Identification of novel human CTL epitopes and their agonist epitopes of mesothelin.

PURPOSE: Mesothelin is overexpressed in many pancreatic and ovarian cancers, mesotheliomas, and other tumor types. Clinical trials are ongoing using immunotoxins to target mesothelin, and patients immunized with allogeneic pancreatic tumor cell lines have shown immune responses to previously defined mesothelin epitopes. The purpose of this study was to define novel mesothelin CTL epitopes and, more importantly, agonist epitopes that would more efficiently activate human T cells to more efficiently lyse human tumors. EXPERIMENTAL DESIGN AND RESULTS: Two novel mesothelin HLA-A2 epitopes were defined. T-cell lines generated from one of these epitopes were shown to lyse pancreatic and ovarian tumor cells. Several agonist epitopes were defined and were shown to (a) have higher affinity and avidity for HLA-A2, (b) activate mesothelin-specific T cells from normal individuals or cancer patients to a greater degree than the native epitope in terms of induction of higher levels of IFN-gamma and the chemokine lymphotactin, and (c) lyse several mesothelin-expressing tumor types in a MHC-restricted manner more effectively than T cells generated using the native peptide. External beam radiation of tumor cells at nontoxic levels was shown to enhance the expression of mesothelin and other accessory molecules, resulting in a modest but statistically significant increase in tumor cell lysis by mesothelin-specific T cells. CONCLUSIONS: The identification of novel CTL agonist epitopes supports and extends observations that mesothelin is a potential target for immunotherapy of pancreatic and ovarian cancers, as well as mesotheliomas.     

Identification of HLA-A2-restricted CTL epitopes of a novel tumour-associated antigen, KIF20A, overexpressed in pancreatic cancer

Background:

Identification of tumour-associated antigens (TAAs) that induce cytotoxic T lymphocytes (CTLs) specific to cancer cells is critical for the development of anticancer immunotherapy. In this study, we aimed at identifying a novel TAA of pancreatic cancer for immunotherapy.

Methods:

On the basis of the genome-wide cDNA microarray analysis, we focused on KIF20A (also known as RAB6KIFL/MKlp2) as a candidate TAA in pancreatic cancer cells. The HLA-A2 (A*02:01)-restricted CTL epitopes of KIF20A were identified using HLA-A2 transgenic mice (Tgm) and the peptides were examined to check whether they could generate human CTLs exhibiting cytotoxic responses against KIF20A⁺, HLA-A2⁺ tumour cells in vitro.

Results:

KIF20A was overexpressed in pancreatic cancer and in some other malignancies, but not in their non-cancerous counterparts and many normal adult tissues. We found that KIF20A-2 (p12–20, LLSDDDVVV), KIF20A-8 (p809–817, CIAEQYHTV), and KIF20A-28 (p284–293, AQPDTAPLPV) peptides could induce HLA-A2-restricted CTLs in HLA-A2 Tgm without causing autoimmunity. Peptide-reactive human CTLs were generated from peripheral blood mononuclear cells of HLA-A2⁺ healthy donors by in vitro stimulation with the three peptides, and those CTLs successfully exhibited cytotoxic responses to cancer cells expressing both KIF20A and HLA-A2.

Conclusion:

KIF20A is a novel promising candidate for anticancer immunotherapeutic target for pancreatic cancers.     

Identification of HLA-A*0201-restricted CTL epitopes encoded by the tumor-specific MAGE-2 gene product

MAGE-2 is expressed in many tumors, including melanoma, laryngeal tumors, lung tumors and sarcomas, but not in healthy tissue, with the exception of testis. Thus, MAGE-2-derived peptides that bind to HLA class I molecules and elicit cytotoxic T lymphocyte (CTL) responses could be of significant therapeutic importance. In this study, we show that several MAGE-2-derived peptides bind with high affinity to HLA-A*0201. Three of them form complexes with HLA-A*0201 that are stable at 37°C and are immunogenic in HLA-A*0201K^b transgenic mice. Moreover, CTLs against 2 of them (M2 112-120, and M2 157-166) specifically recognize cells that express both the MAGE-2 protein and HLA-A*0201K^b. These 2 peptides are processed and presented in the context of HLA-A*0201. Therefore, these peptides are candidate components in peptide-based vaccines for the treatment and prevention of several types of MAGE-2-expressing cancers. Int. J. Cancer 73:125–130, 1997. © 1997 Wiley-Liss, Inc.     

HLA-A2-restricted CTL epitopes of a novel lung cancer-associated cancer testis antigen, cell division cycle associated 1, can induce tumor-reactive CTL

Toward the development of a novel cancer immunotherapy, we have previously identified several tumor-associated antigens (TAAs) and the epitopes recognized by human histocompatibility leukocyte (HLA)-A2/A24-restricted cytotoxic T lymphocyte (CTL). In this study, we tried to identify a TAA of lung cancer (LC) and its HLA-A2 restricted CTL epitopes to provide a target antigen useful for cancer immunotherapy of LC. We identified a novel cancer testis antigen, cell division cycle associated gene 1 (CDCA1), overexpressed in nonsmall cell LC using a cDNA microarray analysis. The expression levels of CDCA1 were also increased in the majority of small cell LC, cholangiocellular cancer, urinary bladder cancer and renal cell cancers. We used HLA-A2.1 transgenic mice to identify the HLA-A2 (A*0201)-restricted CDCA1 epitopes recognized by mouse CTL, and we investigated whether these peptides could induce CDCA1-reactive CTLs from the peripheral blood mononuclear cells (PBMCs) of HLA-A2-positive donors and a NSCLC patient. Consequently, we found that the CDCA1(65-73) (YMMPVNSEV) peptide and CDCA1(351-359) (KLATAQFKI) peptide could induce peptide-reactive CTLs in HLA-A2.1 transgenic mice. In HLA-A2(+) donors, in vitro stimulation of PBMC with these peptides could induce peptide-reactive CTLs which killed tumor cell lines endogenously expressing both HLA-A2 and CDCA1. As a result, CDCA1 is a novel cancer-testis antigen overexpressed in LC, cholangiocellular cancer, urinary bladder cancer and renal cell cancers, and CDCA1 may therefore be an ideal TAA useful for the diagnosis and immunotherapy of these cancers.     

原癌基因Bmi-1 B细胞抗原表位及 HLA I类限制性CTL表位的生物信息学分析

目的:预测原癌基因Bmi-1(B-cell-specific Moloney murine leukemia virus insertion site 1)的B细胞抗原表位及HLA I类限制性细胞毒性T细胞（cytotoxic T cell）表位。方法:采用Ellipro(http://tools.immuneepitope.org/ellipro/)预测Bmi-1蛋白中可能存在的线性B细胞表位和构象B细胞表位;采用ProtParam、NetCTL等软件和方法预测Bmi-1中可能存在的HLA I类限制性CTL表位。结果:Bmi-1蛋白中含有6个线性B细胞表位和8个构象B细胞表位;结合HLA结合力、蛋白酶体切割效率和TAP转运效率,经过NetCTL程序预测表明:针对不同的HLA I类分子,原癌基因Bmi-1中都存在多个HLA I类分子的限制性CTL表位。结论:综合运用多个程序预测了原癌基因Bmi-1中的B细胞抗原表位及HLA I类分子的限制性CTL表位,为下一步开展针对Bmi-1的免疫靶向治疗等研究打下了基础。     

Identification and translational validation of novel mammaglobin-A CD8 T cell epitopes

Mammaglobin-A (MAM-A) is a secretory protein that is overexpressed in 80 % of human breast cancers. Its near-universal expression in breast cancer as well as its exquisite tissue specificity makes it an attractive target for a breast cancer prevention vaccine, and we recently initiated a phase 1 clinical trial of a MAM-A DNA vaccine. Previously, we have identified multiple MAM-A CD8 T cell epitopes using a reverse immunology candidate epitope approach based on predicted binding, but to date no attempt has been made to identify epitopes using an unbiased approach. In this study, we used human T cells primed in vitro with autologous dendritic cells expressing MAM-A to systematically identify MAM-A CD8 T cell epitopes. Using this unbiased approach, we identified three novel HLA-A2-restricted MAM-A epitopes. CD8 T cells specific for these epitopes are able to recognize and lyse human breast cancer cells in a MAM-A-specific, HLA-A2-dependent fashion. HLA-A2⁺/MAM-A⁺ breast cancer patients have an increased prevalence of CD8 T cells specific for these novel MAM-A epitopes, and vaccination with a MAM-A DNA vaccine significantly increases the number of these CD8 T cells. The identification and translational validation of novel MAM-A epitopes has important implications for the ongoing clinical development of vaccine strategies targeting MAM-A. The novel MAM-A epitopes represent attractive targets for epitope-based vaccination strategies, and can also be used to monitor immune responses. Taken together these studies provide additional support for MAM-A as an important therapeutic target for the prevention and treatment of breast cancer.     

Analogues of CTL epitopes with improved MHC class-I binding capacity elicit anti-melanoma CTL recognizing the wild-type epitope

The MHC class-1 binding affinity of an epitope is an important parameter determining the immunogenicity of the peptide-MHC complex. In order to improve the immunogenicity of an epitope derived from melanocyte lineage-specific antigen gp 100, we performed amino-acid substitutions within the epitope and assayed both HLA-A*0201 binding and CTL recognition. Anchor replacements towards the HLA-A*0201 peptide-binding motif gave rise to peptides with higher HLA-A*0201 binding capacity compared to the wild-type epitope. In addition, several of the gp100 154–162 epitope-analogues were more efficient at target-cell sensitization for lysis by anti-gp100 154–162 CTL compared to the wild-type epitope. These altered gp100 154–162 epitopes were subsequently tested for their capacity to induce CTL responses in vivo using HLA-A*0201/K^b transgenic mice, and in vitro using HLA-A*0201⁺ donor-derived lymphocytes. Interestingly, the peptide-specific CTL obtained, which were raised against the different gp 100 154–162 epitope-analogues, displayed cross-reactivity with target cells endogenously processing and presenting the native epitope. These data demonstrate that altered epitopes can be exploited to elicit native epitope-reactive CTL. The use of epitope-analogues with improved immunogenicity may contribute to the development of CTL-epitope based vaccines in viral disease and cancer. Int. J. Cancer, 70:302–309, 1997. © 1997 Wiley-Liss, Inc.     

肿瘤抗原 CTL 表位修饰策略研究进展

肿瘤抗原 CTL 表位能诱导特异性的细胞毒性 T 淋巴细胞（cytotoxic T lymphocyte,CTL）杀伤肿瘤细胞,但是单一表位存在分子量小、免疫原性低等缺点。表位修饰可增加其分子量,提升其免疫原性,诱导更有效的肿瘤杀伤效应。CTL 表位修饰包括表位分子氨基酸残基的改造和引入修饰分子。改造天然表位的氨基酸残基改变了表位分子的氨基酸序列,但保留其特异的抗原性,并可提高表位呈递效率。常用的 CTL 表位修饰分子包括 Toll 样受体配体、C 型凝集素受体特异性抗体、β2微球蛋白、病毒样蛋白微粒等,其可改变表位构象,但保留表位特异的抗原性,提高表位呈递的靶向性,且能诱导特异性高、强度大的免疫反应。本文将对表位修饰的具体策略作一简要综述。     

Identification of HLA-A2- or HLA-A24-restricted CTL epitopes possibly useful for glypican-3-specific immunotherapy of hepatocellular carcinoma.

PURPOSE AND EXPERIMENTAL DESIGN: We previously reported that glypican-3 (GPC3) was overexpressed, specifically in hepatocellular carcinoma (HCC) and melanoma in humans, and it was useful as a novel tumor marker. We also reported that the preimmunization of BALB/c mice with dendritic cells pulsed with the H-2K(d)-restricted mouse GPC3(298-306) (EYILSLEEL) peptide prevented the growth of tumor-expressing mouse GPC3. Because of similarities in the peptide binding motifs between H-2K(d) and HLA-A24 (A*2402), the GPC3(298-306) peptide therefore seemed to be useful for the immunotherapy of HLA-A24+ patients with HCC and melanoma. In this report, we investigated whether the GPC3(298-306) peptide could induce GPC3-reactive CTLs from the peripheral blood mononuclear cells (PBMC) of HLA-A24 (A*2402)+ HCC patients. In addition, we used HLA-A2.1 (HHD) transgenic mice to identify the HLA-A2 (A*0201)-restricted GPC3 epitopes to expand the applications of GPC3-based immunotherapy to the HLA-A2+ HCC patients. RESULTS: We found that the GPC3(144-152) (FVGEFFTDV) peptide could induce peptide-reactive CTLs in HLA-A2.1 (HHD) transgenic mice without inducing autoimmunity. In five out of eight HLA-A2+ GPC3+ HCC patients, the GPC3(144-152) peptide-reactive CTLs were generated from PBMCs by in vitro stimulation with the peptide and the GPC3(298-306) peptide-reactive CTLs were also generated from PBMCs in four of six HLA-A24+ GPC3+ HCC patients. The inoculation of these CTLs reduced the human HCC tumor mass implanted into nonobese diabetic/severe combined immunodeficiency mice. CONCLUSION: Our study raises the possibility that these GPC3 peptides may therefore be applicable to cancer immunotherapy for a large number of HCC patients.     

低亲和力CTL表位肽在治疗性肿瘤疫苗中应用的研究

因为细胞毒性T淋巴细胞（cytotoxic T lymphocytes,CTLs）在肿瘤控制中起着重要作用,所以基于CTL表位（epitope）的治疗性肿瘤多肽疫苗已经成为当前肿瘤综合生物治疗中一个倍受瞩目的策略。传统的免疫治疗策略通常选择与MHC-Ⅰ类分子具有高亲和力的CTL表位肽作为治疗工具,但部分高亲和力的CTL表位肽在体内往往有免疫耐受或者副反应。近来研究表明：低亲和力的CTL表位肽及其改构体能很好地克服这些问题。本文就低亲和力CTL表位肽及其改构体在肿瘤免疫治疗中的研究进展做一综述。     

Spontaneous cytotoxic T-cell responses against survivin-derived MHC class I-restricted T-cell epitopes in situ as well as ex vivo in cancer patients

Recent advances in therapeutic tumor vaccinations necessitate the identification of broadly expressed, immunogenic tumor antigens that are not prone to immune selection. To this end, the human inhibitor of apoptosis, survivin, is a prime candidate because it is expressed in most human neoplasms but not in normal, differentiated tissues. Here, we demonstrate spontaneous cytotoxic T-cell responses against survivin-derived MHC class I-restricted T-cell epitopes in breast cancer, leukemia, and melanoma patients both in situ as well as ex vivo. Moreover, survivin-reactive T cells isolated by magnetic beads coated with MHC/peptide complexes were cytotoxic against HLA-matched tumors of different tissue types. Being a universal tumor antigen, survivin may serve as a widely applicable target for anticancer immunotherapy.     

Determination of cellularly processed HLA-A2402-restricted novel CTL epitopes derived from two cancer germ line genes, MAGE-A4 and SAGE.

PURPOSE: For identification of CTL epitopes useful for cancer vaccines, it is crucial to determine whether cognate epitopes are presented on the cell surface of target cancer cells through natural processing of endogenous proteins. For this purpose, we tried to use the cellular machinery of both mice and human to define naturally processed CTL epitopes derived from two "cancer germ line" genes, MAGE-A4 and SAGE. EXPERIMENTAL DESIGN: We vaccinated newly produced HLA-A2402 transgenic mice with DNA plasmids encoding target antigens. Following screening of synthesized peptides by splenic CD8(+) T cells of vaccinated mice, we selected candidate epitopes bound to HLA-A2402. We then examined whether human CD8(+) T cells sensitized with autologous CD4(+) PHA blasts transduced by mRNA for the cognate antigens could react with these selected peptides in an HLA-A2402-restricted manner. RESULTS: After DNA vaccination, murine CD8(+) T cells recognizing MAGE-A4(143-151) or SAGE(715-723) in an HLA-A2402-restricted manner became detectable. Human CTLs specific for these two peptides were generated after sensitization of HLA-A2402-positive CD8(+) T cells with autologous CD4(+) PHA blasts transduced with respective mRNA. CTL clones were cytotoxic toward tumor cell lines expressing HLA-A2402 and cognate genes. Taken together, these CTL epitopes defined in HLA-A24 transgenic mice are also processed and expressed with HLA-A2402 in human cells. The presence of SAGE(715-723)-specific precursors was observed in HLA-A2402-positive healthy individuals. CONCLUSIONS: Two novel HLA-A2402-restricted CTL epitopes, MAGE-A4(143-151) and SAGE(715-723), were identified. Our approach assisted by cellular machinery of both mice and human could be widely applicable to identify naturally processed CTL epitopes.     

H-2Kb-restricted CTL epitopes from mouse heparanase elicit an antitumor immune response in vivo

The identification of CTL epitopes from tumor antigens is very important for the development of peptide-based, cancer-specific immunotherapy. Heparanase is broadly expressed in various advanced tumors and can serve as a universal tumor-associated antigen. Although several epitopes of heparanase antigen are known in humans, the corresponding knowledge in mice is still rather limited. The present study was designed to predict and identify the CTL epitopes in the mouse heparanase protein. For this purpose, H-2K(b)-restricted CTL epitopes were identified by using the following four-step procedure: (a) a computer-based epitope prediction from the amino acid sequence of mouse heparanase, (b) a peptide-binding assay to determine the affinity of the predicted epitopes with the H-2K(b) molecule, (c) the testing of the induction of CTLs toward various carcinoma cells expressing heparanase antigens and H-2K(b), and (d) the induction of immunoprotection and immunotherapy in vivo. The results showed that, of the tested peptides, effectors induced by peptides of mouse heparanase at residue positions 398 to 405 (LSLLFKKL; mHpa398) and 519 to 526 (FSYGFFVI; mHpa519) lysed three kinds of carcinoma cells expressing both heparanase and H-2K(b) (B16 melanoma cells, EL-4 lymphoma cells, and Lewis lung cancer cells). In vivo experiments indicated that mHpa398 and mHpa519 peptides offered the possibility of not only immunizing against tumors but also treating tumor-bearing hosts successfully. Our results suggest that the mHpa398 and mHpa519 peptides are novel H-2K(b)-restricted CTL epitopes capable of inducing heparanase-specific CTLs in vitro and in vivo. These epitopes may serve as valuable tools for the preclinical evaluation of vaccination strategies.     

Identification and characterization of T-cell epitopes deduced from RGS5, a novel broadly expressed tumor antigen.

PURPOSE: Identification of tumor-associated antigens and advances in tumor immunology resulted in the development of vaccination strategies to treat patients with malignant diseases. In a novel experimental approach that combined comparative mRNA expression analysis of defined cell types with the characterization of MHC ligands by mass spectrometry, we found that regulator of G protein signaling 5 (RGS5) is extensively up-regulated in a broad variety of malignant cells, and we identified two HLA-A2- and HLA-A3-binding peptides derived from the RGS5 protein. Interestingly, RGS5 was recently shown to be involved in tumor angiogenesis. EXPERIMENTAL DESIGN: We used monocyte-derived dendritic cells pulsed with these novel antigenic peptides or transfected with RGS5-mRNA for the in vitro induction of CTLs, generated from healthy donors, to analyze the presentation of RGS5-deduced epitopes by malignant cells. RESULTS: The generated CTL lines elicited an antigen-specific and HLA-restricted cytolytic activity against tumor cells endogenously expressing the RGS5 protein. Furthermore, we were able to induce RGS5-specific CTLs using peripheral blood mononuclear cells from a patient with acute myeloid leukemia capable of recognizing the autologous leukemic blasts while sparing nonmalignant cells. CONCLUSIONS: These results indicate that the RGS5 peptides represent interesting candidates for the development of cancer vaccines designed to target malignant cells and tumor vessels.     

肿瘤相关抗原CTL表位DC疫苗优化策略研究进展

肿瘤免疫治疗被认为是具有显著优势的抗肿瘤疗法,研究人员选择人体内树突状细胞设计DC疫苗,通过DC呈递肿瘤相关抗原,进而诱导CTL细胞,对肿瘤进行杀伤.但抗原肽存在分子量小、免疫原性低等问题,难以在体内引发强有力的特异性免疫反应.本文就如何优化CTL表位DC疫苗作一综述,旨在为疫苗设计提供参考.     

苦瓜蛋白MAP30的HLA-A2/A3限制性CTL表位预测

目的:预测苦瓜蛋白MAP30的HLA - A2/A3限制性CTL表位.方法:应用lasergene 7.0和NetCTL-1.2 Server对MAP30进行HLA - A2 /A3限制性CTL表位预测.结果:MAP30的二级结构含有8个α-螺旋和9个β-折叠股;柔韧性良好氨基酸区域为19-40、99-146、166-273;亲水性指数较高区域为22-45、97-114、117-148、180-198、224-257、265-275;抗原性指数较高区域为19-28、63-71、98-114、118-123、224-246、248-260、262-274;有30个可能CTL表位,综合分析后获得2个HLA - A2和5个HLA - A3限制性CTL表位.结论:MAP30具有潜在的7个HLA-A2/A3限制性CTL表位.     

乙型脑炎病毒E蛋白HLA—A＊0201限制性细胞毒性T细胞表位的预测

目的:预测乙型脑炎病毒E蛋白(Japanese encephalitis virus envelope protein,JEV E 蛋白)的HLA-A2限制性CTL表位.方法:采用SYFPEITHI超基序法、量化基序多项式方案分析及延展基序方案联合应用,筛选JEV E 蛋白HLA-A2限制性的九肽细胞毒性T淋巴细胞(cytotoxic lymphocyte,CTL)表位.结果:通过预测获得了9个JEV E 蛋白HLA-A0201限制性的九肽CTL表位.结论:超基序法与量化基序多项式方案分析及延展基序方案的联合应用所产生的JEV E 蛋白CTL表位,为进一步研制新型乙脑肽疫苗奠定了重要的基础.