Genetic variation in the recognition of Porphyromonas gingivalis antigens in mice

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Abstract
T‐cell cytokine profiles, anti–Porphyromonas gingivalis antibodies and Western blot analysis of antibody responses were examined in BALB/c, CBA/CaH, C57BL6 and DBA/2J mice immunized intraperitoneally with different doses of P. gingivalis outer membrane antigens. Splenic CD4 and CD8 cells were examined for intracytoplasmic interleukin (IL)‐4, interferon (IFN)‐gamma and IL‐10 by FACS analysis and levels of anti–P. gingivalis antibodies in the serum samples determined by enzyme‐linked immunosorbent assay. Western blot analysis was performed on the sera from mice immunized with 100 μg of P. gingivalis antigens. The four strains of mice demonstrated varying degrees of T‐cell immunity, although the T‐cell cytokine profiles exhibited by each strain were not affected by different immunizing doses. While BALB/c and DBA/2J mice exhibited responses that peaked at immunizing doses of 100–200 μg of P. gingivalis antigens, CBA/CaH and C57BL6 demonstrated weak T‐cell responsiveness compared with control mice. Like the T‐cell responses, serum antibody levels were not dose dependent. DBA/2J exhibited the lowest levels of anti–P. gingivalis antibodies followed by BALB/c with CBA/CaH and C57BL6 mice demonstrating the highest levels. Western blot analysis showed that there were differences in reactivity between the strains to a group of 13 antigens ranging in molecular weight from 15 to 43 kDa. Antibody responses to a number of these bands in BALB/c mice were of low density, whereas CBA/CaH and C57BL6 mice demonstrated high‐density bands and DBA/2J mice showed medium to high responses. In conclusion, different immunizing doses of P. gingivalis outer membrane antigens had little effect on the T‐cell cytokine responses and serum anti–P. gingivalis antibody levels. Western blot analysis, however, indicated that the four strains of mice exhibited different reactivity to some lower‐molecular‐weight antigens. Future studies are required to determine the significance of these differences, which may affect the outcome of P. gingivalis infection.