1. Department of Clinical Viro-lmmunology, Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, and Laboratory for Experimental and Clinical Immunology of the University of Amsterdam, Plesmanlaan 125, 1066 CX Amsterdam, The Netherlands.
2. Department of Molecular Pathology, TNO Institute of Applied Radiobiology and Immunology, Rijswijk, The Netherlands.
3. Netherlands Institute for Brain Research, Amsterdam, The Netherlands.
4. Department of Infectious Diseases, Municipal Health Service, Amsterdam, The Netherlands.