Structural and Immunological Insights into the Lipooligosaccharide of the Marine Bacterium Kangiella japonica KMM 3897

The lipooligosaccharide (LOS) of the marine bacterium <i>Kangiella japonica</i> KMM 3897 was structurally characterized using chemical analysis, NMR spectroscopy, and MALDI-TOF mass spectrometry. The oligosaccharide core consists of a monophosphorylated trisaccharide containing 2-amino-2-deoxy-D-glucose, D-<i>glycero</i>-D-<i>manno</i>-heptose, and 3-deoxy-D-<i>manno</i>-oct-2-ulosonic acid. The penta-acylated lipid A moiety features a glucosamine disaccharide backbone with phosphate groups and amide- and ester-linked primary fatty acids [i11:0 (3-OH)], along with a secondary acyl chain (i11:0 or 11:0). Immunostimulatory assays revealed that <i>K. japonica</i> KMM 3897 LOS induced significantly weaker cytokine production in human peripheral blood mononuclear cells (PBMCs) compared with <i>E. coli</i> LPS. Notably, it exhibited potent antagonistic activity against <i>E. coli</i> LPS-mediated toxicity and suppressed caspase-4 activation in LPS-treated PBMCs. These findings highlight its anti-inflammatory and protective properties.