Generation, immunologic characterization and antitumor effects of human monoclonal antibodies for carcinoembryonic antigen

我们利用KM小鼠制备了针对癌胚抗原（CEA）的全人单克隆抗体（hmab）， KM小鼠携带人类14号染色体片段，其中包含小鼠基因组中的整个Ig H链位点和人类kappa L链片段。通过将P3-U1小鼠骨髓瘤细胞与经CEA免疫的KM小鼠脾细胞融合，获得了46个产生CEA抗体的杂交瘤克隆。其中22个克隆产生的hmab能与CEA发生反应，但不能与CEA相关细胞粘附分子（CEACAM）家族成员CEACAM1、CEACAM6和CEACAM8发生反应。12例hmab中，IgG4 8例，IgG3 2例，IgG2 1例，IgG1 1例。这些单克隆抗体对CEA的亲和力常数与先前制备的小鼠抗CEA单克隆抗体（MmAbs）相当。BlAcore分析显示，22种hmab中有1种和2种分别在CEA的N结构域和Al或b1结构域上与MmAbs定义的2个表位发生反应，在体外人补体存在下，2种hmab对表达CEA的肿瘤细胞表现出显著的细胞毒性，即50-65%。在人淋巴因子激活的体外杀伤细胞中，3种hmab对肿瘤细胞表现出40-65%的依赖于抗体的细胞介导的细胞毒性。此外，其中一种hmab对异种移植cea表达细胞的小鼠具有显著的肿瘤生长抑制作用。考虑到它们对人类缺乏免疫原性，这些cea特异性hmab可能对免疫治疗方法和免疫诊断有用。

We generated fully human mAbs (HmAbs) to carcinoembryonic antigen (CEA) using the KM mouse, which carries a human chromosome 14 fragment containing the entire Ig H chain loci and human kappa L chain segments in the mouse genome. Forty-six hybridoma clones producing HmAbs to CEA were thus obtained by fusing the P3-U1 mouse mycloma cells with splenocytes of the KM mice immunized with CEA. Among them, 22 clones produced HmAbs that reacted with CEA but not with 3 other CEA-related cell adhesion molecule (CEACAM) family members, CEACAM1, CEACAM6 and CEACAM8. In 12 HmAbs examined, 8 were IgG4, 2 were IgG3, 1 was IgG2, and the other was IgG1. The affinity constants for CEA of these HmAbs were comparable to those of the previously prepared mouse anti-CEA mAbs (MmAbs). BlAcore analyses revealed that 1 and 2 of the 22 HmAbs react with 2 epitopes defined by MmAbs on the domain N and the domain Al or B 1 of CEA, respectivelyIn the presence of human complement in vitro, 2 HmAbs tested showed substantial cytotoxicity, namely, 50-65%, against CEA-expressing tumor cells. With human lymphokine-activated killer cells in vitro, 3 HmAbs tested exhibited 40-65% Ab-dependent cell-mediated cytotoxicity against the tumor cells. Moreover, one of the HmAbs induced a significant inhibition of tumor growth when administered to mice xenografted with the CEA-expressing cells.Considering their, lack of immunogenicity to humans, these CEA-specific HmAbs may be useful for immunotherapeutic approaches as well as for immunodiagnosis.