Systemic and mucosal immune responses in mice orally immunized with avirulent Salmonella typhimurium expressing a cloned Porphyromonas gingivalis hemagglutinin.

Porphyromonas gingivalis produces a variety of virulence factors that may have a function in the periodontal disease process. Determination of the role of these various factors in pathogenesis and identification of a means for protecting the host from the destructive effects of this organism are areas of vigorous investigation. In this study we demonstrate the potential of avirulent Salmonella typhimurium strains to stimulate a specific systemic and mucosal immune response to a cloned P. gingivalis hemagglutinin (HagB). An avirulent strain of S. typhimurium, chi 4072, expressing the hagB gene of P. gingivalis 381 on the plasmid pDMD1 was intragastrically administered to BALB/c mice. These mice mounted a serum immunoglobulin G (IgG) and IgA primary response against the hagB gene product and a mucosal immune response as measured by evaluation of saliva. IgA antibodies were also detected in bile. These results demonstrate the feasibility of using attenuated S. typhimurium strains as carriers of P. gingivalis virulence factors for subsequent evaluation of the systemic and mucosal immune response against these antigens. This system will provide a means for evaluating the virulence factors of P. gingivalis for their suitability in the construction of potential vaccines.