Signaling via MHC: engineering immune cells with new capabilities

摘要 T细胞是适应性免疫系统的重要组成部分，可以抵御病原体和肿瘤， 同时容忍自己的组织。T细胞反应的失调可导致传染病、癌症或 自身免疫性疾病。T细胞有效性的关键是其精致的抗原特异性，这可以 被用来与疾病作斗争。T细胞利用其表面T细胞受体(TCR)识别多肽表位 关于主要组织相容性复合体分子(PMHC)。同时通过TCR和ITS发送信号 后果已被广泛研究，pMHC传统上仅被视为靶细胞上的一面旗帜 T细胞的识别能力。MHC分子没有规范的细胞内信号域，因此有 不会在呈现它们的细胞中引入任何功能，使TCR-pMHC相互作用在术语上是一条“单行道” 功能反应。这提供了一个独特的工程机会：TCR-pMHC相互作用能否成为 “双行道”？在这里，我们假设如果pMHC复合体增加了信号域，它们 可以引发信号级联反应，导致反应基因的表达，从而导致细胞固有的功能 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 由我的团队开发：信号和抗原递呈双功能受体(SABRs)。SABR包括 细胞外全长MHC复合体，具有遗传(因此共价)连接的表位，与 细胞内信号域。SABRs可以向T细胞递呈表位，并在细胞内引发信号转导 成功识别，从而将TCR-pMHC相互作用转换为“双向街道”。在这项提案中，我们 目的利用SABRs赋予免疫和非免疫细胞新的功能，从而打开一种 免疫工程和合成免疫学的新前沿。我们将首先制定一个开发框架 SABRs作为增强免疫和非免疫组合工程能力的细胞工程平台 以达到预期的免疫效果。我们将描述SABRs的三个免疫应用：1)工程 用细胞毒性CD8+T细胞或自然杀伤(NK)细胞消除自身反应性的CD4+T细胞，2)工程 专业抗原提呈细胞(APC)调节自身反应性或抗肿瘤CD8+T细胞反应，3) 改造CD8+T细胞以感知对特定抗原的内源性免疫并诱导二级功能， 导致了一种“读取并反应”的分子回路。这些研究将创造细胞治疗方式，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 研究将对研究和治疗广泛的疾病--自身免疫--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