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Oral immunization with a dam mutant of Yersinia pseudotuberculosis protects against plague

Victoria L Taylor1, Richard W Titball2,1, Petra C F Oyston1

  • 1Defence Science and Technology Laboratory, Porton Down, Salisbury, Wiltshire SP4 0JQ, UK.

Microbiology (Reading, England)
|June 9, 2005
PubMed

Insights

Inactivating the DNA adenine methylase (dam) gene in Yersinia pseudotuberculosis significantly reduced its virulence and protected mice against lethal infections. This dam mutant shows promise as a live vaccine candidate.

Area of Science:

  • Microbiology
  • Genetics
  • Immunology

Background:

  • DNA adenine methylase (dam) gene inactivation attenuates or is lethal in bacterial pathogens.
  • Yersinia pseudotuberculosis virulence is influenced by DNA methylation patterns.

Purpose of the Study:

  • To investigate the role of the dam methylase gene in Yersinia pseudotuberculosis strain IP32953.
  • To evaluate the virulence and immunogenicity of a dam-deficient Yersinia pseudotuberculosis mutant.

Main Methods:

  • Inactivation of the dam methylase gene in Yersinia pseudotuberculosis IP32953.
  • DNA methylation analysis using MboI digestion.
  • Gene expression profiling via DNA microarray.
  • Virulence assessment in BALB/c mice through oral and intravenous inoculation.
  • Vaccine efficacy testing against Yersinia pestis and Y. pseudotuberculosis challenges.

Main Results:

  • The dam mutant exhibited altered DNA methylation patterns, confirmed by MboI digestion.
  • The dam mutant showed increased sensitivity to bile salts.
  • DNA microarray analysis revealed changes in gene expression due to dam inactivation.
  • The median lethal dose (MLD) of the dam mutant in mice was at least 10(6)-fold higher than the wild-type.
  • Mice inoculated with the dam mutant were protected against subsequent challenges with Yersinia pestis and Y. pseudotuberculosis.

Conclusions:

  • Dam methylase is crucial for the virulence of Yersinia pseudotuberculosis IP32953.
  • The dam-deficient mutant is significantly attenuated and immunogenic.
  • The Yersinia pseudotuberculosis dam mutant demonstrates potential as a live vaccine candidate against plague and pseudotuberculosis.

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