Biology subjects

Wuhrer, M.

Publications and source records attributed to Wuhrer, M..

26 records · Page 2Linked to original sources

bioRxiv2020

Functional monovalency amplifies the pathogenicity of anti-MuSK IgG4 in myasthenia gravis

Human IgG4 usually displays anti-inflammatory activity, and observations of IgG4 autoantibodies causing severe autoimmune disorders are therefore poorly understood. In blood, IgG4 antibodies naturally engage in a stochastic process termed Fab-arm exchange in which unrelated IgG4s exchange half-molecules continuously. The resulting IgG4 antibodies are composed of two different binding sites, thereby acquiring monovalent binding and inability to cross-link for each antigen recognized. Here, we demonstrate this process amplifies autoantibody pathogenicity in a classic IgG4-mediated autoimmune disease: muscle-specific kinase (MuSK) myasthenia gravis (MG). In mice, monovalent anti-MuSK IgG4s caused rapid and severe myasthenic muscle weakness, whereas the same antibodies in their parental bivalent form were less potent or did not induce a phenotype. Mechanistically this could be explained by opposing effects on MuSK signaling. Isotype switching to IgG4 in an autoimmune response thereby may be a critical step in the development of disease. Our study establishes functional monovalency as a novel pathogenic mechanism in IgG4-mediated autoimmune disease and potentially other disorders. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=146 HEIGHT=200 SRC="FIGDIR/small/296293v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@45c221org.highwire.dtl.DTLVardef@1cc31cdorg.highwire.dtl.DTLVardef@d9b09borg.highwire.dtl.DTLVardef@1d9b681_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2020

Anti-SARS-CoV-2 IgG from severely ill COVID-19 patients promotes macrophage hyper-inflammatory responses

For yet unknown reasons, severely ill COVID-19 patients often become critically ill around the time of activation of adaptive immunity. Here, we show that anti-Spike IgG from serum of severely ill COVID-19 patients induces a hyper-inflammatory response by human macrophages, which subsequently breaks pulmonary endothelial barrier integrity and induces microvascular thrombosis. The excessive inflammatory capacity of this anti-Spike IgG is related to glycosylation changes in the IgG Fc tail. Moreover, the hyper-inflammatory response induced by anti-Spike IgG can be specifically counteracted in vitro by use of the active component of fostamatinib, an FDA- and EMA-approved therapeutic small molecule inhibitor of Syk. One sentence summaryAnti-Spike IgG promotes hyper-inflammation.

immunology↗

bioRxiv2020

Afucosylated immunoglobulin G responses are a hallmark of enveloped virus infections and show an exacerbated phenotype in COVID-19

IgG antibodies are crucial for protection against invading pathogens. A highly conserved N-linked glycan within the IgG-Fc-tail, essential for IgG function, shows variable composition in humans. Afucosylated IgG variants are already used in anti-cancer therapeutic antibodies for their elevated binding and killing activity through Fc receptors (Fc{gamma}RIIIa). Here, we report that afucosylated IgG which are of minor abundance in humans ([~]6% of total IgG) are specifically formed against surface epitopes of enveloped viruses after natural infections or immunization with attenuated viruses, while protein subunit immunization does not elicit this low fucose response. This can give beneficial strong responses, but can also go awry, resulting in a cytokine-storm and immune-mediated pathologies. In the case of COVID-19, the critically ill show aggravated afucosylated-IgG responses against the viral spike protein. In contrast, those clearing the infection unaided show higher fucosylation levels of the anti-spike protein IgG. Our findings indicate antibody glycosylation as a potential factor in inflammation and protection in enveloped virus infections including COVID-19.

immunology↗

bioRxiv2020

Site-specific glycosylation mapping of Fc gamma receptor IIIb from neutrophils of health donors

Fc gamma receptors (Fc{gamma}R) translate antigen-recognition by immunoglobulin G (IgG) into various immune responses. A better understanding of this key element of immunity promises novel insights into mechanisms of (auto-/allo-)immune diseases and more rationally designed antibody-based drugs. Glycosylation on both IgG and Fc{gamma}R impacts their interaction dramatically. In this study, we developed a straightforward and comprehensive analytical methodology to map Fc{gamma}RIIIb glycosylation from primary human material. In contrast to recently published alternatives, we assessed all glycosylation sites in a single LC-MS/MS run and simultaneously determined the donor allotype. Studying Fc{gamma}RIIIb derived from healthy donor neutrophils, we observed profound differences as compared to the soluble variant and the homologous Fc{gamma}RIIIa on natural killer cells. This method will allow assessment of Fc{gamma}RIII glycosylation differences between individuals, cell types, subcellular locations and pathophysiological conditions.

immunology↗

bioRxiv2019

Prominent members of the human gut microbiota express endo-acting O-glycanases to initiate mucin breakdown

The human gut microbiota (HGM) are closely associated with health, development and disease. The thick intestinal mucus layer, especially in the colon, is the key barrier between the contents of the lumen and the epithelial cells, providing protection against infiltration by the microbiota as well potential pathogens. The upper layer of the colonic mucus is a niche for a subset of the microbiota which utilise the mucin glycoproteins as a nutrient source and mucin grazing by the microbiota appears to play a key role in maintaining barrier function as well as community stability. Despite the importance of mucin breakdown for gut health, the mechanisms by which gut bacteria access this complex glycoprotein are not well understood. The current model for mucin degradation involves exclusively exo-acting glycosidases that sequentially trim monosaccharides from the termini of the glycan chains to eventually allow access to the mucin peptide backbone by proteases. However, this model is in direct contrast to the Sus paradigm of glycan breakdown used by the Bacteroidetes which involves extracellular cleavage of glycans by surface located endo-acting enzymes prior to import of the oligosaccharide products. Here we describe the discovery and characterisation of endo-acting family 16 glycoside hydrolases (GH16s) from prominent mucin degrading gut bacteria that specifically target the oligosaccharide side chains of intestinal mucins from both animals and humans. These endo-acting O-glycanases display {beta}1,4-glactosidase activity and in several cases are surface located indicating they are involved in the initial step in mucin breakdown. The data suggest a new paradigm for mucin breakdown by the microbiota and the endo-mucinases provide a potential tool to explore changes that occur in mucin structure in intestinal disorders such as inflammatory bowel disease and colon cancer.

biochemistry↗

bioRxiv2019

Systematic evaluation of normalization methods for glycomics data based on performance of network inference

Glycomics measurements, like all other high-throughput technologies, are subject to technical variation due to fluctuations in the experimental conditions. The removal of this non-biological signal from the data is referred to as normalization. Contrary to other omics data types, a systematic evaluation of normalization options for glycomics data has not been published so far. In this paper, we assess the quality of different normalization strategies for glycomics data with an innovative approach. It has been shown previously that Gaussian Graphical Models (GGMs) inferred from glycomics data are able to identify enzymatic steps in the glycan synthesis pathways in a data-driven fashion. Based on this finding, we here quantify the quality of a given normalization method according to how well a GGM inferred from the respective normalized data reconstructs known synthesis reactions in the glycosylation pathway. The method therefore exploits a biological measure of goodness. We analyzed 23 different normalization combinations applied to six large-scale glycomics cohorts across three experimental platforms (LC-ESI-MS, UHPLC-FLD and MALDI-FTICR-MS). Based on our results, we recommend normalizing glycan data using the Probabilistic Quotient method followed by log-transformation, irrespective of the measurement platform.

bioinformatics↗

bioRxiv2019

NK cell activation by RSV-specific antibodies is decreased in infants with severe respiratory infections and correlates with Fc-glycosylation

BackgroundRespiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract infections in infants and there is no vaccine available. In early life, the most important contributors to protection against infectious diseases are the innate immune system and maternal antibodies. However, the mechanisms by which antibodies can protect against RSV disease are incompletely understood, as both antibody levels and neutralization capacity correlate poorly with protection. We therefore asked whether antibody-mediated natural killer (NK) cell activation correlates with RSV disease.\n\nMethodsWe performed an observational case-control study including infants hospitalized for RSV infection (n=43, cases), hernia surgery (n=16, controls), or RSV-negative viral respiratory tract infections (n=18, controls). First, we determined RSV antigen-specific antibody levels in infant plasma using a multiplex immunoassay. Subsequently, we measured the capacity of these antibodies to activate NK cells. Finally, we assessed Fc-glycosylation of the RSV-specific antibodies by mass spectrometry.\n\nResultsWe found that RSV-specific maternal antibodies potently activate NK cells in vitro. While the concentrations of RSV-specific antibodies did not differ between cases and controls, antibodies from infants hospitalized for severe lower respiratory tract infections (RSV and/or other) induced significantly less NK cell interferon gamma production than those from uninfected controls. Furthermore, NK cell activation correlated with Fc-fucosylation of RSV-specific antibodies, but their glycosylation status did not significantly differ between cases and controls.\n\nConclusionsOur results suggest that Fc-dependent antibody function and quality, exemplified by NK cell activation and glycosylation, contribute to protection against severe RSV disease and warrant further studies to evaluate the potential of harnessing these activities to develop an effective vaccine.

immunology↗

bioRxiv2018

e-workflow for recording of glycomic mass spectrometric data in compliance with reporting guidelines

Glycomics targets released glycans from proteins, lipids and proteoglycans. High throughput glycomics is based on mass spectrometry (MS) that increasingly depends on exchange of data with databases and the use of software. This requires an agreed format for accurately recording of experiments, developing consistent storage modules and granting public access to glycomic MS data. The introduction of the MIRAGE (Mimimum Requirement for A Glycomics Experiment) reporting standards for glycomics was the first step towards automating glycomic data recording. This report describes a glycomic e-infrastructure utilizing a well established glycomics recording format (GlycoWorkbench), and a dedicated web tool for submitting MIRAGE-compatible MS information into a public experimental repository, UniCarb-DR. The submission of data to UniCarb-DR should be a part of the submission process for publications with glycomics MSn that conform to the MIRAGE guidelines. The structure of this pipeline allows submission of most MS workflows used in glycomics.

bioinformatics↗