1. Department of Virology and Molecular Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 381011;
2. M. P. Chumakov Institute of Poliomyelitis and Viral Encephalitides, Russian Academy of Medical Sciences, 142782 Moscow,2 and
3. Dipartimento di Virologia, Istituto Superiore di Sanita, 00161 Rome, Italy3;
4. Shemyakin Institute of Bioorganic Chemistry, Miklukho-Maklaya, 117871 Moscow,4 Russia;
5. Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin—Madison, Madison, Wisconsin 537065; and
6. Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo 108-8639, Japan6