AAV-Mediated Gene Delivery in Adult GM1-Gangliosidosis Mice Corrects Lysosomal Storage in CNS and Improves Survival

Abstract

BackgroundGM1-gangliosidosis is a glycosphingolipid (GSL) lysosomal storage disease caused by a genetic deficiency of acid β-galactosidase (βgal), which results in the accumulation of GM1-ganglioside and its asialo-form (GA1) primarily in the CNS. Age of onset ranges from infancy to adulthood, and excessive ganglioside accumulation produces progressive neurodegeneration and psychomotor retardation in humans. Currently, there are no effective therapies for the treatment of GM1-gangliosidosis.Methodology/Principal FindingsIn this study we examined the effect of thalamic infusion of AAV2/1-βgal vector in adult GM1 mice on enzyme distribution, activity, and GSL content in the CNS, motor behavior, and survival. Six to eight week-old GM1 mice received bilateral injections of AAV vector in the thalamus, or thalamus and deep cerebellar nuclei (DCN) with pre-determined endpoints at 1 and 4 months post-injection, and the humane endpoint, or 52 weeks of age. Enzyme activity was elevated throughout the CNS of AAV-treated GM1 mice and GSL storage nearly normalized in most structures analyzed, except in the spinal cord which showed ∼50% reduction compared to age-matched untreated GM1 mice spinal cord. Survival was significantly longer in AAV-treated GM1 mice (52 wks) than in untreated mice. However the motor performance of AAV-treated GM1 mice declined over time at a rate similar to that observed in untreated GM1 mice.Conclusions/SignificanceOur studies show that the AAV-modified thalamus can be used as a ‘built-in’ central node network for widespread distribution of lysosomal enzymes in the mouse cerebrum. In addition, this study indicates that thalamic delivery of AAV vectors should be combined with additional targets to supply the cerebellum and spinal cord with therapeutic levels of enzyme necessary to achieve complete correction of the neurological phenotype in GM1 mice.

Bis(monoacylglycero)phosphate: a secondary storage lipid in the gangliosidoses

“…Vectors expressing the defi cient enzymes needed for corresponding ganglioside degradation are delivered intracranially. AAV treatments can successfully restore the defi cient enzymatic activity and eliminate most of the corresponding ganglioside storage ( 42,43,68 ). We observed that AAV treatment also eliminated secondary storage of BMP in SD mouse brains.…”

“…These fi ndings suggest that BMP storage is not likely associated with infl ammation, but is associated with ganglioside storage. AAV gene therapy has been successfully used to treat GM1 and GM2 gangliosidosis in both mice and cats ( 42,43,68 ). Vectors expressing the defi cient enzymes needed for corresponding ganglioside degradation are delivered intracranially.…”

“…Six-week-old SD mice were injected with 2 l of a 1:1 formulation of AAV1-CBA-Hex ␣ + AAV1-CBA-Hex ␤ vectors (7.2 × 10 12 gc/ml for each vector in the formulation) stereotaxically into left and right thalamus (n = 4) (coordinates from bregma in millimeters: anteroposterior, Ϫ 2.0; medial lateral, ±1.5; dorsal ventral, Ϫ 2.5) at a rate of 0.2. l·min Ϫ 1 as previously described ( 43 ).…”

Feasibility and Safety of Systemic rAAV9-hNAGLU Delivery for Treating Mucopolysaccharidosis IIIB: Toxicology, Biodistribution, and Immunological Assessments in Primates

“…The adeno-associated virus (AAV) vector system offers important advantages as a gene delivery tool for treating a great variety of diseases, including a broad tissue tropism and absence of known pathogenesis in humans (Berns and Linden, 1995). Recombinant AAV (rAAV) vectors based on AAV serotype 2 (AAV2) have been shown to transduce both neuronal and nonneuronal cells in the CNS in numerous gene therapy studies, with demonstrated therapeutic benefits in treating neurological diseases (Daya and Berns, 2008), including MPS and other LSDs, in animal models (Fu et al, 2002(Fu et al, , 2003(Fu et al, , 2007(Fu et al, , 2011Heuer et al, 2002;Desmaris et al, 2004;Liu et al, 2005;Fraldi et al, 2007;Sands and Haskins, 2008;McCarty et al, 2009;Baek et al, 2010;Heldermon et al, 2010;Ruzo et al, 2012). Multiple phase I clinical trials have been completed using rAAV gene delivery approaches in patients with neurological disorders (McPhee et al, 2006;Kaplitt et al, 2007;Worgall et al, 2008;Marks et al, 2010;Mittermeyer et al, 2012).…”

Gene Therapy for the Nervous System: Challenges and New Strategies

“…The comparison with AAV gene delivery to brain is difficult to establish as the resulting level of enzyme activity in different brain regions is measured in tissue blocks where the vast majority of cells are not transduced. Therefore the reported enzymatic activities of 10-to 100-fold above normal in different mouse [123,135] and cat [126,136] models of LSDs represent the activity of enzyme that is distributed throughout the brain from the target sites and now resides in non-transduced cells. Presently, there is no information on the degree of overexpression that takes place in AAV transduced cells in the target structures.…”