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Abstract

Despite significant advances in the understanding of the pathogenesis of viral meningitis, infection with non-polio enteroviruses (NPEV) has an increasing disease burden worldwide. This dissertation hopes to contribute to further deepening the understanding of the disease for a successful containment of the disease in the future. Viral meningitis can be caused by infection with Echovirus (E) 30 (E-30) of the central nervous system (CNS) at the level of the blood-cerebrospinal fluid barrier (BCSFB). This infection causes neuroinflammation resulting in immune cell migration. Clinical analysis suggests that in the cerebrospinal fluid a pleocytosis of predominantly polymorphonuclear granulocytes (PMN) occurs in the early phase of infection, followed by a monocuclear cell population. Within the scope of this thesis we analysed the sequential transmigration of PMN and CD3+ T-lymphocytes across an E-30 Bastianni- infected human BCSFB in vitro. The results show that migration of PMN through human choroid plexus papilloma (HIBCPP) cells was significantly increased when CD3+ T-lymphocytes were present. In contrast, PMN were not able to promote T-lymphocyte migration. Chemokine expression was affected by E-30 infection with an upregulation of CXCL 3 and CXCL 11. The secretion of these and other chemokines was mainly directed towards the basolateral HIBCPP cell side, except for IL-7 where apical secretion was dominant. In the next step we were utilizing three clinical outbreak strains and the prototypic E-30 Bastianni strain and we were able to show strain dependent effect on the epithelial cell barrier function and morphology. The strains 13-759 and 14-397 did not cause significant effects on the barrier integrity of the HIBCPP cells. E-30 Bastianni and outbreak strain 13-311 caused significant decrease in the transepithelial electrical resistance of the epithelial cell barrier. These two strains were the only variants causing visible alteration of the tight junction proteins ZO1 and Occludin and the adherence junction protein E-cadherin. Despite these disruptive effects on the morphology of the epithelial cell barrier, migration of PMN and CD3+ T lymphocytes occurred both via the trans- and paracellular route. Analysis applying electron microscopy and immunofluorescence detected both cell types during and just following their migration across the epithelial cell barrier moving both between and through the HIBCPP cells. Further analysis of the genetic composition identified differences between the strains, but these could not be linked to the differences observed during the infection experiments. Overall, we showed enhanced PMN migration across the infected epithelial cell layer in the presence of CD3+ T-lymphocytes and an intriguing chemokine release pattern. Further, we were able to show E-30 strain specific effects on human epithelial cell barrier integrity. The strains caused particular morphological changes to the junctional proteins, however, migration of leukocytes occurred both trans and paracellularly. We were able to identify E-30 strain-specific effects on the epithelial cell barrier and contribute to the understanding of immune cell migration in viral meningitis.