新融合蛋白CD19scFv/CD80抗白血病作用研究

Study on the anti-leukemia effect of a novel recombinant protein CD19scFv/CD80

B系急性淋巴细胞白血病(B-ALL)是一种十分常见的血液系统恶性肿瘤,尽管目前化疗效果显著,但仍有部分儿童和成人B-ALL患者疗效较差、预后不佳.研究表明,ALL细胞表面免疫共刺激分子CD80(B7.1)表达降低或不表达,导致白血病细胞不能有效地被细胞毒T细胞(CTL)识别杀伤.然而,几乎所有的B-ALL细胞均表达CD19表面抗原.因此,本研究利用前期构建的CD19单链抗体(scFv)/CD80融合基因及表达的融合蛋白,通过融合蛋白中抗CD19scFv,将CD80结合到B-ALL白血病细胞表面,靶向激活CTL细胞,起到杀伤白血病细胞的作用.在体外共培养实验中,该融合蛋白结合B-ALL细胞系Nalm-6细胞后,可诱导淋巴细胞增殖,分泌细胞因子并产生较显著的特异性细胞毒作用.以Nalm-6细胞在免疫缺陷小鼠(Mus musculus)中建立白血病动物模型,CD19scFv/CD80融合蛋白联合输注淋巴细胞可显著延长小鼠的生存时间.本研究表明,该融合蛋白可使逃避免疫监视的B-ALL细胞有效地转化成抗原提呈细胞,进而激活特异性免疫反应,具有潜在的临床应用价值.

B-cell acute lymphoblastic leukemia（B-ALL） is a very common hematological malignancy. Despite the curative effect of chemotherapy observed in children and adults with B-ALL, still some patients fail to respond to chemotherapy and suffer from poor prognosis. Studies have shown that the costimulatory molecule CD80（B7.1） is expressed at low levels on ALL cells, which avoids leukemia cells being recognized and killed by cytotoxic T cells（CTLs）. However, almost all B-ALL cells express CD 19 antigen. Therefore, in this study, the previously constructed recombinant CD19 scFv/CD80 protein, consisting of the extracellular domain of human CD80（B7.1） and a single-chain variable fragment antibody to human CD 19 antigen（CD19 scFv）, was used as a bridge to decorate B-ALL cells with the costimulatory molecule CD80 through the binding of CD19 scFv to CD 19 antigen. Using this strategy, CTLs could be activated by B-ALL cells pretreated with CD19 scFv/CD80 fusion protein, and thus, they could exert their killing effect on leukemia cells. In the in vitro study, it was observed B-ALL Nalm-6 cells cocultured with the recombinant CD19 scFv/CD80 fusion protein were capable of inducing donor T-cell-specific expansion, cytokine production, and cytolytic activity. In a leukemic xenograft NOD/SCID mouse model, intravenous injection of CD19 scFv/CD80 fusion protein was able to significantly prolong the survival time of mice with leukemia. In conclusion, the novel CD19 scFv/CD80 fusion protein could effectively modify B-ALL cells, which evade the immune surveillance,into antigen-presenting cells,which could thus activate specific immune responses, thereby implying a potential clinical value.