Purification of monoclonal antibodies from ascites using ABx liquid chromatography column

Strategy for Development of Site-Specific Ubiquitin Antibodies

Protein ubiquitination is a key post-translational modification regulating a wide range of biological processes. Ubiquitination involves the covalent attachment of the small protein ubiquitin to a lysine of a protein substrate. In addition to its well-established role in protein degradation, protein ubiquitination plays a role in protein-protein interactions, DNA repair, transcriptional regulation, and other cellular functions. Understanding the mechanisms and functional relevance of ubiquitin as a signaling system requires the generation of antibodies or alternative reagents that specifically detect ubiquitin in a site-specific manner. However, in contrast to other post-translational modifications such as acetylation, phosphorylation, and methylation, the instability and size of ubiquitin-76 amino acids-complicate the preparation of suitable antigens and the generation antibodies detecting such site-specific modifications. As a result, the field of ubiquitin research has limited access to specific antibodies. This severely hampers progress in understanding the regulation and function of site-specific ubiquitination in many areas of biology, specifically in epigenetics and cancer. Therefore, there is a high demand for antibodies recognizing site-specific ubiquitin modifications. Here we describe a strategy for the development of site-specific ubiquitin antibodies. Based on a recently developed antibody against site-specific ubiquitination of histone H2B, we provide detailed protocols for chemical synthesis methods for antigen preparation and discuss considerations for screening and quality control experiments.

Production of bispecific antibodies

Bispecific antibodies (bsAbs) contain two different binding specificities within a single molecule and can specifically bind two different molecules together. BsAbs can be produced by chemically cross-linking purified antibodies or Fab fragments with reducible disulfide bonds or nonreducible thioether bonds, both of which are described in this unit. Protocols are also presented for producing BsAbs by fusing two antibody-producing hybridomas that can be selected for based on drug resistance, or by double labeling with fluorochromes and FACS. Support protocols describe screening and purification of bsAbs.

Rapid detection of enterotoxigenic Escherichia coli O6 in water by using monoclonal antibody and a photon-counting television camera

Monoclonal antibodies (MAbs) raised against Escherichia coli O6:H16 were screened against 15 strains of E. coli and 19 non-E. coli bacteria. A MAb-luminescence assay using MAb-5.8, which shows no cross-reactions with non-E. coli bacteria, and a photon-counting television camera were developed for rapid enumeration of E. coli O6:H16 in water. The membrane filter that retained bacteria was boiled for 5 min in a buffer and incubated with biotinylated MAb-5.8. After incubation with streptavidin-peroxidase conjugate, it was reacted with luminol-based reaction mixture. Luminous image and light intensity of the filter was recorded with a Biocell Counter. Levels of E. coli O6 higher than 7 x 10(3) CFU were detected by the MAb-luminescence assay when E. coli O6 was spotted onto the membrane filter. The sample that contained E. coli O6:H16 was filtered through a membrane filter, and the filter that retained bacteria was incubated on a filter paper soaked with nutrient broth supplemented with 0.5% NaCl at 37 degrees C for 6 h. The number of light emission points on the filter correlated well with initial E. coli O6:H16 counts within the range of 1 to 3 x 10(2) CFU. The correlation coefficient was 0.89.

Monoclonal antibody mapping of the envelope glycoprotein of the dengue 2 virus, Jamaica

Although dengue (DEN) virus is the etiologic agent of dengue fever, the most prevalent vector-borne viral disease in the world, precise information on the antigenic structure of the dengue virion is limited. We have prepared a set of murine monoclonal antibodies (MAbs) specific for the envelope (E) glycoprotein of DEN 2 virus and used these antibodies in a comprehensive biological and biochemical analysis to identify 16 epitopes. Following domain nomenclature developed for the related flavivirus, tick-borne encephalitis, three functional domains were identified. Five epitopes associated with domain A were arranged in three spatially independent regions. These A-domain epitopes were destroyed by reduction, and antibodies reactive with these epitopes were able to block virus hemagglutination, neutralize virus infectivity, and block virus-mediated cell membrane fusion. Domain-A epitopes were present on the full-length E glycoprotein, a 45-kDa tryptic peptide representing its first 400 amino acids (aa) and a 22-kDa tryptic peptide representing at least aa 1-120. Four epitopes mapped into domain B, as determined by their partial resistance to reduction and the localization of these epitopes on a 9-kDa tryptic or chymotryptic peptide fragment (aa 300-400). One domain-B-reactive MAb was also capable of binding to a DEN 2 synthetic peptide corresponding to aa 333-351 of the E glycoprotein, confirming the location of this domain. Domain-B epitopes elicited MAbs that were potent neutralizers of virus infectivity and blocked hemagglutination, but they did not block virus-mediated cell-membrane fusion. Domains A and B were spatially associated. As with tick-borne encephalitis virus, determination of domain C was more problematic; however, at least four epitopes had biochemical characteristics consistent with C-domain epitopes.

Production and characterization of monoclonal antibodies directed against the Ah receptor

Six hybridomas secreting monoclonal antibodies that are specific for the N-terminal peptide sequence of the murine Ah receptor were isolated. These antibodies bind with high specificity to the Ah receptor on protein blots of Hepa 1c1c7 cytosol. Three IgG1 antibodies (Rpt 1, 2, and 3) were capable of detecting 2 ng of receptor using peroxidase-goat anti-mouse IgG antibody conjugate on a protein blot. Monoclonal antibody Rpt 9 exhibited the greatest ability to immunoprecipitate the nondenatured 9S form of the Ah receptor and to visualize the AhR on liver tissue sections using immunohistochemical techniques. All of the monoclonal antibodies produced were able to bind to the mouse, rat, and human Ah receptor. These monoclonal antibodies should be useful in a wide number of applications in the study of Ah receptor biochemistry.

A new monoclonal antibody (IE8) reactive with dendritically shaped cells in the human tonsil

A new monoclonal antibody (mAb), 1E8 (IgG1, kappa), was obtained from a hybridoma prepared by fusion of mouse myeloma cells (NS-1) with splenic cells of mice immunized with a human B blastic malignant lymphoma cell line, HPE-Ret-3 (Ret-3). The mAb showed a reactivity unrestricted to a specific cell lineage on flow cytometrical analysis of the reactivity with human lympho-hematopoietic cell lines. In peripheral blood, 1E8 reacted with the cells of all lineage, that is, lymphocytes, monocytes, granulocytes and platelets, even though its intensity was very low by immunohistochemistry. Immunohistochemical examination of human tonsil with 1E8 showed a characteristic staining pattern. Positive cells scattered in follicular (mantle zone and germinal center), parafollicular (T-dependent area), subepithelial and interstitial connective tissue areas. These positive cells seemed to be categorized into dendritically shaped cells (DSC), including dendritic cells (DC) and a subpopulation of macrophages in follicles, interdigitating cells (IDC) and irregularly shaped mononuclear cells. The localization of 1E8 antigen staining was similar to that of integrin CD11c, although its distribution on hematopoietic cell lines did not coincide with that of 1E8 antigen. Immunobiochemical studies showed that 1E8 bound two cell surface proteins with molecular size of 70,000-90,000 and 35,000 Da each. Consequently, 1E8 antigen might be a novel marker of DSC.

Rapid, two-step purification process for the preparation of pyrogen-free murine immunoglobulin G1 monoclonal antibodies

A cost-efficient process was specifically designed for the preparation of gram amounts of highly pure murine immunoglobulin (Ig) G1 monoclonal antibodies (mAbs). This rapid, simple and scalable purification process employs a unique binding and elution protocol for IgG1 mAbs on a silica-based, mixed-mode ion-exchange resin followed by conventional anion-exchange chromatography. mAbs are bound to BakerBond ABx medium at pH 5.6 directly from serum-supplemented hybridoma culture supernatants. Contaminating proteins and nucleic acids are removed by an intermediate wash at pH'6.5, followed by the specific elution of IgG1 mAbs with 100 mM Tris-HCl (pH 8.5). The mAb eluate is then loaded directly on to QAE-Sepharose Fast Flow medium and eluted with 10 mM sodium phosphate buffer (pH 7.4), containing 150 mM sodium chloride. The resulting IgG1 mAbs are greater than 98% pure, free from measurable endotoxin, formulated in a physiological buffer and suitable for in vivo applications.

Preparation of clinical grade monoclonal antibodies from serum-containing cell culture supernatants

Three mouse monoclonal antibodies (Mab), RIV6, MN12, and WT31, were purified from cell culture supernatants containing foetal bovine serum (FBS) by two-step purification protocols, involving protein A affinity and ion exchange chromatography. Provided that the purification conditions were adapted to the physico-chemical properties of the individual Mab, clinical grade products could be obtained. The residual levels of bovine IgG originating from FBS were below 1% on a protein basis. Endotoxin levels were below 1 ng/ml. The contents of other serum proteins, DNA, and protein A were below or near the detection limits. The final products met the requirements for therapeutic Mab. Special attention was paid to the behaviour of foetal bovine IgG in the different purification steps. Large variations in the IgG contents of different batches of FBS were observed. However, the properties of the IgG fractions of the batches were very similar. A major IgG fraction with a low affinity for protein A and with components with relatively acidic isoelectric points (pIs) was distinguished from a minor fraction exhibiting a high affinity for protein A and a more diverse pI pattern. The impact of these findings on the purification strategy used for the Mab is discussed.

Cross-talk between B cell surface immunoglobulin and interleukin 4 receptors: the role of protein kinase C and Ca2(+)-mediated signals

A well-known property of IL4 is its capacity to synergize with low concentrations of anti-immunoglobulin (Ig) antibodies to induce B cells to synthesize DNA. Cross-linking of surface Ig receptors stimulates phosphoinositide hydrolysis, with consequent production of two signals: the elevation of intracellular Ca2+ levels and activation of protein kinase C (PKC). Little is known about the second messengers utilized by interleukin (IL)4 receptors. In this study we have investigated the relative contributions of the two signals emanating from the ligation of surface Ig receptors to the synergistic activation of B cells by IL4. We show that IL4 plus carefully titrated concentrations of PKC-activating phorbol esters [such as phorbol 12,13-dibutyrate (PBu2)] induce cell cycle entry of virtually all murine B cells and substantial levels of DNA synthesis. Ca2+ ionophores, in contrast do not act as co-mitogens with IL4. However, a critical concentration of ionomycin further enhanced DNA synthesis induced by PBu2 plus IL4. Taken together, these results suggest that PKC activation alone is sufficient to synergize with IL4 in inducing B cells to enter cell cycle. However, the co-mitogenic effects of anti-Ig and IL4 are evidently also dependent on Ca2+ signals. This interpretation is supported by the findings that cyclosporin, which abrogates the activation of lymphocytes by Ca2(+)-dependent stimuli, inhibits B cell proliferation induced by anti-Ig plus IL4, but not the response to PBu2 plus IL4.

Protein A, hydroxyapatite and diethylaminoethyl: evaluation of three procedures for the preparative purification of monoclonal antibodies by high-performance liquid chromatography

Three rapid, reproducible and feasible monoclonal antibody purification procedures by means of high-performance liquid chromatography have been evaluated. The stationary phases employed were high-performance hydroxyapatite, high-performance Protein A and high-performance anion-exchange resin. The purity of the final immunoglobulin preparations was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions and, subsequently, by high-performance gel permeation chromatography. The immunoreactivity of purified monoclonal antibodies was determined by the radioimmunoassay method.

Protein purification

This monograph summarizes recent developments in the purification and analysis of natural and recombinant proteins. The basic strategies employed in protein purification are reviewed with regards to the characteristics of the protein of interest that may aid its isolation, choice of the starting material, and use of denaturants. Preparation of cell-free extracts followed by bulk precipitation and/or phase partition constitute the initial steps of many purification schemes. Chromatographic methods (size exclusion, ion exchange, hydroxylapatite, reversed phase, hydrophobic interaction and affinity based) utilizing either traditional, low pressure or high-performance liquid chromatography instrumentation are discussed. Electrophoretic techniques used to analyze the homogeneity of the protein product include SDS-PAGE, isotachophoresis, IEF and two dimensional gel electrophoresis.

Comparison of mono Q, superose-6, and ABx fast protein liquid chromatography for the purification of IgM monoclonal antibodies

Nine immunoglobulin M (IgM) monoclonal antibodies (MAbs) produced in ascites fluids or in cell culture supernatants, have been purified on a fast protein liquid chromatography (FPLC) system using anion-exchange, size-exclusion, or mixed-mode chromatography matrices. The use of a mixed-mode ABx column provided an IgM that had a purity of greater than 99% after a single purification step. Anion-exchange chromatography using a Mono Q column, provided a partial purification of the IgM which could subsequently be purified to a product of ca. 90% purity (determined from sodium dodecyl sulfate polyacrylamide gel electrophoresis) by size-exclusion chromatography on a Superose-6 column. Alternatively, the ascites containing the IgM was ammonium sulfate precipitated and chromatographed on the Superose-6 column under normal- as well as high-ionic strength conditions, which also yielded a product of ca. 90% purity. The purification of IgM from concentrated cell culture supernatants was evaluated using the Superose-6 or the ABx column. IgM purified from this source was greater than 99% pure when chromatographed on the mixed-mode column and ca. 60% pure on the size-exclusion column. MAbs from each of the procedures retained their immunoreactivity, as shown by indirect immunofluorescence staining of fixed cell preparations. A comparison of these methods revealed that mixed mode chromatography was simple, efficient, and yielded a product of high purity. The optimization of these methods facilitates the large-scale purification of mouse IgM MAbs and provides practical procedures for generating IgMs for use as diagnostic and therapeutic reagents.