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ABSTRACT: Gene therapy using recombinant adeno-associated virus vectors (rAAV) is generally considered safe. During the course of a study designed to determine the long-term efficacy of rAAV-mediated gene therapy initiated in newborn mice with the lysosomal storage disease, mucopolysaccharidosis type VII (MPSVII), a significant incidence of hepatocellular carcinomas and angiosarcomas was discovered. A hepatocellular carcinoma was first detected in a 35-week-old mouse and by 72 weeks of age, three out of five rAAV-treated MPSVII mice had similar lesions. These types of tumors had not been seen previously in long-term studies of MPSVII mice using recombinant enzyme or bone marrow transplantation. In an attempt to ascertain whether mouse strain or GUSB expression confers susceptibility to tumor formation, we histopathologically examined untreated normal mice of the same strain, untreated MPSVII mice, and normal mice overexpressing human GUSB for the presence of tumors and increased hepatocyte replication. The results of these studies do not indicate that MPSVII mice or mice overexpressing human GUSB are susceptible to tumor formation; however, the number of animals examined is too small to draw definitive conclusions. Results from quantitative PCR performed on the tumor samples suggest that the tumors are probably not caused by an insertional mutagenesis event followed by the clonal expansion of a transformed cell. In a separate study, a relatively large group of mice injected with varying doses and types of rAAV vectors had no evidence of hepatic or vascular tumors. Although the mechanism of tumor formation is currently unknown, the tumorigenic potential of rAAV vectors must be rigorously determined in long-term in vivo studies.
Gene Therapy 10/2001; 8(17):1343-6. · 3.71 Impact Factor
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ABSTRACT: For many metabolic diseases, early correction of the inherited deficiency is required to prevent long-term sequelae. We examined the ability of adeno-associated virus (AAV) to mediate efficient gene transfer during the neonatal period in mice with the lysosomal storage disease mucopolysaccharidosis type VII (MPS VII). Quadriceps of newborn MPS VII mice were injected with an AAV vector containing human beta-glucuronidase (GUSB) cDNA. High-level intramuscular GUSB expression was seen as early as 2 weeks of age, and persisted for at least 16 weeks with no reduction in activity. In addition, GUSB activity was detected in both liver and spleen at later time points. The level of GUSB activity resulted in a significant reduction in lysosomal storage in the liver and a minimal reduction in the spleen at 16 weeks. However, the temporal and spatial pattern of hepatic GUSB activity, coupled with the presence of GUSB cDNA in liver sections, suggests that hematogenous dissemination of virus at the time of injection led to gene transfer to hepatic cells. These results demonstrate that AAV vectors can successfully infect neonatal muscle and persist through the rapid growth phase following birth. However, GUSB secretion from an intramuscular source is inefficient, limiting the therapeutic efficacy of this approach.
Human Gene Therapy 02/1999; 10(1):85-94. · 4.22 Impact Factor
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M S Sands,
J H Wolfe,
E H Birkenmeier,
J E Barker,
C Vogler,
W S Sly,
T Okuyama,
B Freeman,
A Nicholes, N Muzyczka,
P L Chang,
H R Axelrod
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ABSTRACT: Mucopolysaccharidosis type VII (MPS VII) is caused by a deficiency in the lysosomal enzyme beta-glucuronidase resulting in the accumulation of undegraded glycosaminoglycans in many tissues. A murine model of MPS VII shares many of the clinical, biochemical and histopathological features of human MPS VII and has provided an opportunity to study novel therapeutic approaches in a system with a uniform genetic background. Retroviral mediated gene therapy directed to the hematopoietic system or to artificial neo-organs resulted in low levels of enzyme in several tissues and reduced lysosomal storage in the liver and spleen. Partial correction of the disease in the eye was observed following an intravitreal injection of recombinant adenovirus. Neither retroviral nor adenoviral mediated gene transfer techniques resulted in a systemic reduction of lysosomal storage. Here we discuss several novel gene transfer approaches designed to increase the systemic levels of beta-glucuronidase in the MPS VII mouse.
Neuromuscular Disorders 08/1997; 7(5):352-60. · 2.80 Impact Factor
