Structural and Functional Diversity of Lipid A from Helicobacter pylori

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This study was focused on the structural and functional diversity and change for lipid A from Helicobactor pylori to evaluate the relationship between the structure of lipid A, its immunobiological activities, the infective activity (potency of colonization in stomach) of strains, and varied diseases. By our established quick screening procedure in terms of negative mode ESI-and MALDI-TOF/MS combined with the modified TLC blotting, lipid As of over 40 H. pylori bacteria obtained from different strains or from batches under different culture conditions were evaluated. Four distinct structures were detected. The most predominant form was HPLA_1549 and the second was HPLA_1295. It was found that those structures were changed to HPLA_1506 and HPLA_1252 by the repeated cultivation, but not by the morphological change of the bacteria. The cytokine inducing activities from human peripheral whole blood cells or from human peripheral blood mononuclear cells were evaluated on these lipid As. They possessed very weak, almost no, activities for the production of inflammatory cytokines such as tumor necrosis factor α, interleukin (IL)-12 or interferon-γ, except for the weak but distinct IL-6 inducing activity of one structure, HPLA_1295. In contrast, the lipid As showed high IL-18 inducing activity. It was found that strains possessing the IL-6 inducible lipid A structure (HPLA_1295) had statistically high score for the infection against C57BL/6 mice, suggesting a relation between lipid A structure and infection.