The effect of immunization on the response to P. gingivalis infection in mice is adjuvant-dependent.

Aim: Studies on vaccines against the periodontal pathogen Porphyromonas gingivalis have produced conflicting results, but no consideration has been given to the role of different adjuvants in these vaccines. We have previously shown that an intra-chamber challenge with heat-killed P. gingivalis was modified by immunization with different adjuvants. This study tested the hypothesis that different adjuvants in P. gingivalis vaccines would differentially modify the host response to a live P. gingivalis infection. Results: Using P. gingivalis-infected subcutaneous chambers in mice, we show that vaccination with P. gingivalis in alum attenuated the pro-inflammatory cytokine levels at the site of infection, while the vaccine containing incomplete Freund's adjuvant did the opposite. Although both vaccines induced a similar humoral IgG response, P. gingivalis-induced abscesses were significantly smaller in the alum-adjuvant group. Conclusions: The results suggest that the immune response and the resultant protection to a P. gingivalis infection, in P. gingivalis-vaccinated mice, are adjuvant-dependent.