1. California Primate Research Center, University of California, Davis 95616
2. Frederick Cancer Research Facility, Frederick, Maryland 21701
3. Infectious Diseases Branch, National Institute of Neurological and Communicative Disorders and Stroke, Bethesda, Maryland 20205
4. Cancer Research Institute, University of California Medical Center, San Francisco 94143
5. Department of Pathology, School of Medicine, University of California, Davis 95616