1. Department of Molecular Microbiology and Immunology, Brown University, Providence, RI 02912, USA.
2. Graduate Program in Pathobiology, Brown University, Providence, RI 02912, USA.
3. Graduate Program in Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, RI 02912, USA.
4. Department of Biochemistry, Case Western Reserve University Medical School, Cleveland, Ohio 44106, USA.