Sometimes rare diseases can let scientists pioneer bold new ideas. It has been the case with a condition that affects fewer than 100 babies a year in the United States. These babies are born without a functioning immune system.
The disease is called severe combined immunodeficiency or SCID. "It became famous in the mid 70's when" Bubble Boy "was described in a documentary film, and I think it caught many people's imagination," said Matthew Porteus, a pediatrician at Stanford University.
David Vetter was the boy who spent most of his short life in a plastic bubble to protect him from infection. He died at the age of 12 in 1984.
All babies born in the United States are now screened for this condition and the best treatment today – a bone marrow transplant – succeeds more than 90 percent of the time. The disease remains a source of great interest to researchers.
"This is one of the diseases where there are probably more doctors and researchers studying the disease than patients who have the disease," says Porteus.
Indeed, European researchers have cured SCID in some patients using a technique called gene therapy. This process involves the removal of defective blood cells from a patient, inserting a new gene using a virus, and then putting the cells back in the body. These cells then build the patient's immune system.
First, this treatment in the 1990s and early 2000s saw very promising.
"Of the 20 patients, they all had immune enhancement," says Donald Kohn, an immunologist at UCLA's broad center of regenerative medicine and stem cell research. "But over time, five of them continued to develop a leukemia."
He says 18 of the original patients are still alive today, but the incident provides an understandable pole throughout the gene therapy area.
Scientists went to work to find out how to inject new genes into cells without triggering leukemia, a blood cell cancer. And they think they've succeeded.
Since then, there has been a gradual improvement in gene therapy. The latest advancement reported in the New England Journal of Medicine Wednesday describes a study of eight infants having a type of SCID called SCID-X1.
The gene to correct the problem was inserted into a modified version of HIV, the virus that causes AIDS. The engineered virus cannot cause AIDS, and it has been further tweaked to reduce the risk of it inducing leukemia.
Gene therapy has been used successfully over the last decade. Scientists at St. Jude's Children's Research Hospital in Memphis changed the procedure for SCID by giving the infants a short course of chemotherapy before introducing the new gene. This helped the new cells to take permanent residence. The children apparently developed healthy immune systems, according to the new study.
"I'm thrilled to see these excellent results," says Ewelina Mamcarz, a transplant physician and first author on the new paper.
"To be able to see these babies in my clinic now as toddlers is very rewarding," she says. "They live normal lives. They are no different from my daughters." Two further infants have been treated since the paper was prepared for publication, the team said.
Standard treatment of SCID is a bone marrow transplant. But the procedure only restores part of the child's immune system. As a result, patients require monthly infusions of antibodies called immunoglobulins. Jennifer Puck, a pediatrician at UC-San Francisco and a collaborator in the latest study, says that babies who have gene therapy do not need the medication.
These children "grow normally, they get cold like everyone else and they get over infections – so I say that's a cure," says Puck.
Of course, she adds that they will be carefully monitored for signs of leukemia and to see if the effect of the therapy is
. She believes that the key to treatment is finding these children early – through newborn screening – before they start to have life-threatening infections. Screening for SCID is now done through the US, although the introduction was gradual and state-by-state.
Prior to screening, these children used to appear in the hospital with life-threatening infections "and now we & # 39; re looking forward to happy, bouncing little newborns who just look normal and they are never sick & # 39; says Puck. "Sometimes their families do not understand just how deeply their immune system is affected."
St. Jude hopes to commercialize his treatment. has an exclusive licensing agreement with Mustang Bio to develop a product, a similar treatment called Stremvelis has already been approved by Europe's equivalent of the Food and Drug Administration, targeting another mutation that causes SCID, but the technique is very similar including the short dose of chemotherapy.
This latest advancement is not only encouraging news for these rare patients. SCID is a test case for all researchers working to develop better gene therapy techniques.
For example, instead of inserting a healthy gene into blood cells, Matt Porteus of Stanford has used a precision generation technique called CRISPR to correct genetic defects in human SCID blood cells. It works in the laboratory, "and this really sets the stage and then for a clinical trial hopefully in the next 12 to 18 months," he says.
All this makes leukemia setbacks from the 1990s feel like a fading memory. Kohn at UCLA says for more than a decade it seemed that the gene therapy area was a dead end.
It has obviously made a comeback and has treated other rare diseases, including adrenoleukodystrophy, a neurologic condition, better known as the "Lorenzo's Oil" disease, following a 1992 movie that highlighted a boy with the condition and his parents' hunt for a cure.
Now with continued progress in treating SCID, "it's just nice to see another success for gene therapy," says Kohn.
You can contact NPR Science Correspondent Richard Harris at firstname.lastname@example.org.