1. Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294
2. Howard Hughes Medical Institute, University of Alabama at Birmingham, Birmingham, Alabama 35294
3. Department of Zoology, University of Oxford, Oxford OX1 3PB, UK
4. Division of AIDS, STD, and TB Laboratory Research, CDC, Atlanta, Georgia 30333
5. Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294; Howard Hughes Medical Institute, University of Alabama at Birmingham, Birmingham, Alabama 35294; Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
6. Department of Epidemiology and International Health, University of Alabama at Birmingham, Birmingham, Alabama 35294
7. Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294; Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294