Patent Evaluation: Virulence-Attenuated Vaccines

Summary

Novelty: Vaccines (preferably live), involving a bacterial cell, preferably a Salmonella cell, which are virulence-attenuated by mutations in a two-component regulatory system, are claimed. The Salmonella cells are useful as sources of immunological protection against typhoid fever and related diseases.

Biology: In preferred embodiments the bacterium is Salmonella eg. S. typhi, S. enteritidis typhimurium or S. choleraesuis and the two-component system is the phoP regulatory region which controls the expression of pag and prg genes. Virulence and protective efficacy of the Salmonella strains, administered orally in mice, show that the vaccines are highly attenuated for virulence but retain immunogenicity, thus they are both safe and effective.