Adeno-Associated Virus Vectors for Stem Cell Gene Therapy
My group has been focusing on evaluating genetic modification of hematopoietic stem cells using rAAV vectors for ultimate treatment in HIV infection, cancer, cardiovascular, and genetic diseases. We have recently shown that non-dividing quiescent CD34+CD38- stem cells from bone marrow and cord blood can be modified with AAV vectors and that gene transfer in these cells results in stable (integrated) genetic modification. Utilizing an in vivo model of human hematopoietic engraftment in immune-deficient mice, we have shown that rAAV-transduced CD34+38- cells from cord blood engraft and give rise to multiple lineages of blood cells. Interestingly, rAAV-transduced CD34+ stem cells are also identifiable in the marrow up to at least six months post-transplant.
Perhaps our most exciting finding is that in serial transplants of marrow from immune-deficient mice transplanted with rAAV-transduced human cord blood stem cells, we found rAAV-transduced CD34 cells in secondary recipients. This assay has been the defining in vivo assay for hematopoietic stem cells. Thus we now conclude that rAAV vectors are capable of transducing true human hematopoietic stem cells, an objective in the field that has been elusive for a long time. The ability to gene modify stem cells with a non-pathogenic vector has significant implications for the development of future therapies for a number of intractable diseases. Leah Tager, Helicia Paz, Sai Srinivas, Christie Wong, and Cindy Wei have been involved in these studies.
In other studies, we are investigating the use of rAAV vectors encoding ApoA1 mutants for gene therapy for atherosclerosis. Direct intra-muscular injections of rAAV as well as bone marrow transplants with rAAV-transduced marrow cells are being evaluated for reduction of atherosclerotic plaques in a mouse model.