avid Vetter, the famous “bubble boy” of the 1970s, had to live in a plastic pod, eating sterilized food and wearing sterilized clothes, to avoid the everyday germs that can be fatal to those with X-linked severe combined immunodeficiency (SCID), a rare immune disorder that affects an estimated 1 in 100,000 people, primarily boys.
But if he were born today, Vetter would likely have been the perfect candidate for a new gene therapy technique that seems to get the immune systems of SCID patients back on track. And while previous genetic treatments had been performed on infants, this new approach works in teenagers and young adults, according to a small but promising study published Wednesday.
Why it matters:
The earliest gene therapy for SCID kept patients alive, but it also had the nasty side effect of sometimes causing leukemia. Even when researchers tweaked the virus they were using as a vehicle for the genetic change, making it safer, the therapy only restored the function of certain kinds of immune cells. That meant patients were still sick, and needed regular injections of pathogen-fighting immunoglobulins to make sure that their bodies could recognize dangerous microbes.
What they did:
To overcome this problem, researchers turned to a newer viral vehicle, a lab-grown version of HIV with the dangerous innards torn out. They used this to insert healthy genes into stem cells extracted from each patient’s bone marrow. Unlike the old virus, this new one didn’t require the stem cells to go through a complete cycle of reproduction in order to make its way into the cells’ nuclei. That meant that more of the healthy genes got into more stem cells, which could then be re-injected into the patient.
For the five recipients of this gene fix, doctors also prepared the bone marrow ahead of time. Like gardeners cutting away last year’s brush before planting new seeds, they gave each patient bouts of chemotherapy to wipe out some of their original stem cells, which helped make room for the new and improved ones.
What they found:
“Every single one of these five patients had profound improvements in their quality of life,” said Dr. Harry Malech, chief of the genetic immunotherapy section at the National Institute of Allergy and Infectious Diseases, who led the study and described the results in the journal Science Translational Medicine.
For the two patients in their early 20s, for whom the treatment was performed long enough ago to produce laboratory data, the gene therapy also caused multiple types of immune cells to regain function. This allowed them to finally shake chronic norovirus infections, which had given them persistent diarrhea.
But keep in mind:
“The data is really on two patients,” said Bobby Gaspar, a SCID researcher at University College London, who was not involved in the study. “It’s difficult to make very firm conclusions on something like that.”
The bottom line:
Further studies are needed to determine if this new gene therapy technique could be used more widely. And while this study shows that patients could be treated when they are as old as 23, it makes more sense to treat SCID patients in infancy, so as to try to mitigate the problem as early as possible.