1. Department of Biochemistry and Pharmacy, Åbo Akademi University, PO Box 66, FIN-20521 Turku, Finland
2. Institute of Poliomyelitis and Viral Encephalitides RAMS, Moscow 142782, Russia
3. Department of Virology, University of Turku, Kiinamyllynkatu 13, FIN-20520 Turku, Finland