1. Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892.
2. Laboratory of Oral Medicine, National Institute of Dental Research, NIH, Bethesda, MD.
3. Laboratory of Molecular Biology, NIAID, and the Howard Hughes Medical Institute, NIH, Bethesda, MD.
4. Immunology Branch, National Cancer Institute (NCI), NIH, Bethesda, MD.
5. Laboratory of Experimental Neuropathology, National Institute of Neurological and Communicative Disorders and Stroke, NIH, Bethesda, MD.
6. Laboratory of Pathology, NCI, NIH, Bethesda, MD.
7. Department of Pathobiology, University of Connecticut, Storrs, CT 06268.