[1] Univ Bonn, Inst Mol Med & Expt Immunol, D-53105 Bonn, Germany
[2] Univ Heidelberg, Abt Parasitol, Inst Hyg, D-69120 Heidelberg, Germany
[3] Zentrum Mol Biol Heidelberg, D-69120 Heidelberg, Germany
[4] Vrije Univ Amsterdam, Med Ctr Amsterdam, Dept Mol Cell Biol, NL-1081 Amsterdam, Netherlands