Immunoglobulin G glycosylation in aging and diseases

Fluorescence-barcoded cell lines stably expressing membrane-anchored influenza neuraminidases

The discovery of broadly protective antibodies to the influenza virus neuraminidase (NA) has raised interest in NA as a vaccine target. However, recombinant, solubilized tetrameric NA ectodomains are often challenging to express and isolate, hindering the study of anti-NA humoral responses. To address this obstacle, we established a panel of 22 non-adherent cell lines stably expressing native, historical N1, N2, N3, N9, and NB NAs anchored on the cell surface. The cell lines are barcoded with fluorescent proteins, enabling high-throughput, 16-plex analyses of antibody binding with commonly available flow cytometers. The cell lines were at least as efficient as a Luminex multiplex binding assay at identifying NA antibodies from a library of unselected clonal IgGs derived from human memory B cells. The cell lines were also useful for measuring the magnitude and breadth of the serum antibody response elicited by experimental infection of rhesus macaques with influenza virus. The membrane-anchored NAs are catalytically active and are compatible with established sialidase activity assays. NA-expressing K530 cell lines therefore represent a useful tool for studying NA immunity and evaluating influenza vaccine efficacy.

Serum Disease-specific IgG Fc Glycosylation as Potential Biomarkers for Nonproliferative and Proliferative Diabetic Retinopathy Using Mass Spectrometry

PURPOSE

To investigate the potential of serum disease-specific immunoglobulin G (DSIgG) crystallizable fragment (Fc) N-glycosylation as a diagnostic biomarker for the identification of nonproliferative and proliferative diabetic retinopathy (DR).

METHODS

A total of 160 patients were enrolled and categorized into three groups according to clinical diagnosis: non-diabetic retinopathy (NDR, n=47); nonproliferative diabetic retinopathy (NPDR, n=51); and proliferative diabetic retinopathy (PDR, n=62). Gel electrophoresis was performed to separate IgG from morning fasting blood samples and polyaniline magnetic nanomaterials (Fe3O4@PANI) were used to enrich IgG N-glycopeptides from tryptic digestion. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI ToF MS) was used to detect the IgG N-glycopeptides.

RESULTS

Nine DSIgG N-glycopeptide ratios were significantly different among NDR, NPDR, and PDR groups. There are six glycopeptide ratios available to classify mild, moderate, and severe NPDR. Moreover, four glycopeptide ratios could identify patients with or without diabetic macular edema (DME). The prediction model exhibited good discriminatory performance in distinguishing patients with DR or NDR (AUC=0.8347), NPDR or PDR (AUC=0.7002), mild/moderate or severe NPDR (AUC=0.8059), and with or without DME (AUC=0.7846).

CONCLUSION

DSIgG Fc N-glycosylation ratios were closely associated with different stages of DR and may be used as potential biomarkers for the early diagnosis of NDR, NPDR, and PDR.

Plasma IgG Glycosylation Profiling Reveals the Biological Features of Early Chronic Obstructive Pulmonary Disease

Chronic inflammatory and immune dysregulation are critical drivers of the development and progression of chronic obstructive pulmonary disease (COPD). Posttranslational modifications, such as glycosylation of Immunoglobulin G (IgG), are crucial in modulating systemic inflammatory homeostasis. This study aims to profile plasma IgG glycopeptides (IgGPs) in COPD patients to uncover new insights into their pathogenesis and to identify novel biomarkers. An integrated platform that combines Fe3O4@PDA@DETA nanospheres enrichment with high-resolution mass spectrometry measurement was employed to analyze plasma IgG N-glycopeptides from 90 COPD patients, 45 clinically defined early COPD (CECOPD) patients, and 90 healthy individuals. To explore the underlying mechanism of COPD progression, correlations between IgG N-glycoforms and clinical parameters were assessed. Disease-specific IgGPs were identified in both the ECOPD and COPD cohorts. Notably, it was the IgG glycopattern, rather than the IgG levels themselves, that underwent changes as the disease progressed. In early COPD patients, there was a decrease in bisection, accompanied by an increase in site-specific afucosylated galactosylation and fucosylation of IgG, indicating an anti-inflammatory state. Conversely, in COPD patients, an increase in inflammation was observed, which was characterized by reduced galactosylation and sialylation. Interestingly, a subset of healthy controls displayed IgGP patterns similar to those of early COPD, possibly reflecting the impact of smoking and the associated immune responses. We finally identified 6 anti-inflammatory and 2 pro-inflammatory IgGPs as ECOPD-specific IgGP indicators. Collectively, these findings suggest that plasma IgG glycosylation holds great potential as a biomarker for early COPD diagnosis, providing valuable insights into the immune system changes during disease progression. The raw data files are publicly accessible via the ProteomeXchange Consortium with the identifier PXD056374.

Fc Proteoforms of ACPA IgG Discriminate Autoimmune Responses in Plasma and Synovial Fluid of Rheumatoid Arthritis Patients and Associate with Disease Activity

Autoantibodies and their post-translational modifications (PTMs) are insightful markers of autoimmune diseases providing diagnostic and prognostic clues, thereby informing clinical decisions. However, current autoantibody analyses focus mostly on IgG1 glycosylation representing only a subpopulation of the actual IgG proteome. Here, by taking rheumatoid arthritis (RA) as prototypic autoimmune disease, we sought to circumvent these shortcomings and illuminate the importance of (auto)antibody proteoforms employing a novel comprehensive mass spectrometry (MS)-based analytical workflow. Profiling of anti-citrullinated protein antibodies (ACPA) IgG and total IgG in paired samples of plasma and synovial fluid revealed a clear distinction of autoantibodies from total IgG and between biofluids. This discrimination relied on comprehensive subclass-specific PTM profiles including previously neglected features such as IgG3 CH3 domain glycosylation, allotype ratios, and non-glycosylated IgG. Intriguingly, specific proteoforms were found to correlate with markers of inflammation and disease accentuating the need of such approaches in clinical investigations and calling for further mechanistic studies to comprehend the role of autoantibody proteoforms in defining autoimmune responses.

Recent advances in analytical methods and bioinformatic tools for quantitative glycomics

The significance of glycans in various biological processes has been widely acknowledged. Quantitative glycomics is emerging as an important addition to clinical biomarker discovery, as it helps uncover disease-associated glycosylation patterns that are valuable for diagnosis, prognosis, and treatment evaluation. Compared to glycoproteomics and other established omics approaches, quantitative glycomics exhibits greater methodological diversity and it encounters various challenges in automation and standardization. Nonetheless, numerous advancements have been made in this field over the past 5 years. Here, we have reviewed recent progress in analytical methods and software to improve mass spectrometry-based quantitative glycomics primarily on N- and O-glycosylation. The discussion is organized into four sections: stable isotopic labeling, isobaric labeling, label-free, and fluorescence labeling strategies, with a particular emphasis on quantitative data interpretation. Novel derivatization methods and advanced techniques have been developed for high-throughput and highly sensitive glycan quantification with high accuracy. However, due to variations in glycan derivatization and difficulties in structural identification, most glycomic quantification methods are tailored to specific applications, and manual inspection is frequently necessary for precise data interpretation. Therefore, further advancements in glycan sample preparation, structural characterization, and automated data interpretation are essential to facilitate comprehensive and accurate quantification across a wide array of glycans.

Effects of testosterone and metformin on the GlycanAge index of biological age and the composition of the IgG glycome

With aging, the body's ability to maintain regular functions declines, increasing susceptibility to age-related diseases. Therapeutic interventions targeting the underlying biological changes of aging hold promise for preventing or delaying multiple age-related diseases. Metformin, a drug commonly used for diabetes treatment, has emerged as a potential gerotherapeutic agent due to its established safety record and preclinical and clinical data on its anti-aging effects. Glycosylation, one of the most common and complex co- and post-translational protein modifications, plays a crucial role in regulating protein function and has been linked to aging and various diseases. Changes in immunoglobulin G (IgG) glycosylation patterns have been observed with age, and these alterations may serve as valuable biomarkers for disease predisposition, diagnosis, treatment monitoring, and overall health assessment. In this study, we analyzed the IgG glycosylation patterns of white men from Europe, aged 29-45 years, under treatment with metformin, testosterone, metformin plus testosterone, and placebo (trial registration number NCT02514629, 2013/07/04), and investigated the longitudinal changes in glycosylation over time. We observed statistically significant differences in the IgG glycome composition between participants on testosterone therapy and placebo, with decreased agalactosylation and increased galactosylation and sialylation. However, metformin therapy did not result in statistically significant changes in glycosylation patterns. These findings contribute to our understanding of the impact of therapeutic interventions on IgG glycosylation and confirm the value of IgG glycosylation as a significant biomarker, capable of assessing biological age using the GlycanAge index and providing insight into overall health compared to chronological age.

New insights into phytochemicals via protein glycosylation focused on aging and diabetes

BACKGROUND

Protein glycosylation as a common post-translational modification that has significant impacts on protein folding, enzymatic activity, and interfering with receptor functioning. In recent years, with the rapid development of glycopeptide enrichment and analysis technology and the deepening of glycosylation research, glycosylation has gradually become a sign of disease occurrence and development. Multiple investigations suggest that protein glycosylation affect the advances of diabetes and aging.

PURPOSE AND METHODS

This review was focused on the action mechanisms of glycosylated proteins production, permanent abnormalities in extracellular matrix component function, inflammatory and reactive oxygen species production, as well as the glycosylated characterizations of diabetes and aging. Further, advances in glycosylation analysis and detection methods are presented for the first time, highlighting for needed future developments. All literatures were gathered from PubMed and Google Scholar.

RESULTS

Herein, we review how protein glycosylation impacts the progression of diabetes and aging. Specifically, we focus on various types of glycosylation, including N-linked glycosylation, O-linked glycosylation, C-glycosylation, S-glycosylation, and glycophosphatidylinositol (GPI) anchors. N-linked glycosylation and O-linked glycosylation are commonly observed glycosylation forms, wherein O-GlcNAcylation plays a significant role in diabetes, while N-glycan could serve as biomarkers for identifying inflammation and aging.

CONCLUSIONS

Protein glycosylation produces a vastly larger number of core glycan structures through utilizing at least 173 glycosyltransferases and repeated common scaffolds. Single protein may contain multiple glycosylation sites, and the structure and occupancy of glycan at each site may be different, resulting in the macro heterogeneity of protein glycosylation. This review will contribute to how protein glycosylation impacts the life progress of cells and its association with diseases.

Regulation and Function of the cGAS-STING Pathway: Mechanisms, Post-Translational Modifications, and Therapeutic Potential in Immunotherapy

Autoimmune diseases arise when the immune system attacks healthy tissues, losing tolerance for self-tissues. Normally, the immune system recognizes and defends against pathogens like bacteria and viruses. The cGAS-STING pathway, activated by pattern-recognition receptors (PRRs), plays a key role in autoimmune responses. The cGAS protein senses pathogenic DNA and synthesizes cGAMP, which induces conformational changes in STING, activating kinases IKK and TBK1 and leading to the expression of interferon genes or inflammatory mediators. This pathway is crucial in immunotherapy, activating innate immunity, enhancing antigen presentation, modulating the tumor microenvironment, and integrating into therapeutic strategies. Modulation strategies include small molecule inhibitors, oligonucleotide therapies, protein and antibody therapies, genetic and epigenetic regulation, cytokine and metabolite modulation, and nanoscale delivery systems. Post-translational modifications (PTMs) of the cGAS-STING pathway, such as phosphorylation, acetylation, ubiquitination, methylation, palmitoylation, and glycosylation, fine-tune immune responses by regulating protein activity, stability, localization, and interactions. These modifications are interconnected and collectively influence pathway functionality. We summarize the functions of cGAS-STING and its PTMs in immune and non-immune cells across various diseases, and explore potential clinical applications.

Comprehensive Immunoglobulin G, A, and M Glycopeptide Profiling for Large-Scale Biomedical Research

Glycosylation of immunoglobulin G (IgG) is recognized as a key modulator of cellular effector functions. At the same time, an increasing body of evidence underlines the importance of other antibody isotypes, especially IgA and IgM, in pathophysiological conditions. Therefore, methods to efficiently study the complex interplay between isotypes, subclasses, and glycosylation of antibodies during acute and chronic states of inflammation are needed. As a solution, we present an integrated and comprehensive method combining simultaneous affinity enrichment of IgG, IgA, and IgM with a single measurement, glycopeptide-centered LC-MS analysis of all isotypes which provides protein-specific (isotype and subclass), and site-specific N- and O-glycosylation quantitation. A two-protease approach provided individual peptides for each glycosylation site, allowing unambiguous compositional assignment and relative quantitation of glycoforms on the MS1 level as well as structural confirmation and partial isomer assignment on the MS/MS level. We demonstrate that our methodology can be efficiently applied to large clinical studies revealing differences in antibody glycosylation in women during and after pregnancy, as well as between healthy donors and patients with rheumatoid arthritis. In addition, this showcased the advantages of our method in comprehensiveness and resolution of isotypes, subclasses, and glycosylation sites as well as its precision and robustness.

Profiling of IgG N-glycosylation for axial spondyloarthritis and other rheumatic diseases

BACKGROUND

Axial spondyloarthritis (axSpA) is an inflammatory rheumatic disease with challenges in diagnosis and disease activity assessment. While alterations in immunoglobulin G (IgG) N-glycosylation have been observed in varied rheumatic diseases, those in axSpA remains unclear. This study aims to explore the role of IgG N-glycan profiles in diagnosis and disease activity of axSpA.

METHODS

A clinical case-control study was conducted involving patients with axSpA (n = 138), systemic lupus erythematosus (n = 102), rheumatoid arthritis (n = 106), osteoarthritis (n = 33), gout (n = 41) and healthy controls (n = 117). Ultra-performance liquid chromatography was employed to analyze the composition of the serum IgG N-glycome. Associations between IgG N-glycans and axSpA were investigated and compared to healthy controls and other four rheumatic diseases. The relationship among IgG N-glycosylation, disease activity, and inflammatory cytokines of axSpA patients were analyzed. The receiver operating characteristic (ROC) curve analysis was applied to evaluate the diagnostic/classification performance of IgG N-glycans to distinguish axSpA and its disease activity.

RESULTS

In patients with axSpA, the abundances of IgG galactosylation and sialylation were significantly lower than healthy controls, while the abundance of fucosylation was higher than the other four studied rheumatic diseases. Additionally, two asialylated IgG N-glycans (FA2 and FA2 [3]G1) were associated with axSpA, with adjusted odds ratios (AORs) of 5.62 (95% CI: 3.41-9.24) and 0.33 (95% CI: 0.22-0.50), respectively. Notably, decreased FA2 [3]G1 emerged as a characteristic IgG N-glycan associated with all five studied rheumatic diseases, while decreased FA2BG2S2 was a unique IgG N-glycan differentiating axSpA from the other four rheumatic diseases. Furthermore, FA2 displayed positive association with disease activity indicators (ASDAS-CRP, SPARCC-SIJ and SPARCC-spine) in axSpA. IgG N-glycans, particularly FA2 [3]G1, FA2BG2S2 and FA2, demonstrated canonical correlation with inflammatory cytokines, including interleukin-23 and tumor necrosis factor α, in axSpA (r = 0.519, P = 0.017).

CONCLUSIONS

Specific IgG N-glycans hold potential as novel biomarkers to enhance diagnosis and disease activity assessment in axSpA management.

N-glycosylation signature and its relevance in cardiovascular immunometabolism

Glycosylation is a post-translational modification in which complex, branched carbohydrates (glycans) are covalently attached to proteins or lipids. Asparagine-link protein (N-) glycosylation is among the most common types of glycosylation. This process is essential for many biological and cellular functions, and impaired N-glycosylation has been widely implicated in inflammation and cardiovascular diseases. Different technical approaches have been used to increase the coverage of the N-glycome, revealing a high level of complexity of glycans, regarding their structure and attachment site on a protein. In this context, new insights from genomic studies have revealed a genetic regulation of glycosylation, linking genetic variants to total plasma N-glycosylation and N-glycosylation of immunoglobulin G (IgG). In addition, RNAseq approaches have revealed a degree of transcriptional regulation for the glycoenzymes involved in glycan structure. However, our understanding of the association between cardiovascular risk and glycosylation, determined by a complex overlay of genetic and environmental factors, remains limited. Mostly, plasma N-glycosylation profiling in different human cohorts or experimental investigations of specific enzyme functions in models of atherosclerosis have been reported. Most of the uncovered glycosylation associations with pathological mechanisms revolve around the recruitment of inflammatory cells to the vessel wall and lipoprotein metabolism. This review aims to summarise insights from omics studies into the immune and metabolic regulation of N-glycosylation and its association with cardiovascular and metabolic disease risk and to provide mechanistic insights from experimental models. The combination of emerging techniques for glycomics and glycoproteomics with already achieved omics approaches to map the transcriptomic, epigenomic, and metabolomic profile at single-cell resolution will deepen our understanding of the molecular regulation of glycosylation as well as identify novel biomarkers and targets for cardiovascular disease prevention and treatment.

Synergistic effects of mutation and glycosylation on disease progression

Glycosylation, a post-translational modification, plays a crucial role in proper localization and function of proteins. It is regulated by multiple glycosyltransferases and can be influenced by various factors. Inherited missense mutations in glycosylated proteins such as NOTCH3, Low-density lipoprotein receptor (LDLR), and Amyloid precursor protein (APP) could affect their glycosylation states, leading to cerebral small vessel disease, hypercholesterolemia, and Alzheimer's disease, respectively. Additionally, physiological states and aging-related conditions can affect the expression levels of glycosyltransferases. However, the interplay between mutations in glycosylated proteins and changes in their glycosylation levels remains poorly understood. This mini-review summarizes the effects of glycosylation on transmembrane proteins with pathogenic mutations, including NOTCH3, LDLR, and APP. We highlight the synergistic contributions of missense amino acids in the mutant proteins and alterations in their glycosylation states to their molecular pathogenesis.

Facile Fabrication of Monodisperse Vinyl Hybrid Core-Shell Silica Microsphere with Short Range Radial Channel in bi-phase System

The development of monodisperse hybrid silica microspheres with highly regular pore structure and uniform distribution of functional groups have significant value in the biomolecular separation field. In this work, the short range ordered pore channels are precisely constructed onto the non-porous silica microsphere surface by a bi-phase assembly method, and the cylindrical silica channel introduced a plethora of vinyl groups by "one-pot" co-condensation to form vinyl hybrid silica shell. As hydrophilic interaction chromatography (HILIC) stationary phase, the vinyl hybrid core-shell silica microsphere is simply modified with zwitterion glutathione (SiO2@SiO2-GSH), in which the HILIC enrichment process is significantly shortened due to its specific porous characteristics. Most importantly, SiO2@SiO2-GSH microsphere can enrich 2186 N-glycopeptides from the rat liver protein digest within 2 min, which mapped to 806 glycoproteins. Compared with HILIC enrichment result within 1 h, the glycoproteins and glycopeptides overlap are 88.3% and 79.1%, performing excellent reproducibility. The short range ordered channels onto the silica microsphere surface exhibit excellent mass transfer efficiency, so the developed bi-phase assembly method is expected to design more advanced hybrid silica materials for other urgently fields.

Unveiling unique effector function-related bulk antibody profiles in long-term hemodialysis patients following COVID-19 mRNA booster vaccination

BACKGROUND

Hemodialysis patients exhibit a reduced response to vaccination and have different vaccine dose regimens. Vaccines induce antibodies and affect the inflammatory balance through antibody glycosylation and effector functions. Therefore, we aimed to analyze the antibody glycosylation profiles in hemodialysis patients who were vaccinated against severe acute respiratory syndrome coronavirus 2, infected with the virus, or both, and compare them with those of dialysis patients in a control group.

METHODS

Plasma samples from 112 hemodialysis patients were assigned to four groups: control, infected, vaccinated, and post-vaccine-infected. Paired plasma samples from 47 people with vaccination (vaccinees) were analyzed before and after the booster dose. The same analytical approach was applied to the four groups for a cross-sectional comparison.

RESULTS

Our study found that both vaccination and infection groups showed decreased fucosylation of IgG1, which is associated with a proinflammatory biosignature. However, vaccination also leads to increased galactosylation and bisection of IgG antibodies, which are associated with anti-inflammatory effects and the additional regulation of immune responses. In contrast, infection led to an additional decrease in the fucosylation of IgG2 and IgA, demonstrating a more intense proinflammatory biosignature than vaccination.

CONCLUSIONS

Our findings emphasize the proinflammatory biosignature of afucosylation in both vaccination and infection groups. Additionally, we uncovered further regulated profiles related to galactosylation in vaccinees. These findings suggest that antibody investigation for vaccination or infection should not solely focus on neutralization but should also consider effector function-related glycosylation profiling. This comprehensive information can be valuable for fine-tuning vaccine development in the future.

Structural glycobiology - from enzymes to organelles

Biological carbohydrate polymers represent some of the most complex molecules in life, enabling their participation in a huge range of physiological functions. The complexity of biological carbohydrates arises from an extensive enzymatic repertoire involved in their construction, deconstruction and modification. Over the past decades, structural studies of carbohydrate processing enzymes have driven major insights into their mechanisms, supporting associated applications across medicine and biotechnology. Despite these successes, our understanding of how multienzyme networks function to create complex polysaccharides is still limited. Emerging techniques such as super-resolution microscopy and cryo-electron tomography are now enabling the investigation of native biological systems at near molecular resolutions. Here, we review insights from classical in vitro studies of carbohydrate processing, alongside recent in situ studies of glycosylation-related processes. While considerable technical challenges remain, the integration of molecular mechanisms with true biological context promises to transform our understanding of carbohydrate regulation, shining light upon the processes driving functional complexity in these essential biomolecules.

Glycan profiling of multiple sclerosis oligoclonal bands with MALDI-TOF

Multiple sclerosis (MS) is a common autoimmune disease that primarily affects young adults. In this condition, the immune system attacks the myelin sheath of nerve cells, leading to a variety of neurological symptoms. MS diagnosis often relies on the analysis of oligoclonal bands (OCBs), which involves detecting oligoclonal immunoglobulin G (IgG) bands in cerebrospinal fluid (CSF) and serum. The objective of this study was to investigate the glycosylation profiles of IgG in patients suspected of having MS, using glycan analysis with MALDI-TOF mass spectrometry. Serum samples were analysed, and the IgG glycosylation patterns were compared across different OCB types. Our findings suggest that alterations in IgG glycans may serve as potential biomarkers for MS, providing insights into the disease's molecular mechanisms and aiding in early diagnosis. This study highlights the importance of glycomics in understanding the pathogenesis of MS and in the development of novel diagnostic techniques.

Improving Glycoproteomic Analysis Workflow by Systematic Evaluation of Glycopeptide Enrichment, Quantification, Mass Spectrometry Approach, and Data Analysis Strategies

Glycosylation is one of the most prevalent and crucial protein modifications. Quantitative site-specific characterization of glycosylation usually requires sophisticated intact glycopeptide analysis using glycoproteomics. Recent efforts have focused on the interrogation of intact glycopeptide analyses using tandem mass spectrometry. However, a systematic evaluation of the quantitative glycoproteomic workflow is still lacking. This study compared different strategies for glycopeptide enrichment alongside glycopeptide quantitation, as well as mass spectrometry and data analysis strategies, providing a comprehensive assessment of their efficacy. The ZIC-HILIC enrichment method demonstrated superior performance, representing a 26% improvement in identified glycopeptiudes compared to the MAX enrichment method. Quantification using TMT provided high precision and throughput with an average CV of 8%. Through systematic evaluation, this study established that the ZIC-HILIC enrichment method, quantification with TMT, and collision energies of 25, 35, and 45 using tandem mass spectrometry are the optimal workflow for higher-energy collisional dissociation (HCD) fragmentation, significantly enhancing the analysis of intact glycopeptides. Precise energy adjustment is crucial for the identification of certain glycans. Intact glycopeptides were analyzed using different software tools to investigate the identification and quantification of glycopeptides. By applying optimal settings, 5514 unique intact glycopeptides were in luminal and basal patient-derived xenograft (PDX) characterized models, highlighting distinct glycosylation profiles that may influence tumor behavior. This study offers a systematic approach to evaluate glycoproteomic analysis workflow.

A 2-year calorie restriction intervention reduces glycomic biological age biomarkers

Background/Objective

In a subset of participants from the CALERIE™ Phase 2 study we evaluated the effects of 2y of ~25% Calorie Restriction (CR) diet on IgG N-glycosylation (GlycAge), plasma and complement C3 N-glycome as markers of aging and inflammaging.

Methods

Plasma samples from 26 participants in the CR group who completed the CALERIE2 trial and were deemed adherent to the intervention (~>10 % CR at 12 mo) were obtained from the NIA AgingResearchBiobank. Glycomic investigations using UPLC or LC-MS analyses were conducted on samples from baseline (BL), mid-intervention (12 mo) and post-intervention (24 mo), and changes resulting from the 2y CR intervention were examined. In addition, anthropometric, clinical, metabolic, DNA methylation (epigenetic) and skeletal muscle transcriptomic data were analyzed to identify aging-related changes that occurred in tandem with the N-glycome changes.

Results

Following the 2y CR intervention, IgG galactosylation was higher at 24mo compared to BL (p = 0.051), digalactosylation and GlycAge (the IgG-based surrogate for biological age) were not different between BL and 12mo or BL and 24mo, but increased between 12mo and 24mo (p = 0.016, 0.027 respectively). GlycAge was also positively associated with TNF-α and ICAM-1 (p=0.030, p=0.017 respectively). Plasma highly branched glycans were decreased by the 2y intervention (BL vs 24 mo: p=0.013), but both plasma and IgG bisecting GlcNAcs were increased (BL vs 24mo: p<0.001, p = 0.01 respectively). Furthermore, total complement C3 protein concentrations were reduced (BL vs 24mo: p <0.001), as were Man9 glycoforms (BL vs 24mo: p<0.001), and Man10 (which is glucosylated) C3 glycoforms (BL vs 24mo: p = 0.046).

Conclusions

24-mos of CR was associated with several favorable, anti-aging, anti-inflammatory changes in the glycome: increased galactosylation, reduced branching glycans, and reduced GlycAge. These promising CR effects were accompanied by an increase in bisecting GlcNAc, a known pro-inflammatory biomarker. These intriguing findings linking CR, clinical, and glycomic changes may be anti-aging and inflammatory, and merit additional investigation.

IgG Glycosylation: Biomarker, Functional Modulator, and Structural Component

The family of IgG Abs is a crucial component of adaptive immunity. Glycosylation of IgG maintains its structural integrity and modulates its effector functions. In this review, we discuss IgG glycosylation covering cell biological as well as therapeutic and disease-related aspects, focusing on the glycan structures in distinct IgG regions (Fab versus Fc). We also cover the impact of IgG glycosylation on disease modulation and therapeutic outcomes, alongside the potential for development of vaccines designed to induce Ag-specific IgG with glycoforms for optimal immune responses. Overall, we emphasize the significance of studying glycosylation to enhance our understanding of the dynamics and functional impacts of IgG glycosylation. These insights could be beneficial for advancing future research and clinical applications.

Glycan clock of ageing-analytical precision and time-dependent inter- and i-individual variability

Ageing is a complex biological process with variations among individuals, leading to the development of ageing clocks to estimate biological age. Glycans, particularly in immunoglobulin G (IgG), have emerged as potential biomarkers of ageing, with changes in glycosylation patterns correlating with chronological age.For precision analysis, three different plasma pools were analysed over 26 days in tetraplicates, 312 samples in total. In short-term variability analysis, two cohorts were analysed: AstraZeneca MFO cohort of 26 healthy individuals (median age 20) and a cohort of 70 premenopausal Chinese women (median age 22.5) cohort monitored over 3 months. Long-term variability analysis involved two adult men aged 47 and 57, monitored for 5 and 10 years, respectively. Samples were collected every 3 months and 3 weeks, respectively. IgG N-glycan analysis followed a standardized approach by isolating IgG, its subsequent denaturation and deglycosylation followed by glycan cleanup and labelling. Capillary gel electrophoresis with laser-induced fluorescence (CGE-LIF) and ultra-performance liquid chromatography analyses were employed for glycan profiling. Statistical analysis involved normalization, batch correction, and linear mixed models to assess time effects on derived glycan traits.The intermediate precision results consistently exhibited very low coefficient of variation values across all three test samples. This consistent pattern underscores the high level of precision inherent in the CGE method for analysing the glycan clock of ageing. The AstraZeneca MFO cohort did not show any statistically significant trends, whereas the menstrual cycle cohort exhibited statistically significant trends in digalactosylated (G2), agalactosylated (G0) and fucosylation (F). These trends were attributed to the effects of the menstrual cycle. Long-term stability analysis identified enduring age-related trends in both subjects, showing a positive time effect in G0 and bisected N-acetylglucosamine, as well as a negative time effect in G2 and sialylation, aligning with earlier findings. Time effects measured for monogalactosylation, and F remained substantially lower than ones observed for other traits.The study found that IgG N-glycome analysis using CGE-LIF exhibited remarkably high intermediate precision. Moreover, the study highlights the short- and long-term stability of IgG glycome composition, coupled with a notable capacity to adapt and respond to physiological changes and environmental influences such as hormonal changes, disease, and interventions. The discoveries from this study propel personalized medicine forward by deepening our understanding of how IgG glycome relates to age-related health concerns. This study underscores the reliability of glycans as a biomarker for tracking age-related changes and individual health paths.

N-glycan as new potential biomarker for predicting treatment response in patients with type 2 diabetes mellitus

AIMS

To investigate the N-glycans related to the metformin efficacy in patients with type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

We enrolled 141 healthy controls and 195 newly diagnosed T2DM patients treated with metformin for 3 months. Serum N-glycan profile was determined by DNA sequencer - assisted fluorophore-assisted carbohydrate electrophoresis (DSA-FACE). The N-glycan model was established by logistic regression analysis. Receiver operating characteristic curve (ROC) analysis was used to analyze the predictive power of the N-glycan model for metformin efficacy.

RESULTS

The abundances of several N-glycans in serum of T2DM patients at baseline were significantly different from those of healthy controls and tended to recover the N-glycan of controls after 3 months treatment. Serum N-glycans changes were more significant in the good response group (FPG <7 mmol/L) after metformin treatment. In addition, the abundance of peak9 at baseline had an opposite tendency between HbA1c increased and decreased groups post-treatment, which could be a biomarker for predicting metformin efficacy. Peak9 combined with other 11 N-glycans at baseline was used to establish the predictive model to distinguish non-response from response patients (AUROC = 0.780, sensitivity = 70.6% and specificity = 77.5%).

CONCLUSIONS

Serum N-glycans may have potential value as biomarkers for indicating the efficacy of metformin.

Crosstalk Between Cytokines and IgG N-Glycosylation: Bidirectional Effects and Relevance to Clinical Innovation for Inflammatory Diseases

The crosstalk between cytokines and immunoglobulin G (IgG) N-glycosylation forms a bidirectional regulatory network that significantly impacts inflammation and immune function. This review examines how various cytokines, both pro- and anti-inflammatory, modulate IgG N-glycosylation, shaping antibody activity and influencing inflammatory responses. In addition, we explore how altered IgG N-glycosylation patterns affect cytokine production and immune signaling, either promoting or reducing inflammation. Through a comprehensive analysis of current studies, this review underscores the dynamic relationship between cytokines and IgG N-glycosylation. These insights enhance our understanding of the mechanisms underlying inflammatory diseases and contribute to improved strategies for disease prevention, diagnosis, monitoring, prognosis, and the exploration of novel treatment options. By focusing on this crosstalk, we identify new avenues for developing innovative diagnostic tools and therapies to improve patient outcomes in inflammatory diseases.

Predicting psychiatric risk: IgG N-glycosylation traits as biomarkers for mental health

Background

Growing evidence suggests that chronic inflammation, resulting from intricate immune system interactions, significantly contributes to the onset of psychiatric disorders. Observational studies have identified a link between immunoglobulin G (IgG) N-glycosylation and various psychiatric conditions, but the causality of these associations remains unclear.

Methods

Genetic variants for IgG N-glycosylation traits and psychiatric disorders were obtained from published genome-wide association studies. The inverse-variance-weighted (IVW) method, MR-Egger, and weighted median were used to estimate causal effects. The Cochran's Q test, MR-Egger intercept test, leave-one-out analyses, and MR-PRESSO global test were used for sensitivity analyses.

Results

In the Psychiatric Genomics Consortium (PGC) database, genetically predicted IGP7 showed a protective role in schizophrenia (SCZ), major depressive disorder (MDD), and bipolar disorder (BIP), while elevated IGP34, and IGP57 increased SCZ risk. High levels of IGP21 were associated with an increased risk of post-traumatic stress disorder (PTSD), while elevated levels of IGP22 exhibited a causal association with a decreased risk of attention-deficit/hyperactivity disorder (ADHD). No causal relationship between IgG N-glycan traits and autism spectrum disorder (ASD) and no evidence of reverse causal associations was found.

Conclusion

Here, we demonstrate that IgG N-glycan traits have a causal relationship with psychiatric disorders, especially IGP7's protective role, offering new insights into their pathogenesis. Our findings suggest potential strategies for predicting and intervening in psychiatric disorder risk through IgG N-glycan traits.

Potentially causal association between immunoglobulin G N-glycans and cardiometabolic diseases: Bidirectional two-sample Mendelian randomization study

BACKGROUND

Observational studies support that altered immunoglobulin G (IgG) N-glycosylation and inflammatory factors are associated with cardiometabolic diseases (CMDs); nevertheless, the causality between them remains unclear.

METHODS

Two-sample Mendelian randomization (MR) analyses were conducted to systematically investigate the bidirectional causality between IgG N-glycans and nine CMDs in both East Asians and Europeans.

RESULTS

In the forward MR analysis, the univariable MR analysis presented suggestive causality of 14 and eight genetically instrumented IgG N-glycans with CMDs in East Asians and Europeans, respectively; the multivariable MR analysis showed that ten and 11 pairs of glycan-CMD associations were identified in East Asian and European populations, respectively. In the reverse MR analysis, based on East Asians and Europeans, the univariable MR analysis presented suggestive causality of seven and 12 genetically instrumented CMDs with IgG N-glycans, respectively; the multivariable MR analysis presented that six and five CMD-glycan causality were found in East Asian and Europeans, respectively.

CONCLUSIONS

The comprehensive MR analyses provide suggestive evidence of bidirectional causality between IgG N-glycans and CMDs. This work helps to understand the molecular mechanism of the occurrence/progression of CMDs, optimize existing and develop new strategies to prevent CMDs, and contribute to the early identification of high-risk groups of CMDs.

Novel Antibody-Based Protection/Therapeutics in Staphylococcus aureus

Staphylococcus aureus is a commensal of the skin and nares of humans as well as the causative agent of infections associated with significant mortality. The acquisition of antibiotic resistance traits complicates the treatment of such infections and has prompted the development of monoclonal antibodies. The selection of protective antigens is typically guided by studying the natural antibody responses to a pathogen. What happens when the pathogen masks these antigens and subverts adaptive responses, or when the pathogen inhibits or alters the effector functions of antibodies? S. aureus is constantly exposed to its human host and has evolved all these strategies. Here, we review how anti-S. aureus targets have been selected and how antibodies have been engineered to overcome the formidable immune evasive activities of this pathogen. We discuss the prospects of antibody-based therapeutics in the context of disease severity, immune competence, and history of past infections.

The importance of IgG glycosylation-What did we learn after analyzing over 100,000 individuals

All four subclasses of immunoglobulin G (IgG) antibodies have glycan structures attached to the protein part of the IgG molecules. Glycans linked to the Fc portion of IgG are found in all IgG antibodies, while about one-fifth of IgG antibodies in plasma also have glycans attached to the Fab portion of IgG. The IgG3 subclass is characterized by more complex glycosylation compared to other IgG subclasses. In this review, we discuss the significant influence that glycans exert on the structural and functional properties of IgG. We provide a comprehensive overview of how the composition of these glycans can affect IgG's effector functions by modulating its interactions with Fcγ receptors and other molecules such as the C1q component of complement, which in turn influence various immune responses triggered by IgG, including antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). In addition, the importance of glycans for the efficacy of therapeutics like monoclonal antibodies and intravenous immunoglobulin (IVIg) therapy is discussed. Moreover, we offer insights into IgG glycosylation characteristics and roles derived from general population, disease-specific, and interventional studies. These studies indicate that IgG glycans are important biomarkers and functional effectors in health and disease.

A comprehensive review of transduction methods of lectin-based biosensors in biomedical applications

Biosensors have emerged as a pivotal technology in the biomedical field, significantly enhancing the rapidity and precision of biomolecule detection. These advancements are instrumental in refining diagnostic processes, optimizing treatments, and monitoring diseases more effectively. Central to the development of highly sensitive, selective, and stable biosensors are the bioreceptor and transducer components. This review paper discusses the use of lectin as a bioreceptor and explores the prevalent transducer methods employed in lectin-based biosensors, with a particular emphasis on their applications in biomedical research. The paper meticulously examines various transducers, with a spotlight on electrochemical and optical transduction methods, drawing from a wealth of previous studies to offer a comprehensive perspective on the application of these sensors in critical biomedical areas. These areas include early diagnosis, therapeutic interventions, and continuous health monitoring. Moreover, the review addresses the challenges of implementing lectin-based biosensors, such as specificity and stability issues. It also explores future possibilities, examining potential trends to overcome these challenges. In summary, this comprehensive analysis aspires to equip researchers with profound insights into the transformative potential of lectin-based biosensors, underscoring their significant role in the evolution of biomedical research and the broader healthcare landscape.

Genetics of glycosylation in mammalian development and disease

Glycosylation of proteins and lipids in mammals is essential for embryogenesis and the development of all tissues. Analyses of glycosylation mutants in cultured mammalian cells and model organisms have been key to defining glycosylation pathways and the biological functions of glycans. More recently, applications of genome sequencing have revealed the breadth of rare congenital disorders of glycosylation in humans and the influence of genetics on the synthesis of glycans relevant to infectious diseases, cancer progression and diseases of the immune system. This improved understanding of glycan synthesis and functions is paving the way for advances in the diagnosis and treatment of glycosylation-related diseases, including the development of glycoprotein therapeutics through glycosylation engineering.

The role of antibody glycosylation in autoimmune and alloimmune kidney diseases

Immunoglobulin glycosylation is a pivotal mechanism that drives the diversification of antibody functions. The composition of the IgG glycome is influenced by environmental factors, genetic traits and inflammatory contexts. Differential IgG glycosylation has been shown to intricately modulate IgG effector functions and has a role in the initiation and progression of various diseases. Analysis of IgG glycosylation is therefore a promising tool for predicting disease severity. Several autoimmune and alloimmune disorders, including critical and potentially life-threatening conditions such as systemic lupus erythematosus, anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis and antibody-mediated kidney graft rejection, are driven by immunoglobulin. In certain IgG-driven kidney diseases, including primary membranous nephropathy, IgA nephropathy and lupus nephritis, particular glycome characteristics can enhance in situ complement activation and the recruitment of innate immune cells, resulting in more severe kidney damage. Hypofucosylation, hypogalactosylation and hyposialylation are the most common IgG glycosylation traits identified in these diseases. Modulating IgG glycosylation could therefore be a promising therapeutic strategy for regulating the immune mechanisms that underlie IgG-driven kidney diseases and potentially reduce the burden of immunosuppressive drugs in affected patients.

FCGR2/3 polymorphisms are associated with susceptibility to Kawasaki disease but do not predict intravenous immunoglobulin resistance and coronary artery aneurysms

Introduction

Kawasaki disease (KD) is a pediatric vasculitis that can result in coronary artery aneurysm (CAA) formation, which is a dangerous complication. Treatment with intravenous immunoglobulin (IVIg) significantly decreases the risk of CAA, possibly through competitive binding to Fc-gamma receptors (FcγRs), which reduces the binding of pathological immune complexes. However, ~20% of children have recrudescence of fever and have an increased risk of CAA. Therefore, we aimed to identify genetic markers at the FCGR2/3 locus associated with susceptibility to KD, IVIg resistance, or CAA.

Materials and methods

We investigated the association of single-nucleotide polymorphisms (SNPs) and copy number variations (CNVs) at the FCGR2/3 locus with KD susceptibility, IVIg resistance, and CAA risk using a family-based test (KD susceptibility) and case-control analyses (IVIg resistance and CAA risk) in different cohorts, adding up to a total of 1,167 KD cases. We performed a meta-analysis on IVIg resistance and CAA risk including all cohorts supplemented by previous studies identified through a systematic search.

Results

FCGR2A-p.166His was confirmed to be strongly associated with KD susceptibility (Z = 3.17, p = 0.0015). In case-control analyses, all of the investigated genetic variations at the FCGR2/3 locus were generally not associated with IVIg resistance or with CAA risk, apart from a possible association in a Polish cohort for the FCGR3B-NA2 haplotype (OR = 2.15, 95% CI = 1.15-4.01, p = 0.02). Meta-analyses of all available cohorts revealed no significant associations of the FCGR2/3 locus with IVIg resistance or CAA risk.

Discussion

FCGR2/3 polymorphisms are associated with susceptibility to KD but not with IVIg resistance and CAA formation. Currently known genetic variations at the FCGR2/3 locus are not useful in prediction models for IVIg resistance or CAA risk.

Predicting Biochemical and Physiological Parameters: Deep Learning from IgG Glycome Composition

In immunoglobulin G (IgG), N-glycosylation plays a pivotal role in structure and function. It is often altered in different diseases, suggesting that it could be a promising health biomarker. Studies indicate that IgG glycosylation not only associates with various diseases but also has predictive capabilities. Additionally, changes in IgG glycosylation correlate with physiological and biochemical traits known to reflect overall health state. This study aimed to investigate the power of IgG glycans to predict physiological and biochemical parameters. We developed two models using IgG N-glycan data as an input: a regression model using elastic net and a machine learning model using deep learning. Data were obtained from the Korčula and Vis cohorts. The Korčula cohort data were used to train both models, while the Vis cohort was used exclusively for validation. Our results demonstrated that IgG glycome composition effectively predicts several biochemical and physiological parameters, especially those related to lipid and glucose metabolism and cardiovascular events. Both models performed similarly on the Korčula cohort; however, the deep learning model showed a higher potential for generalization when validated on the Vis cohort. This study reinforces the idea that IgG glycosylation reflects individuals' health state and brings us one step closer to implementing glycan-based diagnostics in personalized medicine. Additionally, it shows that the predictive power of IgG glycans can be used for imputing missing covariate data in deep learning frameworks.

Intricacies of aging and Down syndrome

Down syndrome is the most frequently occurring genetic condition, with a substantial escalation in risk associated with advanced maternal age. The syndrome is characterized by a diverse range of phenotypes, affecting to some extent all levels of organization, and its progeroid nature - early manifestation of aspects of the senile phenotype. Despite extensive investigations, many aspects and mechanisms of the disease remain unexplored. The current review aims to provide an overview of the main causes and manifestations of Down syndrome, while also examining the phenomenon of accelerated aging and exploring potential therapeutic strategies.

Glycosylation in aging and neurodegenerative diseases

Aging, a complex biological process, involves the progressive decline of physiological functions across various systems, leading to increased susceptibility to neurodegenerative diseases. In society, demographic aging imposes significant economic and social burdens due to these conditions. This review specifically examines the association of protein glycosylation with aging and neurodegenerative diseases. Glycosylation, a critical post-translational modification, influences numerous aspects of protein function that are pivotal in aging and the pathophysiology of diseases such as Alzheimer's disease, Parkinson's disease, and other neurodegenerative conditions. We highlight the alterations in glycosylation patterns observed during aging, their implications in the onset and progression of neurodegenerative diseases, and the potential of glycosylation profiles as biomarkers for early detection, prognosis, and monitoring of these age-associated conditions, and delve into the mechanisms of glycosylation. Furthermore, this review explores their role in regulating protein function and mediating critical biological interactions in these diseases. By examining the changes in glycosylation profiles associated with each part, this review underscores the potential of glycosylation research as a tool to enhance our understanding of aging and its related diseases.

The genetics and epidemiology of N- and O-immunoglobulin A glycomics

BACKGROUND

Immunoglobulin (Ig) glycosylation modulates the immune response and plays a critical role in ageing and diseases. Studies have mainly focused on IgG glycosylation, and little is known about the genetics and epidemiology of IgA glycosylation.

METHODS

We generated, using a novel liquid chromatography-mass spectrometry method, the first large-scale IgA glycomics dataset in serum from 2423 twins, encompassing 71 N- and O-glycan species.

RESULTS

We showed that, despite the lack of a direct genetic template, glycosylation is highly heritable, and that glycopeptide structures are sex-specific, and undergo substantial changes with ageing. We observe extensive correlations between the IgA and IgG glycomes, and, exploiting the twin design, show that they are predominantly influenced by shared genetic factors. A genome-wide association study identified eight loci associated with both the IgA and IgG glycomes (ST6GAL1, ELL2, B4GALT1, ABCF2, TMEM121, SLC38A10, SMARCB1, and MGAT3) and two novel loci specifically modulating IgA O-glycosylation (C1GALT1 and ST3GAL1). Validation of our findings in an independent cohort of 320 individuals from Qatar showed that the underlying genetic architecture is conserved across ancestries.

CONCLUSIONS

Our study delineates the genetic landscape of IgA glycosylation and provides novel potential functional links with the aetiology of complex immune diseases, including genetic factors involved in IgA nephropathy risk.

Immunoglobulin G glycosylation and its alterations in aging-related diseases

Immunoglobulin G (IgG) is an important serum glycoprotein and a major component of antibodies. Glycans on IgG affect the binding of IgG to the Fc receptor or complement C1q, which in turn affects the biological activity and biological function of IgG. Altered glycosylation patterns on IgG emerge as important biomarkers in the aging process and age-related diseases. Key aging-related alterations observed in IgG glycosylation include reductions in galactosylation and sialylation, alongside increases in agalactosylation, and bisecting GlcNAc. Understanding the role of IgG glycosylation in aging-related diseases offers insights into disease mechanisms and provides opportunities for the development of diagnostic and therapeutic strategies. This review summarizes five aspects of IgG: an overview of IgG, IgG glycosylation, IgG glycosylation with inflammation mediation, IgG glycan changes with normal aging, as well as the relevance of IgG glycan changes to aging-related diseases. This review provides a reference for further investigation of the regulatory mechanisms of IgG glycosylation in aging-related diseases, as well as for evaluating the potential of IgG glycosylation changes as markers of aging and aging-related diseases.

N-linked glycosylation of the M-protein variable region: glycoproteogenomics reveals a new layer of personalized complexity in multiple myeloma

OBJECTIVES

Multiple myeloma (MM) is a plasma cell malignancy characterized by a monoclonal expansion of plasma cells that secrete a characteristic M-protein. This M-protein is crucial for diagnosis and monitoring of MM in the blood of patients. Recent evidence has emerged suggesting that N-glycosylation of the M-protein variable (Fab) region contributes to M-protein pathogenicity, and that it is a risk factor for disease progression of plasma cell disorders. Current methodologies lack the specificity to provide a site-specific glycoprofile of the Fab regions of M-proteins. Here, we introduce a novel glycoproteogenomics method that allows detailed M-protein glycoprofiling by integrating patient specific Fab region sequences (genomics) with glycoprofiling by glycoproteomics.

METHODS

Glycoproteogenomics was used for the detailed analysis of de novo N-glycosylation sites of M-proteins. First, Genomic analysis of the M-protein variable region was used to identify de novo N-glycosylation sites. Subsequently glycopeptide analysis with LC-MS/MS was used for detailed analysis of the M-protein glycan sites.

RESULTS

Genomic analysis uncovered a more than two-fold increase in the Fab Light Chain N-glycosylation of M-proteins of patients with Multiple Myeloma compared to Fab Light Chain N-glycosylation of polyclonal antibodies from healthy individuals. Subsequent glycoproteogenomics analysis of 41 patients enrolled in the IFM 2009 clinical trial revealed that the majority of the Fab N-glycosylation sites were fully occupied with complex type glycans, distinguishable from Fc region glycans due to high levels of sialylation, fucosylation and bisecting structures.

CONCLUSIONS

Together, glycoproteogenomics is a powerful tool to study de novo Fab N-glycosylation in plasma cell dyscrasias.

IgG1 glycosylation highlights premature aging in Down syndrome

Down syndrome (DS) is characterized by lowered immune competence and premature aging. We previously showed decreased antibody response following SARS-CoV-2 vaccination in adults with DS. IgG1 Fc glycosylation patterns are known to affect the effector function of IgG and are associated with aging. Here, we compare total and anti-spike (S) IgG1 glycosylation patterns following SARS-CoV-2 vaccination in DS and healthy controls (HC). Total and anti-Spike IgG1 Fc N-glycan glycoprofiles were measured in non-exposed adults with DS and controls before and after SARS-CoV-2 vaccination by liquid chromatography-mass spectrometry (LC-MS) of Fc glycopeptides. We recruited N = 44 patients and N = 40 controls. We confirmed IgG glycosylation patterns associated with aging in HC and showed premature aging in DS. In DS, we found decreased galactosylation (50.2% vs. 59.0%) and sialylation (6.7% vs. 8.5%) as well as increased fucosylation (97.0% vs. 94.6%) of total IgG. Both cohorts showed similar bisecting GlcNAc of total and anti-S IgG1 with age. In contrast, anti-S IgG1 of DS and HC showed highly comparable glycosylation profiles 28 days post vaccination. The IgG1 glycoprofile in DS exhibits strong premature aging. The combination of an early decrease in IgG1 Fc galactosylation and sialylation and increase in fucosylation is predicted to reduce complement activity and decrease FcγRIII binding and subsequent activation, respectively. The altered glycosylation patterns, combined with decreased antibody concentrations, help us understand the susceptibility to severe infections in DS. The effect of premature aging highlights the need for individuals with DS to receive tailored vaccines and/or vaccination schedules.

Glyco-signatures in patients with advanced lung cancer during anti-PD-1/PD-L1 immunotherapy

Immune checkpoint inhibitors (ICIs) targeting programmed cell death 1/programmed cell death ligand-1 (PD-1/PD-L1) have significantly prolonged the survival of advanced/metastatic patients with lung cancer. However, only a small proportion of patients can benefit from ICIs, and clinical management of the treatment process remains challenging. Glycosylation has added a new dimension to advance our understanding of tumor immunity and immunotherapy. To systematically characterize anti-PD-1/PD-L1 immunotherapy-related changes in serum glycoproteins, a series of serum samples from 12 patients with metastatic lung squamous cell carcinoma (SCC) and lung adenocarcinoma (ADC), collected before and during ICIs treatment, are firstly analyzed with mass-spectrometry-based label-free quantification method. Second, a stratification analysis is performed among anti-PD-1/PD-L1 responders and non-responders, with serum levels of glycopeptides correlated with treatment response. In addition, in an independent validation cohort, a large-scale site-specific profiling strategy based on chemical labeling is employed to confirm the unusual characteristics of IgG N-glycosylation associated with anti-PD-1/PD-L1 treatment. Unbiased label-free quantitative glycoproteomics reveals serum levels' alterations related to anti-PD-1/PD-L1 treatment in 27 out of 337 quantified glycopeptides. The intact glycopeptide EEQFN 177STYR (H3N4) corresponding to IgG4 is significantly increased during anti-PD-1/PD-L1 treatment (FC=2.65, P=0.0083) and has the highest increase in anti-PD-1/PD-L1 responders (FC=5.84, P=0.0190). Quantitative glycoproteomics based on protein purification and chemical labeling confirms this observation. Furthermore, obvious associations between the two intact glycopeptides (EEQFN 177STYR (H3N4) of IgG4, EEQYN 227STFR (H3N4F1) of IgG3) and response to treatment are observed, which may play a guiding role in cancer immunotherapy. Our findings could benefit future clinical disease management.

A hierarchical structure in the N-glycosylation process governs the N-glycosylation output: prolonged cultivation induces glycoenzymes expression variations that are reflected in the cellular N-glycome but not in the protein and site-specific glycoprofile of CHO cells

N-glycosylation is a central component in the modification of secretory proteins. One characteristic of this process is a heterogeneous output. The heterogeneity is the result of both structural constraints of the glycoprotein as well as the composition of the cellular glycosylation machinery. Empirical data addressing correlations between glycosylation output and glycosylation machinery composition are seldom due to the low abundance of glycoenzymes. We assessed how differences in the glycoenzyme expression affected the N-glycosylation output at a cellular as well as at a protein-specific level. Our results showed that cellular N-glycome changes could be correlated with the variation of glycoenzyme expression, whereas at the protein level differential responses to glycoenzymes alterations were observed. We therefore identified a hierarchical structure in the N-glycosylation process: the enzyme levels in this complex pathway determine its capacity (reflected in the N-glycome), while protein-specific parameters determine the glycosite-specificity. What emerges is a highly variable and adaptable protein modification system that represents a hallmark of eukaryotic cells.

Plasma and Kidney Proteome Profiling Combined with Laser Capture Microdissection Reveal Large Increases in Immunoglobulins with Age

One of the main hallmarks of aging is aging-associated inflammation, also known as inflammaging. In this study, by comparing plasma and kidney proteome profiling of young and old mice using LC-MS profiling, we discovered that immunoglobulins are the proteins that exhibit the highest increase with age. This observation seems to have been disregarded because conventional proteome profiling experiments typically overlook the expression of high-abundance proteins or employ depletion methods to remove them before LC-MS analysis. We show that proteome profiling of immunoglobulins will likely be a useful biomarker of aging. Spatial profiling using immunofluorescence staining of kidney sections indicates that the main increases in immunoglobulins with age are localized in the glomeruli of the kidney. Using laser capture microdissection coupled with LC-MS, we show an increase in multiple immune-related proteins in glomeruli from aged mice. Increased deposition of immunoglobulins, immune complexes, and complement proteins in the kidney glomeruli may be a factor leading to reduced filtering capacity of the kidney with age. Therapeutic strategies to reduce the deposition of immunoglobulins in the kidney may be an attractive strategy for healthy aging.

The Human Blood N-Glycome: Unraveling Disease Glycosylation Patterns

Most of the proteins in the circulation are N-glycosylated, shaping together the total blood N-glycome (TBNG). Glycosylation is known to affect protein function, stability, and clearance. The TBNG is influenced by genetic, environmental, and metabolic factors, in part epigenetically imprinted, and responds to a variety of bioactive signals including cytokines and hormones. Accordingly, physiological and pathological events are reflected in distinct TBNG signatures. Here, we assess the specificity of the emerging disease-associated TBNG signatures with respect to a number of key glycosylation motifs including antennarity, linkage-specific sialylation, fucosylation, as well as expression of complex, hybrid-type and oligomannosidic N-glycans, and show perplexing complexity of the glycomic dimension of the studied diseases. Perspectives are given regarding the protein- and site-specific analysis of N-glycosylation, and the dissection of underlying regulatory layers and functional roles of blood protein N-glycosylation.

Autoimmune hepatitis displays distinctively high multi-antennary sialylation on plasma N-glycans compared to other liver diseases

BACKGROUND

Changes in plasma protein glycosylation are known to functionally affect proteins and to associate with liver diseases, including cirrhosis and hepatocellular carcinoma. Autoimmune hepatitis (AIH) is a liver disease characterized by liver inflammation and raised serum levels of IgG, and is difficult to distinguish from other liver diseases. The aim of this study was to examine plasma and IgG-specific N-glycosylation in AIH and compare it with healthy controls and other liver diseases.

METHODS

In this cross-sectional cohort study, total plasma N-glycosylation and IgG Fc glycosylation analysis was performed by mass spectrometry for 66 AIH patients, 60 age- and sex-matched healthy controls, 31 primary biliary cholangitis patients, 10 primary sclerosing cholangitis patients, 30 non-alcoholic fatty liver disease patients and 74 patients with viral or alcoholic hepatitis. A total of 121 glycans were quantified per individual. Associations between glycosylation traits and AIH were investigated as compared to healthy controls and other liver diseases.

RESULTS

Glycan traits bisection (OR: 3.78 [1.88-9.35], p-value: 5.88 × 10- 3), tetraantennary sialylation per galactose (A4GS) (OR: 2.88 [1.75-5.16], p-value: 1.63 × 10- 3), IgG1 galactosylation (OR: 0.35 [0.2-0.58], p-value: 3.47 × 10- 5) and hybrid type glycans (OR: 2.73 [1.67-4.89], p-value: 2.31 × 10- 3) were found as discriminators between AIH and healthy controls. High A4GS differentiated AIH from other liver diseases, while bisection associated with cirrhosis severity.

CONCLUSIONS

Compared to other liver diseases, AIH shows distinctively high A4GS levels in plasma, with potential implications on glycoprotein function and clearance. Plasma-derived glycosylation has potential to be used as a diagnostic marker for AIH in the future. This may alleviate the need for a liver biopsy at diagnosis. Glycosidic changes should be investigated further in longitudinal studies and may be used for diagnostic and monitoring purposes in the future.

High-throughput N-glycan analysis in aging and inflammaging: State of the art and future directions

As the global population ages at an unprecedented rate, the prevalence of age-related diseases is increasing, making inflammaging - a phenomenon characterized by a chronic, low-grade inflammatory state that follows aging - a significant concern. Understanding the mechanisms of inflammaging and its impact on health is critical for developing strategies to improve the quality of life and manage health in the aging population. Despite their crucial roles in various biological processes, including immune response modulation, N-glycans, oligosaccharides covalently attached to many proteins, are often overlooked in clinical and research studies. This repeated oversight is largely due to their inherent complexity and the complexity of the analysis methods. High-throughput N-glycan analysis has emerged as a transformative tool in N-glycosylation research, enabling cost- and time-effective, detailed, and large-scale examination of N-glycan profiles. This paper is the first to explore the application of high-throughput N-glycomics techniques to investigate the complex interplay between N-glycosylation and the immune system in aging. Technological advancements have significantly improved Nglycan detection and characterization, providing insights into age-related changes in Nglycosylation. Key findings highlight consistent shifts in immunoglobulin G (IgG) and plasma/serum glycoprotein glycosylation with age, with a pronounced rise in agalactosylated structures bound to IgG that also affect the composition of the total plasma N-glycome. These N-glycan modifications seem to be strongly associated with inflammaging and have been identified as valuable biomarkers for biological age, predictors of disease risk, and proxy biomarkers for monitoring intervention efficacy at the individual level. Despite current challenges related to data complexity and methodological limitations, ongoing technological innovations and interdisciplinary research are expected tofurther advance our knowledge of glycan biology, improve diagnostic and therapeutic strategies, and promote healthier aging. The integration of glycomics with other omics approaches holds promise for a more comprehensive understanding of the aging immune system, paving the way for personalized medicine and targeted interventions to mitigate inflammaging. In conclusion, this paper underscores the transformative impact of high-throughput Nglycan analysis in aging and inflammaging.

Local Immune Activation and Age Impact on Humoral Immunity in Mice, with a Focus on IgG Sialylation

Age alters the host's susceptibility to immune induction. Humoral immunity with circulating antibodies, particularly immunoglobulin G (IgG), plays an essential role in immune response. IgG glycosylation in the fragment crystallizable (Fc) region, including sialylation, is important in regulating the effector function by interacting with Fc gamma receptors (FcγRs). Glycosylation is fundamentally changed with age and inflammatory responses. We aimed to explore the regulation of humoral immunity by comparing responses to antigen-induced immune challenges in young and adult mice using a local antigen-induced arthritis mouse model. This study examines the differences in immune response between healthy and immune-challenged states across these groups. Our initial assessment of the arthritis model indicated that adult mice presented more severe knee swelling than their younger counterparts. In contrast, we found that neither histological assessment, bone mineral density, nor the number of osteoclasts differs. Our data revealed an age-associated but not immune challenge increase in total IgG; the only subtype affected by immune challenge was IgG1 and partially IgG3. Interestingly, the sialylation of IgG2b and IgG3 is affected by age and immune challenges but not stimulated further by immune challenges in adult mice. This suggests a shift in IgG towards a pro-inflammatory and potentially pathogenic state with age and inflammation.

Changes in the N-glycosylation of porcine immune globulin G during postnatal development

N-glycosylation influences the effectiveness of immune globulin G (IgG) and thus the immunological downstream responses of immune cells. This impact arises from the presence of N-glycans within the Fc region, which not only alters the conformation of IgG but also influences its steric hindrance. Consequently, these modifications affect the interaction between IgG and its binding partners within the immune system. Moreover, this posttranslational modification vary according to the physiological condition of each individual. In this study, we examined the N-glycosylation of IgG in pigs from birth to five months of age. Our analysis identified a total of 48 distinct N-glycan structures. Remarkably, we observed defined changes in the composition of these N-glycans during postnatal development. The presence of agalactosylated and sialylated structures increases in relation to the number of N-glycans terminated by galactose residues during the first months of life. This shift may indicate a transition from passively transferred antibodies from the colostrum of the sow to the active production of endogenous IgG by the pig's own immune system.

Genetic insights into across pancreatitis types: the causal influence of immunoglobulin G N-glycosylation variants on disease risk

Background

While a few case-control studies indicated a possible correlation of IgG N-glycosylation patterns with pancreatitis, their restricted sample sizes and methodologies prevented conclusive insights into causality or distinguishing traits across pancreatitis types.

Method

We conducted a two-sample Mendelian Randomization (MR) analysis to investigate the causal relationship between 77 IgG N-glycosylation traits and various types of pancreatitis, including acute pancreatitis (AP), chronic pancreatitis (CP), alcohol acute pancreatitis (AAP), and alcohol chronic pancreatitis (ACP). This analysis utilized summary-level data from genome-wide association studies (GWAS), employing methods such as IVW, MR-Egger, and weighted median. To ensure the robustness of our findings, several sensitivity analyses, including Cochran's Q statistic, leave-one-out, MR-Egger intercept, and MR-PRESSO global test were conducted.

Result

Our study uncovered the causal relationship between specific IgG N-glycosylation traits and various types of pancreatitis. Notably, an increase in genetically predicted IGP7 levels was associated with a decreased risk of developing AP. For CP, our data suggested a protective effect associated with higher levels of both IGP7 and IGP31, contrasting with increased levels of IGP27 and IGP65, which were linked to a heightened risk. Moreover, in the case of AAP, elevated IGP31 levels were causatively associated with a lower incidence, while higher IGP26 levels correlated with an increased risk for ACP.

Conclusion

This study establishes causal relationship between specific IgG N-glycosylation patterns and varying risks of different pancreatitis forms, underscoring their potential as predictive biomarkers. These findings necessitate further exploration into the underlying mechanisms, promising to inform more personalized diagnostic and therapeutic strategies in pancreatitis management.

Assessment of IgG-Fc glycosylation from individual RhD-specific B cell clones reveals regulation at clonal rather than clonotypic level

The type and strength of effector functions mediated by immunoglobulin G (IgG) antibodies rely on the subclass and the composition of the N297 glycan. Glycosylation analysis of both bulk and antigen-specific human IgG has revealed a marked diversity of the glycosylation signatures, including highly dynamic patterns as well as long-term stability of profiles, yet information on how individual B cell clones would contribute to this diversity has hitherto been lacking. Here, we assessed whether clonally related B cells share N297 glycosylation patterns of their secreted IgG. We differentiated single antigen-specific peripheral IgG+ memory B cells into antibody-secreting cells and analysed Fc glycosylation of secreted IgG. Furthermore, we sequenced the variable region of their heavy chain, which allowed the grouping of the clones into clonotypes. We found highly diverse glycosylation patterns of culture-derived IgG, which, to some degree, mimicked the glycosylation of plasma IgG. Each B cell clone secreted IgG with a mixture of different Fc glycosylation patterns. The majority of clones produced fully fucosylated IgG. B cells producing afucosylated IgG were scattered across different clonotypes. In contrast, the remaining glycosylation traits were, in general, more uniform. These results indicate IgG-Fc fucosylation to be regulated at the single-clone level, whereas the regulation of other glycosylation traits most likely occurs at a clonotypic or systemic level. The discrepancies between plasma IgG and culture-derived IgG, could be caused by the origin of the B cells analysed, clonal dominance or factors from the culture system, which need to be addressed in future studies.

Complement activation and effector pathways in membranous nephropathy

Complement activation has long been recognized as a central feature of membranous nephropathy (MN). Evidence for its role has been derived from the detection of complement products in biopsy tissue and urine from patients with MN and from mechanistic studies primarily based on the passive Heymann nephritis model. Only recently, more detailed insights into the exact mechanisms of complement activation and effector pathways have been gained from patient data, animal models, and in vitro models based on specific target antigens relevant to the human disease. These data are of clinical relevance, as they parallel the recent development of numerous specific complement therapeutics for clinical use. Despite efficient B-cell depletion, many patients with MN achieve only partial remission of proteinuria, which may be explained by the persistence of subepithelial immune complexes and ongoing complement-mediated podocyte injury. Targeting complement, therefore, represents an attractive adjunct treatment for MN, but it will need to be tailored to the specific complement pathways relevant to MN. This review summarizes the different lines of evidence for a central role of complement in MN and for the relevance of distinct complement activation and effector pathways, with a focus on recent developments.

N-Glycosylation Profiles of Immunoglobulin G and Future Cardiovascular Events

BACKGROUND

Posttranslational glycosylation of IgG can modulate its inflammatory capacity through structural variations. We examined the association of baseline IgG N-glycans and an IgG glycan score with incident cardiovascular disease (CVD).

METHODS

IgG N-glycans were measured in 2 nested CVD case-control studies: JUPITER (Justification for the Use of Statins in Prevention: an Intervention Trial Evaluating Rosuvastatin; NCT00239681; primary prevention; discovery; Npairs=162); and TNT trial (Treating to New Targets; NCT00327691; secondary prevention; validation; Npairs=397). Using conditional logistic regression, we investigated the association of future CVD with baseline IgG N-glycans and a glycan score adjusting for clinical risk factors (statin treatment, age, sex, race, lipids, hypertension, and smoking) in JUPITER. Significant associations were validated in TNT, using a similar model further adjusted for diabetes. Using least absolute shrinkage and selection operator regression, an IgG glycan score was derived in JUPITER as a linear combination of selected IgG N-glycans.

RESULTS

Six IgG N-glycans were associated with CVD in both studies: an agalactosylated glycan (IgG-GP4) was positively associated, while 3 digalactosylated glycans (IgG glycan peaks 12, 13, 14) and 2 monosialylated glycans (IgG glycan peaks 18, 20) were negatively associated with CVD after multiple testing correction (overall false discovery rate <0.05). Four selected IgG N-glycans comprised the IgG glycan score, which was associated with CVD in JUPITER (adjusted hazard ratio per glycan score SD, 2.08 [95% CI, 1.52-2.84]) and validated in TNT (adjusted hazard ratio per SD, 1.20 [95% CI, 1.03-1.39]). The area under the curve changed from 0.693 for the model without the score to 0.728 with the score in JUPITER (PLRT=1.1×10-6) and from 0.635 to 0.637 in TNT (PLRT=0.017).

CONCLUSIONS

An IgG N-glycan profile was associated with incident CVD in 2 populations (primary and secondary prevention), involving an agalactosylated glycan associated with increased risk of CVD, while several digalactosylated and sialylated IgG glycans associated with decreased risk. An IgG glycan score was positively associated with future CVD.

An efficient strategy with a synergistic effect of hydrophilic and electrostatic interactions for simultaneous enrichment of N- and O-glycopeptides

N- and O-glycosylation modifications of proteins are closely linked to the onset and development of many diseases and have gained widespread attention as potential targets for therapy and diagnosis. However, the low abundance and low ionization efficiency of glycopeptides as well as the high heterogeneity make glycosylation analysis challenging. Here, an enrichment strategy, using Knoevenagel copolymers modified with polydopamine-adenosine (denoted as PDA-ADE@KCP), was firstly proposed for simultaneous enrichment of N- and O-glycopeptides through the synergistic effects of hydrophilic and electrostatic interactions. The adjustable charged surface and hydrophilic properties endow the material with the capability to achieve effective enrichment of intact N- and O-glycopeptides. The experimental results exhibited excellent selectivity (1 : 5000) and sensitivity (0.1 fmol μL-1) of the prepared material for N-glycopeptides from standard protein digest samples. Moreover, it was further applied to simultaneous capturing of N- and O-glycopeptides from mouse liver protein digests. Compared to the commercially available zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) material, the number of glycoproteins corresponding to all N- and O-glycopeptides enriched with PDA-ADE@KCP was much more than that with ZIC-HILIC. Furthermore, PDA-ADE@KCP captured more O-glycopeptides than ZIC-HILIC, revealing its superior performance in O-glycopeptide enrichment. All these results indicated that the strategy holds immense potential in characterizing N- and O-intact glycopeptides in the field of proteomics.