CELLULAR IMMUNITY TO JC VIRUS IN AIDS ASSOCIATED PML

JC病毒(JC病毒)是进行性多灶性白质脑病(PML)的病原体，PML是一种少突胶质细胞的抒情感染，发生在有潜在免疫抑制的患者身上。JCV感染90%的正常成年人，但不会导致健康个体的任何疾病。病毒重新激活发生在4%的艾滋病患者中，偶尔也会发生其他免疫严重抑制的人。这种重新激活导致少突胶质细胞的抒情感染和相关的中枢神经系统脱髓鞘。免疫功能正常的人的免疫反应包含病毒，而免疫抑制的人免疫反应失败，其免疫反应的性质尚不清楚。抗JCV抗体不能预防PML。因此，JCV特异性细胞免疫反应很可能在遏制该病毒复制方面起到关键作用。了解对JCV的细胞免疫反应的本质对于确定PML的免疫发病机制具有重要意义。细胞毒性T淋巴细胞(CTL)是控制多种病毒感染的主要效应细胞。CTL通过T细胞受体与感染细胞的MHC-I类分子呈递的病毒表位相互作用来识别病毒感染的细胞。病毒特异性CTL可通过功能细胞毒性试验、通过四聚体MHC I类/病毒多肽复合物染色淋巴细胞的流式细胞仪分析以及抗原刺激的细胞因子产生试验来检测。在本申请中描述的研究中，我们将描述人类中JCV特异性CTL反应的特征，并评估这种免疫反应在PML免疫发病机制中的作用。具体地说，我们将1)用功能裂解试验鉴定JCV特异性细胞毒性T淋巴细胞2)定位PML患者的JCV CTL表位3)建立JCV特异性T淋巴细胞ELISPOT试验4)构建MHC I/JCV四聚体并测定JCV CTL表位免疫优势5)分析PML患者和对照组对JCV的细胞免疫应答，使用MHC I/JCV四聚体染色和ELISPOT试验6)确定脑脊液中对JCV的细胞免疫应答7)JCV特异性CTL的检测与PML患者的免疫状态和临床病程相关

JC virus (JCV) is the etiologic agent of progressive multifocal leucoencephalopathy (PML), a lyric infection of oligodendrocytes occurring in patients with underlying immunosuppression. JCV infects 90% of normal adults, but does not cause any disease in healthy individuals. Viral reactivation occurs in 4% of patients with AIDS, and occasional other individuals who are profoundly immunosuppressed. This reactivation leads to a lyric infection of oligodendrocytes and an associated demyelination of the central nervous system. The nature of the immune response that contains the virus in immunocompetent people, and fails in immunosuppressed individuals, is unknown. Anti-JCV antibodies do not protect against PML. Therefore, the JCV-specific cellular immune response is likely to have a crucial role in containing replication of this virus. Understanding the nature of the cellular immune response to JCV is of central importance in characterizing the immunopathogenesis of PML. Cytotoxic T lymphocytes (CTL) are the major effector cells involved in containing many viral infections. CTL recognize virus-infected cells through the interaction of their T-cell receptor and a viral peptide epitope presented by the MHC class I molecule of the infected cell. Virus-specific CTL can be detected using functional cytotoxicity assays, by flow cytometric analyses through staining of lymphocytes with tetrameric MHC class I/viral peptide complexes, and in antigen-stimulated cytokine production assays. In the studies described in this application we will characterize the JCV-specific CTL response in humans and assess the role of this immune response in the immunopathogenesis of PML. Specifically, we will 1) characterize JCV-specific cytotoxic T lymphocytes using functional lysis assays 2) map JCV CTL epitopes in patients with PML 3) develop JCV-specific T lymphocyte ELISPOT assays 4) construct MHC class I/JCV peptide tetramer complexes and determine JCV CTL epitope immunodominance 5) analyze the cellular immune response to JCV in patients with PML and control subjects, using MHC class I/JCV peptide tetramer complex staining and ELISPOT assays 6) define the cellular immune response to JCV in the cerebrospinal fluid 7) correlate the detection of JCV-specific CTL with the immune status and clinical course of patients with PML