1. Department of Microbiology and Molecular Medicine, University of Geneva Medical School, CMU, 1 Rue Michel-Servet, CH-1211 Geneva 4, Switzerland
2. Centre de Recherche du Service de Santé des Armées, 24 Avenue des Maquis du Grésivaudan, F-38702, La Tronche, France
3. Swiss Federal Institute of Technology, School of Life Sciences, CH-1015 Lausanne, Switzerland