XENOBIOTICS AND PRIMARY BILIARY CIRRHOSIS

描述(申请人提供)：尽管我们对自身抗原的性质和免疫反应的理解有了很大的进步，但原发性胆汁性肝硬变(PBC)的病因仍然是个谜。根据我们的试验数据，我们提出，暴露于外源物质会在遗传易感宿主中诱导PBC。这项工作是基于我们之前的观察结果，即B细胞的免疫优势自身表位以及自身反应的CD4和CD8细胞都局限于内部硫辛基结构域，强调该结构域是一个共同的半抗原。基于这个共同的硫辛基结构域，我们合成了一个合成结构库，旨在模拟异物修饰的硫辛基半抗原，然后将其连接到免疫优势的PDC-E2肽上。利用这些结构，我们确定PBC血清对某些半抗原修饰的多肽的反应明显高于对天然脂基化多肽的反应。此外，我们现在已经证明，一种这样的异源化合物与大载体(BSA)偶联，免疫兔和豚鼠，产生AMA反应，该反应与自身PDC-E2反应，与内部硫辛基结构域结合，并抑制PDC-E2功能，从而概括了人AMA的所有特征。我们认为，这一数据提供了确凿的证据，表明化学异源物质结合到与自身抗原有相同基序的蛋白质上，可能会打破耐受性，诱发AMA，并最终导致PBC。为了证明这一论点，我们需要对一系列化合物进行集中的定量结构活性关系分析(QSAR)，以最佳地定义与AMA反应最好的结构。此外，我们需要显著扩展我们在兔和豚鼠身上的研究，以确定免疫反应的频谱并诱导免疫病理学。我们认为，a)更多的QSAR研究可能有助于更好地了解打破耐受性的化合物与由这种成分引发的自身抗体之间的结构功能关系，从而可能缩小我们对真正引发PBC的化合物的选择；b)用外源载体免疫的动物可能需要很长时间才会发生疾病(需要慢性性)；以及c)无论这种化合物的鉴定如何，疾病的诱导和/或动力学可能需要额外的免疫侮辱，如不适当的或Th1细胞因子环境。这些研究对于确定免疫反应是否单独对疾病诱导至关重要，或者是否需要人类肝脏的独特环境也是至关重要的。

DESCRIPTION (provided by applicant): The etiology of primary biliary cirrhosis (PBC) remains enigmatic despite significant advances in our understanding of the nature of the autoantigens and of the immune response. Based upon our pilot data, we submit that exposure to xenobiotics induces PBC in genetically susceptible hosts. This work is based on our previous observations that the immunodominant autoepitope for B cells, as well as autoreactive CD4 and CD8 cells, are all restricted to the inner lipoyl domain, highlighting this domain as a common hapten. Based upon this common lipoyl domain, we synthesized a library of synthetic structures designed to mimic a xenobiotic-modified lipoyl hapten that were then conjugated to the immunodominant PDC-E2 peptide. Using these structures, we determined that PBC sera were significantly more reactive against some hapten modified peptides than to the native lipoylated peptide. Furthermore, we have now demonstrated that immunization of rabbits and guinea pigs with one such xenobiotic compound, coupled to a large carrier (BSA), generates an AMA response which reacts with selfPDC-E2, binds to the inner lipoyl domain, and inhibits PDC-E2 function, thus recapitulating all the features of human AMA. We believe that this data provides solid evidence that a chemical xenobiotic conjugated to a protein that shares a motif with the autoantigen, may break tolerance, induce AMA, and ultimately lead to PBC. To prove this thesis, we need to perform a focused quantitative structure activity relationship analysis (QSAR) over a range of compounds to optimally define the structure that will best react with AMA. In addition, we need to significantly extend our study in rabbits and guinea pigs to define the spectrum of the immune response and induce immunopathology. We submit that a) additional QSAR studies may lead to a better understanding of the structure function relationships between the compound that breaks tolerance and the autoantibodies elicited by such a component, and thus may narrow our choice of compounds that are the true inducers of PBC; b) it may take a long time for animals immunized with the xenobiotic-carrier to develop disease (chronicity required); and c) that regardless of the identification of such compounds, disease induction and/or kinetics may need an additional immunological insult such as an inappropriate or Th1 cytokine environment. These studies are also critical for determining whether the immune response alone is essential for disease induction, or whether the unique milieu of human liver is required.