"Hemophilia is considered an ideal candidate for correction with gene therapy because if you could just raise the factor VIII activity from less than 1 percent of normal to within 5 to 10 percent of normal, the tendency for spontaneous bleeding and need for hospitalization would diminish dramatically," McCray said.
"In the mouse model in our study, we were able to achieve levels of gene expression that converted the hemophilia A in the mouse from a severe to a mild form. The correction lasted 30 weeks -- the duration of the study," he added.
One of the current treatments for hemophilia involves intravenously delivering recombinant (genetically engineered) human factor VIII protein to prevent bleeding episodes. However, the weekly to bi-weekly preventive treatments are extremely expensive, costing up to $500,000 per year. In addition, over time some patients may develop antibodies to the protein, making the treatments less effective.
In earlier studies, McCray's team, which includes Yubin Kang, M.D., at the time a UI assistant research scientist in pediatrics (now a UI resident in internal medicine), targeted the liver because its main functional cells, called hepatocytes, can make the factor VIII protein and secrete it into the bloodstream. However, the investigators recognized the need to target the liver more effectively.
"It has been difficult to conclusively identify the cells that normally make factor VIII," McCray said. "Hepatocytes may not be the main source of this protein, but they are relatively easy to target. So we aimed to find a way to get these cells to make more of it. In effect, we're using the hepatocytes as a factory to make this protein and secrete it into the bloodstream."
To better target the hepatocytes in the mice, the team took the disabled protein coat from the baculovirus A
Source:University of Iowa