Attenuated Salmonella enterica serovar Typhi expressing urease effectively immunizes mice against Helicobacter pylori challenge as part of a heterologous mucosal priming-parenteral boosting vaccination regimen.

Recombinant vaccine strains of Salmonella enterica serovar Typhi capable of expressing Helicobacter pylori urease were generated by transforming strains CVD908 and CVD908-htrA with a plasmid harboring the ureAB genes under the control of an in vivo-inducible promoter. The plasmid did not interfere with the ability of either strain to replicate and persist in human monocytic cells or with their transient colonization of mouse lungs. When administered to mice intranasally, both recombinant strains elicited antiurease immune responses skewed towards a Th1 phenotype.