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Genetic therapy for hereditary emphysema.

Emphysema is not, as many think, solely a smoking-related disease. About 20,000 to 40,000 people in this country are genetically incapable of producing a particular type of protein that protects the lungs from damage against a certain enzyme that corrodes the lung's lining. This enzyme, called neutrophil elastase, is what causes the emphysema, and you don't have to be a smoker to get it (usually when one is in the 30s or 40s). About one in 50 Americans are unable to pass along the gene that produces the protecting protein, alpha-antitrypsin, to their children. As a result, only 52 percent of 18-year-olds born with this condition are expected to live to age 50 (compared to 93 percent of the general population). Only 16 percent are likely to make it to age 60, compared with 85 percent of the general population. Those individuals with this condition who smoke have an even lesser chance of survival.

Speaking at the American Lung Association's Second Annual Science Writers' Forum in Annapolis, Md., Dr. Ronald G. Crystal, chief of the pulmonary branch of the National Heart, Lung and Blood Institute in Bethesda, Md., told of recent Institute studies in which the human gene that produces alpha, antitrypsin was injected into mouse cells that were in turn injected back into the mice. The study's researchers were later able to detect the protein in the plasma of the mice and, more important, in the lining fluid of their lungs, he said. The researchers were also able to inject the gene into clones of the mouse cells, he said, and to also proliferate the cells throughout each mouse's body.

Crystal is optimistic that, developed properly, such an advance would make obsolete the 1987-FDA-approved therapy of weekly intravenous infusions of the purified protein. These infusions, says Crystal, are inconvenient and expensive (to the tune of more than $30,000 a year per patient), and must be continued throughout the patient's life. There is also the danger, he adds, of the patient contracting the human immunodeficiency virus with this procedure, not to mention the possibility that the present supply of purified alpha-antitrysin may not meet the needs of all patients with the disorders. Crystal warns, however, that if a gene to produce the protein were inserted in the wrong place, it might cause the cells to become malignant, thus destroying the entire purpose of the procedure.

Crystal believes human trials with this procedure will be possible in the next couple of years.
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Publication:Medical Update
Date:Feb 1, 1990
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