Ultrasound-enhanced retinal delivery of engineered viral vectors

The goal of this study was to examine Focused Ultrasound Blood-Retina Barrier Opening (FUS-BRBO) as a method to deliver gene therapy to the eye. We compared AAV.FUS.3, an engineered variant optimized for FUS-enhanced delivery to the central nervous system, and AAV9 for their utility as retinal gene vectors. To achieve this, mouse eyes were insonated by 4.667 MHz FUS in a custom-designed nosecone and vectors administered intravenously. We found 2.1-fold improvement of transduction of AAV.FUS.3 over AAV9 in the insonated area and 19.5-fold improvement over the uninsonated retina. Within that area, the ganglion cell layer showed the highest levels of transduction at 22% for AAV.FUS.3. We observed no gross tissue damage, change in retinal layer thickness, or increase in inflammation markers within the retina. FUS-BRBO has the potential to non-surgically deliver AAV-based vectors to spatially-defined regions of the retina. AAV.FUS.3 showed significantly improved transduction over AAV9 at the same dose. Further research to improve efficiency of delivery to the outer retina could expand the utility of FUS-BRBO.