1. Centre for Gene Therapeutics, Department of Pathology and Molecular Medicine, McMaster University Health Sciences Centre, Hamilton, Ontario, Canada L8N 3Z5
2. Institute of Medical Microbiology, Immunology and Hygiene, Technical University of Munich, Munich, Germany
3. Department of Veterinary Pathobiology, University of Missouri, Columbia, Missouri 65211;
4. Department of Laboratory Medicine, University of Washington, and Program in Infectious Diseases, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109