TLR2 Engagement on Tumor-Specific T Cells: Mechanisms of Costimulation

描述（由申请人提供）：针对显性肿瘤抗原（TA）的T细胞应答可以杀死肿瘤细胞，但对免疫原性差（亚显性）TA的有效性较低。因此，需要策略来诱导针对显性和亚显性TA的有效且持久的T细胞应答。Toll样受体（TLR）激动剂通过刺激抗原呈递细胞（APC）上的TLR来帮助产生有效的抗肿瘤T细胞应答。这些受体的刺激诱导炎性细胞因子的产生并增加最佳T细胞活化所必需的共刺激配体的表达水平。尽管TLR对APC的作用令人惊讶地清楚，但关于TLR接合对CD 8 T细胞的影响知之甚少。我们的研究小组已经产生了新的数据，表明TLR 2与TA特异性CD 8 T细胞的结合增加了T细胞增殖。TLR 2刺激也会增加IFN-？，颗粒酶B和穿孔素产生，并在体外用免疫原性差的TA活化后增强细胞溶解活性。用肿瘤反应性CD 8 T细胞和TLR 2配体的过继性T细胞转移（ACT）治疗荷瘤小鼠（野生型或TLR 2敲除）诱导已建立的肿瘤消退并产生对各种TA的从头T细胞应答。相反，用TLR 2配体和TLR 2敲除（-/-）CD 8 T细胞治疗确实促进显著的肿瘤消退。我们的假设是激活TA特异性CD 8 T细胞中的TLR 2信号通过增强对弱免疫原性TA的应答而导致有效和长期的抗肿瘤活性。该提议的第一个目的是实现对CD 8 T细胞中激活TLR 2信号如何增强对免疫原性差的TA的激活的机理理解。第二个目的是确定TLR 2连接的CD 8 T细胞的体内细胞和抗肿瘤应答。具体目标是：（1）定义CD 8 T细胞中TLR 2信号通过其增强对免疫原性差的肿瘤抗原的活化的信号传导途径。(2)确定TLR 2刺激的CD 8 T细胞在体内用免疫原性差的肿瘤抗原活化后的应答，包括扩增/收缩动力学、活化标志物的动力学表达和CTL效应子功能。(3)确定TLR 2刺激的CD 8 T细胞对有效抗肿瘤应答的发展和新肿瘤特异性T细胞的诱导的作用。我们将使用生理学相关的小鼠模型来评估TLR 2刺激的识别小鼠TA gp 100的TA特异性CD 8 T细胞（称为pmel T细胞）的应答。我们还将检查TLR 2-/- pmel和缺乏TLR 2信号转导过继分子MyD 88的pmel T细胞的抗肿瘤应答。此外，我们将确定TA特异性T细胞的抗肿瘤作用，这些T细胞被工程化以过表达TLR 2或MyD 88。我们设想这些研究将通过更好地理解增强T细胞活化为弱免疫原性TA的分子信号，为开发有效的基于T细胞的抗癌疗法提供可能的新方法。 公共卫生相关性：了解诱导和维持有效免疫应答的分子信号对于开发有效疫苗至关重要。我们试图了解肿瘤特异性T细胞中Toll样受体MyD 88信号如何有助于诱导和长期维持有效的抗肿瘤T细胞应答。有了这些信息，我们希望开发针对多种癌症的免疫疗法。

DESCRIPTION (provided by applicant): T cell responses against dominant tumor antigens (TA) can kill tumor cells but are less effective against poorly immunogenic (subdominant) TAs. Therefore, strategies are needed to induce potent and long-lasting T cell responses against dominant and subdominant TAs. Toll-like receptor (TLR) agonists help to generate potent antitumor T cell responses by stimulating TLRs on antigen presenting cells (APCs). Stimulation of these receptors induces the production of inflammatory cytokines and increases the expression levels of costimulatory ligands necessary for optimal T cell activation. Whereas the roles for TLRs on APCs are clear surprisingly, little is known about the effects of TLR engagement on CD8 T cells. Our group has generated new data demonstrating that TLR2 engagement on TA-specific CD8 T cells increases T cell proliferation. TLR2 stimulation also increases IFN-?, granzyme B, and perforin production and boosts cytolytic activity following activation with poorly immunogenic TAs in vitro. Treatment of tumor-bearing mice (wild type or TLR2 knock out) with adoptive T cell transfer (ACT) of tumor-reactive CD8 T cells and TLR2 ligand induces the regression of established tumors and generates de novo T cell responses to various TAs. In contrast, treatment with TLR2 ligand and TLR2 knock out (-/-) CD8 T cells does promote significant tumor regression. Our hypothesis is that activating TLR2 signals in TA-specific CD8 T cells leads to potent and long-lived antitumor activity by potentiating responses to weakly immunogenic TAs. The first objective of this proposal is to achieve a mechanistic understanding of how activating TLR2 signals in CD8 T cells enhances activation to poorly immunogenic TAs. The second objective is to determine the in vivo cellular and antitumor responses of TLR2-ligated CD8 T cells. The specific aims are: (1) Define the signaling pathway through which TLR2 signals in CD8 T cells potentiate activation to poorly immunogenic tumor antigens. (2) Determine the responses of TLR2-stimulated CD8 T cells following activation with a poorly immunogenic tumor antigen in vivo, including the expansion/contraction kinetics, kinetic expression of activation markers, and CTL effector function. (3) Determine the effect of TLR2- stimulated CD8 T cells on the development of effective antitumor responses and the induction of new tumor-specific T cells. We will use a physiologically-relevant mouse model to evaluate the responses of TLR2- stimulated TA-specific CD8 T cells that recognize the mouse TA gp100, referred to as pmel T cells. We will also examine the antitumor responses of TLR2-/- pmel and pmel T cells lacking the TLR2 signaling adopter molecule MyD88. In addition, we will determine the antitumor effects of TA-specific T cells engineered to overexpress TLR2 or MyD88. We envision these studies will make possible new approaches for the development of effective T cell-based therapies against cancer through a greater understanding of molecular signals that enhance T cell activation to weakly immunogenic TAs. PUBLIC HEALTH RELEVANCE: Understanding the molecular signals that induce and maintain potent immune responses is critical for developing effective vaccines. We seek to understand how Toll-like receptor-MyD88 signals in tumor-specific T cells contribute to the induction and long-term maintenance of effective anti-tumor T cell responses. With this information, we hope to develop immunotherapies against many forms of cancer.