抗人CD3人/鼠嵌合抗体基因的构建

为了降低鼠源抗人CD3单抗的免疫原性．增加其在人体内的生物活性及治疗作用，使该抗体能更广泛更有效地长期多次用于人体治疗肿瘤、器官移植排斥反应及自身免疫性疾病。本文采用PCR技术从分泌抗CD3单抗的杂交瘤细胞HIT3a的mRNA中分离克隆了抗体的轻重链可变区基因的cDNA。以此轻重链可变区cDNA为特异探针从HIT3a基因文库中分离带有调控序列的功能性轻重链可变区基因，并将其插入到含有人k轻链及人71重链恒定区基因的哺乳动物表达载体中成功地构建了抗人CD3人／鼠轻重链嵌合抗体基因，为研制人抗CD3入／鼠嵌合抗体完成了关键性的第一步。     

抗CD3人／鼠嵌合抗体的研究

已有的研究表明抗人T细胞CD3抗原的单抗具有激活和抑制人T细胞的双向功能。该单抗在抗肿瘤、抗多种器官移植排斥反应及再生障碍贫血的治疗中已显示出广阔的应用前景。但目前所用的CD3单抗都是鼠源的，大大地限制了它在临床治疗中的应用。为解决这一难题，本研究应用基因工程技术将鼠源CD3单机进行“人化”改造，在国内首次成功地构建并在其核细胞表达了抗CD3人／鼠嵌合抗体。这里综合报道研究结果如下：一、CD3单抗可变区基因cDNA的克隆和鉴定从分泌抗CD3单抗的小鼠杂交瘤HIT3a提取分离RNA，用小鼠Ig轻重涟恒定区保守序列为引物，…     

抗人胃癌3H11人-鼠嵌合抗体的构建及表达

为了降低抗人胃癌鼠单抗3H11的免疫原性,以利于该单抗在临床中的应用。我们构建并表达了3H11的人-鼠嵌合抗体,将3H11的轻、重链可变区基因分别插入到含有人k链及IgGl重链恒定区基因的真核细胞表达载体中,构建了3H11人-鼠嵌合抗体轻、重链表达载体。应用Lipofectin方法先将嵌合轻链表达载体转染到Sp2/0细胞中,经用含霉酚酸的选择培养基筛选及克隆化培养,获得稳定分泌3H11人-鼠嵌合轻链的转染细胞株。再将嵌合重链表达载体转染该细胞系,用含有组氨醇的选择培养基筛选,获得组氨醇抗性细胞株,经亚克隆后得到可稳定分泌人k链和人IgGl的转染细胞系,经ELISA检测该细胞系所分泌的上清含有可与人胃癌细胞系803结合的人IgG抗体活性,RT-PCR结果显示该细胞株有人-鼠嵌合抗体mRNA的转录,证明已获得分泌3H11人-鼠嵌合抗体的细胞系。     

基因工程抗体的研究

本文综述了本实验室近年来在基因工程抗体方面所做的工作：①从杂交瘤细胞基因组中筛选和鉴定出抗乙型脑炎病毒单克隆抗体的重链、轻链可变区基因，构建成人-鼠嵌舍基因并在骨髓瘤细胞中表达出抗乙型脑炎病毒的人-鼠嵌合抗体；②根据文献中抗CD3单抗的序列，进行了分子设计，设计出改形抗体的分子序列．用合成和PCR补齐的方法构建了改形的单域抗体（Vn)表达载体，并在大肠杆菌中表达；④构建了外分泌型-附着型的表达单链抗体的表达载体；④克隆和测序了抗人肺腺癌．膀胱癌、CD3的单抗重,轻链可变区基因，并正在构建鼠的抗体库。     

抗CEA抗体可变区基因的克隆及其嵌合抗体的表达

目的 在真核细胞中表达抗癌胚抗原（carcinoembryonic antigen,CEA)人－鼠嵌合抗体。方法 从分泌抗CEA鼠单抗C50的杂交瘤细胞扩增、克隆可变区基因。测序鉴定后连入真核表达载体,导入二氢叶酸还原酶缺陷型中国仓鼠卵巢（dihydrofolate reductase-deficient Chinese hamster ovary CHO-dhfr）细胞进行表达。采用间接和竞争抑制ELISA检测表达产物的人源性和抗原结合特异性。结果 序列测定初步确定所克隆的是功能性抗体可变区基因。在转染细胞上清中测到抗CEA嵌合抗体的表达。ELISA试验证实嵌合抗体具有人的恒定区,并与原鼠单抗C50有相同的抗原结合特异性。结论 成功地在真核细胞中表达了抗CEA人－鼠嵌合抗体。     

分泌抗CD71人-鼠嵌合抗体的转染瘤细胞分泌抗体的特异性与稳定性的研究

 目的　研究在液氮中冻存 2年的分泌抗CD71人 鼠嵌合抗体的转染瘤细胞分泌抗体的特异性、稳定性及抗体产量。方法　利用人IgG和鼠IgG作为浓度标准 ,绘制浓度曲线 ,比较研究转染瘤细胞培养上清的抗体分泌量。腹腔接种转染瘤细胞诱导裸鼠产生腹水抗体 ,经离子交换法纯化 ,电泳鉴定纯化嵌合抗体。结果　 1× 10 ⁵个 5ml转染瘤细胞培养 5天的上清中 ,嵌合抗体分泌量为 (0 .5～ 5 ) μg ml。Balb c裸鼠腹腔接种转染瘤细胞后 ,每只裸鼠腹水量在 (3～ 5 )ml,腹水抗体经纯化 ,抗体产量约为 (1～ 2 )mg (ml腹水 )。经离子交换法纯化 ,电泳鉴定 ,在分子量 5 5kDa和 2 5kDa处 ,可见有抗体IgG蛋白质的重链和轻链的染色条带。结论　由我们制备的在液氮中冻存 2年的分泌抗CD71人 鼠嵌合抗体 (D2C)的转染瘤细胞体外生长良好 ,抗体分泌稳定 ,产量高 ,特异性强。     

抗膀胱癌单抗Fab段基因的克隆及表达

目的：克隆抗膀胱癌单抗BDI的Fab段基因并在大肠杆菌中表达。方法：用逆转录－聚合酶链反应技术（RT－PCR），从分泌抗人膀胱癌的鼠单抗杂交瘤细胞系中克隆k链和Fd段基因，克隆到Fab表达载体中，在大肠杆菌表达噬菌体抗体和可溶Fab；运用PCR介导的定位点突变改造VH氨基端序列；用ELISA、免疫组化法等进行特异性鉴定。结果：从分泌抗膀胱癌的鼠单抗杂交瘤细胞系中克隆了重链Fd段和k链基因，在大肠杆菌中获得有抗原结合活性的噬菌体抗体和可溶性Fab的表达，但活性很弱，将VH氨基端序列矫正为亲本单抗原始序列后，明显改善了其活性，通过ELISA、免疫组化及模拟抗体库筛选证实了所获抗体片段的特异性结合及在抗体库技术中的可用性。结论：获得了功能性抗膀胱癌小分子抗体，并再次提示抗体氨基端序列对抗体活性的影响的重要性。     

抗CD71人-鼠嵌合抗体的体外抗肿瘤效应及在肿瘤异种移植模型中的定位研究

Objective To investigate the anti-tumor effects in vitro and in vivo distribution of the human/murine chimeric antibody (D2C).Methods The CD71 positive target cells(K562,CEM and SMMC7721) and the effector cells ,freshly isolated human PBMC,with the ratio of target cells to effector cells 1:50,were incubated in various dilutions of D2C antibody(Ab).Antibody dependent cytotoxicity(AD-CC) was tested by using an LDH-release assay.Instead of effector cells,complement was added to the target cells (CEM,SMMC-7721) with various dilutions of D2C Ab.A method of counting death cells was used in complement dependent cytotoxicity(CDC) assay.Tumor localization and distribution of the chimeric antibody(D2C) were observed by labeling the chimeric Ab with radioiodine(^131I) and injecting in into nude mice(Balb/c nu/nu) transplanted with human hepatocellular carcinoma cells (SMMC-7721).Results A significant ADCC was observed with the increased concentration of the D2C Ab.Cytolysis of CD71-positive target cells by the D2C Ab was found in the presence of fresh rabbit complement.Labeled D2C administered by intraperitoneal as well as tumor regional in-jection,was visualized by SPECT. The distribution of D2C Ab in murine organs and tissues showed that non-specific binding was lower fol-lowing tumor regional administration than when the antibody was administered by an intraperitoneal injection.The human/murine chimeric antibody(D2C) has in vitro anti-tumor effects and can exert its effects in specific tumor localization.Its distribution and local effects in vi-vo can be detected by radioimmunoimaging. Conclusion CD71 human/murine chimeric antibody showed marked killing of tumor cells in vitro,and specific recognition and high affinity binding to tumor tissue in vivo.     

抗人肺癌单克隆抗体3D3 scFv基因构建及其在E.coli中的表达

本研究应用PHA、抗CD3单抗(aCD3)和rIL-2共同刺激人外周血单个核细胞(PBMC),诱生、扩增新型抗肿瘤效应细胞PHA-aCD3LAN,并与PHA-LAk和CD3AK细胞在某些生物学特性方面进行了比较,结果表明,PHA、aCD3和IL-2具有协同增强效应、使PHA-aCD3LAK细胞的增殖能力、细胞毒活性、mIL-2Ra的表达水平及对IL-2的利用均高于PHA-LAK和CD3AK细胞;三组效应细胞均为异质性细胞群体,均以CD3~ CD8~ T细胞为主,而PHA-aCD3LAK的CD8~ 细胞百分率高于其它两组细胞.采用PHA-aCD3LAK可进一步提高LAK细胞的数量和活性,具有重要的临床应用前景     

抗人卵巢癌-抗人CD3单链双特异性抗体体外介导的细胞毒作用及其机制

目的了解抗人卵巢癌-抗人CD3（BHL—I）单链双特异性抗体（scBsAb）体外介导的外周血淋巴细胞（PBL）对靶细胞SKOV3的细胞毒作用及可能的机制。方法二苯基溴化四氮唑蓝（MTr）法检测BHL-I体外介导PBL对SKOV3细胞的杀伤作用；逆转录-聚合酶链反应（RT—PCR）检测BHL—I介导的细胞毒作用过程中效应细胞PBL对穿孔素（perforin）、颗粒酶（GrB）mRNA表达的影响；酶联免疫吸附（ELISA）法检测细胞培养上清液中人肿瘤坏死因子-α（hTNF—α）和人干扰素-γ（hIFN-γ）含量的变化。结果BHL-I体外介导PBL对SKOV3细胞的细胞毒作用显著高于对MCF-7细胞的作用（P〈0.01），并且在效靶比为12．5：1、作用时间为36h、BHL-I浓度为25μg/ml时，PBL对靶细胞的细胞毒作用最为显著；BHL—I体外介导的细胞毒作用中，PBL表达perforin、GrBmRNA及混合细胞培养上清液中hTNF—α和hIFN-γ的含量均显著升高，并且白介素2（IL-2）的存在有利于这些因子的表达。结论BHL—I介导PBL对靶细胞的细胞毒作用具有一定的特异性，并且IL-2能增强BHL—I介导PBL的细胞毒作用。     

Development and Characterization of Chimeric Anti-carcinoembryonic Antigen Monoclonal Antibodies and Their Fab Fragments

In an attempt to reduce the immunogenicity of two different murine anti-carcinoembryonic antigen (CEA) monoclonal antibodies (MAbs), KM10 and A10, we produced recombinant mouse/human chimeric MAbs and the respective Fab fragments carrying the variable regions of the murine MAbs. Chimeric A10 Fab fragment was expressed in Escherichia coli , and produced in large quantities in a mini-jar fermentation system. In competitive binding assays, chimeric MAbs and their Fab fragments showed identical specificity to human CEA epitopes, as compared to the parental MAbs or Fab fragments. Both chimeric Fab fragments exhibited strong immunohistochemical reactivity with various gastrointestinal carcinomas and no reactivity with CEA-related antigens, such as NCA (nonspecific cross-reacting antigen) or BGPI (biliary glycoprotein I). Furthermore, chimeric KM10 MAb elicited substantially higher antibody-dependent cellular cytotoxicity than the murine MAb. Complement-dependent cytotoxicity in vitro was much weaker with chimeric KM10 MAb. These results indicate that chimeric MAbs or Fab fragments could potentially replace the parental murine antibodies or their Fab fragments in therapy or diagnosis of human gastrointestinal carcinomas.     

Effect of Accessory Cells on Stimulation of Murine T-Cell Leukemia with Antibodies to the CD3/T Cell Antigen Receptor Complex

Stimulation of EL4 and RL  

     

Serial killing of tumor cells by cytotoxic T cells redirected with a CD19-/CD3-bispecific single-chain antibody construct

Certain bispecific antibodies exhibit an extraordinary potency and efficacy for target cell lysis by eliciting a polyclonal T-cell response. One example is a CD19-/CD3-bispecific single-chain antibody construct (bscCD19xCD3), which at femtomolar concentrations can redirect cytotoxic T cells to eliminate human B lymphocytes, B lymphoma cell lines and patient-derived malignant B cells. Here we have further explored the basis for this high potency. Using video-assisted microscopy, bscCD19xCD3 was found to alter the motility and activity of T cells from a scanning to a killing mode. Individual T cells could eliminate multiple target cells within a 9 hr time period, resulting in nuclear fragmentation and membrane blebbing of target cells. Complete target cell elimination was observed within 24 hr at effector-to-target cell ratios as low as 1:5. Under optimal conditions, cell killing started within minutes after addition of bscCD19xCD3, suggesting that the rate of serial killing was mostly determined by T-cell movement and target cell scanning and lysis. At all times, T cells remained highly motile, and no clusters of T and target cells were induced by the bispecific antibody. Bystanding target-negative cells were not detectably affected. Repeated target cell lysis by bscCD19xCD3-activated T cells increased the proportion of CD19/CD3 double-positive T cells, which was most likely a consequence of transfer of CD19 from B to T cells during cytolytic synapse formation. To our knowledge, this is the first study showing that a bispecific antibody can sustain multiple rounds of target cell lysis by T cells.     

Detection of Bone-type Alkaline Phosphatase by Monoclonal Antibodies Reacting with Human Osteosarcoma-associated Antigen

The antigen detected by monoclonal antibodies reacting with human osteosarcoma-associated antigen was shown to he a phosphatidyl-inositol (Pl)-glycan-anchored protein, which can be released from the cell surface by PI-specific phospholipase C-treatment. The antigen detected by 2D3 and 2H10 antibodies exhibited alkaline phosphatase activity. Both antibodies strongly reacted with bone-type alkaline phosphatase. However, importantly, immunohistochemical analysis demonstrated that 2D3 and 2H10 did not react with alkaline phosphatase present in kidney or liver. In addition, neither placental nor intestinal alkaline phosphatase was recognized by 2D3 and 2H10 antibodies. These results indicated that two monoclonal antibodies, 2D3 and 2H10, are highly specific for bone-type alkaline phosphatase and can distinguish bone alkaline phosphatase from liver alkaline phosphatase in spite of the fact that liver and bone alkaline phosphatase are encoded by the same gene.     

Preparation and Characterization of a Murine Monoclonal Antibody (MDR3M) Reactive with mdr3 Gene Product

A murine monoclonal antibody (MDR3M) (isotype: IgM) reactive with mdr3 gene product was generated by immunizing mice with mdr3 -specific peptide (H₂N-¹²WRPTSAEGDFELGISSKQKRKKTKTVKMI⁴¹G-COOH) and hybridizing the primed mouse splenic B cells with X63-Ag8,6.5.3 mouse plasmacytoma cells. MDR3M did not cross-react with mdr1 gene product. This monoclonal antibody may be useful for analyzing the role of mdr3 gene product in cells and tissues.     

Clinical Evaluation of an Immunoradiometric Assay for CA15-3 Antigen Associated With Human Mammary Carcinomas: Comparison With Carcinoembryonic Antigen

Serum levels of CA15-3, a mammary tumor associated antigen recognizedby two different murine monoclonal antibodies (115D8 and DF3),were investigated in patients with mammary carcinoma and otherbenign or malignant diseases. The reference value of the serumCA15-3 level was obtained as 24 units/ml at the 99% confidencelimit among healthy individuals (n = 462). Elevation of serumCA15-3 levels was observed in 24.3% of overall patients withmammary carcinoma. Serum CA15-3 levels in breast cancer patientscorrelated with the clinical stage; higher percentages of positivitywere observed in those with advanced breast cancer (stage IV,64.7%, recurrent, 52.4% and metastatic, 70.3%). Furthermore,elevated serum CA15-3 levels in breast cancer patients respondedwell to the effect of therapy. Although the serum CA15-3 testgave percentages of positivity of breast cancer similar to thosefound by the serum CEA test, the serum CA15-3 test revealedlower percentages of posi-tivity than the serum CEA test amongpatients with benign breast lesions, liver cirrhosis or othercarcinomas. These results suggest that the serum CA15-3 antigenlevel provides a very useful marker for diagnosis and clinicalmonitoring of patients with breast cancer.     

Cytomegalovirus Retinitis and Retinal Detachment following Chimeric Antigen Receptor T Cell Therapy for Relapsed/Refractory Multiple Myeloma

Cytomegalovirus (CMV) retinitis is a rare end-organ disease of CMV infection and is a marker of severe immunosuppression, especially in human immunodeficiency virus (HIV)-positive patients. In multiple myeloma (MM) patients, CMV retinitis has been reported in the post-transplant setting, with an incidence lower than 0.2%, and in patients receiving lenalidomide. Here, we describe the first case of CMV retinitis in myeloma patients following B-cell maturation antigen (BCMA)-targeted chimeric antigen receptor T (BCMA CAR-T) cell therapy. In addition to CMV, the patient developed multiple infections including a mouth ulcer, pneumonia, and fungal enteritis. While the complete remission (CR) status of MM was maintained, he regained a visual acuity of 20/1000 after appropriate ophthalmologic treatment. This single case illustrates the potential of BCMA CAR-T therapy to induce profound humoral immunosuppression, and demonstrates an imperative need for an established standard of monitoring and prophylaxis of post-CAR-T infections.