Modulating antibody effector functions by Fc glycoengineering

IgG N-glycosylation contributes to different severities of insulin resistance: implications for 3P medical approaches

Background

Reliable biomarkers capturing immunometabolic processes in insulin resistance (IR) remain limited. IgG N-glycosylation modulates immune responses and reflects metabolic disorders, yet its role in IR remains unclear. This study investigated its potential for early detection, risk stratification, and targeted prevention within the framework of predictive, preventive, and personalised medicine (PPPM/3PM).

Methods

A total of 313 participants were categorized into three groups based on the homeostatic model assessment for insulin resistance (HOMA-IR): insulin-sensitive (HOMA-IR < 2.69 without diabetes, n = 75), mild IR (HOMA-IR ≥ 2.69 without diabetes, n = 155), and severe IR (HOMA-IR ≥ 2.69 with type 2 diabetes, n = 83). Canonical correlation analysis was conducted to explore the overall relationship between IgG N-glycosylation and IR-related inflammation, indicated by tumour necrosis factor-α, interleukin- 6, C-reactive protein, and adiponectin. Mediation analysis was performed to evaluate the effect of IgG N-glycans on IR. Ordinal logistic regression was used to assess the association between IgG N-glycans and IR severity, with discriminative power evaluated using receiver operating characteristic curves.

Results

Pro-inflammatory IgG N-glycoforms, characterized by reduced sialylation and galactosylation, along with increased bisecting N-acetylglucosamine, were observed as IR severity increased. IgG N-glycosylation significantly correlated with inflammatory markers in the insulin-sensitive (r = 0.599, p < 0.05), mild (r = 0.461, p < 0.05), and severe (r = 0.666, p < 0.01) IR groups. IgG N-glycosylation significantly influenced IR (β = 0.406) partially via modulation of inflammation. Increased glycoforms FA2[6]G1 (OR: 0.86, 95% CI: 0.78-0.96) and A2G2S2 (OR: 0.88, 95% CI: 0.82-0.94) were associated with a lower IR risk, with respective area under the curves (AUCs) of 0.752, 0.683, and 0.764 for the insulin sensitive, mild, and severe IR groups.

Conclusions

IgG N-glycosylation contributes to IR by modulating inflammatory responses. Glycoforms FA2[6]G1 and A2G2S2 emerge as protective biomarkers, offering potential for predicting and preventing IR through primary prevention strategies within the PPPM framework.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-025-00410-x.

Future of bNAbs in HIV Treatment

PURPOSE OF REVIEW

Broadly neutralizing antibodies (bNAbs) represent a novel approach to HIV treatment, prevention, and cure strategies. As research advances, the clinical application of bNAbs continues to evolve. This review explores the potential role of bNAbs in HIV management, addressing their mechanisms of action, current limitations, and future directions.

RECENT FINDINGS

Recent studies have demonstrated that bNAbs can effectively neutralize a broad range of HIV strains by targeting conserved epitopes on the viral envelope. Clinical trials have shown that bNAb combinations can maintain viral supression in the absence of antiretroviral therapy (ART), though pre-existing resistance remains a major challenge. Strategies such as Fc engineering and alternative delivery mechanisms (e.g., AAV, mRNA, DNA) are being explored to enhance bNAb efficacy and durability. Despite promising data, bNAbs have not yet demonstrated superior effectiveness compared to existing ART or pre-exposure prophylaxis (PrEP) options. While bNAbs offer exciting possibilities for long-acting HIV therapy, their widespread use is limited by logistical challenges, high production costs, and pre-existing viral resistance. The future of bNAbs may lie in combination strategies with small-molecule antiretrovirals in maintenance strategies, genetic delivery systems, and vaccine-based approaches to induce endogenous bNAb production. Further research is needed to refine these strategies and determine the optimal role of bNAbs in HIV care.

Aberrant glycosylation patterns as potential biomarkers for diagnosis and disease progression in bullous pemphigoid

Objectives

Bullous pemphigoid (BP) is a prototypical autoimmune disease characterized by the production of autoantibodies against hemidesmosomal proteins BP180 and BP230. Aberrant glycosylation has emerged as a possible mechanism linked to the pathogenesis and progression of autoimmune diseases. However, the precise alterations in glycosylation in BP remain largely unknown. In this study, we explored the molecular mechanisms of abnormal glycosylation in BP pathogenesis.

Methods

We systematically investigated the glycosylation changes in serum, blister fluid, and saliva from BP patients using lectin microarray assays and lectin-based enzyme-linked immunosorbent assays.

Results

Our findings revealed increased glycosylation modifications of sialic acid, galactose, and fucose in serum proteins from BP patients, as well as enhanced fucosylation, galactosylation, and biantennary N-glycan glycosylation in blister fluid proteins. Notably, these abnormal modifications of monosaccharides correlated with the clinical indicators of BP. Furthermore, we observed that glycosylation patterns in saliva were associated with disease severity, suggesting their potential as valuable non-invasive diagnostic markers for BP.

Conclusion

These discoveries indicate that aberrant glycosylation patterns may provide insights into the pathogenesis of BP and serve as potential biomarkers for diagnosing and monitoring the disease.

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

This study investigated 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). 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. 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). 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.

An industrial-grade Nicotiana benthamiana line for the production of glycoproteins carrying fucose-free galactosylated N-glycans

β1,4-galactosylation is a typical human N-glycan formation with functional impact on proteins, particularly known for IgGs. Therefore, the expression of recombinant proteins with controlled galactosylation is an important quality parameter in the biotech industry. Here we describe the establishment of a plant-based expression platform for the manufacturing of recombinant proteins carrying β1,4-galactosylated N-glycans. A genome-edited Nicotiana benthamiana glycosylation mutant (NbXF-KO) that synthesizes conserved eukaryotic GnGn structures served as a template for further elongation toward β1,4-galactosylated N-glycans. A hybrid β1,4-galactosyltransferase gene that targets the enzyme to a post-Golgi compartment was introduced into the NbXF-KO genome without any additional foreign DNA sequence. The efficient generation of "marker-free" transgenic lines (NbXF-KOGal) was achieved by using a dual-vector strategy and visual screening procedures. Of note, a monoclonal antibody expressed in NbXF-KOGal exhibited up to 70 % galactosylated, fucose/xylose-free N-glycans, in a batch-to-batch consistent manner. Given recent findings attributing anti-inflammatory activities to nonfucosylated, galactosylated IgG, our results gain new significance.

Immunoglobulin G N-Glycome as a biomarker of mortality risk in Escherichia coli induced sepsis

Background

Sepsis is a life-threatening syndrome caused by an imbalance in the inflammatory response to an infection that can lead to a high mortality rate. Escherichia coli is a common pathogen that causes sepsis. The role of immunoglobulin G N-glycome in estimating the mortality in patients with sepsis remains unknown. This study aims to reveal the clinical application of immunoglobulin G N-glycome as a potentially novel biomarker to predict mortality risk in Escherichia coli-induced sepsis.

Methods

The serum immunoglobulin G N-glycome levels in 100 adult septic patient serum samples on the day of intensive care unit (ICU) admission, and 100 healthy volunteers were measured and analyzed. Immunoglobulin G N-glycome was compared with existing risk scores on predicting in-hospital death.

Results

We identified that the fucosylation level was significantly decreased in patients. Importantly, bisecting GlcNAc, sialylation, and galactosylation have different levels between sepsis and control groups. In addition, the AUC values of the SOFA score combined with GP4, GP5, and GP9 were 0.76 (95%CI: 0.61 to 0.90), 0.58 (95%CI: 0.40 to 0.7) and 0.57 (95%CI: 0.38 to 0.76). The AUC value of the SOFA score combined with GP4 and GP7 was 0.85 (95%CI: 0.76 to 0.93) in predicting in-hospital mortality in patients with sepsis.

Conclusions

Immunoglobulin G N-glycome concentrations at ICU admission are valuable for predicting the in-hospital mortality risk of patients with sepsis, suggesting that immunoglobulin G N-glycome may be a novel biomarker.

In Vitro Evaluation of Genetically Unmodified Ligand-Armed Allogeneic Natural Killer Cells to Treat EGFR-Positive Glioblastoma

Glioblastomas (GBMs) are lethal brain tumors in which EGFR gene amplification or mutation is frequently detected and is associated with poor prognosis. The standard of care is maximal resection followed by chemotherapy and radiation. Over the last twenty years, marginal improvements in patient survival have been achieved mainly through surgical techniques and the more accurate use of radiation. In this study, umbilical cord blood-derived and expanded human allogeneic natural killer (eNK) cells were pre-complexed to an Fc-engineered anti-EGFR monoclonal antibody (Pin-EGFR) to create Pin-EGFR-armed eNK cells. Pin-EGFR-armed eNK cells showed in vitro persistence of mAb anchoring. This arming process mediated specific, rapid and potent NK cell-redirected cytotoxicity against GBM cell lines and patient-derived cells in models consistent with the pathophysiological conditions of GBM. These results demonstrate the potential of Pin-EGFR-armed eNK cells to be an effective therapy against GBM cell lines in vitro. This product represents a promising strategy to directly target residual tumor tissue remaining at and beyond the resection margins immediately following GBM surgery to improve patient care.

Potent efficacy of an IgG-specific endoglycosidase against IgG-mediated pathologies

Endo-β-N-acetylglucosaminidases (ENGases) that specifically hydrolyze the Asn297-linked glycan on immunoglobulin G (IgG) antibodies, the major molecular determinant of fragment crystallizable (Fc) γ receptor (FcγR) binding, are exceedingly rare. All previously characterized IgG-specific ENGases are multi-domain proteins secreted as an immune evasion strategy by Streptococcus pyogenes strains. Here, using in silico analysis and mass spectrometry techniques, we identified a family of single-domain ENGases secreted by pathogenic corynebacterial species that exhibit strict specificity for IgG antibodies. By X-ray crystallographic and surface plasmon resonance analyses, we found that the most catalytically efficient IgG-specific ENGase family member recognizes both protein and glycan components of IgG. Employing in vivo models, we demonstrated the remarkable efficacy of this IgG-specific ENGase in mitigating numerous pathologies that rely on FcγR-mediated effector functions, including T and B lymphocyte depletion, autoimmune hemolytic anemia, and antibody-dependent enhancement of dengue disease, revealing its potential for treating and/or preventing a wide range of IgG-mediated diseases in humans.

2D-CEX-FcRn-MS to Study Structure/Function Relation of mAb Charge Variants

The automated elucidation of the interplay between monoclonal antibody (mAb) structure and function using two-dimensional liquid chromatography-mass spectrometry (2D-LC-MS) is reported. Charge variants, induced through forced degradation, are resolved by first-dimension (1D) cation-exchange chromatography (CEX) and subsequently collected in loops installed on a multiple heart-cutting valve prior to transfer to second-dimension (2D) neonatal crystallizable fragment receptor (FcRn) affinity chromatography coupled with MS. As such, binding affinity of the latter mAb variants can elegantly be assessed and a first glimpse of identity provided. To maximize MS sensitivity, charge variants are unfolded upon eluting from the 2D affinity column by postcolumn addition of a denaturing solution. Further structural details, i.e., modification sites and chain distribution, are unraveled by a multidimensional LC-MS (mD-LC-MS) setup incorporating 1D CEX and parallel online middle-up and bottom-up LC-MS analysis in the subsequent dimensions. Identified charge variants could be ranked according to their affinity for FcRn. Binding is predominantly impacted by heavy chain (HC) M253 oxidation and to a lesser extend, M429 oxidation. Oxidation of both HCs more drastically affects FcRn interaction compared to single-chain oxidation, and the more oxidation, the less binding. Other modifications, such as HC glycosylation, HC N385/390, and N326 deamidation or HC C-terminal processing, are not shown to affect binding. The streamlined platform is challenged against the established workflow involving offline collection of charge variants and structural and functional assessment by, respectively, LC-MS and enzyme-linked immunosorbent assay (ELISA). A decent correlation is demonstrated between the binding affinity measured with ELISA and 2D FcRn affinity chromatography. In addition, throughput is improved (7-fold), material requirements are substantially reduced (2 orders of magnitude), and sample preparation artifacts and loss are minimized. With the simultaneous determination of mAb structure and function, the current study takes the concept of multiattribute analysis to the next level, thereby contributing to the future development of safer and more effective antibody therapeutics.

Altered Spike Immunoglobulin G Fc N-Linked Glycans Are Associated With Hyperinflammatory State in Adult Coronavirus Disease 2019 and Multisystem Inflammatory Syndrome in Children

Background

Severe coronavirus disease 2019 (COVID-19) and multisystem inflammatory syndrome (MIS-C) are characterized by excessive inflammatory cytokines/chemokines. In adults, disease severity is associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific immunoglobulin G (IgG) Fc afucosylation, which induces proinflammatory cytokine secretion from innate immune cells. This study aimed to define spike IgG Fc glycosylation following SARS-CoV-2 infection in adults and children and following SARS-CoV-2 vaccination in adults and the relationships between glycan modifications and cytokines/chemokines.

Methods

We analyzed longitudinal (n = 146) and cross-sectional (n = 49) serum/plasma samples from adult and pediatric COVID-19 patients, MIS-C patients, adult vaccinees, and adult and pediatric controls. We developed methods for characterizing bulk and spike IgG Fc glycosylation by capillary electrophoresis and measured levels of 10 inflammatory cytokines/chemokines by multiplexed enzyme-linked immunosorbent assay.

Results

Spike IgG was more afucosylated than bulk IgG during acute adult COVID-19 and MIS-C. We observed an opposite trend following vaccination, but it was not significant. Spike IgG was more galactosylated and sialylated and less bisected than bulk IgG during adult COVID-19, with similar trends observed during pediatric COVID-19/MIS-C and following SARS-CoV-2 vaccination. Spike IgG glycosylation changed with time following adult COVID-19 or vaccination. Afucosylated spike IgG exhibited inverse and positive correlations with inflammatory markers in MIS-C and following vaccination, respectively; galactosylated and sialylated spike IgG inversely correlated with proinflammatory cytokines in adult COVID-19 and MIS-C; and bisected spike IgG positively correlated with inflammatory cytokines/chemokines in multiple groups.

Conclusions

We identified previously undescribed relationships between spike IgG glycan modifications and inflammatory cytokines/chemokines that expand our understanding of IgG glycosylation changes that may impact COVID-19 and MIS-C immunopathology.

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.

Bacterial glycoengineering: Cell-based and cell-free routes for producing biopharmaceuticals with customized glycosylation

Glycosylation plays a pivotal role in tuning the folding and function of proteins. Because most human therapeutic proteins are glycosylated, understanding and controlling glycosylation is important for the design, optimization, and manufacture of biopharmaceuticals. Unfortunately, natural eukaryotic glycosylation pathways are complex and often produce heterogeneous glycan patterns, making the production of glycoproteins with chemically precise and homogeneous glycan structures difficult. To overcome these limitations, bacterial glycoengineering has emerged as a simple, cost-effective, and scalable approach to produce designer glycoprotein therapeutics and vaccines in which the glycan structures are engineered to reduce heterogeneity and improve biological and biophysical attributes of the protein. Here, we discuss recent advances in bacterial cell-based and cell-free glycoengineering that have enabled the production of biopharmaceutical glycoproteins with customized glycan structures.

Altered spike IgG Fc N-linked glycans are associated with hyperinflammatory state in adult COVID and Multisystem Inflammatory Syndrome in Children

Background

Severe COVID and multisystem inflammatory syndrome (MIS-C) are characterized by excessive inflammatory cytokines/chemokines. In adults, disease severity is associated with SARS-CoV-2-specific IgG Fc afucosylation, which induces pro-inflammatory cytokine secretion from innate immune cells. This study aimed to define spike IgG Fc glycosylation following SARS-CoV-2 infection in adults and children and following SARS-CoV-2 vaccination in adults and the relationships between glycan modifications and cytokine/chemokine levels.

Methods

We analyzed longitudinal (n=146) and cross-sectional (n=49) serum/plasma samples from adult and pediatric COVID patients, MIS-C patients, adult vaccinees, and adult and pediatric healthy controls. We developed methods for characterizing bulk and spike IgG Fc glycosylation by capillary electrophoresis (CE) and measured levels of ten inflammatory cytokines/chemokines by multiplexed ELISA.

Results

Spike IgG were more afucosylated than bulk IgG during acute adult COVID and MIS-C. We observed an opposite trend following vaccination, but it was not significant. Spike IgG were more galactosylated and sialylated and less bisected than bulk IgG during adult COVID, with similar trends observed during pediatric COVID/MIS-C and following SARS-CoV-2 vaccination. Spike IgG glycosylation changed with time following adult COVID or vaccination. Afucosylated spike IgG exhibited inverse and positive correlations with inflammatory markers in MIS-C and following vaccination, respectively; galactosylated and sialylated spike IgG inversely correlated with pro-inflammatory cytokines in adult COVID and MIS-C; and bisected spike IgG positively correlated with inflammatory cytokines/chemokines in multiple groups.

Conclusions

We identified previously undescribed relationships between spike IgG glycan modifications and inflammatory cytokines/chemokines that expand our understanding of IgG glycosylation changes that may impact COVID and MIS-C immunopathology.

Human gut microbes express functionally distinct endoglycosidases to metabolize the same N-glycan substrate

Bacteroidales (syn. Bacteroidetes) are prominent members of the human gastrointestinal ecosystem mainly due to their efficient glycan-degrading machinery, organized into gene clusters known as polysaccharide utilization loci (PULs). A single PUL was reported for catabolism of high-mannose (HM) N-glycan glyco-polypeptides in the gut symbiont Bacteroides thetaiotaomicron, encoding a surface endo-β-N-acetylglucosaminidase (ENGase), BT3987. Here, we discover an ENGase from the GH18 family in B. thetaiotaomicron, BT1285, encoded in a distinct PUL with its own repertoire of proteins for catabolism of the same HM N-glycan substrate as that of BT3987. We employ X-ray crystallography, electron microscopy, mass spectrometry-based activity measurements, alanine scanning mutagenesis and a broad range of biophysical methods to comprehensively define the molecular mechanism by which BT1285 recognizes and hydrolyzes HM N-glycans, revealing that the stabilities and activities of BT1285 and BT3987 were optimal in markedly different conditions. BT1285 exhibits significantly higher affinity and faster hydrolysis of poorly accessible HM N-glycans than does BT3987. We also find that two HM-processing endoglycosidases from the human gut-resident Alistipes finegoldii display condition-specific functional properties. Altogether, our data suggest that human gut microbes employ evolutionary strategies to express distinct ENGases in order to optimally metabolize the same N-glycan substrate in the gastroinstestinal tract.

Pharmacokinetic Analyses of a Lipid Nanoparticle-Encapsulated mRNA-Encoded Antibody against Rift Valley Fever Virus

Rift Valley fever virus (RVFV) could cause an emergency illness characterized by fever, muscle pain, and even death in humans or ruminants. However, there are no approved antiviral drugs that prevent or treat RVFV infection. While therapeutic antibodies have shown promising potential for prevention or treatment in several studies, many studies are ongoing, especially in the field of infectious diseases. Among these studies, the mRNA-LNP platform shows great potential for application, following the COVID-19 pandemic. Previously, we have obtained a neutralizing antibody against RVFV, which was named A38 protein and verified to have a high binding and neutralization ability. In this study, we aimed to identify an effectively optimized sequence and expressed the prioritized mRNA-encoded antibody in vitro. Notably, we effectively expressed mRNA-encoded protein and used the mRNA-LNP platform to generate A38-mRNA-LNP. Pharmacokinetic experiments were conducted in vivo and set up in two groups of mRNA-A38 group and A38 protein group, which were derived from mRNA-LNP and plasmid DNA-expressed proteins, respectively. A38-mRNA-LNPs were administrated by intramuscular injection, A38 proteins were administrated by intravenous administration, and their unique ability to maintain long-lasting protein concentrations by mRNA-encoded protein was demonstrated with the mRNA-encoded protein providing a longer circulating half-life compared to injection of the free A38 protein. These preclinical data on the mRNA-encoded antibody highlighted its potential to prevent infectious diseases in the future.