1. Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, USA
2. Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, USA
3. Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, USA
4. Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, USA