Collagen-induced arthritis (CIA) is an experimental autoimmune arthritis induced by immunization of genetically susceptible strains of mice with type II collagen (CII). It shares several important features with human rheumatoid arthritis. It is characterized by an immune response to CII, including the activation of T cells, and production of arthritogenic autoantibodies that culminate in the induction of synovitis, and the release of degradative enzymes that destroy the tissues. Previous work in our laboratory has identified a region of type II collagen, CII 260-270, as the immunodominant T cell epitope in the immune response to CII of I- A(q)-bearing mice. Activation of T cells requires first a formation of complexes between antigenic peptides and major histocompatibility complex (MHC) molecules. These complexes then are recognized by the T cell receptors (TcR) of antigen-specific T cells. The formation of this tri- molecular complex is an essential initial event in the activation of T cells and subsequent production of arthritogenic antibodies and the development of arthritis. Therefore, developing a means of disrupting the activation of T cells within the context of the trimolecular complex could lead to important therapeutic strategies for suppression of arthritis. In order to produce analog peptides with the potential of disrupting I-A(q)- restricted antigen presentation, synthetic analog peptides were developed that contained amino acid substitutions at selected residues within CII 260-270. One of these analog peptides, A9, (CII 245-270 [s260, 261, 263]), was found to be capable of inhibiting T cell responses to CII in vitro. When DBA/1 mice, (H-2(q)), were administered this analog peptide, the incidence and severity of arthritis were significantly reduced along with the humoral immune responses to CII. Therefore, we plan to identify the amino acid residues of CII 260-270 which interact with I-A(q) and residues which interact with TcR in order to determine the role each amino acid residue plays in T cell function and to design analog peptides which are most effective in disrupting T cell function. The potential mechanism for the effectiveness of these inhibitory peptides will be investigated by i) Analyzing the lymphokine secretion profiles, (TH1 vs. TH2), generated both in vitro and in vivo when CII 260-270-reactive T cells are exposed to wild type peptide, A9 analog, or other inhibitory peptides, and ii) Characterizing the mechanism by which A9 or other inhibitory analog peptides effect signaling through the T cell receptor. Specific attention will be focused on tyrosine phosphorylation of TcR/CD3-associated proteins and turnover of phosphatidyl inositol. Insights gained from these studies will provide important lessons for approaches to designing analog peptides that may be useful in the therapy of autoimmune arthritis in humans.
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