Rational Design of Therapeutic Vaccines for CEA+ Tumors

描述(由申请人提供)：广泛的临床前研究以及临床试验的结果表明，用模仿人类癌胚抗原(CEA)表位的抗独特型(ID)抗体(3H1)接种疫苗有可能增加生存益处。在结直肠癌患者和CEA转基因小鼠中，抗LD3H1打破了对CEA的免疫耐受，诱导了抗CEA抗体和CD4+T辅助细胞(Th1)反应。这一目前形式的反残疾办法虽然前景看好，但需要改进才能充分发挥其潜力。合适的小鼠肿瘤模型将被用来探索显著提高该疫苗治疗效果的策略。该建议基于这样的假设，即在宿主中刺激CEA特异性的CD4+T细胞反应，即T-Help，将为CEA特异性CTL的启动和激活提供关键帮助，CEA特异性CTL是肿瘤破坏的主要效应细胞(CD8+T细胞)。我们推测，CD4+和CD8+T细胞表位的结合将进一步增强抗肿瘤免疫反应。本研究的具体目的是：1)以树突状细胞(DC)为APC，用3H1免疫C57BL/6小鼠(H_2kb)，人CEA和HLA-A2双转基因肿瘤模型，以树突状细胞(DC)为APC，联合CEA产生的3H1和CEA的mRNA，是否能诱导CTL和产生治疗性免疫；2)以DC为APC，探讨3H1与已知的人类CEA的激动型CTL表位结合在上述肿瘤模型中是否具有更好的作用；3)根据3H1和CEA的氨基酸序列同源性，验证其与CEA激动型CTL多肽结合后，是否具有更强的免疫原性。选择最佳疫苗接种方案的标准将基于在体外和体内激发抗肿瘤活性的能力。我们将检测抗体效价、体外CTL活性、细胞内细胞因子水平和体内肿瘤消退。在目标4中，我们将进一步探索通过联合应用IL-2、IL-12、CpG ODN或抗CTLA4抗体来增强体内肿瘤特异性CD4+和CD8+T细胞应答的方法。我们将通过组织病理学分析来测试表达CEA的小鼠正常器官中任何可能的自身免疫反应(目标5)。这些研究表明的有希望的策略将在AIM 6中最终在表达CEA和HLA-A2的小鼠APC基因敲除小鼠中进行评估，可以说，这是最好的结肠癌小鼠模型，因为它与人类疾病非常相似。这些研究的结果将有助于设计治疗CEA+肿瘤的改进的治疗性疫苗，并可以很容易地纳入我们正在进行的临床计划中。

DESCRIPTION (provided by applicant): Extensive preclinical studies, as well as results obtained from clinical trials, suggest that vaccination with an anti-idiotype (Id) antibody (3H1) that mimics an epitope of human carcinoembryonic antigen (CEA) has the potential to augment survival benefits. Anti-ld 3H1 breaks immune tolerance to CEA and induces anti-CEA antibody as well as CD4+T helper (Th1) responses in colorectal cancer patients and also in mice transgenic for CEA. This anti-ld approach in its current form, although promising, will need improvements to realize its full potential. Suitable murine tumor models will be used to explore strategies that will significantly improve the therapeutic impact of this vaccine. The proposal is based on the hypothesis that stimulating a CEA-specific CD4+ T cell response, ie T-help, in the host, will provide critical help for priming and activation of CEA-specific CTL, the major effector cells (CD8+ T cells) for tumor destruction. We hypothesize that the combination of CD4+ with CD8+ T cell epitopes will further augment the anti-tumor immune responses. The specific aims of this proposal are: 1) to determine whether vaccination with 3H1, which will generate anti-CEA Ab and T-help, in combination with mRNA derived from CEA, using dendritic cells (DC) as APC, will induce CTL and engender therapeutic immunity in an established tumor model in C57BL/6 mice (H2kb), double transgenic for human CEA and HLA-A2; 2) to explore whether a combination of 3H1 with HLA-A2 restricted known agonist CTL epitopes of CEA, using DC as APC, will work better in the above tumor model; 3) to test whether the idio-peptides, (LCD-2 and CEA-B) derived from the structure of 3H1 and CEA based on the amino acid sequence homology, which also induce CD4+Th1 help will be more immunogenic in combination with the agonist CTL peptides of CEA. The criteria for selection of the optimal regimen for vaccination will be based on the ability to invoke anti-tumor activities in vitro and in vivo. We will measure the antibody titer, in vitro CTL activity, intra-cellular cytokine levels and in vivo tumor regression. In Aim 4, we will further explore methods to boost tumor-specific CD4+ as well as CD8+ T cell responses in vivo by coadministration of agents such as IL-2, IL-12, CpG ODN or anti-CTLA4 antibody. We will test for any possible autoimmune responses in CEA-expressing normal organs of mice by histopathological analysis (Aim 5). Promising strategies indicated by these studies will be finally evaluated in Aim 6 in the murine Apc knock-out transgenic mice expressing CEA and HLA-A2, which arguably, are the best murine model for colon cancer, as it closely resembles the human disease. The results obtained from these studies will help design improved therapeutic vaccines for the treatment of CEA+ tumors and can be incorporated readily into our ongoing clinical programs.