Melanoma vaccines: the paradox of T cell activation without clinical response
Melanoma vaccines: the paradox of T cell activation without clinical response
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DOI：
10.1007/pl00014052
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发表时间：
2000-06-01
影响因子：
3
通讯作者：
Marincola, FM
中科院分区：
文献类型：
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作者：
Nielsen, MB;Marincola, FM
近年来，从 T 细胞识别的黑色素瘤抗原 (MA) 的识别中，对黑色素瘤免疫生物学的理解取得了重大进展。 MA 由细胞内蛋白组成，这些蛋白在癌细胞表面表达，与人类白细胞抗原 (HLA) I 类分子相关，因此是细胞毒性 T 淋巴细胞 (CTL) 的合适靶标。已经实施了几种新的监测策略来评估疫苗诱导的 T 细胞在外周循环以及肿瘤部位的激活和定位状态，包括有限稀释、体外致敏和 ELISPOT。先前旨在监测接受疫苗接种的患者的研究主要使用这三种方法。这些方法已证明抗原特异性疫苗接种可以引发免疫患者外周血中可检测到的免疫反应。然而，这些检测方法因需要 T 细胞体外扩增（有限稀释或体外致敏）或有限的灵敏度 (ELISPOT) 而存在缺陷。最近，有人提出使用可溶性 HLA/肽复合物四聚体、细胞内荧光激活细胞分选 (FACS) 分析和实时聚合酶链式反应 (PCR) 来监测疫苗试验。这些方法具有允许直接计数相关样品（例如外周血淋巴细胞、淋巴结和肿瘤）中特定表位特异性的 T 细胞的吸引力。我们正在评估将 HLA/肽四聚体 (tHLA) 与基于 Taqman 的实时逆转录 (RT)-PCR 和细胞内 FACS 分析相结合是否可以建立一种直接、全面的策略来评估体内表位特异性免疫反应。然而，在接近肿瘤微环境或外周血淋巴细胞的条件下，由于肿瘤或抗原呈递细胞对 T 细胞的直接刺激，预计 T 细胞活化状态会不同。我们观察到，在接受 MA 特异性疫苗的患者的外周血中很容易检测到活化的 T 细胞。然而，当 T 细胞受到相关表位刺激时，T 细胞受体会发生高水平下调，从而无法直接用 tHLA 识别疫苗特异性 T 细胞。因此，通过细胞内 FACS 和基于 Taqman 的实时 RT-PCR 等功能方法，可以更有效地对肿瘤部位的表位特异性 T 细胞进行评估，其中它们可能受到与肿瘤细胞和/或大量外周血单核细胞相互作用的刺激。
In recent years significant progress in the understanding of the immune biology of melanoma has evolved from the identification of melanoma antigens (MAs) recognized by T cells. MAs consist of intracellular proteins that are expressed on the surface of cancer cells in association with human leukocyte antigen (HLA) class I molecules and therefore are suitable targets for cytotoxic T lymphocytes (CTLs). Several new monitoring strategies have been implemented to evaluate the status of activation and localization of vaccine-induced T cells in the peripheral circulation as well as the tumor site, including limiting dilution, in vitro sensitization, and ELISPOT. Previous studies aimed at monitoring patients receiving vaccination have utilized mainly those three methods. These methods have demonstrated that antigen-specific vaccination can elicit immune responses detectable in the peripheral blood of immunized patients. These assays, however, have been faulted by their requirement for in vitro expansion of T cells (limiting dilution or in vitro sensitization) or for limited sensitivity (ELISPOT). More recently, the use of soluble HLA/peptide complex tetramers, intracellular fluorescence-activated cell sorting (FACS) analysis, and real-time polymerase chain reaction (PCR) has been proposed for the monitoring of vaccine trials. These methods have the appeal of allowing direct enumeration of T cells specific for a particular epitope within relevant samples such as peripheral blood lymphocytes, lymph nodes, and tumors. We are evaluating whether utilizing a combination of HLA/peptide tetramer (tHLA) together with Taqman-based real-time reverse-transcription (RT)-PCR and intracellular FACS analysis could establish a direct and comprehensive strategy for the assessment of epitope-specific immune response in vivo. In conditions close to those of the tumor microenviroment or in peripheral blood lymphocytes, however, a different status of T cell activation call be expected due to a direct stimulation of T cells by tumor or antigen-presenting cells. We observed that activated T cells can easily be detected ill the peripheral blood of patients who have received MA-specific vaccines. However, when T cells are stimulated with their relevant epitope, a high level of T cell receptor downregulation occurs that does not allow identification of vaccine-specific T cells directly with tHLA. Thus evaluation of epitope-specific T cells at the tumor site, where they might be exposed to stimulation by interaction with tumor cells and/or in bulk peripheral blood mononuclear cells, might be more efficiently analyzed with functional methods such as intracellular FACS and Taqman-based real time RT-PCR.