Helicobacter pylori

Helicobacter pylori (H. pylori) is possibly the most widespread human pathogen worldwide. Since it was initially suggested in 1983 by Marshall and Warren to be implicated in gastritis and peptic ulcer disease, H. pylori has also been implicated in gastric carcinoma and was classified as a class I carcinogen. During the last two decades, a significant body of research has revealed the multiple processes that this Gram-negative bacterium activates to cause gastroduodenal disease in humans. Most infections are acquired early in life and may persist for the entire life of the individual. While infected individuals mount an inflammatory response, which becomes chronic, along with a detectable adaptive immune response, these responses are ineffective in clearing the infection. H. pylori has unique features that allow it to reside within the harsh conditions of the gastric environment and also to evade the host immune response. Although only a fraction of infected individuals develop the significant clinical diseases associated with this infection, it is important to eradicate H. pylori from humans. Current therapies based on proton pump inhibitors and antimicrobials are effective but fail at times due to poor compliance and the development of antibiotic resistance by H. pylori . Therefore, an effective vaccine is clearly needed. This chapter reviews the association of H. pylori with human disease, the best-characterized virulence factors, the host response, and vaccine development efforts to date. Although major advances have been made in our understanding of how H. pylori interacts with humans, this bacterium keeps on surprising investigators and there are still many unanswered questions that need to be addressed in order to develop an effective vaccine.