Researchers at the University of Pennsylvania Medical Center recently studied immune responses with gene therapy in hemophilia B mice. The mice received multiple doses of an adeno-associated viral (AAV) vector to deliver the therapy. Vectors are a key component of gene therapy because they act as vehicles to deliver the corrected gene to cells. Although the gene transfer did elicit factor IX (FIX) production in the mice, it often also triggered an immune response. This inhibitory response was manifested by the production of antibodies that attacked the FIX, making the protein ineffective. “Formation of inhibitory antibodies to hFIX was observed over a wide range of vector doses, with increased doses causing stronger immune responses,” said Li-xin Wang, PhD of the University of Pennsylvania.
“The risk of an immune response to the coagulation FIX transgene product is a concern in gene therapy for the X-linked bleeding disorder hemophilia B,” added Dr. Wang. The immune response discovered in this gene therapy study is of potential importance when considering that inhibitor development in humans is often a difficult and costly complication to correct. Approximately 15% to 30% of people with severe hemophilia A and 1% to 4% of those with severe hemophilia B develop inhibitors. The study was published in the October, 2005 issue of the journal Gene Therapy.
Source: Gene Therapy Weekly, November 10, 2005