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

描述(由申请人提供)：针对主要肿瘤抗原(TA)的T细胞反应可以杀死肿瘤细胞，但对免疫原性较差(次要)的TA效果较差。因此，需要一些策略来诱导针对显性和次显性TA的强大而持久的T细胞反应。Toll样受体(Toll-like Receptor，TLR)激动剂通过刺激抗原提呈细胞(APC)上的TLRs，帮助产生强大的抗肿瘤T细胞反应。这些受体的刺激诱导炎性细胞因子的产生，并增加共刺激配体的表达水平，这是最佳T细胞激活所必需的。令人惊讶的是，尽管TLRs在APC上的作用是明确的，但TLR参与对CD8T细胞的影响却知之甚少。我们的团队已经产生了新的数据，表明TLR2与TA特异性CD8 T细胞的结合可以促进T细胞的增殖。在免疫原性较差的TA激活后，TLR2的刺激也增加了干扰素-β、颗粒酶B和穿孔素的产生，并增强了细胞溶解活性。用肿瘤反应性CD8T细胞和TLR2配体过继T细胞转移(ACT)治疗荷瘤小鼠(野生型或TLR2基因敲除)，可诱导已建立的肿瘤消退，并对各种TA产生新的T细胞应答。相比之下，TLR2配体和TLR2敲除(-/-)CD8 T细胞的治疗确实促进了显著的肿瘤消退。我们的假设是，激活TA特异性CD8T细胞中的TLR2信号，通过增强对弱免疫原性TA的反应，导致强大而持久的抗肿瘤活性。这项建议的第一个目标是从机制上理解激活CD8T细胞中的TLR2信号如何增强对免疫原性较差的TA的激活。第二个目的是确定TLR2连接的CD8T细胞的体内细胞和抗肿瘤反应。其具体目的是：(1)明确CD8T细胞中TLR2信号增强对低免疫原性肿瘤抗原的激活的信号通路。(2)检测TLR2刺激的CD8T细胞在低免疫原性肿瘤抗原激活后的体内反应，包括扩/收缩动力学、激活标志物的动力学表达和CTL效应功能。(3)检测TLR2刺激的CD8T细胞在产生有效的抗肿瘤反应和诱导新的肿瘤特异性T细胞方面的作用。我们将使用一个生理相关的小鼠模型来评估TLR2刺激的TA特异性CD8 T细胞识别小鼠TA gp100的反应，称为PMEL T细胞。我们还将检测TLR2-/-PMEL和缺乏TLR2信号转导分子MyD88的PMEL T细胞的抗肿瘤反应。此外，我们还将确定过表达TLR2或MyD88的TA特异性T细胞的抗肿瘤作用。我们预计，这些研究将通过更好地了解增强T细胞对弱免疫原性TA的激活的分子信号，为开发有效的基于T细胞的抗癌治疗提供可能的新方法。与公共卫生相关：了解诱导和维持有效免疫反应的分子信号对于开发有效的疫苗至关重要。我们试图了解肿瘤特异性T细胞中的Toll样受体MyD88信号如何有助于诱导和长期维持有效的抗肿瘤T细胞反应。有了这些信息，我们希望开发出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.