The relationship between O-chain expression and colonisation ability of Helicobacter pylori in a mouse model

The influence of lipopolysaccharide (LPS) O-polysaccharide chain production on the colonisation ability of Helicobacter pylori in four mouse models (N MRI, C57BL/6, CBA/Ca, and BALB/cA mice) was studied. H. pylori strains that produced smooth-form LPS (S-LPS) detectable in silver-stained electrophore tic gels colonised mice. In contrast, a laboratory-passaged strain G50 and the culture collection strain CCUG 17874 did not colonise mice; the former strain produced low amounts of O-chains only detectable in immunoblotting b ut not in silver-stained gels, whereas the latter produced rough-form LPS ( R-LPS) without O-chains. Furthermore, a galE isogenic mutant, which produce d R-LPS, did not colonise mice. However, after repeated broth culture, stra ins G50 and CCUG 17874 produced S-LPS detectable in silver-stained gels and were capable of colonising mice. Consistent with the production of O-chain s, all colonising strains produced Lewis (Le) antigens, Le(x) and/or Le(y). Except for low expression of Le(y) by non-colonising G50, reflecting low p roduction of O-chains, all other non-colonising strains and the galE mutant lacked expression of Le antigens consistent with their production of R-LPS . Lectin typing of strains supported these findings, and also showed that l ectin types did not differ before and after colonisation. The low level of O-chain production and Le antigen expression by the non-colonising G50 may not be sufficient to aid colonisation. Examination of protein profiles of H . pylori strains before inoculation showed that protein expression was not significantly different between colonising and non-colonising strains. Thes e results show that S-LPS production with O-chain expression is required by H. pylori for colonisation in a number of mouse models and that care shoul d be taken with inoculating H. pylori strains that loss of O-chains does no t occur during subculturing. (C) 2000 Federation of European Microbiologica l Societies. Published by Elsevier Science B.V. All rights reserved.