Researchers at the University of Iowa (UI) have reported successful gene therapy delivery in mice using a new type of vector. Vectors, which are often viruses, are a key component of this process because they act as vehicles that deliver the therapy to cells. The particular vector used in this study was a combination of viruses. This hybrid vector combined a baculovirus, which infects insects such as butterflies and moths, with a modified lentivirus called feline immunodeficiency virus, which causes leukemia in cats but not in humans.
The vector delivered the gene therapy to liver cells called hepatocytes. The liver was targeted because it is able to manufacture factor VIII. Paul McCray, MD, is UI professor of pediatrics and corresponding author of the study. In explaining the logic behind targeting liver cells, McCray stated, “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.”
Results of the study demonstrated enough of an increase in factor VIII activity to alter disease severity in mice. “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,” said Dr. McCray. Findings were published in the September 1, 2005 issue of the journal Blood.
Joining the study team, among others, was Yubin Kang, MD, a UI resident in internal medicine. Dr. Kang received a Career Development Award in bleeding disorders research from the National Hemophilia Foundation (NHF) in 2002-2003 and 2003-2004 for a study entitled, “Non-primate Lentiviral Vector-Based Gene Therapy for Hemophilia A.” A description of this and other previous career development awards can be accessed on the NHF Web here.
Source: University of Iowa News Release dated August 22, 2005