Immunogenicity and Protective Efficacy of Heat-Killed Recombinant Lactobacillus casei Expressing Outer Membrane Protein of Porphyromonas gingivalis

This study seeks to access the potential of a heat-killed recombinant Lactobacillus casei expressing 40-kDa outer membrane protein of Porphyromonas gingivalis (L. casei/40k-OMP) as a nasal vaccine against P. gingivalis infection. The 40-kDa outer membrane protein of P. gingivalis (40k-OMP) were expressed on the surface of L. casei using poly-γ-glutamate symthetase A (pgsA). Nasal immunization with heat-killed L. casei/40k-OMP induced significant 40k-OMP-specific serum IgG, IgA and saliva IgA antibody responses. Antibody-forming cell analysis revealed high numbers of 40k-OMP-specific IgA antibody-forming cells in the submandibular glands of mice given heat-killed L. casei/40k-OMP. Importantly, nasal administration of heat-killed L. casei/40k-OMP resulted in the significant reduction of alveolar bone loss caused by oral infection with P. gingivalis. Because L. casei is one of major probiotic bacterias, nasal administration of heat-killed L. casei/40k-OMP should be an effective and safe mucosal vaccine for humans against P. gingivalis infection and may be an important tool for prevention of chronic periodontitis.