Abstract
Purpose::
One disadvantage of adeno-associated viral (AAV) vectors is that onset of expression is delayed for several weeks because of the need for complementary strand synthesis. This disadvantage has recently been circumvented by the development of self complementary AAV (scAAV) vectors. The purpose of this study is to investigate the effects of intraocular injections of type 2 scAAV.GFP in mice, and make dose-response comparisons with type 2 single strand AAV (ssAAV) vectors containing the same expression cassette.
Methods::
Subretinal and intravitreous injection of scAAV.GFP and ssAAV.GFP was performed to adult Balb/C mice. Three, 7, 14 and 28 days after injection, eyes were enucleated and flat mount or cryosection was made.
Results::
Subretinal injection of 5 x 108 vp of scAAV.GFP resulted in expression of GFP in almost all retinal pigmented epithelial (RPE) cells throughout the area of injection by 3 days and strong diffuse expression by 7 days. There was strong expression in all cell layers of the retina at 14 and 28 days. Three days after subretinal injection of 5 x 108 vp of ssAAV.GFP, expression of GFP was detectable in occasional RPE cells and did not become comparable to the day 3 expression seen for scAAV until day 14. Expression in photoreceptors was not detectable until day 28. Dose dilution experiments confirmed that GFP expression was more rapid and more robust after subretinal injection of scAAV.GFP compared to ssAAV.GFP; there was good expression in photoreceptors and other retinal neurons after injection of 107 vp of scAAV.GFP. Results for intravitreous injection paralleled those for subretinal injections with scAAV vectors providing more extensive and earlier onset expression than ssAAV vectors.
Conclusions::
scAAV vectors may be advantageous for some ocular gene therapy applications, particularly those requiring efficient transduction in photoreceptors, rapid onset of expression, or high level expression.
Keywords: gene transfer/gene therapy • retinal pigment epithelium • ganglion cells