Antigen binding properties of highly purified bispecific antibodies.

A panel of three bispecific monoclonal antibodies (bsMAbs) binding to follitropin (FSH) and to beta-galactosidase have been prepared by fusion of hybridoma cell lines resistant to oubain and neomycin. One of these bispecific antibodies contains heavy chains of the same IgG subclass, and two are composed of heavy chains of different IgG subclasses. We have investigated methods for the purification of bispecific antibodies from hybrid hybridoma supernatant fluids grown in serum-free medium. Following ammonium sulfate precipitation, bispecific antibodies can be purified in a single step by mixed mode ion-exchange HPLC on Bakerbond Abx columns. In one case, three species were resolved by ion-exchange HPLC and functional analysis showed that two peaks contained parental antibodies, and the third contained the bispecific. Ion-exchange HPLC purification of serum-free preparations from two other hybrid hybridomas resolved seven protein-containing peaks, only one of which was active in a bispecific ELISA. The equilibrium affinity constants for each of the parental antibodies for both FSH and beta-galactosidase were determined and found to be similar to those of the purified bsMAbs. Further, the association of FSH to one binding site on a bispecific antibody was shown to have no effect on the equilibrium binding constant for beta-galactosidase binding to the other site. Our results suggest that bsMAbs can be readily purified from hybrid hybridomas by a simple and rapid method, and the binding of antigen to one binding site on a bsMAb is independent of antigen binding to the second site.     

Flow sorting of hybrid hybridomas using the DNA stain Hoechst 33342

A two-step sorting procedure with the fluorescence-activated cell sorter (FACS) is described for the selection of hybrid hybridomas producing bispecific monoclonal antibodies. Parental hybridoma cells were first labelled before fusion with fluorescein isothiocyanate (FITC) and tetramethyl rhodamine isothiocyanate (TRITC); heterofluorescent cells were recovered after fusion. After a period of growth in culture, the cells were then stained with the DNA-specific dye bis-benzimidazole Hoechst 33342 and sorted on the basis of their DNA content. The staining conditions (10 micrograms/ml of Hoechst 33342, 90 min incubation time at 37 degrees C) were found to be optimal for obtaining a well resolved DNA histogram with minimal effect on the growth properties of cells from different mouse hybridoma lines. Employing this method we have isolated hybrid hybridomas synthesizing bispecific monoclonal antibodies reacting with human low density lipoprotein and alkaline phosphatase from calf intestine.     

Construction of a quadroma to alpha-endorphin/horseradish peroxidase using an actinomycin D-resistant mouse myeloma cell line.

A hybrid hybridoma (quadroma), secreting antibodies with double specificity to alpha-endorphin (alpha-EP) and horseradish peroxidase (HRP), has been produced. The bispecific antibodies constituted about 28-29% of all immunologically active IgG, produced by quadroma. The quadroma was isolated by fusion of two mouse hybridomas (anti-HRP and anti-alpha-EP) with distinct phenotypes: double mutant AMDR/HAT(S), and wild type (AMDS/HATR). A novel strategy for the construction of a double-mutant was applied, based on the use of an actinomycin D-resistant (AMDR) mouse myeloma for initiation of one of the parental hybridomas.     

Production and ELISA application of bispecific monoclonal antibodies against fluorescein isothiocyanate (FITC) and horseradish peroxidase (HRP)

Hybrid hybridomas producing bispecific monoclonal antibodies reacting with both horseradish peroxidase (HRP) and fluorescein isothiocyanate (FITC) were obtained by fusing two hybridoma lines and selecting the fused cells using a fluorescence activated cell sorter (FACS). FITC was used to label different monoclonal antibodies and the bispecific antibodies acted as a linking agent between FITC-labelled antibody and the marker enzyme HRP. This system was used in enzyme immunoassays for the detection of different antigens. The results suggest a wide application of bispecific anti-FITC/anti-HRP antibodies as a detection system in EIA.     

Selection of hybrid hybridomas by flow cytometry using a new combination of fluorescent vital stains.

A new combination of fluorescent dyes (rhodamine 123 and hydroethidine) was used to internally label hybridoma fusion partners. Murine hybridoma 520C9 (recognizing human c-erbB-2) was labeled with hydroethidine. Murine hybridoma 3G8 (recognizing human Fc gamma receptor III) was labeled with rhodamine 123, and verapamil was used to block rhodamine efflux via P-glycoprotein. Viability assays showed little cytotoxicity from these dyes at the concentrations used. The labeled cells were fused with polyethylene glycol, sorted for dual fluorescence on an Epics V cell sorter, and cloned. Hybrid hybridomas producing bispecific antibodies were selected for ability to promote lysis of SK-Br-3 breast cancer cells by human mononuclear cells. Several positive clones were obtained and shown to have a double content of DNA. Bispecific antibody produced by subclone 2B1 was purified by anion exchange chromatography and shown to bind both tumor cells and Fc gamma R III bearing cells. Using two parameter flow cytometric analysis, we were able to measure a 'bridging' effect of this bispecific antibody, which caused formation of complexes between PMNs and SK-Br-3 cells. Either parental antibody could compete with bispecific antibody to block such complexing. This fusion method provides several advantages over other techniques presently used (speed, convenience, low toxicity and automatic exclusion of dead cells) and can be applied to produce other hybrid hybridomas.     

Bispecific antibody-producing hybrid hybridoma and its use in one-step immunoassays for human lymphotoxin

A hybrid hybridoma cell line secreting a bispecific monoclonal antibody (MAb) was constructed by fusing horseradish peroxidase (HRPO)-immunized mouse splenocytes with previously established mouse hybridomas secreting anti-human lymphotoxin (hLT). This cell line was grown in ascitic fluid in mice to obtain large quantities of hybrid MAbs and a bispecific antibody, reacting with both HRPO and hLT, was separated from the monospecific antibody or other inactive immunoglobulin populations by hydroxylapatite chromatography. Sodium dodecylsulfate-polyacrylamide gel electrophoresis demonstrated that the bispecific antibody molecule contained two different types of heavy and light chains of both anti-HRPO and anti-hLT origin. The bispecific antibody was used to establish one-step enzyme immunoassays (EIAs) employing competitive and sandwich systems. The simple sandwich EIA was able to detect 1-100 U/ml of hLT and there was good correlation (r = 0.96) between hLT concentrations measured by the one-step EIA and a bioassay using L929 cell-lysis.     

Murine Bispecific Antibody 1A10 Directed to Human Transferrin Receptor and a 42-kDa Tumor-Associated Glycoprotein

Previously, we observed that bispecific antibodies (“antigen forks”) that bound to certain pairs of different tumor surface antigens could inhibit cell growth. The chemically linked heteroconjugate of MAb 454A12 (murine IgG1 recognizing human transferrin receptor) and 317G5 (murine IgG1 recognizing a 42-kDa tumor-associated glycoprotein) was particularly inhibitory toward human colorectal cancer cell lines, and the iron-chelating agent deferoxamine was found to augment inhibition of tumor cell growth by this antigen fork. Further experiments revealed that an antigen fork constructed by linking Fab′ fragments instead of whole antibodies retained activity, which led us to construct a fork-secreting hybrid hybridoma. Hybridoma 454A12 was fused with hybridoma 34F2 (murine IgG1 with the same specificity as 317G5). Hybrid hybridomas whose supernatants blocked binding of both 454A12 and 34F2 probes were further tested for the ability to block growth of SW948 human colorectal cancer cells in an MTT growth assay, and were chosen for subcloning. Ascites produced by clone 1A10 was purified by affinity and cation exchange chromatography. Purified 1A10 bispecific antibody showed growth inhibitory activity comparable to that of a chemically linked heteroconjugate of its parental antibodies 34F2 and 454A12. Adding deferoxamine greatly enhanced the inhibitory activity of 1A10 and effectively prevented regrowth of tumor cellsin vitro.By heterologously crosslinking two antigens that are coexpressed on many tumor cells, this bispecific antibody is able to inhibit tumor growth with enhanced selectivity.     

抗HBsAg和抗红细胞双特异Diabody的构建及表达

目的构建及表达抗乙肝病毒表面抗原（ＨＢｓＡｇ）和抗红细胞（ＲＢＣ）双特异Ｄｉａｂｏｄｙ，用于血清中ＨＢｓＡｇ的快速检测。方法将抗ＨＢｓＡｇ的人抗体轻重链可变区基因与抗红细胞的鼠抗体重轻链可变区基因交叉配对构建成两个杂合Ｄｉａｂｏｄｙ基因，并将两个配对基因组建在一个表达载体中，成为双特异Ｄｉａｂｏｄｙ表达载体，并在大肠杆菌中分泌表达。结果经ＥＬＩＳＡ检测和红细胞凝集实验测定，证明所表达的双特异性Ｄｉａｂｏｄｙ具有抗ＨＢｓＡｇ和抗ＲＢＣ双重功能，并可使含有ＨＢｓＡｇ的ＲＢＣ悬液产生血球凝集。结论所表达的双特异性Ｄｉａｂｏｄｙ具有双重抗体活性，可用于血清中ＨＢｓＡｇ的快速检测     

A simple metabolic system for selection of hybrid hybridomas (tetradomas) producing bispecific monoclonal antibodies

A metabolic selective system has been proposed for the selection of hybrid hybridomas (tetradomas) based on the introduction in one of the parental cell lines of two traits simultaneously--a recessive one (resistance to 8-azaguanine) and a dominant one (multidrug resistance). Tetradomas were selected in the presence of two selective agents: aminopterin and actinomycin D. Using this approach we produced tetradomas secreting bispecific MAbs to horseradish peroxidase and human alpha-fetoprotein.     

Use of bispecific hybrid antibodies for the development of a homogeneous enzyme immunoassay

Hybrid bispecific monoclonal antibodies reacting with carcinoembryonal antigen (CEA) and with the E. coli enzyme beta-galactosidase (GZ) were produced by fusion of hybridomas or chemical linkage of half-antibodies. Since the original anti-GZ antibody used in these experiments was capable of protecting GZ from thermal denaturation, it was possible, by hybridizing it with two different non-competitive anti-CEA antibodies, to design a homogeneous enzyme immunoassay for quantitation of CEA. In fact, a mathematical analysis of the reaction indicates that, under appropriate concentrations of the reactants, circular complexes can be formed which contain the two hybrid antibodies, the GZ enzyme and the CEA antigen. The stability of these complexes can be expected to be substantially greater than that of the more labile CEA-free GZ-antibody complexes, prompting a significant increase in the amount of enzyme molecules which are bound to antibody and are consequently protected from thermal denaturation. These expectations were supported by experimental results: under appropriate conditions, heat-resistant enzyme activity was indeed proportional to concentration of CEA in the range up to 75 ng/ml. As predicted by theory, however, in the presence of excess CEA - in fact at CEA concentrations which are higher than those of possible clinical relevance - circular complexes tended to open up, leading to a marked prozone effect.     

Allo-class I-reactive CD4-CD8- T cell hybridomas recognize the conformational change of class I molecule resulting from the exchange of the alpha 3 domain

H-2Kb-reactive, interleukin (IL) 2-producing T cell hybridomas possessing neither CD8 nor CD4 molecules were employed for the study of allorecognition on interspecies hybrid antigens by T cells in the absence of an influence of these accessory molecules. Both HTB176.10 and HTB177.2 T cell hybridomas reacted with KbKbB7 hybrid antigens as well as Kb antigens and they produced more IL2 in response to Kb antigens than KbKbB7 hybrid antigens. IL2 production of these T cell hybridomas was dependent on the surface expression level of Kb molecules on stimulators. Therefore, L cells expressing almost equivalent levels of Kb or hybrid antigens were selected for further functional studies by these T cell hybridomas. They apparently produced less IL2 in response not only to interspecies hybrid antigens but also to interspecies hybrid antigens in response to Kb antigens. These results indicated that T cell hybridomas recognized the conformational change of class I molecule resulting from the exchange of the alpha 3 domain via their T cell receptors.     

Establishment and characterization of permanent murine hybridomas secreting monoclonal anti-thy-1 antibodies

hybridomas secreting anti-Thy-1 antibodies were produced by fusing cells of the mouse myeloma line P3-NSI/1-Ag4-1 (NS-1) with spleen cells from AKR/J mice immunized with C3H/Di thymus cells and by subsequent growth in tissue culture and selection of the hybrid cells. Two permanent hybridomas, 1B5 and 1aG4/C5, secreting antibodies of IgG3 subclass were isolated by repeated cloning of cells by dilution and in soft agar. Growth of the hybrid cell colonies depended on the presence of feeder cells; spleen cells at 1-2 x 10(6)/ml were most effective, then thymus cells at 1-4 x 10(6)/ml and peritoneal cells at a concentration 1-2 orders of magnitude lower. The two hybridomas were grown in vitro or vivo and their products were further analysed. In tissue culture in serum-free medium under the optimum conditions the supernatant from hybridoma 1B5 contained 0.07 mg/ml of antibodies and that from hybridoma IaG4/C5 had 0.26 mg/ml of antibodies, whereas ascites 1B5 contained 3.6 mg/ml and ascites 1aG4/C5 4.4 mg/ml of antibodies. A very low electrophoretic mobility of both antibodies facilitated their isolation. The specificity of the antibodies was tested in the cytotoxicity assay in the presence of complement and by the binding of isotopically labelled antibodies to thymus cells from A/Ph mice and other Thy-1.2+ strains and A.Thy-1.1 and AKR/J mie. Antibodies of clone 1aG4/C5 were specific for Thy-1.2+ cells, whereas antibodies of clone 1B5 at higher concentrations also reacted with Thy-1.1+ cells from the thymus and lymph nodes. Both antibodies killed more than 95% thymus cells and 60-70% lymph node cells in the cytotoxicity assay. The specificity of antibodies for T lymphocytes was confirmed in the functional test in which the antibodies eliminated the response of spleen cells to Concanavalin A but did not affect the response to lipopolysaccharide in the presence of complement.     

A novel technique for the production of hybrid antibodies

Chemically linked bifunctional antibodies (heteroconjugates) composed of one antibody specific for the TcR/CD3 complex on cytotoxic T cells and another specific for viral antigens expressed on the surface of infected cells have been shown to redirect CTL to lyse virus-infected cells. Hybrid antibodies are bifunctional antibodies produced by the fusion of two hybridomas. As a result of their native dimeric immunoglobulin structure, hybrid antibodies may be more effective than heteroconjugates in vivo. We have developed a unique method for production of hybrid antibodies by infecting each hybridoma with a different retrovirus vector which confers resistance to either G418 or methotrexate. The hybridomas are fused and selected in medium containing both inhibitors. Using this technique, we have produced hybrid antibodies made up of one antibody combining site which binds to the TcR and a second specific for the hemagglutinin of X-31 influenza virus. We show that this hybrid antibody effectively mediates the lysis of virus-infected cells in the presence of appropriate CTL. Thus hybrid antibodies as well as heteroconjugates can redirect CTL to lyse virus-infected targets.     

Anti-human CD138 monoclonal antibodies and their bispecific formats: generation and characterization

Syndecan-1 (CD138), a heparan sulfate proteoglycan, acts as a co-receptor for growth factors and chemokines and is a molecular marker associated with the epithelial–mesenchymal transition during development and carcinogenesis. In this study, we generated two specific mouse anti-human CD138 monoclonal antibodies (mAbs, clone ID: 480CT5.4.3, 587CT7.3.6.5) using hybridoma technology and identified their immunological characteristics. After hybridoma sequencing, the single-chain variable fragments (ScFvs) cloned from two hybridoma cells were combined with anti-CD3 OKT-3 ScFv to generate two recombinant bispecific antibodies (h-STL002, m-STL002) against CD138 and CD3 molecules, respectively. The bispecific antibodies were able to specifically target CD138?+?multiple myeloma (MM) cells and CD3?+?T cells, and showed the potent cytotoxicity against MM RPMI-8226 cell line through T cell activation. However, these bispecific antibodies without T cells did not cause toxic side effect on MM cells. Overall, the two hybridoma clones and their bispecific formats have great potential to promote diagnosis and immunotherapy of plasma cell malignancy.     

One-step method for establishing 8-azaguanine-resistant hybridomas suitable for the preparation of triomas.

A simple and rapid one-step method for establishing azaguanine resistant (Agr) hybridomas, which can be used as a fusion partner for the construction of triomas (hybridoma x splenocyte), has been developed. The method relies on cloning the hybridoma cells in soft agar supplemented with 20 micrograms/ml 8-azaguanine. The drug-resistant subclones were isolated after 3-5 days, in comparison with 4-5 weeks reported for the conventional adaptation method. The high frequency (about 10(-3) of Agr-mutants achieved by the cloning method was demonstrated with five different hybridoma clones. One of the derived Agr-hybridomas was fused with mouse immune spleen cells in order to demonstrate its suitability for the generation of triomas secreting bispecific monoclonal antibodies.     

In Vitro Immunization for the Production of Antigen-Specific Lymphocyte Hybridomas

Antigen-specific lymphocyte hybridomas have been produced by a simple in vitro immunization procedure. Non-immune spleen cells have been activated in vitro, and the B-cell blasts have subsequently been used for somatic cell hybridization. Hybrids secreting monoclonal antibodies to human myoglobin, pig insulin, and benzo(a)pyrene were obtained with splenocytes that had been immunized 5 days in culture before the hybridization. The frequency of specific hybridomas was the same as or higher than that of hybridomas produced from in vivo-immunized cells, showing the versatility of the procedure when making monoclonal antibodies to haptens and proteins with a conserved structure or to small amounts of antigen. Monoclonal antibodies of both IgG and IgM isotypes could be isolated.     

A single-step procedure for cloning and selection of antibody-secreting hybridomas

A procedure is described which permits high-yield direct cloning of newly established hybridomas on STO fibroblast feeders in soft agarose. Several thousand independent clones are typically obtained from each fusion (1 X 10(8) spleen cells). These are screened using a colony replica assay in which secreted antibodies diffuse through an agar overlay and bind to antigen immobilised on nitrocellulose. Bound antibodies are then detected with enzyme-labelled second antibody. The procedure is fast and efficient and permits the isolation and selection of antigen-specific clones in less than 2 weeks from fusion. It has been successfully employed for the derivation and selection of high-affinity anti-hapten antibodies. Other potential applications of the assay are in the detection of non-immobilised antigens by an indirect method using anti-globulin on nitrocellulose, in the generation of bispecific antibodies and the selection and characterisation of antibody specificities generated by the expression of antibody fragments in bacteria or yeasts.     

Bispecific Antibodies for Cancer Immunotherapy

The concept of using bispecific antibodies to retarget immune effector cells for cancer therapy was conceived more than 20 years ago. However, initial clinical studies were rather disappointing mainly due to low efficacy, severe adverse effects and immunogenicity of the bispecific antibodies. A deeper understanding of effector cell biology and especially developments in the field of antibody engineering has led to the generation of new classes of bispecific antibodies capable of circumventing many of these obstacles. Furthermore, new applications were established for bispecific antibodies, such as pre-targeting strategies in radioimmunotherapy or dual targeting approaches in order to improve binding, selectivity, and efficacy. This review summarizes recent progress in the development of bispecific antibodies and describes some new concepts developed for cancer immunotherapy.     

Hybridoma cloning by the end-point dilution method

Hybridomas producing monoclonal antibodies to tick-borne encephalitis, Venezuelan equine encephalomyelitis, and vaccinia viruses were cloned and recloned by the end-point dilution method in 96-well Linbro plates on a cell feeder layer. With decreasing of the cell seed dose the average number of clones per well decreased and the effectiveness of clone production increased. When an average of one cell per well was introduced, the portion of vells with single clones for hybridomas of various origins ranged from 5.4% to 37.5%. As a rule, the first cloning resulted in a significant rise in titres of monospecific immunoglobulins secreted by hybridomas and improved growth characteristics of the hybrid cell population. Repeated cloning required in most cases for stability of the hybrid line was usually not accompanied by changes in the productivity of the cell cultures.     

Use of bispecific antibodies in molecular velcro assays whose specificity approaches the theoretical limit of immunodetection for Bordetella pertussis

A bispecific monoclonal antibody (bsMAb) that detects Bordetella pertussis, the causative agent of whooping cough, and horseradish peroxidase (HRPO) has been developed by use of the quadroma technology. A quadroma, P123, was produced by fusing two well-characterized hybridomas against the bacterium and the enzyme and was subcloned to obtain a stable bsMAb-secreting cell line. The quadroma was theoretically expected to produce up to 10 different molecular species of immunoglobulins, so secreted bispecific antibody was complexed with excess HRPO and the HRPO-bsMAb complex was purified in one step by benzhydroxamic acid-agarose affinity cochromatography. An ultrasensitive homosandwich molecular "velcro" enzyme-linked immunosorbent assay for the detection of B. pertussis whole bacteria with HRPO-bsMAb was established in both microplate and nasopharyngeal swab formats. This assay demonstrates a high sensitivity that approaches the theoretical limit of detection of one bacterium. This new nanoprobe can be used to develop a new generation of assays that are simple, inexpensive alternatives to quantitative PCR and that can be used by clinical laboratories. This strategy of homosandwich assays with solid-phase monospecific antibodies and solution-phase bsMAb with specificity for the same repeating surface determinants can be applied to generate ultrasensitive immunodiagnostic assays for viruses and bacteria.