Exploring the potential of cell-derived vesicles for transient delivery of gene editing payloads

Abstract: Machado-Joseph disease (MJD) is the most common dominant autosomal inherited ataxia worldwide, caused by the over-repetition of the trinucleotide CAG in the ATXN3 gene. This leads to the accumulation of ataxin-3 protein and neurodegeneration. Currently, treatment remains symptomatic, though gene therapy has emerged as a promising approach. However, efficient and minimally invasive delivery to the brain remains a challenge. Extracellular vesicle-associated adeno-associated vectors (EV-AAVs) are a novel delivery system, combining AAVs' ability to deliver genes with extracellular vesicles' capacity to bypass the immune system and cross the blood-brain barrier (BBB). Previous studies, however, have only combined AAV serotypes known to efficiently cross the BBB with EVs as a non-invasive delivery system to the brain. Thus, the ability of EV-AAVs to cross the BBB remained inconclusive. In this study we evaluated whether AAV1/2 serotype, combined with rabies virus glycoprotein (RVg)-coated EVs, could effectively target the brain. Two isolation methods, differential ultracentrifugation and size exclusion chromatography (SEC) were compared, with SEC yielding higher EV recovery. Moreover, RVg-EV-AAV1/2 successfully crossed the BBB and transduced mouse brains, leading to motor and neuropathological improvements in an MJD mouse model. This study demonstrates that RVg-EV-AAVs are promising non-invasive delivery systems for MJD gene therapy.

TL;DR: An overview of clinical trials for CNS disorders using AAVs is presented and preclinical studies based on the systemic gene delivery using Aav9 are focused on, opening the way to the first clinical trial in the field.