1. Department of Virology, National Bacteriological Laboratory, Stockholm, Sweden
2. Department of Neurosurgery, Karolinska Institute, Stockholm, Sweden
3. Department of Clinical Immunology/Centre for Biotechnology, Huddinge Hospital and Department of Immunology, Arrhenius Laboratories of Natural Science, University of Stockholm, Sweden
4. Department of Virology, Karolinska Institute, Stockholm, Sweden