Helicobacter pylori Genetic Polymorphisms in Gastric Disease Development

Infecting half of the world’s population, Helicobacter pylori is a medically important bacterium that induces a variety of gastric diseases, including gastritis, peptic ulcer disease, and gastric cancer. Sequencing of almost 1000 H. pylori isolates has revealed a diverse genome that contains abundant polymorphic genetic elements; many of these lie in factors likely to be associated with virulence. To ascertain the effect of these varying genetic elements, numerous epidemiological studies have investigated the contribution of the various polymorphisms to gastric disease development; particular focus has been placed on polymorphisms in the outer membrane proteins (OMPs), an effector protein, and a toxin produced by H. pylori. These studies have revealed geographic variation in the prevalence of various polymorphisms as well as in the associations between particular polymorphisms and gastric disease development. Furthermore, researchers have identified polymorphisms in multiple genes that frequently occur in combination. Though no single polymorphic genetic factor alone can fully account for gastric disease development in a population, the evaluation of multiple polymorphisms in a colonizing H. pylori strain can aid in the assessment of the pathogenic potential of the strain. Here we review specific H. pylori genetic polymorphisms (Bab proteins, Hom proteins, HopQ, SabA, SabB, OipA, IceA, VacA and CagA) that have been linked to disease outcome and discuss how geographic location and virulence factor polymorphisms together contribute to H. pylori-induced disease.