Development of disease-specific diagnosis and immunotherapy for Sjogren's syndrome

以前我们已经确定了120 kD的α-胞衬蛋白作为人类原发性干燥综合征（SS）发病机制中的常见自身抗原，但免疫显性表位识别的机制仍不清楚。干燥综合征（SS）是一种由T细胞介导的自身免疫性疾病，主要表现为口眼干燥（干燥综合征）。将编码人α-胞衬蛋白（JS-1）的cDNA插入pGEX-2 T的EcoR 1位点，构建了重组α-胞衬蛋白（JS-1）。建立了识别人工合成的α-胞衬蛋白自肽N端部分的自身反应性T细胞克隆，产生Th 1细胞因子，并显示细胞毒活性。表位肽的丙氨酸扫描诱变表明表位内MHC接触点的两个氨基酸取代足以改变肽结合和MHC限制。此外，很明显，只有两个TCR接触点对于抗原特异性T细胞应答的起始是必需的。基于类似肽的疫苗接种通过下调Th 1应答和自身抗体产生来预防疾病。通过基于类似肽的免疫疗法阻断致病性T细胞活性对于T细胞介导的自身免疫性疾病如人SS是高度有效的。

Previously we have identified a 120 kD α-fodrin as a common autoantigen in the pathogenesis of primary Sjogren's syndrome (SS) in humans, but the mechanisms underlying the immunodominant epitope recognition remain unclear. SS in human is a T cell-mediated autoimmune disease in the salivary and lacrimal glands, leading to clinical symptoms of dryness of the mouth and eyes (sicca syndrome). Recombinant α-fodrin protein, the cDNA encoding human α-fodrin (JS-1) was constructed by inserting cDNA into EcoR1 site of pGEX-2T, To establish disease-specific diagnostic system, approximately 200 sera from patients with SS were tested with ELISA assay using JS-1 recombinant protein. Autoreactive T cell clones that recognize synthetic N-terminal portion of α-fodrin autopeptide were established, which produced Th1 cytokines, and showed cytotoxic activities. Alanine scanning mutagenesis of the epitope peptide indicate that the two amino acid substitutions of MHC contact points within epitope are sufficient to alter peptide binding and MHC restriction. Moreover, it is evident that only two TCR contact points are essential for initiation of antigen-specific T cell response. An analogue peptide-based vaccination prevented the disease through downregulation of Th1 responses and autoantibody production. Blockade of pathogenic T cell activity through an analogue peptide-based immunotherapy is highly effective for T cell-mediated autoimmune disease such as human SS.