Gene therapy brings the light to human eyes

A QUANTUM OF SCIENCE

Gene therapy delivers on promise of better sight for congenital degenerative eye disorder

A recent AQOS post described the landmark success of gene therapy in curing congenital color-blindness in monkeys – the first primate study to achieve that success. Now, researchers have concluded a two-year study following the effects of similar gene therapy treatments for a congenital degenerative eye condition... in humans.

Twelve human volunteers with a condition known as Leber's congenital amaurosis agreed to be given gene therapy in one eye. Though multiple genes are responsible for the development of amaurosis, this study chose to replace the patients’ own copy of a gene called RPE65. The protein encoded by the RPE65 gene is located in the retinal pigment epithelium and is involved in the conversion of trans-retinol to 11-cis retinal during phototransduction (the molecular perception of light), which is then used in visual pigment regeneration in photoreceptor cells. Without a functioning copy of RPE65, humans suffer a steady decrease in vision and are often legally blind by the age of five.

In this study, twelve volunteers – five of them children – received a new copy of RPE65 in the cells of one eye. Within two weeks, the treated eyes began to become more sensitive to light, and within a few more weeks, vision began to improve. The younger the patients were, the better they responded. The youngest patient (age 9) had been legally blind before the study, and afterwards experienced a sufficient increase in sightedness that he is able to ride a bicycle and play softball. Older patients had less improvement because their eyes had greater degeneration in their retinal cells. Still, the improvement is marked and has persisted for the duration of the two-year study. Yet to be answered questions are whether the change is permanent, and what happens if the same therapy is given to the patients’ other eye.

Gene therapy is a field rapidly outstripping medical practitioners’ ability to conduct relevant trials, but this success augurs well for medical and financial support for future studies.

For more information:

Gene therapy transforms eyesight of 12 born with rare defect (LA Times)

Safety and Efficacy of Gene Transfer for Leber's Congenital Amaurosis (New England Journal of Medicine, Maguire et al)

Leber’s congenital amaurosis (Wikipedia)

RPE65 gene (Wikipedia)

Adenovirus-based gene therapy (Wikipedia)

© AQOS / P. Smalley (2009)
Reproduction with attribution is appreciation

A Cure for the Common Cancer

A QUANTUM OF SCIENCE

What can the common cold do to help fight cancer?

Behold one of the most successful organisms in the history of the world: the humble adenovirus, better known as the cold. Human have recorded suffering from this virus since at least Hippocritas, and likely much earlier. Every year humans around the world come down with runny noses, coughs and fevers associated with the cold. And then they spread it to others, and recover - until the next round. Adenoviruses are among the handful of true success stories in biology. Now, scientists have found a way to harness the infectivity of the common cold to make it serve a therapeutic function, not an epidemiological one.

Recently, a group of scientists led by Dr. Leonard Seymour of Oxford University reported successfully removing the "disease" genes from a adenovirus and replacing them with genes for cancerous proteins. Why would this help? In the same way that your body's immune system eventually learns to recognize and attack normal adenoviruses that manage to infect you, the modified adenovirus contains cancer-linked genes that provide the immune system with the opportunity to "learn" that these proteins are invaders to be fought, potentially turning the immune system into the most potent and selective anti-cancer fighter possible.

Scientists have managed similar feats before but to do so they have had to weaken the virus, making it less effective at stimulating the immune system and teaching it to recognize cancer proteins as invaders to be fought. With this achievement, Dr. Seymour and his collaborators have taken a large step forward into a burgeoning field of therapeutics drawn from biological strategies older than humanity itself.

For more inforation:
http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1000440

(C) AQOS / Peter Smalley (2009)