| Summary: | <p>Abstract</p> <p>Background</p> <p>The <it>homB </it>gene is a <it>Helicobacter pylori </it>disease-marker candidate, strongly associated with peptic ulcer disease, while <it>homA</it>, its paralogue gene with 90% sequence identity, is correlated with non-ulcer dyspepsia. The HomB encoded outer membrane protein was shown to contribute to the proinflammatory properties of <it>H. pylori </it>and also to be involved in bacterial adherence.</p> <p>This study investigated the distribution of <it>homB </it>and <it>homA </it>genes in 455 <it>H. pylori </it>strains from East Asian and Western countries, and carried out sequence comparison and phylogenetic analyses.</p> <p>Results</p> <p>Both <it>homB </it>and <it>homA </it>genes were heterogeneously distributed worldwide, with a marked difference between East Asian and Western strains.</p> <p>Analysis of <it>homB </it>and <it>homA </it>sequences revealed diversity regarding the number of copies and their genomic localization, with East Asian and Western strains presenting different genotypes. Moreover, <it>homB </it>and <it>homA </it>sequence analysis suggests regulation by phase variation. It also indicates possible recombination events, leading to gene duplication or <it>homB</it>/<it>homA </it>conversion which may as well be implicated in the regulation of these genes. Phylogenetic reconstruction of <it>homB </it>and <it>homA </it>revealed clustering according to the geographic origin of strains. Allelic diversity in the middle region of the genes was observed for both <it>homB </it>and <it>homA</it>, although there was no correlation between any allele and disease. For each gene, a dominant worldwide allele was detected, suggesting that <it>hom</it>B/<it>hom</it>A allelic variants were independent of the geographical origin of the strain. Moreover, all alleles were demonstrated to be expressed <it>in vivo</it>.</p> <p>Conclusion</p> <p>Overall, these results suggest that <it>homB </it>and <it>homA </it>genes are good candidates to be part of the pool of <it>H. pylori </it>OMPs implicated in host-bacteria interface and also contributing to the generation of antigenic variability, and thus involved in <it>H. pylori </it>persistence.</p>
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