The chemotactic cytokines in the cerebrospinal fluid of patients with neuroborreliosis

Abstract

Background: The outcome of neuroborreliosis (NB) is variable and may partially depend on host-related immune factors. In NB, the cerebrospinal fluid (CSF) contains a large population of T lymphocytes, but the mechanisms and consequences of their recruitment have not been fully elucidated. We have studied expression of T lymphocyte chemoattractant cytokines in association with CSF cytometric parameters and clinical data in NB patients.

Methods: The blood and CSF of 17 patients with NB and blood of 12 patients with erythema migrans (EM) were obtained before the antibiotic administration, and in fraction of NB patients during and/or after antibiotic treatment. The control samples came from blood donors (blood) and patients in whom neuroinfection was excluded by a lumbar puncture (CSF). Concentrations of IL-16, CXCL9, CXCL10, CXCL11, CCL2 and CCL5 in serum and CSF were measured with commercial ELISA. Data were analyzed with non-parametric tests, p < 0.05 considered significant.

Results: The serum concentrations of IL-16, CXCL9, CXCL10 and CCL5 were increased, higher in NB than in EM. In CSF all the cytokines were upregulated, CXCL10, CXCL9 and IL-16 over ten-fold. The CSF concentration index favored the intrathecal synthesis of all the cytokines except CCL5, for which it could not be reliably estimated. CCL2, CXCL10 and CXCL9 created concentration gradients towards CSF. The intrathecal expression of IL-16, CCL5 and CXCL9 correlated with CSF lymphocyte counts, of IL-16, CXCL9 and CXCL10 - with a blood-brain barrier disruption, and of CXCL9 and CXCL10 with intrathecal specific IgG synthesis. The expression of CCL2, CXCL10 and CXCL11 peaked early after NB onset and decreased naturally afterwards. High initial CSF CXCL9, CXCL10 and CXCL11 levels associated with a persistent CSF pleocytosis and BBB disruption after treatment, but no cytokine was predictive of clinical outcome. In follow up (post-treatment) examinations, CSF CXCL10 and CCL5 associated positively and CCL2 negatively with a protracted lymphocytic pleocytosis.

Conclusions: Several cytokines chemotactic for T lymphocytes are upregulated intrathecally in NB, with different dynamics and relation to other inflammatory parameters, suggesting their distinct pathogenetic roles. CXCL10 and CXCL9 are vividly upregulated and seem deeply involved in the pathogenesis of the intrathecal inflammation. IL-16 and CCL5 may directly drive T lymphocyte migration from periphery, but their ability to create an adequate chemotactic gradient remains to be confirmed. A delayed normalization of pleocytosis is accompanied by higher intrathecal expression of Th1-related and lower of Th2-related chemokines, in agreement with the protective role of Th1 to Th2 transition in the course of NB.

Keywords: Chemokines; Chemotaxis; Neuroborreliosis; Neuroinflammation; T lymphocytes.