Helicobacter pylori isolates from Greek children express type 2 and type 1 Lewis and alpha 1,6-glucan antigens in conjunction with a functional type IV secretion system

Helicobacter pylori infection is often acquired in childhood and can persist for life. Previous studies in adult patients have shown that H. pylori isolates from North American and European hosts express predominantly type 2 Lewis x (Lex) and Ley epitopes, while Asian strains have the capacity to express type 1 Lea and Leb structures. In order to understand the influence of environmental and host factors on the expression of Le antigens, we analysed 50 Greek H. pylori isolates from symptomatic children. Both CagA-positive and -negative strains were evaluated. The expression of Le antigens was determined by whole-cell indirect ELISA (WCE), and LPS profiles were assessed by gel electrophoresis and immunoblotting. Occurrence of Lex and/or Ley antigens was confirmed in 35 of the isolates (70 %) while 15 of the isolates were non-typable. It was found that 11 of the paediatric isolates had the propensity to express type 1 Leb blood-group antigen (22 %), a feature relatively uncommon in H. pylori isolates from adults. One strain expressed both Leb and Lea antigens. The majority of the isolates (49/50, 98 %) expressed alpha 1,6-glucan, an antigenic non-Le determinant present in the outer core region of H. pylori LPS. All Lex- and Ley-expressing strains also carried a functional cag pathogenicity island-encoding a type IV secretion system, capable of translocating CagA protein, as well as the vacAs1 allele, suggesting that Lex and Ley epitopes may aid the persistence of more aggressive strains. No association between bacterial virulence characteristics and the histopathological observations was evident.