1. Center for Vaccine Development and Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland 212011;
2. Department of Microbiology and Immunology, The University of Melbourne, Parkville, Victoria 3052, Australia2;
3. Department of Biology, Reed College, Portland, Oregon 972023; and
4. Division of Bacterial Infection, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo 108-8639, Japan4