Campylobacter is one of the leading causes of bacterial food borne gastroenteritis worldwide. Solely in the European Union the number of confirmed cases in 2011 was 220,209 being the first gastrointestinal pathogen. C. jejuni is the most commonly reported species (90%), followed by C. coli (5-10%). However, the repercussion of C. coli infections on human health remains largely unknown due to various factors: underestimation of the incidence of C. coli infections; differences between C. coli and C. jejuni in case-control studies; limited data on the interaction of C. coli with the host. Campylobacteriosis is an acute diarrheal disease in which severe inflammation may affect the small and large intestine. However, occasionally infection with Campylobacter precedes the Guillain–Barré syndrome (GBS) and other autoimmune neuropathies. Due to the higher incidence of C. jejuni over C. coli and the discovery of several strains of C. jejuni expressing sialylated lipooligosaccharides (LOS) mimic the host ganglioside antigens, the research of etiopathogenesis of GBS were mainly focused on C. jejuni, ignoring the relative contribution of C. coli to the disease. A recent study performed in our group revealed a broader diversity in C. coli LOS biosynthesis locus than C. jejuni. In addition, we identified two new Campylobacter sialyltransferases (cst-IV, cst-V) in different C. coli strains expressing sialo-LOS. These findings would imply that bacterial factors considered important in the etiology of GBS crossed species barriers, and thus also C. coli could contribute to the disease. However, in contrast to C. jejuni, the characterization of C. coli surface glycan structures has been largely neglected. Aim of this project is to fill the gap of knowledge between C. jejuni and C. coli. Particular effort will be made to characterize the structure variability of C. coli LOS among several strains, to identify the genes involved in the synthesis of these surface structures and to study the biochemical proprieties of C. coli-associated sialyltransferases. Mass spectrometry combined with high-throughput DNA sequencing of the whole genome will be used to infer the LOS outer core structures of a large number of C. coli strains from our collection. The strains will be selected on the basis of available preliminary information of the LOS locus. Furthermore, in order to characterize C. coli sialyltransferases in terms of activity and substrate specificity, recombinant proteins will be created and tested for sialyltransferase activity using FCHASE-labelled acceptors. . These two parts of the project will be performed in collaboration with two international partners who will provide technical supports and supervision in performing the experiments. In addition, in order to get insight on the possible role of C. coli in post-infection sequelae the project will focused in investigating the mechanisms of interaction between C. coli sialo-LOS structures and the human host innate immunity. Thus, purified LOS and live cells of C. coli strains (WTs, mutants and complemented mutants) will be used to treat HEK-Blue™ hTLR4 cells which have been designed for studying the stimulation of human TLR4 by monitoring the activation of NF-κB and AP-1. A comprehensive analysis of the LOS structures on C. coli, how these structures are synthetized and how they interact with the host immune system, will provide a better understanding on the possible role of this species in the pathogenesis of post-infection sequelae of human patients.