Abstract
Our previous study have demonstrated that nasal administration of heat-killed recombinant Lactobacillus casei expressing 40-kDa outer membrane protein of Porphyromonas gingivalis (L. casei/40k-OMP) elicited high titers of 40k-OMP-specific serum IgG, IgA and salivary IgA antibody responses which provided significant protection against oral infection with P. gingivalis. In this study, we further elucidated nature of 40k-OMP-specific CD4+ T helper (Th) cells in those immunized mice. When CD4+ T cells that were isolated from spleen or cervical lymph nodes of mice immunized with heat-killed L. casei/40k-OMP were restimulated with 40k-OMP in vitro, significant levels of proliferation occurred. Furthermore, heat-killed L. casei/40k-OMP induced 40k-OMP-specific Th1 cells secreting IFN-γ as well as Th2 cells producing IL-4 and IL-5, with IgG1 and IgG2a antibody responses. These results suggest that nasal administration of heat-killed L. casei/40k-OMP elicits both Th1 and Th2 cytokines for induction of antigen-specific antibody responses in oral mucosal as well as systemic compartments and that provide further evidence of the potential of heat-killed recombinant L. casei vaccine for induction of protective immune responses against P. gingivalis infection.
