For infants diagnosed with a rare genetic disorder called X-linked severe combined immunodeficiency or SCID-X1, it is currently treated with bone marrow transplants. These transplants are conducted during the first three months of life - producing an impressive success rate of 90 percent. Doctors recently announced they have a new advanced therapy and these experts are defining it a ‘cure’.
Severe combined immunodeficiency or SCID refers to a group of rare disorders caused by mutations in genes that influence the development and function of important immune cells. Cells - which ultimately fight off certain bacteria, viruses, and fungi.
Many infants with X-linked SCID develop chronic diarrhea, a fungal infection called thrush, and skin rashes. Those affected also develop slower than other children. If left untreated, males with X-linked SCID usually do not live beyond their second birthday. In the United States, all newborns are screened for SCID.
SCID strips infants of an ordinary childhood full of fun and boisterous wonder. Ordinary activities are taboo for these infants - a day at the park, swimming in a pool, even owning a dog. A simple venture outdoors on a spring day puts these infants at extreme risk for becoming gravely ill. This ‘cure’ or advanced therapy which doctors have discovered may give these infants their lives back.
Researchers at St. Jude Children's Research Hospital in Memphis developed an experimental gene therapy that involves harvesting bone marrow stem cells from a child with SCID-X1, inserting the normal gene that is missing in these patients into those cells. Finally, infusing them back into the child so the cells repopulate and restore the immune system.
This treatment initially tested in the 1990s and early 2000s seemed favorable. "Of the 20 patients, they all had an immune recovery," says Donald Kohn, an immunologist at UCLA's Broad Center of Regenerative Medicine and Stem Cell Research. "But, over time, five of them went on to develop leukemia."
NPR explains: Scientists strived to determine how to inject new genes into cells without triggering leukemia, a cancer of blood cells until they succeeded. The gene to correct the problem was inserted into a modified version of HIV, the virus that causes AIDS. That engineered virus can't cause AIDS, and it has been further tweaked to reduce the risk that it could trigger leukemia.
Infants born with SCID often appear quite healthy but are highly susceptible to severe infections - a common cold could be fatal. There are several types of SCID, depending on which gene defect is involved; mutations in the IL2RG gene on the X chromosome cause X-linked SCID or SCID-X1, which primarily affects infant boys.
Presently, patients require monthly infusions of antibodies called immunoglobulins. Jennifer Puck, a pediatrician at UC San Francisco and a collaborator in the latest study, says infants who receive the gene therapy don't need that medication.
Matthew Porteus, a pediatrician at Stanford University states that SCID became acclaimed in the '70s, when the story of David Vetter - affectionately known as the 'Bubble Boy' was chronicled in a documentary. It captured the imaginations of the world. Today, thanks to medical advances made possible by studies of David’s disease, children with SCID often live normal and healthy lives.
Vetter's mother, Carol Ann Demaret shares, “As parents of an afflicted child, the only thing we had in our control was to see that David received the best possible care. We trusted our doctors. We were grateful for the bubble; the bubble was the only treatment option available for David at the time. If it hadn’t been for the bubble, we would not have had him for 12 years. Our goals were to keep David safe, bring the outside in and make sure he felt loved.”