Split AAV-Mediated Gene Therapy Restores Ureagenesis in a Murine Model of Carbamoyl Phosphate Synthetase 1 Deficiency.

Abstract

The urea cycle enzyme carbamoyl phosphate synthetase 1 (CPS1) catalyzes the initial step of the urea cycle; bi-allelic mutations typically present with hyperammonemia, vomiting, ataxia, lethargy progressing into coma, and death due to brain edema if ineffectively treated. The enzyme deficiency is particularly difficult to treat; early recognition is essential to minimize injury to the brain. Even under optimal conditions, therapeutic interventions are of limited scope and efficacy, with most patients developing long-term neurologic sequelae. One significant encumberment to gene therapeutic development is the size of the CPS1 cDNA, which, at 4.5 kb, nears the packaging capacity of adeno-associated virus (AAV). Herein we developed a split AAV (sAAV)-based approach, packaging the large transgene and its regulatory cassette into two separate vectors, thereby delivering therapeutic CPS1 by a dual vector system with testing in a murine model of the disorder. Cps1-deficient mice treated with sAAVs survive long-term with markedly improved ammonia levels, diminished dysregulation of circulating amino acids, and increased hepatic CPS1 expression and activity. In response to acute ammonia challenging, sAAV-treated female mice rapidly incorporated nitrogen into urea. This study demonstrates the first proof-of-principle that sAAV-mediated therapy is a viable, potentially clinically translatable approach to CPS1 deficiency, a devastating urea cycle disorder.

• Authors: Matthew Nitzahn, Gabriella Allegri, Suhail Khoja, Brian Truong, Georgios Makris, Johannes Häberle, Gerald S Lipshutz
• Journal: Molecular therapy : the journal of the American Society of Gene Therapy (Mol Ther) Vol. 28 Issue 7 Pg. 1717-1730 (07 08 2020) ISSN: 1525-0024 [Electronic] United States
• PMID: 32359471 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2020 The American Society of Gene and Cell Therapy. Published by Elsevier Inc. All rights reserved.

Chemical References

• Ammonia
• Urea
• CPS1 protein, human
• Carbamoyl-Phosphate Synthase (Ammonia)

Topics

• Ammonia (metabolism)
• Animals
• Carbamoyl-Phosphate Synthase (Ammonia) (genetics)
• Carbamoyl-Phosphate Synthase I Deficiency Disease (genetics, metabolism, therapy)
• DNA Packaging
• Dependovirus (genetics)
• Disease Models, Animal
• Female
• Genetic Therapy
• Genetic Vectors (administration & dosage)
• Humans
• Mice
• Proof of Concept Study
• Urea (metabolism)