热休克蛋白gp96与肿瘤免疫研究进展

热休克蛋白gp96作为分子伴侣参与了肿瘤抗原向MHC-I类分子途径的递呈过程,并与抗原肽形成gp96-肽复合物激活CD8 ^＋T淋巴细胞,产生抗肿瘤的特异性免疫反应.此外,还能不依赖于抗原肽通过激活NF-κB信号转导,产生细胞因子和趋化因子,诱导树突状细胞成熟等多种作用而调节非特异性免疫反应.gp96-肽复合物疫苗为肿瘤的免疫治疗提供了新的思路.     

热休克蛋白gp96与肿瘤免疫研究进展

热休克蛋白gp96作为分子伴侣参与了肿瘤抗原向MHC-I类分子途径的递呈过程,并与抗原肽形成gp96-肽复合物激活CD8+T淋巴细胞,产生抗肿瘤的特异性免疫反应。此外,还能不依赖于抗原肽通过激活NF-κB信号转导,产生细胞因子和趋化因子,诱导树突状细胞成熟等多种作用而调节非特异性免疫反应。gp96-肽复合物疫苗为肿瘤的免疫治疗提供了新的思路。     

热休克蛋白与肿瘤免疫

热休克蛋白 (HSPs)作为分子伴侣参与蛋白的合成、折叠、装配、运输和降解。许多肿瘤细胞表面可以高表达HSPs ,它能与癌基因、抑癌基因产物结合。现认为HSPs具有伴移抗原肽的作用 ,肿瘤组织中提取的HSP—肽复合物可以作为肿瘤排斥抗原 ,诱导肿瘤特异性免疫 ,产生特异细胞毒性T细胞 (CTL) ,特异杀伤肿瘤细胞。这种作用在同种间不受MHC 1类分子限制 ,具有很好的临床应用前景。本文主要综述HSP—肽复合物与肿瘤免疫的相关进展。     

热休克蛋白与肿瘤的免疫治疗

热休克蛋白是在细胞内广泛分布、高度保守的蛋白质分子,能与细胞内多种肽分子结合,通过抗原提呈细胞上的受体,将抗原肽经MHCⅠ类途径传递给CD8~ 的细胞毒T细胞,诱导特异性抗肿瘤免疫应答。HSP与肿瘤的关系已成为当前研究的热点之一,热休克蛋白肽复合物作为一种肿瘤疫苗,在肿瘤治疗方面具有广阔的应用前景。     

树突状细胞肿瘤疫苗的研究进展

树突状细胞(DC)是目前发现的功能最强大的专职抗原递呈细胞(APC),能激活静息T细胞并使其增殖,产生抗原特异性细胞毒性T淋巴细胞(CTL),从而发挥抗肿瘤免疫效应.近年来,人们在肿瘤疫苗的研究中,采用多种策略制备DC肿瘤疫苗,尝试通过改变机体免疫系统对肿瘤的免疫状态来加强机体的免疫功能,进而清除肿瘤细胞,而对正常组织几乎无伤害,因此有很好的临床应用前景.     

肿瘤疫苗的研究进展

肿瘤疫苗是用肿瘤细胞、肿瘤细胞裂解物或肿瘤抗原激活机体免疫系统产生特异性抗肿瘤细胞免疫效应.它是一种治疗性的、新型的肿瘤治疗方法,也是一种主动性免疫疗法.随着肿瘤免疫学和分子生物学的发展,肿瘤与机体之间的相互作用、肿瘤免疫耐受以及肿瘤抗原鉴定都取得了很大的进展,这也促进了肿瘤疫苗的发展.     

体外构建的HSP70-肝癌抗原肽诱导抗原肽特异性免疫反应1

目的研究体外构建的HSP70-肝癌抗原肽复合物诱导针对肝癌的特异性免疫反应能力,为该复合物的临床应用奠定基础.方法在体外构建HSP70-肝癌抗原肽复合物,联合应用粒/巨细胞集落刺激因子(GM-CSF)及白介素-4(IL-4)直接从志愿者外周血中培养出DC;以HSP70、HSP70-肝癌抗原肽、抗原肽分别刺激DC,DC激活同源的T淋巴细胞产生细胞毒性T淋巴细胞(CTL),检测其杀伤T2细胞和肝癌细胞系的能力.结果HSP70-抗原肽、抗原肽均可诱导CD8+的抗原肽特异性CTL,而前者的诱导效果更强.结论体外构建的HSP70-抗原肽复合物具有免疫原性,HSP70可以增强抗原肽诱导特异性免疫反应的能力,HSP70-抗原肽复合物有可能作为肽疫苗用于临床肿瘤免疫治疗.     

肿瘤抗原肽研究新进展

肿瘤抗原肽的寻找已成为当前肿瘤研究领域的一大热点。它包括癌基因蛋白抗原肽、致癌病毒基因抗原肽、肿瘤特异性抗原肽和组织特异性分化抗原肽等。这些抗原肽在与MHC类分子结合后 ,提呈到细胞表面被相应T细胞受体识别 ,从而激活细胞毒性T淋巴细胞的活性 ,使机体产生特异性抗肿瘤免疫应答。因而它们在肿瘤免疫接种和免疫治疗等方面有着广阔的应用前景。     

肿瘤源性热休克蛋白gp96诱导淋巴细胞反应及其抗肿瘤效应

目的：研究肿瘤细胞来源的热休克蛋白gp96-多肽复合物在体外诱导脾淋巴细胞的特异性细胞毒性T淋巴细胞（CTL）反应.方法：利用蛋白纯化技术、SDS-PAGE凝胶电泳及Western blot法分离纯化、鉴定gp96-多肽;通过流式细胞术、免疫荧光技术、CCK-8法等检测经gp96多肽诱导的CD8^＋T细胞及其抗肿瘤效应.结果：经鉴定获得纯化的热休克蛋白;流式细胞仪检测表明,经gp96-肽复合物诱导后的CD8^＋T细胞比例达到近70%,远远高于对照组的35%、26%;该活化的CTL细胞在效靶比为50：1时的肿瘤杀伤率达72%,与对照组相比具有统计学意义;激光共聚焦显微镜观察证实实验诱导组的培养上清能诱导H22肿瘤细胞凋亡的形态学改变.结论：肿瘤来源的热休克蛋白gp96-肽复合物能诱导小鼠脾淋巴细胞的CTL反应,该活化的CTL具有特异性抗H22肿瘤细胞的免疫作用,并能分泌免疫活性物质诱导H22肿瘤细胞凋亡.     

肿瘤疫苗治疗膀胱癌进展

肿瘤疫苗免疫治疗是利用肿瘤抗原进行主动免疫来激发、增强机体的主动特异性免疫反应.肿瘤疫苗的设计,首先是基于对肿瘤发生免疫逃逸机理的认识.肿瘤免疫逃逸机制十分复杂,缺乏抗原表位、MHC表达下调以及共刺激分子或某些粘附分子的缺乏等可能是其重要的机理.肿瘤疫苗策略包括基因疫苗、肽和蛋白疫苗、基因修饰的肿瘤细胞疫苗以及抗独特型抗体疫苗等.利用DC细胞荷载抗原肽或者基因修饰的肿瘤细胞等建立膀胱癌细胞疫苗,在体内、外实验中已证实对膀胱癌的治疗有一定的效果.     

Immunity to cancer: attack and escape in T lymphocyte–tumor cell interaction

Summary: Tumor cells may express antigens which are recognized in a form of HLA/peptide complexes by T cells. The frequency at which different antigens are seen by T cells of melanoma patients and healthy donors was evaluated by human leukocyte antigen (HLA)/peptide tetramer technology which stains T cells bearing the specific receptor for a given epitope. By this technique, it was found that the majority of metastatic melanoma patients can recognize differentiation antigens (particularly Melan‐A/MART‐1), whereas such a recognition is scanty in the early phase of the disease and in healthy subjects. Despite the presence of melanoma‐specific T cells infiltrating tumor lesions, tumor rejection rarely occurs. Among the different mechanisms of such inefficient antitumor response, this review discusses the possible anti‐T‐cell counterattack mediated by FasL‐positive tumor cells, and shows that FasL is located in the cytoplasm of melanoma cells and is transported in the tumor microenvironment through the release of melanosomes. Additionally, mechanisms of suboptimal T cell activation through tumor cell expression of peptide analogs with antagonist activity are described, together with the possibility of overcoming such anergy induction by the usage of optimized tumor epitopes. Down‐modulation of HLA expression by target tumor cells and its multiple mechanisms is also considered. Finally, we discuss the role of inducible nitric oxide synthases in determining the inhibition of apoptosis in melanoma cells, which can make such tumor cells resistant to the T‐cell attack.     

New approaches to dissect degeneracy and specificity in T cell antigen recognition

The acquired immune system is a complex and very effective defense against invading pathogens such as bacteria and viruses. T cells are central to the acquired immune system by controlling B and T cell activation and induction of T cell effector functions. The key event for T cell activation is the recognition of a specific antigen by the T cell receptor. During the past decade antigen recognition of T cells has been investigated intensively leading to new insights into the molecular mechanisms of T cell activation. In addition to the resolution of the molecular structure of the trimolecular complex (T cell receptor, peptide, major histocompatibility complex) functional studies have demonstrated the flexibility of the T cell receptor interaction with its ligand. These observations have had strong implications for the understanding of T cell selection, maturation, and repertoire maintenance. In addition, the flexibility of the T cell receptor has provided the basis for novel methods to dissect antigen recognition and define the repertoire of ligands for a given receptor. Here, we summarize recent progress on T cell recognition and method innovations with respect to future studies in autoimmune diseases.     

MUC1-specific anti-tumor responses: molecular requirements for CD4-mediated responses

MUC1 was first defined as a tumor antigen in the late 1980s, yet little is known about the types of immune responses that mediate rejection of MUC1(+) tumors in vivo. MUC1-specific antibodies, T(h) cells and cytotoxic T cells can be detected in patients with different adenocarcinomas, yet these tumors usually progress. Thus, there is a need to better understand the in vivo mechanisms of antigen-specific tumor rejection. To characterize the nature of MUC1-specific immune responses in vivo, rejection of a MUC1-expressing melanoma tumor line (B16.MUC1) was evaluated in mice lacking specific T cell subsets, cytokines, co-stimulatory molecules or molecular effectors of cytolytic pathways. Results demonstrated that rejection of the B16.MUC1 tumor cell line was primarily mediated by CD4(+) T cells, and required Fas ligand, lymphotoxin-alpha, CD40, CD40 ligand and CD28, but not perforin, gammadelta T cells, IL-4, IL-10, IL-12 or tumor necrosis factor receptor-1. Depletion of NK cells demonstrated that NK cells might also contribute to MUC1 immunity in the B16.MUC1 tumor model. These results demonstrated that the immune response generated against MUC1 does not fit the type 1 or 2 model described for many immune responses. Additionally, multiple cytolytic mechanisms are required for B16.MUC1 rejection.     

HLA class I antigen expression in malignant cells: why does it not always correlate with CTL-mediated lysis?

HLA class I antigen defects are frequently found in malignant cells. They appear to play a role in the clinical course of the disease, probably because they provide tumor cells with a mechanism to escape cytotoxic T lymphocyte (CTL) recognition and destruction. Expression of HLA class I antigens, however, is not always associated with the susceptibility of tumor cells to CTL lysis. Many mechanisms may underlie this finding, including the lack of tumor antigen (TA)-derived peptide presentation by a given HLA class I allospecificity, and/or the expression of immunosuppressive molecules such as HLA-G. These findings emphasize the need to develop probes to measure HLA class I allospecificity-TA peptide complex expression in malignant cells. Furthermore, the evaluation of the role of HLA class I antigens in the interaction of malignant cells with host immune cells should take into account the potential interference of tumor-derived immunomodulators.     

T cell avidity and tumor recognition: implications and therapeutic strategies

In the last two decades, great advances have been made studying the immune response to human tumors. The identification of protein antigens from cancer cells and better techniques for eliciting antigen specific T cell responses in vitro and in vivo have led to improved understanding of tumor recognition by T cells. Yet, much remains to be learned about the intricate details of T cell – tumor cell interactions. Though the strength of interaction between T cell and target is thought to be a key factor influencing the T cell response, investigations of T cell avidity, T cell receptor (TCR) affinity for peptide-MHC complex, and the recognition of peptide on antigen presenting targets or tumor cells reveal complex relationships. Coincident with these investigations, therapeutic strategies have been developed to enhance tumor recognition using antigens with altered peptide structures and T cells modified by the introduction of new antigen binding receptor molecules. The profound effects of these strategies on T cell – tumor interactions and the clinical implications of these effects are of interest to both scientists and clinicians. In recent years, the focus of much of our work has been the avidity and effector characteristics of tumor reactive T cells. Here we review concepts and current results in the field, and the implications of therapeutic strategies using altered antigens and altered effector T cells.     

In vivo activation of melanoma-specific CD8(+) T cells by endogenous tumor antigen and peptide vaccines. A comparison to virus-specific T cells

Many new types of vaccines against infectious or malignant diseases are currently being proposed. Careful characterization of the induced immune response is required in assessing their efficiency. While in most studies human tumor antigen-specific T cells are analyzed after in vitro re-stimulation, we investigated these T cells directly ex vivo using fluorescent tetramers. In peripheral blood lymphocytes from untreated melanoma patients with advanced disease, a fraction of tumor antigen (Melan-A/MART-1)-specific T cells were non-naive, thus revealing tumor-driven immune activation. After immunotherapy with synthetic peptides plus adjuvant, we detected tumor antigen-specific T cells that proliferated and differentiated to memory cells in vivo in some melanoma patients. However, these cells did not present the features of effector cells as found in cytomegalovirus specific T cells analyzed in parallel. Thus, peptide plus adjuvant vaccines can lead to activation and expansion of antigen specific CD8(+) T cells in PBL. Differentiation to protective CD8(+) effector cells may, however, require additional vaccine components that stimulate T cells more efficiently, a major challenge for the development of future immunotherapy.     

Targeting HLA class I expression to increase tumor immunogenicity

The dynamic interaction between the host immune system and growing cancer has been of central interest to the field of tumor immunology over the past years. Recognition of tumor-associated antigens (TAA) by self-HLA (human leukocyte antigen) class I-restricted CD8+ T cells is a main feature in the detection and destruction of malignant cells. The discovery and molecular characterization of TAA has changed the field of cancer treatment and introduced a new era of cancer immunotherapy aimed at increasing tumor immunogenicity and T-cell-mediated anti-tumor immunity. Unfortunately, while these new protocols of cancer immunotherapy are mediating induction of tumor-specific T lymphocytes in patients with certain malignancies, they have not yet delivered substantial clinical benefits, such as induction of tumor regression or increased disease-free survival. It has become apparent that lack of tumor rejection is the result of immune selection and escape by tumor cells that develop low immunogenic phenotypes. Substantial experimental data support the existence of a variety of different mechanisms involved in the tumor escape phase, including loss or downregulation of HLA class I antigens. These alterations could be caused by regulatory ('soft') or by structural/irreversible ('hard') defects. On the basis of the evidence obtained from experimental mouse cancer models and metastatic human tumors, the structural defects underlying HLA class I loss may have profound implications on T-cell-mediated tumor rejection and ultimately on the outcome of cancer immunotherapy. Strategies to overcome this obstacle, including gene therapy to recover normal expression of HLA class I genes, require consideration. In this review, we outline the importance of monitoring and correction of HLA class I alterations during cancer development and immunotherapy.     

Involvement of CD91 and scavenger receptors in Hsp70‐facilitated activation of human antigen‐specific CD4+ memory T cells

Hsp70 plays several roles in the adaptive immune response. Based on the ability to interact with diverse peptides, extracellular Hsp70:peptide complexes exert profound effects both in autoimmunity and in tumor rejection by evoking potent T cell responses to the chaperoned peptide. The interaction with receptors on APC represents the basis for the immunological functions of Hsp70 and a critical point where the immune response can be regulated. Various surface proteins (e.g. CD91, scavenger receptors (SR)) have been implicated in binding of Hsp70. In this study, antigenic peptides from tetanus toxin and influenza hemagglutinin complexed to human stress‐inducible Hsp70 were found to enhance the proliferation and cytokine production of human antigen‐specific CD4⁺ T cells. This was demonstrated in proliferation experiments using human monocytes as APC. Proliferated antigen‐specific cells were detected combining HLA‐DRB1^*0401 or HLA‐DRB1^*1101 tetramer and CFSE staining. Treating monocytes with CD91 siRNA diminished these effects. Additional blocking of SR by the SR ligand fucoidan completely abolished enhanced proliferation and production of Th1 and Th2 cytokines. Taken together, our data indicate that in the human system, CD91 and members of the SR family efficiently direct Hsp70:peptide complexes into the MHC class II presentation pathway and thus enhance antigen‐specific CD4⁺ T cell responses.     

Regulatory T-cell response and tumor vaccine-induced cytotoxic T lymphocytes in human melanoma

A role of CD4(+) cells in the regulation of immune responses has steadily gained renewed recognition. The understanding of these T-regulatory (T-reg) cells in the generation of antitumor cytolytic T lymphocyte (CTL) response is therefore important. It has been shown that immunization with specific peptides, DNA, or tumor lysate-based vaccines can induce CTL responses in vivo. We have immunized melanoma patients with major histocompatibility complex (MHC) class I restricted peptide- or melanoma tumor lysate-loaded antigen-presenting cell (APC)-based vaccines and have monitored the generation of CTL responses and T-reg cell responses, if any. Using tetramer staining and limiting dilution analyses as monitors of CTL responses, we found significant increases in the number of antigen-specific CTL in circulation after vaccination with the MART-1(27-35) peptide (AAGIGILTV)-pulsed autologous APC, the MAGE-1(161-169) peptide (EADPTGHSY)-pulsed APC, or with autologous tumor lysate-pulsed APC. The antigen-specific CTL reached the peak expansion by day 7 and then declined to the prevaccine levels by day 28. The decline in the CTL response was associated by a concomitant expansion of CD4(+) CD25(+)T cells. Analysis of postvaccine peripheral blood lymphocytes (PBL) from patients showed an increased amount of interleukin (IL)-10 secretion on in vitro stimulation with IL-2 after successive vaccination. Triple color flow cytometric analyses revealed cytoplasmic IL-10 in the CD4(+)CD25(+) T-cell fraction and the number of CD4(+)CD25(+) IL-10(+) T cells were found to increase significantly in postvaccine PBL. These observations have implications in tumor antigen and APC/dendritic cell (DC)-based cancer vaccine strategies.     

Dendritic Cell-Derived Exosomes Stimulate Stronger CD8~+ CTL Responses and Antitumor Immunity than TVimor Cell-Derived Exosomes

Exosomes (EXO) derived from dendritic cells (DC) and tumor cells have been used to stimulate antitumor immune responses in animal models and in clinical trials. However, there has been no side-by-side comparison of the stimulatory efficiency of the antitumor immune responses induced by these two commonly used EXO vaccines. In this study, we selected to study the phenotype characteristics of EXO derived from a transfected EG7 tumor cells expressing ovalbumin (OVA) and OVA-pulsed DC by flow cytometry. We compared the stimulatory effect in induction of OVA-specific immune responses between these two types of EXO. We found that OVA protein-pulsed DCovA-derived EXO (EXODC) can more efficiently stimulate naive OVA-specific CD8+ T cell proliferation and differentiation into cytotoxic T lymphocytes in vivo, and induce more efficient antitumor immunity than EG7 tumor cell-derived EXO (EXOEG7). In addition, we elucidated the important role of the host DC in EXO vaccines that the stimulatory effect of EXO is delivered to T cell responses by the host DC. Therefore, DC-derived EXO may represent a more effective EXO-based vaccine in induction of antitumor immunity.