Immunoreactive proteins of Campylobacter concisus, an emergent intestinal pathogen

Campylobacter concisus is an emerging pathogen of the human gastrointestinal tract. Recently, a significantly higher prevalence of C.similar to concisus DNA and higher levels of antibodies specific to C.similar to concisus was detected in children with Crohn's disease when compared with controls. The aim of this study was to identify C.similar to concisus immunoreactive antigens. Proteins from C.similar to concisus were separated using two-dimensional gel electrophoresis, and sera from 10 C.similar to concisus-positive children with Crohn's disease were employed for immunoprobing. The patients sera reacted with 69 spots, which corresponded to 31 proteins identified by mass spectrometry. The proteins were functionally classified as involved in chemotaxis, signal transduction, flagellar motility, surface binding and membrane protein assembly. Although the individual patients sera reacted to different sets of proteins, common antigens that were recognized by all patients were flagellin B, ATP synthase F1 alpha subunit, and outer membrane protein 18. Cross-reactivity between proteins of the Campylobacter genus was tested using patients sera absorbed with Campylobacter showae, Campylobacter jejuni and Campylobacter ureolyticus. Most of the C.similar to concisus immunoreactive proteins identified in this study showed cross-reactivity with other species except for three antigens. In conclusion, this study has identified C.similar to concisus proteins that are immunoreactive within patients with Crohn's disease.