抗人卵巢癌×抗人CD3×抗CD28VH单链三特异抗体的胞内可溶表达、纯化及体外活性测定

目的　研究抗人卵巢癌 (ovariancarcinoma ,oc)×抗人CD3×抗CD2 8VH 单链三特异抗体(singlechaintrispecificantibody,scTsAb)在大肠杆菌中的可溶表达与纯化及纯化后产物的活性测定 ,从而为其应用于卵巢癌治疗的临床研究打下基础。方法　将已构建的scTsAb表达载体转化大肠杆菌BL2 1(DE3)Star菌株 ,采用低温 (30℃ )、低剂量IPTG(0 .2mmol L)诱导 ,进行胞内可溶表达。根据抗卵巢癌三特异抗体 (ocTsAb)等电点较高 (pI9.0 ) ,而菌体蛋白大多为酸性蛋白的特点 ,利用DEAE弱阴离子交换层析(pH8.0 )进行一步纯化 ,并利用ELISA及FACS的方法检测纯化后抗卵巢癌三特异抗体的活性。结果　(1)SDS PAGE鉴定低温诱导时可溶比例达到 5 6 %。 (2 )绝大多数菌体蛋白被DEAE层析柱吸附 ,而抗卵巢癌三特异抗体在穿透液中流出 ,SDS PAGE检测纯度达到 90 %。 (3)ELISA结果显示纯化后的抗卵巢癌三特异抗体与重组CD2 8纯抗原 ,Jurkat(CD3 )细胞膜提取抗原 ,SKOV3细胞膜提取抗原均有特异性结合。 (4 )FACS结果证明纯化后的抗卵巢癌三特异抗体与Jurkat(CD3 )活细胞、SKOV3活细胞有特异性结合。结论　低温诱导胞内可溶表达的抗人卵巢癌×抗人CD3×抗CD2 8VH 单链三特异抗体经弱阴离子交换层析一步纯化后仍保持原有免疫学活性 ,这     

抗VEGFR2/抗CD3双特异单链抗体的表达及初步活性检测

目的:构建和表达抗血管内皮细胞生长因子受体2(VEGFR2)/抗CD3双特异单链抗体(bscVEGFR2×CD3),及亲和活性测定。方法:设计抗VEGFR2/抗CD3双特异单链抗体基因序列,由公司合成并亚克隆入真核表达载体pcDNA3.1(+)中,脂质体法转染中国仓鼠卵巢细胞(CHO),筛选高效分泌表达bscVEGFR2×CD3的克隆株。表达产物经Ni-NTA柱纯化,120 g/L SDS-PAGE电泳及Western blot鉴定。应用流式细胞术(FCM)检测生物学活性。结果:bscVEGFR2×CD3重组表达载体测序证实序列正确。bscVEGFR2×CD3能够在CHO细胞中进行分泌表达,筛选出6株高表达克隆株。120 g/L SDS-PAGE显示相对分子质量(Mr)约56 000有1条带,与预期相符,Western blot证明anti-His抗体能与这条蛋白条带发生特异性结合。FCM检测bscVEGFR2×CD3能与CD3+jurkat细胞和VEGFR2+A375细胞特异性结合。结论:成功构建和表达抗VEGFR2/抗CD3双特异单链抗体,该抗体具有与VEGFR2、CD3特异性结合的免疫学活性。     

双特异性单链抗体介导的T细胞对前列腺癌细胞的杀伤作用

目的 研究并比较两种抗人γ-精浆蛋白/抗CD3双特异性单链抗体介导T细胞杀伤前列腺癌细胞的作用.方法 利用流式细胞仪分析双特异性单链抗体(BsAb)及多价双特异性单链抗体(mBsAb)与LNCaP细胞和Jurkat细胞的亲和力;将LNCaP细胞作为靶细胞,分为抗体浓度固定组和效应细胞/靶细胞比例固定组,利用51Cr释放试验评价两种双特异性单链抗体在体外介导T细胞杀伤靶细胞的能力;将Jurkat细胞种植裸鼠后,建立裸鼠前列腺癌模型,并分为非治疗组、对照组、BsAb组和mBsAb组,进一步评价两种双特异性单链抗体在体内介导T细胞杀伤靶细胞的能力.结果 流式细胞仪结果显示:BsAb和mBsAb均可特异性结合LNCaP细胞和Jurkat细胞,阳性结合率分别为56.3%、55.4%和74%、83%.51Cr释放试验结果显示:在体外,BsAb和mBsAb均可介导T细胞对前列腺癌细胞的杀伤,并且T细胞的杀伤效率与抗体浓度和效应细胞/靶细胞比例呈正相关.与非治疗组和对照组比较,接种前列腺癌细胞的裸鼠在体内注射激活的细胞毒T细胞的同时分别接受两种抗体的治疗后,肿瘤生长均明显受到抑制(P＜0.05).另外,体外介导杀伤作用和体内抑制肿瘤生长等方面,多价双特异性抗体的效果明显优于双特异性抗体.结论 同时识别人γ-精浆蛋白和CD3分子的双特异性单链抗体可有效地介导T细胞对前列腺癌细胞的杀伤作用,并且双特异性单链抗体四聚体的形成可明显改善抗体介导杀伤作用的效率.     

人源化抗CD3单链抗体在大肠杆菌中的表达

在以前的工作中 ,我们利用本研究室制备的抗胶质瘤单克隆抗体ＳＺ39通过化学偶联的方法制备了抗ＣＤ3/抗胶质瘤双特异性抗体 ,并在体外细胞毒及荷瘤动物体内试验中取得较好疗效[1,2 ] ,但存在着分子量大 ,穿透力弱 ,免疫原性强 ,制备困难等缺点。因此 ,研制小分子 ,低免疫原性的人源化抗ＣＤ3/抗胶质瘤双特异性抗体是我们正在开展的研究项目之一。目前我们已构建并原核表达了抗胶质瘤单链抗体ＳＺ39 ＳｃＦｖ。本研究构建并表达的人源化抗ＣＤ3单链抗体 ,旨在为下一步制备高效低毒的抗ＣＤ3/抗胶质瘤双特异性抗体提供一个理想的构件。1　材…     

抗人CD4单链抗体的表达及其分离纯化

本研究将构建的抗人ＣＤ３单链抗体基因，克隆到融合蛋白表达载体ｐＧＥＸ－４Ｔ－１，用ＩＰＴＧ诱导表达ＧＳＴ－ＳｃＦｖ融合蛋白，并以ＳＤＳ－ＰＡＧＥ分析，在Ｍｒ为５２０００左右出现的一条新生蛋白带，表达量约占菌体总蛋白的４０％。经初步纯化和复性后，用ＧＳＴ亲和色谱纯化，再经凝血酶水解获得抗人ＣＤ３ＳｖＦｖ，竞争结合抑制实验证明，该表达产物具有ＣＤ３亲和活性。     

CD3／抗CD20双特异双链抗体生物学活性研究

目的 研究抗CD3/抗CD20双特异双链抗体的生物学活性。方法 采用亲和层析法纯化本室构建的抗CD3/抗CD20双特异双链抗体可溶性表达产物,并用SDS-PAGE,Western blot和分子排阻层析鉴定纯化产物;采用FACS法和玫瑰花环试验测定纯化产物与靶细胞的结合活性;采用^3H-TdR掺入实验和^51Cr释放试验测定该双特异双链抗体的生物学性质。结果 纯化的抗CD3/抗CD20双特异双链抗体具有与Jurkat(CD3^ )和Daudi细胞（CD20^ )的结合活性,且能同时与Jurkat和Daudi细胞结合形成玫瑰花环,并能竞争性封闭亲代鼠源性抗体HIT3a和HI47与Jurkat和Daudi细胞的结合位点;该双特异双链抗体具有促进丝分裂原作用和介导激活的T细胞杀伤Daudi细胞的自学成才性。结论 抗CD3/抗CD20双特异双链抗体具有与亲代鼠源性抗体HIT3a和H147相同的性质。且能介导激活的T细胞杀伤表达CD20抗原的肿瘤细胞,是一个有望用于B细胞恶性肿瘤临床治疗的双特异性抗体。     

抗人CD3单链抗体基因的构建及序列分析

本文在已克隆抗人ＣＤ３抗体ＶＨ和ＶＫ基因的基础上，设计并合成了ＰＣＲ引物。两个外侧引物分别含有ＥｃｏＲＩ和ＳａｌＩ酶切位点及起始码和终止码序列，４个内侧引物各含部分连肽基因序列，回收后混合退火。     

抗CD3/抗CD20双特异双链抗体的生物学活性研究

目的研究抗CD3/抗CD20双特异双链抗体的生物学活性.方法采用亲和层析法纯化本室构建的抗CD3/抗CD20双特异双链抗体可溶性表达产物,并用SDS-PAGE,Westernblot和分子排阻层析鉴定纯化产物;采用FACS法和玫瑰花环试验测定纯化产物与靶细胞的结合活性;采用3H-TdR掺入实验和51Cr释放试验测定该双特异双链抗体的生物学性质.结果纯化的抗CD3/抗CD20双特异双链抗体具有与Jurkat(CD3+)和Daudi细胞(CD20+)的结合活性,且能同时与Jurkat和Daudi细胞结合形成玫瑰花环,并能竞争性封闭亲代鼠源性抗体HIT3a和HI47与Jurkat和Daudi细胞的结合位点;该双特异双链抗体具有促有丝分裂原作用和介导激活的T细胞杀伤Daudi细胞的活性.结论抗CD3/抗CD20双特异双链抗体具有与亲代鼠源性抗体HIT3a和HI47相同的性质,且能介导激活的T细胞杀伤表达CD20抗原的肿瘤细胞,是一个有望用于B细胞恶性肿瘤临床治疗的双特异性抗体.     

Development and characterization of a bispecific single-chain antibody directed against T cells and ovarian carcinoma

Bispecific antibodies with specificity for tumor antigen and CD3 have been shown to redirect the cytotoxicity of T cells against relevant tumor. Our objective was to generate single-chain bispecific antibodies (bsSCA) that could retarget mouse cytotoxic T lymphocytes (CTL) to destroy human ovarian carcinoma in a xenogeneic setting. A bsSCA, 2C11 x B43.13, was constructed by genetic engineering and expressed in mammalian cells. Molecular characteristics, binding properties, and ability to retarget CTL were studied. Western blot analysis showed that the product is a 65-kDa protein. Purification of antibodies could be done by single-step affinity chromatography using protein L-agarose with an unoptimized yield of 200 microg/L. BsSCA 2C11 x B43.13 was capable of binding to mouse CD3 and human CA125 as detected by FACS analysis of EL4 and OVCAR Nu3H2 cells, respectively. It could also bridge activated splenic T cells and human ovarian carcinoma as demonstrated by a bridge FACS assay. Redirected mouse CTL could mediate human target cell lysis in a 20-h 51Cr release assay despite that they are xenogeneic. Prolonged incubation of redirected CTL and tumor targets resulted in a dramatic reduction in tumor cell number. CD28 co-stimulation enhanced redirected CTL function in both types of assays. BsSCA 2C11 x B43.13 thus can be used as a preclinical immunotherapeutic model for human ovarian cancer in a xenogeneic setting.     

双特异性抗体对LAK细胞增殖和细胞毒作用影响的体外研究

将抗ＣＤ３与抗ＨＢｓ的单克隆抗体经化学偶联得到双特异性抗体，观察该双特异性抗体对ＬＡＫ细胞增殖和增强细胞毒性的作用。结果显示双特异性抗体显著提高ＬＡＫ细胞与２．２．１５细胞结合率；促进淋巴细胞增殖。１２５Ｉ－ＵｄＲ释放试验检测发现双特异性抗体增强ＬＡＫ细胞对２．２．１５细胞的细胞毒性且与抗体浓度呈正相关。进一步对抗体的特异性研究表明，加入双特异性抗体后ＬＡＫ细胞对２．２．１５细胞毒性作用显著高于对照组。     

A recombinant bispecific single-chain antibody induces targeted,supra-agonistic CD28-stimulation and tumor cell killing

Endowing tumor cells with costimulatory signals for T cell activation has emerged as a promising strategy for tumor immunotherapy. Costimulatory molecules were either transfected into tumor cells to generate vaccines or were fused, e.g. to antibodies against tumor-associated antigens, to achieve targeted T cell costimulation in vivo. Here we report the production and purification of rM28, a recombinant bispecific single-chain antibody directed to a melanoma-associated proteoglycan and to the costimulatory CD28 molecule on human T cells. We found that a dimer of the recombinant molecule, bound to tumor target cells, induced pronounced T cell activation in peripheral blood mononuclear cell preparations without additional TCR/CD3 stimulation being required. The lytic activity generated after 3 days of stimulation effectively prevented tumor cell growth. However, it was unspecific and predominantly mediated by non T cells. Our findings demonstrate that presentation of a CD28 antibody within a suitable recombinant, bispecific format may result in a "targeted supra-agonistic stimulation" of the CD28 molecule, which leads to effective tumor cell killing after induction of unspecifically lytic cells.     

抗HEV中和抗体13D8的单链抗体的构建及表达

目的 :降低HEV中和性单抗 (mAb) 13D8的鼠源性 ,表达其单链抗体 (scFv)。方法 :从分泌 13D8鼠mAb的杂交瘤细胞中 ,通过RT PCR克隆mAb的VL、VH 基因 ,并进一步组装成VH linker VL 型的scFv片段。将scFv片段克隆到pTO T7载体中 ,在大肠杆菌中进行表达。用ELISA、Westernblot检测scFv的活性。结果 :SDS PAGE表明 ,13D8的scFv在E .coli中得到高效表达 ,表达量达菌体总蛋白的 2 6 .8%左右 ,表达产物主要以包涵体的形式存在。间接ELISA和Westernblot检测表明 ,表达的 13D8的scFv能与HEVOFR2区中一段重组蛋白(NE2 )特异结合。竞争ELISA表明 ,scFv与原鼠mAb识别的为同一表位。结论 :成功地表达出具有免疫学活性的 13D8的scFv。     

人源化抗炭疽芽胞杆菌保护性抗原单链抗体的设计和表达

目的:应用抗体"框架区重塑"技术,对鼠单克隆抗体(mAb)框架区进行人源化,制备人源化单链抗体(scFv)并检测其活性。方法:在获得抗炭疽芽胞杆菌保护性抗原鼠mAb(5E1)可变区基因的基础上,保持鼠mAb互补决定区(CDR)不变,选择与框架区同源性最高的人源序列替换鼠mAb的框架区,保留个别关键的鼠源残基。通过融合PCR技术构建人源化的scFv,并在大肠杆菌中进行了表达。表达产物以包涵体形式存在,通过变性、镍柱亲和层析和复性,获得复性后的可溶蛋白。对纯化产物进行了SDS-PAGE、ELISA和抑制炭疽毒素中和活性的检测。结果:人源化后的序列具有与鼠源scFv一致的抗原结合活性和细胞水平的中和炭疽毒素活性。结论:获得了具有功能的人源化的抗体基因序列,为表达具有中和炭疽毒素活性的全分子人源化抗体奠定了基础。     

In vitro and in vivo properties of a dimeric bispecific single-chain antibody IgG-fusion protein for depletion of CCR2+ target cells in mice

The chemokine receptor CCR2 is highly expressed on leukocytes in several inflammatory diseases of both mice and men. Apart from blockade of CCR2 to prevent chemokine-dependent cell migration, depletion of CCR2(+) cells might be a promising strategy for treatment of inflammatory diseases. We therefore designed a bispecific antibody construct with the ability to deplete CCR2(+) target cells in vitro and in vivo. The bispecific antibody construct consists of two single-chain antibody variable fragments (scFv) - one recognizing murine CD3epsilon and the other recognizing murine CCR2 - joined by a short linker and fused to a modified hinge region and the C(H)2 and C(H)3 domains of murine IgG1 for dimerization. The protein was expressed in mammalian cells and purified via its C-terminal histidine tail. In vitro this construct leads to efficient antigen-specific and costimulation-independent activation of T cells and strong lysis of CCR2(+) target cells. In vivo the construct induces an almost complete depletion of CCR2(+)CD11b(+) monocytes from the peripheral blood and spleens of BALB/c mice within 24 h. This recombinant protein construct is a dimeric, bispecific antibody with markedly improved serum levels compared to conventional bispecific single-chain antibodies and the ability to deplete CCR2(+)CD11b(+) monocytes in vivo.     

Generation and characterization of a single-chain anti-EphA2 antibody

Abstract

Recombinant antibody phage library technology provides multiple advantages, including that human antibodies can be generated against proteins that are highly conserved between species. We used this technology to isolate and characterize an anti-EphA2 single-chain antibody. We show that the antibody binds the antigen with 1:1 stoichiometry and has high specificity for EphA2. The crystal structure of the complex reveals that the antibody targets the same receptor surface cavity as the ephrin ligand. Specifically, a lengthy CDR-H3 loop protrudes deep into the ligand-binding cavity, with several hydrophobic residues at its tip forming an anchor-like structure buried within the hydrophobic Eph pocket, in a way similar to the ephrin receptor-binding loop in the Eph/ephrin structures. Consequently, the antibody blocks ephrin binding to EphA2. Furthermore, it induces apoptosis and reduces cell proliferation in lymphoma cells lines. Since Ephs are important mediators of tumorigenesis, such antibodies could have applications both in research and therapy.     

全人源性肝癌单链抗体的表达、纯化及功能鉴定

目的:在大肠杆菌中表达人源性肝癌单链抗体(scFv),并分析他的结合活性。方法:应用噬菌体表面呈现技术获得人源性肝癌scFv,利用重叠延伸PCR将VL和VH基因以(Gly4ser)3linker连接成单链,插入表达载体pET28a( ),诱导目的蛋白表达,对包涵体进行溶解、复性、纯化,得到可溶性目的蛋白,应用非竞争细胞ELISA检测与肝癌细胞结合的特异性及结合能力。结果:在A600为0.8时开始诱导,持续6h,目的蛋白表达量占菌体总蛋白的26%,包涵体经过复性纯化后,得到纯度达到95%的重组scFv,其亲和常数为:3.6×107mol/L。结论:实现了人源性肝癌scFv的蛋白表达,抗体蛋白与肝癌细胞具有较强的特异性结合能力,为今后进行免疫学检测和开发肿瘤靶向治疗提供了研究手段。     

Development trends for generation of single-chain antibody fragments

Recombinant antibodies are increasingly being employed as therapeutic agents especially in combination with anti-cancer drugs. The single-chain antibody fragments are small antigen-binding proteins which provide the most commonly used antibody formats for diagnostic and therapeutic purposes. These antibody fragments have more rapid tumor penetration and clearance from the serum relative to full-length monoclonal antibodies. There are in vitro antibody-display technologies such as phage display, cell surface display, ribosome display and mRNA display that can be used to isolate high specificity and affinity single-chain antibodies against a wide variety of targets. We review these strategies for generation of stable and active antibody fragments in the present article.