Intrathecal immune response in neuroborreliosis: importance of cross-reactive antibodies.

The intrathecal IgG response to Borrelia burgdorferi was evaluated in 35 patients with neuroborreliosis (NB). Samples were tested with and without preabsorption with Treponema phagedenis. Specific antibody concentrations in the CSF and serum were determined by ELISA. The antibody index (AIBb = QBb/QIgG) was calculated from the ratio between the CSF/serum quotients for specific antibodies (QBb) and total IgG (QIgG). Intrathecal synthesis of B. burgdorferi antibodies was demonstrated in 31 samples before and in 24 samples after preabsorption with T. phagedenis. The clonal distribution of intrathecally produced IgG antibodies was determined by isoelectric focusing combined with affinity blotting. B. burgdorferi-specific oligoclonal IgG bands occurring predominantly in the CSF were demonstrated in 32/35 patients. In 29/32 samples, the major proportion of these bands also reacted with T. phagedenis. Preabsorption of samples with T. phagedenis removed a considerable share of bands reacting with B. burgdorferi. In patients with neurosyphilis, intrathecal synthesis of antibodies with specificity for B. burgdorferi was demonstrated in 7/10 samples before, and in no sample, after preabsorption of cross-reactive antibodies. Due to the lower sensitivity in determining the AIBb (-20%), preabsorption of cross-reactive antibodies cannot be generally recommended. In all patients with suspected neuroborreliosis, but uncommon neurological symptoms and missing anamnestic data concerning a tick bite or erythema migrans, neurosyphilis should be excluded by a negative TPHA test.