Immune responses against HIV-induced cell-derived neoepitopes and HIV control

描述(由申请人提供)：目前旨在识别保护性细胞毒性T细胞(CTL)反应和设计针对HIV的疫苗的策略是基于这样的假设，即在HIV感染期间引发的免疫反应仅针对HIV表位。这些策略的局限性是艾滋病毒特异性保护性免疫反应的难以捉摸，以及许多艾滋病毒特异性CTL对艾滋病毒施加压力，导致病毒突变和随后的免疫逃逸。因此，诱导HIV特异性CTL反应可能不足以阻断HIV的传播。这项提议将专门测试这一假设，即非传统艾滋病毒诱导的宿主衍生的新表位在艾滋病毒感染细胞(但不是健康细胞)中独特地处理和呈现，激发有助于自发艾滋病毒免疫控制的CTL反应。这些HIV诱导的宿主衍生的抗病毒表位(HDAE)和相应的CTL反应(不受免疫压力)的鉴定将在一组HIV自发控制者中进行，这些人具有弱的HIV特异性CTL反应。细胞和HIV蛋白被胞浆中的蛋白酶体和其他多肽酶降解成表位或表位前体，然后在内质网中被修剪，然后被装载到MHC-I上，并在细胞表面展示，供CTL识别。在新的表位处理分析的基础上，我们显示了一些HIV表位的优先处理，这种特性依赖于我们用来改变无关表位的产生的基序。我们还发现了一个与表位处理效率有关的新因素，即最优HIV表位的高度可变的细胞内稳定性，也是由特定的基序驱动的。在HIV感染的细胞中，我们最近发现的抗原处理机制的表达和活性的改变，额外的HIV编码的蛋白酶的存在，以及特定细胞靶点的大量降解，可能会改变细胞蛋白质的降解模式，产生HDAE。然而，通过全面筛选细胞多肽来识别HDAE特异性CTL反应是不可能的。通过与微软研究院的合作，我们将建立一个定制的预测程序，并扫描人类基因组，寻找在感染艾滋病毒的原代细胞中产生的抗原肽。通过一种创新的基于质谱学的分析，我们将识别在HIV控制者感染HIV的CD4T细胞胞浆中唯一发现的抗原前体。它们的特性将通过计算分析和目标蛋白的体外降解来确认。我们将筛查HIV感染者对HDAE的CTL反应，分离HDAE特异性CTL，并评估其抗病毒能力。我们还将评估单核细胞来源的树突状细胞交叉呈现由HIV感染的CD4T细胞内源性处理的HDAE的能力，以刺激CTL，其抗病毒能力将被评估。这一建议依赖于跨学科合作，涉及计算科学，为原代细胞设计的新型生化和免疫学分析。确定HDAE将有助于设计新的免疫原，激发CTL反应，防止艾滋病毒传播。

DESCRIPTION (provided by applicant): Current strategies aiming at identifying protective cytotoxic T cell (CTL) responses and designing vaccines against HIV are based on the assumption that immune responses elicited during HIV infection are only directed against HIV epitopes. The limitations of these strategies are the elusiveness of HIV-specific protective immune responses and the fact that many HIV-specific CTL exert pressure on HIV leading to viral mutations and subsequent immune escape. Thus eliciting HIV-specific CTL responses may not be sufficient to block the transmission of HIV. This proposal will specifically test the hypothesis that unconventional HIV-induced host- derived neoepitopes uniquely processed and presented in HIV-infected cells (but not in healthy cells) elicit CTL responses contributing to spontaneous HIV immune control. The identification of these HIV-induced Host- Derived Antiviral Epitopes (HDAE) and corresponding CTL responses -not subjected to immune pressure- will be performed in a unique cohort of HIV spontaneous controllers with weak HIV-specific CTL responses. Cellular and HIV proteins are degraded into epitopes or epitope precursors by the proteasome and other peptidases in the cytosol and then trimmed in the endoplasmic reticulum before being loaded onto MHC-I and displayed at the cell surface for recognition by CTL. 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. In HIV-infected cells, the altered expression and activities of the antigen processing machinery that we recently identified, the presence of an additional HIV-encoded protease along with massive degradation of specific cellular targets are likely to alter the degradation pattern of cellular proteins and produce HDAE. Yet it is impossible to identify HDAE-specific CTL responses by a comprehensive screen of cellular peptides. Through a collaboration with Microsoft Research, we will build a customized prediction program and scan the human genome for antigenic peptides produced in HIV-infected primary cells. With an innovative mass spectrometry- based analysis, we will identify antigenic precursors uniquely found in the cytosol of HIV-infected CD4 T cells from HIV controllers. Their identity will be confirmed through computational analysis and in vitro degradation of target proteins. We will screen HIV-infected persons for CTL responses against HDAE, isolate HDAE-specific CTL and assess their antiviral capacity. We will also assess the capacity of monocyte-derived dendritic cells to cross-present HDAE endogenously processed by HIV-infected CD4 T cells, to stimulate CTL whose antiviral capacity will be assessed. This proposal relies on a cross-disciplinary collaboration involving computational science, novel biochemical and immunological assays designed for primary cells. Identifying HDAE will contribute to the design of novel immunogens eliciting CTL responses that will prevent HIV transmission.