1. Department of Biosystems Science and Engineering, ETH Zurich, 4058 Basel, Switzerland;
2. Life Science Zurich Graduate School, ETH Zurich and University of Zurich, 8006 Zurich, Switzerland
3. Department of Pathology and Immunology, University of Geneva, 1205 Geneva, Switzerland
4. Department of Biology, Institute of Microbiology and Immunology, ETH Zurich, 8093 Zurich, Switzerland