Madsen Pirie

Gene therapy has been used to operate on people with damaged retinas.  It has involved using naturally occurring viruses to repair damaged light-sensing cells, but the problem was that it involved direct injection into the eye, a process that carries its own risk of damage by interfering with the eye’s photoreceptors.  The new process involves selecting from random mutations induced in the laboratory the one most effective at taking the therapy to its target by itself.

The researchers produced millions of random variations of the adeno-associated virus, a harmless virus often used as a vector for gene therapy. From this vast pool, they ultimately identified the single strain that was the best at delivering new genes into damaged retinas.

They injected millions of viruses into the aqueous fluid of the eyes of retina-damaged mice.  A subsequent examination of the retinas of the mice showed which strains had successfully made their way most effectively to the rodents’ retinas.  Repeating the process led them to identify a single strain best at delivering the new genes where they were needed.  They report that the virus carried its material across the retina, which “glued itself together” and saw its response to light restored.

It is still experimental.  It works with monkeys, though not as effectively as with mice, so the team is working to locate a virus strain that will do a similar job in primates.  The next step will be to try using the technique to restore sight to human patients.

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