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Stewart R.,MedImmune | Thom G.,MedImmune | Levens M.,MedImmune | Guler-Gane G.,MedImmune | And 6 more authors.
Protein Engineering, Design and Selection | Year: 2011

Ribosome display was applied to the Fc region of human immunoglobulin G (IgG1) to select for improved binding to human FcγRIIIa, the receptor expressed on human natural killer cells that mediates antibody-dependent cellular cytotoxicity (ADCC). A library of human Fcγ1 variants was generated using error-prone polymerase chain reaction, and subjected to multiple rounds of ribosome display selection against progressively decreasing concentrations of soluble human FcγRIIIa, to enrich for improved binders. Radioimmunoassay and alphascreen analyses of the aglycosylated IgG-Fc output revealed variants with improved binding to FcγRIIIa relative to wild-type IgG-Fc. Subsequent expression in human (HEK-EBNA) cells generated glycosylated IgGs with modified activity in ADCC assays. One particular variant, 125-B01 triggered enhanced ADCC (EC50 up to four-fold reduced with increased maximal lysis) relative to wild-type antibody, having more equal levels of ADCC for each allotype (V158/F158) of FcγRIIIa. Deconvolution of individual replacements within the variant showed that improved function arose from the Phe243Leu replacement within the CH2 domain, rather than the CH3 domain replacements Thr393Ala or His433Pro. Surprisingly, the oligosaccharide profiles of 125-B01 indicated more oligosaccharide chains lacking fucose, or with bisecting N-acetylglucosamine relative to wild-type IgG1, which correlates with improved function and the replacement Phe243Leu that is a carbohydrate contact residue within the CH2 domain. © The Author 2011. Published by Oxford University Press. All rights reserved.

Gotz L.,Swiss Institute of Bioinformatics | Abrahams J.L.,Research Frontiers | Mariethoz J.,Swiss Institute of Bioinformatics | Rudd P.M.,National Institute for Bioprocessing Research and Training | And 5 more authors.
Bioinformatics | Year: 2014

Sequencing oligosaccharides by exoglycosidases, either sequentially or in an array format, is a powerful tool to unambiguously determine the structure of complex N- and O-link glycans. Here, we introduce GlycoDigest, a tool that simulates exoglycosidase digestion, based on controlled rules acquired from expert knowledge and experimental evidence available in GlycoBase. The tool allows the targeted design of glycosidase enzyme mixtures by allowing researchers to model the action of exoglycosidases, thereby validating and improving the efficiency and accuracy of glycan analysis. © The Author 2014. Published by Oxford University Press.

Lauc G.,Glycobiology Laboratory | Lauc G.,University of Zagreb | Huffman J.E.,University of Edinburgh | Pucic M.,Glycobiology Laboratory | And 42 more authors.
PLoS Genetics | Year: 2013

Glycosylation of immunoglobulin G (IgG) influences IgG effector function by modulating binding to Fc receptors. To identify genetic loci associated with IgG glycosylation, we quantitated N-linked IgG glycans using two approaches. After isolating IgG from human plasma, we performed 77 quantitative measurements of N-glycosylation using ultra-performance liquid chromatography (UPLC) in 2,247 individuals from four European discovery populations. In parallel, we measured IgG N-glycans using MALDI-TOF mass spectrometry (MS) in a replication cohort of 1,848 Europeans. Meta-analysis of genome-wide association study (GWAS) results identified 9 genome-wide significant loci (P<2.27×10-9) in the discovery analysis and two of the same loci (B4GALT1 and MGAT3) in the replication cohort. Four loci contained genes encoding glycosyltransferases (ST6GAL1, B4GALT1, FUT8, and MGAT3), while the remaining 5 contained genes that have not been previously implicated in protein glycosylation (IKZF1, IL6ST-ANKRD55, ABCF2-SMARCD3, SUV420H1, and SMARCB1-DERL3). However, most of them have been strongly associated with autoimmune and inflammatory conditions (e.g., systemic lupus erythematosus, rheumatoid arthritis, ulcerative colitis, Crohn's disease, diabetes type 1, multiple sclerosis, Graves' disease, celiac disease, nodular sclerosis) and/or haematological cancers (acute lymphoblastic leukaemia, Hodgkin lymphoma, and multiple myeloma). Follow-up functional experiments in haplodeficient Ikzf1 knock-out mice showed the same general pattern of changes in IgG glycosylation as identified in the meta-analysis. As IKZF1 was associated with multiple IgG N-glycan traits, we explored biomarker potential of affected N-glycans in 101 cases with SLE and 183 matched controls and demonstrated substantial discriminative power in a ROC-curve analysis (area under the curve = 0.842). Our study shows that it is possible to identify new loci that control glycosylation of a single plasma protein using GWAS. The results may also provide an explanation for the reported pleiotropy and antagonistic effects of loci involved in autoimmune diseases and haematological cancer. © 2013 Lauc et al.

Doherty M.,National Institute for Bioprocessing Research and Training | McManus C.A.,National Institute for Bioprocessing Research and Training | McManus C.A.,University of Western Australia | McManus C.A.,Phylogica Ltd. | And 2 more authors.
Methods in Molecular Biology | Year: 2012

N-linked oligosaccharides are complex non-template-derived structures that are attached to the side chains of asparagine, via the nitrogen atom. Specific changes in the N-glycans of serum glycoproteins have been associated with the pathogenesis of many diseases. The oligosaccharides present on the C H2 domain of immunoglobulins are known to modulate the effector functions of the molecule. These glycans provoke various biological effects, necessitating the development of robust high-throughput technology in order to fully characterize the N-glycosylation profile. This chapter describes in detail four methods to release N-glycans from the glycoprotein of interest. Two of these protocols, referred to as the "In-Gel Block" and "1D sodium dodecyl sulfate-polyacrylamide gel electrophoresis" methods, require immobilization of the glycoprotein prior to analysis. An automated method is also described, involving the purification of immunoglobulins directly from fermentation media, and, finally, an "In-solution method" is detailed, which directly releases the N-glycans into solution. HILIC and WAX-HPLC are used to analyze the N-glycan profile. Exoglycosidase enzymes digestion arrays, in combination with computer-assisted data analysis, are used to determine both the sequence and linkage of the N-glycans present. © 2012 Springer Science+Business Media, LLC.

Knezevic A.,Genos Ltd | Bones J.,National Institute for Bioprocessing Research and Training | Kracun S.K.,Copenhagen University | Gornik O.,University of Zagreb | And 3 more authors.
Analyst | Year: 2011

A rapid glycomic profiling method is described wherein N-glycans from plasma samples individually labelled with aniline, 2-aminobenzamide and 2-aminoacridone are mixed, co-injected and separated in the same HILIC-fluorescence run. Transfer of the multiplexed method to UPLC-fluorescence permits an increase in sample throughput from 24 to 864 plasma samples per day. © 2011 The Royal Society of Chemistry.

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