About the Authors
Institute of Microbiology, ETH Zürich, Zürich, Switzerland
Institute for Virology, Heinrich-Heine-University Düsseldorf , Düsseldorf, Germany
The authors have declared that no competing interests exist.
Conceived and designed the experiments: SMW HH AO. Performed the experiments: SMW SM NT AZ. Analyzed the data: SMW SM NT AO. Contributed reagents/materials/analysis tools: AZ HH. Wrote the paper: SMW AO.