The role of CD4+ Cell Responses in LCMV Infection

描述(申请人提供)：近年来，在了解病毒生物学和对病毒感染的免疫反应方面取得了巨大的进步。在大多数病毒感染中，感染的急性期与成功的免疫反应有关，从而遏制了病毒血症和病毒传播。然而，某些病毒，如人类免疫缺陷病毒(HIV)和丙型肝炎病毒(丙型肝炎病毒)，能够建立持续感染。在这项提案中，我们将使用淋巴脉络膜脑膜炎病毒(LCMV)感染模型来探索为什么一组免疫反应在慢性感染中受到阻碍。 LCMV已被广泛用作宿主致病的小鼠模型，根据所用LCMV株的不同，既可以获得自解性急性感染(例如LCMV Armstrong)，也可以获得持续感染(例如LCMV克隆13)。到目前为止，我们在原始SCORE试点项目中所做的工作已经导致了LCMV阿姆斯特朗感染后一组9个CD4T细胞表位的表征，显示了在成功控制病毒复制的背景下的广泛反应。然而，LCMV克隆13在慢性感染中没有检测到这些反应。即使免疫后可以激发这些反应，但随后的LCMV克隆13感染会导致它们的抑制。最近也有研究表明，程序性死亡-1(PD-1)在慢性感染的T细胞中表达上调，导致T细胞的凋亡。这是否适用于持续LCMV感染的CD4T细胞仍有待观察。 我们假设LCMV持续株感染会导致LCMV特异性的CD4T细胞免疫功能受损，从而导致持续感染的建立。这项提议的长期目标是从机械上定义CD4T细胞在慢性感染中如何受损。为解决这个问题，我们的具体目标包括：(1)利用ELISPOT检测中的病毒冲击抗原提呈细胞和来自感染动物的CD4T细胞，确定持续LCMV感染后是否会发生有效的LCMV特异性CD4T细胞反应；(2)通过四聚体染色和淋巴因子产生的CD4T细胞的缺失和/或功能障碍，了解CD4T细胞损伤是否是持续LCMV感染中的CD4T细胞损伤的结果；(3)通过研究CD4T细胞是否表达高水平的PD-1(可被阻断)，来确定在LCMV持续感染的情况下是否可以挽救CD4T细胞反应。

DESCRIPTION (provided by applicant): In recent years, tremendous advances have been made in understanding viral biology and immune responses to viral infection. In the majority of viral infections, the acute phase of infection is associated with successful immune responses leading to the containment of viremia and viral spread. However, certain viruses, such as human immunodeficiency virus (HIV) and hepatitis C virus (HCV), are able to establish persistent infection. In this proposal, we are going to use the Lymphochoriomeningitis virus (LCMV) model of infection to probe why one set of immune responses is hampered in chronic infection. LCMV has been widely used as a murine model of host pathogenesis, and depending on the LCMV strain utilized, either self-resolving acute infection (e.g., LCMV Armstrong) or persistent infection (e.g., LCMV clone 13) can be obtained. The work we performed in our original SCORE pilot project has thus far lead to the characterization of a set of nine CD4+ T-cell epitopes after LCMV Armstrong infection, showing a broad repertoire of responses in the setting of successful control of viral replication. However, these responses were not detected in chronic infection with LCMV clone 13. Even though these responses could be elicited after immunization, subsequent LCMV clone 13 infection resulted in their suppression. It has also been recently shown by other groups that programmed death-1 (PD-1) is up-regulated in T-cells in chronic infection, resulting in their apoptosis. It remains to be seen whether this applies to CD4+ T-cells in persistent LCMV infection. We hypothesize that infection with persistent LCMV viral strains leads to impairment of LCMV-specific CD4+ T-cell immunity contributing to the establishment of persistent infection. The long-term goal of this proposal is to mechanistically define how CD4+ T-cells are impaired in chronic infection. To address this, our specific aims consist of the following: (1) to determine whether effective LCMV-specific CD4+ T-cell responses develop after persistent LCMV infection using virus-pulsed antigen presenting cells and CD4+ T-cells from infected animals in ELISPOT assays; (2) to understand whether CD4+ T-cell impairment is a result of deletion and/or dysfunction in persistent LCMV infection by following CD4+ T-cells with tetramer staining and lymphokine production; (3) to determine whether CD4+ T-cell responses can be rescued in the setting of LCMV persistent infection by investigating if CD4+ T-cells express high levels of PD-1 which can be blocked.