H. pylori tips off host

Helicobacter pylori triggers gastric inflammation by injecting peptidoglycan from its cell wall into epithelial cells, where it is recognized by an intracellular pathogen recognition molecule, researchers report in Nature Immunology this week.

Richard Ferrero and colleagues at Institut Pasteur in France note in their paper that H. pylori strains carrying the cag pathogenicity island (cagPAI) are known to be more often associated with severe gastric inflammation and its pathogenic consequences in humans, but the mechanism underlying the link had been poorly understood.

Because H. pylori doesn't invade epithelial cells but lives outside among a wide range of commensal bacteria, "the question was, if together with commensal bacteria you have bacteria that are not commensal but pathogens, how are they recognized?" said Rino Rappuoli, from Chiron Research Center, Siena, Italy, who wrote an accompanying News and Views article.

The answer, Ferrero told The Scientist, is that "H. pylori is...