The role of CD4+ Cell Responses in LCMV Infection

描述（由申请人提供）：近年来，在理解病毒生物学和对病毒感染的免疫应答方面取得了巨大进展。在大多数病毒感染中，感染的急性期与成功的免疫应答相关，导致病毒血症和病毒传播的遏制。然而，某些病毒，如人类免疫缺陷病毒（HIV）和丙型肝炎病毒（HCV），能够建立持续感染。在这个提议中，我们将使用脉络丛脑膜炎病毒（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已被广泛用作宿主发病机制的鼠模型，并且取决于所用的LCMV毒株，可以是自行消退的急性感染（例如，LCMV Armstrong）或持续感染（例如，可以获得LCMV克隆13）。我们在最初的SCORE试点项目中进行的工作迄今为止已经导致了LCMV Armstrong感染后一组9个CD 4 + T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库。然而，在LCMV克隆13的慢性感染中未检测到这些应答。尽管这些反应可以在免疫后引起，但随后的LCMV克隆13感染导致其抑制。其他研究小组最近也表明，慢性感染中T细胞中程序性死亡-1（PD-1）上调，导致其凋亡。这是否适用于持续性LCMV感染中的CD 4 + T细胞还有待观察。 我们推测持续性LCMV病毒株感染导致LCMV特异性CD 4 + T细胞免疫功能受损，从而导致持续性感染。该提案的长期目标是从机制上确定CD 4 + T细胞在慢性感染中如何受损。为了解决这个问题，我们的具体目标包括以下内容：（1）在ELISPOT测定中使用来自感染动物的病毒脉冲抗原呈递细胞和CD 4 + T细胞来确定在持续的LCMV感染后是否产生有效的LCMV特异性CD 4 + T细胞应答;（2）通过随访CD 4 + T细胞亚群，了解CD 4 + T细胞损伤是否是持续性LCMV感染的缺失和/或功能障碍的结果。（3）通过研究CD 4 + T细胞是否表达可被阻断的高水平PD-1来确定在LCMV持续感染的情况下是否可以挽救CD 4 + T细胞应答。

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.