1. Department of Biochemistry, University of Lausanne, 1066 Epalinges, Switzerland.
2. Swiss Institute of Bioinformatics, University of Lausanne, 1015 Dorigny, Switzerland.
3. Department of Molecular Microbiology, Washington University, School of Medicine, St Louis, MO 63110, USA.
4. World Health Organization–Immunology Research and Training Centre, 1066 Epalinges, Switzerland.