1. Department of Epizootiology, Faculty of Veterinary Medicine; Hokkaido University; Sapporo, Hokkaido 060
2. Laboratory of Cell Biology, Basic Research Laboratories; Toray Industries Inc.; Kamakura, Kanagawa 248
3. Laboratory of Molecular Oncology; The Institute of Physical and Chemical Research; Wako, Saitama 351-01
4. Department of Veterinary Microbiology; College of Dairy Agriculture; Ebetsu, Hokkaido 069