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Impaired clearance of accumulated lysosomal glycogen in advanced Pompe disease despite high-level vector-mediated transgene expression.

ABSTRACT: Infantile-onset glycogen storage disease type II (GSD-II; Pompe disease; MIM 232300) causes death early in childhood from cardiorespiratory failure in the absence of effective treatment, whereas late-onset Pompe disease causes a progressive skeletal myopathy. The limitations of enzyme replacement therapy could potentially be addressed with adeno-associated virus (AAV) vector-mediated gene therapy.AAV vectors containing tissue-specific regulatory cassettes, either liver-specific or muscle-specific, were administered to 12- and 17-month-old Pompe disease mice to evaluate the efficacy of gene therapy in advanced Pompe disease. Biochemical correction was evaluated through acid alpha-glucosidase (GAA) activity and glycogen content analyses of the heart and skeletal muscle. Western blotting, urinary biomarker, and Rotarod performance were evaluated after vector administration.The AAV vector containing the liver-specific regulatory cassette secreted high-level human GAA into the blood and corrected glycogen storage in the heart and diaphragm. The biochemical correction of the heart and diaphragm was associated with efficacy, as reflected by increased Rotarod performance; however, the clearance of glycogen from skeletal muscles was relatively impaired compared to in younger Pompe disease mice. An alternative vector containing a muscle-specific regulatory cassette transduced skeletal muscle with high efficiency, but also failed to achieve complete clearance of accumulated glycogen. Decreased transduction of the heart and liver in older mice, especially in females, was implicated as a cause for reduced efficacy in advanced Pompe disease.The impaired efficacy of AAV vector-mediated gene therapy in old Pompe disease mice emphasizes the need for early treatment to achieve full efficacy.

SUBMITTER: Sun B

PROVIDER: S-EPMC3622249 | biostudies-literature | 2009 Oct

REPOSITORIES: biostudies-literature

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Impaired clearance of accumulated lysosomal glycogen in advanced Pompe disease despite high-level vector-mediated transgene expression.

Sun Baodong B Zhang Haoyue H Bird Andrew A Li Songtao S Young Sarah P SP Koeberl Dwight D DD

The journal of gene medicine 20091001 10

<h4>Background</h4>Infantile-onset glycogen storage disease type II (GSD-II; Pompe disease; MIM 232300) causes death early in childhood from cardiorespiratory failure in the absence of effective treatment, whereas late-onset Pompe disease causes a progressive skeletal myopathy. The limitations of enzyme replacement therapy could potentially be addressed with adeno-associated virus (AAV) vector-mediated gene therapy.<h4>Methods</h4>AAV vectors containing tissue-specific regulatory cassettes, eith ...[more]

PMID: 19621331

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Project description:Pompe disease can be treated effectively, if immune tolerance to enzyme replacement therapy (ERT) with acid ?-glucosidase (GAA) is present. An adeno-associated viral (AAV) vector carrying a liver-specific regulatory cassette to drive GAA expression (AAV-LSPhGAA) established immune tolerance in GAA knockout (KO) mice, whereas ubiquitous expression with AAV-CBhGAA provoked immune responses. Therefore, we investigated the hypothesis that immune tolerance induced by hepatic-restricted expression was dominant. AAV-LSPhGAA and AAV-CBhGAA were administered singly or in combination to groups of adult GAA-KO mice, and AAV-LSPhGAA induced immune tolerance even in combination with AAV-CBhGAA. The dual vector approach to GAA expression improved biochemical correction of GAA deficiency and glycogen accumulations at 18 weeks, and improved motor function testing including wire-hang and grip-strength testing. The greatest efficacy was demonstrated by dual vector administration, when both vectors were pseudotyped as AAV8. T cells from mice injected with AAV-LSPhGAA failed to proliferate at all after an immune challenge with GAA and adjuvant, whereas mock-treated GAA-KO mice mounted vigorous T cell proliferation. Unlike AAV-LSPhGAA, AAV-CBhGAA induced selective cytokine and chemokine expression in liver and spleen after the immune challenge. AAV-CBhGAA transduced dendritic cells and expressed high-level GAA, whereas AAV-LSPhGAA failed to express GAA in dendritic cells. The level of transduction in liver was much higher after dual AAV8 vector administration at 18 weeks, in comparison with either vector alone. Dual vector administration failed to provoke antibody formation in response to GAA expression with AAV-CBhGAA; however, hepatic-restricted expression from dual vector expression did not prevent antibody formation after a strong immune challenge with GAA and adjuvant. The relevance of immune tolerance to gene therapy in Pompe disease indicates that hepatic expression might best be combined with nonhepatic expression, achieving the benefits of ubiquitous expression in addition to evading deleterious immune responses.

Project description:Pompe disease is an inherited lysosomal storage disorder that results from a deficiency in acid ?-glucosidase (GAA) activity due to mutations in the GAA gene. Pompe disease is characterized by accumulation of lysosomal glycogen primarily in heart and skeletal muscles, which leads to progressive muscle weakness. We have shown previously that the small molecule pharmacological chaperone AT2220 (1-deoxynojirimycin hydrochloride, duvoglustat hydrochloride) binds and stabilizes wild-type as well as multiple mutant forms of GAA, and can lead to higher cellular levels of GAA. In this study, we examined the effect of AT2220 on mutant GAA, in vitro and in vivo, with a primary focus on the endoplasmic reticulum (ER)-retained P545L mutant form of human GAA (P545L GAA). AT2220 increased the specific activity of P545L GAA toward both natural (glycogen) and artificial substrates in vitro. Incubation with AT2220 also increased the ER export, lysosomal delivery, proteolytic processing, and stability of P545L GAA. In a new transgenic mouse model of Pompe disease that expresses human P545L on a Gaa knockout background (Tg/KO) and is characterized by reduced GAA activity and elevated glycogen levels in disease-relevant tissues, daily oral administration of AT2220 for 4 weeks resulted in significant and dose-dependent increases in mature lysosomal GAA isoforms and GAA activity in heart and skeletal muscles. Importantly, oral administration of AT2220 also resulted in significant glycogen reduction in disease-relevant tissues. Compared to daily administration, less-frequent AT2220 administration, including repeated cycles of 4 or 5 days with AT2220 followed by 3 or 2 days without drug, respectively, resulted in even greater glycogen reductions. Collectively, these data indicate that AT2220 increases the specific activity, trafficking, and lysosomal stability of P545L GAA, leads to increased levels of mature GAA in lysosomes, and promotes glycogen reduction in situ. As such, AT2220 may warrant further evaluation as a treatment for Pompe disease.

Dataset Information

Impaired clearance of accumulated lysosomal glycogen in advanced Pompe disease despite high-level vector-mediated transgene expression.

Publications

Impaired clearance of accumulated lysosomal glycogen in advanced Pompe disease despite high-level vector-mediated transgene expression.

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