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Cytolethal distending toxin sequence and activity in the enterohepatic pathogen Helicobacter hepaticus
V B Young1, K A Knox, D B Schauer
1Division of Bioengineering and Environmental Health, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Abstract:
Little is known about the molecular pathogenesis of hepatitis and enterocolitis caused by enterohepatic Helicobacter species. Sonicates of the murine pathogen Helicobacter hepaticus were found to cause progressive cell distension, accumulation of filamentous actin, and G(2)/M cell cycle arrest in HeLa cell monolayers. The genes encoding this cytotoxic activity were cloned from H. hepaticus. Three open reading frames with closest homology to cdtA, cdtB, and cdtC from Campylobacter jejuni were identified. Sonicates of a laboratory strain of Escherichia coli carrying the cloned cdtABC gene cluster from H. hepaticus reproduced the cytotoxic activities seen with sonicates of H. hepaticus. Cytolethal distending toxin activity is a potential virulence determinant of H. hepaticus that may play a role in the pathogenesis of Helicobacter-associated hepatitis and enterocolitis.
Insights
Enterohepatic Helicobacter species cause liver and intestinal inflammation. Researchers identified the cytolethal distending toxin (CDT) genes from Helicobacter hepaticus, revealing a key factor in pathogenesis.
Area of Science:
- Microbiology
- Molecular Pathogenesis
- Hepatology
Background:
- The molecular mechanisms underlying hepatitis and enterocolitis induced by enterohepatic Helicobacter species remain largely uncharacterized.
- Helicobacter hepaticus is a murine pathogen implicated in liver and intestinal diseases.
Purpose of the Study:
- To investigate the molecular pathogenesis of enterohepatic Helicobacter-associated liver and intestinal inflammation.
- To identify the genes responsible for the cytotoxic effects of Helicobacter hepaticus.
Main Methods:
- Analysis of sonicates from Helicobacter hepaticus in HeLa cell monolayers.
- Cloning of genes encoding cytotoxic activity from H. hepaticus.
- Expression of cloned genes in Escherichia coli to assess cytotoxic effects.
Main Results:
- Helicobacter hepaticus sonicates induced cell distension, actin accumulation, and G(2)/M cell cycle arrest in HeLa cells.
- Three genes homologous to Campylobacter jejuni cdtA, cdtB, and cdtC were identified in H. hepaticus.
- Expression of the cloned H. hepaticus cdtABC genes in E. coli replicated the observed cytotoxic activities.
Conclusions:
- Cytolethal distending toxin (CDT) activity is a significant virulence factor for Helicobacter hepaticus.
- CDT produced by H. hepaticus likely contributes to the pathogenesis of hepatitis and enterocolitis.
- Understanding CDT's role provides insights into enterohepatic Helicobacter-associated diseases.