Methods: PG1841 was identified as an immunodominant Pg antigen by T cell expression cloning. Recombinant PG1841 was expressed and purified using standard methodologies. C57Bl/6 mice were infected with Pg W83 subcutaneously to determine if PG1841 is expressed and is immunogenic in vivo. To determine effects on inflammatory bone resorption, mice were pre-immunized with rPG1841 under Th1 (alum + CpG) or Th2 (alum alone) biasing conditions. Th biasing was confirmed by serum antibody responses to PG1841 (IgG1/IgG2a) and by lymphoid cell expression of IL-4/IFN&Gamma. Effects on inflammatory bone resorption were evaluated using a periapical lesion model. Bone loss was measured by micro-computed tomography.
Results: Subcutaneous infection of mice with Pg W83 induced a strong Th1 biased response to PG1841, as indicated by specific serum antibody (IgG2a > IgG1). Mice immunized with rPG1841 under Th1 and Th2 inducing regimens showed the expected systemic immune response biasing. rPG1841 immunized Th1-biased mice challenged with Pg into dental pulp tissue developed severe periapical bone loss. In contrast, rPG1841 Th2-biased mice had no exacerbation of resorption when compared to adjuvant immunized control animals.
Conclusion: We conclude that selected immunodominant antigens of Pg that normally induce a Th1 response may reduce inflammatory bone loss if presented in a Th2 biasing adjuvant formulation. This approach may be useful for the development of vaccines or immunotherapeutics to prevent inflammatory bone loss caused by Pg.
Supported by NIDCR grants DE-09018 and T32-DE-007327.