1. Max von Pettenkofer Institute, Department of Virology,1 and
2. Chester Beatty Laboratories, Institute of Cancer Research, London SW3 6JB, United Kingdom2
3. Leibniz Research Laboratories for Biotechnology and Artificial Organs, Hannover Medical School, 30659 Hannover,3 Germany, and
4. Department of Medical Genetics,4 Ludwig Maximilian University, Munich, and