1. Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA.
2. Rakai Health Sciences Program, Kalisizo, Uganda.
3. Department of Pathology and School of Medicine, Johns Hopkins University, Baltimore, Maryland, USA.
4. Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, Maryland, USA.
5. Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, US National Institutes of Health, Bethesda, Maryland, USA.