[1] Georg Speyer Haus, Paul Ehrlich Str 42-44, D-60596 Frankfurt, Germany
[2] Univ Hamburg, Heinrich Pette Inst Expt Virol & Immunol, D-20251 Hamburg, Germany
[3] Univ Hamburg, Krankenhaus Eppendorf, Zentrum Knochenmarktransplantat, D-20251 Hamburg, Germany
[4] Inst Appl Microbiol, A-1190 Vienna, Austria