Adeno-associated Virus-mediated Rescue of Neonatal Lethality in Argininosuccinate Synthetase-deficient Mice

Abstract

Viral vectors based on adeno-associated virus (AAV) are showing exciting promise in gene therapy trials targeting the adult liver. A major challenge in extending this promise to the pediatric liver is the loss of episomal vector genomes that accompanies hepatocellular proliferation during liver growth. Hence maintenance of sufficient transgene expression will be critical for success in infants and children. We therefore set out to explore the therapeutic efficacy and durability of liver-targeted gene transfer in the challenging context of a neonatal lethal urea cycle defect, using the argininosuccinate synthetase deficient mouse. Lethal neonatal hyperammonemia was prevented by prenatal and early postnatal vector delivery; however, hyperammonemia subsequently recurred limiting survival to no more than 33 days despite vector readministration. Antivector antibodies acquired in milk from vector-exposed dams were subsequently shown to be blocking vector readministration, and were avoided by crossfostering vector-treated pups to vector-naive dams. In the absence of passively acquired antivector antibodies, vector redelivery proved efficacious with mice surviving to adulthood without recurrence of significant hyperammonemia. These data demonstrate the potential of AAV vectors in the developing liver, showing that vector readministration can be used to counter growth-associated loss of transgene expression provided the challenge of antivector humoral immunity is addressed.

Argininosuccinic aciduria fosters neuronal nitrosative stress reversed by Asl gene transfer

“…As with many liver inherited metabolic diseases, urea cycle defects exhibit a high rate of mortality and neurological morbidity in infancy despite conventional treatment 8 . Successful correction of the urea cycle via AAV-mediated gene therapy has been reported in mouse models of ornithine transcarbamylase deficiency 9,10 , argininosuccinate synthetase deficiency 11,12 , and arginase deficiency 13 . Argininosuccinic aciduria (ASA; OMIM 207900) is the second most common urea cycle defect with a prevalence of 1/218,000 live births 14 .…”

Adeno-associated virus serotype rh.10 displays strong muscle tropism following intraperitoneal delivery

“…In another pre-clinical trial, Kok et al . rescued the neonatal lethality of argininosuccinate synthetase-deficient mice14. In the clinic, a modified adenovirus vector with deletion of the E1B 55-kd gene was delivered via IP administration to treat patients with ovarian cancer22.…”

“…IP injection is less invasive than many types of local injection and potentially induces less of a humoral immune response in comparison to other routes of delivery, such as IV administration9101112. In addition, recent studies have shown that IP administration of certain rAAV serotypes produces comparable transduction efficiency relative to other routes of administration91314.…”

Gene Therapy for Inherited Diseases of Liver Metabolism

“…Several studies have repeatedly shown loss of episomal AAV vector genomes as a consequence of liver growth. 54,55 The decline in transgene expression, particularly during the early rapid growth phase of dividing tissues, is a substantial problem that compromises long-term phenotypic correction. The human liver doubles in weight between the newborn period and the first 3 months of a life, doubles again by 10 months, and then once more by the age of 5 years.…”