Complete correction of enzymatic deficiency and neurochemistry in the GM1-gangliosidosis mouse brain by neonatal adeno-associated virus-mediated gene delivery.

GM1-gangliosidosis is a glycosphingolipid (GSL) lysosomal storage disease caused by autosomal recessive deficiency of lysosomal acid beta-galactosidase (betagal), and characterized by accumulation of GM1-ganglioside and GA1 in the brain. Here we examined the effect of neonatal intracerebroventricular (i.c.v.) injection of an adeno-associated virus (AAV) vector encoding mouse betagal on enzyme activity and brain GSL content in GM1-gangliosidosis (betagal(-/-)) mice. Histological analysis of betagal distribution in 3-month-old AAV-treated betagal(-/-) mice showed that enzyme was present at high levels throughout the brain. Biochemical quantification showed that betagal activity in AAV-treated brains was 7- to 65-fold higher than in wild-type controls and that brain GSL levels were normalized. Cerebrosides and sulfatides, which were reduced in untreated betagal(-/-) mice, were restored to normal levels by AAV treatment. In untreated betagal(-/-) brains, cholesterol was present at normal levels but showed abnormal cellular distribution consistent with endosomal/lysosomal localization. This feature was also corrected in AAV-treated mice. The biochemical and histological parameters analyzed in this study showed that normal brain neurochemistry was achieved in AAV-treated betagal(-/-) mice. Therefore we show for the first time that neonatal AAV-mediated gene delivery of lysosomal betagal to the brain may be an effective approach for treatment of GM1-gangliosidosis.

Adeno-associated virus vectors serotyped with AAV8 capsid are more efficient than AAV-1 or -2 serotypes for widespread gene delivery to the neonatal mouse brain.

Adeno-associated virus (AAV) vectors have gained a preeminent position in the field of gene delivery to the normal brain through their ability to achieve extensive transduction of neurons and to mediate long-term gene expression with no apparent toxicity. In adult animals direct infusion of AAV vectors into the brain parenchyma results in highly efficient transduction of target structures. However AAV-mediated global delivery to the adult brain has been an elusive goal. In contrast, widespread global gene delivery has been obtained by i.c.v. injection of AAV1 or AAV2 in neonates. Among the novel AAV serotypes cloned and engineered for production of recombinant vectors, AAV8 has shown a tremendous potential for in vivo gene delivery with nearly complete transduction of many tissues in rodents after intravascular infusion. Here we compare the efficiency of an AAV8 serotyped vector with that of AAV1 and AAV2 serotyped vectors for the extent of gene delivery to the brain after neonatal injection into the lateral ventricles. The vectors all encoded green fluorescent protein (GFP) under control of a hybrid CMV enhancer/chicken beta-actin promoter with AAV2 inverted terminal repeats, but differed from each other with respect to the capsid type. A total of 6.8 x 10(10) genome copies were injected into the lateral ventricles of postnatal day 0 mice. Mice were killed at postnatal day 30 and brains analyzed for distribution of GFP-positive cells. AAV8 proved to be more efficient than AAV1 or AAV2 vectors for gene delivery to all of the structures analyzed, including the cerebral cortex, hippocampus, olfactory bulb, and cerebellum. Moreover the intensity of gene expression, assessed using a microarray reader, was considerably higher for AAV8 in all structures analyzed. In conclusion, the enhanced transduction achieved by AAV8 compared with AAV1 and AAV2 indicates that AAV8 is the superior serotype for gene delivery to the CNS.