Induction of inflammasome-dependent signalling in the human monocytic cell line THP-1 by Campylobacter lipooligosaccharides

The Campylobacter lipooligosaccharides (LOS) can stimulate membrane-bound innate immune receptors in human macrophages. However, the association of Campylobacter LOS in the stimulation of cytosolic receptors or the inflammasome remains poorly characterised. Therefore, the aim of this study was to determine the role of Campylobacter LOS in the activation of NLRP3 inflammasome-dependent signalling in a human monocytic cell line. The induction of NLRP3 inflammasome-mediated IL-1β and Caspase-1 secretion in THP-1 supernatants was quantified using ELISA following co-culture of THP-1 cells with LOS extracts from wild type C. jejuni 11168, mutant C. jejuni 11 168 with reduced LOS and two wild type C. coli strains (RM1875 and 76339). Our results demonstrate that LOS purified from both C. jejuni and C. coli can induce Caspase-1 and IL-1β production in human macrophages. However, C. jejuni 11 168 mutant LOS with modified lipid A and lack of core oligosaccharides stimulated significantly reduced Caspase-1 and IL-1β. This result was also replicated in co-culture of live wild type and mutant C. jejuni with THP-1 cells. This study provides new insight into the interaction of Campylobacter with human macrophages and suggests that variation in LOS structure may alter NLRP3 inflammasome activation.