A Cure for Bubble Babies
Michele Taylor (11 AM Micro) likes BONUS! She found this article in the news a few weeks ago. Here is her summary:
Severe combined immunodeficiency (SCID) is an extreme condition describing an absent immune system. The term “bubble boy” was coined from this disease because the victims must live in a sterile environment. 15% of patients have SCID due to ADA deficiency. This enzyme gives white blood cells their immune defenses.
SCID has been found in 1 of every 100,000 births. Typically, children born with this disease are diagnosed by six months old. If not treated, the condition becomes fatal within two years. These children are at high risk for infectious diseases and have declined growth. SCID becomes apparent when the child has signs of “chronic diarrhea, ear infections, recurrent pneumonia, and profuse oral candidiasis.”
Curious about this condition, a UCLA researcher performed an 11-year study on 10 children with SCID. With hopes of restoring the immune system, the children underwent therapy routines. The doctors wanted to decrease blood stem cells that were not making the enzyme adenosine deaminase. The lack of ADA correlated with a lack of white blood cells. Small doses of chemotherapy were used to eliminate the “useless” cells in the bone marrow. Tests were performed on three children in the attempt to restore their immune system. Dr. Kohn, “a professor of pediatrics and of microbiology, immunology and molecular genetics in UCLA Life Sciences Division,” took the study a step further with a type of virus delivery system. Ten patients were utilized for this study.
Up until this point, ADA-deficient SCID patients have had to be injected with the necessary enzyme twice a week. Kohn explains this lifelong process “is very expensive and often doesn’t return the immune system to optimal levels.” Although rare, another treatment for this condition is having bone marrow transplants from matched siblings.
The new study Kohn performed uses a virus delivery system he created in the 90s. It fixes the gene that makes the enzyme for healthy immune systems. During the gene study on the 10 patients, 4 remained on their enzyme replacement therapy. Although no side effects, there was also no restoration in the immune system. Alternately, the enzyme therapy was stopped in the other six patients. Then, before starting the gene therapy, light doses of chemotherapy were given to lower the ADA-deficient cells. Half of these patients had restored immune systems. Kohn and his colleague went on to test the finding in a mouse model with ADA-deficient SCID.
A specific case of Kohn is recalled in the article. A baby boy, diagnosed with ADA-deficiency at 10 months old, was not improving with the enzyme replacement treatment. His symptoms for the disease were pneumonia, constant diarrhea, and an inability to gain weight. Kohn accepted the boy into the gene therapy study. 4 years later, this boy is still thriving with a healthy immune system. The same family of the baby boy came back to Kohn with their 4-month-old daughter. Again, the results were positive. Kohn believes the younger the child is diagnosed and treated, the better the results. The benefit seen in the human trials are considered a valuable fix to this distressing disease.