Molecular integrity of monoclonal antibodies produced by hybridoma cells in batch culture and in continuous-flow culture with integrated product recovery

The molecular integrity of monoclonal antibodies (MCAB) produced by murine hybridoma cell line TB/C3 was studied in batch and continuous-flow cultures. In batch culture, one band of MCAB was detected initially by Western blotting of sodium dodecyl sulfate (SDS)-polyacrylamide gels run under unreduced conditions, but heterogenous MCAB bands appeared as the culture aged. The latter were due to the degradation of MCAB by proteases active at the neutral pH of the culture. The deleterious effect of proteases was minimized in the continuous-flow cultures which were integrated for product recovery. The MCAB of high quality was purified over 26 days from a culture grown at a dilution rate of 0.025 h(-1) (experiment 1). However, at a lower dilution rate of 0.015 h(-1) (experiment 2), the integrity of MCAB was compromised after the initial 13 days of culture. This was shown to be due to the variation in the carbohydrate content of MCAB produced, as judged by the increased sialylation of heavy chains and the varied reactivity of MCAB with lectins (Maackia amurensis agglutinin, Galanthus nivalis agglutinin, and Datura stramonium agglutinin) as the age of the culture increased. The concentration of the purified MCAB samples by enzyme-linked immunosorbent assay (ELISA) (used normally) was usually higher than that estimated by absorbance at 280 nm. Best correlation between the two methods (ELISA-280 nm ratio of 1.02-1.25) was obtained with experiment 1 samples. This ratio increased in experiment 2 and batch culture samples as the heterogeneity of MCAB produced increased, being 1.03-2.94 and 2.53-4.62, respectively. Therefore, ELISA overestimated MCAB concentration when the molecular integrity of the latter was compromised. The ELISA-A(280) nm ratio might hence provide a useful indicator for assessing the quality of MCAB produced. Comparison of SDS-polyacrylamide gels stained with Coomassie Brilliant Blue R and silver showed that the former correlated better with the MCAB activity stain, whereas the silver stained both the protein- and carbohydrate-rich components. Comparison of the patterns produced with these two stains might therefore offer another parameter to monitor the overall integrity of MCAB produced. Finally, the data presented have important implications on the validity of using long-term and intensive cultures for generating MCAB because such cultures would be subjected to the additive effects reported for batch and continuous modes of growth. (c) 1993 John Wiley & Sons, Inc.     

杂交瘤细胞体外大规模培养研究进展

单克隆抗体在生物学和医学研究领域中显示了极大的应用价值,是免疫检验中的新型试剂,是生物治疗的导向武器。作为医学检验试剂,单克隆抗体可以充分发挥其优势,如特异性好,灵敏度高,更便于质量控制,利于标准化和规范化。传统的方法是利用小鼠腹水制备单克隆抗体,但是近几十年杂交瘤细胞体外大规模培养制备单克隆抗体技术也在不断发展。特别是单克隆抗体在疾病诊断和治疗方面的需求,更进一步促进了杂交瘤细胞体外培养生产技术的发展,体外培养杂交瘤细胞生产的单克隆抗体已应用到许多方面。由于杂交瘤细胞的半贴壁性质,无论是悬浮培养还是贴壁培养,均可进行杂交瘤细胞的体外大规模培养。针对应用于体外诊断试剂的杂交瘤细胞体外培养制备单克隆抗体进行综述,主要包括中空纤维细胞培养和生物反应器细胞培养方法,以及不同培养方法优化的进展。     

Carbonic anhydrase--marker of cell type in cell culture of the guinea pig vas deferens]

Polyclonal antibodies (PCAB) to smooth muscle myosin (SMM), monoclonal antibodies (MCAB) to cytokeratin 8 (clon HI, IgGI) and H4 (IgM), as well as PCAB to carbonic anhydrase III were used for identification of the cell types in the vas deferens cell culture of guinea pig. Smooth muscle cells (SMC) are identified by intensive staining of PCAB to SMM. Fibroblast-like cells (FBL) are determined by the presence of the filament finest network, apparently responding to the myosin non-muscular forms, which are present in PCAB to SMM. The epithelial cells are stained by MCAB to cytokeratins. PCAB to carbonic anhydrase III interact with all three cell types. In the majority of SMC the enzyme is detected as solitary stripes, though there are diffuse ones across the whole cytoplasms, the nucleus remains clearly visible. Carbonic anhydrase III in epithelial cells is detected only in nucleoli and along nucleus membrane while in FBL--in nucleoli and cytoplasm as focal granulation. PCAB to carbonic anhydrase III may serve as a universal marker for identification of cell type in the guinea pig vas deferens cell culture.     

Isolation of monoclonal antibodies against avian oncornaviral protein p19

For the production of monoclonal antibodies against pp60src and the gag precursor protein Pr76gag, the spleens of mice bearing tumors that had been induced by avian sarcoma virus Schmidt-Ruppin D-transformed cells were used. One hybridoma culture produced antibodies that were directed against the p19 portion of the gag precursor. However, no antibodies directed against pp60src could be detected in any of the hybridoma supernatants. The anti-p19-producing hybridoma culture was cloned twice in soft agar, and a stable clone was used for the production of high-titer ascites fluid in mice. The monoclonal antibodies belonged to the immunoglobulin G subclass 2b. The antibodies precipitated Pr76gag and the processed virion-associated p19, as well as the 75,000-molecular-weight gag fusion protein from avian erythroblastosis virus-transformed bone marrow cells. Also, viral ribonucleoprotein complexes were specifically precipitable, indicating that they contain p19 molecules.     

Microimmunofluorescence using Terasaki plates and direct plate freezing method--rapid and reliable screening system of hybridomas

Microimmunofluorescence using Terasaki plates and a direct plate freezing method were combined for effective screening of hybridoma supernatants. The microplates, in which the fused cells (myeloma and spleen cells) were cultured and hybridoma colonies were growing, were frozen after harvest of supernatants and saved at -80 C for several weeks without affecting antibody production ability of hybridomas. Microimmunofluorescence was performed in Terasaki plates on which target cells were attached by poly-L-lysine and glutaraldehyde or by short time culture of the cells in Terasaki plates. The direct plate freezing method prevented initial hybridoma cells from changes or disappearance of antibody productions during screening of hybridoma supernatants; the microimmunofluorescence staining method permits fast and detailed estimation of specificity of antibodies of hybridomas by saving time and minimal consumption of supernatant for checking. The combination of these two methods is a powerful tool for obtaining desired monoclonal antibodies.     

A structured kinetic modeling framework for the dynamics of hybridoma growth and monoclonal antibody production in continuous suspension cultures

A structured kinetic model is developed to describe the dynamics of hybridoma growth and the production of monoclonal antibodies and metabolic waste products in suspension culture. The crucial details of known metabolic processes in hybridoma cells are incorporated by dividing the cell mass into four intracellular metabolic pools. The model framework and structure allow the dynamic calculation of the instantaneous specific growth rate of a hybridoma culture. The steady state and dynamic simulations of the model equations exhibit excellent agreement with experimentally observed trends in substrate utilization and product formation. The model represents the first to include any degree of metabolic detail and structure in describing a hybridoma culture. In so doing, it provides the basic modeling framework for incorporating further details of metabolism and can be a useful tool to study various strategies for enhancing hybridoma growth as well as viability and the production of monoclonal antibodies in suspension cultures.     

The detection of lipofuscin in a culture of hybridoma cells

Lipofuscin granules (LG) are found in the cultured hybridoma cells producing monoclonal antibodies to phage. LG have been studied using light and electron microscopy. Luminescent spectra of LG clusters in hybridoma cells are presented. The increase of own luminescence intensity of LG in the course of excitation by ultraviolet (365/nm) is shown. The advantages of hybridoma cells culture for investigation of LG on the cell level are discussed.     

Human monoclonal antibodies derived from pleural effusion lymphocytes of a patient with breast carcinoma react with human breast cancer-associated antigens and mouse mammary tumor virus polypeptides

Four human hybridoma cell lines (PEB1-4) were established from a fusion of pleural effusion lymphocytes isolated from a breast cancer patient with metastatic disease, 6 years postmastectomy. The hybridomas secreted IgG-k (3 micrograms/ml/10(6) cells). These monoclonal antibodies (PEB1-4) reacted to different degrees with mouse mammary tumor virus (MMTV) and T47D particles (HuMTV). Immunological cross-reaction was also detected with antigens isolated from body fluids of breast cancer patients (BF-Ag). The binding capacity of the monoclonal antibodies (MAbs) PEB1-4 to the above-mentioned antigens was measured by RIA. The specificity of these antibodies was further demonstrated by radioimmunoprecipitation of MMTV, T47D (HuMTV) and BF-Ag. The binding of PEB1-4 to surface antigens of intact cells grown in culture was measured by RIA. Some of the MAbs were shown to bind more avidly to breast cancer cells than to nonbreast cancer cells or nonmalignant cells. The PEB1-4 human monoclonal antibodies may be found useful in analyzing the virus-breast cancer relationship.     

Advantages of using swine serum in culturing animal and human cell lines

Using the culture of lymphoid human cells, mice myeloma cells and hybridoma (the latter was obtained by fusion of myeloma cells with those of mice spleen immunized with phage lambda), the fetal serum was shown to be surpassed in growth activity by that from adult swines. This fact is especially pronounced at small serum concentrations. When hybridoma cells were cultured there were no differences in titre of monoclonal antibodies specific to phage lambda with the use of both sera. The possibility of substitution of swine serum for human one was demonstrated using the culture of lymphocytes from human peripheral blood.     

Continuous delivery of a monoclonal antibody against Reissner’s fiber into CSF reveals CSF-soluble material immunorelated to the subcommissural organ in early chick embryos

The subcommissural organ (SCO) is an ependymal differentiation located in the dorsal midline of the caudal diencephalon under the posterior commissure. SCO cells synthesize and release glycoproteins into the cerebrospinal fluid (CSF) forming a threadlike structure known as Reissner’s fiber (RF), which runs caudally along the ventricular cavities and the central canal of the spinal cord. Numerous monoclonal antibodies have been raised against bovine RF and the secretory material of the SCO. For this study, we selected the 4F7 monoclonal antibody based on its cross-reactivity with chick embryo SCO glycoproteins in vivo. E4 chick embryos were injected with 4F7 hybridoma cells or with the purified monoclonal antibody into the ventricular cavity of the optic tectum. The hybridoma cells survived, synthesized and released antibody into the CSF for at least 13 days after the injection. E5 embryos injected with 4F7 antibody displayed precipitates in the CSF comprising both the monoclonal antibody and anti-RF-positive material. Such aggregates were never observed in control embryos injected with other monoclonal antibodies used as controls. Western blot analysis of CSF from E4-E6 embryos revealed several immunoreactive bands to anti-RF (AFRU) antibody. We also found AFRU-positive material bound to the apical surface of the choroid plexus primordia in E5 embryos. These and other ultrastructural evidence suggest the existence of soluble SCO-related molecules in the CSF of early chick embryos.C. Hoyo-Becerra and M.D. López-ávalos contributed equally to this study and should be considered as first authors. C. Hoyo-Becerra was the recipient of a predoctoral fellowship (PFPI) from the Ministerio de Educacion y Cultura (Spain). This work was supported by grants from DGICYT (BFI2003-03348; Spain) and FIS (01/0948; Spain), FIS (01-0948, PI021517; Spain) and ISCIII (red CIEN, nodo Fundación Carlos Haya).     

Interleukin-10 expression after intramuscular DNA electrotransfer: kinetic studies

A set of monoclonal antibodies that recognizes a Trypanosoma cruzi 45-kDa protein was produced and used to characterize this molecule and study its role in trypanosome adhesion to heart myoblasts. We found that the 45-kDa protein is a surface mucin, is expressed only in invasive trypomastigotes, but not in noninvasive epimastigotes or amastigotes, and is released by the trypanosome in culture medium. One of the monoclonal antibodies (Mab B5) from this set inhibits the attachment of trypomastigotes to heart myoblasts preventing trypanosome entry, whereas the others (Mabs B4 and F1) do not. This inhibition was seen with the B5 hybridoma culture supernatant, with the purified Mab B5 IgG or with Mab B5 Fab fragments. These novel findings identify the 45-kDa mucin as a new T. cruzi ligand that is used by invasive forms of this organism to adhere to heart myoblasts.     

Monoclonal antibodies against Mycoplasma hyorhinis: A secondary effect of immunization with cultured cells

Monoclonal antibodies were prepared against two different human tumour cell lines, the melanoma cell line SK-Mel-25 and the acute lymphoblastic leukemia T cell line CCRF-CEM. Presence of antibodies against human tumour cells in the supernatants of hybridoma cultures was tested by binding of ¹²⁵I-F(ab′)₂ anti-mouse IgG. On two occasions a hybridoma culture, initially selected for subsequent cloning as it seemingly produced antibodies against tumour cells, was later found to produce monoclonal antibodies specific for Mycoplasma hyorhinis. In immunofluorescent staining patchy structures were visible which seemed to be attached to the cell surface. By combined staining with FITC-conjugated anti-mouse immunoglobulin for monoclonal antibody, Evans blue for cytoplasm and Hoechst compound no. 33258 for DNA, the reaction against mycoplasma could be recognized. These results demonstrate that if cultured cells are used for preparation of monoclonal antibodies, there is a good chance that the selected hybridomas may produce antibodies against ‘culture artifacts’ such as mycoplasmas, in addition to the target antigens. Thus mycoplasma contamination of cell cultures poses a serious problem in the hybridoma research and the testing system for antibody specificity should be carefully monitored.     

A hyman hybrid hybridoma producing a bispecific monoclonal antibody that can target tumor cells for attack by Pseudomonas aeruginosa exotoxin A

By fusing a human hybridoma producing an IgG2 antibody against human A431 epidermoid carcinoma cells with an Epstein-Barr virus-transformed human B lymphocyte producing an IgG2 antibody against Pseudomonas aeruginosa exotoxin A, we established a hybrid hybridoma producing a bispecific monoclonal antibody reacting with both A431 cells and the exotoxin. Human IgG was purified from the culture supernatant of the hybrid hybridoma, and the bispecific monoclonal antibody in the IgG preparation was further separated from the two parental antibodies by hydroxyapatite high-performance liquid chromatography. The human bispecific monoclonal antibody thus obtained efficiently targeted the antibody-reative cells, A431, for attack by the exotoxin in vitro.Abbreviations bs mAb Bispecific Monoclonal Antibody - HRP Horseradish Peroxidase - MHA Mixed Hemadsorption Assay - MTT 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium Bromide - PEA Pseudomonas aeruginosa Exotoxin A - PEG Polyethylene Glycol     

牛血清白蛋白单克隆抗体杂交瘤细胞株的建立及鉴定

用牛血清白蛋白(BSA)免疫BALB/c小鼠,取其脾细胞与小鼠骨髓瘤细胞SP2/0进行融合,培养上清经过双抗体夹心法检测初步筛选分泌鼠IgG的杂交瘤细胞,将此种杂交瘤细胞注射小鼠产生的腹水用间接ELISA法筛选,获得4株能稳定分泌抗BSA单克隆抗体的杂交瘤细胞株,分别命名为2A5、3A3、3G6、4A8。鉴定结果显示,2A5细胞分泌IgG2a/κ,其余3株细胞分泌IgG1/κ;纯化后4株腹水单抗的纯度达90%以上,对BSA的ELISA滴度均可达到1∶100000以上;4株单抗均不与人以及马、猪、羊、兔、豚鼠等血清发生交叉反应;W estern B lotting试验证明4株单抗均识别分子量为68000的BSA;用间接ELISA法测定4株单抗相对亲和力及相对敏感度大小依次为3A3>2A5>3G6>4A8;杂交瘤细胞株连续培养3个月以及冻存半年后复苏,细胞生长良好,杂交瘤细胞分泌的抗体效价稳定。     

A Rapid Method to Characterize Mouse IgG Antibodies and Isolate Native Antigen Binding IgG B Cell Hybridomas

B cell hybridomas are an important source of monoclonal antibodies. In this paper, we developed a high-throughput method to characterize mouse IgG antibodies using surface plasmon resonance technology. This assay rapidly determines their sub-isotypes, whether they bind native antigen and their approximate affinities for the antigen using only 50 μl of hybridoma cell culture supernatant. Moreover, we found that mouse hybridomas secreting IgG antibodies also have membrane form IgG expression without Igα. Based on this surface IgG, we used flow cytometry to isolate rare γ2a isotype switched variants from a γ2b antibody secreting hybridoma cell line. Also, we used fluorescent antigen to single cell sort antigen binding hybridoma cells from bulk mixture of fused hybridoma cells instead of the traditional multi-microwell plate screening and limiting dilution sub-cloning thus saving time and labor. The IgG monoclonal antibodies specific for the native antigen identified with these methods are suitable for in vivo therapeutic uses, but also for sandwich ELISA assays, histology, flow cytometry, immune precipitation and x-ray crystallography.     

Effects of two different nutrition supply methods on improving hybridoma cell production

Hybridoma cells are featured by the effective utilization of both B lymphocytes and immortalized myeloma cells, allowing for the continuous generation of monoclonal antibodies specific to antigens. With regard to conventional hybridoma technology, B lymphocytes must be fused with myeloma cells using various methods to generate hybridoma cells. Nutrition plays an important role in hybridoma cell survival and amplification, which determines the fusion effect and antibody production. Here we compared the growth and survival rates of hybridoma in a commonly used peritoneal macrophage feeder layer (PMFL) nutrition supply system with a commercial hybridoma feeder additive (HFA) nutrition supply system at the post fusion stage and discussed the titer of monoclonal antibodies by enzyme linked immunosorbent assay (ELISA). Our results indicate that commercially available HFA promotes the survival and amplification of hybridoma clones and improves the titer of monoclonal antibodies indirectly.     

Monoclonal antibody metabolism during the growth of hybridoma cells

Metabolism of monoclonal antibodies (MAb) during the growth of mouse hybridoma, producing MAb to phage lambda, has been studied. It was shown that the specific production of MAb decreased by 25-35% in the stationary phase of growth in comparison with the middle of the exponential growth phase, which was associated with the decrease in the rate of MAb synthesis. The secretion kinetics of MAb did not change during the growth of hybridoma cells. MAb did not degrade inside the cells and in the culture medium after being secreted. The ratio of the synthesis rate of MAb to that of cellular proteins increased from 7-10% in the exponential growth phase to 14-18% in the stationary phase, which points to a specific regulation of MAb synthesis in comparison with cellular proteins. Possible regulation mechanisms for synthesis of MAb and cellular proteins during the growth of hybridoma cells are discussed.     

Modulation of hybridoma cell growth and antibody production by coating cell culture material with extracellular matrix proteins

The influence of coating polystyrene tissue culture plates with different proteins on murine hybridoma cell growth and antibody production was investigated. Fibronectin, collagen I, bovine serum albumin and laminin were used to coat NUNC^® and COSTAR^® cell culture plates. Cell number and antibody concentration in culture fluids were quantified as indicators for cell viability, proliferation and productivity. Adhesive behaviour, morphology, expression of surface receptors of hybridoma cells and the presence of tyrosine-phosphorylated proteins in cell lysates were characterized by cell adhesion experiments, microscopy, flow cytometry and Western Blot analysis.It was shown that coatings with fibronectin (0.2 μg/ml) lead to a substantial improvement of cell growth by 50–70% and an increase of monoclonal antibody production by 100–120%.Collagen I coatings showed an improvement in cell growth by 30–70% and by 60% for the production of monoclonal antibodies. Coatings with BSA and laminin had minor effects on these parameters. It was found that the hybridoma cell lines used in this study did not express the α₂-chain of the α₂β₁-integrin, which is responsible for binding to collagen and laminin.However, the presence of β₁-integrin on the cell surface was shown, which should enable hybridoma cells to bind fibronectin. We propose, therefore, that fibronectin adsorption to cell culture materials may be a promising approach to enhance the production of monoclonal antibodies by cultivated hybridoma cells.     

Utilization of leucine methyl ester for the generation of hybridomas producing monoclonal antibodies specific to tumor-associated antigens

In an attempt to obtain monoclonal antibodies specific to tumor-associated antigens. C3H/He mice were immunized with syngeneic MM2 tumor cells, and the primed spleen cells were fused with P3-X63-Ag8.653 myeloma cells. The outgrowth of hybridomas, however, was extremely low and monoclonal antibodies were not obtained. The reason for the low hybridoma growth was studied. It was found that MM2 cells used as the immunogen, the fusion partner myeloma cells and the resulting hybridomas shared at least one tumor-associated antigen, namely Q5 antigen. Because of this common antigen, cytotoxic cells, presumably cytotoxic T lymphocytes, which were lytic to the hybridomas, were induced during the culture for generation of the hybridomas. Removal of lysosome-rich cells, including cytotoxic T lymphocytes, from the primed spleen cells before the fusion by treatment with leucine methyl ester, a lysosomotropic agent, drastically improved the outgrowth of hybridomas. By this method, seven stable hybridoma clones producing monoclonal antibodies specific to tumor-associated antigens were obtained. Two of the seven clones were found to secrete monoclonal IgM species, which reacted with the extra-cellular region of the Q5 antigen. This procedure will be an option when production of monoclonal antibodies specific to cell-surface antigens is intended and outgrowth of hybridomas is unexpectedly low.     

日本血吸虫重组信号蛋白14—3—3的纯化及单克隆抗体的制备

纯化日本血吸虫（中国大陆株）重组信号蛋白（rSj14—3—3）,并制备其单克隆抗体。以纯化后的rsj14-3—3蛋白为抗原免疫Balb／c小鼠,用杂交瘤技术制备抗rSj14-3-3的单克隆抗体,并通过ELISA方法和Westernblotting测定抗体的效价与特异性。获得了大量高纯度的rSj14-3-3蛋白：筛选出了能够稳定分泌抗rSj14．3．3单抗的杂交瘤细胞株3H6。单抗亚型为IgG1。实验依靠大肠杆菌表达系统高效表达了rSj14—3—3蛋白,并利用该蛋白制备了单克隆抗体．可用于今后血吸虫病免疫诊断的实验研究。