Ocular Gene Transfer with Self-Complementary AAV Vectors

• Published in: Investigative ophthalmology & visual science Vol. 48; no. 7; pp. 3324 - 3328
• Main Authors: Yokoi, Katsutoshi, Kachi, Shu, Zhang, H. Steve, Gregory, Philip D, Spratt, S. Kaye, Samulski, R. Jude, Campochiaro, Peter A
• Format: Journal Article
• Language: English
• Published: Rockville, MD ARVO 01-07-2007; Association for Research in Vision and Ophtalmology
• Subjects: Animals; Biological and medical sciences; Dependovirus - genetics; Eye and associated structures. Visual pathways and centers. Vision; Female; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation - physiology; Gene Transfer Techniques; Genetic Therapy; Genetic Vectors; Green Fluorescent Proteins - genetics; Mice; Mice, Inbred BALB C; Microscopy, Fluorescence; Pigment Epithelium of Eye - metabolism; Plasmids; Transgenes; Vertebrates: nervous system and sense organs; Eye; Transfer; Ophthalmology; Gene; Ocular; Vector
• ISSN: 0146-0404; 1552-5783; 1552-5783
• DOI: 10.1167/iovs.06-1306

Self-complementary AAV (scAAV) vectors have been developed to circumvent rate-limiting second-strand synthesis in single-stranded AAV vector genomes and to facilitate robust transgene expression at a minimal dose. In this study, the authors investigated the effects of intraocular injections of type 2 scAAV.GFP in mice.
Dose-response experiments were performed to compare conventional single-strand AAV type 2 (ssAAV2) vectors with scAAV2 vectors encoding an identical expression cassette.
Subretinal injection of 5 x 10(8) viral particles (vp) of scAAV.CMV-GFP resulted in green fluorescent protein (GFP) expression in almost all retinal pigment epithelial (RPE) cells within the area of the small detachment caused by the injection by 3 days and strong, diffuse expression by 7 days. Expression was strong in all retinal cell layers by days 14 and 28. In contrast, 3 days after subretinal injection of 5 x 10(8) vp of ssAAV.CMV-GFP, GFP expression was detectable in few RPE cells. Moreover, the ssAAV vector required 14 days for the attainment of expression levels comparable to those observed using scAAV at day 3. Expression in photoreceptors was not detectable until day 28. Dose-response experiments confirmed that onset of GFP expression was more rapid and robust after subretinal injection of scAAV.CMV-GFP than of ssAAV.CMV-GFP, resulting in pronounced expression in photoreceptors and other retinal neurons. Similar results were obtained for intravitreous injections.
These data suggest that scAAV vectors may be advantageous for ocular gene therapy, particularly in retinal diseases that require rapid and robust transgene expression in photoreceptor cells.