1. AIDS Vaccine Evaluation Unit, Vanderbilt University, Nashville, Tennessee 37232
2. Department of Medicine, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
3. AIDS Vaccine Evaluation Unit, University of Alabama at Birmingham, Birmingham, Alabama 35284
4. Duke University Center for AIDS Research, Durham, North Carolina 27710
5. Division of Retrovirology, Walter Reed Army Institute of Research and Henry M. Jackson Foundation, Rockville, Maryland 20850
6. Cattedra di Immunologia, Universita degli Studi di Milano, Milan, Italy
7. Mucosal Immunology Laboratory, University of Alabama at Birmingham, Birmingham, Alabama 02115