Signaling via MHC: engineering immune cells with new capabilities

摘要 T细胞构成了适应性免疫系统的一个重要分支，保护免受病原体和肿瘤的侵害， 同时耐受自身组织。T细胞反应的失调可导致感染性疾病、癌症或其他疾病。 自身免疫性疾病T细胞有效性的关键是它们精致的抗原特异性， 被用来对抗疾病。T细胞利用其表面T细胞受体（TCR）识别肽表位 主要组织相容性复合物（MHC）分子（pMHC）。当通过TCR及其受体发出信号时， 尽管已经广泛研究了pMHC的结果，但pMHC通常被视为靶细胞上的“标志”， T细胞的识别。MHC分子没有典型的胞内信号结构域，因此 不引起呈递它们的细胞的任何功能，使得TCR-pMHC相互作用在术语上是“单行道”。 功能性反应。这提供了一个独特的工程机会：TCR-pMHC相互作用能否成为 “双向街道”？在这里，我们假设如果pMHC复合物增加了信号结构域， 可以引发信号级联，导致反应基因的表达，这将导致细胞内在的功能性 变化，最终导致细胞外在功能的变化。为此，我们将使用工程平台 信号和抗原呈递双功能受体（Signaling and Antigen-presenting Bifunctional Receptors，SABR）。SABR包括 细胞外全长MHC复合物与基因（并因此共价）连接的表位，融合 胞内信号结构域。SABR可以将表位呈递给T细胞并在T细胞活化后引发细胞内信号传导。 成功识别，从而将TCR-pMHC相互作用转化为“双向街道”。在本提案中，我们 目的是利用SABR赋予免疫和非免疫细胞新的功能，从而打开一个新的领域。 免疫工程和合成免疫学的新前沿。我们将首先制定一个框架， SABR作为一个细胞工程平台，使免疫和非免疫的组合工程 细胞，以达到预期的免疫效果。我们将描述SABR的三种免疫应用：1）工程 细胞毒性CD 8 + T细胞或自然杀伤（NK）细胞以消除自身反应性CD 4 + T细胞，2）工程化 专职抗原呈递细胞（APC）调节自身反应性或抗肿瘤CD 8 + T细胞应答，3） 工程化CD 8 + T细胞以感应针对特异性抗原的内源性免疫并诱导第二功能， 从而形成“读取-反应”分子电路。这些研究将创造细胞治疗模式，免疫 监测和扰动工具，实验模型系统和发现新的免疫现象。这些 这些研究将对研究和治疗广泛的疾病产生深远的影响， 疾病、传染病、癌症和器官移植。 1

ABSTRACT T cells constitute an essential arm of the adaptive immune system, protecting against pathogens and tumors, while tolerating self-tissues. Dysregulation of T cell responses can lead to infectious diseases, cancers, or autoimmune disorders. The key to the effectiveness of T cells is their exquisite antigenic specificity, which can be harnessed to combat diseases. T cells use their surface T cell receptor (TCR) to recognize peptide epitopes on Major Histocompatibility Complex (MHC) molecules (pMHC). While signaling through the TCR and its consequences have been studied extensively, pMHC is conventionally seen as merely a ‘flag’ on target cells for recognition by T cells. MHC molecules do not have canonical intracellular signaling domains, and therefore do not elicit any function into the cells presenting them, making TCR-pMHC interaction a ‘one-way street’ in terms of functional response. This presents a unique engineering opportunity: can TCR-pMHC interactions become ‘two-way streets’? Here, we hypothesize that if pMHC complexes are augmented with signaling domains, they can elicit signaling cascades, leading to expression of response genes that will cause cell-intrinsic functional changes, ultimately leading to cell-extrinsic functional changes. To that end, we will use the engineering platform developed by my group: Signaling and Antigen-presenting Bifunctional Receptors (SABRs). SABRs consist of extracellular full-length MHC complexes with genetically (and hence covalently) linked epitopes, fused with intracellular signaling domains. SABRs can present epitopes to T cells and elicit intracellular signaling upon successful recognition, thereby converting TCR-pMHC interactions into ‘two-way streets. In this proposal, we aim to wield SABRs to impart novel functional capabilities to immune and non-immune cells, thereby opening a new frontier of immune engineering and synthetic immunology. We will first lay out a framework for developing SABRs as a cellular engineering platform to empower combinatorial engineering of immune and non-immune cells to achieve desired immune outcome. We will describe three immune applications of SABRs: 1) engineering of cytotoxic CD8+ T cells or Natural Killer (NK) cells to eliminate autoreactive CD4+ T cells, 2) engineering professional Antigen-Presenting Cells (APCs) to modulate self-reactive or anti-tumor CD8+ T cell responses, 3) engineering CD8+ T cells to sense endogenous immunity to specific antigens and induce a secondary function, leading to a ‘read-and-react’ molecular circuit. These studies will create cellular therapeutic modalities, immune monitoring and perturbation tools, experimental model systems and uncover new immune phenomena. These studies will have profound implications on study and treatment of a wide range of diseases – autoimmune disorders, infectious diseases, cancers, and organ transplantations. 1