* To whom correspondence should be addressed.
Received October 4, 2019; Revised November 29, 2019; Accepted November 30, 2019
Helicobacter pylori is an important human pathogen that causes gastritis, gastric and duodenal ulcers, and gastric cancer. O-polysaccharides of H. pylori lipopolysaccharide (LPS) are composed of (β1→3)-poly(N-acetyllactosamine) (polyLacNAc) decorated with multiple α-L-fucose residues. In many strains, their terminal LacNAc units are mono- or di-fucosylated to mimic Lewis X (Lex) and/or Lewis Y (Ley) oligosaccharides. The studies in rhesus macaques as a model of human infection by H. pylori showed that this bacterium adapts to the host during colonization by expressing host Lewis antigens. Here, we characterized LPS from H. pylori strains used in the previous study, including the parental J166 strain and the three derivatives (98-149, 98-169, and 98-181) isolated from rhesus macaques after long-term colonization. Chemical and NMR spectroscopic analyses of the LPS showed that the parent strain expressed Lex, Ley, and H type 1 terminal oligosaccharide units. The daughter strains were similar to the parental one in the presence of the same LPS core and fucosylated polyLacNAc chain of the same length but differed in the terminal oligosaccharide units. These were Lex in the isolates 98-149 and 98-169, which corresponded to the Lea phenotype of the host animals, and Ley was found in the 98-181 isolate from the macaque characterized by the Leb phenotype. As Lea and Leb are isomers of Lex and Ley, respectively, the observed correlation confirmed adaptation of the expression of terminal oligosaccharide units in H. pylori strains to the properties of the host gastric mucosa. The 98-181 strain also acquired glucosylation of the polyLacNAc chain and was distinguished by a lower expression of fucosylated internal LacNAc units (internal Lex) as a result of decoration of polyLacNAc with β-glucopyranose, which may also play a role in the bacterial adaptation.
KEY WORDS: Helicobacter pylori, lipopolysaccharide, O-polysaccharide, poly(N-acetyllactosamine), glucosylation, Lewis antigen expression, bacterial adaptation, rhesus macaque