1. Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892
2. Bioqual, Rockville, Maryland 20850
3. Science Applications International Corporation—Frederick, Inc., Frederick, Maryland 21702
4. Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892
5. Department of Virology, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima-shi, Tokushima 770-8503, Japan