsid variants in rhesus macaques to identify novel variants that transduced multiple basal ganglia and cortical areas following a single focused infusion. The goal of our approach was to take advantage of network connectivity in the brain to aid in AAV biodistribution. After three rounds of selection, next-generation sequencing revealed the top-performing capsid variants. We selected six variants for further validation by packaging one of five reporter transgenes. Mixes of top AAVs were infused unilaterally in two rhesus macaques at relatively low doses (3.5E10-7.0E10 vector genomes each, or 4.6E9-1.3E10 vector genomes per kilogram), and tissue was collected for histology after three weeks. Multiple variants showed robust and widespread transduction in the caudate nucleus, putamen, globus pallidus, and substantia nigra. One capsid variant targeted these brain areas with remarkable efficiency and also layer V/VI projection neurons across multiple cortical areas, including primary motor cortex. Brain biodistribution was corroborated using RNAscope™ fluorescence in situ hybridization. To test for AAV transduction outside of the central nervous system, digital droplet PCR was performed on liver samples. Notably, and in contrast to animals receiving intracerebroventricular infusions of a commonly used parental AAV serotype, AAV genomes were below the detection threshold with no transgene expression observed. Taken together, we identified novel AAV capsid variants that efficiently target basal ganglia and cortical projection neurons following focal infusion in rhesus macaques, with delivery at doses orders of magnitude lower than currently in clinical and preclinical use. These capsid variants may be useful for delivery of therapeutic transgenes for HD as well as Parkinson’s disease and other disorders affecting the basal ganglia.

David E. Leib1, Megan S. Keiser1, Yong Hong Chen1, Paul T. Ranum1, Luis Tecedor1, Congsheng Cheng1, Laurence A. Busque1, Beverly L. Davidson1,2

1The Raymond G. Perelman Center for Cellular and Molecular Therapeutics, Children's Hospital of Philadelphia, Philadelphia, PA,2Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA
 D.E. Leib: None.

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