Poster abstracts

Poster number 96 submitted by Jessica Herstine

Astrocyte-targeted gene therapy demonstrates efficacy in two murine models of Vanishing White Matter disease

Jessica A. Herstine (MCDB), Sergiy Chornyy, Jessica Rediger, Nettie Pyne, Caleb Holaway, Alex Sunshine (Center for Gene Therapy, The Abigail Wexner Research Institute at Nationwide Childrens Hospital, Columbus, OH), Tatyana Vetter, Kevin Flanigan (Center for Gene Therapy, The Abigail Wexner Research Institute at Nationwide Childrens Hospital, Columbus, OH), Pi-Kai Chang, Julia Wentz, Erika Scholl, Tamara Stevenson (Department of Pediatrics, University of Utah, Salt Lake City, UT), Joshua Bonkowsky (Department of Pediatrics, University of Utah, Salt Lake City, UT)

Abstract:
Vanishing White Matter Disease (VWM) is a neurodegenerative leukodystrophy that most commonly occurs in children and presents with ataxia, spasticity, neurological decline, and seizures which lead to premature death1,2. Currently there are no treatments. VWM is caused by autosomal recessive loss of function mutations in the subunits of eukaryotic initiation factor 2B (EIF2B) with pathologic variants commonly occurring in EIF2B53. Due to VWM’s monogenic nature, it is a good candidate for adeno-associated virus (AAV)-mediated gene replacement therapy. VWM pathology suggests that astrocytes are a critical target, as their differentiation, morphology, and function is impaired, thus mediating disease progression4,5. Therefore, we designed gene replacement constructs to compare astrocyte-specific or ubiquitous expression. Intracerebroventricular injections of our GFP vectors into wild-type mice revealed that astrocyte-specific reporters (AAV9.GFAP.GFP and AAV9.gfaABC1D.GFP) appropriately targeted astrocytes, with our AAV9.GFAP.GFP vector having significantly greater neuraxial distribution compared to truncated or ubiquitous counterparts (AAV9.gfaABC1D.GFP and AAV9.CAG.GFP). To increase biodistribution while staying within the size constraints of AAV, we created a novel intermediate gfaABCD1405 promoter with preliminary studies demonstrating biodistribution comparable to GFAP. To evaluate potential therapeutic efficacy, we generated four AAV constructs driving expression of the EIF2B5 transgene. Evaluation of said vectors in two murine models of VWM is ongoing. Current data suggests that our astrocyte-targeted gene therapy can delay disease progression and significantly increase latency to fall on rotarod in both models. Overall, we anticipate emergence of a lead candidate in which the data will be strengthened through the evaluation of clinically relevant measures allowing for timely translation to the clinic.

References:
1. Van Der Knaap, M. S. et al. A new leukoencephalopathy with vanishing white matter. Neurology 48, 845–855 (1997).
2. Hamilton, E. M. C. et al. Natural History of Vanishing White Matter. Ann. Neurol. 84, 274–288 (2018).
3. Fogli, A. et al. The effect of genotype on the natural history of eIF2B-related leukodystrophies. Neurology 62, 1509–1517 (2004).
4. Bugiani, M., Vuong, C., Breur, M. & van der Knaap, M. S. Vanishing white matter: a leukodystrophy due to astrocytic dysfunction. Brain Pathol. 28, 408–421 (2018).
5. Dooves, S. et al. Astrocytes are central in the pathomechanisms of vanishing white matter. J. Clin. Invest. 126, 1512–1524 (2016).

Keywords: Leukodystrophy, Astrocytes, AAV Gene Replacement Therapy