Induction of mucosal immune responses by DNA vaccine encoding Porphyromonas gingivalis fimbriae

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For the development of vaccines against oral and pharyngeal pathogens invading the mucosal epithelia, both secretory and serum IgA/IgG antibodies and cytotoxic T lymphocytes have been induced. We employed a novel approach, targeted salivary gland (TSG) immunization, using a plasmid pcDNA3/fimA coding for Porphyromonas gingivalis fimbriae. Expression of subunit protein, fimbrillin, was observed in eukaryotic cells growing in vitro following transfection, with pcDNA3/fimA. In this study, we obtained good humoral and cell-mediated immune responses in BALB/c mice by TSG administration using the above mentioned DNA vaccine. The production 6f fimbriae-specific IgA and IgG antibodies in saliva and serum IgG antibody was significantly stimulated by TSG immunization. Injection of DNA vaccine into salivary gland elicited high level production of antigen-specific IgG antibody, similar to that induced following intramuscular immunization. The major IgG subclass that recognized fimbriae was IgG2a in serum from pcDNA3/fimA immunized mice. When mononuclear cells from salivary glands^were analyzed by RT-PCR, higher levels of Th2 cytokine-specific mRNA were seen in the immunized group than non-immunized group. In addition, TSG DNA immunization resulted in the generation of antigen-specific CTL in spleen. These results indicate that TSG immunization with plasmid DNA may represent a genetic immunization strategy against infection by oral and pharyngeal pathogens that may invade local, mucosal surfaces.