[1] CLB Sanquin, Dept Clin Viroimmunol, NL-1066 CX Amsterdam, Netherlands
[2] Univ Amsterdam, Acad Med Ctr, Expt & Clin Immunol Lab, NL-1105 AZ Amsterdam, Netherlands
[3] Katholieke Univ Leuven, Rega Inst, Lab Virol & Chemotherapy, B-3000 Louvain, Belgium