Abstract
Abstract: :
Purpose: Previously we have used adenovirus to transfer genes encoding vIL-10 into the rat eye, leading to significantly reduced severity of EAU. AAV offers several advantages over adenovirus for gene transfer, including sustained, stable gene expression, and relative lack of pathogenicity and immunogenicity. We investigated the possibility of using an AAV vector, with transgene transcription controlled by the tetracycline-inducible TetON system, to deliver vIL-10 intraocularly in the rat to inhibit EAU. Methods: To study AAV-mediated intraocular gene transfer, Lewis rats were injected intravitreally (10 µl) or subconjunctivally (20 µl) with AAV-GFP (1x1011 viral particles/ml). Animals were killed 6, 7, 8 and 9 weeks, and 3 months, after injection, and serial 10 µm cryostat sections of eyes were screened for GPF expression by epifluorescence microscopy. In a pilot study, Lewis rats were injected intravitreally with either AAV-TetON-vIL-10 or control AAV-GFP. Transgene expression was induced 5 weeks later by adding doxycycline (DOX) (200 mg/kg/day) to the drinking water. Rats were immunized systemically with S-Ag (30 µg), either on the first day of DOX treatment or 1 week after commencement of DOX (n=4 rats/group). Ocular histopathology and S-Ag-specific systemic immune responses were studied 3 weeks post-immunization. Results: Subconjunctival injection of AAV-GFP did not lead to consistent GFP expression in the orbital or ocular tissues. In contrast, after intravitreal injection of virus, GFP expression was detected in different cell types throughout the retina, in the anterior uveal epithelium and in the optic nerve. Expression was present from 6 weeks after injection and persisted through 3 months. There was a trend (p=0.07) towards photoreceptor rescue in those rats treated with AAV-TetON-vIL-10 that started DOX 1 week prior to S-Ag immunization when compared with AAV-GFP-treated control animals. A similar trend was not observed in the case of the AAV-TetON-vIL-10-injected rats that were dosed with DOX from the day of immunization (p=0.54). Intravitreal AAV-TetON-vIL-10 injection had no effect on the systemic S-Ag lymphocyte proliferation responses of treated rats versus controls. Conclusions: Intravitreal injection of AAV is effective in transferring genes to intraocular tissues. An inducible vector encoding vIL-10 and administered locally may prove useful in the control of experimental uveitis, with possible applications for human disease.
Keywords: uveitis-clinical/animal model • gene transfer/gene therapy • cytokines/chemokines