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A Jungbauer

Publications and source records attributed to A Jungbauer.

69 records · Page 4Linked to original sources
PubMed1990

Isolation of isoproteins from monoclonal antibodies and recombinant proteins by chromatofocusing.

A fast protein liquid chromatographic method for the preparative separation of the various isoproteins is described. Highly purified human monoclonal antibodies, recombinant human superoxide dismutase and human superoxide dismutase from erythrocytes were used as starting material. The isoproteins were separated by chromatofocusing on Mono P columns. A very narrow pH gradient was applied to achieve complete separation of the isoproteins. The prepurification steps and the pretreatment of the samples to achieve optimum resolution are described in detail. The method is also applicable to extremely basic monoclonal antibodies (pI = 9). The successful separation was checked by isoelectric focusing in immobilized pH gradients (Immobilines). The future of these methods is discussed, because for many different biochemical and biophysical investigations pure and homogeneous isoproteins are necessary.

Antibodies, Monoclonal↗
PubMed1990

Preparative purification of human monoclonal antibody isoforms in a multi-compartment electrolyser with immobiline membranes.

The performance of a multi-compartment electrolyser with isoelectric Immobiline membranes for large-scale protein purification is evaluated. Owing to the presence of isoelectric membranes possessing a high buffering capacity and ionic strength, isoelectric protein precipitation inside the membranes, one of the major drawbacks of present membrane uses, is fully avoided. In addition, owing to this novel membrane technology, pH gradient decay, typical of isoelectric focusing in carrier ampholytes, is fully eliminated and pH and conductivity constancy is guaranteed in all flow chambers for running periods of more than 11 days (160,000 V h). The membranes described possess a unique selectivity, in that they act by modulating the surface charge (i.e., the mobility) of macroions crossing or tangential to them. The concept of isoelectric Immobiline membranes acting like a pH-stat unit is introduced. Protein homogeneity in each chamber of the electrolyser can be achieved even when purifying human monoclonal antibodies against HIV-1, which possess high pI values (9.0-9.6), are large molecules (Mr 150,000) and are fractionated in the presence of large micelles of neutral detergents.

Antibodies, Monoclonal↗
PubMed1990

Shifts of isoelectric points between cellular and secreted antibodies as revealed by isoelectric focusing and immobilized pH gradients.

Charge microheterogeneity of monoclonal antibodies, as revealed by isoelectric focusing in carrier ampholytes, has been known for a long time. Here we demonstrate, in the case of monoclonals against the gp-41 of the HIV-1 virus, that this heterogeneity is already present within the cell sap of hybridoma cells during antibody synthesis. When the monoclonals are secreted extracellularly, the same isoelectric point (pI) spectrum is maintained, but there is marked redistribution of the relative isoform abundance towards the lower pI components. This suggests in vivo processing of such forms, possibly via glycosylation or deamidation. The secreted antibodies are also analyzed by immobilized pH gradients (IPG), where they demonstrate an even more extensive heterogeneity, due to the marked increment in resolving power. Single bands are purified by preparative IPGs in a multicompartment electrolyzer and are shown to be stable with time. Thus, artefactual heterogeneity produced by the focusing technique is completely excluded and cellular processing is clearly established.

Animals↗
PubMed1989

High-performance liquid chromatographic determination of metabolic products for fermentation control of mammalian cell culture: analysis of carbohydrates, organic acids and orthophosphate using refractive index and ultraviolet detectors.

A method for the determination of carbohydrate substrates and excreted metabolic end-products of cell culture supernatants using a strong cation-exchange column in the H+ form has been developed. Organic acids and carbohydrates can be determined in addition to orthophosphoric acid. Pyrrolidone carboxylic acid, resulting from chemical conversion of the amino acid glutamine during the incubation of fresh medium and during the fermentation process, can be determined. The chromatographic method allows the correction of glutamine uptake values for physiological studies. Measured values of pyrrolidone carboxylic acid in supernatants of human hybridoma cell line show that it cannot be consumed by the cells. This technique allows the separation of major metabolites used in process optimization. Peak homogeneity is proved by on-line monitoring of the effluent with an ultraviolet (214 nm) and a refractive index detector connected in series.

Acids↗
PubMed1989

Comparison of protein A, protein G and copolymerized hydroxyapatite for the purification of human monoclonal antibodies.

Protein A Superose, protein G Sepharose fast flow and copolymerized hydroxyapatite were used for the purification of human monoclonal antibodies against HIV 1. Both desalted culture supernatant and a prepurified protein solution were used as starting materials. The different runs were compared with respect to yield and recovery of biological activity. The biological activity (specific reactivity) was checked by antigen enzyme-linked immunosorbent assay with recombinant antigen. The human monoclonal antibodies could not be selectively eluted from the hydroxyapatite but elution could be effected from the protein A Superose at pH 4.0 and from protein G at pH 3.0. The eluted immunoglobulin G was distributed over a broad pH range when protein G Superose was used. Biologically active material could be obtained from protein A Superose and protein G Sepharose fast flow.

Antibodies, Monoclonal↗
PubMed1989

Application of a human monoclonal antibody in a rapid competitive anti-HIV ELISA.

The ELISA is the established screening technique for the detection of antibodies directed against HIV. The first generation assays, mostly based on the sandwich principle, employed purified virus from cell culture and gave both false-positive and false-negative results. Sandwich-type assays preferentially detect IgG antibodies, require a high serum dilution and are two-step procedures. In order to detect an immune response as early as possible after infection anti-HIV antibodies of the IgM class should also be measured. To this end a competitive ELISA has been developed using a solid phase-adsorbed recombinant HIV envelope protein and an enzyme-labelled human monoclonal antibody. This detects both IgM and IgG antibodies, the results are available within 1 h and a serum predilution is not necessary.

Antibodies, Monoclonal↗
PubMed1989

Isolation of human monoclonal antibody isoproteins by preparative isoelectric focusing in immobilized pH gradients.

A method for preparative isolation of human monoclonal antibody isoproteins is described in the present paper. A human monoclonal antibody directed against the transmembrane protein gp 41 from the human immunodeficiency virus (HIV-1) was used in this study. The antibody belongs to the IgG1 subtype and exhibits antibody dependent cellular cytotoxicity. The resolving power of conventional preparative protein separation techniques such as ion-exchange chromatography, chromatofocusing and lectin affinity chromatography is too poor for a complete separation of isoproteins. The more sophisticated technique of chromatofocusing on FPLC-based material (Mono P, Pharmacia) did not satisfy our expectation. With semipreparative IEF in immobilized pH gradients we were able to prepare the different isoproteins of a human monoclonal antibody in milligram amounts. No significant difference between the single isoproteins with respect to specificity and avidity to the recombinant antigen (rec gp 160) was detected. Therefore, we assume that the separation conditions did not influence the immunochemical nature of the antibody and significant denaturation and/or precipitation of the IgG did not occur. Furthermore the method affords preparative separation with resolution equivalent to analytical runs. Experiments for scale up and further characterization of isoproteins (carbohydrate composition, amino acid analysis, half life times etc.) are in progress.

Animals↗
PubMed1987

Combination of Zetaprep mass ion-exchange media and high-performance cation-exchange chromatography for the purification of high-purity monoclonal antibodies.

A procedure involving diafiltration, mass ion exchange on a QAE Zetaprep disk, gel chromatography and cation-exchange chromatography was used for the purification of mouse monoclonal antibodies from hybridoma culture supernatant. Prior to the separation steps, the starting solution was adjusted to the desired pH and conductivity. Diafiltration was used for this purpose in order to keep the volume constant or even to reduce the volume of sample. A QAE Zetaprep disk was used to remove the main protein contaminants from the culture supernatant. After washing unbound proteins out of the Zetaprep disk, slightly bound protein was eluted with a buffer solution containing 50 mM sodium chloride. The monoclonal antibody was eluted with a solution containing 150 mM sodium chloride. The purity of the eluted antibody was 50%, and was increased to 99% by subsequent high-performance cat-ion-exchange chromatography. The purity was determined by means of sodium-dodecyl sulphate polyacrylamide gel electrophoresis and silver staining. The advantage of the two high-performance techniques, mass ion exchange and high-performance cation-exchange chromatography, are the high-flow-rates and the high resolution that can be obtained. These techniques are suitable for the production of injectable therapeutic preparations.

Animals↗
PubMed1987

Screening for monoclonal antibodies with covalently linked antigen.

Microtitre plates prepared for ELISA are treated for the maximum adsorption of gamma-globulins (at pH 9). The adsorption of other soluble proteins (e.g. antigens) is sometimes less effective and therefore requires a higher amount of protein for the primary coat of wells. In order to reduce the amount of pure antigen required for the screening of mAb-producing hybridomas, we improved the sensitivity of our screening ELISA technique by coupling the antigen covalently to the surface of the microtiter wells. The antigen (urokinase) was coupled by the glutaraldehyde or carbodiimide procedures respectively using "aminoplates" (Nissho Iwai, Japan). The glutaraldehyde method led to at least a five fold increase of the sensitivity compared to coventional adsorption. Reduced requirement of antigen for the assay is thus achieved by a simple procedure.

Animals↗
PubMed1987

Cross flow diafiltration of serum with basal medium suitable for growth of hybridomas, sterilization and protein reduction.

Fetal Calf Serum (FCS) was extensively extracted by cross flow diafiltration (Pellicon, Millipore) and sterilized using the basal growth medium (DMEM) for the extraction. Ultrafiltration membranes of 10(5) and 3 X 10(5) Dalton cut off were used respectively. The diafiltrates were used for hybridoma cultivation and the results of growth and mAb-production were compared with standard medium (DMEM + 5% FCS). Slightly reduced mAb-titers were achieved. These were, however, compensated by decreased concentration of contaminating protein and higher specific mAb/protein ratio as examined by SDS-PAGE and enzyme linked immuno electro transfer blot (EITB).

Animals↗
PubMedDate not supplied

Pilot scale production of a human monoclonal antibody against human immunodeficiency virus HIV-1.

Human monoclonal antibodies against the transmembrane protein gp41 of HIV-1 were isolated and purified on a pilot scale. A purification scheme was established for the production of human monoclonal antibodies on the gram scale. 50 1 of culture supernatant can be treated in one purification cycle. The hybridomas were mass cultured in an airlift fermenter. The culture broth was clarified by microfiltration and chromatographed on CM-Sepharose fast flow and protein A Superose. Scale up of the high performance affinity chromatography from 1 ml protein A Superose up to 40 ml is described. All desalting steps were performed by gel filtration on Sephadex G-25 coarse. The yield of the whole purification procedure is in the range of 50-60%. The purity is higher than 99.9%. DNA and reverse transcriptase could not be detected. The whole method is designed as a basis for scale up to industrial scale. Results from quality control assays have proven the validity of this approach.

Antibodies, Monoclonal↗
PubMedDate not supplied

Continuous removal of protein aggregates by annular chromatography.

The removal of polymeric proteins from their monomers is a frequently encountered separation task, especially in the polishing step of therapeutic proteins. Continuous separation of protein polymers from monomers by annular chromatography using size exclusion chromatography has been studied regarding the resolution, recovery, fouling, and productivity and has been compared to conventional chromatography. An IgG preparation rich in aggregates was used as a model protein mixture. Under conditions that maximized the throughput, the polymers could be separated from the monomers, but baseline separation could not be achieved. Baseline separation was also not possible in batch mode using equivalent conditions, which was also confirmed by computer simulation. For separation of the aggregates from the product the entire available separation space (360 degrees ) was indispensable. Therefore only cyclic, discontinuous regeneration could be carried out. Loading was identified as a critical step, since the concentrated protein solution evaded into the headspace instead of migrating into the gel where viscous fingering often occurs in conventional chromatography. The productivity of annular chromatography was two times higher than that of the conventional batch chromatography, and the buffer consumption was reduced to half the conventional value. These two benefits are especially important for protein separation processes that suffer from low loadability, such as size exclusion chromatography. We have demonstrated that size exclusion can be performed on an industrial scale when it is run continuously with the aid of a pressurized annular chromatograph.

Chromatography, Gel↗
PubMedDate not supplied

Flocculation: an alternative process to ion-exchange chromatography: (A scale-up study using recombinant human superoxide dismutase as model protein).

Flocculation using pellicular charged flocculants was investigated as an alternative process to conventional chromatography in purification of recombinant proteins using human recombinant superoxide dismutase expressed in E. coli as a model system. The removal of pyrogens, proteins, debris and the yield were determined. At laboratory scale, the starting conditions were optimized to yield a stable solution and the flocculation process fitted into a purification scheme. 100 L fermentation broth was the initial volume at pilot scale. The process parameters determined at the laboratory scale were tested and the results were compared to the pilot scale. The method was also compared to an ion-exchange chromatography.

Chromatography, Ion Exchange↗