Detection and characterization of autoantibodies directed against neurofilament proteins in human African trypanosomiasis

In serum and in cerebrospinal fluid (CSF) from patients with human African trypanosomiasis (HAT) with central nervous system involvement, we detected autoantibodies directed to some proteins from these tissues. The characterization of antigenic proteins by Western blotting showed that the antibodies recognized the 200-kD and 160-kD proteins of neurofilament (NF). Serum anti-NF antibodies were more frequent in HAT patients than in control subjects (86% versus 24%; P < 10-9) and they belonged predominantly to the IgM class (anti-NF IgM = 86% versus anti-NF IgG = 4%; P < 10-9) in the patients with stage II (central nervous system involvement) HAT. The CSF antibodies to NF were IgM in 88% (22 of 25) of the cases and IgG in 32% (8 of 25) of the cases. Epitopes shared by NF and trypanosomes were detected by indirect immunofluorescence and this was confirmed by the disappearance of anti-NF reactivity after adsorption with trypanosome antigens (Trypanosoma brucei brucei or T. b. gambiense). Anti-NF antibodies were undetectable in the CSF from stage I HAT patients.