Author information:
(1)Institute for Molecular Infection Biology, University of Würzburg, 
Josef-Schneider-Straße 2, 97080 Würzburg, Germany.
(2)Institute for Molecular Infection Biology, University of Würzburg, 
Josef-Schneider-Straße 2, 97080 Würzburg, Germany. Electronic address: 
joerg.vogel@uni-wuerzburg.de.