Increased Intrathecal High-Avidity Anti-Tau Antibodies in Patients with Multiple Sclerosis

Background: Antibodies against tau protein indicate an interaction between the immune system and the neurocytoskeleton and therefore may reflect axonal injury in multiple sclerosis (MS). Methodology/Principal Findings: The levels and avidities of anti-tau IgG antibodies were measured using ELISA in paired cerebrospinal fluid (CSF) and serum samples obtained from 49 MS patients and 47 controls. Anti-tau antibodies were significantly elevated intrathecally (p < 0.0001) in the MS group. The CSF anti-tau antibody levels were lower in MS patients receiving therapy than those without treatment (p < 0.05). The avidities of anti-tau antibodies were higher in the CSF than in the serum (MS group p < 0.0001; controls p < 0.005). Anti-tau avidities in the CSF were elevated in MS patients in comparison with controls (p < 0.05), but not in serum. Conclusions: MS patients have higher levels of intrathecal anti-tau antibodies. Anti-tau antibodies have different avidities in different compartments with the highest values in the CSF of MS patients.