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Ornithine transcarbamylase deficiency (OTCD) is the most common inborn error of urea synthesis. Complete OTCD can result in hyperammonemic coma in the neonatal period, which can rapidly
become fatal. Current acute therapy involves dialysis; chronic therapy involves the stimulation of alternate nitrogen clearance pathways; and the only curative approach is liver
transplantation. Adeno-associated virus (AAV) vector-based gene therapy would add to current treatment options provided the vector delivers high level and stable transgene expression in
liver without dose-limiting toxicity. In this study, we employed an AAV2/8-based self-complementary (sc) vector expressing the murine OTC (mOTC) gene under a liver-specific thyroxine-binding
globulin promoter and examined the therapeutic effects in a mouse model of OTCD, the spf ash mouse. Seven days after a single intravenous injection of vector, treated mice showed complete
normalization of urinary orotic acid, a measure of OTC activity. We further improved vector efficacy by incorporating a Kozak or Kozak-like sequence into mOTC complementary DNA, which
increased the OTC activity by five or twofold and achieved sustained correction of orotic aciduria for up to 7 months. Our results demonstrate that vector optimizations can significantly
improve the efficacy of gene therapy.
We thank Martin Lock, Julie Johnston, Arbans Sandhu, and Shu-Jen Chen (Penn Vector) for supplying vectors, Guangping Gao and Xun Sun for initial participation of the project. This work was
supported in part by the Kettering Family Foundation and the following Grants to JMW: P01-HD057247, P01-HL059407 and P30-DK047757. HW was supported by a scholarship from China Scholarship
Council.
L Wang and H Wang: These authors contributed equally to this work.
Department of Pathology and Laboratory Medicine, Division of Transfusion Medicine, Gene Therapy Program, University of Pennsylvania, Philadelphia, PA, USA
L Wang, H Wang, P Bell, J Lin, D McMenamin, H Yu & J M Wilson
Center for Genetic Medicine Research, Children's National Medical Center, Children's Research Institute, Washington, DC, USA
Vaccine Research Institute, Third Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China
JMW is a consultant to ReGenX Holdings, and is a founder of, holds equity in and receives a grant from affiliates of ReGenX Holdings; in addition, he is an inventor on patents licensed to
various biopharmaceutical companies, including affiliates of ReGenX Holdings.
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