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呈强表达。最近，鉴定了几种源自CEA的表位肽。已经阐明HLA-A24限制性肽CEA 652 [9]（TYACFVSNL）能够引发特异性CTL，其能够裂解表达HLA-A24和CEA的肿瘤细胞。HLA-A24是日本人最适用的MHC I类等位基因。在这项初步研究中，我们使用肽脉冲树突状细胞（DC）从外周血单核细胞补充GM-CSF和IL-4。8例晚期表达CEA的胃肠道恶性肿瘤患者每2或3周接受一次皮下接种。通过酶联免疫斑点（ELISPOT）试验评估疫苗接种后CTL反应性的变化及其体外诱导抗肿瘤CTL的能力。6例患者中有3例在接种疫苗后产生了CTL反应。6例患者中有2例在ELISPOT测定中应答。在8例患者中的1例注射部位观察到DTH反应。注射部位的皮肤活检显示淋巴细胞浸润。然而，未观察到重大肿瘤消退。除1例接种3次后出现轻度腹泻外，未观察到明显毒副作用。结论：肽致敏DC皮下注射是安全的，并能在肿瘤组织中产生肽特异性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.