1. Ruhr-Universität Bochum, Abteilung für Molekulare und Medizinische Virologie, 44780 Bochum, Germany
2. Clinical Gene Therapy Branch, National Human Genome Research Institute, National Institutes of Health, Bldg. 10, Rm. 10C103, Bethesda, MD and Metabolism Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bldg. 10, Rm. 4N115, Bethesda, MD