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Sensational headlines have been streaming across presses for several years now: GENE FOR OBESITY FOUND, SCIENTISTS IDENTIFY GENE LINKED TO HEART DISEASE, or CANCER GENE GIVES HOPE FOR CURE. Each refuels the hope that powerful therapies against such major health threats will soon emerge from the pipeline of medical science. Diagnostics based on genetics are now commonly used, for example, when considering surgery against breast cancer, and in prenatal screening for inheritable diseases. But we're still waiting for a generation of genetic treatments that may provide miraculous cure-alls to our most persistent and pernicious illnesses.
Expectations of genetic medicine surged after a breakthrough in 1990, when four-year-old Ashanthi De Silva from Cleveland became the first gene therapy patient. The girl suffered from a problem called severe combined immunodeficiency (SCID), often dubbed "bubble-boy syndrome" since its sufferers must live in a sterile environment or risk acquiring a life-threatening infection. De Silva's form of SCID was caused by a mutation in the gene for the protein adenosine deaminase, or ADA, an enzyme that is necessary for the immune system. De Silva's body could not produce functioning ADA.
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De Silva's form of SCID was caused by a mutation in the gene for the protein adenosine deaminase, or ADA, an enzyme that is necessary for the immune system.
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In a pioneering experiment, De Silva's doctors gave her healthy copies of the gene that produces ADA. They placed the healthy gene inside a modified virus and allowed the virus to infect blood cells they had drawn from De Silva. They then injected the blood cells back into her body. The girl's new gene started to generate functioning ADA, resuscitating her immune system, and she has since lived a healthy life.
Yet, after this initial success, subsequent gene therapy procedures haven't always been so trouble-free. In De Silva's case, the single healthy gene she received was sufficient to restore her immune system. People who suffer from other single-gene diseases, such as cystic fibrosis, sickle-cell anemia, or hemophilia, may also find help in gene therapy. But many genetic diseases involve the malfunction of multiple genes, and fixing one gene is often a formidable task.
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