A SAFER way to give drugs to prevent blindness might be to break through the blood-retina barrier that normally prevents molecules in the blood from reaching the retina. At the moment, such drugs have to be regularly injected into the eyeball. This can cause eye infections and even blindness in 1 in 50 cases.
A team led by Matthew Campbell at Trinity College in Dublin, Ireland, has now restored the vision of mice by temporarily weakening this barrier, to let drug molecules injected into the blood slip through. They used a technique called RNA interference (RNAi) to block the production of a protein that helps make the barrier impermeable (PNAS, ).
RNAi therapy is not yet safe in people, however, as it would breach the blood-brain barrier as well as the blood-retina barrier. The team are working on a way to confine the effect to the eye. This involves gene therapy using a modified virus that makes the interfering RNA only in the presence of an antibiotic. After a single injection into the eye, the virus could then be activated once a month by oral antibiotics.
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