Correction of neurological disease of mucopolysaccharidosis IIIB in adult mice by rAAV9 trans-blood-brain barrier gene delivery

Abstract

The greatest challenge in developing therapies for mucopolysaccharidosis (MPS) IIIB is to achieve efficient central nervous system (CNS) delivery across the blood-brain barrier (BBB). In this study, we used the novel ability of adeno-associated virus serotype 9 (AAV9) to cross the BBB from the vasculature to achieve long-term global CNS, and widespread somatic restoration of α-N-acetylglucosaminidase (NAGLU) activity. A single intravenous (IV) injection of rAAV9-CMV-hNAGLU, without extraneous treatment to disrupt the BBB, restored NAGLU activity to normal or above normal levels in adult MPS IIIB mice, leading to the correction of lysosomal storage pathology in the CNS and periphery, and correction of astrocytosis and neurodegeneration. The IV delivered rAAV9 vector also transduced abundant neurons in the myenteric and submucosal plexus, suggesting peripheral nervous system (PNS) targeting. While CNS entry did not depend on osmotic disruption of the BBB, it was significantly enhanced by pretreatment with an IV infusion of mannitol. Most important, we demonstrate that a single systemic rAAV9-NAGLU gene delivery provides long-term (>18 months) neurological benefits in MPS IIIB mice, resulting in significant improvement in behavioral performance, and extension of survival. These data suggest promising clinical potential using the trans-BBB neurotropic rAAV9 vector for treating MPS IIIB and other neurogenetic diseases.

Figures

Figure 1

Improved behavior and extended survival in mucopolysaccharidosis (MPS) IIIB mice by systemic recombinant adeno-associated virus 9 (rAAV9) gene transfer. Mice were tested for behavior at 5–5.5 months of age, and were observed for longevity. (a) Latency to fall from a rotarod (n = 11/group). (b) Survival (n ≥ 5/group, P < 0.001). +/+, wt; −/−, MPS IIIB; AAV9-L, AAV9-H, MPS IIIB mice treated with 5 × 1012 or 1.5 × 1013 vg/kg rAAV9-hNAGLU vector, respectively; *P < 0.05 (versus +/+); #P < 0.05 (versus AAV9-L); ^P < 0.05 (versus AAV9-H); &P > 0.05 (versus −/−). NAGLU, α-N-acetylglucosaminidase.

Figure 2

Distribution of recombinant adeno-associated virus 9 (rAAV9)-mediated rNAGLU expression in the central nervous system (CNS) and somatic tissues of mucopolysaccharidosis (MPS) IIIB mice after an intravenous (IV) rAAV9 vector injection. Tissues from rAAV9-CMV-hNAGLU-treated MPS IIIB mice (6 month postinjection) were assayed for hNAGLU by immunofluorescence. Red fluorescence: hNAGLU-positive cells. Blue fluorescence (4′,6-diamidino-2-phenylindole): nuclei. (a) CNS; A. mouse treated with 5 × 1012 vg/kg vector; B. mouse treated with 2 × 1013 vg/kg vector; C–H. mouse treated with 2 × 1013 vg/kg vector following mannitol pretreatment; I, nontreated MPS IIIB mouse. BS, brain stem; CB, cerebellum; CP, choroid plexus; CTX, cerebral cortex; SC, spinal cord; TH, thalamus. Yellow arrowheads: hNAGLU-positive brain cells; red arrowheads: hNAGLU-positive endothelial cells. Bar = 100 µm. (b) Somatic tissues. Red fluorescence: AAV9, MPS IIIB mouse treated with 2 × 1013 vg/kg vector; NT, nontreated MPS IIIB mouse. A. Hrt, heart; Liv, liver; Mus, skeletal muscle. (quadracep). Yellow arrowheads: hNAGLU-positive cells (hepatocytes, myocytes, cardiomyocytes). B. INT, intestine; ME, muscularis externa; Sm, submucosa; +TB, toluidine blue staining. Yellow arrowheads: rNAGLU-positive neurons of myenteric plexus and submucosal plexus. Red arrowheads: peritoneal surface of intestine. Black arrows: neurons of myenteric plexus and submucosal plexus. Bar = 40 µm. NAGLU, α-N-acetylglucosaminidase.

Figure 3

Recombinant adeno-associated virus 9 (rAAV9)-mediated expression of functional rNAGLU in tissues. Tissues from mucopolysaccharidosis (MPS) IIIB mice treated with rAAV9-hNAGLU were assayed for NAGLU activity [6 and 9 months postinfection (pi)] (n = 5–6/group). (a) Dose-response. +/+, wt; AAV9-H, AAV9-L, MPS IIIB mice treated with 1.5 × 1013 (AAV9-H) or 5 × 1012 vg/kg (AAV9-L) vector. (b) Impact of mannitol pretreatment. M+/M−, MPS IIIB mice treated with 2 × 1013 vg/kg vector with (M+) or without (M−) mannitol pretreatment. (c) Plasma NAGLU activity (n = 3–4). +/−, heterozygotes. No significant difference in tissue NAGLU activity was detected at 6 and 9 months pi. Data shown are means ± SD of combined data on tissues from mice at 6 and 9 months pi. *P < 0.01 versus +/+ #P < 0.05 versus AAV9-L or M−; +P > 0.05 versus +/+. @P < 0.05 versus +/−. All P values that were <0.01 and majority of P values that were <0.05, were <0.05 after Bonferroni correction. NAGLU, α-N-acetylglucosaminidase.

Figure 4

Significant reduction of glycosaminoglycan (GAG) content in the central nervous system and somatic tissues. Tissues from mucopolysaccharidosis (MPS) IIIB mice treated with rAAV9-hNAGLU were assayed to quantify GAG content (6 and 9 months postinfection (pi)). (a) Dose-response.(b) Impact of mannitol pretreatment. +/+, wt; −/−, MPS IIIB; AAV9-H, AAV9-L, MPS IIIB mice treated with 1.5 × 1013 vg or 5 × 1012 vg/kg vector; M+, M−, MPS IIIB mice treated with recombinant AAV9 vector (2 × 1013 vg/kg) with or without mannitol pretreatment. Data shown are means ± SD (n = 5–6), combining data from tissues collected at 6 and 9 month pi. *P < 0.01 versus +/+ #P < 0.05 versus AAV9-H or M+; ^P < 0.05 versus AAV9-L or M−; +P > 0.05 versus +/+. All P values that were <0.01 and majority of P values that were <0.05, were <0.05 after Bonferroni correction. NAGLU, α-N-acetylglucosaminidase; rAAV9, recombinant adeno-associated virus 9.

Figure 5

Correction of lysosomal storage pathology in the central nervous system of mucopolysaccharidosis (MPS) IIIB mice after intravenous (IV) recombinant adeno-associated virus 9 (rAAV9) gene delivery. (a) Paraffin sections from mice treated with 5 × 1012 vg/kg rAAV9-hNAGLU vector [6 months postinfection (pi)] were stained with toluidine blue. The lysosomal storage lesions are shown as vacuoles. A, C. Nontreated MPS IIIB mice; B, D. rAAV9-treated MPS IIIB mice. BS, brain stem; CB, cerebellum; CTX, cerebral cortex (pyramidal layer); G, granular layer of CB; HP, hippocampus; M, molecular layer of CB; SC, spinal cord (ventral horn motor neurons); TH, thalamus; Red arrows and yellow arrowheads, neurons. (b) Cryostate brain sections (6 months pi) were assayed for lysosomal-associated membrane protein 1 (LAMP-1) (red fluorescence) by immunofluorescence. A. Nontreated MPS IIIB mouse. B, rAAV-treated MPS IIIB mouse; BS, brain stem; CTX, cerebral cortex (pyramidal layer); TH, thalamus. Yellow arrowheads: LAMP-1-positive cells. Blue fluorescence (4′,6-diamidino-2-phenylindole), nuclei. Bar = 20 µm. NAGLU, α-N-acetylglucosaminidase.

Figure 6

Correction of lysosomal storage pathology in the liver of mucopolysaccharidosis (MPS) IIIB mice after intravenous (IV) recombinant adeno-associated virus 9 (rAAV9) gene delivery. Cryostate liver sections from mice treated with 5 × 1012 vg/kg rAAV9-hNAGLU vector (6 months postinfection) were stained with toluidine blue. Lysosomal storage lesions are shown as vacuoles. AAV9, rAAV9-treated MPS IIIB mouse; NT, nontreated MPS IIIB mouse; Red arrowheads, nuclei of hepatocytes. Bar = 20 µm. NAGLU, α-N-acetylglucosaminidase.

Figure 7

Recombinant adeno-associated virus 9 (rAAV9)-mediated correction of astrocytosis and neurodegeneration in mucopolysaccharidosis (MPS) IIIB mice. Brain sections of MPS IIIB mice treated with rAAV9-CMV-hNAGLU vector (6 months postinfection) were assayed for glial fibrillary acidic protein (GFAP) by (a,b) immunofluorescence (IF) and (c) stained with toluidine blue for histopathology. (a) IF images of astrocytes (green fluorescent-GFAP+). (b) Number of astrocytes: Data are means ± SD of GFAP+ cells per 330 × 433 µm on 6–8 IF-GFAP-staining sections/mouse, from three mice/group. (c) Number of purkinje cells: Data are means ± SD of purkinje cells/200 µm (in length) in ansiform lobules in cerebellum on six toluidine blue stained sections/mouse, from three mice/group. AAV9, MPS IIIB mouse treated with rAAV9; BS, Brain stem; CTX, cerebral cortex; NT, nontreated MPS IIIB mouse; ST, striatum; TH, thalamus. *P < 0.01 versus nontreated. NAGLU, α-N-acetylglucosaminidase.