Genetic Navigation


The story of an altered-gene experiment at the National Institutes of Health gave heart to many people, but it also demonstrated a critical need. In the first of what will surely become a flood of attempts to repair genetic deficiencies, NIH doctors recently dosed a four-year-old girl suffering a rare immune deficiency with samples of her own white blood cells, altered to produce a critical protein. Now they wait and watch, planning new infusions monthly, hoping the damage to her immune system can be corrected.

The girl suffers from adenosine deaminase deficiency, similar to the ailment that kept a Texas boy confined to a plastic chamber all his life. It's caused by a lack of the gene that makes the adenosine deaminase (ADA) enzyme, needed to clear the blood of dangerous metabolic byproducts that destroy immune cells. Knowing the location of the deficient gene, NIH researchers R. Michael Blaese, W. French Anderson and Kenneth Culver decided to try a repair job.

The doctors removed some of the girl's blood and separated out the T cells, key immune system components. Using recombinant DNA techniques, they inserted a copy of the human ADA gene into a virus specially weakened to prevent disease. Next, they infected the T cells with the virus and grew large quantities of the cells. Tests showed that some of the cells began producing the ADA enzyme, so the scientists moved to the next step: infusion back into the girl's blood. They hope the altered T cells will survive, producing ADA and allowing a bloom of other types of immune cells.

Such work demonstrates the increasing sophistication omodern molecular biology, but it also underscores the need to fill in the blanks in the bioscience picture by pushing forward on the human genome project. Some observers have called this expensive "big science," but the criticism falls short of a practical mark. The amount sought, $108 million for fiscal 1991, is nowhere near the billion-dollar budgets of the manned space station or the superconducting super-collider. And the genome project, now working its way through congressional committees, can provide the bedrock supporting many other kinds of research.

Think how much more rapidly the search for the ADA gene could have gone had an area map of human chromosomes been available. Similarly, the worldwide hunt for the cystic fibrosis gene. When dealing with infectious diseases, knowing where to look for a culprit is half the battle. Such knowledge cannot be less critical when the root cause is a protein-producing gene.

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