Etiology and Pathogenesis of Pemphigus

描述（由申请人提供）：该基金旨在发现巴西农村地方性落叶型天疱疮（PF）的病因，也称为Fogo Selvagem（FS）。这种表皮特异性自身免疫性疾病由致病性IgG4抗桥粒芯糖蛋白1（Dsg1）自身抗体介导。1994年，我们确定了巴西Limao Verde（LV）的美洲印第安人保留区，约有1，400人，FS的患病率约为3%。重要的是，我们在过去的18年中对这一人群进行了临床和血清学研究，确定了12个人从正常到FS的转变，并报告说，接触吸血节肢动物是FS的潜在危险因素。此外，利什曼病、恰加斯病和盘尾丝虫病患者的血清（其中这些昆虫作为寄生虫的携带者参与）具有抗Dsg 1抗体。最近，我们已经表明，IgG4抗Dsg1自身抗体交叉反应的构象表位的LJM 11“黄色”蛋白从唾液的Lutzomyia longipalpis，载体利什曼病。本提案的目的是确定Dsg1如何成为FS中免疫系统的靶标，并确定启动抗自身反应的环境抗原。基于以往的研究，我们推测嗜血昆虫的唾液抗原是FS致敏抗原的来源。这项资助的目的是鉴定Dsg1和LJM 11上与FS患者IgG 4抗体交叉反应的表位，并测试患者血清中存在的这些抗体是否来自结合外源抗原或自身抗原或两者的幼稚B细胞。在目的1中，我们将确定由来自FS患者的血清和B细胞的IgG 4抗Dsg 1多克隆抗体结合Dsg 1（自身）和LJM 11（白蛉）抗原的构象表位。此外，我们将通过被动转移实验测试结合人Dgs 1的鼠抗LJM 11抗体是否具有致病性。目的2：利用噬菌体展示技术从FS B细胞中制备IgG 4单克隆抗体（scFv），并通过淘选法筛选Dsg 1和LJM 11特异性克隆。将测试这些scFv抗体的致病性并用于更精确的表位作图。此外，将产生“回复突变体”单克隆抗体，并测试其与Dsg1和LJM 11的反应性，以努力揭示FS中IgG4抗体应答的初始触发因素。目标3和4涉及三个队列和Limao Verde人口的血清流行病学研究。我们将继续寻找可能导致正常人IgG自身免疫反应和FS患者IgG4的危险因素。从正常到疾病状态的转变可能会在队列的随访研究中发现。在完成这些新的研究，我们将有一个更好的了解环境抗原如何可能触发，在某些遗传易感的个人，自身免疫性IgG 4反应，导致皮肤病。与此同时，新的表位特异性免疫测定和潜在的新的治疗干预可能会从这些研究中发展出来。

DESCRIPTION (provided by applicant): This grant is aimed at discovering the etiology of endemic pemphigus foliaceus (PF), also known as Fogo Selvagem (FS) in rural Brazil. This epidermal-specific autoimmune disease is mediated by pathogenic IgG4 anti-desmoglein 1 (Dsg1) autoantibodies. In 1994, we identified the Amerindian Reservation of Limao Verde (LV), Brazil composed of ~1,400 individuals where the prevalence of FS was ~3%. Importantly, we have followed this population clinically and serologically for the last 18 years, identifying transitions from normal to FS in 12 individuals, and reported that exposure to blood feeding arthropods is a potential risk factor for FS. Moreover, the sera of patients with leishmaniasis, Chagas disease and onchocerciasis, where these insects are involved as carriers of parasites, possess anti-Dsg1 antibodies. Recently, we have shown that IgG4 anti-Dsg1 autoantibodies cross-react with conformational epitopes of the LJM11 "yellow" protein from the saliva of Lutzomyia longipalpis, the vector of leishmaniasis. The objective of this proposal is to determine how Dsg1 becomes the target of the immune system in FS and to identify the environmental antigen(s) that initiate the anti-self response. Based on previous studies, we hypothesize that salivary antigens from hematophagous insects are the source of sensitizing antigen in FS. The aims of this grant will identify epitopes on Dsg1 and LJM11 that cross-react with IgG4 antibodies from FS patients and test whether these antibodies present in patient sera derive from na¿ve B cells that bind foreign or self-antigens or both. In Aim 1 we will determine the conformational epitopes bound by IgG4 anti-Dsg1 polyclonal antibodies from sera and B cells of FS patients on Dsg1(self) and LJM11(sand fly) antigens. Moreover, we shall test if murine anti-LJM11 antibodies, that bind human Dgs1, are pathogenic by passive transfer experiments. In Aim 2 we shall generate IgG4 monoclonal antibodies (scFv) from FS B cells by phage display methods and select Dsg1 and LJM11 specific clones by panning procedures. These scFv antibodies will be tested for pathogenicity and used for more precise epitope mapping. Further, "revertant" monoclonal antibodies will be generated and tested for reactivity with Dsg1 and LJM11 in an effort to disclose the initial trigger of the IgG4 antibody response in FS. Aim 3 and 4 are concerned with seroepidemiological studies in three cohorts and the population of Limao Verde. We shall continue searching for risk factors that may precipitate the IgG autoimmune response in normal subjects and the IgG4 in FS patients. The transition from normal to disease state will likely be uncovered on the follow up studies of the cohorts. At the completion of these novel studies we shall have a better understanding of how environmental antigens might trigger, in certain genetically predisposed individuals, an autoimmune IgG4 response that leads to skin diseases. In parallel, new epitope-specific immunoassays and potential novel therapeutic interventions may evolve from these studies.