Fixing a body’s broken genes is becoming possible

DNA vaccine and Gene therapy techniques are similar. (Photo credit: Wikipedia)

IT SOUNDS like science fiction, and for years it seemed as though it was just that: fiction.

But the idea of gene therapy—introducing copies of healthy genes into people who lack them, to treat disease—is at last looking as if it may become science fact.

The field got off to a bad start, with the widely reported death of an American liver patient in 1999. In 2003 some French children who were being treated with it for an immune-system problem called SCID developed leukaemia. Since then, though, things have improved. Indeed one procedure, for lipoprotein lipase deficiency (which causes high levels of blood fats, with all the problems those can bring), has been approved, in Europe, for clinical use.

The most recent success, announced last month in the Lancet, was of an experimental treatment for choroideremia, a type of blindness. This is caused by mutation of the gene for a protein called REP1. Without REP1, the eye’s light receptors degenerate. Robert MacLaren of Oxford University used a virus to deliver working versions of the REP1 gene to the most light-sensitive part of the retina. Five of the six participants in the trial duly experienced an improvement in their sensitivity to light. Two were so improved that they could read more letters than previously on a standard eye chart.

Dr MacLaren’s work complements that of Albert Maguire and Jean Bennett at the University of Pennsylvania, who use gene therapy to treat another eye disease, Leber’s congenital amaurosis. A defective version of a gene called RPE65 means that, in this condition, retinal cells are starved of vitamin A, which also causes blindness. Putting normal copies of RPE65 into the retina leads, as with REP1, to greater light sensitivity and—sometimes—clearer vision.

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The Latest on: Gene therapy

via  Bing News


Sight Seen: Gene Therapy Restores Vision in Both Eyes

Packaging system for producing recombinant ret...

Image via Wikipedia

Two doses of gene therapy restore vision to three women who were born nearly blind

Gene therapy has markedly improved vision in both eyes in three women who were born virtually blind. The patients can now avoid obstacles even in dim light, read large print and recognize people’s faces. The operation, researchers predict, should work even better in children and adolescents blinded by the same condition.

The advance, reported in the February 8 issue of Science Translational Medicine, extends earlier work by the same group. Between 2008 and 2011, Jean Bennett of the University of Pennsylvania’s Mahoney Institute of Neurological Sciences and her colleagues used gene therapy to treat blindness in 12 adults and children with Leber’s congenital amaurosis (LCA), a rare inherited eye disease that destroys vision by killing photoreceptors—light-sensitive cells in the retina at the back of the eye. Typically, afflicted children start life with poor vision, which worsens as more and more photoreceptors die.

The treatment grew out of the understanding that people with the disorder become blind because of genetic mutations in retinal cells. One mutated gene that causes the disorder is named RPE65. An enzyme encoded by RPE65 helps break down a derivative of vitamin A called retinol into a substance that photoreceptors need to detect light and send signals to the brain. Mutant forms of RPE65 prevent the production of this enzyme in a “nursery” layer of cells called the retinal pigment epithelium, which is attached to the retina and nourishes photoreceptors by breaking down retinol, among other cellular services.

In the initial study, retina specialist and Bennett’s co-author Albert Maguire of Penn Medicine injected a harmless virus carrying normal copies of RPE65 into an area of the retinal pigment epithelium, which subsequently began producing the enzyme. In each of the 12 patients, Maguire treated one eye—the one with worse vision. Six patients improved so much they no longer met the criteria for legal blindness.

In the new study, Maguire injected the functional genes into the previously untreated eye in three of the women from the first group. Bennett followed the patients for six months after their surgeries. The women’s vision in their previously untreated eye improved as soon as two weeks after the operation: They could navigate an obstacle course, even in dim light, avoiding objects that had tripped them up before, as well as recognize people’s faces and read large signs. Bennett showed that not only were the women’s eyes much more sensitive to light, their brains were much more responsive to optical input as well. Functional magnetic imaging showed regions of their visual cortices that had remained offline before gene therapy began to light up.

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