Rational Design of Therapeutic Vaccines for CEA+ Tumors

描述（由申请方提供）：广泛的临床前研究以及从临床试验中获得的结果表明，使用模拟人癌胚抗原（CEA）表位的抗独特型（Id）抗体（3 H1）接种疫苗有可能增加生存获益。抗ld 3 H1打破了对CEA的免疫耐受，并在结直肠癌患者和CEA转基因小鼠中诱导抗CEA抗体以及CD 4 +T辅助细胞（Th 1）应答。这种目前形式的抗ld方法虽然有希望，但需要改进才能充分发挥其潜力。合适的小鼠肿瘤模型将用于探索将显著改善该疫苗的治疗效果的策略。该提议基于这样的假设，即刺激宿主中CEA特异性CD 4 + T细胞应答，即T辅助，将为CEA特异性CTL的引发和活化提供关键帮助，所述CTL是用于肿瘤破坏的主要效应细胞（CD 8 + T细胞）。我们假设CD 4+与CD 8 + T细胞表位的组合将进一步增强抗肿瘤免疫应答。本发明的具体目的是：1）确定在人CEA和HLA-A2双转基因的C57 BL/6小鼠（H2kb）中，使用树突状细胞（DC）作为APC，用将产生抗CEA Ab和T-help的3 H1与源自CEA的mRNA组合接种，是否将在建立的肿瘤模型中诱导CTL并产生治疗性免疫; 2）探索3 H1与CEA的HLA-A2限制性已知激动剂CTL表位的组合，使用DC作为APC，是否在上述肿瘤模型中更好地起作用; 3）测试独特肽，（LCD-2和CEA-B）基于3 H1和CEA的结构的氨基酸序列同源性，其也诱导CD 4 + Th 1辅助细胞与CEA的激动剂CTL肽组合将更具免疫原性。疫苗接种的最佳方案的选择标准将基于在体外和体内引发抗肿瘤活性的能力。我们将测量抗体滴度、体外CTL活性、细胞内细胞因子水平和体内肿瘤消退。在目的4中，我们将进一步探索通过共同施用诸如IL-2、IL-12、CpG ODN或抗CTLA 4抗体的试剂来增强体内肿瘤特异性CD 4+以及CD 8 + T细胞应答的方法。我们将通过组织病理学分析测试CEA表达小鼠正常器官中任何可能的自身免疫应答（目的5）。这些研究表明的有希望的策略将最终在Aim 6中在表达CEA和HLA-A2的鼠Apc敲除转基因小鼠中进行评估，这可以说是结肠癌的最佳鼠模型，因为它与人类疾病非常相似。从这些研究中获得的结果将有助于设计用于治疗CEA+肿瘤的改进的治疗性疫苗，并且可以很容易地纳入我们正在进行的临床项目中。

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.