1. Department of Microbiology, Division of Infectious Diseases, University of Alabama at Birmingham, Birmingham, Alabama 35294-2170.
2. Mucosal Immunology Laboratory for the AIDS Vaccine Evaluation Group, Division of Infectious Diseases, University of Alabama at Birmingham, Birmingham, Alabama 35294-2170.
3. Department of Medicine, Division of Infectious Diseases, University of Alabama at Birmingham, Birmingham, Alabama 35294-2170.