Chemical synthesis and antibody affinity of epitope fragments from Helicobacter pylori lipopolysaccharide

Helicobacter pylori (Hp) is responsible for chronic gastritis, peptic ulcers, and even gastric cancers. Currently, there is no vaccine to prevent or treat Hp infections. Here, we described the chemical synthesis of α-1,6-glucans with different lengths (di- to hexasaccharide), which are present in the core oligosaccharide of Hp lipopolysaccharide (LPS). The 1,2-cis-glucosidic bonds were constructed successfully using a synergistic glycosylation strategy based on acyl remote participation and solvent effects. The results of glycan microarrays indicated that all synthesized α-1,6-glucan fragments possessed a strong binding to IgG antibodies in both rabbit serum immunized with Hp O1 LPS and patient serum infected with Hp. The α-1,6-linked trisaccharide exhibited strong binding affinity to anti-LPS rabbit IgG antibodies. The α-1,6-glucan trisaccharide and pentasaccharide elicited a strong response to IgG antibodies in sera of most Hp-infected patients. Some patients’ sera exhibited strong binding activity with α-1,6-linked disaccharide. The results suggest that the α-1,6-glucan disaccharide, trisaccharide and pentasaccharide could be important carbohydrate antigen fragments in Hp lipopolysaccharide.