Abstract Details

B3 - Lysosomal Storage Diseases

52: From Mouse to Sheep: Developing an AAV Gene Therapy for Sialidosis

Type: Oral Abstract Session

Presentation Details

Session Title: Lysosomal Storage Disorders






Sialidosis is a rare lysosomal storage disease caused by mutations in the NEU1 gene that encodes the lysosomal sialidase neuraminidase 1 (NEU1). Deficiency of NEU1 causes accumulation of sialylated glycopeptides and oligosaccharides in tissues and body fluids, resulting in cell and organ dysfunction. Sialidosis has two forms the late onset type I or early onset type II. Type I patients have adolescent onset with myoclonus, ataxia, seizures, cherry-red spot, and vision loss with death in midlife. Type II infantile/juvenile patients are more severe, including hepatosplenomegaly, coarse facial features, dysostosis multiplex, developmental delay, and death in childhood. There are no approved therapies for sialidosis. We developed an AAV-mediated gene therapy strategy to treat sialidosis that includes three AAV9 vectors: encoding either Neu1 alone (AAV9-Neu1), or in combination with its chaperone protein cathepsin A (AAV9-Ctsa-Bici-Neu1) or encoding modifications to enhance secretion (AAV9-Idua-Neu1). Neonatal Neu1-KO mice were injected via intracerebroventricular with 1E11vg of each AAV vector. Increased survival was noted for all three vectors compared to untreated Neu1-KO mice, however both AAV9-Neu1 treated WT (n=1) and NEU1-KO mice developed seizures at ~10 months of age (A). Behavioral testing revealed significant motor improvement for AAV treated Neu1-KO mice for all three vectors compared to Neu1-KO untreated mice with a trend toward decreased anxiety-like behavior (B&C). Reduction of sialic acid and PPCA levels were observed in the liver, brain, and quad, while mild reduction was seen in the kidney of treated mice compared to untreated Neu1-KO mice (D). Increased Neu1 activity was observed in the kidney, quadriceps, and brain of treated mice versus untreated Neu1-KO mice (D). Pathology of the liver, spleen, kidney, and pancreas was markedly ameliorated as well as diminished astrocytosis in the hippocampus of treated mice compared to untreated Neu1-KO’s. Overall, the most efficacious vector is AAV9-Ctsa-Bici-Neu1, which will be further tested in a large animal model of sialidosis. We have successfully generated the first sheep model of sialidosis type II. Using CRISPR-SpCas9 technology, we generated a founder sheep heterozygous for a 3 base pair deletion within exon 5 of Neu1(A320del) that is in the same loation as the amino acid change in patients (A319V). the A320del in sheep recapitulates many aspects of sialidosis including increased sialic acid levels (E), reduced Neu1 activity (F), neurological deficits, hepatosplenomegaly, hydronephrosis in the kidney, bone deformities, contracted tendons, and short lifespan. Further characterization of this model is currently ongoing. Altogether these studies in parallel with natural history studies in sialidosis patients will inform future clinical trials for this devastating disease.

Jillian Gallagher¹, Judith Gallant², Ping Xu², Rachael Gately³, Stephanie Bertrand³, Rachel Prestigiacomo³, Abigail McElroy¹, Erin F. Hall⁴, Hector Ribeiro Benatti⁵, Leigh Fremuth⁶, Diantha Van de Vlekkert⁶, Camilo Toro⁷, Cynthia J. Tifft⁷, Scot A. Wolfe⁵, Alessandra d'Azzo⁶, Miguel Sena-Esteves⁸, Yvette Lopez-Diaz¹, Heather L. Gray-Edwards<sup>5

1</sup>Horae Gene Therapy Center, UMass Chan Medical School, Worcester, MA,²Department of Pediatrics, UMass Chan Medical School, Worcester, MA,³Cummings School of Veterinary Medicine at Tufts University, Grafton, MA,⁴University of Massachusetts Chan Medical School, Worcester, MA,⁵UMass Chan Medical School, Worcester, MA,⁶St. Jude Children’s Research Hospital, Memphis, TN,⁷National Institutes of Health, Bethesda, MD,⁸Neurology, UMass Chan Medical School, Worcester, MA"