1. Department of Applied Chemistry and Microbiology, University of Helsinki, P.O. Box 56, FIN-00014 Helsinki, Finland, Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Institutskaya 3, Pushchino, Moscow Region, 142290 Russia, Department of Viral Diseases and Immunology, National Public Health Institute, Mannerheimintie 166, FI-00300 Helsinki, Finland, and Department of Microbiology, Faculty of Science and Informatics, University of Szeged, Kozep fasor 52, H-6726 Szeged,...