人源抗破伤风毒素单链抗体(ScFv)的原核表达、纯化及功能鉴定

实验通过DNA重组技术从一株可中和破伤风毒素的人源单克隆抗体细胞(G6)中扩增出了抗体VH、VL的基因,通过重叠PCR使连接片段与VH、VL连接成单链ScFv。经测序证实VH、VL为抗体的可变区序列,命名为ScFv-G6。将ScFv-G6连接转化PET/26b质粒,构建了抗体的表达载体,被命名为PET/26b/ScFv-G6。以该载体在大肠杆菌中分泌表达产物经Ni-亲和柱纯化后的小鼠试验证实,可抵抗破伤风毒素的攻击,表明为中和抗体。具有组织穿透力强,不易过敏,可直接靶向于毒素等特点,适合于破伤风的防治,具有重要的应用价值。

抗人肝癌MDscFV基因的表达及其免疫活性初步研究

将抗人肝癌单克隆抗体MD的重链可变区VH和轻链可变区VL基因重组,并使其表达。采用PT-PCR技术扩增VH及VL基因,通过重叠延伸拼接PCR在VH和VL基因间引入连接短肽,体外构建加MDscFV基因,经过常规转化与筛选,诱导表达蛋白。MDscFV基因全长为732bp,VH354bp位于上游;VL330bp位于下游。重组蛋白相对分子量36kDa。scFV保留了与亲本抗体MD相似的免疫活性。成功地构建了抗人单链抗体MDscFV,并获得了较高水平的功能性表达。

Anti-CD3 scFv-B7.1真核表达载体的构建及在COS-7细胞中的初步表达

目的 构建anti CD3scFv B7.1真核表达载体 ,并进行初步表达。方法 采用重叠延伸拼接法 (splicingbyoverlapextention ,SOE)将anti CD3scFv和B7.1(V +C)两个基因片段通过spacer序列连接 ,将融合基因克隆入T载体 ,并测序证实。在此基础上构建真核表达载体pcDNA/anti CD3scFv B7.1,并经脂质体法转染COS 7细胞 ,免疫组织化学法检测表达。结果 获得了序列与预期完全相同的融合基因 ;构建了抗CD3scFv B7.1融合基因真核表达载体 ;在COS 7细胞中获得初步表达。结论 成功构建及表达抗CD3scFv B7.1融合基因真核表达载体 ,为进一步研究抗CD3scFv B7.

抗TfR-scFv-EGFP融合蛋白的构建与表达

目的:抗转铁蛋白受体单链抗体(TfR-scFv)-EGFP融合蛋白真核表达载体的构建与表达。方法:设计两对引物引入连接肽(Gly4Ser)3以及酶切位点HindⅢ和BamHⅠ,采用重叠延伸PCR扩增与构建具有前导肽的L-VH-Linker-VL单链抗体基因,亚克隆至pEGFP-N1,转染COS-7细胞,倒置相差荧光显微镜下观察荧光蛋白表达,流式细胞术(FCM)检测细胞分泌上清与乳腺癌细胞MCF-7及黑色素瘤细胞A375结合活性。结果:测序表明获得了正确的L-VH-Linker-VL单链抗体基因序列;亚克隆至pEGFP-N1后,表达载体转染COS-7细胞,经荧光显微镜观察转染细胞,及通过流式细胞术(FCM)检测细胞分泌上清,证实抗TfR-scFv-EGFP融合蛋白在转染细胞中分泌性表达,并能够与天然高表达TfR的细胞特异性结合。结论:抗TfR-scFv-EGFP融合蛋白真核表达载体构建成功,其表达产物具有与TfR阳性细胞结合的活性。

抗乙型肝炎表面抗原单链抗体(ScFv)的原核表达、纯化及鉴定

从抗HBsAg鼠单抗的杂交瘤细胞提取RNA,经反转录得到cDNA,进一步扩增得到鼠重链可变区基因(VH)和轻链可变区基因(VL),按VH-linker-VL的结构将VH、VL基因拼接成单链抗体(scFv)基因;经测序正确后进一步构建了表达重组体p26HBSc并在E.coli中表达,得到一约30kD的外源蛋白;纯化后经ELISA检测与HBsAg有较高的亲和力活性,为下一步的人源化改造奠定了基础。

H_3N_2亚型犬流感病毒鼠/犬嵌合抗体scFv-Fc的制备与活性分析

[目的]为减少鼠源单克隆抗体的异源性在犬临床治疗中引起的宿主免疫排斥反应,针对H_3N_2亚型犬流感病毒(CIV),制备具有犬源抗体恒定区基因(Fc)的鼠/犬嵌合抗体。[方法]从产生具有良好中和活性CIV单抗的鼠源杂交瘤细胞株中扩增抗体重链和轻链可变区基因,通过重叠延伸PCR(SOE-PCR)获得单链抗体基因(scFv)片段,同时从犬外周血单核细胞中扩增得到犬源抗体Fc片段;分别构建单链抗体与嵌合抗体表达载体,通过大肠杆菌表达、纯化后调整蛋白浓度为1 mg·mL^(-1),检测单链抗体与嵌合抗体的ELISA和血凝抑制(HI)效价,并分析其对病毒感染细胞的中和活性。[结果]获得的H_3N_2亚型CIV鼠源scFv的相对分子质量为45×10~3,ELISA及HI效价分别为1∶640(1.56μg·mL^(-1))和1∶160(6.25μg·mL^(-1)),中和效价为1∶160(6.25μg·mL^(-1));鼠/犬嵌合抗体scFv-Fc的相对分子质量为80×10~3,ELISA及HI效价分别为1∶2 560(0.39μg·mL^(-1))和1∶640(1.56μg·mL^(-1)),中和效价为1∶40(25μg·mL^(-1))。[结论]成功制备了H_3N_2亚型CIV鼠/犬嵌合抗体,为犬流感的临床治疗提供了物质基础。

Antioxidant Effect of Human Selenium-containing Single-chain Fv in Rat Cardiac Myocytes

Reactive oxygen species（ROS） plays a key role in human heart diseases. Glutathione peroxidase（GPX） functions as an antioxidant as it catalyzes the reduction of hydroperoxide. In order to investigate the antioxidant effect of human selenium-containing single-chain Fv（Se-scFv-B3）, a new mimic of GPX, a model system of hydrogen peroxide（H202）-induced rat cardiac myocyte damage was established. The cardiac myocyte damage was characte- rized in terms of cell viability, lipid peroxidation, cell membrane integrity, and intracellular H202 level. The Se-scFv-B3 significantly reduced H2O2-induced cell damage as shown by the increase of cell viability, the decline of malondialdehyde（MDA） production, lactate dehydrogenase（LDH） release, and intracellular H2O2 level. So Se-scFv-B3 may have a great potential in the treatment of human heart diseases induced by ROS.

Construction and Analysis of Three-dimensional Graphic Model of Single-chain Fv Derived from an Anti-human Placental Acidic Isoferritin Monoclonal Antibody by Computer

Summary: A three-dimensional (3D) graphic model of a single-chain Fv (scFv) which was derived from an anti-human placental acidic isoferritin (PAF) monoclonal antibody (MAb) was construct- ed by a homologous protein-predicting computer algorithm on Silicon graphic computer station. The structure, surface static electricity and hydrophobicity of scFv were investigated. Computer graphic modelling indicated that all regions of scFv including the linker, variable regions of the heavy (VH) and light (VL) chains were suitable. The VH region and the VL region were involved in composing the 'hydrophobic pocket'. The linker was drifted away VH and VL regions. The complementarity determining regions (CDRs) of VH and VL regions surrounded the 'hydrophobic pocket'. This study provides a theory basis for improving antibody affinity, investigating antibody structure and analyzing the functions of VH and VL regions in antibody activity.

人源抗肝癌单链抗体scFv-CD3ζ基因真核载体的构建

目的克隆正常人T细胞CD3ζ的胞内区、跨膜区基因,将其与二硫键稳定的人源化抗肝癌的单链抗体scFv的基因克隆入真核表达载体,为制备肝癌靶向性嵌合锚定T细胞奠定基础,并探讨其对肝癌的杀伤活性。方法应用PCR法将二硫键稳定的人源化的单链抗体scFv的基因克隆入真核细胞表达载体pcDNA3,在5'端及3'端分别引入相应酶切位点;用RT-PCR法从正常外周血人T细胞扩增出CD3ζ的胞内区、跨膜区基因,然后将其克隆于scFv的下游,并在5'端及3'端引入相应的酶切位点。结果二硫键稳定的人源化抗肝癌的单链抗体scFv的cDNA片段为735bp,与已知的序列相符;CD3ζ的胞内区、跨膜区的cDNA片段为294bp,与GeneBank公布的序列一致。重组的表达载体经酶切琼脂糖电泳及测序加以证实。结论完成了二硫键稳定的人源化抗肝癌的单链抗体scFv及CD3ζ的胞内区、跨膜区融合基因真核表达载体pcDNA3-scFv-CD3ζ的构建,为制备肝癌靶向性嵌合锚定T细胞奠定了实验基础。

Expression, purification and targeting therapy of mscFv_(25)-TNFα against hepatocellular carcinoma

Objective: To Obtain purified genetic eogineering recombinant scFv-fusion protein with potentialities of clinical application. Methods: Mouse anti-hepatocellular carcinoma (HCC) single chain Fv fragment (mscFv25 ) was fused to human TNFa gene, then mscFv25-TNFa was subcloned into prokaryotic GST fusion expression vector pGEX 4T-l, and ex-. pressed in the host E. colt induced by IPTG. Expressed proteins as inclusion bodies were solubilized, solubilized and purified by GST affinity chromatography. The cytotoxity of mscFv25-TNFa was evaluated on SMMC-7721 by MTT, and the targeting therapeutic value was revealed in nude mice bearing HCC xenografts. Results: The specificity and affinity of mscFv25-TNFa were not markedly reduced compared with its parental antibody HAb25 against SMMC-7721 antigen. In vitro target cell SMMC-7721 was insensitive to mscFv25-TNFa. In the mscFv25-TNFa had certain targeting cytotoxicity and caused complete tumor disappearance in 4 of 14 mice, and the side effects of TNFa were much weaker in mscFv25-TNFa group than in group. Conclusion: SMMC-7721 may belong to the TNF-resistant type. While in the trial, mscFv25-TNFa caused complete tumor disappearance in 4 of 14 mice, but no disappearance in TNFa group, suggesting that mscFv25-TNFa had certain tar geting cytotoxicity, and the cytotoxicity of TNFa depended on some other factors in the. It may damage vascular endothelial cell and lead to ischemic necrosis, or induce the tumor cell to apoptosis and some agents to play the the of actinmycin-D in vivo. The targeting of mscFv25 can diminish unspecific cytotoxicity of TNFa, thus attenuate the side effects of TNFa.

THE CONSTRUCTION AND EXPRESSION OF THE MURINE SCFV GENE IN E.COLI AGAINST HUMAN CERVICAL CANCER

Objective To obtain the gene of murine Single chain Fv fragment (ScFv) against human cervical cancer and to express it in E.coli . Methods The variable region gene fragments of the heavy and light chains, which were amplified respectively using recombinant DNA techniques from CsA125 hybridoma cells, were spliced together through a flexible linker to ScFv against human cervical cancer. The ScFv genes were then cloned into expression vector pCANTAB 5E and expressed in E.coli HB2151 and TG1 respectively. The soluble ScFv were characterized by SDS-PAGE and Western blot. The antigen-binding activities of the soluble and phage displayed ScFv were assayed by ELISA and cell immunohistochemical analysis. Results The expressed ScFv antibodies were soluble and phage displayed. The soluble ScFv secreted and expressed in E.coli HB2151 induced by IPTG were confirmed with SDS-PAGE, Western blot and ELISA. The specific binding capacity of the soluble and phage displayed ScFv to the surface associated antigen of human cervical cancer cell line was further confirmed with immunohistochemical studies. Conclusion The soluble and phage displayed ScFv expressed in E.coli against human cervical cancer showed high, specific affinity for the cervical cancer cell line surface associated antigen.

Fv及其衍生物重组基因的构建

利用蛋白酶解法从完整抗体制备 Fv 片段是个费时费力的繁琐过程,且对于多种McAb 的 Fv 片段制备是不成功的。利用 PCR 方法,从抗体产生细胞中获得可变区基因,并利用基因工程技术,构建不同的目的基因:重链可变区(VH)和轻链可变区(VL)相连构成 Fv,VH 和VL 连入一基因编码的连接肽(Linker)构成 scFv,两个 scFv 相连构成双价 scFv,两种功能 scFv相连构成双功能 scFv 等。本文就 Fv 抗体及其衍生物基因的体外构建作一综述。

Disulfide-stabilized single-chain antibody-targeted superantigen: Construction of a prokaryotic expression system and its functional analysis

AIM: To construct the expression vector of B3 (scdsFv)-SEA (D227A) and to identify its binding and cytotoxic ability to B3 antigen positive carcinoma cell lines.METHODS: This fusion protein was produced by a bacterial expression system in this study. It was expressed mainly in the inclusion body. The gene product was solubilized by guanidine hydrochloride, refolded by conventional dilution method, and purified using SP-sepharose cation chromatography.RESULTS: The expression vector B3 (scdsFv)-SEA-PETwas constructed, the expression product existed mainly in the inclusion body, the refolding product retained the binding ability of the single-chain antibody and had cytotoxic effect on HT-29 colon carcinoma cells. The stability assay showed that the resulting protein was stable at 37 ℃.CONCLUSION: This genetically engineered B3 (scdsFv)-SEA fusion protein has bifunction of tumor targeting and tumor cell killing and shows its promises as an effective reagent for tumor-targeted immunotherapy.

Novel Selenium-containing Human Single-chain Variable Fragment with Glutathione Peroxidase Activity from Computer-aided Molecular Design

In order to enhance the glutathione peroxidase（GPX） catalytic activity of the selenium-containing single-chain variable fragments（Se-scFv）, a novel human scFv was designed on the basis of the structure of human antibody and optimized via bioinformatics methods such as homologous sequence analysis, three-dimensional（3D） model building, binding-site analysis and docking. The DNA sequence of the new human scFv was synthesized and cloned into the expression vector pET22b（＋）, then the scFv protein was expressed in soluble form in Escherichia coli BL21（DE3） and purified by Ni2＋-immobilized metal affinity chromatography（IMAC）. The serine residue of scFv in the active site was converted into selenocysteine（Sec） with the chemical modification method, thus, the human Se-scFv with GPX activity was obtained. The GPX activity of the Se-scFv protein was characterized. Compared with other Se-scFv, the new human Se-scFv showed similar efficiency for catalyzing the reduction of hydrogen peroxide by glutathione. It exhibited pH and temperature dependent catalytic activity and a typical ping-pong kinetic mechanism.

Screening and identification of human Zn T8-specific single-chain variable fragment (scFv) from type 1 diabetes phage display library

Zinc transporter 8 （ZnT8） is a major autoantigen and a predictive marker in type 1 diabetes （T1D）. To investigate ZnT8-specific antibodies, a phage display library from TID was constructed and single-chain antibodies against ZnT8 were screened and identified. Human T1D single-chain variable fragment （scFv） phage display library consists of approximately 1 ~ l0s clones. After four rounds of bio-panning, seven unique clones were positive by phage ELISA. Among them, C27 and C22, which demonstrated the highest affinity to ZnT8, were expressed in Escherichia coli Topl0F＇ and then purified by affin- ity chromatography. C27 and C22 specifically bound ZnT8 N/C fusion protein and ZnT8 C terminal dimer with one Arg325Trp mutation. The specificity to human islet cells of these scFvs were further confirmed by immunohistochemistry. In conclusion, we have successfully constructed a T1D phage display antibody library and identified two ZnT8-specific scFv clones, C27 and C22. These ZnT8-specific scFvs are potential agents in immunodiagnostic and immunotherapy of T1D.

大肠杆菌表达的单链抗体柱复性的研究

对包含体表达的抗乙肝病毒表面抗原（ＨＢｓＡｇ）的单链抗体（ＳｃＦｖ）纯化复性进行了探索．尝试了利用金属螯合亲和层析和凝胶层析柱进行柱上在位复性的可行性．对包含体表达的ＳｃＦｖ进行透析复性与柱复性，比较其相对复性率及蛋白质回收率，发现柱上复性效果优于传统的透析复性．抗ＨＢｓＡｇＳｃＦｖ经凝胶色谱ＳｅｐｈａｃｙｌＳ２００柱复性的相对复性率为９８％，蛋白质回收率为８１％．由于将纯化复性同步进行，简化了操作程序。

大容量人源噬菌体抗体库的构建

目的:构建大容量易于改造成Diabody的噬菌体单链抗体库,筛选人源性抗体。方法:从正常成人外周血和新生儿脐血中分离淋巴细胞提取RNA,经RT-PCR扩增轻重链可变区基因(VL和VH),通过重叠PCR(over-lapPCR)将VL和VH拼接成单链抗体(ScFv)基因(其中VH两侧是两个非同源的loxp基因),并克隆入噬菌体表达载体PDF,得到初级噬菌体抗体库。将初级抗体库以高MOI超感染Cre+菌株BS1365,通过loxp-cre定位重组系统,介导轻重链在菌内重组配对,然后低感染XL1-Blue菌,得到大容量的次级抗体库。以多种不同抗原对库进行筛选,得到多样性较好的特异性抗体。结果:经超感染重组,得到1·2×1010的大容量抗体库。经三种蛋白抗原筛选,均得到多株特异性较好的噬菌体抗体,并成功构建为活性较好的Diabody。结论:经Loxp-Cre定位重组系统在单细胞内重组,能够高效地构建大容量噬菌体单链抗体库。

抗血小板膜糖蛋白单克隆抗体SZ-21基因克隆及单链抗体的构建和表达

目的将能与血小板膜糖蛋白 a特异结合的单克隆抗体 SZ- 2 1构建成单链抗体 ,为其临床应用奠定基础。方法通过逆转录及多聚酶链反应 ,扩增并克隆 SZ- 2 1的可变区基因 VH、VL ,经测序后构建 SZ- 2 1单链抗体 (SZ- 2 1Sc Fv) ,在大肠杆菌中进行表达。EL ISA和 Western印迹检测其与血小板的结合特性。结果 VH、VL 可变区基因符合小鼠抗体可变区特征 ,SZ- 2 1Sc Fv基因拼接正确。表达产物除少量为分泌型外 ,主要以包涵体形式存在 ,表达量占菌体蛋白的 2 1%。经过变性和复性后 ,该单链抗体保留了与血小板特异结合的能力。结论成功表达了 SZ- 2 1单链抗体 ,该小分子抗体具有特异结合血小板的能力 ,有望用于抗血栓治疗。

日本血吸虫未成熟卵单链抗体库的构建、筛选及初步应用

运用噬菌体展示技术构建日本血吸虫未成熟虫卵可溶性抗原(SIEA)单链抗体(scFv)表达文库,以天然分子候选疫苗SIEA26～28ku为靶抗原筛选SIEA单链抗体库,获得特异性单链抗体.并将该scFv基因亚克隆至原核高效表达载体PET32a,诱导SIEA26～28ku特异性scFv大量表达.随后以此为探针筛选日本血吸虫尾蚴cDNA文库,以期获得SIEA26～28ku天然分子候选疫苗相关的编码基因.结果显示,所获得的SIEA26～28ku特异性scFv,表达量高,采用该探针初步筛选出相关基因核糖体蛋白S4.SIEA26～28ku特异性scFv的获得,为进一步筛选、分析鉴定抗日本血吸虫病天然分子候选疫苗SIEA26～28ku的编码基因奠定了基础.

β-淀粉样蛋白特异性单链抗体的制备及鉴定

目的制备1株人源性的β-淀粉样蛋白(Aβ)特异性单链抗体(scFv),并进行性能鉴定。方法利用噬菌体展示技术,用20个AD病人的外周血B细胞首次构建了AD患者的单链可变区噬菌体抗体库。以Aβ1-40为靶,挑选出77个阳性抗体克隆,从中筛选出一株抗Aβ单链抗体H1,对其重链和轻链可变区基因进行测序分析。通过表达载体pET28a(+)对目的蛋白进行大量表达,并利用Western-blot对单链抗体H1的免疫活性进行鉴定。结果成功构建出AD患者的单链可变区噬菌体抗体库,库容量为1.5×106。从库中筛选并表达出一株抗Aβ1-40的单链抗体H1,DNA测序结果证实了其抗体的基因结构及氨基酸序列。Western-blot检测证实该抗体可特异性结合Aβ1-40。结论利用噬菌体抗体库技术可成功制备Aβ肽特异性单链抗体,为AD患者的临床诊断和被动免疫治疗提供了一种新的可供选择的途径。