1. Section of Serology, Institute of Immunological Science, Hokkaido University, Kita-ku, Sapporo 060-0815,1
2. Department of Virology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871,2
3. Department of Neuropsychiatry, Kagawa Medical College, Kagawa 761-0007,3
4. Department of Pathology, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu 069-8501,4 and
5. Department of Pathology, National Institute of Infectious Diseases, Shinjuku-ku, Tokyo 162-8640,5 Japan, and
6. Department of Neuropharmacology, The Scripps Research Institute, La Jolla, California 920376