1. Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, WI 53226
2. Kyoto University, Kyoto, Japan
3. Laboratory of Cytokines, Department of Viral Disease and Vaccine Control, National Institutes of Infectious Diseases, Tokyo, Japan
4. Schering-Plough K.K., Shiga Research Laboratories, Shiga, Japan
5. Amersham Bucks, HP6 6EY, U.K