Gidlöf C, Dohlsten M, Lando P, Kalland T, Sundström C, Tötterman T H
Department of Clinical Immunology, University Hospital, Uppsala, Sweden.
Blood. 1997 Mar 15;89(6):2089-97.
The bacterial superantigen staphylococcal enterotoxin A (SEA) is an efficient activator of cytotoxic T cells when presented on major histocompatibility complex (MHC) class II molecules of target cells. Our previous studies showed that such SEA-directed T cells efficiently lysed chronic B-lymphocytic leukemia (B-CLL) cells. Next, we made a mutated SEA-protein A (SEAm-PA) fusion protein with more than 1,000-fold reduced binding affinity for MHC class II compared with native SEA. The fusion protein was successfully used to direct T cells to B-CLL cells coated with different B lineage-directed monoclonal antibodies (MoAbs). In this communication, we constructed a recombinant anti-CD19-Fab-SEAm fusion protein. The MHC class II binding capacity of the SEA part was drastically reduced by a D227A point mutation, whereas the T-cell activation properties were retained. The Fab part of the fusion protein displayed a binding affinity for CD19+ cells in the nanomolar range. The anti-CD19-Fab-SEAm molecule mediated effective, specific, rapid, and perforin-like T-cell lysis of B-CLL cells at low effector to target cell ratios. Normal CD19+ B cells were sensitive to lysis, whereas CD34+ progenitor cells and monocytes/macrophages were resistant. A panel of CD19+ B-cell lines representing different B-cell developmental stages were efficiently lysed, and the sensitivity correlated with surface ICAM-1 expression. The anti-CD19-Fab-SEAm fusion protein mediated highly effective killing of tumor biopsy cells representing several types of B-cell non-Hodgkin's lymphoma (B-NHL). Humanized severe combined immune deficiency (SCID) mice carrying Daudi lymphoma cells were used as an in vivo therapy model for evaluation of the anti-CD19-Fab-SEAm fusion protein. Greater than 90% reduction in tumor weight was recorded in anti-CD19-Fab-SEAm-treated animals compared with control animals receiving an irrelevant Fab-SEAm fusion protein. The present results indicate that MoAb-targeted superantigens (SAgs) may represent a promising approach for T-cell-based therapy of CD19+ B-cell malignancies.
细菌超抗原葡萄球菌肠毒素A（SEA）在靶细胞的主要组织相容性复合体（MHC）II类分子上呈递时，是细胞毒性T细胞的有效激活剂。我们之前的研究表明，这种SEA导向的T细胞能有效裂解慢性B淋巴细胞白血病（B-CLL）细胞。接下来，我们制备了一种突变的SEA-蛋白A（SEAm-PA）融合蛋白，与天然SEA相比，其与MHC II类的结合亲和力降低了1000多倍。该融合蛋白成功用于将T细胞导向用不同B谱系导向单克隆抗体（MoAb）包被的B-CLL细胞。在本通讯中，我们构建了一种重组抗CD19-Fab-SEAm融合蛋白。SEA部分的MHC II类结合能力通过D227A点突变大幅降低，而T细胞激活特性得以保留。融合蛋白的Fab部分对CD19+细胞的结合亲和力在纳摩尔范围内。抗CD19-Fab-SEAm分子在低效应细胞与靶细胞比例下介导了对B-CLL细胞的有效、特异性、快速且类似穿孔素的T细胞裂解。正常CD19+ B细胞对裂解敏感，而CD34+祖细胞和单核细胞/巨噬细胞具有抗性。一组代表不同B细胞发育阶段的CD19+ B细胞系被有效裂解，且敏感性与表面ICAM-1表达相关。抗CD19-Fab-SEAm融合蛋白介导了对代表几种B细胞非霍奇金淋巴瘤（B-NHL）类型的肿瘤活检细胞的高效杀伤。携带Daudi淋巴瘤细胞的人源化严重联合免疫缺陷（SCID）小鼠被用作体内治疗模型，以评估抗CD19-Fab-SEAm融合蛋白。与接受无关Fab-SEAm融合蛋白的对照动物相比，抗CD19-Fab-SEAm治疗的动物肿瘤重量减少了90%以上。目前的结果表明，单克隆抗体靶向的超抗原（SAgs）可能是基于T细胞治疗CD19+ B细胞恶性肿瘤的一种有前景的方法。
