ANALOG PEPTIDES IN COLLAGEN-INDUCED ARTHRITIS

胶原蛋白诱导性关节炎(CIA)是用II型胶原(CII)免疫易感品系小鼠而诱导的自身免疫性关节炎的实验模型。我们最近利用表达与类风湿性关节炎(RA)易感性相关的HLAII类分子的转基因(TG)小鼠的研究表明，DR1(DRB1*0101)和DR4(DRB1*0401)可以结合和呈递来自人(H)CII的多肽，并且携带这些转基因DR分子的小鼠对CIA易感。CII，A12，CII 256-276(F263-&gt；N，E266-&gt；D)的类似肽可以下调对HCII和关节炎的免疫反应，当它与HCII免疫时联合给药。与用野生型CII多肽(CII 256-276)培养的细胞相比，来自DR TG小鼠的人CII致敏的脾和淋巴结细胞在Al2培养时产生更多的IL-4和IL-10。这些观察表明，A12对这些DR TG小鼠对CII和CIA的免疫反应的抑制作用是通过细胞因子谱的改变而介导的，从Th1到Th2。然而，这种转变的机制(S)尚不清楚。与野生型CII肽相比，Al2含有两个氨基酸替换。替换有两种类型，a)参与与DR分子结合的多肽的残基263，以及b)与TCR相互作用的残基266。在本应用中要检验的假设是，A12对CIA的影响是通过对以Th2为主的特异性免疫反应的极化来介导的，这种极化是由于DR与多肽之间的亲和力或DR/多肽与TCR相互作用的变化导致T细胞信号的改变，从而产生细胞因子。因此，我们计划：1)确定模拟多肽Al2的结构特征，它介导了DR TG小鼠对CiIL和CIA免疫反应的调节；2)确定编码三螺旋CII分子中的Al2取代是否增加了抑制CIA自身免疫反应的有效性；3)确定A12给药产生的CIA抑制是依赖于IL-10还是IL-4分泌；以及4)通过分析T细胞激活所涉及的信号通路，确定Al2改变T细胞功能的机制。从这些研究中获得的信息将为设计新的治疗方法提供重要的见解，这些方法可能被证明对人类自身免疫性关节炎的治疗有益。

Collagen-induced arthritis (CIA) is an experimental model of autoimmune arthritis induced by immunization of susceptible strains of mice with type II collagen (CII). Our recent studies using HLA-DR transgenic (Tg) mice expressing HLA class II molecules associated with susceptibility to rheumatoid arthritis (RA) reveal that DR1 (DRB1*0101) and DR4 (DRB1*0401) can bind and present peptides derived from human (h) CII, and that mice bearing these transgenic DR molecules are susceptible to CIA. The immune response to hCII and arthritis can be down regulated by an analog peptide of CII, A12, CII 256-276 (F263->N, E266->D), when it is co-administered at the time of immunization with hCII. Human CII- sensitized spleen and lymph node cells from DR Tg mice produce increased amounts of IL-4 and IL-10 when cultured with Al2 in comparison to cells cultured with the wild-type CII peptide (CII 256-276). These observations suggest that the suppressive effect of A12 on immune response to CII and CIA in these DR Tg mice is mediated by a shift in the cytokine profile, from that of a Thl to a Th2. However, the mechanism(s) whereby the shift is brought about is not known. Al2 contains two amino acid substitutions as compared to the wild-type CII peptide. The substitutions are of two types, a) residue 263 that participates in peptide binding to the DR molecule, and b) residue 266 that interacts with the TCR. The hypothesis to be tested in this application is that the A12 effect on CIA is mediated through polarization of the specific immune response to a predominant Th2 profile, and that this polarization is caused by changes in the affinity between either DR and peptide or DR/peptide interaction with the TCR leading to altered T cell signaling and, consequently, the production of cytokines. We, therefore, plan to: 1) Identify the structural characteristics of the analog peptide Al2 that mediate its modulation of the immune response to CIIl and CIA in DR Tg mice; 2) Determine whether encoding the Al2 substitutions within the triple helical CII molecule increases the efficacy in inhibiting the autoimmune response in CIA; 3) Determine whether the suppression of CIA produced by A12 administration is dependent on IL-l0 or IL-4 secretion; and 4) Determine the mechanism by which Al2 alters T cell function by analyzing signaling pathways involved in T cell activation. Information gained from these studies will provide important insight for the design of novel therapeutic approaches that may prove beneficial in the treatment of autoimmune arthritis in humans.