The findings are available online in Nature.
By artificially initiating a DNA repair process known as homologous recombination, Dr. Matthew Porteus of UT Southwestern, working with scientists from Richmond, Calif.-based Sangamo Biosciences, was able to replace a mutated version of the gene that encodes a portion of the interleukin-2 receptor (IL-2R) in human cells, restoring both gene function and the production of the IL-2R protein. Mutations in the IL-2R gene are associated with a rare immune disease called severe combined immunodeficiency disease, or SCID. Children with SCID are unable to successfully fight off infections, and must constantly live in a germ-free environment. Their lifespans are usually shortened by systemic infection, and while bone marrow transplants can be used to treat the disease, they are not always successful.
"SCID is ideal for this sort of therapy because you only need to correct the defect in a small number of immune cells to fix the problem," said Dr. Porteus, assistant professor of pediatrics and biochemistry at UT Southwestern. "This is called selective advantage; the healthy cells grow and divide preferentially over the mutant ones."
Previous gene therapy attempts for SCID have been only moderately successful because of technical difficulties in the delivery method. In one instance, the correct IL-2R gene was delivered to mutant cells of SCID children by a disabled virus, but some subsequently developed leukemia because the virus inadvertently turned on a cancer gene.
Dr. Porteus' strategy differs fundamentally from previous gene therapies because it essentially replicates the natural process, which is more accurate. This a
Contact: Megha Satyanarayana
UT Southwestern Medical Center