1. Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
2. Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
3. Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
4. Division of Infectious Diseases, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
5. AIDS and Cancer Virus Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA
6. Bioqual, Inc., Rockville, Maryland, USA
7. Duke Human Vaccine Institute, Duke University School of Medicine, Durham, North Carolina, USA
8. Department of Medicine, Duke University School of Medicine, Durham, North Carolina, USA