Gene Therapy for Very Long Chain Acyl-coA Dehydrogenase Deficiency Using Adeno-Associated Virus Vectors: A Dissertation

Abstract

Very long chain acyl-coA dehydrogenase (VLCAD) is the rate-limiting step in mitochondrial fatty acid oxidation. VLCAD deficient mice and patients’ clinical symptoms stem from not only an energy deficiency but also long-chain metabolite accumulations. VLCAD deficient mice were treated systemically with 1x10 vector genomes of rAAV9-VLCAD. Expression was detected in the liver, heart and muscle. Also substantial expression of VLCAD was noted in the brain, where it was expressed across different sections of the brain and in different cell types with different morphologies. Biochemical correction was observed in vector-treated mice beginning two weeks post-injection, as characterized by a significant drop in long chain fatty acyl accumulates in whole blood after an overnight fast. Changes persisted through the termination point around 20 weeks post injection. Magnetic resonance spectroscopy (MRS) and tandem mass spectrometry (MS/MS) revealed normalization of intramuscular lipids in treated animals. Correction was not observed in liver tissue extracts, but cardiac muscle extracts showed significant reduction of long chain metabolites. Disease-specific phenotypes were characterized, including thermoregulation and maintenance of euglycemia after a fasting cold challenge. Internal body temperatures of untreated VLCAD-/mice dropped below 20°C and the mice became lethargic, requiring euthanasia. In contrast all rAAV9-treated VLCAD-/mice and the wildtype controls maintained body temperatures. rAAV9-treated VLCAD-/mice maintained euglycemia, whereas untreated VLCAD-/mice suffered hypoglycemia following a fasting cold challenge. These promising results suggest rAAV9 gene therapy as a potential treatment for VLCAD deficiency in humans.