Galactomannan and vicilin from fenugreek seeds (Trigonella foenum-graecum) impair pathogen-host interaction of Campylobacter jejuni with intestinal cells via JlpA.

Abstract

Campylobacter jejuni is the leading cause of severe enteritis worldwide. Identification of natural products against C. jejuni, inhibiting early-stage host-pathogen interactions is a promising strategy, particularly by blocking bacterial adhesion to and invasion into the host cells. This should help to reduce bacterial load in the vector animals. From the seeds of Trigonella foenum-graecum an aqueous extract (FHM) of high-molecular compounds (polysaccharides, proteins) was obtained. The polysaccharide was characterized as galactomannan (1,4-mannose backbone, substituted at O-6 with single galactose residues and galactose oligosaccharide chains). The protein part consisted of 50 kDa vicilin as main compound. FHM did not influence proliferation of C. jejuni and viability of Caco-2 cells (1-1000 μg/mL). FHM reduced bacterial adhesion to Caco-2 significantly (500-1000 μg/mL), which was due to interaction with the bacterial adhesin JlpA, preventing the interaction of this outer membrane protein to its ligand HSP90α (IC50 23.4 µg/mL). Bacterial invasion was reduced significantly. Both, polysaccharides as well as vicilin contribute to the observed antiadhesive effect. As vicilin-like proteins are widely found in plants from Fabaceae family a vicilin-enriched protein preparation from Pisum sativum was investigated for antiadhesive activity. These findings suggest that fenugreek seeds or vicilin-rich plant extracts could be used to develop novel strategies to control C. jejuni infections in food-producing animals, ultimately helping to decrease the prevalence of campylobacteriosis in humans.