High-throughput quantitative analysis of plant N-glycan using a DNA sequencer

A Rapid Protocol for Preparing 8-Aminopyrene-1,3,6-Trisulfonate-Labeled Glycans for Capillary Electrophoresis-Based Enzyme Assays

Purified glycan standards are required for glycan arrays, characterizing substrate specificities of glycan-active enzymes, and to serve as retention-time or mobility standards for various separation techniques. This chapter describes a method for the rapid separation, and subsequent desalting, of glycans labeled with the highly fluorescent fluorophore 8-aminopyrene-1,3,6-trisulfonate (APTS). By using fluorophore-assisted carbohydrate electrophoresis (FACE) on polyacrylamide gels, a technique amenable to equipment readily available in most molecular biology laboratories, many APTS-labeled glycans can be simultaneously resolved. Excising specific gel bands containing the desired APTS-labeled glycans, followed by glycan elution from the gel by simple diffusion and subsequent solid-phase extraction (SPE)-based desalting, affords a single glycan species free of excess labeling reagents and buffer components. The described protocol also offers a simple, rapid method for the simultaneous removal of excess APTS and unlabeled glycan material from reaction mixtures. This chapter describes a FACE/SPE procedure ideal for preparing glycans for capillary electrophoresis (CE)-based enzyme assays, as well as for the purification of rare, commercially unavailable glycans from tissue culture samples.

Immunotherapeutic effects of recombinant colorectal cancer antigen produced in tomato fruits

The production of pharmacological vaccines in plants has been an important goal in the field of plant biotechnology. GA733-2, the protein that is also known as colorectal carcinoma (CRC)-associated antigen, is a strong candidate to produce a colorectal cancer vaccine. Tomato is the one of the major targets for production of an edible vaccine, as tomato is a fruit consumed in fresh form. It also contains high content of vitamins that aid activation of immune response. In order to develop an edible colorectal cancer vaccine, the transgene rGA733-Fc that encodes a fusion protein of GA733-2, the fragment crystallizable (Fc) domain, and the ER retention motif (rGA733-Fc) was introduced into tomato plants (Solanumlycopersicum cv. Micro-Tom). The transgenic plants producing rGA733-Fc (rGA733-Fc^OX) protein were screened based on stable integration of transgene expression cassette and expression level of rGA733-Fc protein. Further glycosylation pattern analysis revealed that plant derived rGA733-Fc protein contains an oligomannose glycan structure, which is a typical glycosylation pattern found on ER-processing proteins. The red fruits of rGA733-Fc^OX transgenic tomato plants containing approximately 270 ng/g FW of rGA733-Fc protein were orally administered to C57BL/6 mice. Oral administration of tomato fruits of the rGA733-Fc expressing transgenic plants delayed colorectal cancer growth and stimulated immune responses compared to oral administration of tomato fruits of the h-Fc expressing transgenic plants in the C57BL/6J mice. This is the first study showing the possibility of producing an edible colorectal cancer vaccine using tomato plants. This research would be helpful for development of plant-derived cancer edible vaccines.

Unidentified N-glycans by N-glycosidase A were Identified by Nglycosidase F under Denaturing Conditions in Plant Glycoprotein

Background:

The identification of N-glycans in plant glycoproteins or plant-made pharmaceuticals is essential for understanding their structure, function, properties, immunogenicity, and allergenicity (induced by plant-specific core-fucosylation or xylosylation) in the applications of plant food, agriculture, and plant biotechnology. N-glycosidase A is widely used to release the N-glycans of plant glycoproteins because the core-fucosylated N-glycans of plant glycoproteins are hydrolyzed by N-glycosidase A but not by N-glycosidase F. However, the efficiency of N-glycosidase A activity on plant glycoproteins remains unclear.

Objective:

To elucidate the efficient use of N-glycosidases to identify and quantify the N-glycans of plant glycoproteins, the identification of released N-glycans by N-glycosidase F and their relative quantities with a focus on unidentified N-glycans by N-glycosidase A in plant glycoproteins, Phaseolus vulgaris lectin (PHA) and horseradish peroxidase (HRP), were investigated.

Methods:

Liquid chromatography–tandem mass spectrometry was used to analyze and compare the N-glycans of PHA and HRP treated with either N-glycosidase A or F under denaturing conditions. The relative quantities (%) of each N-glycan (>0.1%) to the total N-glycans (100%) were determined.

Results:

N-glycosidase A and F released 9 identical N-glycans of PHA, but 2 additional core-fucosylated N-glycans were released by only N-glycosidase A, as expected. By contrast, in HRP, 8 N-glycans comprising 6 core-fucosylated N-glycans, 1 xylosylated N-glycan, and 1 mannosylated N-glycan were released by N-glycosidase A. Moreover, 8 unexpected N-glycans comprising 1 core-fucosylated N-glycan, 4 xylosylated N-glycans, and 3 mannosylated N-glycans were released by N-glycosidase F. Of these, 3 xylosylated and 2 mannosylated N-glycans were released by only N-glycansodase F.

Conclusion:

These results demonstrated that N-glycosidase A alone is insufficient to release the N-glycans of all plant glycoproteins, suggesting that to identify and quantify the released N-glycans of the plant glycoprotein HRP, both N-glycosidase A and F treatments are required.

A Plant-Derived Antigen-Antibody Complex Induces Anti-Cancer Immune Responses by Forming a Large Quaternary Structure

The antigen–antibody complex (AAC) has novel functions for immunomodulation, encouraging the application of diverse quaternary protein structures for vaccination. In this study, GA733 antigen and anti-GA733 antibody proteins were both co-expressed to obtain the AAC protein structures in a F1 plant obtained by crossing the plants expressing each protein. In F1 plant, the antigen and antibody assembled to form a large quaternary circular ACC structure (~30 nm). The large quaternary protein structures induced immune response to produce anticancer immunoglobulins G (IgGs) that are specific to the corresponding antigens in mouse. The serum containing the anticancer IgGs inhibited the human colorectal cancer cell growth in the xenograft nude mouse. Taken together, antigens and antibodies can be assembled to form AAC protein structures in plants. Plant crossing represents an alternative strategy for the formation of AAC vaccines that efficiently increases anticancer antibody production.

Screening and Selection of Production Strains: Secretory Protein Expression and Analysis in Hansenula polymorpha

The thermotolerant methylotrophic yeast Hansenula polymorpha has been used as a host for the high-level production of recombinant proteins from industrial enzymes to therapeutic proteins. Despite favorable characteristics of the H. polymorpha-based platform for application to heterologous gene expression, several problems and limitations, such as over-glycosylation and proteolytic degradation, can be encountered in the development of production strains for secretory proteins. Here, H. polymorpha genetic tools and host strains, developed for authentic processing and modification of secretory recombinant proteins, are introduced with the analytical protocols.

Multiplexing N-glycan analysis by DNA analyzer

Analysis of N-glycan structures has been gaining attentions over the years due to their critical importance to biopharma-based applications and growing roles in biological research. Glycan profiling is also critical to the development of biosimilar drugs. The detailed characterization of N-glycosylation is mandatory because it is a nontemplate driven process and that significantly influences critical properties such as bio-safety and bio-activity. The ability to comprehensively characterize highly complex mixtures of N-glycans has been analytically challenging and stimulating because of the difficulties in both the structure complexity and time-consuming sample pretreatment procedures. CE-LIF is one of the typical techniques for N-glycan analysis due to its high separation efficiency. In this paper, a 16-capillary DNA analyzer was coupled with a magnetic bead glycan purification method to accelerate the sample preparation procedure and therefore increase N-glycan assay throughput. Routinely, the labeling dye used for CE-LIF is 8-aminopyrene-1,3,6-trisulfonic acid, while the typical identification method involves matching migration times with database entries. Two new fluorescent dyes were used to either cross-validate and increase the glycan identification precision or simplify sample preparation steps. Exoglycosidase studies were carried out using neuramididase, galactosidase, and fucosidase to confirm the results of three dye cross-validation. The optimized method combines the parallel separation capacity of multiple-capillary separation with three labeling dyes, magnetic bead assisted preparation, and exoglycosidase treatment to allow rapid and accurate analysis of N-glycans. These new methods provided enough useful structural information to permit N-glycan structure elucidation with only one sample injection.

Current landscape of protein glycosylation analysis and recent progress toward a novel paradigm of glycoscience research

This review covers the basics and some applications of methodologies for the analysis of glycoprotein glycans. Analytical techniques used for glycoprotein glycans, including liquid chromatography (LC), capillary electrophoresis (CE), mass spectrometry (MS), and high-throughput analytical methods based on microfluidics, were described to supply the essentials about biopharmaceutical and biomarker glycoproteins. We will also describe the MS analysis of glycoproteins and glycopeptides as well as the chemical and enzymatic releasing methods of glycans from glycoproteins and the chemical reactions used for the derivatization of glycans. We hope the techniques have accommodated most of the requests from glycoproteomics researchers.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update for 2009-2010

This review is the sixth update of the original article published in 1999 on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2010. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, arrays and fragmentation are covered in the first part of the review and applications to various structural typed constitutes the remainder. The main groups of compound that are discussed in this section are oligo and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals. Many of these applications are presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions and applications to chemical synthesis.

High-throughput glycosylation analysis of therapeutic immunoglobulin G by capillary gel electrophoresis using a DNA analyzer

The Fc glycosylation of therapeutic antibodies is crucial for their effector functions and their behavior in pharmacokinetics and pharmacodynamics. To monitor the Fc glycosylation in bioprocess development and characterization,high-throughput techniques for glycosylation analysis are needed. Here, we describe the development of a largely automated high-throughput glycosylation profiling method with multiplexing capillary-gel-electrophoresis (CGE) with laser induced fluorescence (LIF) detection using a DNA analyzer. After PNGaseF digestion, the released glycans were labeled with 9-aminopyrene-1,3,6-trisulfonic acid (APTS) in 96-well plates, which was followed by the simultaneous analysis of up to 48 samples. The peak assignment was conducted by HILIC-UPLC-MS/MS of the APTS-labeled glycans combined with peak fractionation and subsequent CGE-LIF analysis of the MS-characterized fractions. Quantitative data evaluation of the various IgG glycans was performed automatically using an in-house developed software solution. The excellent method accuracy and repeatability of the test system was verified by comparison with two UPLC-based methods for glycan analysis. Finally, the practical value of the developed method was demonstrated by analyzing the antibody glycosylation profiles from fermentation broths after small scale protein A purification.

Molecular characterization of acidic peptide:N-glycanase from the dimorphic yeast Yarrowia lipolytica

Peptide:N-glycanase (PNGase) A is used preferentially to cleave the glycans from plant and insect glycopeptides. Although many putative PNGase A homologous genes have been found in the plant and fungus kingdoms through sequence similarity analyses, only several PNGases from plants and one from a filamentous fungus have been characterized. In this study, we identified and characterized a PNGase A-like enzyme, PNGase Yl, in the dimorphic yeast Yarrowia lipolytica. The corresponding gene was cloned and recombinantly expressed in Pichia pastoris. The purified enzyme cleaved glycans from glycopeptides with the maximum activity at pH 5. No metal ions were required for full activity, and rather it was repressed by three metal ions (Fe(3+), Cu(2+) and Zn(2+)). Using glycopeptide substrates, PNGase Yl was shown to release various types of N-glycans including high-mannose and complex-type glycans as well as glycans containing core-linked α(1,3)-fucose that are frequently found in plants and insects. Moreover, in comparison with PNGase A, PNGase Yl was able to cleave with higher efficiency the glycans from some denatured glycoproteins. Taken together, our results suggest that PNGase Yl, the first biochemically characterized yeast PNGase A homologue, can be developed through protein engineering as a useful deglycosylation tool for N-glycosylation study.

Capillary electrophoresis/mass spectrometry of APTS-labeled glycans for the identification of unknown glycan species in capillary electrophoresis/laser-induced fluorescence systems

The examination of protein glycosylation is of high importance, especially in the (bio)pharmaceutical sector. The analysis of protein glycosylation is conducted routinely in high performance by capillary electrophoresis with laser-induced fluorescence (CE/LIF) using 8-aminopyrene-1,3,6-trisulfonic acid (APTS)-labeled glycans. In this work we present an optimized capillary electrophoresis/time-of-flight mass spectrometry (CE/TOF-MS) methodology for these labeled glycans, which combines the high separation performance of CE with the high resolution, accuracy, and speed of TOF-MS for eased glycan identification. The system based on an acidic background electrolyte (BGE) provides a migration direction analogue to routine CE/LIF systems. Different BGE compositions, capillary dimensions, coatings, and instrumental parameters were tested to optimize the system with respect to separation efficiency and robustness. Subsequently, the CE/MS method optimized for acidic conditions was compared to an alkaline CE/MS method. Further, the mobilities of six APTS-labeled complex-type N-glycans were compared for both CE/MS methods and two standard CE/LIF approaches. For the acidic and alkaline BGE systems, the mobilities of sialylated glycans were shifted relative to nonsialylated glycans in comparison to common CE/LIF systems. However, in this study a straightforward unequivocal peak assignment was achieved for all unknown glycans in a medium complex glycan mixture from a fusion protein.

Cell surface-specific N-glycan profiling in breast cancer

Aberrant changes in specific glycans have been shown to be associated with immunosurveillance, tumorigenesis, tumor progression and metastasis. In this study, the N-glycan profiling of membrane proteins from human breast cancer cell lines and tissues was detected using modified DNA sequencer-assisted fluorophore-assisted carbohydrate electrophoresis (DSA-FACE). The N-glycan profiles of membrane proteins were analyzed from 7 breast cancer cell lines and MCF 10A, as well as from 100 pairs of breast cancer and corresponding adjacent tissues. The results showed that, compared with the matched adjacent normal tissue samples, two biantennary N-glycans (NA2 and NA2FB) were significantly decreased (p <0.0001) in the breast cancer tissue samples, while the triantennary glycan (NA3FB) and a high-mannose glycan (M8) were dramatically increased (p = 0.001 and p <0.0001, respectively). Moreover, the alterations in these specific N-glycans occurred through the oncogenesis and progression of breast cancer. These results suggested that the modified method based on DSA-FACE is a high-throughput detection technology that is suited for analyzing cell surface N-glycans. These cell surface-specific N-glycans may be helpful in recognizing the mechanisms of tumor cell immunologic escape and could be potential targets for new breast cancer drugs.

Intracellular reprogramming of expression, glycosylation, and function of a plant-derived antiviral therapeutic monoclonal antibody

Plant genetic engineering, which has led to the production of plant-derived monoclonal antibodies (mAb(P)s), provides a safe and economically effective alternative to conventional antibody expression methods. In this study, the expression levels and biological properties of the anti-rabies virus mAb(P) SO57 with or without an endoplasmic reticulum (ER)-retention peptide signal (Lys-Asp-Glu-Leu; KDEL) in transgenic tobacco plants (Nicotiana tabacum) were analyzed. The expression levels of mAb(P) SO57 with KDEL (mAb(P)K) were significantly higher than those of mAb(P) SO57 without KDEL (mAb(P)) regardless of the transcription level. The Fc domains of both purified mAb(P) and mAb(P)K and hybridoma-derived mAb (mAb(H)) had similar levels of binding activity to the FcγRI receptor (CD64). The mAb(P)K had glycan profiles of both oligomannose (OM) type (91.7%) and Golgi type (8.3%), whereas the mAb(P) had mainly Golgi type glycans (96.8%) similar to those seen with mAb(H). Confocal analysis showed that the mAb(P)K was co-localized to ER-tracker signal and cellular areas surrounding the nucleus indicating accumulation of the mAb(P) with KDEL in the ER. Both mAb(P) and mAb(P)K disappeared with similar trends to mAb(H) in BALB/c mice. In addition, mAb(P)K was as effective as mAb(H) at neutralizing the activity of the rabies virus CVS-11. These results suggest that the ER localization of the recombinant mAb(P) by KDEL reprograms OM glycosylation and enhances the production of the functional antivirus therapeutic antibody in the plant.

Development and application of a high throughput carbohydrate profiling technique for analyzing plant cell wall polysaccharides and carbohydrate active enzymes

BACKGROUND

Plant cell wall polysaccharide composition varies substantially between species, organs and genotypes. Knowledge of the structure and composition of these polysaccharides, accompanied by a suite of well characterised glycosyl hydrolases will be important for the success of lignocellulosic biofuels. Current methods used to characterise enzymatically released plant oligosaccharides are relatively slow.

RESULTS

A method and software was developed allowing the use of a DNA sequencer to profile oligosaccharides derived from plant cell wall polysaccharides (DNA sequencer-Assisted Saccharide analysis in High throughput, DASH). An ABI 3730xl, which can analyse 96 samples simultaneously by capillary electrophoresis, was used to separate fluorophore derivatised reducing mono- and oligo-saccharides from plant cell walls. Using electrophoresis mobility markers, oligosaccharide mobilities were standardised between experiments to enable reproducible oligosaccharide identification. These mobility markers can be flexibly designed to span the mobilities of oligosaccharides under investigation, and they have a fluorescence emission that is distinct from that of the saccharide labelling. Methods for relative and absolute quantitation of oligosaccharides are described. Analysis of a large number of samples is facilitated by the DASHboard software which was developed in parallel. Use of this method was exemplified by comparing xylan structure and content in Arabidopsis thaliana mutants affected in xylan synthesis. The product profiles of specific xylanases were also compared in order to identify enzymes with unusual oligosaccharide products.

CONCLUSIONS

The DASH method and DASHboard software can be used to carry out large-scale analyses of the compositional variation of plant cell walls and biomass, to compare plants with mutations in plant cell wall synthesis pathways, and to characterise novel carbohydrate active enzymes.

Expression of GA733-Fc fusion protein as a vaccine candidate for colorectal cancer in transgenic plants

The tumor-associated antigen GA733 is a cell-surface glycoprotein highly expressed in colorectal carcinomas. In this study, 3 recombinant genes were constructed as follows: GA733 tagged to the ER retention sequence KDEL (GA733K), GA733 fused to the immunoglobulin Fc fragment (GA733-Fc), and GA733-Fc fused to the ER retention sequence (GA733-FcK). Agrobacterium-mediated transformation was used to generate transgenic plants expressing recombinant genes. The presence of transgenes was confirmed by genomic PCR. Western blot, confocal immunofluorescence, and sandwich ELISA showed the expression of recombinant proteins. The stability, flexibility, and bioactivity of recombinant proteins were analyzed and demonstrated through N-glycosylation analysis, animal trials, and sera ELISA. Our results suggest that the KDEL retained proteins in ER with oligomannose glycan structure and enhanced protein accumulation level. The sera of mice immunized with GA733-FcK purified from plants contained immunoglobulins which were at least as efficient as the mammalian-derived GA733-Fc at recognizing human colorectal cancer cell lines. Thus, a plant system can be used to express the KDEL fusion protein with oligomannose glycosylation, and this protein induces an immune response which is comparable to non-KDEL-tagged, mammalian-derived proteins.

High-throughput quantitative analysis of total N-glycans by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Accurate and reproducible quantification of glycans from protein drugs has become an important issue for quality control of therapeutic proteins in biopharmaceutical and biotechnology industries. Mass spectrometry is a promising tool for both qualitative and quantitative analysis of glycans owing to mass accuracy, efficiency, and reproducibility, but it has been of limited success in quantitative analysis for sialylated glycans in a high-throughput manner. Here, we present a solid-phase permethylation-based total N-glycan quantitative method that includes N-glycan releasing, purification, and derivatization on a 96-well plate platform. The solid-phase neutralization enabled us to perform reliable absolute quantification of the acidic N-glycans as well as neutral N-glycans from model glycoproteins (i.e., chicken ovalbumin and porcine thyroglobulin) by only using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Furthermore, low-abundance sialylated N-glycans from human serum prostate specific antigen (PSA), an extremely valuable prostate cancer marker, were initially quantified, and their chemical compositions were proposed. Taken together, these results demonstrate that our all-inclusive glycan preparation method based on a 96-well plate platform may contribute to the precise and reliable qualitative and quantitative analysis of glycans.

Development and qualification of an antibody rapid deglycosylation method

N-linked glycosylation can influence the biological activity and safety of an antibody as well as be a measure of the consistency of the production process. The released N-glycans is an important part of the development of a therapeutic antibody. The traditional method for N-glycan analysis requires complex and laborious sample preparation and lengthy analysis time. Two preparation steps with limited control are removal of the antibody backbone by ice-cold ethanol precipitation and water removal before 2-AB fluorescent dye labeling. Simplification of the sample preparation and better control of key steps that allows for the characterization/quantitation of glycans during all stages of development of a therapeutic antibody is desired. Recently Prozyme introduced a rapid deglycosylation kit and a rapid tagging kit that address some of these issues. The deglycosylation kit immobilizes the antibody on a membrane, thereby eliminating the precipitation step. An instant fluorescent tag kit eliminates the water removal before the 2-AB labeling step. In addition use of a new chromatography column can improve the glycan resolution and shorten the analysis time. The evaluation and qualification of the Rapid Deglycosylation Kit (RDK) and instant 2-AB tagging with the improved chromatography are highlighted.

Robust and high-throughput sample preparation for (semi-)quantitative analysis of N-glycosylation profiles from plasma samples

High-throughput quantitative or semiquantitative glycoanalytical procedures are urgently required for biomarker discovery and quality control of glycoprotein pharmaceuticals. We describe here a strategy for high-throughput sample preparation for the relative quantitation of N-glycan patterns of human plasma glycoproteins. To this end, efficient glycan release is combined with a robust labeling step. Sample purification is achieved using solid phase extraction with a hydrophilic interaction chromatography stationary phase, which allows the separation of the labeled glycans from excess label, proteins, and matrix constituents such as salts and lipids. We show that the obtained labeled glycan sample solution is directly compatible with a number of downstream analytical techniques such as hydrophilic interaction and reverse-phase chromatography, capillary electrophoresis, and matrix-assisted laser desorption ionization mass spectrometry. High throughput is achieved by conducting all sample preparation steps in the 96-well format. The robustness and repeatability of the sample preparation strategy is evaluated.

Improved sample preparation for CE-LIF analysis of plant N-glycans

In view of glycomics studies in plants, it is important to have sensitive tools that allow one to analyze and characterize the N-glycans present on plant proteins in different species. Earlier methods combined plant-based sample preparations with CE-LIF N-glycan analysis but suffered from background contaminations, often resulting in non-reproducible results. This publication describes a reproducible and sensitive protocol for the preparation and analysis of plant N-glycans, based on a combination of the 'in-gel release method' and N-glycan analysis on a multicapillary DNA sequencer. Our protocol makes it possible to analyze plant N-glycans starting from low amounts of plant material with highly reproducible results. The developed protocol was validated for different plant species and plant cells.

Essential role of YlMPO1, a novel Yarrowia lipolytica homologue of Saccharomyces cerevisiae MNN4, in mannosylphosphorylation of N- and O-linked glycans

Mannosylphosphorylation of N- and O-glycans, which confers negative charges on the surfaces of cells, requires the functions of both MNN4 and MNN6 in Saccharomyces cerevisiae. To identify genes relevant to mannosylphosphorylation in the dimorphic yeast Yarrowia lipolytica, the molecular functions of five Y. lipolytica genes showing significant sequence homology with S. cerevisiae MNN4 and MNN6 were investigated. A set of mutant strains in which Y. lipolytica MNN4 and MNN6 homologues were deleted underwent glycan structure analysis. In contrast to S. cerevisiae MNN4 (ScMNN4), the Y. lipolytica MNN4 homologue, MPO1 (YlMPO1), encodes a protein that lacks the long KKKKEEEE repeat domain at its C terminus. Moreover, just a single disruption of YlMPO1 resulted in complete disappearance of the acidic sugar moiety in both the N- and O-linked glycan profiles. In contrast, even quadruple disruption of all ScMNN6 homologues, designated YlKTR1, YlKTR2, YlKTR3, and YlKTR4, resulted in no apparent reduction in acidic sugar moieties. These findings strongly indicate that YlMpo1p performs a significant role in mannosylphosphorylation in Y. lipolytica with no involvement of the Mnn6p homologues. Mutant strains harboring the YlMPO1 gene disruption may serve as useful platforms for engineering Y. lipolytica glycosylation pathways for humanized glycans without any yeast-specific acidic modifications.

Characterization of N-glycan structures and biofunction of anti-colorectal cancer monoclonal antibody CO17-1A produced in baculovirus-insect cell expression system

Advantages of the baculovirus insect cell expression system for production of recombinant proteins include high capacity, flexibility, and glycosylation capability. In this study, this expression system was exploited to produce anti-cancer monoclonal antibody (mAb) CO17-1A, which recognizes the antigen GA733. The heavy chain (HC) and light chain (LC) genes of mAb CO17-1A were cloned under the control of P(10) and Polyhedrin promoters in the pFastBac dual vector, respectively. Gene expression cassettes carrying the HC and LC genes were transposed into a bacmid in Escherichia coli (DH10Bac). The transposed bacmid was transfected to Sf9 insect cells to generate baculovirus expressing mAb CO17-1A. Confocal immunofluorescence and Western blot analyses confirmed expression of mAb CO17-1A in baculovirus-infected insect cells. The optimum conditions for mAb expression were evaluated at 24, 48, and 72 h after the virus infection at an optimum virus multiplicity of infection of 1. Expression of mAb CO17-1A in insect cells significantly increased at 72 h after infection. HPLC analysis of glycosylation status revealed that the insect-derived mAb (mAb(I)) CO17-1A had insect specific glycan structures. ELISA showed that the purified mAb(I) from cell culture supernatant specifically bound to SW948 human colorectal cancer cells. Fluorescence-activated cell sorting analysis showed that, although mAb(I) had insect specific glycan structures that differed from their mammalian counterparts, mAb(I) similarly interacted with CD64 (FcgammaRI) and Fc of IgG, compared to the interactions of mammalian-derived mAb. These results suggest that the baculovirus insect cell expression system is able to express, assemble, and secrete biofunctional full size mAb.

Rapid and high-throughput analysis of N-glycans from ovarian cancer serum using a 96-well plate platform

We present a rapid and high-throughput human serum N-glycan preparation technology using 96-well plate-based procedures. The released N-glycans from polyvinylidene fluoride (PVDF) membrane filter plate are subsequently loaded to porous graphitic carbon (PGC) containing a 96-well plate to remove salts and other contaminants without sacrificing accuracy or reproducibility. This robust glycan preparation technology is applied to ovarian cancer diagnosis using 5 microl of patient serum.