Free Immunoglobulin Light Chains in Patients with Tick-Borne Encephalitis: Before and after Treatment

Background: Tick-borne encephalitis (TBE) is inflammation of the central nervous system (CNS) caused by a viral infection which may be associated with increased synthesis of immunoglobulins. It can lead to inter alia, breakdown of the blood-brain barrier (BBB), or even death and, unfortunately, treatment is only symptomatic. Therefore, the aim of the present study was assessment of the concentrations of free light chains (FLC) kappa (kappa) and lambda (lambda in the cerebrospinal fluid (CSF) and serum of patients with TBE. Methods: A total of 58 cerebrospinal fluid and serum sample pairs were analyzed. Samples were collected from patients with TBE before and after treatment. FLC were measured using the turbidimetric method. The values of kappa IgG-index, lambda IgG-index, kappa FLC-index and lambda FLC-index were calculated using relevant formulas. Results: Pre-treatment serum lambda FLC concentrations were higher in comparison to post-treatment levels. Moreover, it was observed that CSF lambda FLC, TBEV IgM, TBEV IgG, and serum TBEV IgG, as well as the values of lambda FLC-index, kappa FLC-index, and lambda IgG-index were elevated after treatment. In the total study group, the concentrations of CSF kappa FLC and lambda FLC, and values of four indexes: kappa FLC-index, lambda FLC-index, kappa IgG-index, and lambda IgG-index correlated with each other and with CSF TBEV IgM and IgG antibodies. The CSF level of TBEV IgG was also associated with serum IgG TBEV and CSF IgM TBEV antibodies. Additionally, serum kappa FLC correlated with serum and CSF lambda FLC. Conclusion: This is the first study that demonstrates statistically significant differences in serum and CSF lambda FLC, as well as in the calculated values of three algorithms: lambda IgG-index, kappa FLC-index, and lambda IgG-index prior to and following treatment of TBE. Our findings may indicate that these differences reflect the intrathecal synthesis of immunoglobulins and increased permeability of BBB in patients with TBE. Moreover, it could provide the basis for developing new therapeutic strategies.