1. Infectious Diseases Division, Department of Internal Medicine, University of Texas Medical Branch, Galveston, Texas
2. Department of Medicine, Division of Gastroenterology, University of California at San Diego, La Jolla, California
3. Cell Biology Laboratory, United States Army Medical Research Detachment, Walter Reed Army Institute of Research, Brooks City-Base, Texas
4. Infectious Disease Section, Department of Medicine
5. Department of Immunology, Baylor College of Medicine, Houston, Texas