Contactin-1 and contactin-2 in cerebrospinal fluid as potential biomarkers for axonal domain dysfunction in multiple sclerosis

Background: Contactin-1 and contactin-2 are important for the maintenance of axonal integrity. Objective: To investigate the cerebrospinal fluid levels of contactin-1 and contactin-2 in multiple sclerosis patients and controls, and their potential use as prognostic markers for neurodegeneration. Methods: Cerebrospinal fluid contactin-1 and contactin-2 were measured in relapsing–remitting multiple sclerosis (n = 41), secondary progressive multiple sclerosis (n = 26) and primary progressive multiple sclerosis patients (n = 13) and controls (n = 18), and in a second cohort with clinically isolated syndrome patients (n = 88, median clinical follow-up period of 2.3 years) and controls (n = 20). Correlations/linear regressions were analysed with other baseline cerebrospinal fluid axonal damage markers and cross-sectional/longitudinal magnetic resonance imaging features. Results: Contactin-1 and contactin-2 levels were up to 1.4-fold reduced in relapsing–remitting multiple sclerosis (contactin-1: p = 0.01, contactin-2: p = 0.02) and secondary progressive multiple sclerosis (contactin-1: p = 0.05, contactin-2: p = 0.02) compared to controls. In clinically isolated syndrome patients, contactin-1 tended to increase when compared to controls (p = 0.07). Both contactin-1 and contactin-2 correlated with neurofilament light, neurofilament heavy and magnetic resonance imaging metrics differently depending on the disease stage. In clinically isolated syndrome patients, baseline contactin-2 level (β = –0.42, p = 0.04) predicted the longitudinal decline in cortex volume. Conclusion: Cerebrospinal fluid contactin-1 and contactin-2 reveal axonal dysfunction in various stages of multiple sclerosis and their inclusion to the biomarker panel may provide better insight into the extent of axonal damage/dysfunction.