1. Laboratory of Gastrointestinal and Liver Studies, Digestive Diseases Division, Department of Medicine; Uniformed Services University of the Health Sciences; Bethesda Md
2. Laboratory of Gastrointestinal and Liver Studies, Digestive Diseases Division, Department of Medicine; Uniformed Services University of the Health Sciences, Bethesda, and Bioqual Inc.,; Rockville Md
3. Departments of Molecular Microbiology and of Genetics; Washington University Medical School; St. Louis Mo
4. Departments of Medicine and Microbiology; New York University School of Medicine, and New York Harbor VA Medical Center; New York NY