T CELL RESPONSE TO A PERIODONTAL PATHOGEN

University Of Texas Hlth Sci Ctr San Ant, San Antonio TX

Investigators

Abstract

We have focused on the periodontal pathogen, Actinobacillus actinomycetemcomitans (Aa). Individuals infected with this bacterium generate a specific humoral immune responses; some of the antigens recognized by serum antibodies have already been identified. On the other hand, the T cell epitopes on Aa have not yet been defined. Towards this end, we have undertaken an innovative, T cell hybridoma-based approach in order to dissect the T cell responses to Aa. In preliminary mice were orally inoculated with live bacteria and a panel of T cell hybridomas was generated. To our surprise, approximately 50% of the T cells reactive with Aa were specific for leukotoxin, a virulence factor produced by this oral pathogen. In order to characterize the immune response to Aa further, we now propose to: Aim 1. Clone genes that encode other T cell epitopes by direct screening of an Aa genomic library. The identities of the Aa proteins recognized by the T cell hybridomas will be determined and recombinant peptides generated for use in Aims 2 and 3. Aim 2: Characterize the nature of the immune response in vivo to individual Aa antigens. Mice will be: a) immunized with purified recombinant peptides, b) immunized with bacteria, or c) orally inoculated with viable Aa. Immune activation to individual T cell epitopes will then be assessed by studies of antibody production, T cell activation and cytokine production (Th1 versus Th2), and protection in a murine inflammation model. Aim 3. Determine whether the predominant T cell antigens in mice are similarly stimulatory in Aa-infected patients. Specifically, peripheral blood lymphocytes from EOP patients will be cultured in vitro with individual recombinant Aa peptides and T cell stimulation assessed by cytokine production and by spectrotyping. These aims will: i) provide the first evidence regarding T cell antigenic epitopes on this pathogen and ii) assess the relationship between T cell epitopes that are immunodominant in mice and those seen in humans. The long term goal is to develop and validate a model for evaluating host-parasite interactions, vaccine potency, and immune protection for periodontal diseases.