Lactobacillus johnsonii glycolipids, their structure and immunoreactivity with sera from inflammatory bowel disease patients.

Structural studies of the major glycolipids produced by two Lactobacillus johnsonii (LJ) strains, LJ 151 isolated from intestinal tract of healthy mice and LJ 142 isolated from mice with experimentally induced inflammatory bowel disease (IBD), were performed. Two major glycolipids, GL1 and GL2, were present in lipid extracts from L. johnsonii 142 and 151 strains. Glycolipid GL1 has been identified as β-D-Glcp-(1→6)-α-D-Galp-(1→2)-α-D-Glcp-diglyceride and GL2 as α-D-Galp-(1→2)-α-D-Glcp-diglyceride. The main fatty acid residues identified by gas-liquid chromatography-mass spectrometry were palmitic, stearic and lactobacillic acids. Besides structural elucidation of the major glycolipids, the aim of this study was to determine the immunochemical properties of these glycolipids and to compare their immunoreactivity to that of polysaccharides obtained from the same strains. Sera from rabbits immunized with bacterial cells possessed much higher serological reactivity with polysaccharides than with glycolipids. Inversely, reactivity of the glycolipids with human sera from patients with IBD was much higher than that determined for the polysaccharides, while reactivity of glycolipids with human sera from healthy individuals was much lower than one measured for the polysaccharides. Results indicate that glycoconjugates from Lactobacillus cell wall act as antigens and may represent new IBD diagnostic biomarkers.