Self-complementary adeno-associated virus serotype 2 vector: global distribution and broad dispersion of AAV-mediated transgene expression in mouse brain

Abstract

The blood-brain barrier is the main obstacle to efficient delivery of therapeutic reagents, including viral vectors, into the central nervous system (CNS) for treating global CNS diseases. In this study, the effects of mannitol infusions on global brain gene expression of a novel AAV vector were examined after intravenous (i.v.) or intracisternal injection. Initially, a self-complementary adeno-associated virus serotype 2 vector (scAAV) was compared to traditional single-stranded AAV2 vector for reporter gene expression in the brain of adult mice with or without pretreatment of an i.v. mannitol infusion. One to two months postinjection, analysis of vector-transduced green fluorescent protein (GFP) expression in the brain revealed that vector delivery to the CNS via i.v. injection required pretreatment with mannitol. This expression was observed only when scAAV vectors were used. Using these conditions, transgene expression was observed in various neurons and glial cells throughout the brain. The peripherally administered scAAV vectors also transduced the cells in multiple somatic tissues with efficient expression in liver (20-30% of hepatocytes), but was less efficient in other somatic tissues. Intracisternal injection of scAAV vector produced a broad and intense transgene expression in both neurons and glial cells in the CNS of injected mice ranging from the olfactory area to the brain stem and spinal cord. More than 50% of the Purkinje cells in the cerebellum expressed GFP. Intravenous infusion of mannitol before intracisternal injection of the scAAV vector enhanced the dispersion of the vector in the CNS. Further optimization of these steps combining peripheral and intracisternal scAAV gene delivery should facilitate the development of treatments for global CNS diseases, especially diseases involving both the somatic system and the CNS, such as lysosomal storage disorders.

Significantly increased lifespan and improved behavioral performances by rAAV gene delivery in adult mucopolysaccharidosis IIIB mice

“…In addition, mannitol pretreatment also enhanced the delivery of rAAV injected into the posterior cistern of adult mice, beyond the BBB, resulting in a deep periventricular, though not global, distribution of transduced cells in the CNS, likely through the effects of the re-establishment of fluid balance within the brain tissues. 13 These observations provide a foundation for the therapeutic use of mannitol-enhanced rAAV gene delivery for the correction of the CNS manifestations of MPS IIIB.…”

“…These data are consistent with the propensity of the liver to take up the vast majority of i.v.-injected AAV2 vector, with or without mannitol pretreatment. 13 The CNS and somatic correction of lysosomal storage by rAAV gene delivery Several different methods, including direct quantitation of GAG, histopathology, and transmission electron microscopy (TEM) were used to evaluate the rAAVNaGlu-mediated correction of lysosomal storage in somatic and CNS tissues in MPS IIIB mice. The i.v.…”

“…infusion of mannitol to transiently open the BBB. 13 The mannitol pretreatment both enabled the CNS entry of i.v.-injected rAAV vector, and enhanced the spread of i.c.-delivered rAAV vector in CNS tissues. 13 Using the strategy of combining an i.v.…”

“…infusion of mannitol facilitated the CNS entry of i.v.-delivered rAAV2 reporter vector, and a diffuse global distribution of transduced neuronal and non-neuronal cells throughout the CNS. 13 No CNS delivery was observed without mannitol pretreatment. In addition, mannitol pretreatment also enhanced the delivery of rAAV injected into the posterior cistern of adult mice, beyond the BBB, resulting in a deep periventricular, though not global, distribution of transduced cells in the CNS, likely through the effects of the re-establishment of fluid balance within the brain tissues.…”

“…12 The wellestablished rAAV vector system has been shown to mediate long-term gene expression and functional correction in both the CNS and in multiple somatic tissues of different animal models. 13,14 Previous studies have also demonstrated rAAV-mediated long-term transgene expression in both neuronal and non-neuronal cells, resulting in the correction of lysosomal storage in MPS I, MPS IIIB and MPS VII animals after direct injection into the mouse brain. [15][16][17][18][19] The most challenging aspect of MPS IIIB therapeutic studies is to develop treatment for the degeneration of CNS function, for which the major obstacle is the BBB, which segregates the CNS from the blood circulation system and impedes effective delivery of therapeutic reagents.…”