1. Department
of Chemical Engineering, Stanford University, Palo Alto, California 94305, United States
2. Department of Medicine, Division of Gastroenterology and Hepatology, Stanford University School of Medicine, Palo Alto, California 94305, United States
3. Department of Microbiology and Immunology, Stanford University School of Medicine, Palo Alto, California 94305, United States
4. Virology Discovery, Hoffmann-La Roche Inc., Nutley, New Jersey 07110, United States
5. Veterans Administration Medical Center, Palo Alto, California 94304, United States