BBC NEWS
'Dramatic results' in eye gene op
US scientists have
claimed success using gene therapy to
try to reverse a severe inherited sight disorder.
They injected material
containing a corrective gene into
the eyes of three patients with Leber congenital amaurosis (LCA).
The journal Proceedings
of the National Academy of Sciences
reports all three showed signs of "significant" improvement in their vision.
UK researchers carried
out a similar procedure on three
patients last year.
They believe the method
could be ready for use within two
years to treat people suffering from some
inherited diseases of the retina, which
affect 20,000 people in Britain.
Within three years,
they believe it could be ready for testing
on people who suffer age related macular
degeneration, a condition that affects 500,000
Britons.
The paper adds to the
body of evidence supporting the value
of gene therapy for people with inherited disease
Dr James Bainbridge
Institute of Ophthalmology
Gene therapy works on a
simple principle - to replace a
malfunctioning gene, and restore function to a
part of the body affected by a genetic
disorder.
In practice, however,
it has proved very difficult to find
ways to introduce the new gene copies in the
correct tissues, and experiments in
animals have had mixed results.
In the eye, however,
gene therapy has shown more promise.
LCA affects
approximately one in 80,000 people, causing
progressively worsening vision, often starting in the first few years of life.
It is responsible for
one in 10 severe sight disorders in
children.
A fault in the RPE65
gene is to blame, and the gene therapy
injects working copies of the gene into the back of the eye.
Just 30 days after the
treatment was delivered into one
eye of each of the three young adults involved in
the US study, the improvements
could be measured.
The researchers, from
Pennsylvania University, the University
of Florida and Cornell University, suggested that
the function of "cones" in the
retina, which are used in daytime and colour
vision, could be boosted up to 50-fold
- a "dramatic" improvement in function.
However, vision in the
treated eyes was not perfect - with
the patients showing an abnormally slow adaptation to low light levels.
UK first
In the UK, scientists
and doctors at the Institute of Ophthalmology
and Moorfields Eye Hospital in London have been
working for some years on a similar
approach.
In 2007, they were the
first to perform a gene therapy operation
on three people with LCA, and earlier this year
reported significant improvement
in one of these.
Dr James Bainbridge,
one of the Institute of Ophthalmology
researchers involved, said the US findings were a
step forward, helping to fine tune
the technique and maximising the chances of success.
He said: "This paper is
important because it provides further
evidence that gene replacement therapy can
improve vision in people with this form
of LCA.
"It also confirms the
prediction that the extent of improvement
depends on the number of surviving target cells
at the time of intervention, and
shows that both rod and cone photoreceptor cells can benefit.
"The paper adds to the
body of evidence supporting the value
of gene therapy for people with inherited disease."
Professor Robin Ali,
who also worked on the UK study, said
the latest paper gave scientists a much better
idea of what dose of gene therapy
would give the best results.
He said: "We can now
begin to find out how much useful vision
is restored by improving retinal sensitivity and
whether the results are better in
young children when we treat the whole retina using a high dose."
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