Poster abstracts

Poster number 90 submitted by Jessica Herstine

Defining the therapeutic ceiling of astrocytic gene therapy for vanishing white matter disease

Jessica A. Herstine (Molecular, Cellular, and Developmental Biology Graduate Program), Meng Weng (Steve and Cindy Rasmussen Institute for Genomic Medicine, The Abigail Wexner Research Institute at Nationwide Childrens Hospital), Sergiy Chornyy, Jan Kubacek, Abigail Hetterscheidt, Nettie Pyne (Jerry R. Mendell Center for Gene Therapy, The Abigail Wexner Research Institute at Nationwide Childrens Hospital), Tamara J. Stevenson, Julia Wentz, Joshua L. Bonkowsky (Department of Pediatrics, University of Utah), Allison M. Bradbury (Jerry R. Mendell Center for Gene Therapy, The Abigail Wexner Research Institute at Nationwide Childrens Hospital)

Abstract:
Vanishing White Matter Disease (VWM) is a severe childhood-onset leukodystrophy caused by loss-of-function mutations in the eukaryotic initiation factor 2B (eIF2B) complex, most commonly in EIF2B5.1 The disease is characterized by motor impairment, neurologic decline, seizures, and premature death, with progression triggered by stress.2,3 There are no approved treatments. Because astrocytes play a central role in disease development, they represent an important therapeutic target.4,5 Therefore, we evaluated AAV9-mediated astrocyte targeted and ubiquitous EIF2B5 gene replacement in two VWM mouse modelsR191H and I98Mwhich resulted in delayed disease progression, improved body weight, and motor function.6 In I98M mice, all vectors prolonged lifespan, with high-dose astrocyte-targeted treatment extending survival up to 2 years. However, full correction was not achieved, as seizures and neurologic decline persisted. To define this incomplete rescue, we performed single-cell RNA sequencing on age- and dose-matched control and gene therapy-treated brains. Even after treatment, dysregulation of apoptotic, inflammatory, and stress response pathways remained in astrocytes, as indicated by pseudobulk differential expression and pathway analyses. To identify positively transduced cells, we incorporated human transgene reads into the reference genome, which showed 5-10% of cells expressed the human transgene. Across treatments, transgenic EIF2B5 positive astrocytes showed down regulation of biomarkers including Gdf15, indicating that wild type EIF2B5 expression can correct molecular pathology. However, dysregulation persists in non-transduced cells, defining a limitation of this cell autonomous gene therapy. These findings support both the promise and limitations of astrocyte-targeted EIF2B5 gene replacement and support optimization and combination strategies for VWM.

References:
1. Fogli, A. et al. The effect of genotype on the natural history of eIF2B-related leukodystrophies. Neurology 62, 15091517 (2004).
2. Van Der Knaap, M. S. et al. A new leukoencephalopathy with vanishing white matter. Neurology 48, 845855 (1997).
3. Hamilton, E. M. C. et al. Natural History of Vanishing White Matter. Ann. Neurol. 84, 274288 (2018).
4. Bugiani, M., Vuong, C., Breur, M. & van der Knaap, M. S. Vanishing white matter: a leukodystrophy due to astrocytic dysfunction. Brain Pathol. 28, 408421 (2018).
5. Dooves, S. et al. Astrocytes are central in the pathomechanisms of vanishing white matter. J. Clin. Invest. 126, 15121524 (2016).
6. Herstine, JA. et al. Evaluation of safety and early efficacy of AAV gene therapy in mouse models of vanishing white matter disease. Mol Ther. 32(6):1701-1720 (2024).

Keywords: AAV Gene Therapy , Leukodystrophy, scRNA-seq