Abstract
Purpose :
Intrathecal administration of adeno-associated virus type 9 (AAV9) is an approach being utilized to treat an increasing number of neurological disorders, many of which have optic nerve degeneration. We tested the hypothesis that optic nerve (retinal ganglion cell, RGC) transduction occurs in mice along with the widespread brain gene transfer observed with this vector and route of administration.
Methods :
Adult female C57BL/6 mice received a single intra-cerebrospinal fluid (CSF) injection of 4.5x1011 vg scAAV9/CBh-GFP (5 uL total volume) via a lumbar puncture (n=9) or via an injection into the cisterna magna (n=4). Two mice were injected with vehicle as controls. At 1, 2, 3, and 4 weeks post-injection, GFP expression in the retina was visualized using a Micron IV retinal imaging microscope (Phoenix Research Labs). At 4 weeks post-injection, mice were sacrificed and histology was performed to visualize GFP expression in the retina.
Results :
At 1 week following injection, minimal GFP expression was observed in the retina. At 2 weeks, extensive and widespread GFP expression was observed across the retina. Expression peaked at 2-3 weeks, and remained stable to the end of the study at 4 weeks. No appreciable difference was seen between the lumbar intrathecal and cisterna magna routes of administration. By histology, RGCs were transduced. Ongoing studies are in progress to quantify the results and to identify whether non-RGC cells in the retina are also transduced. A qualitative representative image is provided as Figure 1.
Conclusions :
Intrathecal injections are routine outpatient procedures, and intrathecal administration of AAV9 is being evaluated in Phase I clinical trials for Giant Axonal Neuropathy (GAN) and Batten Disease type 6 (clinicaltrials.gov identifiers NCT02362438 and NCT02725580, respectively). Optic neuropathy is a feature of both diseases, and our studies suggest that the current clinical approach has some potential to treat this component of each disease. We propose that intrathecal administration of AAV9 is a translationally-relevant approach for gene transfer to RGCs across the entire retina. However, questions remain as to whether the efficiency is sufficient to provide treatment efficacy and how effectively these results translate from mice to larger animals and humans.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.