Increase in Campylobacter jejuni Invasion of Intestinal Epithelial Cells under Low-Oxygen Coculture Conditions That Reflect theIn VivoEnvironment

Abstract

ABSTRACTCampylobacter jejuniinfection often results in bloody, inflammatory diarrhea, indicating bacterial disruption and invasion of the intestinal epithelium. WhileC. jejuniinfection can be reproducedin vitrousing intestinal epithelial cell (IEC) lines, low numbers of bacteria invading IECs do not reflect these clinical symptoms. Performingin vitroassays under atmospheric oxygen conditions neither is optimal for microaerophilicC. jejuninor reflects the low-oxygen environment of the intestinal lumen. A vertical diffusion chamber (VDC) model system creates microaerobic conditions at the apical surface and aerobic conditions at the basolateral surface of cultured IECs, producing anin vitrosystem that closely mimicsin vivoconditions in the human intestine. Ninefold increases in interacting and 80-fold increases in intracellularC. jejuni11168H wild-type strain bacteria were observed after 24-h coculture with Caco-2 IECs in VDCs under microaerobic conditions at the apical surface, compared to results under aerobic conditions. Increased bacterial interaction was matched by an enhanced and directional host innate immune response, particularly an increased basolateral secretion of the proinflammatory chemokine interleukin-8 (IL-8). Analysis of the invasive ability of a nonmotileC. jejuni11168HrpoNmutant in the VDC model system indicates that motility is an important factor in the early stages of bacterial invasion. The first report of the use of a VDC model system for studying the interactions of an invasive bacterial pathogen with IECs demonstrates the importance of performing such experiments under conditions that represent thein vivosituation and will allow novel insights intoC. jejunipathogenic mechanisms.