New Insights Chart Course in Fight Against Hemophilia
Study in latest issue of Journal of Biological Chemistry
October 21, 1999
More than 20,000 people in the country have hemophilia A, which leaves them prone to excessive bleeding from minor injuries because their blood does not efficiently clot in a wound. Unfortunately, the only treatment available proves ineffective for many hemophiliacs because the patient's own immune system sabotages doctors' efforts. Researchers at the University of Rochester Medical Center and the American Red Cross have found how the immune system neutralizes the therapy in a study appearing in the Journal of Biological Chemistry. The findings are a first step toward a more effective treatment for those suffering from hemophilia.
"To help hemophiliacs, doctors inject a protein called Factor VIIIa (F8) which helps the blood clot properly," explains Philip J. Fay, Ph.D., lead author of the study and professor of Biochemistry and Biophysics at the University of Rochester. "The problem is that the immune system sees the new protein as an invader and often attacks it before it can do much good. But as we learn how the immune system is stopping F8, we should be able design ways to get around it."
Healthy people naturally produce F8 and the immune system leaves it alone because the protein is not foreign.
Like a magnet, a certain part of the F8 protein is attracted to another protein in the blood called Factor IXa (F9) and once they meet and bind together, they ensure that the blood clots properly. In type A hemophiliacs the F8 protein is missing or defective, so doctors inject a dose of healthy F8. But Fay found a problem: that "magnetic" part of F8 also attracts the immune system's antibodies, which often bind to it before F9 can, leaving the patient once again without any effective means of stopping severe blood loss.
Knowing that the immune system is attracted to that "magnetic" part of F8 means that doctors may be able to create a synthetic F8 that still binds to F9 the way it should, but does not attract the immune system antibodies. Such a treatment would likely be more effective and much less expensive than the current treatment, which ranges from $50,000 - $100,000 a year for a single patient.
"Hemophilia A is the most common of the severe of the inherited bleeding disorders," says Fay. "One in every 5-10,000 men will be born with this disease, and about 20 percent of them will develop this immunity to current treatments. For them, there aren't very many treatment options."