A new approach for producing polyclonal antibodies using impure antigens

A new convenient approach has been designed to produce polyclonal antibodies (PcAb). The approach is based on the principle of the immunoglobulin (Ig) class switch in the immune response. We produced six different antibodies (Ab) against calcineurin A subunit (CNA). CNA, His-tagged calcineurin A subunit (His-CNA), single chain calcineurin (CNB-CNA) and single chain calcineurin–calmodulin complex (CaM-CNB-CNA) were expressed in Escherichia coli (E. coli) BL21 strain, and they were used to immunize male BALB/c mice. These Ab were examined by enzyme-linked immunosorbent assay (ELISA) and western blot analysis. The results clearly demonstrated that the specificity of the Ab produced by different protein samples was much higher than that of the Ab produced by a single sample. We used CNA, CaM-CNB-CNA and His-CNA to immunize mice in turn and obtained monospecific PcAb against CNA fortunately by our new approach. Remarkably, our approach not only offered a simple and general alternative to other methods for producing PcAb described previously, but also disclosed a novel process of immunization that could be used to produce monoclonal antibodies (mAb).     

Effect of metal ions on the activity of the catalytic domain of calcineurin

Calcineurin (CN) is a heterodimer, composed of a catalytic subunit (CNA) and a regulatory subunit (CNB). There are four functional domains present in CNA, which are catalytic domain (CNa), CNB-binding domain (BBH), CaM-binding domain (CBH) and autoinhibitory domain (AI). It has been shown previously that the in vitro activity of calcineurin is relied primarily on the binding of metal ions. Mn2+ and Ni2+ are the most crucial cation-activators for this enzyme. In order to determine which domain(s) in CN is functionally regulated by metal ions, the rat CNA alpha subunit and its catalytic domain (CNa) were cloned and expressed in E. coli. The effects of Mn2+, Ni2+ and Mg2+ on the catalytic activity of these purified proteins were examined. Our results demonstrate that all the metal ions tested in this study activated either CNA or CNa. However, the activation degree of CNa by the metal ions was much higher than that of CNA. In term of different metal ions, the activating extents to CNA and CNa were different. To CNA, the activating order from high to low was Mg2+ > > Ni2+ > Mn2+, but Mn2+ > Ni2+ > > Mg2+ to CNa. No effect of CaM/Ca2+ and CNB/Ca2+ on the activity of CNa was observed in our experiments. Moreover, a weak interaction (or untight coordination binding) between metal ions and the enzyme molecule was also identified. These results suggest that the activation of these enzymes by the exogenous metal ions might be via both regulating fragment of CNA (including BBH, CBH and AI) and catalytic domain (CNa), and mainly via regulating fragment to CNA and mainly via catalytic domain to CNa. The activating extents of metal ions via catalytic domain were higher than that via regulating fragment. The results obtained in this study should be very useful for understanding the molecular mechanism underlying the interaction between calcineurin and metal ions, especially Mn2+, Ni2+ and Mg2+.     

大肠杆菌FtsZ蛋白原核表达及多克隆抗体的制备与鉴定

为制备特异性抗大肠杆菌丝状热敏蛋白Z(Escherichia coli filamentous thermosensitive protein Z,Ec-FtsZ)多克隆抗体,将Ec-FtsZ基因进行化学合成后连接pET-22b(+)表达载体,构建重组质粒Ec-FtsZ-pET-22b(+)。将重组质粒转化到大肠杆菌E.coli BL21(DE3)中进行Ec-FtsZ原核表达与表达条件优化,以HisTrap层析柱进行Ec-FtsZ的分离纯化,再以孔雀绿法进行Ec-FtsZ GTPase(Guanosine triphosphatase)活性测定。使用纯化的Ec-FtsZ为抗原免疫大鼠制备多克隆抗体,经酶联免疫吸附测定实验(Enzyme-linked immunosorbent assay,ELISA)、Western blotting实验和免疫荧光实验鉴定,抗Ec-FtsZ多克隆抗体效价可达1∶256 000且具有良好的抗原特异性。抗Ec-FtsZ多克隆抗体的成功制备为Ec-FtsZ生物学功能研究和生化检测奠定了实验基础。     

人早胚发育相关蛋白ZNF268的抗体制备

目的:获得纯化抗原用于制备ZNF268的多克隆抗体。方法:PCR扩增目的基因片Spacer区序列,亚克隆入融合蛋白表达载体pET28a+,构建了重组质粒pET28a+/SPA。然后将该重组质粒转化E.coliDE3(Rosseta),IPTG诱导表达,SDS-PAGE分离,获纯化融合蛋白6His-SPA。用6His-SPA免疫家兔,颈动脉取血,分离血清,从血清中获得ZNF268特异的多克隆抗体。结论:通过构建融合蛋白重组表达质粒pET28a+/SPA,用获得的初步纯化融合蛋白6His-SPA,制备了特异的ZNF268的多克隆抗体6His-SPA Ab。     

Tumor-specific idiotype vaccines. I. Generation and characterization of internal image tumor antigen

The concept of idiotype vaccines against tumor-associated antigens (TAA) was tested in the DBA/2 L1210 lymphoma subline, L1210/GZL. Monoclonal antibodies against a TAA that cross-reacts with the envelope glycoprotein gp52 of the mammary tumor virus were used to make hybridoma anti-idiotype antibodies (Ab2). In this report we describe the characterization of monoclonal anti-idiotypic antibodies against the combining site of 11C1 (Ab1), which recognizes a shared determinant of gp52 of mouse mammary tumor virus (MMTV) and the TAA of L1210/GZL. Hybridomas expressing the internal image of gp52 were screened by an idiotype inhibition assay. Mice sensitized with radiated L1210/GZL cells produced specific delayed type hypersensitivity (DTH) against the Ab2 hybridoma. Five Ab2 hybridomas were selected and were used to immunize DBA/2 mice. Such immunized animals showed specific DTH reaction against a challenge with the L1210/GZL tumor cells. Similar results were obtained in mice immunized with purified Ab2. Fluorescence-activated cell sorter analysis demonstrated that fluorescence staining of L1210/GZL cells by 11C1 can be completely inhibited with preabsorption on Ab2 hybridoma cells. Mice immunized with 2F10 and 3A4 coupled to keyhole limpet hemocyanin (KLH) contained antibodies binding to MMTV. But only in mice immunized with 2F10-KLH was significant inhibition of L1210/GZL tumor growth observed. Collectively, these results indicate that certain anti-idiotypic antibodies can mimic the MMTV gp52 antigen, as well as the gp52-like epitope expressed on the L1210/GZL tumor cells. These properties of anti-idiotypic antibodies mimicking TAA could be exploited for making idiotype vaccines against tumors.     

Interaction of glycyrol with calcineurin A studied by spectroscopic methods and docking

We have shown previously that glycyrol has an inhibitory effect on the immune response in mice by reducing calcineurin activity (Li et al., 2010, Pharm Biol 48:1177–1184). Here, we investigated the interaction of glycyrol with calcineurin A (CNA, catalytic A subunit of calcineurin) by spectroscopic methods and docking. We showed that glycyrol binds to CNA via hydrophobic interactions in a ratio of 1:1, and the main binding site is in the catalytic domain of CNA close to the calcineurin B subunit-binding domain. Binding of glycyrol changes the secondary structure of CNA, and this effect may possibly inhibit CN activity.     

卡他莫拉菌UspA1蛋白多克隆抗体的制备及鉴定

为制备抗卡他莫拉菌(Moraxella catarrhalis,Mc)表面蛋白UspA1胞外结构域的多克隆抗体(PcAb),对UspA1蛋白进行生物信息学分析,获取胞外结构域中抗原表位最为丰富的肽段,找到其对应的基因序列并引入大肠杆菌偏好性密码子,对其优化后化学合成全基因序列。将该基因序列按常规方法克隆入表达载体p ET-28a(+)后表达重组UspA1-His融合蛋白并纯化。以该纯化抗原免疫新西兰大白兔,经4次免疫后,用Protein A亲和层析柱从抗血清中纯化出抗UspA1-His融合蛋白PcAbIgG。经免疫荧光法、酶联免疫吸附法及Western blotting鉴定,抗UspA1-His融合蛋白PcAb能特异性识别UspA1蛋白的表面暴露区。该多抗的制备为下一步建立卡他莫拉菌快速检测技术奠定了基础。     

抗松材线虫纤维素酶单链抗体库的构建及筛选

构建鼠源性松材线虫纤维素酶（Bursaphelenchus xylophilus cellulase, BXC）的噬菌体单链抗体库,从中筛选特异性BXC的单链抗体。以BXC为抗原免疫BALB/C小鼠,从脾脏提取总RNA,用RT-PCR技术扩增小鼠抗体重链（V_H）和轻链(V_L)可变区基因。经重叠PCR(SOE-PCR)在体外将V_H和V_L连接成单链抗体(scFv)基因,并克隆到噬菌粒载体pCANTAB5E中,电转化至大肠杆菌TG1,经辅助噬菌体超感染,成功构建了库容为5×10⁴的Anti-BXC单链抗体库,并从该抗体库中初步筛选到了特异性识别BXC的噬菌体单链抗体scFv。将表面展示单链抗体的单克隆噬菌体转化大肠杆菌HB2151进行可溶性表达,SDS-PAGE及Western blot分析结果显示,可溶性scFv获得表达,且与BXC具有结合活性,为松材线虫的检验检疫以及病理学研究奠定了基础。     

烟草生产霍乱毒素B亚单位疫苗的免疫分析

用纯化的ＣＴＢ后腿肌肉注射免疫小鼠,每次１２．５μｇ,每隔１４天加强一次,共注射三次,末次免疫后两周收集血清,免疫小鼠诱导产生了特异性抗ＣＴＢ抗体。在ＣＨＯ细胞中,免疫小鼠血清能够中和ＣＴ的细胞病变效应;小鼠肠结扎实验表明,抗ＣＴＢ血清能够抑制ＣＴ结合细胞表面受体ＧＭ１神经节苷脂。这表明转基因烟草产ＣＴＢ在小鼠中能够产生抗细菌毒素的保护免疫力。     

白喉毒素A片段的表达纯化与单克隆抗体制备

白喉毒素 (Diphtheriatoxin ,DT)A片段 (DTA)是白喉毒素的酶活性区 ,也是DT类免疫毒素的关键结构域。DTA蛋白及其单克隆抗体在免疫毒素的毒性机理、检测与纯化研究等方面具有重要价值。通过在E .coli中表达了DTA ,经Q SepharoseFF和Ni²⁺ Sepharose两步层析纯化 ,得到纯度约为 90 %的融合蛋白。以DTA为抗原免疫BalB c小鼠 ,获得了分泌抗DTA特异单抗的杂交瘤细胞株 3B6和 3B9。单抗为IgG1亚型 ,滴度达 1∶10⁶ 以上 ,与DTA的结合可被抗DT马血清竞争抑制。抗DTA单抗用于免疫印迹试验 ,或制备成免疫亲和柱纯化基于DT的重组免疫毒素 ,均获得较好效果 ,为免疫毒素的研究奠定了良好基础     

Calcineurin B protects calcineurin A against denaturation by urea

Calcineurin (CN), a heterodimer composed of a catalytic subunit, calcineurin A (CNA) and regulatory subunit, calcineurin B (CNB), is involved in many cellular processes. We investigated the denaturation of CNA by urea in the presence or absence of CNB and found that CNB protected CNA against urea. The phosphatase activity of CNA that had been exposed to low urea concentrations (below 4 M), in the presence CNB, was higher than that of the separately urea-treated subunits mixed just prior to assay. In order to analyze the protection of CNA by CNB, we investigated the K(m) and V(max), and intrinsic fluorescence, of CNA that had been exposed to various concentrations of urea in the presence or absence of CNB. CN had an increased V(max) and decreased K(m) when exposed to 1 to 2 M urea. In addition, the kinetic parameters and intensity of intrinsic fluorescence of the AB complex and isolated subunits were quite different in 3 M urea. These results indicate that CNB not only plays an important role in regulating CNA, but also protects it against denaturation by urea.     

单克隆抗体S2C4对2型志贺毒素及其亚型毒性的中和作用

纯化的2型志贺毒素(Shiga toxin 2,Stx2)经福尔马林脱毒后免疫BALB/c小鼠制备Stx2单克隆抗体,用体外中和试验对具有中和活性的阳性抗体克隆进行初筛,对所获得的中和抗体的重、轻链同种型及结合特异性进行鉴定,其中和保护作用通过体内、体外中和试验加以验证,最后,中和抗体对Stx2亚型Stx2c和Stx2vha的中和谱用体内中和试验验证．结果显示,12株抗Stx2的阳性抗体克隆中,只有1株具有中和活性,命名为S2C4,其重、轻链同种型为G₁/κ,其靶分子为Stx2的A亚单位,与Stx2的B亚单位或Stx1不结合．在体外中和试验中S2C4可有效中和Stx2对Vero细胞的杀伤作用,同样,S2C4可中和致死量的Stx2及其亚型Stx2c和Stx2vha对小鼠的毒性作用．该抗体有望成为治疗产志贺毒素大肠杆菌感染的候选分子．     

Production of functional single-chain Fv antibodies in the cytoplasm of Escherichia coli

Production of intracellular antibodies in Escherichia coli has been thought unlikely owing to an inability to form stable disulfide bonds in the cytoplasm, a necessary step in the folding of most immunoglobulin (Ig) domains. This work investigates whether E. coli strains carrying mutations in the major intracellular disulfide bond-reduction systems (i.e. the thioredoxin and the glutathione/glutaredoxin pathways) allow the oxidation and folding of single chain variable fragment (scFv) antibodies in the cytoplasm. The effect of the co-expression of disulfide bond chaperones in these cells was also examined. An scFv that recognizes the alternative sigma factor sigma(54) was used as a model to investigate disulfide bond formation and the folding of Ig domains in E. coli. The results demonstrate that functional intrabodies, with oxidized disulfide bonds in their Ig domains, are produced efficiently in E. coli cells carrying mutations in the glutathione oxidoreductase (gor) and the thioredoxin reductase (trxB) genes and co-expressing a signal-sequence-less derivative of the disulfide-bond isomerase DsbC ((Delta)ssDsbC). We obtained evidence indicating that (Delta)ssDsbC acts as a chaperone promoting the correct folding and oxidation of scFvs.     

人源天然ScFv噬菌体抗体库的构建及鉴定

噬菌体抗体库技术是获得治疗性抗体的一条重要途径。以20份健康人外周血为样本,通过提取淋巴细胞、逆转录－PCR（RT PCR）、抗体可变区基因的扩增、重叠PCR获得单链抗体（ScFv）基因,将ScFv克隆入噬粒载体,通过近300次的电转化获得了库容量为1.3×109的全人源天然ScFv噬菌体抗体库。通过随机挑克隆测序和用5种不同抗原筛选对抗体库进行了初步验证。随机测序表明抗体库具有较好的多样性,用5种不同抗原对其进行筛选,均获得了特异性噬菌体抗体的不同富集,表明成功构建了一个多样性良好的人源天然ScFv噬菌体抗体库。     

Cancer vaccines: single-epitope anti-idiotype vaccine versus multiple-epitope antigen vaccine

In this study, we compared the immunogenicity and tumor-protective activity of anti-idiotypic antibodies mimicking a single tumor-associated epitope and tumor-associated antigen expressing multiple potentially immunogenic epitopes. We focused our study on the colorectal-carcinoma(CRC)-associated antigen GA733 (also known as CO17-1A/KS1-4/KSA/EpCAM). Monoclonal anti-idiotypic antibody (Ab2) BR3E4 was produced against murine anti-CRC mAb CO17-1A (Ab1) in rats. Full-length native GA733 protein was isolated from human tumor cells, and the extracellular domain protein (GA733-2E) was isolated from supernatants of recombinant baculovirus-infected insect cells by immunoafffinity chromatography. The immunomodulatory activity of the Ab2 was compared with that of the antigen, both in rabbits and in mice. Mice, like humans but not rabbits, express a GA733 antigen homologue on some of their normal tissues. Thus, these in vivo models allow the comparison of the immunogenicity of Ab2 and antigen in the presence (mice) and absence (rabbits) of normal tissue expression and immunological tolerance of the GA733 antigen homologue. In rabbits, aluminum-hydroxide(alum)-precipitated native GA733 antigen was superior to alum-precipitated Ab2 in inducing specific humoral immunity. In mice, alum-precipitated recombinant GA733-2E antigen, but not alum-precipitated Ab2, induced specific humoral immunity. However, when the Ab2 was administered to mice in Freund's complete adjuvant, specific humoral immune responses were elicited. Ab2 in complete Freund's adjuvant and GA733-2E in alum were compared for their capacity to induce antigen-specific cellular immunity in mice. Whereas lymphoproliferative responses were obtained with the recombinant antigen only, delayed-type hypersensitivity responses were obtained with both recombinant antigen and Ab2, although these responses were lower than after antigen immunization. The recombinant antigen in alum did not protect mice against challenge with antigen-positive syngeneic murine CRC cells. Similar studies with Ab2 BR3E4 mimicking the CO17-1A epitope were not possible because the tumor cells do not express this epitope after transfection with the human GA733-2 cDNA. However, similar studies with Ab2 mimicking the epitope defined by mAb GA733, which is expressed by the transfected tumor cells, indicated a lack of tumor-protective activity of this Ab2. In contrast, the full-length antigen expressed by recombinant adenovirus inhibited the growth of established tumors in mice. In conclusion, soluble antigen is a more potent modulator of humoral and cellular immune responses than Ab2, both administered in adjuvant. However, for induction of protective immunity, the immunogenicity of the antigen must be further enhanced, e.g., by expression of the antigen in a viral vector. Received: 27 December 1999 / Accepted: 27 January 2000     

Anti-idiotype-induced, lipopolysaccharide-specific antibody response to Pseudomonas aeruginosa

Antibody directed to the O-specific polysaccharide (Ps) side chain of Pseudomonas aeruginosa LPS provides immunotype-specific protection against infection by virtue of enhancing opsonophagocytosis. We have developed a syngeneic anti-idiotypic antibody (mAb2) directed to a functionally active monoclonal immunotype 1 Ps-antibody (mAb1). The mAb2 performed as a molecular mimic of Ps as evidenced by 1) blocking of mAb1/mAb2 interaction by Ps, 2) blocking of mAb1/Ps binding by mAb2, 3) cross-species binding of mAb2 to human Ps antibodies from individuals immunized with the same immunotype 1 Ps, and 4) induction of anti-LPS antibody by immunization with mAb2 in syngeneic mice. Our studies thus show that an anti-idiotypic antibody may functionally mimic the O-polysaccharide of P. aeruginosa LPS, and bind to cross-reactive Id present in human Ps antibodies. We have further shown that this anti-idiotypic antibody induces anti-LPS antibody when used as an Ag in syngeneic mice, suggesting that this approach may eventually be used to successfully immunize humans.     

新型抗结核蛋白亚单位疫苗Ag85A-γ干扰素的免疫效果评价

本研究旨在评价新型抗结核融合蛋白亚单位疫苗Ag85A-γ干扰素(Ag85A-IFN-γ)的免疫效果.在成功表达并纯化了去除Ag85A信号肽的融合蛋白Ag85A-IFN-γ后,将其与免疫佐剂二甲基三十六烷基铵(DDA)混合,皮下免疫C57BL/6小鼠3次,每次间隔2周,末次免疫2周后进行效果评价.采用酶联免疫吸附试验(ELISA)检测血清中IgG、IgG1和IgG2c水平.结果显示,融合蛋白Ag85A-IFN-γ组的IgG水平均高于单独抗原组,且融合蛋白组IgG2c/IgG1 比值显著高于对照组,表明融合蛋白能刺激宿主产生更强烈的体液免疫反应,更倾向于激发T辅助细胞1型(Th1型)免疫反应.流式细胞术检测特异性CD4+和CD8+ T细胞比例,发现Ag85A-IFN-γ组CD8+/CD4+最高,显示该融合蛋白能显著增强CD8+ T细胞增殖.上述结果表明,融合蛋白Ag85A-IFN-γ有望成为有效的新型抗结核融合蛋白亚单位疫苗.     

Cooperative autoinhibition and multi-level activation mechanisms of calcineurin

The Ca²⁺/calmodulin-dependent protein phosphatase calcineurin (CN), a heterodimer composed of a catalytic subunit A and an essential regulatory subunit B, plays critical functions in various cellular processes such as cardiac hypertrophy and T cell activation. It is the target of the most widely used immunosuppressants for transplantation, tacrolimus (FK506) and cyclosporin A. However, the structure of a large part of the CNA regulatory region remains to be determined, and there has been considerable debate concerning the regulation of CN activity. Here, we report the crystal structure of full-length CN (β isoform), which revealed a novel autoinhibitory segment (AIS) in addition to the well-known autoinhibitory domain (AID). The AIS nestles in a hydrophobic intersubunit groove, which overlaps the recognition site for substrates and immunosuppressant-immunophilin complexes. Indeed, disruption of this AIS interaction results in partial stimulation of CN activity. More importantly, our biochemical studies demonstrate that calmodulin does not remove AID from the active site, but only regulates the orientation of AID with respect to the catalytic core, causing incomplete activation of CN. Our findings challenge the current model for CN activation, and provide a better understanding of molecular mechanisms of CN activity regulation.     

Analysis of specificity of antibodies against synthetic fragments of different neuronal nicotinic acetylcholine receptor subunits

We have compared specificity of a panel of polyclonal antibodies against synthetic fragments of the alpha7 subunit of homooligomeric acetylcholine receptor (AChR) and some subunits of heteromeric AChRs. The antibody interaction with extracellular domain of alpha7 subunit of rat AChR (residues 7-208) produced by heterologous expression in E. coli and rat adrenal membranes was investigated by the ELISA method. For comparison, membranes from the Torpedo californica ray electric organ enriched in muscle-type AChR and polyclonal antibodies raised against the extracellular domain (residues 1-209) of the T. californica AChR alpha1 subunit were also used. Antibody specificity was also characterized by Western blot analysis using rat AChR extracellular domain alpha7 (7-208) and the membrane-bound T. californica AChR. Epitope localization was analyzed within the framework of AChR extracellular domain model based on the crystal structure of acetylcholine-binding protein available in the literature. According to this analysis, the 179-190 epitope is located on loop C, which is exposed and mobile. Use of antibodies against alpha7 (179-190) revealed the presence of alpha7 AChR in rat adrenal membranes.