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Heterogeneity of Helicobacter pylori cag genotypes in experimentally infected mice
1Division of Gastroenterology and Digestive Endoscopy, CRO, Via Pedemontana Occidentale 12, 33081 Aviano, Italy. msozzi@cro.it
Abstract:
Our aim was to assess whether the Helicobacter pylori population recovered from experimentally infected mice show heterogeneity in cag genotypes. Wild-type FVB/N mice were challenged with strain Hp1 and sacrificed 8 weeks later. Direct PCR on gastric tissue was performed using primers for glmM and cagA, and for these two genes and for cagE and virB11 using DNA from the infecting and the emerging strains. The gastric tissues of two of five mice were PCR+ for glmM but not cagA. For the infecting strain, the PCRs for all four genes studied were strongly positive, but the sweeps from the emerging strains from both mice gave weaker signals for cagA and cagE. Examination of single colonies showed reduced or absent signals for cagA and cagE in relation to glmM and virB11. Serial dilution PCR of sweep isolates from the mice showed a 10- to 100-fold decrease in cagA signal compared to the infecting strain. The decrease of cagA and cagE, but not virB11, amplification and lack of cagA hybridization in Southern blots indicates a selective loss of the right half of the cag island during murine infection. This phenomenon is consistent with host-induced adaptive changes of cag genotype in the population of colonizing H. pylori cells.
Insights
Helicobacter pylori infecting mice showed genetic changes, losing parts of its cag island. This suggests H. pylori adapts to its host environment by altering its virulence genes.
Area of Science:
- Microbiology
- Genetics
- Infectious Diseases
Background:
- Helicobacter pylori is a bacterium that colonizes the human stomach.
- The cag pathogenicity island (cag) is a key virulence factor in H. pylori.
- Understanding H. pylori genetic diversity during infection is crucial for comprehending its pathogenesis.
Purpose of the Study:
- To investigate the heterogeneity of cag genotypes in Helicobacter pylori populations during experimental murine infection.
- To determine if H. pylori undergoes genetic modifications in its cag island within a host environment.
Main Methods:
- Experimental infection of FVB/N mice with H. pylori strain Hp1.
- DNA extraction from gastric tissues and infecting/emerging bacterial strains.
- Polymerase Chain Reaction (PCR) targeting glmM, cagA, cagE, and virB11 genes.
- Southern blot analysis for cagA hybridization.
- Serial dilution PCR to quantify gene signal reduction.
Main Results:
- Gastric tissues from infected mice showed reduced or absent signals for cagA and cagE compared to glmM and virB11.
- PCR analysis revealed a 10- to 100-fold decrease in cagA signal in emerging strains.
- Southern blots indicated a selective loss of the right half of the cag island in H. pylori populations recovered from mice.
Conclusions:
- H. pylori populations can undergo selective loss of parts of the cag island during murine infection.
- These genetic alterations suggest host-induced adaptive changes in H. pylori virulence gene expression.
- The findings provide insights into the dynamic genetic adaptation of H. pylori within a host.