Immune response to co-infection of periodontopathogens in a mouse model

Objectives: were to determine the immune responses to a co-infection of periodontopathic bacteria using a mouse abscess model. Methods: Non-immunised BALB/c mice were divided into seven groups of 3-4 mice were challenged with Fusobacterium nucleatum (Fn) ATCC 25586, Tannerella forsythensis (Tf) ATCC 43037 and Porphyromonas gingivalis (Pg) ATCC 33277 as follows: Group 1 mice received Pg and Fn; Group 2 mice, Tf and Fn; Group 3 mice, Pg and Tf; Group 4 mice, Pg only; Group 5 mice, Fn;Group 6 mice, Tf; and Group 7 mice, saline. On days 1, 4, 7, and 14 mice were euthanized, lesions excised, serum taken, weight of mice and lesion sizes measured. Sections from the lesions were stained by an avidin-biotin immunoperoxidase method for CD4 T-cells, CD8 T-cells, CD19 B-cells and Mac3 macrophages. Serum specific antibodies also determined to each bacterium using an ELISA. Results: lesions developed at the injection site in all groups except the saline group. Lesion sizes peaked at day 4 with Pg/Tf and solely with Pg. While mice injected with combinations of Pg/Fn and Fn/Tf peaked at day 7, as well with solely Fn and Tf. Mice challenged with Pg/Fn the lesions were still visible at day 14 while the other groups had healed or healing. All mice lost weight at 12hrs with Fn mice losing the most weight. Mice Fn, Pg/Fn, Pg/Fn and Pg gaining weight on day 7 with all mice losing weight on day 14. Mice infected with Pg/Fn showed that the CD4+ T-cells and Mac3+ cells had an increased infiltration into the lesion when compared to mice injected singly with Pg or Fn. Mice infected with Pg/Tf also showed a synergistic effect in CD4+ T-cells compared with mice injected with only Pg or Tf. Conclusions: The results showed a synergistic effect from combinations of bacteria.