VARIATIONS IN THE EXPRESSION OF TERMINAL OLIGOSACCHARIDE UNITS AND GLYCOSYLATION OF POLY(<i>N</i>-ACETYLLACTOSAMINE) CHAIN IN THE <i>Helicobacter pylori </i>LIPOPOLYSACCHARIDE UPON COLONIZATION OF RHESUS MACAQUES
<i>Helicobacter pylori</i> is an important human pathogen that causes gastritis, gastric and duodenal ulcers, and gastric cancer. O-polysaccharides of <i>H. pylori</i> lipopolysaccharides (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 monoor di-fucosylated to mimic Lewis X (Le<sup>x</sup>) and/or Lewis Y (Le<sup>y</sup>) oligosaccharides. The studies in rhesus macaques as a model of human infection by <i>H. pylori</i> showed that this bacterium adapts to the host during colonization by expressing host Lewis antigens. Here, we characterized LPS from <i>H. pylori</i> 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 longterm colonization. Chemical and NMR spectroscopic analyses of the LPS showed that the parental strain expressed Le<sup>x</sup>, Le<sup>y</sup>, 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 Le<sup>x</sup> in the isolates 98-149 and 98-169, which corresponded to the Le<sup>a</sup> phenotype of the host animals, and Le<sup>y</sup> was found in the 98-181 isolate from the macaque characterized by the Le<sup>b</sup> phenotype. As Le<sup>a</sup> and Le<sup>b</sup> are isomers of Le<sup>x</sup> and Le<sup>y</sup>, respectively, the observed correlation confirmed adaptation of the expression of terminal oligosaccharide units in <i>H. pylori</i> strains to the properties of the host gastric mucosa. The 98-181 strain also acquired glycosylation of the polyLacNAc chain and was distinguished by a lower expression of fucosylated internal LacNAc units (internal Le<sup>x</sup>) as a result of decoration of polyLacNAc with β-glucopyranose, which may also play a role in the bacterial adaptation.