Epitope dissection of receptor-active gangliosides with affinity for Helicobacter pylori and influenza virus.

Receptor-active gangliosides with affinity for Helicobacter pylori and influenza virus were chemically modified and analyzed by negative ion fast atom bombardment mass spectrometry (FAB MS) or electron ionization mass spectrometry (EI MS) after permethylation. Derivatizations included mild periodate oxidation of the sialic acid glycerol tail or conversion of the carboxyl group to primary alcohol or amides. The modified gangliosides were then tested for binding affinity using thin-layer plates overlaid with labeled microbes or microbe-derived proteins. Mild periodate oxidation, which shortens sialic acid tail without destruction of sugar cores, abolished or drastically reduced binding of H. pylori and avian influenza virus to sialyl-3-paragloboside (S-3-PG). The same effect was observed in the case of binding of the human influenza virus to receptor-active gangliosides of human leukocytes. Conversion of S-3-PG or leukocyte gangliosides to primary alcohols or amides also abolished the binding. However, mild periodate oxidation had no effect on binding of NAP (neutrophil-activating protein of H. pylori) to the active ganglioside.