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Title: [Construction of a new anti-CD123 chimeric antigen receptor T cells and effect of anti-acute myeloid leukemia].
Author: Wang ZZ, Lu Y, Xu YX, Xing HY, Tang KJ, Tian Z, Rao Q, Wang M, Xiong DS, Wang JX.
Journal: Zhonghua Xue Ye Xue Za Zhi; 2020 Mar 14; 41(3):192-197. PubMed ID: 32311887.
Abstract:
Objective: To construct a new CD123- specific chimeric antigen receptor in order to provide a foundation for immunotherapy of CD123 positive leukemia. Methods: A hybridoma strain (6E11) capable of stably secreting CD123 antibody was obtained by a monoclonal screening technique, and the hybridoma cells were expanded and injected intraperitoneally to the pretreated Balb/c mice. Ascites was collected and purified to obtain the monoclonal antibody (mAb) . The affinity and specificity of 6E11 mAb were measured. The variable regions of the heavy and light chains of the 6E11 mAb were cloned by RT-PCR from the 6E11 mouse hybridoma. We generated a new CD123 specific chimeric antigen receptor with a scFv fragment derived from 6E11 antibody, designated as 6E11 CAR. T cells were transduced with lentiviral supernatant from 293T cells transfected with 6E11 CAR plasmid to generate 6E11 CAR-T cells. The specific cytotoxicity of 6E11 CAR-T against CD123(+) acute myeloid leukemia (AML) cell lines and primary AML cells in vitro were evaluated by co-culture experiments, degranulation experiments and cytokine releasing assay. Results: ① A hybridoma cell line 6E11 stably secreting anti-human CD123 antibody was developed and its variable region sequences were obtained. ② The 6E11 mAb has high affinity for CD123 protein (Kd value: 2.1 nmol/L) . The 6E11 mAb specifically recognizes CD123(+) cell line THP-1 cells and does not respond to CD123(-) cell line Jurkat cells. ③ 6E11 CAR-T cells were successfully generated with a CAR expression rate higher than 60%. ④ 6E11 CAR-T cells could specifically kill CD123(+) MV4-11 cell line but had no killing effect on the CD123(-) K562 cell line. Compared with vector-T cells, 6E11 CAR-T cells have higher killing rate to MV4-11 cells[ (98.60±1.20) %vs (20.28±6.74) %, P<0.001]. ⑤ MV4-11 cells activated 6E11 CAR-T cells significantly but not Vector-T cells[ (26.33±3.30) %vs (1.17±0.06) %, P<0.001]. ⑥ 6E11 CAR-T cells released more cytokines than vector-T cells when co-cultured with MV4-11[IL-2: (92.90±1.51) pg/ml vs (6.05±3.41) pg/ml, P<0.001; TNF-α: (1 407.20±91.95) pg/ml vs (7.86±0.85) pg/ml, P<0.001; IFN-γ: (5 614.60±170.17) pg/ml vs (8.42±2.70) pg/ml, P<0.001]. The IFN-γ, IL-2 and TNF-α in the 6E11 CAR-T group were similar to those in the Vector-T group when co-cultured with K562. ⑦ 6E11 CAR-T cells could be activated by bone marrow mononuclear cells (BMMNC) derived from CD123(+) AML patients and effectively kill these BMMNC cells from CD123(+) AML patients. Conclusion: 6E11 hybridoma cell line can stably secrete highly specific monoclonal antibodies against human CD123, which can be used to detect the expression of human CD123. It can also be used to target human CD123 protein in tumor immunotherapy. CD123 CAR-T cells with 6E11 Ig variable region sequence have specific anti-leukemic activity in vitro, which may provide a new option for further clinical research of AML. 目的： 构建一种新的靶向CD123的嵌合抗原受体T细胞（CAR-T细胞），为CD123阳性白血病的免疫治疗提供实验参考。 方法： 通过单克隆筛选技术获得能稳定分泌CD123抗体的杂交瘤细胞株6E11，将杂交瘤细胞扩增后腹腔注射至Balb/c小鼠腹腔内，收集腹水并处理、纯化得到单克隆抗体，测定抗体效价并对其特异性进行验证；RT-PCR法获得轻链和重链可变区序列，并以此为基础利用分子克隆技术构建一种新的靶向CD123嵌合抗原受体，包装病毒后感染T细胞制备CD123 CAR-T细胞，通过功能实验初步探讨6E11 CAR-T细胞体外抗白血病的能力。 结果： ①获得1株稳定分泌抗人CD123抗体的杂交瘤细胞株6E11并获得其可变区序列。②6E11单克隆抗体对CD123蛋白亲和性高，解离常数（K(d)值）为2.10 nmol/L，特异性识别CD123阳性细胞且与CD123阴性细胞无交叉反应。③成功构建了CD123 CAR慢病毒载体，感染T细胞后获得了靶向CD123的CAR-T细胞（6E11 CAR-T），感染效率大于60%。④6E11 CAR-T能明显杀伤CD123阳性靶细胞MV4-11，效靶比1∶1时6E11 CAR-T细胞对MV4-11细胞的杀伤比例明显高于Vecor-T细胞[（98.60±1.20）%对（20.28±6.74）%，P<0.001]，但对CD123阴性靶细胞K562没有明显杀伤作用。⑤MV4-11细胞可以显著激活6E11 CAR-T，但对Vecor-T细胞无明显激活作用[（26.33±3.30）%对（1.17±0.06）%，P<0.001]。⑥6E11 CAR-T与MV4-11细胞共培养上清中细胞因子水平均显著高于Vecor-T组[IL-2：（92.90±1.51）pg/ml对（6.05±3.41）pg/ml，P<0.001；TNF-α：（1 407.20±91.95）pg/ml对（7.86±0.85）pg/ml，P<0.001；IFN-γ：（5 614.60±170.17）pg/ml对（8.42±2.70）pg/ml，P<0.001]，但与K562细胞共培养后，两组各细胞因子水平差异无统计学意义。⑦6E11 CAR-T在与CD123阳性急性髓系白血病（AML）原代细胞共培养过程中被显著激活，且能有效杀伤原代AML细胞。 结论： 杂交瘤细胞株6E11能稳定分泌高效特异的抗人CD123单克隆抗体，可用于检测表达人CD123的细胞，也能应用在靶向人CD123蛋白的肿瘤免疫治疗中，以6E11 Ig可变区序列为抗原识别区的CD123 CAR-T细胞，具有明确的体外抗白血病活性，为进一步的临床研究奠定了基础。.

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