Long-term correction of murine glycogen storage disease type Ia by recombinant adeno-associated virus-1-mediated gene transfer

Abstract

Glycogen storage disease type Ia (GSD-Ia) is caused by a deficiency in glucose-6-phosphatase-a (G6Pase-a), a ninetransmembrane domain, endoplasmic reticulum-associated protein expressed primarily in the liver and kidney. Previously, we showed that infusion of an adeno-associated virus (AAV) serotype 2 vector carrying murine G6Pase-a (AAV2-G6Pase-a) into neonatal GSD-Ia mice failed to sustain their life beyond weaning. We now show that neonatal infusion of GSD-Ia mice with an AAV serotype 1-G6Pase-a (AAV1-G6Pase-a) or AAV serotype 8-G6Pase-a (AAV8-G6Pase-a) results in hepatic expression of the G6Pase-a transgene and markedly improves the survival of the mice. However, only AAV1-G6Pase-a can achieve significant renal transgene expression. A more effective strategy, in which a neonatal AAV1-G6Pase-a infusion is followed by a second infusion at age 1 week, provides sustained expression of a complete, functional, G6Pase-a system in both the liver and kidney and corrects the metabolic abnormalities in GSD-Ia mice for the 57 week length of the study. This effective use of gene therapy to correct metabolic imbalances and disease progression in GSD-Ia mice holds promise for the future of gene therapy in humans. Gene Therapy (2005) 13, 321-329.

Early, sustained efficacy of adeno-associated virus vector-mediated gene therapy in glycogen storage disease type Ia

“…in the liver as detected by RT-PCR (Figure 3e, lanes 4-9); however, G6Pase expression declined to almost undetectable levels at 7 and 10 m.o. in the kidney ( Figure 3e, lanes [11][12][13][14][15][16]. No signal for vector DNA and RNA was present for phosphate-buffered saline (PBS)-treated mice (Figure 3c-e, PBS) and no signal for b-actin was present for negative control polymerase chain reactions reactions (PCR) (Figure 3c-e, lane 2), indicating that samples and reagents were not contaminated with exogenous nucleic acids.…”

“…(to 60717 mg/dl). 12,13 Thus, high numbers of AAV2/8 vector particles were required to partially correct hypoglycemia during fasting in infant GSD-Ia mice, despite substitution of a well-characterized, high-activity promoter/enhancer for the G6Pase promoter.…”

Potential of AAV vectors in the treatment of metabolic disease

“…Excluding GSD II, which is discussed as an LSD, GDS Ia is the only disease in the class to have received attention as a possible target for AAV-mediated gene therapy. [83][84][85] While dietary therapy has improved growth and survival, improved therapies are required to address problematic long-term complications, including liver tumors, osteoporosis and renal failure. The possibility of ERT, as described for GSD II, is precluded by the fact that the deficient enzyme, glucose-6-phosphatase-a, is a hydrophobic endoplasmic reticulum-associated transmembrane protein that cannot be expressed in a soluble active form.…”

“…86 Murine and canine models of GSD Ia exist, and both have been used to explore AAV-mediated phenotype correction. [83][84][85] In mice, substantial biochemical correction, including abnormal glycogen storage, has been achieved with vectors bearing serotype 1 or 8 capsids., 84,85 In dogs, consistent reduction in liver glycogen has been achieved with normalization of fasting glucose, cholesterol, triglycerides and lactic acid reported in one animal. Whether longer term complications mentioned earlier can be ameliorated remains unknown, and truly effective therapy is likely to require highly efficient gene delivery to both liver and kidney.…”

Adeno-associated virus gene therapy prevents hepatocellular adenoma in murine model of glycogen storage disease type Ia

“…Using AAV8 or AAV1 vectors prolonged survival, and partial biochemical correction was demonstrated in G6pc À/À mice. 10,11 However, both studies required high vector doses in excess of 2 Â 10 14 vector genome/kg while still failing to fully correct biochemical parameters and restore G6Pase deficiency. Further improvements in efficacy were achieved by using a scAAV8 vector expressing human G6Pase-a from a minimal human G6Pase promoter.…”