1Division of Gene Therapy and Hepatology, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain2Division of Gene Therapy, University of Ulm, Ulm, Germany3Department of Cell and Immunology, Faculty of Medicine, Vrije Universiteit Medical Center, Amsterdam, The Netherlands4Unité de Biologie des Régulations Immunitaires, INSERM E 352, Institut Pasteur, Paris, France5Division of Hematology, Department of Medicine, University of Minnesota, Minneapolis, MN