Sometimes rare diseases can make scientists break new ground. This is the case of a condition that affects fewer than 100 babies per year in the United States. These children are born without a functioning immune system.
The disease is referred to as Severe Combined Immunodeficiency (SCID). "It was made famous in the mid-'70s, when the" Bubble Boy "was featured in a documentary, and I think it attracted the imagination of many people," says Matthew Porteus, a pediatrician at Stanford University. David (19659008) Cousin was the boy who spent most of his short life in a plastic bladder to protect him from infection. He died in 1984 at the age of 12.
All born in the United States babies are now being examined for this condition and the best treatment today – a bone marrow transplant – is successful in more than 90 percent of cases. The disease is still of great interest to the researchers.
"This is one of the diseases where more doctors and scientists are likely to examine the disease than patients who suffer from the disease," says Porteus.
In the 1990s European scientists have cured SCID in some patients with a technique known as gene therapy. Defective blood cells of a patient are removed, a new gene is inserted with the help of a virus and the cells are then reintroduced into the body. These cells then build up the patient's immune system.
Initially, this treatment looked very promising in the 1990s and early 2000s.
"Of the 20 patients, all had an immune system," says immunologist Donald Kohn, the broad center for regenerative medicine and stem cell research at UCLA. "But over time, five of them developed leukemia."
He says that 18 of these original patients are still alive today, but the incident burdened the entire area of gene therapy.
Scientists began working to find out how new genes can be injected into cells without causing leukemia, a blood tumor. And they think they have succeeded.
Since then, gene therapy has gradually improved. The most recent raid reported on Wednesday New England Journal of Medicine describes a study of eight infants who have a SCID type called SCID-X1.
The gene suitable for solving the problem was inserted into a gene modified version of HIV, the virus that causes AIDS. The engineered virus can not trigger AIDS, and it has been further optimized to reduce the risk of it causing leukemia.
Gene therapy has been used successfully over the last decade. Scientists at St. Jude's Children's Research Hospital in Memphis modified the procedure for SCID by giving the infants short chemo before introducing the new gene. This helped the new cells to stay permanent. According to the new study, the babies seem to have developed healthy immune systems.
"I am thrilled to see these outstanding results," says Ewelina Mamcarz, transplant physician and first author of the new work.
"Now seeing these babies in my clinic as toddlers is very rewarding," she says. "They live a normal life, they are no different from my daughters." The team says two more babies have been treated since the paper was prepared for publication.
The standard treatment for SCID is a bone marrow transplant. However, this procedure often restores only part of a child's immune system. As a result, patients require monthly infusions of antibodies called immunoglobulins. Jennifer Puck, a pediatrician at UC-San Francisco and one of the newest study, says infants who have received gene therapy do not need these medicines.
These children grow "normally", they get colds like everyone else and they fight infections – so I would say that this is a cure, "says Puck.
Of course, they are carefully monitored for signs of leukemia and the Effect of Therapy Monitoring Abrasion.
The key to their treatment is to find these children early – through neonatal screening – before they get life-threatening infections Screening for SCID is now being conducted by the United States, although the Introduction Gradual and State-to-State
Before the screening was introduced, these children appeared in the hospital with life-threatening infections, "and now we see happy, nimble little newborns who just look normal and are never ill." Puck says, "Sometimes their families do not understand how deeply their immune system is affected."
St. Jude hopes to commercialize his treatment. It has an exclusive license agreement with Mustang Bio to develop a product. A similar treatment called Stremvelis has already been approved by the European Food and Drug Administration. It targets another mutation that causes SCID, but the technique is very similar, including the short dose of chemo.
This recent progress not only encourages the rare patient. SCID is a test case for all scientists working on the development of better gene therapy techniques.
Instead of inserting a healthy gene into blood cells, Matt Porteus at Stanford used a precise gene editing technique called CRISPR to correct for genetic errors in human SCID blood cells. It works in the lab, "and that's really the cornerstone of a clinical trial, hopefully in the next 12 to 18 months," he says.
All this makes the leukemia setback of the 1990s look like a fading memory. Kohn from UCLA says the field of gene therapy has been a dead end for more than a decade.
There has clearly been a comeback and other rare diseases, including adrenoleukodystrophy, treated as "Lorenzo's Oil," after a 1992 film in which a boy was highlighted with the disease, and the hunt of his parents for a cure.
Now, with continued advances in the treatment of SCID, "it's just great to see another success for gene therapy." Kohn says.
You can contact NPR Science Correspondent Richard Harris at firstname.lastname@example.org.