Serum and CSF measles antibody levels increase over time in patients with multiple sclerosis or clinically isolated syndrome

In general, measles virus (MV) immunoglobulin G (IgG) antibody titres decline over time. However, we found that serum and CSF MV antibody titres increased with age (slope = 0.038, p < 0.001 and slope = 0.022, p = 0.008), respectively, and disease duration (slope = 0.031, p = 0.002 and slope = 0.032, p = 0.005), respectively, in patients with multiple sclerosis (MS) or clinically isolated syndrome (CIS). The age dependency of serum antibody levels differed between patients and controls (slope = 0.038 versus − 0.004, p < 0.001). The increasing MV antibody titres over time in MS/CIS patients support a general nonspecific stimulation of B cells and plasma cells that is not confined only to the CNS/CSF compartment.