1 Department of Preventive Medicine and AIDS Research and Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, and First Department of Internal Medicine, Yokohama City University School of Medicine, Yokohama, Japan; Gladstone Institute of Virology and Immunology, San Francisco, California; and Immunopathology Section, Laboratory of Immunobiology, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, Maryland