Correction of Ornithine Transcarbamylase Deficiency in AdultspfashMice and in OTC-Deficient Human Hepatocytes with Recombinant Adenoviruses Bearing the CAG Promoter

Publisher Website
Google Scholar
Abstract
Ornithine transcarbamylase (OTC) deficiency, the most common and severe inborn error of the urea cycle in humans, remains without adequate treatment, and mortality rates are high. Adenoviral vectors provide an efficient system for gene delivery, but there are problems, including toxicity. Efficient promoters that reduce the amount of vector required for treatment need to be developed. We constructed two recombinant adenoviral vectors, AdexCAGhOTC and AdexSRαhOTC, which harbor the human OTC gene under transcriptional control of CAG (a modified chicken β-actin promoter with CMV-IE enhancer) and SRα (the SV40 early promoter with the R segment and part of the U5 segment of the HTLV-1 LTR), respectively. Each was tested in adult spfash mice, an animal model of human OTC deficiency, and in primary human hepatocytes with OTC deficiency. Spfash mice have a pronounced orotic aciduria as seen in humans. A complete recovery of hepatic OTC activity with minimal tissue damage was observed in these animals following the intravenous administration of AdexCAGhOTC alone. Western blot analysis confirmed hepatic OTC expression and normalization of orotic aciduria was evident for 60 days. Enzyme activities of primary human hepatocytes infected with AdexCAGhOTC were 10–40 times higher than those with AdexSRαhOTC. Thus, the adenoviral vector with an efficient promoter such as CAG, can be given further consideration for possible gene therapy in humans with OTC deficiency. Kiwaki et al. report the adenoviral-mediated transfer of the ornithine transcarbamylase (OTC) gene. Using the CAG promoter, enzyme activity equal to that of the wild type was obtained in adult spfash mice and in deficient human hepatocytes. The strong and rapid expression seen here would be advantageous for treating subjects with this disease. The immune response would need to be given further study.