Efficacy of a Bicistronic Vector for Correction of Sandhoff Disease in a Mouse Model

Evan Woodley; Karlaina J L Osmon; Patrick Thompson; Christopher Richmond; Zhilin Chen; Steven J Gray; Jagdeep S Walia

doi:10.1016/j.omtm.2018.10.011

Efficacy of a Bicistronic Vector for Correction of Sandhoff Disease in a Mouse Model

Mol Ther Methods Clin Dev. 2018 Oct 26:12:47-57. doi: 10.1016/j.omtm.2018.10.011. eCollection 2019 Mar 15.

Authors

Evan Woodley¹, Karlaina J L Osmon², Patrick Thompson¹, Christopher Richmond¹, Zhilin Chen³, Steven J Gray^{4

5}, Jagdeep S Walia^{1

2

3}

Affiliations

¹ Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada.
² Centre for Neuroscience Studies, Queen's University, Kingston, ON, Canada.
³ Medical Genetics/Departments of Pediatrics, Queen's University, Kingston, ON, Canada.
⁴ Gene Therapy Center, University of North Carolina, Chapel Hill, NC, USA.
⁵ Department of Pediatrics; UT Southwestern Medical Center, Dallas, TX, USA.

Abstract

G_M2 gangliosidoses are a family of severe neurodegenerative disorders resulting from a deficiency in the β-hexosaminidase A enzyme. These disorders include Tay-Sachs disease and Sandhoff disease, caused by mutations in the HEXA gene and HEXB gene, respectively. The HEXA and HEXB genes are required to produce the α and β subunits of the β-hexosaminidase A enzyme, respectively. Using a Sandhoff disease mouse model, we tested for the first time the potential of a comparatively lower dose (2.04 × 10¹³ vg/kg) of systemically delivered single-stranded adeno-associated virus 9 expressing both human HEXB and human HEXA cDNA under the control of a single promoter with a P2A-linked bicistronic vector design to correct the neurological phenotype. A bicistronic design allows maximal overexpression and secretion of the Hex A enzyme. Neonatal mice were injected with either this ssAAV9-HexB-P2A-HexA vector or a vehicle solution via the superficial temporal vein. An increase in survival of 56% compared with vehicle-injected controls and biochemical analysis of the brain tissue and serum revealed an increase in enzyme activity and a decrease in brain G_M2 ganglioside buildup. This is a proof-of-concept study showing the "correction efficacy" of a bicistronic AAV9 vector delivered intravenously for G_M2 gangliosidoses. Further studies with higher doses are warranted.

Keywords: AAV9; Sandhoff disease; Tay-Sachs disease; gene therapy; hexosaminidase.