目的：设计同时靶向B淋巴细胞表面CD20 和CD19 两个抗原蛋白的双特异嵌合抗原受体（chimeric antigen receptor,CAR）并制备BiCAR-T 细胞，检测其对B淋巴细胞肿瘤细胞的杀伤作用以及对免疫缺陷B-NSG 小鼠白血病模型的治疗效果。方法：构建基于鼠源CD19 和人源化CD20 scFv 的双靶点CAR分子，将CAR基因装载于慢病毒载体中，在293T细胞中包装慢病毒，感染健康人T 细胞制备BiCAR-T 细胞。构建表达CD19 和CD20 的K562-CD19-GFP、K562-CD20-GFP 以及表达Luciferase 的Nalm6-Luc-GFP 细胞作为靶细胞，将BiCAR-T 细胞与靶细胞共同孵育，检测其对靶细胞杀伤能力及释放IFN-γ 水平。使用Nalm6-Luc-GFP 细胞构建白血病小鼠模型，尾静脉注射BiCAR-T细胞，通过小动物成像方法观察BiCAR-T细胞对荷瘤小鼠的治疗作用。结果：健康人来源的BiCAR-T 细胞经7 d 培养后扩增良好，扩增倍数为20~50 倍，阳性率为10%~92%，显示成功制备BiCAR-T细胞。在效靶比为10∶1 时，BiCAR-T细胞对Nalm-6、K562-CD19-GFP 和K562-CD20-GFP 的杀伤率显著高于对照组细胞[ （76.7±7.4）% vs（8.7±2.4）%、（93.3±5.2）% vs（46.7±6.2）、（51.0±0.8）vs（30.7±0.5）%，均P<0.01]；与对照组相比，与Nalm-6细胞共孵育后BiCAR-T 细胞分泌IFN- γ 量显著增加[（872.7±7.7）vs（101.0±5.3）pg/ml ，P<0.01]。动物实验表明，BiCAR-T细胞对B-NSG小鼠白血病模型治疗效果明显，注射BiCAR-T细胞后白血病细胞逐渐减少，第50 天时基本消失，小鼠全部存活至第70 天被安乐死；PBS和对照T细胞组小鼠分别在（19±3）和（20±1）d 全部死亡。结论：成功设计了表达CD19 和CD20 的双靶点CAR分子后成功制备了BiCAR-T 细胞，该细胞能够有效杀伤表达CD19 和/或CD20 的B淋巴细胞肿瘤细胞，与靶细胞共同孵育后能够分泌大量IFN-γ，对B-NSG免疫缺陷小鼠白血病模型具有明显的治疗效果。

Objective: To design and prepare a novel bi-specific chimeric antigen receptor (CAR) -T cell targeting both CD20 and CD19 antigen on B lymphocyte surface, and to detect its killing effect on B lymphocyte tumors as well as its treatment efficacy on immunodeficiency B-NSG mouse with leukemia. Methods: Bi-specific CAR molecule of CD20 (human originated)/CD19 (murine originated) scFv was constructed and packaged into lentiviral vector in 293 cells, and then transfected into T lymphocytes from healthy donors to prepare BiCAR-T cells. K562-CD19-GFP cells (with positive CD19 expression), K562-CD20-GFP cells (with positive CD20 expression) and Nalm6-Luc-GFP cells expressing luciferase were constructed as target cells. After being co-incubated with above mentioned targets cells, the cytotoxic effects of BiCAR-T cells on target cells were evaluated via LDH release assay, and the secretion of IFN-γ by BiCAR-T cells was evaluated by ELISA. Nalm6-Luc-GFP cells were used to construct the mouse model of leukemia and BiCAR-T cells were transfused via tail veins; the treatment efficacy of BiCAR-T cells on tumor bearing mice was evaluated with small animal imaging method. Results: After 7 days’incubation, the BiCAR-T cells originated from healthy donors amplified about 20-50 times with a positive rate of 10%~92%, indicating successful preparation of BiCAR-T cells. Under an effector∶target ratio of 10∶1, the killing rates of BiCAR-T cells against Nalm-6, K562-CD19-GFP and K562-CD20-GFP cells were significantly higher than that of control cells [(76.7±7.4)% vs (8.7±2.4)%, (93.3±5.2)% vs (46.7±6.2)%, (51.0±0.8) vs (30.7±0.5)%, all P<0.01]. Compared with control group, BiCAR-T cells co-incubated with Nalm-6 cells also secreted significantly more IFN- γ [(872.7±7.7) vs (101.0±5.3)pg/ml, P<0.01). Animal experiment showed that BiCAR-T cells had significant efficacy on B-NSG mice with leukemia; NSG leukemia mice treated with BiCAR-T cells all lived up to 70 days (till they were mercy killed) and leukemia cells disappeared at about 50 days,while the mice in PBS and T lymphocytes group all died at (19±3) d and (20±1) d, respectively. Conclusion: Bi-specific CAR molecules expressing CD19 and CD20 were successfully designed and BiCAR-T cells were successfully prepared. The BiCAR-T cells can effectively kill CD19 and/or CD20 tumor cells and secret large amounts of IFN-γ after co-incubation with target cells, exerting significant treatment efficacy on B-NSG immunodeficiency mouse with leukemia.

首都临床特色应用研究与成果推广课题资助项目（No.Z171100001017189）；北京市朝阳区科技计划资助项目（No.CYSF1835）