General and Facile Coating of Single Cells via Mild Reduction.

Cell surface modification has been extensively studied to enhance the efficacy of cell therapy. Still, general accessibility and versatility are remaining challenges to meet the increasing demand for cell-based therapy. Herein, we present a facile and universal cell surface modification method that involves mild reduction of disulfide bonds in cell membrane protein to thiol groups. The reduced cells are successfully coated with biomolecules, polymers, and nanoparticles for an assortment of applications, including rapid cell assembly, in vivo cell monitoring, and localized cell-based drug delivery. No adverse effect on cellular morphology, viability, proliferation, and metabolism is observed. Furthermore, simultaneous coating with polyethylene glycol and dexamethasone-loaded nanoparticles facilitates enhanced cellular activities in mice, overcoming immune rejection.

Butyrated ManNAc analog improves protein expression in Chinese hamster ovary cells.

The chemical additive sodium butyrate (NaBu) has been applied in cell culture media as a direct and convenient method to increase the protein expression in Chinese hamster ovary (CHO) and other mammalian cells. In this study, we examined an alternative chemical additive, 1,3,4-O-Bu3 ManNAc, for its effect on recombinant protein production in CHO. Supplementation with 1,3,4-O-Bu3 ManNAc for two stable CHO cell lines, expressing human erythropoietin or IgG, enhanced protein expression for both products with negligible impact on cell growth, viability, glucose utilization, and lactate accumulation. In contrast, sodium butyrate treatment resulted in a ∼20% decrease in maximal viable cell density and ∼30% decrease in cell viability at the end of cell cultures compared to untreated or 1,3,4-O-Bu3 ManNAc treated CHO cell lines for both products. While NaBu treatment enhanced product yields more than the 1,3,4-O-Bu3 ManNAc treatment, the NaBu treated cells also exhibited higher levels of caspase 3 positive cells using microscopy analysis. Furthermore, the mRNA levels of four cell apoptosis genes (Cul2, BAK, BAX, and BCL2L11) were up-regulated more in sodium butyrate treated wild-type, erythropoietin, or IgG expressing CHO-K1 cell lines while most of the mRNA levels of apoptosis genes in 1,3,4-O-Bu3 ManNAc treated cell lines remained equal or increased only slightly compared to the levels in untreated CHO cell lines. Finally, lectin blot analysis revealed that the 1,3,4-O-Bu3 ManNAc-treated cells displayed higher relative sialylation levels on recombinant EPO, consistent with the effect of the ManNAc component of this additive, compared to control while NaBu treatment led to lower sialylation levels than control, or 1,3,4-O-Bu3 ManNAc-treatment. These findings demonstrate that 1,3,4-O-Bu3 ManNAc has fewer negative effects on cell cytotoxicity and apoptosis, perhaps as a result of a more deliberate uptake and release of the butyrate compounds, while simultaneously increasing the expression of multiple recombinant proteins, and improving the glycosylation characteristics when applied at comparable molarity levels to NaBu. Thus, 1,3,4-O-Bu3 ManNAc represents a highly promising media additive alternative in cell culture for improving protein yields without sacrificing cell mass and product quality in future bioproduction processes.

Pharmacological, Physiochemical, and Drug-Relevant Biological Properties of Short Chain Fatty Acid Hexosamine Analogues Used in Metabolic Glycoengineering.

In this study, we catalog structure activity relationships (SAR) of several short chain fatty acid (SCFA)-modified hexosamine analogues used in metabolic glycoengineering (MGE) by comparing in silico and experimental measurements of physiochemical properties important in drug design. We then describe the impact of these compounds on selected biological parameters that influence the pharmacological properties and safety of drug candidates by monitoring P-glycoprotein (Pgp) efflux, inhibition of cytochrome P450 3A4 (CYP3A4), hERG channel inhibition, and cardiomyocyte cytotoxicity. These parameters are influenced by length of the SCFAs (e.g., acetate vs n-butyrate), which are added to MGE analogues to increase the efficiency of cellular uptake, the regioisomeric arrangement of the SCFAs on the core sugar, the structure of the core sugar itself, and by the type of N-acyl modification (e.g., N-acetyl vs N-azido). By cataloging the influence of these SAR on pharmacological properties of MGE analogues, this study outlines design considerations for tuning the pharmacological, physiochemical, and the toxicological parameters of this emerging class of small molecule drug candidates.

Glycoengineering of Esterase Activity through Metabolic Flux-Based Modulation of Sialic Acid.

This report describes the metabolic glycoengineering (MGE) of intracellular esterase activity in human colon cancer (LS174T) and Chinese hamster ovary (CHO) cells. In silico analysis of carboxylesterases CES1 and CES2 suggested that these enzymes are modified with sialylated N-glycans, which are proposed to stabilize the active multimeric forms of these enzymes. This premise was supported by treating cells with butanolylated ManNAc to increase sialylation, which in turn increased esterase activity. By contrast, hexosamine analogues not targeted to sialic acid biosynthesis (e.g., butanoylated GlcNAc or GalNAc) had minimal impact. Measurement of mRNA and protein confirmed that esterase activity was controlled through glycosylation and not through transcription or translation. Azide-modified ManNAc analogues widely used in MGE also enhanced esterase activity and provided a way to enrich targeted glycoengineered proteins (such as CES2), thereby providing unambiguous evidence that the compounds were converted to sialosides and installed into the glycan structures of esterases as intended. Overall, this study provides a pioneering example of the modulation of intracellular enzyme activity through MGE, which expands the value of this technology from its current status as a labeling strategy and modulator of cell surface biological events.

A novel sugar analog enhances sialic acid production and biotherapeutic sialylation in CHO cells.

A desirable feature of many therapeutic glycoprotein production processes is to maximize the final sialic acid content. In this study, the effect of applying a novel chemical analog of the sialic acid precursor N-acetylmannosamine (ManNAc) on the sialic acid content of cellular proteins and a model recombinant glycoprotein, erythropoietin (EPO), was investigated in CHO-K1 cells. By introducing the 1,3,4-O-Bu3 ManNAc analog at 200-300 µM into cell culture media, the intracellular sialic acid content of EPO-expressing cells increased ∼8-fold over untreated controls while the level of cellular sialylated glycoconjugates increased significantly as well. For example, addition of 200-300 µM 1,3,4-O-Bu3 ManNAc resulted in >40% increase in final sialic acid content of recombinant EPO, while natural ManNAc at ∼100 times higher concentration of 20 mM produced a less profound change in EPO sialylation. Collectively, these results indicate that butyrate-derivatization of ManNAc improves the capacity of cells to incorporate exogenous ManNAc into the sialic acid biosynthetic pathway and thereby increase sialylation of recombinant EPO and other glycoproteins. This study establishes 1,3,4-O-Bu3 ManNAc as a novel chemical supplement to improve glycoprotein quality and sialylation levels at concentrations orders of magnitude lower than alternative approaches. Biotechnol. Bioeng. 2017;114: 1899-1902. © 2017 Wiley Periodicals, Inc.

Identification of sialylated glycoproteins from metabolically oligosaccharide engineered pancreatic cells.

In this study, we investigated the use of metabolic oligosaccharide engineering and bio-orthogonal ligation reactions combined with lectin microarray and mass spectrometry to analyze sialoglycoproteins in the SW1990 human pancreatic cancer line. Specifically, cells were treated with the azido N-acetylmannosamine analog, 1,3,4-Bu3ManNAz, to label sialoglycoproteins with azide-modified sialic acids. The metabolically labeled sialoglyproteins were then biotinylated via the Staudinger ligation, and sialoglycopeptides containing azido-sialic acid glycans were immobilized to a solid support. The peptides linked to metabolically labeled sialylated glycans were then released from sialoglycopeptides and analyzed by mass spectrometry; in parallel, the glycans from azido-sialoglycoproteins were characterized by lectin microarrays. This method identified 75 unique N-glycosite-containing peptides from 55 different metabolically labeled sialoglycoproteins of which 42 were previously linked to cancer in the literature. A comparison of two of these glycoproteins, LAMP1 and ORP150, in histological tumor samples showed overexpression of these proteins in the cancerous tissue demonstrating that our approach constitutes a viable strategy to identify and discover sialoglycoproteins associated with cancer, which can serve as biomarkers for cancer diagnosis or targets for therapy.

Metabolic glycoengineering bacteria for therapeutic, recombinant protein, and metabolite production applications.

Metabolic glycoengineering is a specialization of metabolic engineering that focuses on using small molecule metabolites to manipulate biosynthetic pathways responsible for oligosaccharide and glycoconjugate production. As outlined in this article, this technique has blossomed in mammalian systems over the past three decades but has made only modest progress in prokaryotes. Nevertheless, a sufficient foundation now exists to support several important applications of metabolic glycoengineering in bacteria based on methods to preferentially direct metabolic intermediates into pathways involved in lipopolysaccharide, peptidoglycan, teichoic acid, or capsule polysaccharide production. An overview of current applications and future prospects for this technology are provided in this report.

Metabolic glycoengineering sensitizes drug-resistant pancreatic cancer cells to tyrosine kinase inhibitors erlotinib and gefitinib.

Metastatic human pancreatic cancer cells (the SW1990 line) that are resistant to the EGFR-targeting tyrosine kinase inhibitor drugs (TKI) erlotinib and gefitinib were treated with 1,3,4-O-Bu3ManNAc, a 'metabolic glycoengineering' drug candidate that increased sialylation by ∼2-fold. Consistent with genetic methods previously used to increase EGFR sialylation, this small molecule reduced EGF binding, EGFR transphosphorylation, and downstream STAT activation. Significantly, co-treatment with both the sugar pharmacophore and the existing TKI drugs resulted in strong synergy, in essence re-sensitizing the SW1990 cells to these drugs. Finally, 1,3,4-O-Bu3ManNAz, which is the azido-modified counterpart to 1,3,4-O-Bu3ManNAc, provided a similar benefit thereby establishing a broad-based foundation to extend a 'metabolic glycoengineering' approach to clinical applications.

Integration of the transcriptome and glycome for identification of glycan cell signatures.

Abnormalities in glycan biosynthesis have been conclusively linked to many diseases but the complexity of glycosylation has hindered the analysis of glycan data in order to identify glycoforms contributing to disease. To overcome this limitation, we developed a quantitative N-glycosylation model that interprets and integrates mass spectral and transcriptomic data by incorporating key glycosylation enzyme activities. Using the cancer progression model of androgen-dependent to androgen-independent Lymph Node Carcinoma of the Prostate (LNCaP) cells, the N-glycosylation model identified and quantified glycan structural details not typically derived from single-stage mass spectral or gene expression data. Differences between the cell types uncovered include increases in H(II) and Le(y) epitopes, corresponding to greater activity of α2-Fuc-transferase (FUT1) in the androgen-independent cells. The model further elucidated limitations in the two analytical platforms including a defect in the microarray for detecting the GnTV (MGAT5) enzyme. Our results demonstrate the potential of systems glycobiology tools for elucidating key glycan biomarkers and potential therapeutic targets. The integration of multiple data sets represents an important application of systems biology for understanding complex cellular processes.

Metabolic flux increases glycoprotein sialylation: implications for cell adhesion and cancer metastasis.

This study reports a global glycoproteomic analysis of pancreatic cancer cells that describes how flux through the sialic acid biosynthetic pathway selectively modulates a subset of N-glycosylation sites found within cellular proteins. These results provide evidence that sialoglycoprotein patterns are not determined exclusively by the transcription of biosynthetic enzymes or the availability of N-glycan sequons; instead, bulk metabolic flux through the sialic acid pathway has a remarkable ability to increase the abundance of certain sialoglycoproteins while having a minimal impact on others. Specifically, of 82 glycoproteins identified through a mass spectrometry and bioinformatics approach, ≈ 31% showed no change in sialylation, ≈ 29% exhibited a modest increase, whereas ≈ 40% experienced an increase of greater than twofold. Increased sialylation of specific glycoproteins resulted in changes to the adhesive properties of SW1990 pancreatic cancer cells (e.g. increased CD44-mediated adhesion to selectins under physiological flow and enhanced integrin-mediated cell mobility on collagen and fibronectin). These results indicate that cancer cells can become more aggressively malignant by controlling the sialylation of proteins implicated in metastatic transformation via metabolic flux.

A dual-acting DNASE1/DNASE1L3 biologic prevents autoimmunity and death in genetic and induced lupus models.

A defining feature of systemic lupus erythematosus (SLE) is loss of tolerance to self-DNA, and DNASE1L3 deficiency, the main enzyme responsible for chromatin degradation in blood, is also associated with SLE. This association includes an ultra-rare pediatric population with DNASE1L3 deficiency who develop SLE, adult patients with loss of function variants of DNASE1L3 who are at a higher risk for SLE, and patients with sporadic SLE who have neutralizing autoantibodies to DNASE1L3. To mitigate the pathogenic effects of inherited and acquired DNASE1L3 deficiencies, we engineered a long-acting enzyme biologic with dual DNASE1/DNASE1L3 activity that is resistant to DNASE1 and DNASE1L3 inhibitors. Notably, we found that the biologic prevented the development of lupus in Dnase1-/-/Dnase1L3-/- double knockout mice and rescued animals from death in pristane-induced lupus. Finally, we confirmed that the human isoform of the enzyme biologic was not recognized by autoantibodies in SLE and efficiently degrades genomic and mitochondrial cell free DNA, as well as microparticle DNA, in SLE plasma. Our findings suggest that autoimmune diseases characterized by aberrant DNA accumulation, such as SLE, can be effectively treated with a replacement DNASE tailored to bypass pathogenic mechanisms, both genetic and acquired, that restrict DNASE1L3 activity.

Mass spectrometric analysis of sialylated glycans with use of solid-phase labeling of sialic acids.

The analysis of sialylated glycans is critical for understanding the role of sialic acid in normal biological processes as well as in disease. However, the labile nature of sialic acid typically renders routine analysis of this monosaccharide by mass spectrometric methods difficult. To overcome this difficulty we pursued derivatization methodologies, extending established acetohydrazide approaches to aniline-based methods, and finally to optimized p-toluidine derivatization. This new quantitative glycoform profiling method with use of MALDI-TOF in positive ion mode was validated by first comparing N-glycans isolated from fetuin and serum and was then exploited to analyze the effects of increased metabolic flux through the sialic acid pathway in SW1990 pancreatic cancer cells by using a colabeling strategy with light and heavy toluidine. The latter results established that metabolic flux, in a complementary manner to the more well-known impact of sialyltransferase expression, can critically modulate the sialylation of specific glycans while leaving others virtually unchanged.

Improving Schwann Cell Differentiation from Human Adipose Stem Cells with Metabolic Glycoengineering.

Schwann cells (SCs) are myelinating cells that promote peripheral nerve regeneration. When nerve lesions form, SCs are destroyed, ultimately hindering nerve repair. The difficulty in treating nerve repair is exacerbated due to SC's limited and slow expansion capacity. Therapeutic use of adipose-derived stem cells (ASCs) is emerging in combating peripheral nerve injury due to these cells' SC differentiation capability and can be harvested easily in large numbers. Despite ASC's therapeutic potential, their transdifferentiation period typically takes more than two weeks. In this study, we demonstrate that metabolic glycoengineering (MGE) technology enhances ASC differentiation into SCs. Specifically, the sugar analog Ac5ManNTProp (TProp), which modulates cell surface sialylation, significantly improved ASC differentiation with upregulated SC protein S100ß and p75NGFR expression and elevated the neurotrophic factors nerve growth factor beta (NGFß) and glial cell-line-derived neurotrophic factor (GDNF). TProp treatment remarkably reduced the SC transdifferentiation period from about two weeks to two days in vitro, which has the potential to improve neuronal regeneration and facilitate future use of ASCs in regenerative medicine.

Protocol Considerations for In Vitro Metabolic Glycoengineering of Non-Natural Glycans.

Metabolic glycoengineering (MGE) refers to a technique where non-natural monosaccharide analogs are introduced into living biological systems. Once inside a cell, these compounds intercept a targeted biosynthetic glycosylation pathway and in turn are metabolically incorporated into cell-surface-displayed oligosaccharides, where they can modulate a host of biological activities or be exploited as tags for bioorthogonal and chemoselective ligation reactions. Over the past decade, azido-modified monosaccharides have become the go-to analogs for MGE; at the same time, analogs with novel chemical functionalities continue to be developed. Therefore, one emphasis of this article is to describe a general approach for analog selection and then provide protocols to ensure safe and efficacious analog usage by cells. Once cell-surface glycans have been successfully remodeled by MGE methodology, the stage is set for probing changes to the myriad cellular responses modulated by these versatile molecules. This manuscript concludes by detailing how one of these detection methods-flow cytometry-can be successfully utilized to quantify MGE analog incorporation and set the stage for numerous follow-up applications. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Incubation of cells with sugar analogs Support Protocol: Routine growth and maintenance of Jurkat cells Basic Protocol 2: Cell viability assays Basic Protocol 3: Periodate-resorcinol assay to measure analog uptake and incorporation into metabolic pathways Basic Protocol 4: Quantitation of cell-surface glycoconjugates.

Anticancer Properties of Hexosamine Analogs Designed to Attenuate Metabolic Flux through the Hexosamine Biosynthetic Pathway.

Altered cellular metabolism is a hallmark of cancer pathogenesis and progression; for example, a near-universal feature of cancer is increased metabolic flux through the hexosamine biosynthetic pathway (HBP). This pathway produces uridine diphosphate N-acetylglucosamine (UDP-GlcNAc), a potent oncometabolite that drives multiple facets of cancer progression. In this study, we synthesized and evaluated peracetylated hexosamine analogs designed to reduce flux through the HBP. By screening a panel of analogs in pancreatic cancer and glioblastoma multiform (GBM) cells, we identified Ac4Glc2Bz─a benzyl-modified GlcNAc mimetic─as an antiproliferative cancer drug candidate that down-regulated oncogenic metabolites and reduced GBM cell motility at concentrations non-toxic to non-neoplastic cells. More specifically, the growth inhibitory effects of Ac4Glc2Bz were linked to reduced levels of UDP-GlcNAc and concomitant decreases in protein O-GlcNAc modification in both pancreatic cancer and GBM cells. Targeted metabolomics analysis in GBM cells showed that Ac4Glc2Bz disturbed glucose metabolism, amino acid pools, and nucleotide precursor biosynthesis, consistent with reduced proliferation and other anti-oncogenic properties of this analog. Furthermore, Ac4Glc2Bz reduced the invasion, migration, and stemness of GBM cells. Importantly, normal metabolic functions mediated by UDP-GlcNAc were not disrupted in non-neoplastic cells, including maintenance of endogenous levels of O-GlcNAcylation with no global disruption of N-glycan production. Finally, a pilot in vivo study showed that a potential therapeutic window exists where animals tolerated 5- to 10-fold higher levels of Ac4Glc2Bz than projected for in vivo efficacy. Together, these results establish GlcNAc analogs targeting the HBP through salvage mechanisms as a new therapeutic approach to safely normalize an important facet of aberrant glucose metabolism associated with cancer.

Metabolic oligosaccharide engineering with N-Acyl functionalized ManNAc analogs: cytotoxicity, metabolic flux, and glycan-display considerations.

Metabolic oligosaccharide engineering (MOE) is a maturing technology capable of modifying cell surface sugars in living cells and animals through the biosynthetic installation of non-natural monosaccharides into the glycocalyx. A particularly robust area of investigation involves the incorporation of azide functional groups onto the cell surface, which can then be further derivatized using "click chemistry." While considerable effort has gone into optimizing the reagents used for the azide ligation reactions, less optimization of the monosaccharide analogs used in the preceding metabolic incorporation steps has been done. This study fills this void by reporting novel butanoylated ManNAc analogs that are used by cells with greater efficiency and less cytotoxicity than the current "gold standard," which are peracetylated compounds such as Ac4 ManNAz. In particular, tributanoylated, N-acetyl, N-azido, and N-levulinoyl ManNAc analogs with the high flux 1,3,4-O-hydroxyl pattern of butanoylation were compared with their counterparts having the pro-apoptotic 3,4,6-O-butanoylation pattern. The results reveal that the ketone-bearing N-levulinoyl analog 3,4,6-O-Bu3 ManNLev is highly apoptotic, and thus is a promising anti-cancer drug candidate. By contrast, the azide-bearing analog 1,3,4-O-Bu3 ManNAz effectively labeled cellular sialoglycans at concentrations ∼3- to 5-fold lower (e.g., at 12.5-25 µM) than Ac4 ManNAz (50-150 µM) and exhibited no indications of apoptosis even at concentrations up to 400 µM. In summary, this work extends emerging structure activity relationships that predict the effects of short chain fatty acid modified monosaccharides on mammalian cells and also provides a tangible advance in efforts to make MOE a practical technology for the medical and biotechnology communities.

Extracellular and intracellular esterase processing of SCFA-hexosamine analogs: implications for metabolic glycoengineering and drug delivery.

This report provides a synopsis of the esterase processing of short chain fatty acid (SCFA)-derivatized hexosamine analogs used in metabolic glycoengineering by demonstrating that the extracellular hydrolysis of these compounds is comparatively slow (e.g., with a t(1/2) of ∼4 h to several days) in normal cell culture as well as in high serum concentrations intended to mimic in vivo conditions. Structure-activity relationship (SAR) analysis of common sugar analogs revealed that O-acetylated and N-azido ManNAc derivatives were more refractory against extracellular inactivation by FBS than their butanoylated counterparts consistent with in silico docking simulations of Ac(4)ManNAc and Bu(4)ManNAc to human carboxylesterase 1 (hCE1). By contrast, all analogs tested supported increased intracellular sialic acid production within 2h establishing that esterase processing once the analogs are taken up by cells is not rate limiting.

Glycoengineering human neural stem cells (hNSCs) for adhesion improvement using a novel thiol-modified N-acetylmannosamine (ManNAc) analog.

This study sets the stage for the therapeutic use of Ac5ManNTProp, an N-acetylmannosamine (ManNAc) analog that installs thiol-modified sialoglycans onto the surfaces of human neural stem cells (hNSC). First, we compared hNSC adhesion to the extracellular matrix (ECM) proteins laminin, fibronectin, and collagen and found preferential adhesion and concomitant changes to cell morphology and cell spreading for Ac5ManNTProp-treated cells to laminin, compared to fibronectin where there was a modest response, and collagen where there was no observable increase. PCR array transcript analysis identified several classes of cell adhesion molecules that responded to combined Ac5ManNTProp treatment and hNSC adhesion to laminin. Of these, we focused on integrin α6ß1 expression, which was most strongly upregulated in analog-treated cells incubated on laminin. We also characterized downstream responses including vinculin display as well as the phosphorylation of focal adhesion kinase (FAK) and extracellular signal-related kinase (ERK). In these experiments, Ac5ManNTProp more strongly induced all tested biological endpoints compared to Ac5ManNTGc, showing that the single methylene unit that structurally separates the two analogs finely tunes biological responses. Together, the concerted modulation of multiple pro-regenerative activities through Ac5ManNTProp treatment, in concert with crosstalk with ECM components, lays a foundation for using our metabolic glycoengineering approach to treat neurological disorders by favorably modulating endpoints that contribute to the viability of transplanted NSCs.

Strategies for Glycoengineering Therapeutic Proteins.

Almost all therapeutic proteins are glycosylated, with the carbohydrate component playing a long-established, substantial role in the safety and pharmacokinetic properties of this dominant category of drugs. In the past few years and moving forward, glycosylation is increasingly being implicated in the pharmacodynamics and therapeutic efficacy of therapeutic proteins. This article provides illustrative examples of drugs that have already been improved through glycoengineering including cytokines exemplified by erythropoietin (EPO), enzymes (ectonucleotide pyrophosphatase 1, ENPP1), and IgG antibodies (e.g., afucosylated Gazyva®, Poteligeo®, Fasenra™, and Uplizna®). In the future, the deliberate modification of therapeutic protein glycosylation will become more prevalent as glycoengineering strategies, including sophisticated computer-aided tools for "building in" glycans sites, acceptance of a broad range of production systems with various glycosylation capabilities, and supplementation methods for introducing non-natural metabolites into glycosylation pathways further develop and become more accessible.

A versatile design platform for glycoengineering therapeutic antibodies.

Manipulation of glycosylation patterns, i.e., glycoengineering, is incorporated in the therapeutic antibody development workflow to ensure clinical safety, and this approach has also been used to modulate the biological activities, functions, or pharmacological properties of antibody drugs. Whereas most existing glycoengineering strategies focus on the canonical glycans found in the constant domain of immunoglobulin G (IgG) antibodies, we report a new strategy to leverage the untapped potential of atypical glycosylation patterns in the variable domains, which naturally occur in 15% to 25% of IgG antibodies. Glycosylation sites were added to the antigen-binding regions of two functionally divergent, interleukin-2-binding monoclonal antibodies. We used computational tools to rationally install various N-glycosylation consensus sequences into the antibody variable domains, creating "glycovariants" of these molecules. Strikingly, almost all the glycovariants were successfully glycosylated at their newly installed N-glycan sites, without reduction of the antibody's native function. Importantly, certain glycovariants exhibited modified activities compared to the parent antibody, showing the potential of our glycoengineering strategy to modulate biological function of antibodies involved in multi-component receptor systems. Finally, when coupled with a high-flux sialic acid precursor, a glycovariant with two installed glycosylation sites demonstrated superior in vivo half-life. Collectively, these findings validate a versatile glycoengineering strategy that introduces atypical glycosylation into therapeutic antibodies in order to improve their efficacy and, in certain instances, modulate their activity early in the drug development process.