BBC Gene therapy restores sight to dogs

Gene therapy may be helpful in some cases of blindness Dogs born blind because of an inherited disorder have had partial vision restored by revolutionary gene therapy.

There are hopes that the technique might eventually help the small number of children born with the rare condition.

The advance, headed by researchers at the University of Pennsylvania, is published in the journal Nature Genetics.

It is the first time that such gene therapy has proved successful in a large animal.

Gene defect

The condition Leber congenital amaurosis means that children are born either with severely-reduced vision or near-blindness.

The problem is caused by a defect in a gene called RPE65.

This is vital in helping to correctly construct the photo-receptors in the eye which convert light into nerve signals.

Flaws in the gene mean they do not work and the retinas gradually degrade.

The researchers took retinal cells from blind dogs with this genetic disorder.

These were then "infected" with a virus carrying a correct copy of the RPE65 gene.

Viruses reproduce by incorporating their own genes into the genetic structure of host cells, and those used in gene therapy have been modified so they carry no disease threat.

Injected back

The "infected" cells were then injected back into the eyes of the dogs.

The dogs performed well on various tests to see how the eyes were performing.

The eyes responded as well to light and dark stimuli as the eyes of healthy dogs.

The treated animals also managed to avoid obstacles in dim light.

The researchers said they were "optimistic" about restoring some form of vision to children with the condition.

But the team say that long term safety trials on the therapy would have to be completed before testing on humans could begin.

There are still question marks over the safety of gene therapy, although some trials in other fields have been completed in humans with mixed results.

-- Anonymous, April 27, 2001