When Helicobacter pylori invades and replicates in the cells.

Autophagosome formation is induced by Helicobacter pylori infection and these autophagic vesicles are adopted for replication of H. pylori and subsequent eradication of the invading H. pylori in macrophages. Some Taiwanese clinical isolates of H. pylori can replicate in certain macrophage cell lines. After entry, there was a 5-10 fold increment of recultivable H. pylori from the infected permissible cells at 12 h post infection. The dividing H. pylori are observed to reside in double-layered autophagosomes. Therefore, H. pylori can be considered as a kind of intracellular microorganism. The autophagy induction by H. pylori is not only found in macrophages, but also in dendritic cells and gastric epithelial cells. This new finding has several implications for the life cycle of H. pylori in the host. The bacterium's residence inside infected cells will increase its resistance to antimicrobial treatment, avoid neutralization by anti-H. pylori antibodies, impair antigen presentation, and alter the cellular immune response. The replication of H. pylori in autophagic vesicles, and the consequences of this provide an important hint as to why this microorganism causes such a broad spectrum of diseases.