The human pathogen Neisseria gonorrhoeae produces an array of diseases ranging from urethritis and cervicitis to pelvic inflammatory disease. Early events in the establishment of infection involve interactions between N. gonorrhoeae and the mucosal surface, which lead to the local release of inflammatory mediators. Because of this, it is important to identify the bacterial factors and host cell components that contribute to inflammation. The innate immune system is the first line of defense against invading microorganisms. Toll-like receptors (TLRs) are a part of this innate immune defense, recognizing conserved microbial patterns and initiating signal transduction pathways that direct the inflammatory response. These germ-line encoded proteins are expressed to varying degrees in both professional and non-professional immune cells. Epithelial cells that line the mucosal surface are often the initial site of contact for microorganisms, making them responsible for alerting adjacent epithelium and the underlying immune cells of the potential danger posed by an infectious challenge. Little is known about the mechanism of epithelial cell activation by pathogens, and the receptors and secondary mediators involved in this regulated response. We hypothesize that the interactions between STD pathogens and the TLRs expressed on mucosal epithelial cells are responsible for initiating and coordinating the subsequent inflammatory response. Our previous work established that cervical epithelial cells fail to express the LPS receptor TLR4 and the associated molecule MD-2. In contrast, they express a variety of other TLRs that appear to be functionally capable of recognizing their cognate ligands. This includes TLR2 for the recognition of bacterial lipoproteins and TLR9 for the recognition of bacterial DNA. The goal of this proposal is to identify the innate immune receptors in the urogenital tract that are responsible for the recognition of N. gonorrhoeae and the initiation of the immune response.
We aim to: (1) characterize the interactions between TLR2 and gonococcal lipoproteins during gonococcal infections; (2) examine the role of bacterial DNA and TLR9 signaling in epithelial cell responses to Neisseria; (3) examine the signaling pathways activated during gonococcal infection; and (4) examine the role played by TLRs in gonococcal pathogenesis using the mouse model for genital tract infection in defined TLR mutants.
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