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Maureen Neitz, Anita Hendrickson, Michael Lukason, Jay Neitz, Daniel Possin, Gelareh Abedi, Jing Huang, Abraham Scaria, Sam Wadsworth; Accessibility of Retinal Cells to Different AAV Serotypes After Intravitreal Injection in Old Versus New World Primates. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2733.
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© ARVO (1962-2015); The Authors (2016-present)
Adeno-associated virus (AAV) is a promising vehicle for ocular gene therapy but little is known about what cells types are accessible to virus injected intravitreally (IVT) in primate. Here we evaluated this issue for AAV serotypes 2 and 5.
10 animals each received a single IVT injection containing an admixture of two AAVs: one carrying the gene for GFP the other carrying the gene for a chimeric soluble VEGF receptor, sFLT02. All vectors had a ubiquitous chicken beta actin promoter. For each animal, the same serotype, 2 or 5, was injected in both eyes but AAV injected into the right eye had a wild type (wt) capsid, AAV injected into the left eye had a capsid modification (see Table 1). Macaques received 1x1010 vector genomes (vg) of each vector in 50 µL. Marmosets received 8x109 vg of each vector in 10 µL. GFP expression was evaluated histologically, sFLT02 transgene product was measured using a commercially available ELISA.
In macaques, sFLT02 expression was similar for wild type AAV2 and modified AAV2 capsids, and expression with AAV2 vectors was higher than for AAV5; however, AAV5 with modified capsids gave stronger expression than wt AAV5 capsids. ELISA results for sFLT02 in marmosets were inconsistent across animals for AAV5 vectors but modified AAV2 gave higher sFLT02 levels than wt AAV2. All but one macaque eye injected with AAV2 gave strong GFP labeling of ganglion cells around the foveal pit with fewer foveal amacrines, horizontals, bipolars and cones. Scattered labeled ganglion cells and many Mueller cells were present in the mid to far periphery. Pars plana epithelial cells were strongly labeled. The distribution of GFP was similar for eyes treated with wt versus capsid modified AAV5. In marmosets, GFP labeling for eyes treated with AAV2 was similar to macaque but labeling at the fovea was much less pronounced. AAV5 virus gave weak GFP labeling in marmosets, with little or no foveal labeling.
IVT administration of AAV vectors transduces a variety of cell types within the eye including ganglion, amacrine, bipolar, horizontal cells, and to some extent, photoreceptors. Tropism differs among serotypes with AAV2 transducing more cell types than AAV5. While the capsid modifications examined in these experiments did not appear to alter tropism, overall transgene expression level was affected.
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