Epitope distance to the target cell membrane and antigen size determine the potency of T cell-mediated lysis by BiTE antibodies specific for a large melanoma surface antigen
Epitope distance to the target cell membrane and antigen size determine the potency of T cell-mediated lysis by BiTE antibodies specific for a large melanoma surface antigen
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DOI：
10.1007/s00262-010-0844-y
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发表时间：
2010-08-01
影响因子：
5.8
通讯作者：
Kufer, Peter
中科院分区：
文献类型：
--
作者：
Bluemel, Claudia;Hausmann, Susanne;Kufer, Peter
黑色素瘤硫酸软骨素蛋白聚糖（MCSP;也称为CSPG 4、NG 2、HMW-MAA、MSK 16、MCSPG、MEL-CSPG或gp 240）是在人黑色素瘤细胞上频繁表达的表面抗原，其参与细胞粘附、侵袭和扩散、血管生成、补体抑制和信号传导。因此，MCSP经常被选为开发基于抗体和疫苗的治疗方法的靶抗原。我们在此使用了一大组抗人MCSP的单克隆抗体来产生BiTE（用于双特异性T细胞增殖剂）类的单链MCSP/CD 3双特异性抗体。尽管与MCSP的结合亲和力相似，但各BiTE抗体在用全长人MCSP或用各种MCSP缺失突变体和融合蛋白稳定转染的CHO细胞的重定向裂解的效力方面存在很大差异。与MCSP的膜近端结构域D3结合的BiTE抗体比与更远端结构域结合的BiTE抗体更有效。通过测试作为表面抗原的MCSP和EpCAM之间的各种融合蛋白，用EpCAM/CD 3-双特异性BiTE抗体MT 110证实了这种表位距离效应。表达小表面靶抗原的CHO细胞通常比表达较大靶抗原的CHO细胞更好地裂解，表明抗原大小也是BiTE抗体效价的重要决定因素。本研究首次将结合结构域的定位和表面抗原的大小与BiTE重定向的细胞毒性T细胞裂解靶细胞的效力相关联。在MCSP抗原的情况下，这为选择最大效力的BiTE抗体候选物以开发新的黑素瘤疗法提供了基础。
Melanoma chondroitin sulfate proteoglycan (MCSP; also called CSPG4, NG2, HMW-MAA, MSK16, MCSPG, MEL-CSPG, or gp240) is a surface antigen frequently expressed on human melanoma cells, which is involved in cell adhesion, invasion and spreading, angiogenesis, complement inhibition, and signaling. MCSP has therefore been frequently selected as target antigen for development of antibody- and vaccine-based therapeutic approaches. We have here used a large panel of monoclonal antibodies against human MCSP for generation of single-chain MCSP/CD3-bispecific antibodies of the BiTE (for bispecific T cell engager) class. Despite similar binding affinity to MCSP, respective BiTE antibodies greatly differed in their potency of redirected lysis of CHO cells stably transfected with full-length human MCSP, or with various MCSP deletion mutants and fusion proteins. BiTE antibodies binding to the membrane proximal domain D3 of MCSP were more potent than those binding to more distal domains. This epitope distance effect was corroborated with EpCAM/CD3-bispecific BiTE antibody MT110 by testing various fusion proteins between MCSP and EpCAM as surface antigens. CHO cells expressing small surface target antigens were generally better lysed than those expressing larger target antigens, indicating that antigen size was also an important determinant for the potency of BiTE antibody. The present study for the first time relates the positioning of binding domains and size of surface antigens to the potency of target cell lysis by BiTE-redirected cytotoxic T cells. In case of the MCSP antigen, this provides the basis for selection of a maximally potent BiTE antibody candidate for development of a novel melanoma therapy.