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The stomach-loving bacterium Helicobacter pylori infects nearly half of the world's population. Although some strains are harmless, others are linked to stomach inflammation, gastric cancer and nearly all cases of peptic ulcers. Now researchers writing in this week's issue of the journal Science report the discovery of a protein that H. pylori uses to co-opt the body's immune response to further its own ends. The findings could aid the development of new treatment strategies to stop the persistent bug.
In order for an H. pylori infection to occur, the bacteria must adhere to the cells lining the stomach wall. Nearly a decade ago, scientists identified a molecule called Lewis B antigen (Leb) that the bacterium uses to accomplish that. Five years later, researchers discovered a protein dubbed BabA, which aids this adhesion. The new work began with the intriguing observation that a genetically engineered strain of H. pylori that lacked BabA could still adhere to inflamed stomach tissue of a person infected with H. pylori. The mutant strain could not, however, attach to the stomach cells of an uninfected subject. Thomas Bor¿n of Umea University in Sweden and his colleagues thus posited that a second so-called adhesin protein, one tied to molecules involved in inflammation, must be at work. Subsequent research revealed that the bacteria were indeed binding to sugar molecules secreted by the stomach's cells as a distress call to the immune system, using an adhesion protein that the team named SabA.
Because both BabA and SabA seem to be unique to H. pylori, the team postulates that the new findings might be used to combat the widespread bacteria. According to study co-author Douglas E. Berg of Washington University School of Medicine, the researchers hope "that understanding how these adhesins work will lead to a vaccine against H. pylori infections and to new drugs to treat or diminish their severity." Such a tailored vaccine would be preferable to widespread use of antibiotics, which could produce even hardier, drug-resistant strains of H. pylori.