1. Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Martinistrasse 52, 20251 Hamburg, Germany
2. Department of Virology, Bernhard Nocht Institute for Tropical Medicine, Bernhard Nocht Strasse 74, 20359 Hamburg, Germany
3. Department of Microbiology & Immunology, University of Texas Medical Branch, Galveston, TX 77555, USA
4. Galveston National Laboratory, University of Texas Medical Branch, Galveston, TX 77555, USA