Host-interaction proteins Many of the virulence factors show wide divergence between hspEAsia and hpEurope, most likely because of co-evolution with the host. We anticipate that the list of well-diverged genes (Table 6) is enriched for host-interaction and potential virulence genes. We detected positively-selected amino-acid changes in two virulence factors: cagA and vacA (Table 7). Many OMP families showed loss of one of their resident

loci (hopMN, babABC, sabAB), whereas one family (oipA) showed duplication of its locus. Some OMP genes showed internal deletions (vacA-2) or interallelic homologous recombination (hopMN). A group-specific repertoire was seen for other OMP genes (homB, hopZ and hopQ), for other criteria. We also found substantial hspEAsia-hpEurope divergence in many OMPs (Table 5). The OMPs play important roles in host interaction such as Repotrectinib adhesion to the host cells and induction of immune responses [26]. For example, OipA induces IL-8 from host cells [70]. Systematic decay of OMP genes occurred during adaptation of H. pylori to a new host Selleck SB525334 of large felines, generating the new species of H. acinonychis [36]. Hence, the above OMP changes might reflect selection and/or fine regulation in host interaction, and more specifically,

may help avoid the host immune system. At least two OMPs show evidence for positive selection (Table 7). We do not yet know whether these OMP changes are related to immune response or adhesin activity. Lewis antigen mimicry is important for gastric colonization and adhesion. The mimicry affects innate immune recognition, inflammatory response, and T-cell polarization. Long-term infection by H. pylori might induce autoreactive anti-Lewis antigen antibodies [107]. Divergence in transferase genes for LPS biosynthesis may have resulted from co-evolution with the host immune system and could be related to G protein-coupled receptor kinase changes in Lewis

antigens in human populations. For example, the Le(a+b+) phenotype is almost absent in Caucasian persons whereas it occurs with a higher frequency in the Asian population [108]. This might be related to differences in pathogenicity and adaptation [109]. Changes in transporter genes, the loss of a putative amino acid utilization gene, divergence in a branched chain amino acid metabolism gene, differences in acetate metabolism genes, and divergence in motility and chemotaxis genes could also be related to host interaction, because these are related to the stomach environment. An interesting question is if these changes are related to variation in human diets. Electron transfer Several key electron transfer components were diverged between hspEAsia and hpEurope. The multiple and drastic changes in redox metabolism were unexpected. The systematic decay of all Mo-related genes through mutations in all (6/6) hspEAsia strains was the most striking. We do not know whether our findings reflect the biased environmental occurrence of Mo or the dietary habits of human populations.