CELLULAR IMMUNITY TO JC VIRUS IN AIDS ASSOCIATED PML

JC病毒（JCV）是进行性多灶性白质脑病（PML）的病原体，PML是一种发生在潜在免疫抑制患者中的少突胶质细胞的溶血性感染。 JCV感染90%的正常成年人，但不会对健康个体造成任何疾病。 4%的艾滋病患者会出现病毒再激活，偶尔也会出现免疫抑制严重的患者。 这种再激活导致少突胶质细胞的抒情性感染和相关的中枢神经系统脱髓鞘。 在免疫功能正常的人中含有病毒的免疫应答的性质，以及在免疫抑制的个体中失败的免疫应答的性质尚不清楚。抗JCV抗体不能预防PML。 因此，JCV特异性细胞免疫应答可能在抑制该病毒复制方面具有关键作用。 了解对JCV的细胞免疫应答的性质对于表征PML的免疫发病机制至关重要。 细胞毒性T淋巴细胞（CTL）是参与抑制多种病毒感染的主要效应细胞。 CTL通过它们的T细胞受体和由感染细胞的MHC I类分子呈递的病毒肽表位的相互作用识别病毒感染的细胞。 可以使用功能性细胞毒性测定、通过用四聚体MHC I类/病毒肽复合物染色淋巴细胞的流式细胞术分析以及在抗原刺激的细胞因子产生测定中检测病毒特异性CTL。 在本申请中描述的研究中，我们将描述人类JCV特异性CTL应答的特征，并评估这种免疫应答在PML免疫发病机制中的作用。具体而言，我们将1）使用功能性裂解测定来表征JCV特异性细胞毒性T淋巴细胞2）绘制PML患者中的JCV CTL表位3）开发JCV特异性T淋巴细胞ELISPOT测定4）构建MHC I类/JCV肽四聚体复合物并确定JCV CTL表位免疫优势5）分析PML患者和对照受试者中对JCV的细胞免疫应答，使用MHC I类/JCV肽四聚体复合物染色和ELISPOT测定6）确定脑脊液中对JCV的细胞免疫应答7）将JCV特异性CTL的检测与PML患者的免疫状态和临床病程相关联

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