Focused Ultrasound-Mediated Disruption of the Blood-Brain Barrier for AAV9 Delivery in a Mouse Model of Huntington's Disease.

Authors: Owusu-Yaw BS, Zhang Y, Garrett L, Yao A, Shing K, Batista AR, Sena-Esteves M, Upadhyay J, Kegel-Gleason K, Todd N

Huntington's disease (HD) is a monogenic neurodegenerative disorder caused by a cytosine-adenine-guanine (CAG) trinucleotide repeat expansion in the <i>HTT</i> gene. There are no cures for HD, but the genetic basis of this disorder makes gene therapy a viable approach. Adeno-associated virus (AAV)-miRNA-based therapies have been demonstrated to be effective in lowering HTT mRNA; however, the blood-brain barrier (BBB) poses a significant challenge for gene delivery to the brain. Delivery strategies include direct injections into the central nervous system, which are invasive and can result in poor diffusion of viral particles through the brain parenchyma. Focused ultrasound (FUS) is an alternative approach that can be used to non-invasively deliver AAVs by temporarily disrupting the BBB. Here, we investigate FUS-mediated delivery of a single-stranded AAV9 bearing a cDNA for GFP in 2-month-old wild-type mice and the zQ175 HD mouse model at 2-, 6-, and 12-months. FUS treatment improved AAV9 delivery for all mouse groups. The delivery efficacy was similar for all WT and HD groups, with the exception of the zQ175 12-month cohort, where we observed decreased GFP expression. Astrocytosis did not increase after FUS treatment, even within the zQ175 12-month group exhibiting higher baseline levels of GFAP expression. These findings demonstrate that FUS can be used to non-invasively deliver an AAV9-based gene therapy to targeted brain regions in a mouse model of Huntington's disease.

Introduction

Purpose Drug delivery with BBB opening

Study Objective To evaluate whether focused ultrasound-mediated blood–brain barrier disruption can noninvasively enhance delivery and expression of AAV9-based gene therapy in wild-type and zQ175 Huntington’s disease mice across different ages.

Animal model / Human subject Mouse (Mus musculus); strains: wild-type and zQ175 (Huntington’s disease model); ages: WT 2 months; zQ175 2, 6, and 12 months; sex: not reported

Disease model Huntington's disease

MRI or image guidance method MRI imaging

Targeted brain region(s) Caudate Putamen

Cargo name and characteristics Single-stranded AAV9 viral vector carrying a cDNA encoding GFP (AAV9 gene therapy vector expressing green fluorescent protein)

Route of administration Intravenous

Outcomes and Safety

Summary of Outcomes Focused ultrasound (FUS) noninvasively enhanced delivery of AAV9-GFP to targeted brain regions in wild-type and zQ175 Huntington’s disease mice at 2, 6, and 12 months, with similar efficacy across groups except for reduced GFP expression in the zQ175 12-month cohort; FUS did not increase astrocytosis (GFAP). No multiple FUS parameter variations were reported.

Duration of biological effect 3 weeks

Safety-related matter Astrocytosis did not increase after FUS treatment, including in the zQ175 12-month group with higher baseline GFAP, and no adverse effects were reported.

Brain Region

Ultrasound Parameters

Ultrasound instrument Single-element focused ultrasound transducer

FUS Frequency 690 kHz

FUS Pressure 0.34 Mpa

FUS Mode pulsed

Pulse duration 10 ms

Duration of a single FUS session 120 s

Focal Characteristics Focal depth: 3.5 cm; Focal length: None; Aperture size: 4 cm

Treatment frequency single

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