Adeno-associated virus serotype 9 transduction in the central nervous system of nonhuman primates

Abstract

Widespread distribution of gene products at clinically relevant levels throughout the CNS has been challenging. Adeno-associated virus type 9 (AAV9) vector has been reported as a good candidate for intravascular gene delivery, but low levels of preexisting antibody titers against AAV in the blood abrogate cellular transduction within the CNS. In the present study we compared the effectiveness of vascular delivery and cerebrospinal fluid (CSF) delivery of AAV9 in transducing CNS tissue in nonhuman primates. Both delivery routes generated similar distribution patterns, although we observed a more robust level of transduction after CSF delivery. Consistent with previous reports administering AAV9, we found greater astrocytic than neuronal tropism via both routes, although we did find a greater magnitude of CNS transduction after CSF delivery compared with intravascular delivery. Last, we have demonstrated that delivery of AAV9 into the CSF does not shield against AAV antibodies. This has obvious implications when developing and/or implementing any clinical trial studies.

FIG. 1.

Stronger AAV9-GFP transduction in cortex and cerebellum after cisterna magna (CM) injection compared with internal carotid artery (ICA) delivery. Immunostained sections against GFP revealed similar prefrontal to occipital distribution between ICA (a–d) and CM (f–i), although images also show a more robust level of transduction after CM delivery (f–i), especially in the Purkinje cells of the cerebellum (e and j). Images in the right-hand columns for both ICA and CM are higher magnification pictures of images in the left-hand columns. Scale bars: (a–j) left column: 500 μm; (a–d, f–i) right column: 50 μm; (e and j) right column: 200 μm. Color images available online at www.liebertonline.com/hum

FIG. 2.

Presence of AAV9-GFP in peripheral organs. Vascular delivery (i.e., internal carotid artery [ICA]) of AAV9-GFP resulted in higher levels of transduction in the spleen and liver compared with cisterna magna (CM) infusions. Organs obtained from NHPs used in a separate study were included as control tissues, and these tested negative against the GFP transgene. Scale bar: 50 μm. Color images available online at www.liebertonline.com/hum

FIG. 3.

Cell-specific expression after AAV9-GFP infusion. Brain sections were stained for GFP and either a neuronal (NeuN), astrocytic (GFAP, S100), or cortical interneuron (GAD₆₇) marker. Both ICA and CM infusion resulted in the transduction of neurons (a) as well as fibrous and protoplasmic astrocytes (b and c). Interestingly, some GFP-positive cortical interneurons (d) could also be seen but only after CM delivery. Sections were counterstained with DAPI, a nuclei marker. Arrows depict examples of GFP-positive cells expressing the various markers. Scale bar: 50 μm. Color images available online at www.liebertonline.com/hum

FIG. 4.

Lack of AAV9-GFP cortical transduction in NHPs with preexisting anti-AAV antibodies. Brain sections from seropositive (antibody titer >1:200) and seronegative (antibody titer <1:50) NHPs show differences in transduction levels. The presence of preexisting anti-AAV antibodies produces an almost complete abolition of the transgene transduction signal. Insets: Higher magnification images of transduced cells (arrows). Scale bars: low magnification, 500 μm; high magnification, 100 μm. Color images available online at www.liebertonline.com/hum

FIG. 5.

Widespread transduction throughout the brain after cisterna magna (CM) infusion of AAV9-hAADC. Representative images of transduced cortical neurons grouped in clusters through the prefrontal (a), temporal (b), parietal (c), and occipital cortex (d). Arrows indicate magnifications of regions of interest (a–d, and f and g). Most of them were located proximal to blood vessels, suggesting perivascular transport (e). Astrocytic transduction in the cortical white matter (f), cerebellum (double staining; AADC in brown and GFAP in blue) (g), and transduction of Purkinje neurons also in the cerebellum (h). Scale bars: (a, c, e, f, and h) 100 μm; (b and d) 200 μm; (g) 50 μm. Color images available online at www.liebertonline.com/hum