Modulating Phagocyte Activation: The Pros and Cons of Helicobacter pylori Virulence Factors

Helicobacter pylori (Hp) is a highly successful human pathogen that has colonized the gastric mucosa of approximately half of the world's population. Infection with this gram-negative bacterium induces a state of chronic inflammation that does not resolve the underlying infection and often leads to gastric or duodenal ulcers or more rarely to gastric adenocarcinoma or mucosa-associated lymphoid tissue (MALT) lymphoma. A characteristic feature of Hp-induced inflammation is the massive recruitment of phagocytes (particularly neutrophils) to the gastric mucosa, and it is generally believed that the ensuing tissue damage is due to the combined effects of bacterial factors and host inflammatory mediators. Multiple bacterial virulence factors are known to modulate Hp-induced inflammation, including LPS, PicB, urease, and the vacuolating cytotoxin VacA 1. Of particular interest in this regard is a recently identified virulence factor called Hp neutrophil-activating protein (HP-NAP)....