In a striking success for gene therapy, doctors in Paris gave healthy new immune systems to the baby boys, born with a rare, genetic immune disorder. A fifth boy had his immune system partially repaired and is improving with other treatment.
The five French boys were born with severe combined immunodeficiency, or SCID, an inherited disease that occurs in about 1 in 75,000 births. The best-known victim was David, Houston's famous "bubble boy" who lived in a germ-proof plastic enclosure until his death at age 12 in 1984.
The disease left them unable to fight off infections and dependent on constant antibiotic treatments. Now the boys, followed for up to 2½ years, are thriving. They've even been immunized against some childhood diseases — shots that previously would have killed them.
"This is the first instance in which an otherwise fatal disease has been treated with gene therapy as the only treatment and the disease was reversed," said Dr. Jennifer M. Puck, head of the immunologic genetics section at the National Human Genome Research Institute. "This is exciting and it's important."
The doctors reported initial success with the first two patients two years ago; the update with additional cases in Thursday's New England Journal of Medicine shows the therapy is still working.
The gene therapy was given to the boys in 1999 and 2000 when they were babies, ranging in age from one month to 11 months. The oldest of the boys is now about 4.
Sonia Skarlatos, gene therapy coordinator at the National Heart, Lung and Blood Institute, said the results do not prove the boys' immune systems have been permanently repaired, but it is the longest-lived success in gene therapy so far.
Puck said patients treated with gene therapy for other disorders still need regular, expensive medication to survive.
"This is the one where gene therapy on its own did the job," she said.
The French boys had X-linked SCID, a severe form that strikes only boys. It is the most common form of SCID, accounting for about half the cases.
The boys lacked a protein because of a genetic mutation. As a result, they could not make two types of crucial infection-fighting immune cells, and a third type did not work, leaving their bodies vulnerable to infection.
Many babies with the disorder are now saved with bone marrow transplants, but they need monthly intravenous infusions of immune globulin, antibodies culled from donated blood, for the rest of their lives.
To reverse the gene defect, doctors at Necker Hospital in Paris drew bone marrow from the boys. They culled stem cells from the marrow and mixed them with a harmless virus in which a gene that makes the missing protein had been inserted. After the virus infected the bone marrow cells, millions of each boy's cells were injected into his bloodstream.
Repeated tests showed the boys' bone marrow cells continue to make the immune cells they once lacked. Skarlatos said some of the boys' stem cells still have the defective gene, but enough have the normal one to give them a good immune system.
She said the approach could eventually help cure some other genetic diseases, including hemophilia and another form of SCID.
"In the next five years or so, I would expect to see some results," she said.