The Gram-negative invasive bacterium Campylobacter jejuni (C. jejuni) is the leading cause of bacterial food-borne gastrointestinal illness worldwide, with approximately 2-3 million annual cases in the United States alone. In addition, C. jejuni infection is associated with post-infectious complications such as arthritis and the neurodegenerative disorder Guillian-Barri syndrome. Therefore, C. jejuni infection has the potential to cause both acute/chronic intestinal disorders and debilitating extra-intestinal illnesses. Although C. jejuni infection represents a serious health concern, limited information is available on both host responses and the molecular mechanisms by which the microorganism triggers diseases. The lack of a murine model mimicking C. jejuni induced pathogenesis likely contributed to this gap of knowledge. In preliminary studies, we observed that gnotobiotic C. jejuni-associated IL-10-/-;NF?BEGFP mice developed severe bloody diarrhea and intestinal inflammation associated with NF?B activation. In this proposal, we hypothesize that NF?B signaling derived from intestinal epithelial cells and myeloid cells contributes to the host response to C. jejuni infection and to the reestablishment of intestinal homeostasis. Consequently, improper temporal and spatial (cellular) activation of NF?B signaling will have pathological consequences for the host, leading to failure to clear the microorganism and development of inflammation. We will test our hypothesis with two SPECIFIC AIMS: 1) Dissect the cellular contribution of NF?B signaling in C. jejuni mediated pathogenesis. 2) Determine the impact of RelA-dependent genes on C. jejuni translocation and intracellular survival. This project will utilize both in vivo and in vitro approaches to define the role and function of enterocyte and myeloid-derived NF?B signaling in the host response to C.jejuni. Our goal is to selectively delete RelA (NF?B subunit) in enterocytes and myeloid cells of IL-10-/- mice to address the function of NF?B signaling in the host response to C. jejuni. The ultimate goal of this proposal is to understand, at the molecular level, host responses to C. jejuni infection and to determine the functional involvement of various signaling events in the development of the pathogenesis. This gain of knowledge could be utilized to modulate the deleterious impact of this pathogenic microorganism on the host and help design effective preventive measures. Future goals include the characterization of C. jejuni virulence factors responsible for the pathogenesis of the bacterium. PUBLIC HEALTH RELEVANCE: Campylobacter jejuni (C.jejuni) infection has become the predominant cause of bacterial-food borne diarrheal diseases worldwide with up to 2.4 million cases annually in the United States alone. Despite this health and socio-economical burden, the scientific and medical community knows little about the host response to this pathogenic microorganism. This gap of knowledge negatively impact on the design of new therapeutic alternative to control for C.jejuni mediated illnesses. This project investigates the molecular mechanism of C. jejuni-induced pathogenesis through genetic removal of the NF?B transcriptional subunit RelA (p65) in the susceptible murine strain IL-10-/-. The project will elucidate the function of enterocyte- and myeloid-derived NF?B signaling in host responses to C. jejuni infection. This new knowledge would significantly contribute to the understanding of C. jejuni pathogenesis and could lead to the design of new therapeutic strategies.