1. Laboratory Branch, Division of HIV/AIDS Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia 30333.
2. Emory University School of Medicine, Division of Infectious Diseases, Emory Center for AIDS Research, Atlanta, Georgia 30322.
3. Epidemiology Branch, Division of HIV/AIDS Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia 30333.
4. Department of Biochemistry, University of Pennsylvania, School of Dental Medicine, Philadelphia, Pennsylvania 19104.
5. Present address: University of Pittsburgh, Magle-Women’s Research Institute, Pittsburgh, Pennsylvania 152130.