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Brian C Gilger, Allison Blanchard, Elizabeth Crabtree, Liujiang Song, Jacklyn Salmon, Matthew Hirsch; Intrastromal injection using a 31 gauge or precise corneal injection (PCI) needle for gene therapy. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1327. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Gene therapy targeting cornea disease has led to the need for precise corneal drug delivery. Use of standard needles (ie, 31G) results in variability in drug distribution and efficacy. For consistent corneal drug delivery, a purpose-designed precise corneal injection (PCI) needle was developed. This study was designed to compare drug distribution following use of a standard 31G or PCI needle.
A 31G or PCI needle was used for instrastromal injections (ISI) in anesthetized rabbits. The right eye received 25μL of AAV8-GFP (1e9 viral genomes [vg]) and the left eye 25μL of saline (n=6 each injection). On days 0, 1-6, 9, 14, and 16, slit lamp biomicroscopy, pachymetry, and intraocular pressure were performed. Additionally, in vivo GFP expression was done on days 6, 9, and 16. Following euthanasia on day 18, eyes were analyzed histologically for GFP expression by immunofluorescence (IF) or qPCR analysis. Serum neutralizing antibody to vector capsid was analyzed, Additionally, peripheral vg biodistribution was assessed by qPCR in peripheral blood, lymph nodes, and body organs.
Of 12 ISIs made with 31G needle, 5 resulted in anterior chamber (AC) perforations, 12 had injection site drug leakage, but 10 achieved good ISIs. In comparison using a PCI needle, only 1 injection was intracameral, 6 eyes had injection site drug leakage, and 10 achieved good ISI injections. Using either the 31G or PCI needle, mean ocular inflammatory scores, IOP, and corneal thickness returned to near baseline by 24 hours and normalized in all eyes by 5 days after injection. Although area of corneal GFP was not significantly different in eyes injected with 31G or PCI needles, the % area of the corneal infiltrated was 14-18% immediately after injection, but % area of corneal GFP expression was nearly 50% by day 16. Viral genome copies were higher in peripheral tissues using 31G compared to the PCI needle.
ISIs using the PCI needle were simple, easy to perform, and compared to the 31G needle, resulted in less leakage, less variability, and fewer AC injections; all parameters important for gene therapy to limit off-target tissue exposure of the virus and transgene. Although area of corneal infiltration after ISI and GFP expression were similar with the two needle types, the PCI needle decreased drug dose variability, increased target tissue drug levels, and provided a simple method for dosing.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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