Gene therapy is a potentially powerful technology to replace faulty disease-causing genes with functional copies. Though not yet a common procedure to treat genetic disease (primarily due to the difficulties of getting it right), there have been major advances. Here is a look at some of them.
Gene Therapy Advances
September 2009: Researchers from the University of Washington cure two colour blind squirrel monkeys. Functioning genes were introduced into the light-sensing cells at the back of the eye. They enabled these cells to be able to distinguish between red and green.
March 2009: Gene therapy and nanotechnology - therapeutic genes were wrapped in nano particles and taken up by cancerous cells in mice. Once inside these cells the genes recognised the toxic environment and produced a protein which destroyed the cancer cells. Healthy normal cells were unaffected. The benefit of this gene therapy approach is that it can target difficult-to-reach tumours in a specific way.
May 2007: Scientists at Moorfields Eye Hospital in the UK carried out a pioneering gene therapy eye operation to restore some vision to a teenager with a degenerative eye disorder. The condition was caused by a faulty gene known as RPE65 that is usually able to help cells at the back of the retina to detect light. However, in this situation the defect stops this from happening and so researchers injected working copies of the gene into the back of the eye. It was a success. Before the operation the teenager, Steven Howarth could not see at nighttime, and eventually he would have lost his vision completely. But after the procedure he could make out objects and road markings, and being a guitarist he can see the frets better. It is also likely that he will not lose his sight as he ages. He was the third person to undergo the experimental test. Two other people did not have their vision restored, but gene therapy may prevent their vision from deteriorating still further.
Further Gene Therapy Advances
August 2006: It was reported that researchers from the National Cancer Institute had achieved sustained regression of advanced melanoma in a patient study. The test subjects had their own immune cells genetically engineered to recognise the cancer cells and destroy them. Blood samples were taken and normal lymphocytes (white blood cells) were genetically engineered into powerful cancer killing cells. In the lab lymphocytes were infected by a retrovirus carrying T cell receptor genes and a person's own modified cells were put back into the patients. When the therapeutic genes were turned on T cell receptors were made which could bind to the surface of tumour cells and activate the lymphocytes to destroy them. Of the 17 patients who took part, two were disease free for more than a year, and most participants had 9-56% of the genetically engineered cells still in their body one month after the procedure. This was the first time that gene therapy was used to successfully treat cancer in humans.
February 2005: Gene therapy was used to cure deafness in guinea pigs. The hearing problems were caused by the destruction of hair cells in the cochlea that translate vibrations into nerve signals. Scientists delivered genes called Atoh1 that re-triggered hair cell growth. They were carried to the cochlea inside an adenovirus. The animals regained up to 80% of their original hearing.