1. Departments of Epidemiology and Molecular Microbiology and Immunology, Johns Hopkins University, Baltimore, Maryland 21205
2. Division of Cancer Epidemiology and Genetics and Division of Cancer Prevention
3. Departments of Molecular Genetics and Microbiology and Obstetrics and Gynecology, University of New Mexico Health Sciences Center, School of Medicine, University of New Mexico, Albuquerque, New Mexico 87131
4. National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892