Lewis antigens in Helicobacter pylori: biosynthesis and phase variation

The lipopolysaccharides (LPS) of most Helicobacter pylori strains contain c omplex carbohydrates known as Lewis antigens that are structurally related to the human blood group antigens. Investigations on the genetic determinan ts involved in the biosynthesis of Lewis antigens have led to the identific ation of the fucosyltransferases of H. pylori, which have substrate specifi cities distinct from the mammalian fucosyltransferases. Compared with its h uman host, H. pylori utilizes a different pathway to synthesize the difucos ylated Lewis antigens, Lewis y and Lewis b. Unique features in the H. pylor i fucosyltransferase genes, including homopolymeric tracts mediating slippe d-strand mispairing and the elements regulating translational frameshifting , enable H. pylori to produce variable LPS epitopes on its surface. These n ew findings have provided us with a basis to further examine the roles of m olecular mimicry and phase variation of H. pylori Lewis antigen expression in both persistent infection and pathogenesis of this important human gastr ic pathogen.