Genetic variation in the recognition of Porphyromonas gingivalis antigens in mice

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 microg 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 microg 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.