[1] Univ Heidelberg, Klinikum Mannheim, Med Klin 3, Fak Klin Med Mannheim, D-68305 Mannheim, Germany
[2] Univ Munster, Kinderklin Paediat Haematol & Onkol, D-4400 Munster, Germany
[3] Univ Dusseldorf, Klin Haematol Onkol & Klin Immunol, D-4000 Dusseldorf, Germany
[4] Klinikum Stadt Ludwigshafen, Med Klin A, D-6700 Ludwigshafen, Germany
[5] GSF, Natl Res Ctr Environm & Hlth, Inst Mol Virol, Neuherberg, Germany