Development of cancer vaccine therapy targeting CEA and the analysis of its immunologicai responses

癌胚抗原(CEA)在绝大多数胃肠道恶性肿瘤中强烈表达。最近发现了几种来源于CEA的表位多肽。已有研究表明，HLAA24限制性多肽CEA652[9](TYACFVSNL)能诱导特异性CTL杀伤表达HLAA24和CEA的肿瘤细胞。HLA-A24是日语中应用最广泛的MHC I类等位基因。在这项初步研究中，我们使用了外周血单核细胞产生的多肽冲击的树突状细胞(DC)，并补充了GM-CSF和IL-4。8例表现为胃肠道恶性肿瘤的晚期CEA患者，每2~3周皮下接种一次。用酶联免疫斑点法(ELISPOT)检测疫苗接种后CTL活性的变化及体外诱导抗肿瘤CTL的能力。6名患者中有3名在接种疫苗后出现CTL反应。6名患者中有2名在ELISPOT试验中有反应。8例患者中有1例在注射部位观察到DTH反应。注射部位皮肤活检可见淋巴细胞渗出。然而，没有观察到重大的肿瘤消退。除1例接种3次后出现轻度腹泻外，未见明显毒副作用。综上所述，我们的结果表明，多肽冲击的DC皮下注射是安全的，并且可以在肿瘤患者体内产生多肽特异性的CTL活性。

Carcinoembryonic antigen (CEA) is strongly expressed in vast majority of gastrointestinal malignancies. Recently several epitope peptides derived from CEA were identified. It was already clarified HLA-A24 restricted peptide CEA652[9] (TYACFVSNL) was capable of eliciting specific CTL which could lyse tumor cells expressing HLA-A24 and CEA. HLA-A24 is the most applicable MHC class I allele in Japanese. In this pilot study, we used peptide pulsed dendritic cells (DCs) generated from peripheral blood mononuclear cells supplemented with GM-CSF and IL-4. Eight patients with advanced CEA expressing gastrointestinal malignancies received every 2 or 3 weeks subcutaneous vaccination. Changes in CTL reactivity after vaccinations were assessed by enzyme-linked immunospot (ELISPOT) assay and their capacity to elicit anti-tumor CTL in vitro. Three of six patients developed their CTL reactivity after vaccinations. Two of six patients responded in ELISPOT assay. DTH reaction was observed in one of eight patients at the injected site. Skin biopsy at the injected site demonstrated infiltration of lymphocytes. However no major tumor regressions were observed. No significant toxic adverse effects were observed except mild diarrhea in one case after three times vaccination. In conclusion, our results demonstrated that peptide pulsed DCs injected subcutaneously was safe and could develop peptide specific CTL activity in cancer pattante.