Development of effective immunization by DNA vaccine against iron-acquisition protein of periodontopathic bacteria

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Lysine-specific cysteine proteinase (KGP) of Porphyromonas gingivalis, which is a prominent periodontopathic bacterium, is considered to play an important role in its pathogenesis, since it possesses protease activity as well as hemoglobin-binding activity. Previously, we reported that immunization of mice by injection of DNA vaccine against KGP into the muscle induced specific anti-KGP IgG antibodies in serum and that the DNA vaccine prevented inflammatory responses and prolonged the survival rate of the immunized mice against P gingivalis infection. The aim of this study was to investigate whether humoral immunity and cell-mediated immunity could be introduced when mice were immunized by injection of DNA vaccine into muscle or by oral administration of DNA vaccine-harboring avirulent bacterium that parasitizes in host cells; consequently to develop effective immunization. We constructed kgp-DNA vaccine (pCMV/kgp) for oral administration and transformed the plasmid into Salmonella typ … More himuriuin SL7207, which is an avirulent bacterium and was used as a vehicle for the DNA vaccine. Mice were immunized orally with the bacterium harboring the plasmid encoding kgp-DNA vaccine weekly for a total of four inoculations. Following the immunization, it was shown that specific anti-KGP IgG antibodies in serum were clearly induced by ELISA. Although induction of anti-KGP IgG antibodies in serum was observed when mice were immunized by injection of the DNA vaccine into muscle, the titers were lower than those when mice were orally immunized. Moreover, anti-KGP IgA antibodies in saliva were also introduced by immunization by oral administration of the DNA vaccine, while those were not observed when mice were immunized by intramuscular injection. We are now working on development of effective immunization methods and ion introduction of cell-mediated immunity and mucosal immunity. The present study indicates that immunization of kgp-DNA vaccine by oral administration may be a useful method to prevent periodontitis. Less