CXCL9 concentrations in cerebrospinal fluid and serum of patients with tick-borne encephalitis

Introduction: The aim of our current study was to evaluate cerebrospinal fluid (CSF) and serum CXCL9 concentrations and diagnostic usefulness of this molecule in tick-borne encephalitis (TBE). The study included TBE patients in the acute phase (TBE I) and after 2 weeks of follow-up (TBE II). The control group consisted of patients investigated for suspected central nervous system (CNS) infection, but with normal CSF findings. Material and methods: Concentrations of CXCL9 were measured using enzyme-linked immunosorbent assay (ELISA). Results: Cerebrospinal fluid and serum concentrations of CXCL9 in patients with TBE were significantly higher than in controls (p < 0.001). This alteration was also observed in the case of the CXCL9 index (I-CXCL9; CSF CXCL9 concentration divided by serum CXCL9 concentration) (p < 0.001); moreover, I-CXCL9 significantly decreased after 2 weeks (p < 0.001). This is the first study to evaluate the CSF and serum levels of CXCL9 in subjects with TBE. Conclusions: CXCL9 is a ligand for CXCR3, which was found on all Th-1 memory lymphocytes present in the peripheral blood; therefore the elevated concentrations of CXCL9 in TBE patients as compared to the controls might indicate that this chemokine perhaps takes part in the trafficking of Th-1 cells into the CNS. The results presented here support the hypothesis that CXCL9 may play a role in TBE. However, further studies are required to determine whether this protein might be used as a potential tool for the diagnosis and monitoring of inflammation in TBE.