Brain GALT restoration by intrathecal injection of scAAV9-hGALT enables partial metabolic correction in adolescent GALT-null rats Open Access
Patel, Sneh (Spring 2023)
Abstract
Classic Galactosemia (CG) is a potentially lethal autosomal recessive disorder caused by a severe deficiency of galactose-1-phosphate uridylyl transferase (GALT). Following galactose exposure, newborns with CG develop feeding difficulties, cataracts, failure to thrive, hepatocellular damage, hypotonia, renal tubular disease, and E. coli sepsis, which can lead to neonatal death. The current therapeutic standard of care for galactosemic patients is a galactose-restricted diet which is effective in nullifying acute neonatal complications but is inadequate in preventing long-term complications such as cognitive deficits, problems with speech, fine motor skills deficits, persistent cataracts, and primary ovarian insufficiency in young women. GALT gene therapy is currently being investigated as a potential treatment to directly restore GALT activity. The overarching goal of the study is to test the efficacy of scAAV9-mediated hGALT replacement administered intrathecally in adolescent GALT-null rats. GALT enzymes assays confirmed successful hGALT transduction in the brains of GALT-null rats that persisted for at least four months with fairly high tissue specificity. Previous studies have suggested accumulation of galactose metabolites from the Leloir pathway may be the root cause of some of the adverse phenotypes associated with CG. Galactitol responded well at 30 days after treatment in both brain and plasma. However, other metabolic abnormalities were not significantly reduced at the three timepoints in the study. The lack of significant metabolic efficacy could be attributed to insufficient GALT restoration in the brain and/or the inability of the brain to metabolize galactose sufficiently to “scrub the blood”. Although our current findings are inconclusive, future research, for example with higher doses or altered virus with improved access to the brain could potentially provide greater metabolic impact. The results reported here represent a major conceptual step in the direction of developing an effective gene therapy treatment option for adolescent patients with CG.
Table of Contents
Chapter 1: Background and Introduction 1
Description of Classic Galactosemia and Patient Experience 1
The Leloir Pathway of Galactose Metabolism 3
Current Treatment and Gene-Based Therapeutic Approaches 4
Adeno-Associated Virus (AAV)-Mediated Therapy 6
The CG Rat Model 8
Neonatal AAV-mediated GALT Restoration Offers Metabolic and Phenotypic Partial Rescue 10
Significance of the study 10
Chapter 2: GALT restoration in brain following adolescent intrathecal administration of scAAV9-hGALT 13
Introduction 13
Materials and Methods 13
Results 21
Discussion 28
Chapter 3: Metabolic efficacy in brain and plasma following adolescent intrathecal administration of scAAV9-hGALT 30
Introduction 30
Materials and Methods 30
Results 37
Discussion 59
Chapter 4: Discussion, Limitations, and Future Directions 61
References 65
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Brain GALT restoration by intrathecal injection of scAAV9-hGALT enables partial metabolic correction in adolescent GALT-null rats () | 2023-04-08 15:10:31 -0400 |
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