XENOBIOTICS AND PRIMARY BILIARY CIRRHOSIS

描述（由申请人提供）：原发性胆汁性肝硬化（PBC）的病因学仍然是个谜，尽管我们对自身抗原和免疫应答的性质的理解有了重大进展。根据我们的试验数据，我们认为暴露于外源性物质会诱导遗传易感宿主的PBC。这项工作是基于我们以前的观察，即B细胞以及自身反应性CD 4和CD 8细胞的免疫显性自身表位都局限于内部硫辛酰结构域，突出了该结构域作为共同的半抗原。基于这个共同的硫辛酰结构域，我们合成了一个合成结构库，该结构库被设计成模拟异生物质修饰的硫辛酰半抗原，然后将其缀合至免疫显性PDC-E2肽。使用这些结构，我们确定PBC血清对某些半抗原修饰肽的反应性显著高于对天然脂酰化肽的反应性。此外，我们现在已经证明，用一种这样的异生物质化合物与大载体（BSA）偶联免疫家兔和豚鼠，产生AMA反应，该反应与自身PDC-E2反应，与内部硫辛酰结构域结合，并抑制PDC-E2功能，从而重现了人AMA的所有特征。我们认为，这些数据提供了坚实的证据，表明与自身抗原共享基序的蛋白质结合的化学异生素可能会破坏耐受性，诱导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构效关系分析（QSAR），以最佳地确定与AMA反应最好的结构。此外，我们需要在兔子和豚鼠中显著扩展我们的研究，以确定免疫应答谱并诱导免疫病理学。我们认为，a）额外的QSAR研究可能导致更好地理解破坏耐受性的化合物与由这种组分引起的自身抗体之间的结构功能关系，从而可能缩小我们对PBC真正诱导剂的化合物的选择; B）用外源性载体免疫的动物可能需要很长时间才发生疾病（需要慢性）;和c）无论这些化合物的鉴定如何，疾病诱导和/或动力学可能需要额外的免疫损伤，例如不适当的或Th 1细胞因子环境。这些研究对于确定免疫反应是否是疾病诱导所必需的，或者是否需要人类肝脏的独特环境也至关重要。

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.