Helicobacter (H.) suis is a porcine gastric pathogen, which has also been associated with human gastric disorders. Previous studies in mice showed that an H. suis infection does not result in protective immunity, whereas immunization with an H. suis whole-cell lysate (lysate) protected against a subsequent experimental infection. Therefore, in a first study two-dimensional gel electrophoresis of H. suis proteins was performed followed by immunoblotting with pooled sera from H. suis- infected mice or mice immunized with lysate. Little reactivity against H. suis proteins was observed in post-infection sera. Sera from lysate immunized mice, however, showed immunoreactivity against a total of 19 protein spots which were identified using ESI-Q-TOF. The H. suis urease subunit B (UreB) showed most pronounced reactivity against sera from immunized mice and was not detected by sera from infected mice. Other identified proteins included H. suis chaperonin GroEL, urease subunit A, flagellin A and elongation factor G. In a second study, the protective efficacy against an H. suis infection of two subunit vaccines was evaluated and compared with that of H. suis lysate in a standardized mouse model. Subunit vaccines consisted of either the immunoreactive H. suis UreB or the non-immunoreactive H. suis neutrophil-activating protein A (NapA), both recombinantly expressed in Escherichia coli (rUreB and rNapA, respectively). Intranasal immunization of mice with rUreB induced a specific serum anti-rUreB IgG response and a significant (p<0.001) reduction of H. suis colonization compared to non-vaccinated H. suis-infected positive controls. rNapA had no significant (p=0.14) protective effect, although it induced anti-rNapA IgG. Immunization with whole-cell lysate was most effective against a H. suis challenge (p<0.001). Increased specific serum IgG and gastric IFN-γ mRNA expression levels were correlated with decreased gastric bacterial load. In conclusion, rUreB is a potential candidate for inclusion in vaccines against H. suis infections.