Easy and effective therapy to restore sight: Engineered virus will improve gene therapy for blinding eye diseases

June 12, 2013 Researchers at UC Berkeley have developed an easier and more effective method for inserting genes into eye cells that could greatly expand gene therapy to help restore sight to patients with blinding diseases ranging from inherited defects like retinitis pigmentosa to degenerative illnesses of old age, such as macular degeneration.

Unlike current treatments, the new procedure is quick and surgically non-invasive, and it delivers normal genes to hard-to-reach cells throughout the entire retina.

Over the last six years, several groups have successfully treated people with a rare inherited eye disease by injecting a virus with a normal gene directly into the retina of an eye with a defective gene. Despite the invasive process, the virus with the normal gene was not capable of reaching all the retinal cells that needed fixing.

"Sticking a needle through the retina and injecting the engineered virus behind the retina is a risky surgical procedure," said David Schaffer, professor of chemical and biomolecular engineering and director of the Berkeley Stem Cell Center at UC Berkeley. "But doctors have no choice, because none of the gene delivery viruses can travel all the way through the back of the eye to reach the photoreceptors -- the light sensitive cells that need the therapeutic gene.

"Building upon 14 years of research, we have now created a virus that you just inject into the liquid vitreous humor inside the eye, and it delivers genes to a very difficult-to-reach population of delicate cells in a way that is surgically non-invasive and safe. "It's a 15-minute procedure, and you can likely go home that day."

The engineered virus works far better than current therapies in rodent models of two human degenerative eye diseases, and can penetrate photoreceptor cells in monkeys' eyes, which are like those of humans.

Schaffer said he and his team are now collaborating with physicians to identify the patients most likely to benefit from this gene delivery technique and, after some preclinical development, hope soon to head into clinical trials.

Schaffer and John Flannery, UC Berkeley professor of molecular and cell biology and of optometry, along with colleagues from UC Berkeley's Helen Wills Neuroscience Institute and the Flaum Eye Institute at the University of Rochester in New York, published the results of their study on June 12 in the journal Science Translational Medicine.

Harnessing a benign virus for gene therapy

Three groups of researchers have successfully restored some sight to more than a dozen people with a rare disease called Leber's congenital amaurosis, which leads to complete loss of vision in early adulthood. They achieved this by inserting a corrective gene into adeno-associated viruses (AAV), and injecting these common but benign respiratory viruses directly into the retina. The photoreceptor cells take up the viruses and incorporate the functional gene into their chromosomes to make a critical protein that the defective gene could not, rescuing the photoreceptors and restoring sight.

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Easy and effective therapy to restore sight: Engineered virus will improve gene therapy for blinding eye diseases