Mechanisms and optimization of epitope presentation by HIV-infectable cell subset

描述（由申请方提供）：HIV特异性细胞毒性T淋巴细胞（CTL）在急性感染或自发控制情况下抑制HIV病毒血症中发挥关键作用，使其成为疫苗策略的有吸引力的候选者。然而，迄今为止开发的疫苗未能保护免受HIV感染，尽管产生CTL应答。针对病毒某些区域的CTL应答在控制HIV复制方面可能比具有其他特异性的CTL更有效，这一事实表明疫苗应引发与保护相关的选择性CTL应答。HIV感染细胞对同源表位的有效呈递是保护性CTL应答的关键条件。然而，仍然有令人惊讶的是，很少了解的细胞内机制管理的CD 8 T细胞识别的HIV表位的介绍。大多数关于HIV特异性CTL功能的研究都利用合成肽形式的同源表位，从而绕过蛋白质降解的所有细胞内步骤，导致表位的呈现。HIV感染几种表达CD 4的亚群（CD 4 T细胞、单核细胞/巨噬细胞和树突细胞），这些亚群将呈递HIV表位。这些亚群是否呈现具有相同动力学的相似表位尚不清楚。亚群之间表位呈递的变化可能影响CTL的抗病毒效力。相反，鉴定HIV中有效加工成所有亚群中的表位的区域对于鉴定保护性CTL应答和选择免疫原是最重要的。基于新的表位加工测定，我们显示了一些HIV表位的优先加工，这一特性依赖于我们用来改变不相关表位产生的基序。我们还确定了一个新的因素参与表位加工效率，即高度可变的最佳HIV表位的细胞内稳定性，也由特定的基序驱动。最后，我们表明，CD 4 T细胞具有较低的加工活动比单核细胞，这影响了HIV蛋白降解产物的动力学和抗原性。这些数据表明，表位的产生是由规则控制的，可以利用这些规则来设计定制的免疫原。具体而言，我们建议：1）确定与HIV病毒血症的自发控制相关的CTL应答是否有效地识别并杀死所有HIV可感染的细胞亚群。利用大量的控制者和进展者，我们将评估由各种HIV感染亚群刺激的CD 8 T细胞的功能。2)识别在可感染亚群的不同抗原加工途径中通常产生的肽，这些肽有助于自发性控制病毒血症。使用纳米颗粒靶向细胞亚群内的HIV蛋白，我们将鉴定所有亚群产生的抗原肽。3)设计和测试导致保护性HIV表位选择性呈递的序列特征。该建议依赖于跨学科的合作方法，涉及计算科学，生物工程工具和生物化学和免疫学测定表位加工和CTL功能的原代细胞设计。HIV特异性CD 8 T细胞能够杀死HIV感染的细胞，因为感染的细胞显示称为表位的病毒片段。破译HIV抗原决定簇的产生和呈递机制，刺激有效的免疫应答，是合理疫苗设计的关键。该项目旨在确定免疫反应和抗原表位提出的HIV感染的细胞亚群的人自发检测不到的病毒血症（控制器），并确定因素的表位加工的效率，这将使选择性介绍的保护性抗原表位的免疫原。

DESCRIPTION (provided by applicant): HIV-specific cytotoxic T-lymphocytes (CTL) play a critical role in containing HIV viremia in acute infection or in situation of spontaneous control, rendering them attractive candidates for vaccine strategies. However vaccines developed so far have failed to protect against HIV infection, this despite generating CTL responses. The fact that CTL responses against certain areas of the virus may be more effective at controlling HIV replication than CTL with other specificities suggests that vaccine should elicit selected CTL responses associated with protection. Effective presentation of the cognate epitopes by HIV-infected cells is a crucial condition for protective CTL responses. However, there is still surprisingly little understanding of intracellular mechanisms governing the presentation of HIV epitopes recognized by CD8 T cells. Most studies on HIV- specific CTL functions utilize cognate epitopes in the form of synthetic peptides, thus bypassing all intracellular steps of protein degradation leading to the presentation of epitopes. HIV infects several CD4-expressing subsets (CD4 T cells, monocyte/macrophages and dendritic cells) that will present HIV epitopes. Whether these subsets present similar epitopes with identical kinetics is unknown. Variations in epitope presentation between subsets may affect the antiviral efficacy of CTL. Conversely identifying areas of HIV that are efficiently processed into epitopes in all subsets is of highest importance for the identification of protective CTL responses and selection of immunogens. Building on novel epitope processing assays, we showed preferential processing of some HIV epitopes, a property that relies on motifs we used to alter the production of irrelevant epitopes. We also identified a novel factor involved in epitope processing efficiency, namely the highly variable intracellular stability of optimal HIV epitopes, also driven by specific motifs. Finally we show that CD4 T cells have lower processing activities than monocytes, which affects the kinetics and antigenicity of degradation products from HIV proteins. These data suggest that epitope production is controlled by rules that could be exploited to design customized immunogens. Specifically we propose to: 1) Determine whether CTL responses associated with spontaneous control of HIV viremia efficiently recognize and kill all HIV-infectable cell subsets. Taking advantage of a large cohort of controllers and progressors, we will assess the functionality of CD8 T cells stimulated by various HIV-infected subsets. 2) Identify peptides commonly produced in distinct antigen processing pathways of infectable subsets contributing to spontaneous controlled viremia. Using nanoparticles to target HIV proteins inside cell subsets, we will identify antigenic peptides produced by all subsets. 3) Design and test sequence signatures leading to the selective presentation of protective HIV epitopes. This proposal relies on a cross-disciplinary collaborative approach involving computational science, bioengineered tools and biochemical and immunological assays of epitope processing and CTL functions designed for primary cells. HIV-specific CD8 T cells are able to kill HIV-infected cells because infected cells display pieces of virus called epitopes. Deciphering the mechanisms of production and presentation of HIV epitopes stimulating efficient immune responses is key to rational vaccine design. This project seeks to identify immune responses and epitopes presented by HIV-infected cell subsets from persons with spontaneously undetectable viremia (controllers) and to define factors governing the efficiency of epitope processing that will enable selected presentation of protective epitopes in immunogens.