This work was supported in part by a Research Career Development Award from the Israel Cancer Research Fund, a grant from the Israeli National Nanotechnology Initiative and the Helmsley Charitable Trust for a Focal Technology Area on Nanomedicines for Personalized Theranostics (V.P-K), and National Institutes of Health grant R01GM076360 (to X.C.).

<ol>
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H., Diaz, S., Varki, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanism+of+uptake+and+incorporation+of+the+non-human+sialic+acid+N-glycolylneuraminic+acid+into+human+cells.">Mechanism of uptake and incorporation of the non-human sialic acid N-glycolylneuraminic acid into human cells.</a> J Biol Chem. 280 (6), 4228-4237 (2005).</li><li>Padler-Karavani, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diversity+in+specificity,+abundance,+and+composition+of+anti-Neu5Gc+antibodies+in+normal+humans:+potential+implications+for+disease.">Diversity in specificity, abundance, and composition of anti-Neu5Gc antibodies in normal humans: potential implications for disease.</a> Glycobiology. 18 (10), 818-830 (2008).</li><li>Padler-Karavani, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+xeno-autoantibodies+against+a+non-human+sialic+acid+serve+as+novel+serum+biomarkers+and+immunotherapeutics+in+cancer.">Human xeno-autoantibodies against a non-human sialic acid serve as novel serum biomarkers and immunotherapeutics in cancer.</a> Cancer Res. 71 (9), 3352-3363 (2011).</li><li>Cao, H., Chen, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=General+consideration+on+sialic+acid+chemistry.">General consideration on sialic acid chemistry.</a> Methods Mol Biol. 808, 31-56 (2012).</li><li>Deng, L., Chen, X., Varki, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exploration+of+sialic+Acid+diversity+and+biology+using+sialoglycan+microarrays.">Exploration of sialic Acid diversity and biology using sialoglycan microarrays.</a> Biopolymers. 99 (10), 650-665 (2013).</li><li>Liang, C. H., Hsu, C. H., Wu, C. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sialoside+Arrays:+New+Synthetic+Strategies+and+Applications.">Sialoside Arrays: New Synthetic Strategies and Applications.</a> Top Curr Chem. 367, 125-149 (2015).</li><li>Song, X., Heimburg-Molinaro, J., Smith, D. F., Cummings, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glycan+microarrays+of+fluorescently-tagged+natural+glycans.">Glycan microarrays of fluorescently-tagged natural glycans.</a> Glycoconj J. 32 (7), 465-473 (2015).</li><li>Muthana, S. M., Gildersleeve, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glycan+microarrays:+powerful+tools+for+biomarker+discovery.">Glycan microarrays: powerful tools for biomarker discovery.</a> Cancer Biomark. 14 (1), 29-41 (2014).</li><li>Rillahan, C. D., Paulson, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glycan+microarrays+for+decoding+the+glycome.">Glycan microarrays for decoding the glycome.</a> Annu Rev Biochem. 80, 797-823 (2011).</li><li>Heimburg-Molinaro, J., Song, X., Smith, D. F., Cummings, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+and+analysis+of+glycan+microarrays.">Preparation and analysis of glycan microarrays.</a> Curr Protoc Protein Sci. 12 (10), (2011).</li><li>Park, S., Gildersleeve, J. C., Blixt, O., Shin, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carbohydrate+microarrays.">Carbohydrate microarrays.</a> Chem Soc Rev. 42 (10), 4310-4326 (2013).</li><li>Struwe, W. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+minimum+information+required+for+a+glycomics+experiment+(MIRAGE)+project:+sample+preparation+guidelines+for+reliable+reporting+of+glycomics+datasets.">The minimum information required for a glycomics experiment (MIRAGE) project: sample preparation guidelines for reliable reporting of glycomics datasets.</a> Glycobiology. 26 (9), 907-910 (2016).</li><li>Liu, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+minimum+information+required+for+a+glycomics+experiment+(MIRAGE)+project:+improving+the+standards+for+reporting+glycan+microarray-based+data.">The minimum information required for a glycomics experiment (MIRAGE) project: improving the standards for reporting glycan microarray-based data.</a> Glycobiology. , (2016).</li><li>Hara, S., Yamaguchi, M., Takemori, Y., Furuhata, K., Ogura, H., Nakamura, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+mono-O-acetylated+N-acetylneuraminic+acids+in+human+and+rat+sera+by+fluorometric+high-performance+liquid+chromatography.">Determination of mono-O-acetylated N-acetylneuraminic acids in human and rat sera by fluorometric high-performance liquid chromatography.</a> Anal Biochem. 179 (1), 162-166 (1989).</li><li>Padler-Karavani, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cross-comparison+of+protein+recognition+of+sialic+acid+diversity+on+two+novel+sialoglycan+microarrays.">Cross-comparison of protein recognition of sialic acid diversity on two novel sialoglycan microarrays.</a> J Biol Chem. 287 (27), 22593-22608 (2012).</li><li>Padler-Karavani, V., Varki, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Potential+impact+of+the+non-human+sialic+acid+N-glycolylneuraminic+acid+on+transplant+rejection+risk.">Potential impact of the non-human sialic acid N-glycolylneuraminic acid on transplant rejection risk.</a> Xenotransplantation. 18 (1), 1-5 (2011).</li><li>Samraj, A. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+red+meat-derived+glycan+promotes+inflammation+and+cancer+progression.">A red meat-derived glycan promotes inflammation and cancer progression.</a> Proc Natl Acad Sci USA. 112 (2), 542-547 (2015).</li><li>Pearce, O. M., L&#228;ubli, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sialic+acids+in+cancer+biology+and+immunity.">Sialic acids in cancer biology and immunity.</a> Glycobiology. 26 (2), 111-128 (2016).</li><li>Alisson-Silva, F., Kawanishi, K., Varki, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+risk+of+diseases+associated+with+red+meat+intake:+Analysis+of+current+theories+and+proposed+role+for+metabolic+incorporation+of+a+non-human+sialic+acid.">Human risk of diseases associated with red meat intake: Analysis of current theories and proposed role for metabolic incorporation of a non-human sialic acid.</a> Mol Aspects Med. 51, 16-30 (2016).</li><li>Pearce, O. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inverse+hormesis+of+cancer+growth+mediated+by+narrow+ranges+of+tumor-directed+antibodies.">Inverse hormesis of cancer growth mediated by narrow ranges of tumor-directed antibodies.</a> Proc Natl Acad Sci USA. 111 (16), 5998-6003 (2014).</li><li>Pham, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence+for+a+novel+human-specific+xeno-auto-antibody+response+against+vascular+endothelium.">Evidence for a novel human-specific xeno-auto-antibody response against vascular endothelium.</a> Blood. 114 (25), 5225-5235 (2009).</li><li>Reuven, E. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+immunogenic+Neu5Gc+in+bioprosthetic+heart+valves.">Characterization of immunogenic Neu5Gc in bioprosthetic heart valves.</a> Xenotransplantation. 23 (5), 381-392 (2016).</li><li>Ghaderi, D., Taylor, R. E., Padler-Karavani, V., Diaz, S., Varki, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Implications+of+the+presence+of+N-glycolylneuraminic+acid+in+recombinant+therapeutic+glycoproteins.">Implications of the presence of N-glycolylneuraminic acid in recombinant therapeutic glycoproteins.</a> Nat Biotechnol. 28 (8), 863-867 (2010).</li></ol>

The authors have nothing to disclose.

A successful glycan microarray fabrication requires careful planning and includes several important steps in the protocol. These include: (1) planning the block and plate layouts that define all subsequent parameters (e.g., distances, spacing, amount of samples, and printing); (2) cleaning the pins and ensuring pin integrity, which is critical for controlling spot homogeneity; (3) maintaining high humidity during printing, critical to avoiding sample evaporation during long print runs, which could compromise spo...

Sias are acidic sugars covering glycan chains on cell-surface glycoproteins and glycolipids in vertebrates. Sia expression is modified in cancer cells1 and correlates with progression and/or metastasis2,3. Two of the major Sia forms in mammals are Neu5Ac and its hydroxylated form, Neu5Gc2. Humans cannot synthesize Neu5Gc due to a specific inactivation of the gene encoding the CMAH enzyme . This non-human Sia metabolically incorporates into human cells as &#34;self,&#34; originating from dietary Neu5Gc-rich foods (e.g., red meat)4,5. Neu5Gc is present at low levels on the cell surfaces of human epithelia and endothelia, but it especially accumulates in carcinomas. Neu5Gc is recognized as foreign by the human humoral immune system2,6. The antigenic complexity of Neu5Gc-glycans may arise at multiple levels, including Neu5Gc modification, linkage, underlying glycans and scaffolds, and their density, all reflected by the complexity of anti-Neu5Gc antibody response in humans6. Some of these antibodies serve as carcinoma biomarkers and potential immunotherapeutics7. The advent of the chemoenzymatic synthesis of different sialoglycans8 paved the way for the more in-depth analysis of such antibodies, facilitated by the use of glycan microarray technology9,10. Thus, with the facilitated preparation and manipulation of large libraries of natural and synthetic carbohydrates, glycan microarrays have become a powerful high-throughput technology for investigating the interactions of carbohydrates with a myriad of biomolecules10,11,12,13. In an array format, minimal amounts of materials are used, and this multivalent display of biologically relevant glycans allows for the investigation of thousands of binding interactions in a single experiment. Importantly, this technology can also be applied to biomarker discovery and to monitoring immune responses in various samples7,12.
Successful glycan microarray fabrication requires the consideration of three important aspects: the printer robot type, glycan conjugation chemistry, and detection optics. As to the printing instrument consideration, two techniques are available: contact and non-contact printers. In contact printing, 1-48 steel pins are dipped into a multi-well source plate containing glycan solution and are spotted on functionalized glass slides by directly contacting the glass slide surface. The solution amount delivered to the slide is a function of the lingering duration on the slide surface. Usually, the samples are first pre-spotted on a glass block (to reach homogenous spots) before they are printed on the slide surface. In non-contact printers (e.g., the piezo-electronic printer), the glycans are printed from a glass capillary using controlled electric signals. The electric signal can be finely calibrated to achieve more precise printing relative to contact printing. The size and morphology of the spots are also relatively more homogeneous. An additional advantage is the recycling of the sample back to the source plate after printing. Nevertheless, the major disadvantage of piezo-electronic printers is the printing tip limitation (4 or 8), resulting in a very long printing duration, which requires special attention to slide stability, temperature, humidity, and sample evaporation. The non-contact inkjet printer requires larger sample volumes14.
In contrast to the limited available options for printing methods, glycan conjugation chemistry is a more complex consideration, with many options to choose from. Selected immobilization chemistry must account for both the active groups on the glycans and the slide surface reactivity. The glycans to be immobilized onto a specific microarray surface, either synthetically synthesized or naturally isolated, all require an identical reactive group. In addition, the glycans need to be pure and homogenous. On the other hand, the immobilization surface and chemistry should provide reproducibility and reliable attachment density. Multiple immobilization methods have been developed with either covalent or non-covalent (physical absorption) attachment10,11,12,13. For highly detailed information on printed glycan microarray technology for the uninitiated investigator, refer to these excellent reviews 13,15. Importantly, the recent Minimum Information Required for a Glycomics Experiment (MIRAGE) initiative describes guidelines for sample preparation16 and for reporting data from glycan microarray analyses17 to improve the standards in this growing field.
Here, we describe a detailed protocol for the fabrication of sialoglycan microarrays using a specific contact nano-printer in a 16-well format. Each of the glycans have a primary amine that mediate their covalent link to epoxy-activated glass slides. We also describe the development and analysis of one slide using various human sera samples, antibodies, and Sia-binding plant lectins. Sialoglycan microarray assays involve several major steps that include array fabrication, processing, development, and analysis. Array fabrication requires planning the array layout, preparing the glycans and source plate, programming the nano-printer, and printing the slides. Subsequently, the slides are processed, developed, and analyzed (Figure 1).

<table><tbody><tr><td>Primary-amine containing sialoglycans</td><td>Glycohub, Inc., Davis, CA, USA (http://www.glycohub.com/services)</td><td>Contact info@glycohubusa.com for compound requests</td><td>Printed glycans</td></tr><tr><td>Monosodium phosphate monohydrate</td><td>Sigma</td><td>S9638</td><td>Printing buffer component</td></tr><tr><td>Disodium phosphate heptahydrate</td><td>Sigma</td><td>S9390</td><td>Printing buffer component</td></tr><tr><td>Phosphate buffered saline</td><td>Hy-Labs</td><td>BP-507/500D</td><td>Printing buffer/ incubation/washing buffer</td></tr><tr><td>Tris-base</td><td>Sigma</td><td>T1503</td><td>Slide blocking reagent</td></tr><tr><td>Glycerol</td><td>Sigma</td><td>G-7893</td><td>Printing buffer component</td></tr><tr><td>Ethanolamine</td><td>Thermo-Fisher Scientific</td><td>0700/08</td><td>Slide blocking reagent</td></tr><tr><td>Ovalbumin (Grade V)</td><td>Sigma</td><td>A5503</td><td>Slide Blocking protein</td></tr><tr><td>Tween-20</td><td>Sigma</td><td>P7949</td><td>Slide washing detergent</td></tr><tr><td>Alexa 555-Hydrazide</td><td>Thermo-Fisher Scientific</td><td>A20501MP</td><td>Marker on array</td></tr><tr><td>ChromPure Human IgG, whole molecule</td><td>Jackson Immunoresearch</td><td>009-000-003</td><td>Printing component</td></tr><tr><td>Biotinylated- SNA</td><td>Vector Laboratories</td><td>B-1305</td><td>Plant Lectin &amp;ndash; binding Sia-alpha2&amp;ndash;6-linked</td></tr><tr><td>Biotinylated-MALII</td><td>Vector Laboratories</td><td>B-1265</td><td>Plant Lectin &amp;ndash; binding Sia-alpha2&amp;ndash;3-linked</td></tr><tr><td>Chicken-anti Neu5Gc IgY</td><td>BioLegend</td><td>146903</td><td>Primary detection</td></tr><tr><td>Cy3-Streptavidin</td><td>Jackson Immunoresearch</td><td>016-160-0848</td><td>Biotin binding</td></tr><tr><td>Cy3-anti Human IgG</td><td>Jackson Immunoresearch</td><td>109-165-088</td><td>Secondary detection against human IgG</td></tr><tr><td>Cy3-anti Chicken IgY</td><td>Jackson Immunoresearch</td><td>703-165-155</td><td>Secondary detection against chicken IgY</td></tr><tr><td>Human sera samples</td><td>Israeli Blood Bank</td><td></td><td>Primary detection</td></tr><tr><td>Compressed Nitrogen (Grade 5)</td><td></td><td></td><td>General dusting/drying tool</td></tr><tr><td>Epoxy-coated slides</td><td>Corning</td><td>40044</td><td>Slides</td></tr><tr><td>Epoxy-coated slides</td><td>PolyAn</td><td>2D 104-00-221</td><td>Slides. In this type of slides the surface is more hydrophobic (compared to Coring slides) therefore the glycans Print Buffer would need to be supplemented with 0.005% Tween-20 to obtain 100 &amp;micro;m size spots.</td></tr><tr><td>384-well microtiter plate</td><td>Genetix</td><td>2070</td><td>Printing plate</td></tr><tr><td>VWR lab marker</td><td>VWR</td><td>52877-310</td><td>Slide labeling</td></tr><tr><td>Staining Tube</td><td>ArrayIt</td><td>MST</td><td>Slide developing tool</td></tr><tr><td>Staining bath</td><td>VWR</td><td>25608-904</td><td>Slide developing tool</td></tr><tr><td>Slides glass holders</td><td>VWR</td><td>631-9321</td><td>Slide developing tool</td></tr><tr><td>GenePix Scanner</td><td>Molecular devices</td><td>4000B</td><td>Slide scanner</td></tr><tr><td>LM-60 NanoPrinter</td><td>ArrayIt</td><td>LM-60</td><td>Array printer</td></tr><tr><td>Pins</td><td>ArrayIt</td><td>946MP3</td><td>Printing pins</td></tr><tr><td>ProPlate Module</td><td>Grace Bio-Labs</td><td>P37004</td><td>Slide developing module</td></tr><tr><td>Distilled water</td><td>Bio-Lab</td><td>2321020500</td><td>Required for arrayer and humidifier</td></tr><tr><td>Electronic Multi Pippete, 8 Channel , volume range 2-125 &amp;mu;L</td><td>Thermo-Fisher Scientific (Matrix)</td><td>MA-2131 Impact2 Equalizer 384</td><td>Multi pippete for sample dispansing into 384-well plate</td></tr></tbody></table>

profiling anti-neu5gc igg in human sera with a sialoglycan microarray assay

Cells are covered with a cloak of carbohydrate chains (glycans) that is commonly altered in cancer and that includes variations in sialic acid (Sia) expression. These are acidic sugars that have a 9-carbon backbone and that cap vertebrate glycans on cell surfaces. Two of the major Sia forms in mammals are N-acetylneuraminic acid (Neu5Ac) and its hydroxylated form, N-glycolylneuraminic acid (Neu5Gc). Humans cannot produce endogenous Neu5Gc due to the inactivation of the gene encoding cytidine 5&#39;monophosphate-Neu5Ac (CMP-Neu5Ac) hydroxylase (CMAH). Foreign Neu5Gc is acquired by human cells through the dietary consumption of red meat and dairy and subsequently appears on diverse glycans on the cell surface, accumulating mostly on carcinomas. Consequently, humans have circulating anti-Neu5Gc antibodies that play diverse roles in cancer and other chronic inflammation-mediated diseases and that are becoming potential diagnostic and therapeutic targets. Here, we describe a high-throughput sialoglycan microarray assay to assess such anti-Neu5Gc antibodies in the human sera. Neu5Gc-containing glycans and their matched pairs of controls (Neu5Ac-containing glycans), each with a core primary amine, are covalently linked to epoxy-coated glass slides. We exemplify the printing of 56 slides in a 16-well format using a specific nano-printer capable of generating up to 896 arrays per print. Each slide can be used to screen 16 different human sera samples for the evaluation of anti-Neu5Gc antibody specificity, intensity, and diversity. The protocol describes the complexity of this robust tool and provides a basic guideline for those aiming to investigate the response to Neu5Gc dietary carbohydrate antigen in diverse clinical samples in an array format.

Array Printing, Development, and Analysis:
Printing a sialoglycan microarray with multiple glycan samples and human IgG STD curves in 16 different blocks requires thorough calibration to ensure that all samples are printed as uniformly as possible in all 16 blocks per slide and to all slides in the same print run. Therefore, multiple calibration experiments are required before the specific printing parameters are determined, includ...

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Profiling Anti-Neu5Gc IgG in Human Sera with a Sialoglycan Microarray Assay

A sialoglycan microarray assay can be used to evaluate anti-Neu5Gc antibodies in human sera, making it a potential high-throughput diagnostic assay for cancer and other chronic inflammation-mediated human diseases.

Cells are covered with a cloak of carbohydrate chains (glycans) that is commonly altered in cancer and that includes variations in sialic acid (Sia) ...

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9.4K Views.  Tel Aviv University. A sialoglycan microarray assay can be used to evaluate anti-Neu5Gc antibodies in human sera, making it a potential high-throughput diagnostic assay for cancer and other chronic inflammation-mediated human diseases.

Video: Profiling Anti-Neu5Gc IgG in Human Sera with a Sialoglycan Microarray Assay

Mass Spectrometric Analysis of Glycosphingolipid Antigens

Glycosphingolipids (GSL's) belong to the glycoconjugate class of biomacromolecules, which bear structural information for significant biological processes such as embryonic development, signal transduction, and immune receptor recognition1-2. They contain complex sugar moieties in the form of isomers, and lipid moieties with variations including fatty acyl chain length, unsaturation, and hydroxylation. Both carbohydrate and ceramide portions may be basis of biological significance. For example, tri-hexosylceramides include globotriaosylceramide (Gal&alpha;4Gal&beta;4Glc&beta;1Cer) and isoglobotriaosylceramide (Gal&alpha;3Gal&beta;4Glc&beta;1Cer), which have identical molecular masses but distinct sugar linkages of carbohydrate moiety, responsible for completely different biological functions3-4. In another example, it has been demonstrated that modification of the ceramide part of alpha-galactosylceramide, a potent agonist ligand for invariant NKT cells, changes their cytokine secretion profiles and function in animal models of cancer and auto-immune diseases5. The difficulty in performing a structural analysis of isomers in immune organs and cells serve as a barrier for determining many biological functions6.
Here, we present a visualized version of a method for relatively simple, rapid, and sensitive analysis of glycosphingolipid profiles in immune cells7-9. This method is based on extraction and chemical modification (permethylation, see below Figure 5A, all OH groups of hexose were replaced by MeO after permethylation reaction) of glycosphingolipids10-15, followed by subsequent analysis using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) and ion trap mass spectrometry. This method requires 50 million immune cells for a complete analysis. The experiments can be completed within a week. The relative abundance of the various glycosphingolipids can be delineated by comparison to synthetic standards. This method has a sensitivity of measuring 1% iGb3 among Gb3 isomers, when 2 fmol of total iGb3/Gb3 mixture is present9.
Ion trap mass spectrometry can be used to analyze isomers. For example, to analyze the presence of globotriaosylceramide and isoglobtriaosylceramide in the same sample, one can use the fragmentation of glycosphingolipid molecules to structurally discriminate between the two (see below Figure 5). Furthermore, chemical modification of the sugar moieties (through a permethylation reaction) improves the ionization and fragmentation efficiencies for higher sensitivity and specificity, and increases the stability of sialic acid residues. The extraction and chemical modification of glycosphingolipids can be performed in a classic certified chemical hood, and the mass spectrometry can be performed by core facilities with ion trap MS instruments.

A specific and sensitive method to gain insight into the expression profile of glycosphingolipid antigens in immune organs and cells is described. The method takes advantage of the ion trap mass spectrometry allowing step-wise fragmentation of glycosphingolipid molecules for structural analysis in comparison to chemically synthesized standards.

Glycosphingolipids (GSL's) belong to the glycoconjugate class of biomacromolecules, which bear structural information for significant biological processes ...

Immunology and Infection

Chemo-enzymatic Synthesis of N-glycans for Array Development and HIV Antibody Profiling

We present a highly efficient way for the rapid preparation of a wide range of N-linked oligosaccharides (estimated to exceed 20,000 structures) that are commonly found on human glycoproteins. To achieve the desired structural diversity, the strategy began with the chemo-enzymatic synthesis of three kinds of oligosaccharyl fluoride modules, followed by their stepwise &#945;-selective glycosylations at the 3-O and 6-O positions of the mannose residue of the common core trisaccharide having a crucial &#946;-mannoside linkage. We further attached the N-glycans to the surface of an aluminum oxide-coated glass (ACG) slide to create a covalent mixed array for the analysis of hetero-ligand interaction with an HIV antibody. In particular, the binding behavior of a newly isolated HIV-1 broadly neutralizing antibody (bNAb), PG9, to the mixture of closely spaced Man5GlcNAc2 (Man5) and 2,6-di-sialylated bi-antennary complex type N-glycan (SCT) on an ACG array, opens a new avenue to guide the effective immunogen design for HIV vaccine development. In addition, our ACG array embodies a powerful tool to study other HIV antibodies for hetero-ligand binding behavior.

Chemo-enzymatic Synthesis of N-glycans for Array Development and HIV Antibody Profiling

A modular approach to the synthesis of N-glycans for attachment to an aluminum oxide-coated glass slide (ACG slide) as a glycan microarray has been developed and its use for the profiling of an HIV broadly neutralizing antibody has been demonstrated.

We present a highly efficient way for the rapid preparation of a wide range of N-linked oligosaccharides (estimated to exceed 20,000 structures) that are ...

Chemistry

N-glycan Profiling of Glycoproteins by Hydrophilic Interaction Liquid Chromatography with Fluorescence and Mass Spectrometric Detection

Glycosylation is a vital modification found in proteins. N-glycan profiling of glycoproteins is required to detect novel biomarker candidates and determine glycan alterations in diseases. Most commercially available biopharmaceutical proteins are glycoproteins. The efficacy of these drugs is affected by glycosylation patterns. Therefore, an in-depth characterization method for the N-glycans is necessary. Here, we present a comprehensive approach for qualitative and quantitative analysis of N-glycans using hydrophilic interaction liquid chromatography equipped with fluorescence detection and tandem mass spectrometry (HILIC-FLD-MS/MS). N-glycans were released from glycoproteins with a facile method and labeled by a procainamide fluorophore tag in the strategy. Subsequently, the procainamide labeled N-glycans were analyzed by a HILIC-FLD-MS/MS technique. In this approach, N-glycan structures were confirmed by the tandem mass spectrometric analysis, whereas fluorescence detection was used for the quantitative analysis. An application for data analysis of the detected N-glycan peaks is described in the study. This protocol can be applied to any glycoprotein extracted from various species.

N-glycan Profiling of Glycoproteins by Hydrophilic Interaction Liquid Chromatography with Fluorescence and Mass Spectrometric Detection

N-glycan profiling of glycoproteins is essential for discovering novel biomarkers and understanding glycan functions in cellular events. Additionally, N-glycan analysis of protein biopharmaceuticals is very important for human use. In this current article, a high-throughput strategy for identifying and quantifying N-glycan structures was presented using the HILIC-FLD-MS/MS technique.

Glycosylation is a vital modification found in proteins. N-glycan profiling of glycoproteins is required to detect novel biomarker candidates and ...

Biochemistry

A Miniaturized Glycan Microarray Assay for Assessing Avidity and Specificity of Influenza A Virus Hemagglutinins

Influenza A virus (IAV) hemagglutinins recognize sialic acids on the cell surface as functional receptors to gain entry into cells. Wild waterfowl are the natural reservoir for IAV, but IAV can cross the species barrier to poultry, swine, horses and humans. Avian viruses recognize sialic acid attached to a penultimate galactose by a &#945;2-3 linkage (avian-type receptors) whereas human viruses preferentially recognize sialic acid with a &#945;2-6 linkage (human-type receptors). To monitor if avian viruses are adapting to human type receptors, several methods can be used. Glycan microarrays with diverse libraries of synthetic sialosides are increasingly used to evaluate receptor specificity. However, this technique is not used for measuring avidities. Measurement of avidity is typically achieved by evaluating the binding of serially diluted hemagglutinin or virus to glycans adsorbed to conventional polypropylene 96-well plates. In this assay, glycans with &#945;2-3 or &#945;2-6 sialic acids are coupled to biotin and adsorbed to streptavidin plates, or are coupled to polyacrylamide (PAA) which directly adsorb to the plastic. We have significantly miniaturized this assay by directly printing PAA-linked sialosides and their non PAA-linked counterparts on micro-well glass slides. This set-up, with 48 arrays on a single slide, enables simultaneous assays of 6 glycan binding proteins at 8 dilutions, interrogating 6 different glycans, including two non-sialylated controls. This is equivalent to 18x 96-well plates in the traditional plate assay. The glycan array format decreases consumption of compounds and biologicals and thus greatly enhances efficiency.

Using a printed glycan microarray strategy, a conventional 96-well plate assay was miniaturized for analysis of influenza A virus hemagglutinin avidity and specificity for sialic acid containing receptors.

Influenza A virus (IAV) hemagglutinins recognize sialic acids on the cell surface as functional receptors to gain entry into cells. Wild waterfowl are the ...

Metabolic Glycoengineering of Sialic Acid Using N-acyl-modified Mannosamines

Sialic acid (Sia) is a highly important constituent of glycoconjugates, such as N- and O-glycans or glycolipids. Due to its position at the non-reducing termini of oligo- and polysaccharides, as well as its unique chemical characteristics, sialic acid is involved in a multitude of different receptor-ligand interactions. By modifying the expression of sialic acid on the cell surface, sialic acid-dependent interactions will consequently be influenced. This can be helpful to investigate sialic acid-dependent interactions and has the potential to influence certain diseases in a beneficial way. Via metabolic glycoengineering (MGE), the expression of sialic acid on the cell surface can be modulated. Herein, cells, tissues, or even entire animals are treated with C2-modified derivatives of N-acetylmannosamine (ManNAc). These amino sugars act as sialic acid precursor molecules and therefore are metabolized to the corresponding sialic acid species and expressed on glycoconjugates. Applying this method produces intriguing effects on various biological processes. For example, it can drastically reduce&#160;the expression of polysialic acid (polySia) in treated neuronal cells and thus affects neuronal growth and differentiation. Here, we show the chemical synthesis of two of the most common C2-modified N-acylmannosamine derivatives, N-propionylmannosamine (ManNProp) as well as N-butanoylmannosamine (ManNBut), and further show how these non-natural amino sugars can be applied in cell culture experiments. The expression of modified sialic acid species is quantified by high performance liquid chromatography (HPLC) and further analyzed via mass spectrometry. The effects on polysialic acid expression are elucidated via Western blot using a commercially available polysialic acid antibody.

Metabolic Glycoengineering of Sialic Acid Using N-acyl-modified Mannosamines

Sialic acid is a typical monosaccharide-unit found in glycoconjugates. It is involved in a plethora of molecular and cellular interactions. Here we present a method to modify cell surface sialic acid expression using metabolic glycoengineering with N-acetylmannosamine derivatives.

Sialic acid (Sia) is a highly important constituent of glycoconjugates, such as N- and O-glycans or glycolipids. Due to its position at the non-reducing ...

Bioengineering

Automated Lectin-Based Glycan Profiling Using Bead Array in a Single Tip (BIST)

Rapid Glyco-Qualitative Assessment of Recombinant Proteins Using a Fully Automated System

Protein glycosylation, a critical post-translational modification, influences the stability, efficacy, and immunogenicity of recombinant proteins, including biopharmaceuticals. Glycan structures exhibit significant heterogeneity, varying with production cell types, culture conditions, and purification methods. Consequently, monitoring and evaluating the glycan structures of recombinant proteins is vital, particularly in biopharmaceutical production. The lectin microarray, a technique complementary to mass spectrometry, boasts high sensitivity and ease of use. However, it typically requires more than a day to yield results. To adapt it to non-glycoscience research or drug product process development, an automated, high-throughput alternative is needed. Therefore, the world's first fully automated lectin-based glycan profiling system was developed, utilizing the "bead array in a single tip (BIST)" technology concept. This system allows for the preparation and storage of lectin-immobilized beads in units of 1,000, with customizable parallel insertion orders for various purposes. This article presents a practical protocol for research involving "glyco-qualified" recombinant proteins. After testing their reactivity against 12 polyacrylamide-glycan conjugates, 15 lectins were selected to increase the system's versatility. In addition, the sample labeling process was optimized by switching from Cy3 to biotin, reducing the overall processing time by 30 min. For immediate data qualification, lectin-binding signals are displayed as a dotcode on the top monitor. The system's reliability was confirmed through day-to-day reproducibility tests, repeatability tests, and long-term storage tests, with a coefficient of variation of &lt;10%. This user-friendly and rapid glyco-analyzer has potential applications in the quality monitoring of endogenous glycoproteins for biomarker evaluation and validation. This method facilitates analysis for those new to glycoscience, thereby broadening its practical utility.

Author Spotlight: Advancing Protein Glycosylation Research Using a Fully Automated System

A system for the automated and rapid analysis of glycans on proteins was previously developed. This article presents the protocol for "glyco-qualitative analysis," optimized for a broad spectrum of users, such as those engaged in analyzing glycan structures in biopharmaceuticals and other glycoconjugate materials.

Protein glycosylation, a critical post-translational modification, influences the stability, efficacy, and immunogenicity of recombinant proteins, ...

Printed Glycan Array: A Sensitive Technique for the Analysis of the Repertoire of Circulating Anti-carbohydrate Antibodies in Small Animals

The repertoire of circulating anti-carbohydrate antibodies of a given individual is often associated with its immunological status. Not only the individual immune condition determines the success in combating internal and external potential threat signals, but also the existence of a particular pattern of circulating anti-glycan antibodies (and their serological level variation) could be a significant marker of the onset and progression of certain pathological conditions. Here, we describe a Printed Glycan Array (PGA)-based methodology that offers the opportunity to measure hundreds of glycan targets with very high sensitivity; using a minimal amount of sample, which is a common restriction present when small animals (rats, mice, hamster, etc.) are used as models to address aspects of human diseases. As a representative example of this approach, we show the results obtained from the analysis of the repertoire of natural anti-glycan antibodies in BALB/c mice. We demonstrate that each BALB/c mouse involved in the study, despite being genetically identical and maintained under the same conditions, develops a particular pattern of natural anti-carbohydrate antibodies. This work claims to expand the use of PGA technology to investigate repertoire (specificities) and the levels of circulating anti-carbohydrates antibodies, both in health and during any pathological condition.

This work shows the potential of printed glycan array (PGA) technology for the analysis of circulating anti-carbohydrate antibodies in small animals.

The repertoire of circulating anti-carbohydrate antibodies of a given individual is often associated with its immunological status. Not only the ...

Chemically-blocked Antibody Microarray for Multiplexed High-throughput Profiling of Specific Protein Glycosylation in Complex Samples

In this study, we describe an effective protocol for use in a multiplexed high-throughput antibody microarray with glycan binding protein detection that allows for the glycosylation profiling of specific proteins. Glycosylation of proteins is the most prevalent post-translational modification found on proteins, and leads diversified modifications of the physical, chemical, and biological properties of proteins. Because the glycosylation machinery is particularly susceptible to disease progression and malignant transformation, aberrant glycosylation has been recognized as early detection biomarkers for cancer and other diseases. However, current methods to study protein glycosylation typically are too complicated or expensive for use in most normal laboratory or clinical settings and a more practical method to study protein glycosylation is needed. The new protocol described in this study makes use of a chemically blocked antibody microarray with glycan-binding protein (GBP) detection and significantly reduces the time, cost, and lab equipment requirements needed to study protein glycosylation. In this method, multiple immobilized glycoprotein-specific antibodies are printed directly onto the microarray slides and the N-glycans on the antibodies are blocked. The blocked, immobilized glycoprotein-specific antibodies are able to capture and isolate glycoproteins from a complex sample that is applied directly onto the microarray slides. Glycan detection then can be performed by the application of biotinylated lectins and other GBPs to the microarray slide, while binding levels can be determined using Dylight 549-Streptavidin. Through the use of an antibody panel and probing with multiple biotinylated lectins, this method allows for an effective glycosylation profile of the different proteins found in a given human or animal sample to be developed.
Introduction
Glycosylation of protein, which is the most ubiquitous post-translational modification on proteins, modifies the physical, chemical, and biological properties of a protein, and plays a fundamental role in various biological processes1-6. Because the glycosylation machinery is particularly susceptible to disease progression and malignant transformation, aberrant glycosylation has been recognized as early detection biomarkers for cancer and other diseases 7-12. In fact, most current cancer biomarkers, such as the L3 fraction of &alpha;-1 fetoprotein (AFP) for hepatocellular carcinoma 13-15, and CA199 for pancreatic cancer 16, 17 are all aberrant glycan moieties on glycoproteins. However, methods to study protein glycosylation have been complicated, and not suitable for routine laboratory and clinical settings. Chen et al. has recently invented a chemically blocked antibody microarray with a glycan-binding protein (GBP) detection method for high-throughput and multiplexed profile glycosylation of native glycoproteins in a complex sample 18. In this affinity based microarray method, multiple immobilized glycoprotein-specific antibodies capture and isolate glycoproteins from the complex mixture directly on the microarray slide, and the glycans on each individual captured protein are measured by GBPs. Because all normal antibodies contain N-glycans which could be recognized by most GBPs, the critical step of this method is to chemically block the glycans on the antibodies from binding to GBP. In the procedure, the cis-diol groups of the glycans on the antibodies were first oxidized to aldehyde groups by using NaIO4 in sodium acetate buffer avoiding light. The aldehyde groups were then conjugated to the hydrazide group of a cross-linker, 4-(4-N-MaleimidoPhenyl)butyric acid Hydrazide HCl (MPBH), followed by the conjugation of a dipeptide, Cys-Gly, to the maleimide group of the MPBH. Thus, the cis-diol groups on glycans of antibodies were converted into bulky none hydroxyl groups, which hindered the lectins and other GBPs bindings to the capture antibodies. This blocking procedure makes the GBPs and lectins bind only to the glycans of captured proteins. After this chemically blocking, serum samples were incubated with the antibody microarray, followed by the glycans detection by using different biotinylated lectins and GBPs, and visualized with Cy3-streptavidin. The parallel use of an antibody panel and multiple lectin probing provides discrete glycosylation profiles of multiple proteins in a given sample 18-20. This method has been used successfully in multiple different labs 1, 7, 13, 19-31. However, stability of MPBH and Cys-Gly, complicated and extended procedure in this method affect the reproducibility, effectiveness and efficiency of the method. In this new protocol, we replaced both MPBH and Cys-Gly with one much more stable reagent glutamic acid hydrazide (Glu-hydrazide), which significantly improved the reproducibility of the method, simplified and shorten the whole procedure so that the it can be completed within one working day. In this new protocol, we describe the detailed procedure of the protocol which can be readily adopted by normal labs for routine protein glycosylation study and techniques which are necessary to obtain reproducible and repeatable results.

In this study, we describe an improved protocol for a multiplexed high-throughput antibody microarray with lectin detection method that can be used in glycosylation profiling of specific proteins. This protocol features new reliable reagents and significantly reduces the time, cost, and lab equipment requirements as compared to the previous procedure.

 In this study, we describe an effective protocol for use in a multiplexed high-throughput antibody microarray with glycan binding protein detection that ...

Biology

Immunoglobulin G N-Glycan Analysis by Ultra-Performance Liquid Chromatography

Glycomics is a new subspecialty in omics system research that offers significant potential in discovering next-generation biomarkers for disease susceptibility, drug target discovery, and precision medicine. Alternative IgG N-glycans have been reported in several common chronic diseases and suggested to have great potential in clinical applications (i.e., biomarkers for diagnosis and prediction of diseases). IgG N-glycans are widely characterized using the method of hydrophilic interaction chromatography (HILIC) ultra-performance liquid chromatography (UPLC). UPLC is a stable detection technology with good reproducibility and high relative quantitative accuracy. In addition, the structure of IgG N-glycan is clearly separated, and glycan composition and relative abundance in plasma are characterized.

Immunoglobulin G (IgG) N-glycan is characterized using hydrophilic interaction chromatography UPLC. In addition, the structure of IgG N-glycan is clearly separated. Presented here is an introduction to this experimental method so that it can be widely used in research settings.

Glycomics is a new subspecialty in omics system research that offers significant potential in discovering next-generation biomarkers for disease ...

Medicine

Elucidating Glycan Structure and Occurrence Using Microarray Polymer Profiling

Microarray Polymer Profiling (MAPP) for High-Throughput Glycan Analysis

Microarray polymer profiling (MAPP) is a robust and reproducible approach to systematically determine the composition and relative abundance of glycans and glycoconjugates within a variety of biological samples, including plant and algal tissues, food materials, and human, animal, and microbial samples. Microarray technology underpins the efficacy of this method by providing a miniaturized, high-throughput screening platform, allowing thousands of interactions between glycans and highly specific glycan-directed molecular probes to be characterized concomitantly, using only small amounts of analytes. Constituent glycans are chemically and enzymatically fractionated, before being sequentially extracted from the sample and directly immobilized onto nitrocellulose membranes. The glycan composition is determined by the attachment of specific glycan-recognizing molecular probes to the extorted and printed molecules. MAPP is complementary to conventional glycan analysis techniques, such as monosaccharide and linkage analysis and mass spectrometry. However, glycan-recognizing molecular probes provide insight into the structural configurations of glycans, which can aid in elucidating biological interactions and functional roles.

Author Spotlight: MAPP Protocol &#8211; Advancing Glycan Analysis 

Microarray polymer profiling (MAPP) is a high-throughput technique for compositional analysis of glycans in biological samples.

Microarray polymer profiling (MAPP) is a robust and reproducible approach to systematically determine the composition and relative abundance of glycans ...

Profiling Anti-Neu5Gc IgG in Human Sera with a Sialoglycan Microarray Assay

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Mass Spectrometric Analysis of Glycosphingolipid Antigens

Chemo-enzymatic Synthesis of N-glycans for Array Development and HIV Antibody Profiling

N-glycan Profiling of Glycoproteins by Hydrophilic Interaction Liquid Chromatography with Fluorescence and Mass Spectrometric Detection

A Miniaturized Glycan Microarray Assay for Assessing Avidity and Specificity of Influenza A Virus Hemagglutinins

Metabolic Glycoengineering of Sialic Acid Using N-acyl-modified Mannosamines

Rapid Glyco-Qualitative Assessment of Recombinant Proteins Using a Fully Automated System

Printed Glycan Array: A Sensitive Technique for the Analysis of the Repertoire of Circulating Anti-carbohydrate Antibodies in Small Animals

Chemically-blocked Antibody Microarray for Multiplexed High-throughput Profiling of Specific Protein Glycosylation in Complex Samples

Immunoglobulin G N-Glycan Analysis by Ultra-Performance Liquid Chromatography

Microarray Polymer Profiling (MAPP) for High-Throughput Glycan Analysis