Helicobacter pylori is considered the most prevalent infectious agent among humans, and it causes gastric inflammation, gastroduodenal ulcers, and a risk of gastric cancer. We performed a genomewide linkage analysis among Senegalese siblings phenotyped for H. pylori-reactive serum immunoglobulin G. A multipoint LOD score of 3.1 was obtained at IFNGR1, the gene that encodes chain 1 of the interferon-gamma (IFN-gamma) receptor. Sequencing of IFNGR1 revealed -56C-->T, H318P, and L450P variants, which were found to be associated with high antibody concentrations. The inclusion of these in the linkage analysis raised the LOD score to 4.2. The variants were more prevalent in Africans than in whites. Our findings indicate that IFN-gamma signaling plays an essential role in human H. pylori infection, and they contribute to an explanation of the observations of high prevalences and relatively low pathogenicity of H. pylori in Africa. Moreover, they provide further support for the value of genomewide linkage studies in the analysis of susceptibility to infection and other complex genetic traits.
Helicobacter pylori urease was characterized by means of an enzyme histochemical electron microscopic technique. Ultrastructural analysis revealed no urease activity in one strain; in seven H. pylori strains (43.75%), urease activity was associated with the cell membrane. Eight strains (50.0%) showed reaction product located within the cytoplasm. Urease activity showed no correlation with localization of activity. Our results demonstrate that H. pylori urease is not uniform in all H. pylori strains, and differences in activity and localization of urease activity may account for different virulence activities.
These results suggest that reinfection is not dependent on the H. pylori prevalence in family members and that H. pylori reinfection after successful eradication therapy is an unlikely event.
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