MOLECULAR MIMICRY OF HOST STRUCTURES BY BACTERIAL LIPOPOLYSACCHARIDESAND ITS CONTRIBUTION TO DISEASE

The core oligosaccharides of low-molecular-weight lipopolysaccharide ( LPS), also termed lipooligosaccharide (LOS), of pathogenic Neisseria s pp. mimic the carbohydrate moieties of glycosphingolipids present on h uman cells. Such mimicry may serve to camouflage the bacterial surface from the host. The LOS component is antigenically and/or chemically i dentical to lactoneoseries glycosphingolipids and can become sialylate d in Neisseria gonorrhoeae when the bacterium is grown in the presence of cytidine 5'-monophospho-N-acetylneuraminic acid, the nucleotide su gar of sialic acid. Strains of Neisseria meningitidis and Haemophilus influenzae also express similarly sialylated LPS. Sialylation of the L OS influences susceptibility to bactericidal antibody, may decrease or prevent phagocytosis, cause down-regulation of complement activation, and decrease adherence to neutrophils and the subsequent oxidative bu rst response. The core oligosaccharides of LPS of Campylobacter jejuni serotypes which are associated with the development of the neurologic al disorder, Guillain-Barre syndrome (GBS), exhibit mimicry of ganglio sides. Cross-reactive antibodies between C. jejuni LPS and ganglioside s are considered to play an important role in GBS pathogenesis. In con trast, the O-chain of a number of Helicobacter pylori strains exhibit mimicry of Lewis(x) and Lewis(y) blood group antigens. The role of thi s mimicry remains to be investigated, but may play a role in bacterial camouflage, the induction of autoimmunity and immune suppression in H . pylori-associated disease.