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http://www.theglobeandmail.com/life/health/monkeys-see-red-after-gene-therapy/article1290015/

Monkeys see red – after gene therapy

New research suggests there may be a way to correct vision disorders
such as colour blindness, long thought to be incurable in adults

Dakhshana Bascaramurty

Globe and Mail
Last updated on Wednesday, Sep. 16, 2009 02:56PM EDT

Strawberries coloured crimson, grapes tinted deep purple and limes
shaded green. For some of the estimated 422,000 Canadians who suffer
from colour blindness – the most common genetic disorder – the true
colour of those fruits is often replaced by dull shades of grey.

But new research published in the most recent issue of the journal
Nature suggests there may be a way to correct vision disorders such as
colour blindness, which were long thought to be incurable in adults.

A team of scientists from the University of Washington and the
University of Florida have brought full-colour vision to two adult
squirrel monkeys that suffered from red-green colour blindness using
gene therapy. Because monkeys and humans have very similar retinas,
the researchers believe the techniques they used could improve the
vision of humans, too.

The monkeys were trained to do the Cambridge Colour Test, the standard
test used to detect colour blindness in humans. They were presented
with three panels on a monitor – two were blank and one had a pattern
of coloured dots on it – and had to touch their noses to the panel
with the pattern. If they were correct, they were rewarded with a sip
of grape juice, but if they were wrong, the researchers played a
buzzing sound.

Because the monkeys were colour blind, they continually guessed and
had a success rate of about 33 per cent, said William Hauswirth, one
of the study's authors and a professor of ophthalmology and molecular
genetics at the University of Florida.

Then, scientists injected each monkey's retina with a human virus that
contained the gene that allows the eye to detect red. They also
injected a piece of DNA to regulate how the gene is made into protein.
They anticipated the monkeys would open their eyes to a new world
after the treatment.

At first, there was no change in the vision test results.

“We started losing hope,” Dr. Hauswirth said.

But after 15 weeks, he and his research partners noticed something
dramatic: the monkeys' success rate jumped to 95 per cent – they could
see red.

“We demonstrated that we can add a new colour response to a primate.
If we can do it in a monkey, we can almost certainly do it in a
human,” Dr. Hauswirth said.

This research could prove useful for those diagnosed with
achromatopsia, what Dr. Hauswirth describes as a “very debilitating”
form of coloured blindness. Sufferers are very sensitive to light and
often have to wear red contact lenses and sunglasses when they are
indoors.

This process could also benefit people suffering from a range of
vision disorders that stem from a problem with the cones in their
eyes, which sense light and are key to colour vision.

“This is the first demonstration that you can treat cones with the
gene they're missing,” Dr. Hauswirth said.

Alex Goulet-Hanssens, a 23-year-old master's student at McGill
University in Montreal, has long eschewed the label “colour blind.”

Though there have been signs of the disorder since he was in Grade 9,
when he mistakenly bought a pair of baby blue cargo pants thinking
they were grey, it was only a few months ago that he was formally
diagnosed with the disorder.

While Mr. Goulet-Hanssens said his colour blindness doesn't bother him
enough to seek treatment just yet, a cure for it would certainly help
him in the laboratory.

As student of chemistry, he sometimes struggles to detect whether a
compound is an acid or a base when he uses phenolphthalein, an
indicator that stays colourless in acidic solutions but turns pink in
basic ones. His teaching assistant usually comes to his aid to tell
him if it's pink or not.

He said it may also be nice to pick out clothes that don't clash on his own.

“I learned very early on that I needed female friends with me to come
shopping,” he said with a laugh. “Even if I thought something was in
the ballpark, I would be wrong.”