Helicobacter pylori Lipopolysaccharides and Lewis Antigens
Anthony P. Moran and M. Stephen Trent
from: Helicobacter pylori: Molecular Genetics and Cellular Biology (Edited by: Yoshio Yamaoka). Caister Academic Press, U.K. (2008)
The outer membrane of Helicobacter pylori, like other Gram-negative bacteria, contains lipopolysaccharides (LPSs) which are important for the structure of the bacterial cell envelope and the interaction of the bacterium with its environment. They are a family of phoshorylated lipoglycans, composed of a lipid moiety, termed lipid A, a core oligosaccharide and an O-chain polysaccharide. The present chapter reviews the main biological attributes of H. pylori LPS and the understanding that has been gained into the molecular genetics, structure and contributing properties of this class of molecule to H. pylori pathogenesis. Compared with LPSs of other bacteria, LPS of H. pylori has low immunoactivities, the molecular basis for which is the under-phosphorylation and unusual acylation pattern of the lipid A component that interacts with immune receptors. Important insights have been gained into the biosynthesis and modification pathways that remodel H. pylori lipid A and hence aid persistence of the bacterium in the gastric mucosa. Notwithstanding this, the LPS core exhibits structural properties (i.e., laminin binding and pepsinogen induction) the molecular variation of which may influence the virulence of H. pylori strains. Furthermore, the O-chains of most strains, though not all isolates (i.e., those associated with asymptomatic infection), mimic Lewis and related blood group antigens. The nature of these antigens in H. pylori, their genetic determination and regulation of expression, particularly of the fucosyltransferases required for synthesis, as well as the biological consequences of this mimicry have provided a better understanding of the molecular pathogenesis of H. pylori read more ...