1. Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63130, USA.
2. Swedish Institute for Infectious Disease Control and Center for Infectious Medicine, Department of Medicine, Karolinska Institutet, 141 86 Stockholm, Sweden.
3. Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA.
4. Unité Mixte de Recherche (Joint Research Unit) CNRS 5539, University Montpellier 2, Place Eugene Bataillon, 34095 Montpellier Cedex 5, France.
5. Department of Veterinary Molecular Biology, Montana State University, Bozeman, MT 59717, USA.