Autoimmunity to LINE-1-encoded antigens in SLE pathogenesis

项目总结/摘要 虽然在系统性红斑狼疮（SLE）中， 世纪以来，所有的研究都未能确定这种自身免疫性疾病的微生物原因。这导致 寻找SLE中无菌性炎症和I型干扰素（IFN-I）产生的内源性驱动因素。40多 人类基因组的10%是由数十万个重复序列组成的，这些序列是从 转座子含有类似病毒的序列。反转录转座子是主要的 大多数哺乳动物基因组中的一类转座因子。近年来，人们发现， 病毒产物、源自这些基因组“寄生虫”的核酸可以激活胞质核酸传感器。 这些发现将逆转录转座子表达失调与以下疾病联系起来： 持续的IFN-I产生，如SLE。特别是，非LTR亚类的调节缺陷 逆转录转座子，长散布核元件-1（LINE 1或L1），与SLE相关 发病机制为了进一步了解L1元件在SLE中的潜在作用，我们将重点放在中性粒细胞上。 和IFN-1，在SLE发病机制中的两个重要参与者。L1含有两个开放阅读框（ORF 1和ORF 2）。 利用SLE中性粒细胞与IFN-I激活的证据，我们最初确定了一种新的多态性变异体， ORF1。在初步研究中，我们使用由该变体编码的蛋白质（ORF 1 p）作为抗原， SLE患者首次出现L1-ORF 1 p抗体。这支持了L1元素是 活性及其产物刺激SLE的免疫应答。除了这些创新的发现， 这些数据提供了与L1在SLE发病机制中的作用相关的新假说。它将注意力集中在中性粒细胞上， L1-ORF 1 p的潜在来源，表明ORF 1 p的多态性变体（可能被错误地 被认为是“病毒衍生的”产物）可能触发针对该蛋白质的体液应答，并打开 抗ORF 1 p抗体在SLE中可能是致病性的。这一探索性建议的主要目标是 为了进一步了解这些新的假设和初步发现的潜在意义， SLE发病机制的背景。在目标1中，我们将使用基于捕获的L1-ORF 1富集与RNA-聚合物组合。 Seq以确定独特的ORF 1转录变体是否在对照和IFN-γ中差异表达。 激活SLE中性粒细胞。此外，我们将确定ORF 1 p变体是否优先被 SLE中的抗体在目标2中，我们将确定ORF 1 p抗体的患病率和临床相关性。 以及它们与SLE患者前瞻性观察队列中IFN信号的关系， 广泛的临床和血清学数据以及IFN诱导的基因表达分析是可用的。在一起， 这些研究试图增强我们对无菌性炎症的自身免疫原性途径的理解 在SLE中。这项工作的最终目标是获得对疾病机制的新见解，从而为 探索新疗法

PROJECT SUMMARY/ABSTRACT While an infectious etiology has been hypothesized in systemic lupus erythematosus (SLE) for more than a century, all studies have failed to identify a microbial cause of this autoimmune disease. This has led to the search for endogenous drivers of sterile inflammation and type I interferon (IFN-I) production in SLE. Over 40 percent of the human genome is made up of hundreds of thousands of repetitive sequences that evolved from genetic elements called transposons, which contain virus-like sequences. Retrotransposons are the predominant class of transposable elements in most mammalian genomes. In recent years, it has been found that similar to viral products, nucleic acids derived from these genomic “parasites” can activate cytosolic nucleic acid sensors. These findings have linked dysregulated expression of retrotransposons with diseases characterized by sustained IFN-I production, such as SLE. In particular, defective regulation of a subclass of non-LTR retrotransposon, the long interspersed nuclear element-1 (LINE1 or L1), has been associated to SLE pathogenesis. To gain further insights into the potential role of L1 elements in SLE, we focused on neutrophils and IFN-I, two important players in SLE pathogenesis. L1 contains two open-reading frames (ORF1 and ORF2). Using SLE neutrophils with evidence of IFN-I activation, we initially identified a novel polymorphic variant of ORF1. Using the protein (ORF1p) encoded by this variant as an antigen in preliminary studies, we identified for the first time that patients with SLE have antibodies to L1-ORF1p. This supports the notion that L1 elements are active and their products stimulate the immune response in SLE. In addition to these innovative findings, our data provide novel hypotheses related to the role of L1 in SLE pathogenesis. It focus attention on neutrophils as a potential source of L1-ORF1p, suggests that polymorphic variants of ORF1p (which could be mistakenly recognized as “viral-derived” products) may trigger the humoral response against this protein, and opens the possibility that anti-ORF1p antibodies may be pathogenic in SLE. The major goal of this exploratory proposal is to gain further insights into the potential significance of these novel hypotheses and preliminary findings in the context of SLE pathogenesis. In Aim 1, we will use capture-based enrichment of L1-ORF1 combined with RNA- Seq to determine whether unique ORF1 transcriptional variants are differentially expressed in control and IFN- activated SLE neutrophils. In addition, we will define whether ORF1p variants are preferentially recognized by antibodies in SLE. In Aim 2, we will determine the prevalence and clinical associations of antibodies to ORF1p and their relationship to the IFN-signature in a prospective observational cohort of patients with SLE, for which extensive clinical and serologic data is available, as well as IFN-induced gene expression analysis. Together, these studies seek to enhance our understanding of self-immunogenic pathways underlying sterile inflammation in SLE. The final goal of this work is to gain new insights into disease mechanisms, thus laying the foundation to explore novel therapies.