1. Department of Microbiology, Immunology, and Molecular Genetics, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
2. Department of Radiology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
3. Department of Biology, Indiana University, Bloomington, Indiana, USA
4. Department of Molecular Biology & Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
5. Howard Hughes Medical Institute, Chevy Chase, Maryland, USA