Monkey Flu, Monkey Color Blindness Is Removed
Boffins infect squirrel monkeys with a modified cold virus to deliver a gene that lets them see in colour
Two monkeys were cured of colour blindness thanks to gene therapy that one day may open the way to treating eye disorders in humans, scientists said on Wednesday.
The revolutionary technique used a cold virus as a Trojan horse to infect cone-shaped cells in the retina, stealthily delivering a gene that provides a pigment which is sensitive to red.
In 20 weeks after the treatment, the two primates began to acquire full colour vision, according to the paper, published by the British journal Nature.
“It was as if they woke up and saw these new colours. The animals unquestionably responded to colours that had been invisible to them.” said Jay Neitz, a professor of ophthalmology at the USbased University of Washington, who led the work.
ONE IN A HUNDRED
Colour blindness is the inability to distinguish between different hues, particularly between red and green. Instead, these colours show up shades of grey, causing problems for simple everyday tasks such as recognising traffic lights.
Red-green colour blindness is the most common and incurable genetic disease. It affects between five and eight per cent of males and one per cent of women, as per various studies.
More than 13 million Indians suffer from the problem of colour blindness, making them unsuitable for a variety of professions.
The experiment was conducted on two squirrel monkeys (Saimiri sciureus) Dalton and Sam, who had been colour-blind since birth.
The monkeys were given an adapted form of a standard visiontest to find out exactly which out of 16 hues they failed to see.
When the monkeys traced a colour pattern on a computer touch screen, they were given a reward of grape juice.
HOW THEY DID IT
The researchers inserted a human gene called L-opsin into a disabled cold virus and delivered it to the monkeys’ retina through several injections.
The gene colonised cone cells, the most important vision receptors in mammals, adding the missing light-sensitive pigment.
Colour vision in Sam and Dalton has remained stable more than two years after treatment.
It is the first time that a vision disorder has been corrected in primates in which all photo-receptors are intact and healthy.
“Although colour blindness is only moderately life-altering, we’ve shown we can cure a cone disease in a primate, and that it can be done safely,” said co-researcher William Hauswirth.
“That’s extremely encouraging for the development of therapies for human cone diseases that really are blinding,” he added.
The researchers believe this technique could be useful in correcting a variety of known vision disorders. “People who are colour blind often feel that they are missing out. If we could find a way to do this in humans, there would be a lot of people who would want it.” said Professor Neitz.
Gene therapy holds the promise of blocking or reversing inherited diseases. Targeting cone cells could cure common types of blindness such as age-related macular degeneration and diabetic retinopathy
(with thanks MM)
