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Intracellular niches for extracellular bacteria: lessons from Helicobacter pylori
1Department of Medicine, University of Iowa and the Veterans Administration Medical Center, Iowa City 52242, USA. lee-ann-allen@uiowa.edu
Abstract:
Helicobacter pylori colonizes the gastric epithelium of humans and plays a causative role in peptic ulcer disease and perhaps gastric cancer. H. pylori proliferates in the mucus layer over the epithelium and is not cleared by the host immune response. Although the mucus layer is the major reservoir of H. pylori in vivo, a growing body of evidence suggests that H. pylori can persist in multiple intracellular locales. Clinical isolates of H. pylori invade epithelial monolayers at least as well as Shigella. The intracellular organisms are cytotoxic, and bacterial microcolonies form on the exposed basement membrane. Both mononuclear phagocytes and neutrophils phagocytose unopsonized H. pylori. However, the internalized organisms are not killed efficiently and our recent data suggest that H. pylori disrupts phagosome maturation. Collectively, the data support the hypothesis that intracellular H. pylori represent a reservoir of organisms that contributes to bacterial persistence, host tissue damage, and treatment failure.
Insights
Helicobacter pylori persists inside human cells, forming intracellular reservoirs. This intracellular presence contributes to persistent infections, tissue damage, and treatment failure in peptic ulcer disease.
Area of Science:
- Microbiology
- Cell Biology
- Gastroenterology
Background:
- Helicobacter pylori is a bacterium that colonizes the human stomach.
- It is linked to peptic ulcer disease and gastric cancer.
- H. pylori resides in the mucus layer but can also invade host cells.
Purpose of the Study:
- To investigate the role of intracellular H. pylori.
- To understand how H. pylori persists within host cells.
- To explore the contribution of intracellular bacteria to disease pathogenesis.
Main Methods:
- Invasion assays using epithelial monolayers.
- Assessment of intracellular bacterial cytotoxicity.
- Phagocytosis studies with immune cells (mononuclear phagocytes and neutrophils).
- Analysis of phagosome maturation in infected cells.
Main Results:
- H. pylori invades epithelial cells effectively.
- Intracellular bacteria are cytotoxic and form microcolonies.
- Immune cells phagocytose H. pylori but do not kill it efficiently.
- H. pylori disrupts phagosome maturation within host cells.
Conclusions:
- Intracellular H. pylori acts as a persistent reservoir.
- This intracellular persistence contributes to host tissue damage.
- Intracellular H. pylori may lead to treatment failure in infections.