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Scientists that have been working on gene therapy for congenital blindness have conducted a study and report that in three adult patients who had previously been treated they have found improvement in seeing in low-light situations. The researchers from the Perelman School of Medicine at the University of Pennsylvania and The Children's Hospital of Philadelphia say that there have been no conflicting effects reported as a result of the study.
In previous studies of gene therapy on different diseases the two treatments had recorded no immune reactions. This cancelled those genes that were administered. This study focused on addressing Leber congenital amaurosis (LCA), a retinal disease resulting in complete loss of vision by adulthood.
Neuroimaging was facilitated to flash a dimly blinking checkerboard pattern in front of the eye which had just recently been treated with the gene. The part of the brain responsible for vision “brightened” as a result of the functional magnetic resonance imaging (MRI), telling us that the brain responded to the eye's sensitivity to dim light.
The patients were administered with a vector, a genetically engineered adeno-associated one form of LCA. LCA is an accumulation of hereditary retinal diseases, in which a gene mutation challenges production of an enzyme necessary for light receptors in the retina.
A trial had previously been conducted using the same gene therapy back in October 2009. Four of these patients were under the age of 11 when treated for the blindness. They only had the eye that was able to see better treated, and the study had evident results; six patients were able to see better, and were no longer considered "legally blind".
Researchers were skeptical that the vector in the eye which had not been treated could possibly result in inflammatory responses that could take away the benefits from the eye that wasn't treated. The eye is somewhat separate from the body's immune system, therefore the concern was not high in terms of the inflammatory responses, however, further testing needed to be done in practice. The concern was that the initial treatment might have caused a vaccine-like immune response that could prime the individual's immune system to react against repeat exposure.
The vector was administered in the eyes of three patients that had been untreated previously. They had all received treatment three years prior. They were then observed for six months after they had been readministered with the vector. The greatest advancements were in terms of light sensitivity, including the pupil's differentiation to light when it viewed in varying intensities. Out of the three patients, only one was unable to able to find their way through an obstacle course in very low-light.
The MRI findings demonstrated improvement in brain responses in the first treated eye, not just the newly treated one.This was likely because the eyes were able to parallel each other in focsing in on the objects they were trying to see.
It is important for further research to be done in order to ensure that gene therapy is an effective and safe way to treat retinal disease in humans.