We here describe the online liquid chromatography (LC) electrospray ionization mass spectrometry (MS) of underivatized glycans using a nanoscale normal-phase amide column at a flow rate of 300 nL/min. Retention on the amide column is based on polar interactions of the oligosaccharide hydroxyl groups with the stationary phase, and thus, the retention time predictably increases with elongation of the oligosaccharide chain. The system is characterized by its high chromatographic resolution, which routinely allows the separation of isobaric structures. Separation of oligosaccharide mixtures over a 1-h range permits the detailed characterization of the different species by multiple ion selection and fragmentation steps using ion trap MS. The here presented miniaturization of the online-LC system to the nanoscale in combination with ion trap MS allows the detection of oligosaccharide species in a mixture at low-femtomole sensitivity. Online normal-phase nano-LC-MS of complex oligosaccharide mixtures further facilitates the sensitive and detailed structural analysis of oligosaccharides by overcoming the need for cumbersome and time-consuming derivatization procedures such as reductive amination for labeling with hydrophobic fluorophores or labeling with tritium. The method should be useful for the sensitive and quick analysis of glycosylation patterns and individual oligosaccharides from biotechnologically produced glycoproteins as well as scarcely available biological samples.

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The N-linked carbohydrate chains of recombinant human erythropoietin expressed in CHO cells were quantitatively released with peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase F, separated from the remaining O-glycoprotein by gel-permeation chromatography, and subsequently fractionated via FPLC on Mono Q, HPLC on Lichrosorb-NH2 and high-pH anion-exchange chromatography on CarboPac PA1. The purified sialylated oligosaccharides were analyzed by one-dimensional and two-dimensional 500-MHz 1H-NMR spectroscopy. When necessary, oligosaccharides were treated with endo-beta-galactosidase (and N-acetyl-beta-glucosaminidase) followed by 1H-NMR analysis of the incubation products, to obtain additional structural information. Di-, tri-, tri'- and tetraantennary N-acetyllactosamine-type oligosaccharides occur which can be completely (major) or partially (minor) sialylated. Three different types of alpha 2-3-linked sialic acids are present, namely, N-acetylneuraminic acid (95%), N-glycolylneuraminic acid (2%) and N-acetyl-9-O-acetylneuraminic acid (3%). In the case of partial sialylation, a non-random distribution of the sialic acids over the branches is observed. One or two extra N-acetyllactosamine units, being exclusively located in the branches attached to the alpha 1-6-linked Man residue, can be present in completely or partially sialylated di-, tri'-, and tetraantennary oligosaccharides. Tetraantennary oligosaccharides with N-acetyllactosamine repeats could be digested quantitatively with endo-beta-galactosidase from Bacteroides fragilis, whereas under the same conditions tri' antennary oligosaccharides hardly reacted (< 15%). Using endo-beta-galactosidase from Escherichia freundii, these tri'antennary oligosaccharides could be digested more extensively (> 75%). The O-linked carbohydrate chains were released from the O-glycoprotein by alkaline borohydride treatment, and purified via FPLC on Mono Q and HPLC on Lichrosorb-NH2. Two O-glycans were found, namely, Neu5Ac alpha 2-3Gal beta 1-3GalNAc-ol and Neu5Ac alpha 2-3Gal beta 1-3(Neu5Ac alpha 2-6)GalNAc-ol.

BackgroundImmunoglobulin G1 (IgG1) effector functions are impacted by the structure of fragment crystallizable (Fc) tail-linked N-glycans. Low fucosylation levels on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein specific (anti-S) IgG1 has been described as a hallmark of severe coronavirus disease 2019 (COVID-19) and may lead to activation of macrophages via immune complexes thereby promoting inflammatory responses, altogether suggesting involvement of IgG1 Fc glycosylation modulated immune mechanisms in COVID-19.MethodsIn this prospective, observational single center cohort study, IgG1 Fc glycosylation was analyzed by liquid chromatography – mass spectrometry following affinity capturing from serial plasma samples of 159 SARS-CoV-2 infected patients.FindingsAt baseline close to disease onset, anti-S IgG1 glycosylation was highly skewed when compared to total plasma IgG1. A rapid, general reduction in glycosylation skewing was observed during the disease course. Low anti-S IgG1 galactosylation and sialylation as well as high bisection were early hallmarks of disease severity, whilst high galactosylation and sialylation and low bisection were found in patients with low disease severity. In line with these observations, anti-S IgG1 glycosylation correlated with various inflammatory markers.InterpretationAssociation of low galactosylation, sialylation as well as high bisection with disease severity suggests that Fc-glycan modulated interactions contribute to disease mechanism. Further studies are needed to understand how anti-S IgG1 glycosylation may contributes to disease mechanism and to evaluate its biomarker potential.FundingThis project received funding from the European Commission’s Horizon2020 research and innovation program for H2020-MSCA-ITN IMforFUTURE, under grant agreement number 721815.Research in contextEvidence before this studyAntibody glycosylation against the spike (S) protein of patients infected with severe acute respiratory syndrome SARS-CoV-2 has been reported as a potentially important determinant of COVID-19 disease severity. Studies have hitherto focused on afucosylation, a modification on immunoglobulin G1 (IgG) Fc-tail-linked N-glycans that enhances effector functions. Most of these studies featured limited sample numbers or were imperfectly matched with respect to demographic and other important confounding factors. Our lab has contributed to some of these studies, and we additionally searched for research articles on PubMed and Google Scholar from January 2020 to October 2021. To date, only two groups studied anti-S IgG1 glycosylation, which resulted in overall three publications found. However, none of these groups found a severity marker between hospitalized non-ICU and ICU patients or studied dynamic changes. Instead, exclusively fucosylation at the first available timepoint has been associated with disease severity between severely ill inpatients and mild outpatients.Added value of this studyIn this prospective, observational single center cohort study, we investigated the severity marker potential of anti-S IgG1 glycosylation in severe and mild hospitalized COVID-19 cases, and correlated these findings with numerous inflammation and clinical markers. Our study reveals low galactosylation and sialylation as well as high bisection on anti-S IgG1 as early hallmarks of severe COVID-19, after correction for age and sex effects. In line with these observations, anti-S IgG1 glycosylation correlated with many inflammatory markers. As days since onset is one of the major confounders of anti-S IgG1 glycosylation due to its highly dynamic nature, we additionally confirmed our findings in time-matched patient subgroups. We believe anti-S IgG1 glycosylation may be applicable for patient stratification upon hospitalization.Implications of all the available evidenceDemographic factors as well as temporal differences should be taken into consideration when analyzing IgG1 glycosylation of COVID-19 patients. Anti-S IgG1 glycosylation is highly dynamic, but is a promising early severity marker in COVID-19.

Background Sensitive diagnostics are needed for effective management and surveillance of schistosomiasis so that current transmission interruption goals set by WHO can be achieved. We aimed to screen the Schistosoma haematobium secretome to find antibody biomarkers of schistosome infection, validate their diagnostic performance in samples from endemic populations, and evaluate their utility as point of care immunochromatographic tests (POC-ICTs) to diagnose urogenital schistosomiasis in the field. MethodsWe did a biomarker identification study, in which we constructed a proteome array containing 992 validated and predicted proteins from S haematobium and screened it with serum and urine antibodies from endemic populations in Gabon, Tanzania, and Zimbabwe. Arrayed antigens that were IgG-reactive and a select group of antigens from the worm extracellular vesicle proteome, predicted to be diagnostically informative, were then evaluated by ELISA using the same samples used to probe arrays, and samples from individuals residing in a lowendemicity setting (ie, Pemba and Unguja islands, Zanzibar, Tanzania). The two most sensitive and specific antigens were incorporated into POC-ICTs to assess their ability to diagnose S haematobium infection from serum in a fielddeployable format. FindingsFrom array probing, in individuals who were infected, 208 antigens were the targets of significantly elevated IgG responses in serum and 45 antigens were the targets of significantly elevated IgG responses in urine. Of the five proteins that were validated by ELISA, Sh-TSP-2 (area under the curve [AUC] serum =0⋅98 [95% CI 0⋅95-1⋅00]; AUC urine =0⋅96 [0⋅93-0⋅99]), and MS3_01370 (AUC serum =0⋅93 [0⋅89-0⋅97]; AUC urine =0⋅81 [0⋅72-0⋅89]) displayed the highest overall diagnostic performance in each biofluid and exceeded that of S haematobium-soluble egg antigen in urine (AUC=0⋅79 [0⋅69-0⋅90]). When incorporated into separate POC-ICTs, Sh-TSP-2 showed absolute specificity and a sensitivity of 75% and MS3_01370 showed absolute specificity and a sensitivity of 89%.Interpretation We identified numerous biomarkers of urogenital schistosomiasis that could form the basis of novel antibody diagnostics for this disease. Two of these antigens, Sh-TSP-2 and MS3_01370, could be used as sensitive, specific, and field-deployable diagnostics to support schistosomiasis control and elimination initiatives, with particular focus on post-elimination surveillance.Funding Australian Trade and Investment Commission and Merck Global Health Institute.