PATHOGENESIS OF LYME NEUROBORRELIOSIS IN THE RHESUS MONKEY: STUDIES IN VITRO

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Background: Many neurodegenerative disorders including Alzheimer's disease, cerebral ischemia and the AIDS-dementia complex are thought to result from inflammation in the central nervous system (CNS). Lyme neuroborreliosis is likewise considered to be a consequence of inflammation elicited in the CNS. The bacterial spirochete Borrelia burgdorferi (Bb) causes Lyme disease and is known to induce the production of inflammatory mediators in glial cells of the CNS. We hypothesized that neuronal cells, by virtue of proximity, may become impaired in this environment, eventually leading to the neurocognitive symptoms seen in neuroborreliosis. Methods: In order to determine the neuronal and glial cell responses to Borrelia burgdorferi infection we have designed an in-vitro model where Bb is co-cultivated with cells from primary rhesus cortex either alone or in combination with SH-SY5Y neuroblastoma cells. Results: Using sandwich ELISA we observed robust expression and release of the inflammatory cytokines / chemokines IL-6 and 8, and induction of TNF-¿, in the cortex cells stimulated with Bb. When these same stimulations of primary glial cells with Bb are combined with the neuronal cell lines SH-SY5Y or HCN-1, increases in cellular apoptosis consistently occur. The neuronal cell lines independently stimulated with Borrelia express comparatively negligible amounts of inflammatory cytokine and they are resistant to apoptosis in this environment. In contrast, when neurons are co-cultivated either with mixed glial cells or with pure microglia, the neurons die by apoptosis, as assessed via the TUNEL assay: These are findings to suggest that 1) B. burgdorferi does not damage neurons per se; 2) microglia, either alone or in concert with other glial cell types, are able to generate a deleterious effect on neurons in the presence of B. burgdorferi.