A potent protein vaccines OmpW induces strong protective immunity against Klebsiella pneumoniae in a mouse model.

Klebsiella pneumoniae causes severe respiratory-associated infections in healthy individuals, and widespread antibiotic resistance in K. pneumoniae poses a global health threat. Although great efforts have been taken to develop effective vaccines against K. pneumoniae, there are no licensed vaccines against K. pneumoniae available up to date. In the current study, we designed a potent subunit vaccine OmpW, which was obtained from an outer membrane protein (OmpW) to maximize host responses in mice. Antibody-mediated responses and protective effects were determined to compare the immunogenicity of the OmpW subunit vaccine in the vaccinated mice. Immunization experiments showed that mice immunized with recombinant OmpW generated high IgG antibody production, which promoted macrophage opsonophagocytic activity and induced strong serum bactericidal activity. The residual bacterial burdens from the different organs were declined in the immunized mice compared with the control group. Notably, immunization with the OmpW subunit vaccine provided better protection against K. pneumoniae challenge in vaccinated mice. The passive transfer of antiserum from OmpW-immunized mice also provided protection against K. pneumoniae infection. This study constitutes an important step toward developing potent antibacterial vaccines against K. pneumoniae infections and prevents further dissemination of K. pneumoniae strains.