TOLL-LIKE RECEPTORS IN LYME NEUROBORRELIOSIS

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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 likely caused by inflammatory effects of the tick-borne spirochete Borrelia burgdorferi on the nervous system. Microglia, the resident macrophage cells within the central nervous system (CNS), are important in initiating an immune response to microbial products. In addition, astrocytes, the major CNS glial cell type, also can contribute to brain inflammation. TLRs (Toll-Like Receptors) are used by glial cells to recognize pathogen-associated molecular patterns (PAMPs), mediate innate responses, and initiate an acquired immune response. Here we hypothesize that because of their PAMP specificities, TLR 1, 2, 5, and 9 may be involved in the pathogenesis of Lyme neuroborreliosis. Previous reports have shown that the rhesus monkey is the only animal model to exhibit signs of Lyme neuroborreliosis. Therefore, we used primary cultures of rhesus astrocytes and microglia to determine the role of TLRs in mediating pro-inflammatory responses to B. burgdorferi. Results of experiments involving quantification of TLR transcript by RT-PCR and microscopic observation of expression of TLR protein indicate that microglia and astrocytes respond to B. burgdorferi through TLR1/2 and TLR5. In addition, we observed that phagocytosis of B. burgdorferi by microglia enhances not only the expression of TLR1, 2, and 5, but also that of TLR4. Taken together, our data provide proof of the concept that astrocyte and microglial TLR 1, 2, and 5 are involved in the in vivo response of primate glial cells to B. burgdorferi. The pro-inflammatory molecules elicited by these TLR-mediated responses could be a significant factor in the pathogenesis of Lyme neuroborreliosis. A manuscript based on these results was published in the journal Infection and Immunity.