1. Department of Microbiology & Molecular Genetics, College of Osteopathic Medicine, Michigan State University, East Lansing, MI 48824, USA
2. Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 22710, USA
3. Duke Human Vaccine Institute, Duke University Medical Center, Durham, NC 27710, USA
4. Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA 01650, USA
5. Department of Immunology, Duke University Medical Center, Durham, NC 22710, USA