Approximately 100,000 people in the United States have X-linked retinitis pigmentosa, a form of hereditary retinal blindness. This form of blindness is passed down from mothers to offspring, but drastic vision impairments are seen mostly in males. Retinal blindness entails a slow progression of loss of vision. The individual will first lose peripheral and night vision, and then continues to tunnel vision and eventually complete blindness.
Dr. William W. Hauswirth and Dr. Alfred S. Lewin, both professors at the University of Florida, have devised a treatment that may reinstall vision to the individuals who have inherited this unfortunate defect. These doctors have already had success in the beginning stages of a treatment for a less prevalent vision defect that results in blindness, known as Leber’s congenital amaurosis, but their new treatment presents the opportunity for a bigger impact because hereditary retinal blindness is a much more common vision defect.
Light sensitive cells found in the eye are known as photoreceptors. These cells are necessary for vision. X-linked retinitis pigmentosa occurs when these cells are slowly broken down. This starts in the early stages of life, and as the aging process continues the affected individual slowly begins to lose his or her sight. Complete blindness usually occurs around the second decade of life. Imagine being a young teenager and literally watching the world disappear around you. This is what motivated these doctors to try and find a treatment for this type of blindness.
The strategy for this treatment was to create a functioning copy of the affected gene and then turn it into a virus. The “virus” would then be used as a delivery system to the part of the eye where the malfunctioning form of this gene is located. An “on-off switch” was also copied and would help turn the “virus” on once it was in place. This would result in the functioning gene releasing necessary proteins that would activate the otherwise damaged light sensitive cells.
This type of therapy that Dr. Hauswirth, Dr. Lewin, and fellow coworkers from the University of Pennsylvania have derived falls under the heading of “gene therapy”. The researchers were able to inject these functioning genes into canines that had vision defects that mirror the retinal heritable blindness. The functioning genes made their way only to the eye where they were needed. They were not found anywhere else within the body. The researchers are hopeful that this is how the treatment will also work within humans.
Although this may seem like an instant cure, there are numerous steps and procedures that these Florida and Pennsylvania researchers still need to follow through with in order to create a working treatment.
So what’s the game plan?
The researchers plan on continuing to develop the gene therapy and creating a version of the “virus” that is completely safe to humans. A large scale clinical trial will then have to occur, which will hopefully provide evidence that a treatment for this type of heritable vision defect has been found.
William A. Beltran, Artur V. Cideciyan, Alfred S. Lewin, Simone Iwabe, Hemant Khanna, Alexander Sumaroka, Vince A. Chiodo, Diego S. Fajardo, Alejandro J. Román, Wen-Tao Deng, Malgorzata Swider, Tomas S. Alemán, Sanford L. Boye, Sem Genini, Anand Swaroop, William W. Hauswirth, Samuel G. Jacobson, Gustavo D. Aguirre. Gene therapy rescues photoreceptor blindness in dogs and paves the way for treating human X-linked retinitis pigmentosa. Proceedings of the National Academy of Sciences, 2012; DOI: 10.1073/pnas.1118847109
University of Florida Health Science Center. “Researchers develop gene therapy that could correct a common form of blindness.” ScienceDaily, 23 Jan. 2012. Web. 6 Mar. 2012.