1. Laboratory of Immunology, Department of Pathology, Universidade Federal de Uberlandia, Uberlandia 38400-902,1
2. Department of Biochemistry and Immunology, Universidade Federal de Minas Gerais, Belo Horizonte 31270-010,2 and
3. Centro de Pesquisas Rene Rachou, FIOCRUZ, Belo Horizonte 30190-002,3Minas Gerais, Brazil, and
4. Department of Medicine (Neurology) and Microbiology, Dartmouth Medical School, Lebanon, New Hampshire 037564