Lipopolysaccharide Structural Differences between Western and Asian Helicobacter pylori Strains.

Recent structural analysis of the lipopolysaccharide (LPS) isolated from Helicobacter pylori G27 wild-type and O-antigen ligase mutant resulted in the redefinition of the core-oligosaccharide and O-antigen domains. The short core-oligosaccharide (Glc⁻Gal⁻Hep-III⁻Hep-II⁻Hep-I⁻KDO) and its attached trisaccharide (Trio, GlcNAc⁻Fuc⁻Hep) appear to be highly conserved structures among H. pylori strains. The G27 LPS contains a linear glucan⁻heptan linker between the core-Trio and distal Lewis antigens. This linker domain was commonly identified in Western strains. In contrast, out of 12 partial LPS structures of Asian strains, none displayed the heptan moiety, despite the presence of Lewis antigens. This raises the question of how Lewis antigens are attached to the Trio, and whether the LPS structure of Asian strains contain another linker. Of note, a riban was identified as a linker in LPS of the mouse-adapted SS1 strain, suggesting that alternative linker structures can occur. In summary, additional full structural analyses of LPS in Asian strains are required to assess the presence or absence of an alternative linker in these strains. It will also be interesting to study the glucan-heptan linker moieties in pathogenesis as H. pylori infections in Asia are usually more symptomatic than the ones presented in the Western world.