Determination of monoclonal antibody production in cell culture using novel microfluidic and traditional assays

This study compares microfluidic technology (Protein 200 LabChip Assay kit, Agilent 2100 Bioanalyzer, referred to here as Protein 200) to the traditional approach for protein analysis, one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), for the sizing and quantification of immunoglobulin G (IgG) in hybridoma cell cultures. Internal references differ between each method: purified IgG was used alone in SDS-PAGE while myosin (the upper marker) was added to each sample in Protein 200. The IgG used here were produced in cultures propagated in either a serum-free or a serum-containing medium. With serum-containing samples, there was a significant difference in the IgG concentrations (p < 0.05) between SDS-PAGE and Protein 200. The concentration determined by SDS-PAGE was significantly higher (> 30%) than by Protein 200 or by high-pressure liquid chromatography (HPLC) because the large amounts of serum albumin in the samples affect the accuracy of SDS-PAGE. Protein 200 can determine size similarly to SDS-PAGE in serum-free samples (standard error of the mean, SEM, < 1%, 95% confidence < +/-1%), unlike in serum-containing samples. The Protein 200 assay was more effective than the traditional one-dimensional SDS-PAGE in determining concentration and size of IgG in cell culture samples and it provided a miniaturized and convenient platform for rapid analysis.     

Synthesis of a novel analytical reagent for the determination of active sites for conjugation on a catalytic aldolase monoclonal antibody

An optimized and scalable synthesis of a novel analytical reagent for the determination of the number of active sites available for conjugation on a catalytic aldolase monoclonal antibody (mAb) is described. The original conditions suffered from lack of reproducibility, incomplete reactions, and required several chromatographies and lyophilizations that afforded material of low purity. A redesigned route and optimized protocols have been developed that eliminate the use of toxic and unsafe reagents such as HMPA and HATU. In addition, the number of chromatographies has been reduced to only one and time-consuming and energy-intensive lyophilizations are no longer required. The overall yield has been considerably improved from the original 4% to 20% after telescoping the last two steps of the synthesis and this new approach allowed for the preparation of material with higher chemical purity (?99% vs the initial 90%) to meet specifications.     

Glutamine deamidation of a recombinant monoclonal antibody

Deamidation of glutamine (Gln) proceeds at a much slower rate than deamidation of asparagine (Asn) residues at peptide level. However, deamidation of Gln residues in native proteins may occur faster because of the impact of protein structure and thus plays a significant role in affecting protein stability. Gln deamidation of a recombinant monoclonal IgG1 antibody was investigated in the current study. Deamidation was determined by a molecular weight increase of 1 Da, a retention time shift on reversed‐phase chromatography and tandem mass spectrometric (MS/MS) analysis of the peptides. As expected, Gln residues at different locations in the three‐dimensional structure had different susceptibilities to deamidation. Gln deamidation was highly pH dependent with the highest level detected in the sample incubated at pH 9, and lowest level at pH 6 in the pH range from 5 to 9. The detection of significant levels of Gln deamidation suggested that it may play an important role in affecting heterogeneity and stability of recombinant monoclonal antibodies. Copyright © 2008 John Wiley & Sons, Ltd.     

Purification of monoclonal antibody from tobacco extract using membrane-based bioseparation techniques

Transgenic plants offer a promising system for large-scale production of therapeutic proteins such as monoclonal antibodies (mAbs). This paper describes a membrane-based process suitable for purification of a humanized mAb expressed in tobacco. Most monoclonal antibody purification schemes rely on the use of Protein A as the affinity ligand for antibody capture. The main objective of our work was to develop non-Protein A-based purification methods to avoid some of the problems and limitations associated with this ligand, e.g. cost, immunotoxicity, and antibody aggregation during elution. Ion exchange membrane chromatography (IEMC) was used for primary capture and preliminary purification of the mAb from tobacco juice. Hydrophobic interaction membrane chromatography (HIMC) was then used for high-resolution purification, followed by ultrafiltration for polishing, desalting and buffer exchange. Using this scheme, both high mAb purity (single peak in size exclusion chromatogram, i.e., ca. 100% purity) and high recovery (77% of mAb spiked into the tobacco extract) were achieved. Membrane chromatography is generally considered unsuitable for resolving bound proteins by gradient elution and is therefore commonly used in the bind and elute mode with a single-step change of mobile phase. We show that the gradient elution process in the HIMC step can be optimized to increase the resolution and thereby obtain product of high purity.     

Quick analysis of baicalin in Scutellariae Radix by enzyme-linked immunosorbent assay using a monoclonal antibody

To establish an immunoassay for baicalin (BA), a hybridoma cell line (9D6) secreting a monoclonal antibody (MAb) against BA was prepared by cell fusion with splenocytes derived from a mouse immunized with BA-bovine serum albumin (BSA) conjugate and a myeloma cell line, SP2/0-Ag14. MAb 9D6 shows specific reactivity against BA and its aglycone, baicalein, but not against other natural products. We developed an enzyme-linked immunosorbent assay (ELISA) using MAb 9D6 in a competitive manner, ranging from 200 ng/mL to 2 μg/mL. After validating the developed ELISA on the basis of intra- and inter-assays and a recovery experiment, it was found that the ELISA was not only simple, but also sufficiently reliable and accurate for quality control of Scutellariae Radix. It allowed determination of BA in complex and mixed materials, such as Kampo medicines.     

Sensitivity of steroid enzyme immunoassays. Comparison of four label enzymes in an assay system using a monoclonal anti-steroid antibody

The sensitivities of monoclonal antibody-based enzyme immunoassays for 11-deoxycortisol using alkaline phosphatase (AP), horseradish peroxidase (HRP), beta-galactosidase (beta-GAL) and glucose oxidase (GOD) as labels were compared. The anti-11-deoxycortisol antibody used was that produced in ascites by inoculating antibody-secreting hybridoma cells into mice. Enzyme labeling of 11-deoxycortisol was carried out by the N-succinimidyl ester method. The activated ester of 4-(2-carboxyethylthio)-11-deoxycortisol was treated with each enzyme to give a homologous enzyme-labeled antigen. In the competitive immunoassay, the bound and free enzyme-labeled antigens were separated by a double antibody method and the enzymic activity of the immune precipitate was determined by colorimetric and fluorimetric methods. The AP activity was measured in three ways, using p-nitrophenyl phosphate, nicotinamide adenine dinucleotide phosphate (NADP), and 4-methylumbelliferyl phosphate as substrates. o-Nitrophenyl beta-D-galactopyranoside and 4-methylumbelliferyl beta-D-galactopyranoside were used for beta-GAL, and 3,3',5,5'-tetramethylbenzidine (TMB) and 3-(p-hydroxyphenyl)propionic acid (HPPA) for HRP. In the case of GOD, TMB and HPPA were used in combination with HRP. A dose-response curve with a high sensitivity was obtained in each 11-deoxycortisol assay system by the use of a minimum amount of the enzyme-labeled antigen at an appropriate dilution of monoclonal anti-11-deoxycortisol antibody (Ka = 2 x 10(10) M-1). The amounts of 11-deoxycortisol needed to displace 50% of the bound label ranged from 5 to 15 pg in the colorimetric methods, and 4-9 pg in the fluorimetric methods.(ABSTRACT TRUNCATED AT 250 WORDS)     

Conversion of a murine monoclonal antibody A13 targeting epidermal growth factor receptor to a human monoclonal antibody by guided selection

Epidermal growth factor receptor (EGFR) is an attractive target for tumor therapy because it is overexpressed in the majority of solid tumors and the increase in receptor expression levels has been linked with a poor clinical prognosis. Also it is well established that blocking the interaction of EGFR and the growth factors could lead to the arrest of tumor growth and possibly result in tumor cell death. A13 is a murine monoclonal antibody (mAb) that specifically binds to various sets of EGFR-expressing tumor cells and inhibits EGF-induced EGFR phosphorylation. We isolated human immunoglobulin genes by guided selection based on the mAb A13. Four different human single chain Fvs (scFvs) were isolated from from hybrid scFv libraries containing a human VH repertoire with the VL of mAb A13 and a human VL repertoire with the VH of mAb A13. All the 4 scFvs bound to EGFR-expressing A431 cells. One scFv (SC414) with the highest affinity was converted to IgG1 (ER414). The ER414 exhibited ～17 fold lower affinity compared to the A13 mAb. In addition the ER414 inhibited an EGF-induced tyrosine phosphorylation of EGFR with much lower efficacy compared to the A13 mAb and Cetuximab (Merck KgaA, Germany). We identified that the epitope of A13 mAb is retained in ER414. This approach will provide an efficient way of converting a murine mAb to a human mAb.     

Development of FIA equipped with a chemiluminescence detector using a mixed reagent of luminol and 1,10-phenanthroline.

We developed an FIA system equipped with a chemiluminescence detector using a mixed chemiluminescence reagent of luminol and 1,10-phenanthroline for the detection of metal ions and metal complexes. The carrier, mixed chemiluminescence reagent comprising luminol, 1,10-phenanthroline, and cethyltrimethylammonium bromide, and H2O2 solutions were fed by corresponding pumps at a definite flow rate. Sample solutions dissolving hematin, [Co(NH3)4(H2O)2]2(SO4)3, CuSO4, NiCl2, K3[Fe(CN)6], and K4[Fe(CN)6] were analyzed as models by the means of the present FIA system. Solutions of hematin, [Co(NH3)4(H2O)2]2(SO4)3, CuSO4, and NiCl2 were detected as positive peaks, as usual. The order of the catalytic activity of these samples for the present chemiluminescence reaction using the mixed chemiluminescence reagent was [Co(NH3)4(H2O)2]2(SO4)3 > hematin > CuSO4 > NiCl2. On the other hand, sample solutions of K3[Fe(CN)6] and K4[Fe(CN)6] were detected as negative peaks and were determined over the ranges of 1 x 10(-8) - 1 x 10(-6) M with a detection limit of 1 x 10(-8) M and 2 x 10(-8) - 4 x 10(-6) M with a detection limit of 2 x 10(-8) M, respectively. Their negative peaks were observed reproducibly with a relative standard deviation of 2 - 5%.     

Purification of a human immunoglobulin G1 monoclonal antibody from transgenic tobacco using membrane chromatographic processes

Efficient purification of protein biopharmaceuticals from transgenic plants is a major challenge, primarily due to low target protein expression levels, and high impurity content in the feed streams. These challenges may be addressed by using membrane chromatography. This paper discusses the use of cation-exchange and Protein A affinity-based membrane chromatographic techniques, singly and in combination for the purification of an anti-Pseudomonas aerugenosa O6ad human IgG1 monoclonal antibody from transgenic tobacco. Protein A membrane chromatography on its own was unable to provide a pure product, mainly due to extensive non-specific binding of impurities. Moreover, the Protein A membrane showed severe fouling tendency and generated high back-pressure. With cation-exchange membrane chromatography, minimal membrane fouling and high permeability were observed but high purity could not be achieved using one-step. Therefore, by using a combination of the cation-exchange and Protein A membrane chromatography, in that order, both high purity and recovery were achieved with high permeability. The antibody purification method was first systematically optimized using a simulated feed solution. Anti-P. aeruginosa human IgG1 type monoclonal antibody was then purified from transgenic tobacco juice using this optimized method.     

Radioimmunoassay of circulating schistosome antigen with a radiation-immobilized monoclonal antibody : Preliminary results

A two-site immunoradiometric assay with a mouse monoclonal antibody to a circulating schistosome antigen was comparatively investigated using the monoclonal antibody either absorbed to microtiter plates (reference IRMA) or immobilized by several techniques. Radiation polymerization methods were carried out at Takasaki Radiation Chemistry Research Establishment, Takasaki, Gunma (I. Kaetsu, M. Kumakura), using 2-hydroxyethyl methacrylate monomers and 1 Mrad irradiation. A significant correlation was obtained with the reference IRMA and the assay using radiation polymerization-immobilized antibody (r = 0.94), although non-specific binding to the polymer discs was higher (x 10) than with microtiter plates. Immobilization of the monoclonal antibody onto polypropylene/polyethylene copolymer films grafted with methacrylic acid irradiated at 0.68 Mrads and treated with carbodiimide/N-hydroxysuccinimide, was carried out at the Dept of Bioengineering, University of Washington, Seattle, Washington (A.S. Hoffman, W.R. Gombotz, S. Uenoyama). A significant correlation (r = 0.90) was obtained with the reference IRMA. Non-specific binding was also higher than with microtiter plates (x 6). An important result was the increased shelf life of the immobilized reagent.     

Liposomalization of hydroxyphenyl fluorescein as a reagent for detecting highly reactive oxygen species

It has been shown that lifestyle-related diseases and aging are related to reactive oxygen species (ROS), and many studies have reported on the direct detection of ROS. The topical fluorescence reagent 2,7-dichlorodihydrofluorescein (DCDHF) is used to measure oxidation. However, there are problems regarding its stability, and its similar sensitivity to ROS cannot be easily distinguished. In this study, we used hydroxyphenyl fluorescein (HPF), which is a novel fluorescence probe with high stability against light that undergoes specific reactions with highly ROS (hROS). We examined the specificity for hROS of HPF solution and liposomal HPF in different reactions. HPF containing high cholesterol liposomes (HC-H-lipo) maintained its ability to tolerate light scattering energy, dependent on the turbidity of this solution, but DCDHF did not. In the reaction with hydroxyl radicals, the fluorescein concentration in HC-H-lipo was increased compared with that in HPF solution. In contrast, in the reaction with peroxynitrite, HC-H-lipo was inhibited. It was confirmed that HC-H-lipo that reacted specifically with hydroxyl radicals was able to distinguishably detect hydroxyl radicals. It was regarded to be useful as an examination kit. Tissue disorder induced by sodium valproate (SV) was one of the prepared murine disease models. The reactivity ratio of HC-H-lipo with serum to that of HPF solution was markedly different between the normal group (30%) and SV group (70%). In conclusion, HC-H-lipo cannot only simply and directly detect ROS but can also selectively detect ROS type. This nanocarrier is expected to be used as a novel diagnosis method.     

Charge heterogeneity of a therapeutic monoclonal antibody conjugated with a cytotoxic antitumor antibiotic, calicheamicin

A robust and highly reproducible capillary isoelectric focusing (cIEF) method for the evaluation of charge heterogeneity of monoclonal antibody (mAb) pharmaceutical which contains covalently bound antitumor compounds was developed using a combination of commercially available dimethylpolysiloxane-coated capillary and carrier ampholyte. In order to optimize major analytical parameters for robust mobilization, experimental responses from three pI markers were selected. The optimized method gave excellent repeatability and intermediate precision in estimated pI values of charge variants with relative standard deviations (RSDs) of not more than 0.06% and 0.95%, respectively, when using IgG(4) as a model. Furthermore, RSDs of charge variant compositions were less than 5.0%. These results suggest that the proposed method can be a powerful tool for reproducible evaluation of charge variants of both naked mAbs and their conjugates with high resolution, and it is applicable to quality testing and detailed characterization in the pharmaceutical industry. In addition, it should be noticed that the method provided non-linear pH gradient within the tested ranges, from pI 9.50 to 3.78, and the pH gradient caused the inconsistency of estimated pI ranges between cIEF and gel IEF. This result indicates that selecting appropriate pI markers based on the target pI ranges of charge variants for each mAb related pharmaceutical is highly recommended for the precise determination of pI values.     

An immunoradiometric assay for human follicle stimulating hormone using a monoclonal antibody coupled to magnetisable cellulose

A simple immunoradiometric assay for human follicle stimulating hormone (hFSH) was developed using a pair of monoclonal antibodies obtained from commercial sources. The system developed makes use of a capture antibody covalently coupled to magnetisable cellulose, which is a more economical and stable immunosorbent as compared to the other solid phases. The detector antibody is labeled with¹²⁵I using the chloramine-T oxidation method and purified by gel filtration. After initial cross-matching of the capture and detector antibodies, various assay parameters have been optimised. This assay does not show any significant cross reactivity with homologous hormones. A number of serum samples from men and women from reproductive age group was screened and compared with another commercially available kit (r=0.98). Sensitivity of the assay is 1.4 mIU/ml, interassay variation is <5% and intraassay variation around 15%. The assay is reproducible and sensitive enough for regular estimation of serum hFSH and is relatively inexpensive.     

Thin-layer chromatography of urinary 17-oxosteroids using dansylhydrazine as a prelabelling reagent.

This paper describes a modification of a high-performance liquid chromatographic method for measurement of 17-oxosteroids in biological fluids for use with thin-layer chromatography and fluorometric scanning detection. After extraction from urine samples with Separon-C18 microcolumns, free oxosteroids were labelled with dansylhydrazine in acetonitrile-acetic acid and chromatographed on silica gel F-254 plates with the solvent system chloroform-methanol (97:3). Linearity of fluorescence detection (Shimadzu CS-9000 densitometer) was obtained between 30 and 1000 ng.     

Separation of oxidized variants of a monoclonal antibody by anion-exchange

Monoclonal antibodies are subject to a variety of degradation mechanisms, therefore orthogonal techniques are required to demonstrate product quality. In this study, the three individual antibodies comprising a multi-antibody drug product, XOMA 3AB were evaluated by both cation-exchange (CEX) and anion-exchange chromatography (AEX). In contrast to CEX analysis which showed only a single, broad peak for the force-oxidized antibodies, AEX analysis of Ab-A (pI=7.6) revealed two more basic peaks. Ab-B (pI=6.7) bound but exhibited only a single major peak while Ab-C (pI=8.6) flowed through. Peptide mapping LC/MS analysis of the isolated Ab-A fractions demonstrated that the basic peaks resulted from oxidation in a complementary determining region (CDR). Differential scanning calorimetry (DSC) analysis of the oxidized Ab-A species showed a decrease in the Fab melting point for the oxidized species consistent with unfolding of the molecule. Greater/lesser surface exposure of ionic residues resulting from a conformational change provides a likely explanation for the dramatic shift in retention behavior for the Ab-A oxidized variants. Peptide mapping analysis of the Ab-B antibody showed, in contrast to Ab-A, no detectable CDR oxidation. Hence, the lack of separation of oxidized variants in Ab-B can be explained by the absence of CDR oxidation and the associated changes in secondary/tertiary structure which were observed for oxidized Ab-A. In summary, anion-exchange HPLC shows potential as an orthogonal analytical technique for assessing product quality of monoclonal antibody therapeutics. In the case of the XOMA 3AB drug product, two of the antibodies bound and one, Ab-A, exhibited separation of CDR oxidized variants.     

Element of a validation method for MU-B3 monoclonal antibody using an imaging capillary isoelectric focusing system

This paper presents an imaging capillary isoelectric focusing (CIEF) assay for the determination of the identity, stability, and isoform distribution of a murine monoclonal antibody (MU-B3). The experiments were conducted using a Convergent Bioscience iCE280 instrument. The optimum carrier ampholyte composition that gave the best peak separation was found to be 25% Pharmalyte pH 3-10 and 75% Pharmalyte pH 5-8. The antibody gave a highly reproducible CIEF profile with three major peaks having average isoelectric point (pI) values of 6.83, 6.99, and 7.11. Intraday and interday reproducibility of pI values was found to be within RSD of 0.5%. The CIEF profile was also the same, with an alternate column cartridge and alternate batches of methyl cellulose. A plot of peak areas versus MU-B3 concentration was linear (R2 = 0.995) up to a concentration of 0.5 mg/mL in the sample solution. Peak area measurements were reproducible to within 7% RSD. The CIEF profiles of two other antibodies were distinctly different from the profile of MU-B3, showing that the assay is specific. After a sample of MU-B3 was subjected to heat stress by exposure to heat at 55 degrees C for 4 h, its CIEF profile was altered with extra peaks appearing at lower pI values, indicating that the assay could be used to monitor stability. The result of the heat stress experiment was also confirmed with a parallel slab-gel IEF analysis of the antibody sample before and after application of the heat stress. The results of this work suggest that imaging CIEF can be used for product testing under a quality control environment. The assay can be used for pI profiling of proteins and for monitoring structural changes (deamidation, glycosylation, etc.) during the manufacturing process and upon storage.