may 2006
LCA Gene Therapy in the Egg
First dogs, now chickens! Can humans be that far off? As reported earlier this year, scientists have found a way to restore sight to blind Briard dogs afflicted with Leber's Congenital Amaurosis (read about it here). Now, a University of Florida team has used a similar gene-therapy technique to deliver healthy genes to blind chickens - while still in the egg!
"We were able to restore function to the photoreceptor cells in the retinas of an avian model of a disease that is one of the more common causes of inherited blindness in human infants," said Sue Semple-Rowland, Ph.D., an associate professor of neuroscience with UF's Evelyn F. and William L. McKnight Brain Institute. "The vision capabilities of the treated animals far exceeded our expectations."
Using a technique that sounds simple but actually took twenty years to perfect, the team located then treated LCA in a type of Rhode Island Red chicken known to carry the genetic defect similar to LCA type-1 (or LCA1) in humans. LCA1 consists of a malformed GC1 gene that makes it impossible for the patient to produce an enzyme necessary for sight. The Florida doctors developed viruses that carry healthy GC1 genes, they injected them into the egg, then waited for the results. If all worked well, the viruses would "infect" the chicken's photoreceptor cells with the healthy GC1 gene.
After hatching, they found that of the seven treated chickens, five had near-normal sight and responded to light. That's a 71% success rate!
Dr. Paul A. Sieving, director of the National Eye Institute of the National Institutes of Health, which partially funded the study, said: "This is an interesting gene-transfer technique that appears to restore function to light-sensitive cells in the retina. An approach such as this could lead eventually to a vision-restoring therapy for children who suffer from blinding retinal diseases."
This technique seems to restore sight and slow down retinal degeneration, but degeneration still occurs. Next, researchers need to find a way to stop degeneration all together and, of course, apply this gene-transfer technique to humans.