Abstract
This review focuses on the main virulence factors characterizing Helicobacter pylori strains. Several pathogenic factors are important for the establishment and maintenance of H. pylori infection. Among those present in all isolates are the production of urease and phospholipases, the presence of flagella, the ability to attract neutrophils, the expression of ice A gene and a number of adhesins that ensure tissue-specific colonization. In addition, a subset of H. pylori strains is characterized by: i) a potent toxin (VacA) able to cause vacuolar degeneration of target cells by interfering with intracellular membrane fusion; and ii) the pathogenicity island (PAI), named Cag PAI that encodes for a putative secretory mechanism in which the cag A gene encodes an immunodominant antigen that is associated with cytotoxin expression.