Efficient generation of monoclonal antibodies for specific protein domains using recombinant immunoglobulin fusion proteins: pitfalls and solutions

Monoclonal antibody production (mAb) first requires the availability of large amounts of pure immunogen for animal immunisation and fusion screening procedures. To overcome this obstacle, we have developed a simple method for rapid generation of pure antigen by generation of recombinant protein containing the antigen of interest fused to the hinge and Fc domains of human immunoglobulin (Ig). The Fc domain forms a convenient 'tag' to enable detection of the protein in supernatant of transfected cells and for purification of immunogen by protein A affinity chromatography. The only requirement for immunogen preparation using this methodology is that a DNA sequence encoding a portion of the molecule of interest is known and that a suitable PCR template is available. Antibody production can be tailored to specific protein domains, for example functional domains, by expressing solely those domains in the fusion protein. We illustrate the technique with two different fusions used to raise antibodies against the porcine and human analogues of a complement (C) regulatory protein, decay accelerating factor (DAF) (CD55). Use of the specific Ig-fusion protein and a control protein facilitated screening of fusions by ELISA. We demonstrate two expression systems used to generate Ig fusion proteins, the first utilised a commercial vector to incorporate an amino terminal leader sequence and carboxy terminal Ig domains. Low levels of expression required subcloning into a high expression vector and resulted in yields of fusion protein at between 2 and 10 mg per litre of supernatant. The second expression system utilised the high expression vector directly, Ig domains of the chosen immunoglobulin isotype were amplified from peripheral blood mononuclear cell (PBMC) RNA and ligated into the vector in frame with DNA encoding the antigen. We describe potential pitfalls that may be encountered while using Ig fusion proteins as immunogen and demonstrate ways in which to tailor their design for optimal mAb production.     

A general approach to the generation of monoclonal antibodies against members of the tetraspanin superfamily using recombinant GST fusion proteins.

Tetraspanins belong to a rapidly growing family of proteins characterized by the presence of four conserved transmembrane segments and are involved in such diverse functions as cellular activation, adhesion, migration and differentiation. In an effort to develop reagents against newly discovered tetraspanins, we have devised a simple method for the screening of monoclonal antibodies (mAbs) using recombinant GST fusion proteins. GST fusion proteins containing the second extracellular domain of different tetraspanins (CD9, CD63, CD53, CD81, A15 or CO-029) were produced separately. Mice were immunized with cells having a high expression of the chosen tetraspanin and the constructs were used to screen hybridomas in a solid phase ELISA. Several clones binding the fusion protein were identified for each construct tested: four anti-CD9 hybridoma clones, four anti-CD63, two anti-CD53, two anti-CD81, three anti-A15 and one anti-CO-029. All the newly developed mAbs recognized the native proteins by flow cytometry, immunofluorescence staining of cells and immunoprecipitation and bound to the denatured proteins on immunoblotting. Use of GST fusion protein constructs in a simple ELISA can facilitate screening for mAbs to members of the tetraspanin family, especially in cases where information is limited to the nucleotide sequence. The mAbs obtained by this strategy should prove to be valuable tools for functional studies of newly discovered tetraspanins.     

Use of recombinant fusion proteins and monoclonal antibodies to define linear and discontinuous antigenic sites on the dengue virus envelope glycoprotein.

Sixteen overlapping fragments of the dengue-2 virus envelope (E) protein, expressed as trpE-E fusion products in Escherichia coli, were used to map the epitopes defined by a panel of 20 monoclonal antibodies (MAbs) by immunoblotting. Using this technique, the amino acid sequence of six antigenic domains on the E protein was characterized. Nonneutralizing MAbs were found to define either linear-specific, subcomplex-specific (amino acids 22-58), and complex-specific (amino acids 304-332) epitopes or a subcomplex conformational-dependent epitope requiring the presence of two closely linked amino acid sequences from the E protein, 60-97 and 298-397. Neutralizing MAbs, however, defined either group-reactive epitopes present on two overlapping domains (amino acids 60-135; amino acids 60-205) or type-, subcomplex-, complex-, subgroup-, and group-specific determinants (amino acids 298-397). These neutralizing epitopes were all found to be dependent upon disulfide bridges. Our results suggest that the maintenance of a topographical arrangement of discontinuous antigenic domains in the flavivirus E-protein is necessary to induce neutralizing and protective antibodies.     

Second generation monoclonal antibodies to the human integrin alpha 6 beta 4

Second generation monoclonal antibodies to the alpha 6 beta 4 subunits of human integrins have been prepared. MAbs 450-9D, 10D, and 11A1 react at different sites on the beta 4 molecule and MAbs 450-30A1 and 33D react at the same site on the alpha 6 subunit. Double determinant (two-site) radioimmunoassays using combinations of these MAbs have been developed. Two assays for beta 4 distinguish between the whole beta 4 molecule and the beta 4 molecule truncated from the C-terminus (form c) while another assay measures the presence of alpha 6 subunits. Data from the two-site assays support the following conclusions: (1) Colon tumors and normal colon mucosa express large amounts of alpha 6 beta 4 although only form c of the beta 4 was detected; (2) There is no evidence for alpha 6 beta 1 expression in colon; however, some of this complex may be present in certain lung tumors. The extracellular domains of alpha 6 and beta 4 can associate with each other even if the cytoplasmic domain of the beta 4 subunit is not present. MAbs to specific domains of the beta 4 molecule may be useful in analyses of forms a and c in normal and malignant tissue. The fact that only the largest beta 4 molecule "a" retains the phosphorylation site may have functional significance.     

Use of monoclonal antibodies for discrimination between natural and recombinant human interferon-tau.

Different monoclonal antibodies (MAbs) were raised against denaturated and native recombinant human Interferon-tau (IFN-tau). This approach gave us MAbs which recognized either N-term (prepared with SDS-denaturated IFN-tau) or C-terminal part of the antigen as well as MAbs which linked to non linear epitopes (obtained with native form of IFN-tau). Some of them inhibited or enhanced their respective binding to IFN-tau. After characterization, these antibodies were used as probes and some were selected to prepare two quantitative sensitive sandwich IRMAs able to discriminate between recombinant and natural IFN-tau.     

抗rhNDPK-A单克隆抗体的制备及鉴定

目的 :研制抗rhNDPK A (recombinanthumannucleosidediphosphatekinase A)单克隆抗体 (mAb) ,并鉴定其特性。 方法 :以纯化的rhNDPK A免疫BALB/c小鼠 ,采用杂交瘤技术制备抗rhNDPK AmAb ;用免疫双扩散鉴定Ig亚类 ;West ernblot鉴定mAb的特异性 ;间接ELISA检测mAb的腹水效价、亲和常数 ,并进行表位分析。结果 :获得 6株可分泌特异性mAb的抗rhNDPK A的杂交瘤细胞系 2D9、8C7、13E2、15D9、15E3和 2 0D9,Ig亚类均为IgG1;其效价为 1× 10 -4～5× 10 -6;亲和常数为 4 .5× 10 -9～ 2 .8× 10 -10 mol/L ;共有3个抗原表位。结论 :获得抗rhNDPK A的mAb ,为进一步用于临床诊断和实验研究创造了条件     

Isolation of a monoclonal antibody to the TrpE protein and its use for the purification of recombinant fusion proteins.

The trpE (or anthranilate synthetase) gene product has been used extensively as a fusion protein for the expression of a myriad of biologically active proteins. A trpE construct can be produced in high yield, is relatively resistant to proteolysis, and separates from the bulk of E. coli proteins because of its insolubility. We have isolated and characterized a monoclonal antibody against the TrpE protein for use as a detection and immunoaffinity reagent. The MAb, TRP 7.4, is highly specific for the TrpE protein and has a relative affinity of 1.0 ng. The antibody can also be used to detect TrpE constructs on Western blots. In addition, TRP 7.4 has been used to purify a TrpE-IL-6 fusion protein. These studies show the utility of this MAb as a tool for both research and protein purification.     

抗人乳腺癌候选抑制蛋白1单克隆抗体的制备及鉴定

目的:制备抗人乳腺癌候选抑制蛋白1(BCSC-1)蛋白单克隆抗体(mAb),并对其特异性进行鉴定。方法:构建原核表达载体pET-30a-BCSC-1,在原核表达系统E.coliBL21(DE3)中表达重组人BCSC-1蛋白。超声洗涤纯化重组蛋白作为抗原免疫BALB/c小鼠,取免疫小鼠的脾细胞和同系小鼠的骨髓瘤细胞Sp2/0进行常规融合,通过有限稀释法进行克隆和间接ELISA筛选,获得分泌小鼠抗人BCSC-1蛋白mAb的杂交瘤细胞株,通过ELISA、Western blot等方法检测其特异性。将真核重组表达载体pcDNA3.1/v5-HisB-BCSC-1转染入乳腺癌MCF-7细胞,通过免疫组化确定了人BCSC-1蛋白的表达。结果:成功构建了原核表达载体pET-30a-BCSC-1,经IPTG诱导表达出了重组人BCSC-1蛋白,主要以包涵体的形式存在沉淀中。用纯化的重组BCSC-1蛋白免疫小鼠后经融合筛选得到1株稳定分泌抗BCSC-1的mAb杂交瘤细胞株。通过ELISA、Western blot、免疫组化等方法鉴定,抗BC-SC-1的mAb能与BCSC-1蛋白特异性结合。结论:成功制备了小鼠抗人BCSC-1的mAb。     

An antibody to beta amyloid and the amyloid precursor protein inhibits cell-substratum adhesion in many mammalian cell types.

An epitope-specific antibody directed against the first 16 amino acids of the beta amyloid protein (anti-BP16) immunoprecipitated the secreted form of the amyloid precursor protein (APP) from the conditioned medium of PC12 cells. This antibody caused neurite retraction in differentiated PC12 cells and inhibited cell-substratum adhesion in many neuronal and non-neuronal cell types. The inhibitory effect of anti-BP16 was abolished by preabsorption of the antibody with BP16 peptide. Antibodies directed against other domains of APP did not inhibit cell adhesion. The secreted form of APP may be important for cell adhesion in many different mammalian cell types.     

抗Ig融合蛋白Fc段单克隆抗体的制备、鉴定与应用研究

目的：制备并鉴定抗Ig融合蛋白Fc段的单克隆抗体(mAb)，建立用于检测Ig融合蛋白的夹心ELISA法和纯化Fc融合蛋白的亲和层析法。方法：以hBCMA—Ig融合蛋白为抗原免疫BALB／c小鼠，通过细胞融合制备抗Fc段mAb，用ELISA等方法鉴定mAb的Ig亚类、表位以及种属特异性，建立用于检测Ig融合蛋白的夹心ELISA法;Western blot检测mAb对变性Ig融合蛋白的反应性。将mAb与Sepharose4B交联，制备亲和层析柱，对LAIR1-Ig融合蛋白进行纯化。结果：获得7株稳定分泌抗Fc段mAb的杂交瘤(FMUFcl-FMUFc7)。利用FMUFc4作为包被mAb，FMUFc5作为酶标记mAb，成功地建立了检测Ig融合蛋白的ELISA法，敏感度达到2μg／L；在7株mAb中，FMUFc6可用于Ig融合蛋白的western blot检测。用FMUFc 6mAb制备的亲和层析柱，可有效地纯化LAIRl—Ig融合蛋白。结论：成功地制备了抗Ig融合蛋白Fc段的mAb，建立了可用于Ig融合蛋白检测和纯化的方法，为Ig融合蛋白的应用提供了有力手段。     

Cerebral microvascular amyloid beta protein deposition induces vascular degeneration and neuroinflammation in transgenic mice expressing human vasculotropic mutant amyloid beta precursor protein

Cerebral vascular amyloid beta-protein (Abeta) deposition, also known as cerebral amyloid angiopathy, is a common pathological feature of Alzheimer's disease. Additionally, several familial forms of cerebral amyloid angiopathy exist including the Dutch (E22Q) and Iowa (D23N) mutations of Abeta. Increasing evidence has associated cerebral microvascular amyloid deposition with neuroinflammation and dementia in these disorders. We recently established a transgenic mouse model (Tg-SwDI) that expresses human vasculotropic Dutch/Iowa mutant amyloid beta-protein precursor in brain. Tg-SwDI mice were shown to develop early-onset deposition of Abeta exhibiting high association with cerebral microvessels. Here we present quantitative temporal analysis showing robust and progressive accumulation of cerebral microvascular fibrillar Abeta accompanied by decreased cerebral vascular densities, the presence of apoptotic cerebral vascular cells, and cerebral vascular cell loss in Tg-SwDI mice. Abundant neuroinflammatory reactive astrocytes and activated microglia strongly associated with the cerebral microvascular fibrillar Abeta deposits. In addition, Tg-SwDI mouse brain exhibited elevated levels of the inflammatory cytokines interleukin-1beta and -6. Together, these studies identify the Tg-SwDI mouse as a unique model to investigate selective accumulation of cerebral microvascular amyloid and the associated neuroinflammation.     

Monoclonal hybridoma antibodies to human amyloid related protein SAA.

Problems concerning isolation and characterization of the amyloid related serum protein SAA in a pure form prompted us to make monoclonal antibodies to the protein. Protein SAA isolated by gel filtration under dissociating conditions was used for immunization of BALB/c mice, and spleen cells from a mouse producing high titred antiserum to SAA were fused with cells from the mouse plasmacytoma line P3U1. Antibody specificity to various preparations of protein SAA was tested using an indirect enzyme-linked immunosorbent assay. Monoclonal antibodies with specificity for SAA were obtained in addition to antibodies which reacted with both SAA and the related amyloid protein AA. Antibodies specific for one of the apoC proteins of the lipoprotein fraction were also produced showing that the SAA preparation used for immunization was contaminated with apoC proteins.     

Generation of monoclonal antibodies to human lymphocyte cell surface antigens using insect cells expressing recombinant proteins.

We have expressed human CD40 and human B7 in insect cells using the baculovirus expression system and have used these insect cells to immunize mice for the generation of monoclonal antibodies. We demonstrate here that specific monoclonal antibodies to human CD40 and human B7 were obtained using this approach. One significant advantage of this method is that immunizing mice with insect cells did not evoke an immune response to human cells and, therefore, EBV-transformed human B cells could be used to screen for specific antibody production by the hybridoma clones.     

Intracellular domain generation of amyloid precursor protein by epsilon-cleavage depends on C-terminal fragment by alpha-secretase cleavage

A significant accumulation of Abeta is major pathological feature in the brain in patients with Alzheimer's disease (AD). Amyloid precursor protein (APP) is cleaved by alpha- and beta-secretase, resulting in secretion of extracellular domain. Then the remaining membrane-anchored C-terminal fragments (CTFalpha or CTFbeta) are cleaved by gamma-secretase. Therefore, Abeta is derived from APP by sequential proteolytic processing involving 2 proteases, called beta- and gamma-secretase. Gamma-secretase cleavage results in the generation of the APP intracellular domain (AICD), as well as Abeta. Recently, AICD is generated by epsilon-cleavage site near the cytoplasmic membrane boundary of APP, not by gamma-cleavage site in the middle of transmembrane domain. We show that elevated beta-secretase levels induced the increase in CTFbeta and Abeta generation and reduction of CTFalpha and AICD generation in vitro. Furthermore, elevated alpha-secretase levels induced an increase of AICD. The results suggest that generation of AICD by epsilon-cleavage depends on CTFalpha and that gamma- and epsilon-cleavage are differentially regulated.     

One-step immunoaffinity purification of bioactive human recombinant IL-1 beta with a monoclonal antibody directed to a well-exposed domain of the protein

A monoclonal antibody (mAb) specific for human recombinant IL-1 beta (hu rIL-1 beta) was produced by immunizing BALB/c mice with hu rIL-1 beta purified with classical methods. This mAb recognizes an epitope within the highly hydrophylic fragment spanning amino acid 133-147. The affinity constant of this mAb towards IL-1 beta was determined by RIA. An affinity column was prepared by covalent binding of the mAb to Sepharose CL-4B. The column was capable of selectively binding hu rIL-1 beta produced in Escherichia coli directly from crude homogenates. The IL-1 beta protein yield was higher than 90% with a very good recovery of IL-1 beta biological activity. Moreover, the immunosorbent retained at least two thirds of its IL-1 beta-binding capacity after 20 cycles of purification.     

Use of monoclonal antibodies in human transplantation.

Monoclonal antibodies are of growing importance in human organ transplantation in the prophylatic and curative treatment of cellular rejection. Among the pan T-lymphocyte monoclonal antibodies, OKT3 has been much studied, although clinical research is engaged with more selective targets of allorecognition and/or their consequences, for example monoclonal antibodies directed against the interleukin-2 receptor, adhesion molecules and CD4 molecules. We summarize the use of these monoclonal antibodies and bioreagents in clinical transplantation.     

抗人尿激酶单克隆抗体制备和鉴定

用人高分子量尿激酶(HMW-UK)为抗原,通过杂交瘤技术获得了两株阳性杂交瘤细胞(2B8、3A2)。采用葡萄球菌 A 蛋白(SPA)亲和层析或 Water's650快速蛋白分离系统纯化抗 UK 单克隆抗体(McAb).3A2McAb 为 IgG 1亚类,特异地识别 HMW-UK 和低分子量 LMW-UK,抑制 UK 活性,表明3A2McAb 所作用的位点为 UK 的 B 链,即活性中心。EIA 测定3A2McAb 与 UK 的亲和常数为8.43×10~8M~(-1)。2B_8McAb 亦为IgG_(?)亚类,特异地识别 HMW-UK 及其氨基端1～135氨基酸片段(ATF),不抑制活性,EIA 测定2B_8McAb 与UK 的亲和常数为2.8×10~9M~(-1)。2B_8McAb 可用于导向溶栓的研究以及 UK 与其受体间反应的研究。     

慢性髓细胞自血病BCR-ABL 融合基因片段的克隆表达及其单克隆抗体的制备

目的 制备针对慢性髓细胞白血病(CML)bcr-abl融合蛋白的单克隆抗体(mAb).方法 采用PCR方法扩增包含BCR-ABL(b3a2)融合位点周围约450bp的基因片段,将其定向克隆到pQE-31载体内,转化大肠杆菌M15菌株,诱导表达6×His标签的融合蛋白p18bcr-ab1并对其进行纯化,用纯化后的蛋白免疫Balb/c小鼠,采用常规的细胞融合技术制备针对bcr-abl蛋白的mAB并对其特性进行鉴定.结果 获得了6株分泌抗bcr-abl融合蛋白mAB的杂交瘤细胞株,所分泌的mAbs均特异性识别.bcr-cbl蛋白abl端.结论 本研究中所表达的融合蛋白p18bcr-abl及其mAb的获得为慢性髓细胞白血病的研究提了有效的工具.     

Production and characterization of two monoclonal antibodies to human glutathione peroxidase.

Glutathione peroxidase (GSH-Px) is an important selenium-containing enzyme which protects cells from oxidative damage. Two hybridoma clones (GPX-121 and GPX-347), producing mouse IgG1 monoclonal antibodies specific for GSH-Px, were established. Immunoblot analysis revealed that GPX-347 was specific for human GSH-Px, while GPX-121 cross-reacted with human, rat, mouse and rabbit GSH-Px. Correlation between GSH-Px content and its enzymatic activity was investigated in erythrocytes of 76 humans and in human lung adenocarcinoma PC-9 cells by using a sandwich type ELISA. The results indicated that GSH-Px activity was expressed higher than expected from GSH-Px content especially in the range of low GSH-Px concentration. PC-9 cells selenium depleted medium did not stain but the cytoplasm of PC-9 cells grown in medium supplemented with selenium stained strongly.