Effects of immunization with B. macacae on induced periodontitis--preliminary findings

This preliminary study examined the effects of immunization with Bacteroides macacae, the monkey equivalent of the human species of B. gingivalis on ligature-induced periodontitis. During a 12 week immunization period, 8 out of the 12 Macacae fasicularis monkeys were immunized weekly with B. macacae washed cells and 4 were sham-immunized with saline. At the same time, all were scaled and pumiced weekly to establish gingival health. Following this period, the mandibular first molars were ligated in 8 out of the 12 monkeys to induce periodontitis. The immunized, ligated experimental group, the ligated, sham-immunized control group, and the immunized, non-ligated control group were then followed for a 6 months ligation period while plaque was allowed to accumulate. Gingival indices, attachment levels, pocket depths, plaque indices, radiographs, serum and crevicular fluid antibodies and subgingival bacteria were assessed. Immunization led to elevated antibody levels to B. macacae while ligation increased plaque, gingival inflammation, and bone loss. Following the 6 month ligation period, B. macacae comprised 1.7% of the cultivable flora in the immunized, non-ligated monkeys, 2.1% in the immunized, ligated monkeys, and 5.6% in the sham-immunized, ligated monkeys. Similar differences between the immunized, ligated and and the sham-immunized, ligated groups were not seen for B. intermedius, nor B. melaninogenicus. These results suggest a heightened humoral response to B. gingivalis reduces subgingival re-colonization by this organism and modulates the course of ligature-induced periodontitis.