1. Institute for Virology and Immunobiology, University of Würzburg, 97078 Würzburg, Germany
2. Institute for Virology and Immunobiology, University of Würzburg, 97078 Würzburg, Germany; Infectious Disease Unit, Medical Policlinic, University of Würzburg, 97080 Würzburg, Germany
3. SmithKline Beecham, Rixensart, Belgium
4. Infectious Disease Unit, Medical Policlinic, University of Würzburg, 97080 Würzburg, Germany