1. Department of Pediatric Hematology/Oncology, University Children's Hospital, Tübingen, Germany;
2. Department of Hematology/Oncology, Eberhard-Karls University, Tübingen, Germany;
3. Department of Hematology/Oncology, University Hospital Würzburg, Würzburg, Germany;
4. Clinic of Pediatric Oncology, Hematology and Immunology, Heinrich-Heine-University, Düsseldorf, Germany;
5. Hannover Medical School, Clinic for Hematology, Hemostasis, Oncology and Stem Cell Transplantation, Hannover, Germany;
6. Hematologie Clinique, Universite de Nantes, Nantes, France;
7. Department of Bone Marrow Transplantation, Hadassah University Hospital, Jerusalem, Israel;
8. Russian Children's Hospital, Moscow, Russia; and
9. Institute of Virology, Eberhard-Karls University, Tübingen, Germany