Borrelia afzelii differential gene expression in the course of tick blood-feeding, and during chronic infection in mice was studied. Temperature effect on B. afzelii gene expression and infectivity was investigated. Infection rates of mice immunized with B. afzelii tick gut antigen at various stages of tick blood-intake were analyzed. This work was funded by the Grant Agency of the Czech Republic, Project No. 17-27393S to Radek Šíma.

Interaction between mouse dendritic cells (DCs) and Borrelia afzelii spichochetes was studied on three different levels: phagocytosis of borrelia by DCs, production of cytokines by borrelia-activated DCs and the ablilty of DCs to activate CD4+ T cells. The effect of Ixodes ricinus saliva on each of these levels was examined. Tick saliva was shown to decrease the number of phagocosing DCs. The ability of borrelia-activated DCs to induce both proliferation and IL-2 production in specific CD4+ T cells was significantly reduced by tick saliva. And surprisingly, we have shown an inhibitory effect of I. ricinus saliva on the production of both Th1 (IL-6 and TNF-{$\alpha$}) and Th2 (IL-10) cytokines. Our data reveal a complex inhibitory effect of tick saliva on DC function.

The topic of this thesis is a logical continuation of the bachelor project. In our previous project, using the method of Borrelia cultivation on solid medium, we succeeded obtaining a monoclonal population of B. garinii from the american isolate in which the presence of more borrelia species was confirmed. By this we confirmed the presence so-called "european" Borrelia species in the southeastern United States (specifically in South Carolina). By multilocus analysis of eight housekeeping genes of american isolate it has been shown that the obtained strain of B. garinii is different from the previously described european and asian strains of this species. The main objective of the proposed project, is the analysis of the pathogenic potential of the isolated clone of B. garinii. Validation of the pathogenic potential of American B. garinii isolate in laboratory mice model could be important for the public health of the southeast american population, as this will confirm the possibility of existence of Lyme disease, caused by this spirochete species, with significantly different clinical signs in this region. For this purpose, the method of direct diagnosis (infecting laboratory animals and transferring of infection from infected animals to the tick and vice versa) was used. Laboratory mice were infected subcutaneously, and the spirochete infection was confirmed in ear tissue by PCR. Uninfected Ixodes ricinus larvae were fed on infected mice. After the confirmation of infection in newly hatched nymphs they were fed on naive mice. The ability of transmitted spirochetes to disseminate into different mice tissues was confirmed by PCR. The presence another so-called "European" species, B. afzelii, was confirmed in original rodent associated American isolate. Another aim of the project was to obtain monoclonal populations B. afzelii from co-infected northamerican sample confirming by this way the transoceanic migration of spirochtes.

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