Adenovirus-mediated in vivo gene transfer rapidly protects ornithine transcarbamylase-deficient mice from an ammonium challenge

The purpose of this study was to determine the time of onset, duration, and the efficacy of in vivo gene transfer in protecting the ornithine transcarbamylase deficient spf/Y mouse from an acute ammonium challenge. The animals were challenged with ammonia (10 mmol/kg NH4Cl) 1, 2, 7, 14, or 28 d after the administration of a recombinant adenoviral construct deleted in El and with a temperature sensitive mutation in E2. Although there was no protection with the control LacZ virus, the ornithine transcarbamylase (OTC)-containing vector provided partial protection from both behavioral symptoms (ataxia, seizures, and abnormal response to sound) and biochemical abnormalities (ammonium, aspartate, alanine, and glutamine) within 24 h and complete protection by 48 h. Mortality was also decreased. Animals receiving the vector 7 and 14 d before the ammonium load were also protected, whereas those treated 28 d before the challenge were not. OTC enzyme activity in liver of untreated spf/Y mice was 5% of control C3H mice. After gene transfer, activity was increased to near control levels through 14 d but had returned to baseline by 28 d. These studies indicate that adenovirus-mediated gene transfer confers a metabolic benefit within 24 h of administration and provides protection against an acute metabolic insult for at least 2 wk.