1. Abteilung Virologie, Institut für Medizinische Mikrobiologie und Hygiene, Universität Freiburg, D-79008 Freiburg, Germany
2. Department of Medical Microbiology and Immunology, University of Aarhus, DK-8000 Aarhus, Denmark
3. Department of Molecular Biology, University of Aarhus, DK-8000 Aarhus, Denmark