Using a harmless virus to insert a corrective gene into mouse blood cells, scientists at St. Jude Children's Research Hospital have alleviated sickle cell disease pathology. In their studies, the researchers found that the treated mice showed essentially no difference from normal mice. Although the scientists caution that applying the gene therapy to humans presents significant technical obstacles, they believe that the new therapy will become an important treatment for the disease.
Sickle cell disease, which affects millions of people worldwide, arises because of a tiny genetic defect in the gene for beta-globin, a protein component of hemoglobin. This defect causes hemoglobin-containing red blood cells to tend to deform, clump and break apart. The resulting clogged blood vessels can lead to cognitive dysfunction by causing small strokes in the brain and cause damage to kidneys, liver, spleen and lungs. The only permanent cure for the disease is a bone marrow transplant to give recipients blood-forming cells that will form normal beta-globin. However, such transplants are rare because of the lack of compatible donors.
Researchers have long known that symptoms of the disease could be alleviated by persistence in the blood of an immature fetal form of hemoglobin in red blood cells. This immature hemoglobin, which usually disappears after birth, does not contain beta-globin, but another form called gamma-globin. St. Jude researchers had found that treating patients with the drug hydroxyurea encourages the formation of fetal hemoglobin and alleviates disease symptoms.
"While this is a very useful treatment for the disease, our studies indicated that it might be possible to cure the disorder if we could use gene transfer to permanently increase fetal hemoglobin levels," said Derek Persons, M.D., Ph.D., assistant member in the St. Jude Department of Hematology.
He and his colleagues developed a technique to insert the gene for gam
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St. Jude Children's Research Hospital