1. Institute of Virology and Immunology, Bern, Switzerland
2. Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
3. Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA
4. Department of Veterinary Pathobiology, Oklahoma State University, Stillwater, Oklahoma, USA
5. Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark