Lyme borreliosis, the most common tick-borne disease in the northern hemisphere, is caused by Borrelia burgdorferi sensu lato spirochetes (later Borrelia). They can infect humans through bites of infected Ixodes ticks. If the infection is not treated at the early local stage of the disease, spirochetes can disseminate via the blood vasculature into distant tissues of the human body and cause symptoms in the joints, the heart, and the nervous system. Infection of the central nervous system is called Lyme neuroborreliosis. Lyme neuroborreliosis is diagnosed based on neurological symptoms, pleocytosis, and intrathecal production of Borrelia-specific antibodies. Recently, chemokine CXCL13 has been introduced as a new biomarker for diagnostics of Lyme neuroborreliosis.

The first aim of this study was to characterize the dissemination of Borrelia by in vitro adhesion studies conducted under shear stress and by imaging the infection in vivo in mice. The second aim was to evaluate the use of cytokines as biomarkers for Lyme neuroborreliosis.

The studies revealed that decorin binding proteins of Borrelia act in a flow-tolerant manner mediating adherence into vascular endothelium under the mechanical force caused by the liquid flow. In addition to decorin, decorin binding proteins were shown to bind biglycan, a proteoglycan which is expressed on endothelium more abundantly than decorin. Moreover, dissemination of Borrelia can be imaged in vivo in mice using positron-emission tomography. The studies also showed that CXCL13 is the most specific cytokine biomarker for Lyme neuroborreliosis and the concentration of CXCL13 can reliably be measured of Lyme neuroborreliosis patients’ cerebrospinal fluid samples with a point-of-care test. Overall, the studies gave new information on the pathogenesis of Lyme borreliosis and helped to improve the disease diagnostics.