Adeno-associated viruses (AAV) engineered to target specific cells in the retina can be injected directly into the vitreous of the eye to deliver genes more precisely than can be done with wild type AAVs, which have to be injected directly under the retina. UC Berkeley neuroscientists have taken AAVs targeted to ganglion cells, loaded them with a gene for green opsin, and made the normally blind ganglion cells sensitive to light. Credit: John Flannery, UC Berkeley
It was surprisingly simple. University of California, Berkeley, scientists inserted a gene for a green-light receptor into the eyes of blind mice and, a month later, they were navigating around obstacles as easily as mice with no vision problems. They were able to see motion, brightness changes over a thousandfold range and fine detail on an iPad sufficient to distinguish letters.
The researchers say that, within as little as three years, the gene therapy—delivered via an inactivated virus—could be tried in humans who’ve lost sight because of retinal degeneration, ideally giving them enough vision to move around and potentially restoring their ability to read or watch video.
“You would inject this virus into a person’s eye and, a couple months later, they’d be seeing something,” said Ehud Isacoff, a UC Berkeley professor of molecular and and director of the Helen Wills Neuroscience Institute. “With neurodegenerative diseases of the retina, often all people try to do is halt or slow further degeneration. But something that restores an image in a few months—it is an amazing thing to think about.”
About 170 million people worldwide live with age-related macular degeneration, which strikes one in 10 people over the age of 55, while 1.7 million people worldwide have the most common form of inherited blindness, retinitis pigmentosa, which typically leaves people blind by the age of 40.