1. State Key Laboratory for Infectious Disease Prevention and Control, National Center for AIDS/STD Control and Prevention (NCAIDS), Chinese Center for Disease Control and Prevention (CDC), Beijing, China.
2. Scientific Research Center, Shanghai Public Health Clinical Center, Institutes of Biomedical Sciences, Fudan University, Shanghai, China.
3. Present address: Vaccine Research Center, National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, Maryland.