PATHOGENESIS OF LYME NEUROBORRELIOSIS IN THE RHESUS MONKEY: STUDIES EX VIVO

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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. Lyme neuroborreliosis is a disease of the nervous system caused by the spirochete B. burgdorferi; it often leads to cognitive deficits that may be due to impaired neuronal function. The pathogenesis of LNB is unknown. We hypothesized that B. burgdorferi spirochetes induce cytokines, chemokines and immune mediators in the central nervous system. This inflammatory milieu results in neuroglial damage by apoptosis. To test our hypothesis we set up an ex vivo model consisting of fresh brain slices from the cortex of normal rhesus monkeys, and allowed live spirochetes to penetrate the tissue. Microarray analysis of RNA extracted from tissues stimulated with spirochetes or medium alone revealed that the transcripts of genes that regulate oligodendrocyte and neuronal apoptosis were perturbed. Importantly, we also observed apoptosis of oligodendrocytes and neurons in spirochete-stimulated tissues by the in situ-activated caspase-3 and TUNEL assays. We then stimulated brain explants with live B. bugdorferi in the presence of brefeldin A, which blocks protein export from cells, and detected immune mediators in glial cells in situ by immunofluorescence staining and confocal microscopy. Spirochete-stimulated brain tissue explants showed the cytokines IL-6 in astrocytes and IL-1b in microglia. The chemokine IL-8 was detected in astrocytes and microglia. The chemokine CXCL13 was detected in microglia. The immune mediator COX-2 was detected in astrocytes and microglia. We further extended our study into an in vivo model in which live spirochetes were injected stereotaxically into the rhesus monkey brain and observed IL-6 in astrocytes. These results provide evidence that B. bugdorferi is able to induce an inflammatory environment in the brain with concomitant oligodendrocyte and neuronal death. As per our hypothesis, this phenomenon could be the basis of Lyme neuroborreliosis pathogenesis.