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Hepatology. 2015 Aug;62(2):417-28. doi: 10.1002/hep.27842. Epub 2015 May 23.

Modeling correction of severe urea cycle defects in the growing murine liver using a hybrid recombinant adeno-associated virus/piggyBac transposase gene delivery system.

Author information

1
Gene Therapy Research Unit, Children's Medical Research Institute and The Children's Hospital at Westmead, Westmead, New South Wales, Australia.
2
University of Sydney Medical School, Sydney, New South Wales, Australia.
3
Department of Chemistry and Biomolecular Sciences, Macquarie University, Macquarie Park, New South Wales, Australia.
4
Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada.
5
Biochemical Genetics, The Children's Hospital at Westmead, Westmead, Sydney, New South Wales, Australia.
6
Institute of Medical Science and Department of Obstetrics & Gynaecology, University of Toronto, Toronto, Ontario, Canada.
7
Department of Obstetrics & Gynaecology, University of Toronto, Toronto, Ontario, Canada.
8
Discipline of Paediatrics and Child Health, The University of Sydney, Sydney, New South Wales, Australia.

Abstract

Liver-targeted gene therapy based on recombinant adeno-associated viral vectors (rAAV) shows promising therapeutic efficacy in animal models and adult-focused clinical trials. This promise, however, is not directly translatable to the growing liver, where high rates of hepatocellular proliferation are accompanied by loss of episomal rAAV genomes and subsequently a loss in therapeutic efficacy. We have developed a hybrid rAAV/piggyBac transposon vector system combining the highly efficient liver-targeting properties of rAAV with stable piggyBac-mediated transposition of the transgene into the hepatocyte genome. Transposition efficiency was first tested using an enhanced green fluorescent protein expression cassette following delivery to newborn wild-type mice, with a 20-fold increase in stably gene-modified hepatocytes observed 4 weeks posttreatment compared to traditional rAAV gene delivery. We next modeled the therapeutic potential of the system in the context of severe urea cycle defects. A single treatment in the perinatal period was sufficient to confer robust and stable phenotype correction in the ornithine transcarbamylase-deficient Spf(ash) mouse and the neonatal lethal argininosuccinate synthetase knockout mouse. Finally, transposon integration patterns were analyzed, revealing 127,386 unique integration sites which conformed to previously published piggyBac data.

CONCLUSION:

Using a hybrid rAAV/piggyBac transposon vector system, we achieved stable therapeutic protection in two urea cycle defect mouse models; a clinically conceivable early application of this technology in the management of severe urea cycle defects could be as a bridging therapy while awaiting liver transplantation; further improvement of the system will result from the development of highly human liver-tropic capsids, the use of alternative strategies to achieve transient transposase expression, and engineered refinements in the safety profile of piggyBac transposase-mediated integration.

PMID:
26011400
DOI:
10.1002/hep.27842
[Indexed for MEDLINE]

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