Gene Therapy Beats 'Bubble Boy' Disease

Four children with disorder recover immune functioning

FRIDAY, Dec. 17, 2004 (HealthDayNews) -- Researchers report that gene therapy has successfully treated four children with severe combined immunodeficiency disorder, more popularly known as the "bubble boy" disease.

The finding appears in the Dec. 17 issue of The Lancet.

The genetic disorder first came to public awareness in the 1980s when David Vetter, a Texas boy with severe combined immunodeficiency (SCID), was housed in a bubble to prevent infections before he died.

With SCID, the immune system, especially the white blood cells, don't function properly. Persons with the disorder are at high risk of catching infections.

In the new study, the researchers first removed stem cells, which are immature cells capable of differentiating into many types of cells, from the children's own bone marrow.

"These children are born with a defect in a particular gene," said study co-author Dr. Christof von Kalle, an associate professor of pediatrics and program leader for molecular and gene therapy at the Cincinnati Children's Hospital.

Next, the researchers substituted correct genetic information for the defective information, putting the new genetic material inside a leukemia virus. The leukemia virus served as a gene vector, delivering the gene to the patient's cells, von Kalle explained. "It's also called a gamma retrovirus," he said of the leukemia virus. "These viruses are used because they have the capability of getting into cells without causing disease." Once the genetic material is in the cells, a healthy copy of the gene is made, he said.

After gene therapy, all four children started making the correct T-cells.

"They are back to nearly normal," von Kalle said. "Patients were discharged and living at home."

Von Kalle stops short of calling it a cure. "We don't really know for how long" the gene therapy will be effective, he said. The longest follow-up for gene therapy for SCID, he said, is four years, involving patients in a French trial.

Another gene therapy expert not involved in the study calls the new work both important and exciting. "It confirms the earlier finds that this gene therapy for this devastating disease really works," said Dr. Mark A. Kay, a professor of pediatrics and genetics at Stanford University.

Whether the effects will endure is yet to be determined, he said. "The question is whether this will last permanently or not," he said.

In 2002, a gene therapy study in France was halted after mysterious leukemia-like side effects were found in a 3-year-old boy who underwent the therapy to treat his SCID. While the researchers weren't sure if the gene therapy was to blame for the reaction, they said at the time is might be likely. In animal studies, the risk of such transmission has been reported as very low. The corrective gene used to correct SCID enters the body attached to a virus that theoretically is not supposed to be capable of causing the disease.

More information

To learn more about gene therapy, visit the Human Genome Project.

SOURCES: Christof von Kalle, M.D., associate professor, pediatrics and program leader, molecular and gene therapy, Cincinnati Children's Hospital; Mark A. Kay, M.D., Ph.D., professor, pediatrics and genetics, Stanford University, Palo Alto, Calif.; Dec. 17, 2004, The Lancet
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