**2.** *Helicobacter pylori*

*Helicobacter pylori* (*H. pylori*) is a 3 micrometer long gram-negative spiral bacteria that colonizes the human gastric epithelium's luminal surface of approximately 50% of humans worldwide. Once acquired, it establishes a chronic persistent infection that

leads to ulcer, cancer or MALT lymphoma [4]. *H. pylori* is conformed by BabA, SabA, OipA and HopQ bacterial colonization factors, and the effector proteins CagA, VacA, urease, catalase, flagellin, mucinase, lipase, neutrophil activating protein, lipopolysaccharides, Cholesterol-Glucosyltransferase and HtrA considered as virulence/ pathogenicity factors, and the outer membrane vesicles [5–9]. **Figure 1** shows the complete structure and components of *H. pylori*. Although it has been clearly established that *H. pylori* disrupts gastric epithelial barrier function [10, 11] the precise mechanism(s) remain elusive. A major structure of *H. pylori* is the syringe-like Type IV secretion system which is found in many species of bacteria [12, 13]; this system plays an essential role in the translocation of CagA into host cells [14].
