Search Results (19)

Antibodies are a cornerstone of the adaptive immune response, serving as key defenders against viral infections; however, they can also act as a double-edged sword, contributing to immune-mediated pathologies. This review advances a “Yin-Yang” framework to integrate the dual activities of antibodies. The protective ‘Yin’ functions are driven by high-affinity antibodies generated through processes like somatic hypermutation and class-switch recombination. These antibodies execute viral neutralization, activate the complement system, and engage Fc receptors (FcRs) to drive antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis. These mechanisms form the immunological basis of effective vaccines, which aim to elicit durable and functionally specialized antibody isotypes like IgG and mucosal IgA. Conversely, the pathogenic ‘Yang’ of the response can be detrimental. This includes antibody-dependent enhancement (ADE) of infection, notably observed with flaviviruses, and the development of autoimmunity through mechanisms like molecular mimicry and bystander activation, which can lead to conditions such as multiple sclerosis and Guillain-Barré Syndrome. The balance between protection and pathology is tipped by a confluence of factors. These include viral evasion strategies like antigenic mutation and glycan shielding, as well as host-based determinants such as genetic polymorphisms in FcRs, immune history, and the gut microbiome. Understanding these molecular determinants informs the rational design of next-generation interventions. Promising strategies, such as Fc-region glyco-engineering and the design of tolerogenic vaccines, aim to selectively promote protective functions while minimizing pathological risks, offering a clear path forward in combating viral threats. Full article

Glycosylation plays a pivotal role in regulating the functions and immunogenicity of antigens. Targeting the receptor-binding domain (RBD) of the spike protein (S protein) of SARS-CoV-2, we examined the impact of different glycoforms on RBD antigen immunogenicity and the underlying mechanisms. IgG-specific antibody titers and pseudovirus neutralization were compared in mice immunized with RBD antigens bearing different glycoforms, which were prepared using glycoengineering-capable Pichia pastoris and mammalian cell expression systems with distinct glycosylation pathways. The glycosylation impacted the surface charges of the RBD antigen, and influenced its adsorption onto alum. This may further lead to variations in the antigen’s immunogenicity. The high-mannose variant of the RBD antigen (H-MAN/RBD) expressed in wild-type Pichia pastoris induced significantly higher IgG-specific antibody titers and pseudovirus neutralization activity compared with the complex RBD variant (Complex/RBD) expressed in mammalian cells (293F) or glycoengineering-capable Pichia pastoris. The rate of H-MAN/RBD adsorption onto aluminum hydroxide (alum) adjuvant was significantly higher than that of Complex/RBD. It was assumed that H-MAN/RBD might carry more negative charges because of its phosphomannose-modified surfaces, leading to a higher rate of adsorption onto the positively charged alum and enhancing the immune response. To assess the impact of phosphomannose modification on antigen immunogenicity, a yeast strain was engineered to prepare a low-mannose RBD antigen (L-MAN/RBD); additionally, a yeast strain was constructed to generate a low-phosphomannose-modified RBD antigen (L-MAN-P/RBD). In conclusion, phosphomannose modification substantially enhanced the immunogenicity of RBD by altering the surface charges of the RBD antigen and facilitating its adsorption onto alum. These findings offer novel insights and strategies for vaccine design and immunotherapeutic approaches. Full article

Therapeutic antibodies with lambda light chains (λ-Abs) are underrepresented compared to kappa light chains (κ-Abs). Here, we evaluated two SARS-CoV-2-specific monoclonal antibodies (mAbs) that exhibit high (P5C3) and low (H4) antigen binding as κ and λ variants. mAbs expressed in glycoengineered Nicotiana benthamiana did not show differences in expression levels, glycosylation, and antigen binding, while κ-Abs exhibited slightly increased thermodynamic stability over λ-Abs. SARS-CoV-2 neutralization and IgG-FcγR immune complex studies revealed increased activities of H4 IgG1κ compared to H4 IgG1λ, with no differences observed between P5C3 variants. Our results indicate that constant light chain variability and Ab specificity contribute to Ab features, a fact that should be considered in engineering therapeutics. Full article

Background: Recombinant monoclonal antibodies represent a vital category of biologics, constituting the largest class of molecules used to treat autoimmune disorders, cancers, rheumatoid arthritis, and other chronic conditions. The IgG1 subclass is the most potent among all the immunoglobulin gamma (IgG) antibodies, inducing Fc-related effector functions. N-linked glycan distribution of therapeutic IgG1s affects Fc-related effector functions such as CDC (complement-dependent cytotoxicity) and ADCC (antibody dependent cell-mediated cytotoxicity) biological activities and efficacy in vivo. Hence, as a critical quality attribute (CQA), the glycosylation profile of therapeutic IgG1s must be consistently preserved, which is primarily influenced by manufacturing process factors. In the era of biosimilars, it is challenging for biopharmaceutical manufacturers to not only obtain the desired glycan distribution consistently but also to meet the innovator molecule specifications as per the regulatory agencies. Methods: This study investigates the CHO fed-batch process parameters that affect the titer and terminal galactosylation of the TNF-α blocker-IgG1. It was hypothesized that galactose supplementation would enhance the galactosylation of TNF-α blocker-IgG1. Results: It was observed that such in-cultivation process shift does not affect cell culture parameters yet significantly enhances the galactosylation of TNF-α blocker-IgG1. Interestingly, the results indicate that supplementing D-galactose from the exponential phase of the CHO fed-batch process had the greatest effect on Fc galactosylation, increasing the amount of total galactosylated TNF-α blocker-IgG1 from 7.7% to 15.8%. Conclusions: Our results demonstrate a relatively easy and viable technique for cell culture engineering that is more appropriate for industrial production than costly in vitro glycoengineering. Full article

(1) Background: The currently circulating variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exhibits resistance to antibodies induced by vaccines. The World Health Organization recommended the use of monovalent XBB.1 sublineages (e.g., XBB.1.5) as an antigenic component in 2023. (2) Objective: In this study, we aimed to develop vaccines based on the XBB.1.5 receptor-binding domain (RBD) to combat the recently emerged SARS-CoV-2 XBB and JN.1 variants, as well as previously circulating variants. (3) Methods: Glycoengineered Pichia pastoris was utilized to produce a recombinant XBB.1.5 RBD protein with mammalian-like and fucose-free N-glycosylation. The XBB.1.5 RBD was mixed with Al(OH)₃:CpG adjuvants to prepare monovalent vaccines. Thereafter, the XBB.1.5 RBD was mixed with the Beta (B.1.351), Delta (B.1.617.2), or Omicron (BA.2) RBDs (1:1 ratio), along with Al(OH)₃:CpG, to prepare bivalent vaccines. BALB/c mice were immunized with the monovalent and bivalent vaccines. Neutralizing antibody titers were assessed via pseudovirus and authentic virus assays; humoral immune responses were analyzed by RBD-binding IgG subtypes. (4) Results: The monovalent vaccine induced higher neutralizing antibody titers against Delta, BA.2, XBB.1.5, and JN.1 compared to those in mice immunized solely with Al(OH)₃:CpG, as demonstrated by pseudovirus virus assays. The XBB.1.5/Delta RBD and XBB.1.5/Beta RBD-based bivalent vaccines provided potent protection against the BA.2, XBB.1.5, JN.1, and KP.2 variants, as well as the previously circulating Delta and Beta variants. All monovalent and bivalent vaccines induced high levels of RBD-binding IgG (IgG1, IgG2a, IgG2b, and IgG3) antibodies in mice, suggesting that they elicited robust humoral immune responses. The serum samples from mice immunized with the XBB.1.5 RBD-based and XBB.1.5/Delta RBD-based vaccines could neutralize the authentic XBB.1.16 virus. (5) Conclusions: The XBB.1.5/Beta and XBB.1.5/Delta RBD-based bivalent vaccines are considered as potential candidates for broad-spectrum vaccines against SARS-CoV-2 variants. Full article

Aflibercept is a therapeutic recombinant fusion protein comprising extracellular domains of human vascular endothelial growth factor receptors (VEGFRs) and IgG1-Fc. It is a highly glycosylated protein with five N-glycosylation sites that might impact it structurally and/or functionally. Aflibercept is produced in mammalian cells and exhibits large glycan heterogeneity, which hampers glycan-associated investigations. Here, we report the expression of aflibercept in a plant-based system with targeted N-glycosylation profiles. Nicotiana benthamiana-based glycoengineering resulted in the production of aflibercept variants carrying designed carbohydrates, namely, N-glycans with terminal GlcNAc and sialic acid residues, herein referred to as AFLI^GnGn and AFLI^Sia, respectively. Both variants were transiently expressed in unusually high amounts (2 g/kg fresh leaf material) in leaves and properly assembled to dimers. Mass spectrometric site-specific glycosylation analyses of purified aflibercept showed the presence of two to four glycoforms in a consistent manner. We also demonstrate incomplete occupancy of some glycosites. Both AFLI^GnGn and AFLI^Sia displayed similar binding potency to VEGF₁₆₅, with a tendency of lower binding to variants with increased sialylation. Collectively, we show the expression of functionally active aflibercept in significant amounts with controlled glycosylation. The results provide the basis for further studies in order to generate optimized products in the best-case scenario. Full article

Fc-glycosite-specific antibody–drug conjugation represents a promising direction for the preparation of site-specific antibody–drug conjugates (ADCs). In the present research, we conducted a systemic evaluation of two endoglycosidase-catalyzed chemoenzymatic glycoengineering technologies to prepare glycosite-specific ADCs. In the first two-step approach, the antibody was deglycosylated and then reglycosylated with a modified intact N-glycan oxazoline. In the second one-pot approach, antibodies were deglycosylated and simultaneously glycosylated with a functionalized disaccharide oxazoline. For the comprehensive evaluation, we first optimized and scaled-up the preparation of azido glycan oxazolines. Afterwards, we proved that the one-pot glycan-remodeling approach was efficient for all IgG subclasses. Subsequently, we assembled respective ADCS using two technology routes, with two different linker-payloads combinations, and performed systemic in vitro and in vivo evaluations. All the prepared ADCs achieved high homogeneity and illustrated excellent stability in buffers with minimum aggregates, and exceptional stability in rat serum. All ADCs displayed a potent killing of BT-474 breast cancer cells. Moving to the mouse study, the ADCs prepared from two technology routes displayed potent and similar efficacy in a BT-474 xenograft model, which was comparable to an FDA-approved ADC generated from random conjugation. These ADCs also demonstrated excellent safety and did not cause body weight loss at the tested dosages. Full article

Monoclonal therapeutic antibodies have revolutionized the treatment of cancer and other diseases. Fc engineering aims to enhance the effector functions or half-life of therapeutic antibodies by modifying their Fc regions. Recent advances in the Fc engineering of modern therapeutic antibodies can be considered the next generation of antibody therapy. Various strategies are employed, including altering glycosylation patterns via glycoengineering and introducing mutations to the Fc region, thereby enhancing Fc receptor or complement interactions. Further, Fc engineering strategies enable the generation of bispecific IgG-based heterodimeric antibodies. As Fc engineering techniques continue to evolve, an expanding portfolio of Fc-engineered antibodies is advancing through clinical development, with several already approved for medical use. Despite the plethora of Fc-based mutations that have been analyzed in in vitro and in vivo models, we focus here in this review on the relevant Fc engineering strategies of approved therapeutic antibodies to finetune effector functions, to modify half-life and to stabilize asymmetric bispecific IgGs. Full article

Glycosylation of IgG regulates the effector function of this antibody in the immune response. Glycosylated IgG is a potent therapeutic used for both research and clinical purposes. While there is ample research on how different cell culture conditions affect IgG glycosylation, the data are missing on the stability of IgG glycome during long cell passaging, i.e., cell “aging”. To test this, we performed three independent time course experiments in FreeStyle 293-F cells, which secrete IgG with a human-like glycosylation pattern and are frequently used to generate defined IgG glycoforms. During long-term cell culturing, IgG glycome stayed fairly stable except for galactosylation, which appeared extremely variable. Cell transcriptome analysis revealed no correlation in galactosyltransferase B4GALT1 expression with galactosylation change, but with expression of EEF1A1 and SLC38A10, genes previously associated with IgG galactosylation through GWAS. The FreeStyle 293-F cell-based system for IgG production is a good model for studies of mechanisms underlying IgG glycosylation, but results from the present study point to the utmost importance of the need to control IgG galactosylation in both in vitro and in vivo systems. This is especially important for improving the production of precisely glycosylated IgG for therapeutic purposes, since IgG galactosylation affects the inflammatory potential of IgG. Full article

The 2022 global outbreaks of monkeypox virus (MPXV) and increased human-to-human transmission calls for the urgent development of countermeasures to protect people who cannot benefit from vaccination. Here, we describe the development of glycovariants of 7D11, a neutralizing monoclonal IgG antibody (mAb) directed against the L1 transmembrane protein of the related vaccinia virus, in a plant-based system as a potential therapeutic against the current MPVX outbreak. Our results indicated that 7D11 mAb quickly accumulates to high levels within a week after gene introduction to plants. Plant-produced 7D11 mAb assembled correctly into the tetrameric IgG structure and can be easily purified to homogeneity. 7D11 mAb exhibited a largely homogeneous N-glycosylation profile, with or without plant-specific xylose and fucose residues, depending on the expression host, namely wild-type or glycoengineered plants. Plant-made 7D11 retained specific binding to its antigen and displayed a strong neutralization activity against MPXV, as least as potent as the reported activity against vaccinia virus. Our study highlights the utility of anti-L1 mAbs as MPXV therapeutics, and the use of glycoengineered plants to develop mAb glycovariants for potentially enhancing the efficacy of mAbs to combat ever-emerging/re-emerging viral diseases. Full article

Antibody-dependent cell-mediated cytotoxicity (ADCC) by natural killer (NK) lymphocytes eliminates cells infected with viruses. Anti-viral ADCC requires three components: (1) antibody; (2) effector lymphocytes with the Fc-IgG receptor CD16A; and (3) viral proteins in infected cell membranes. Fc-afucosylated antibodies bind with greater affinity to CD16A than fucosylated antibodies; individuals’ variation in afucosylation contributes to differences in ADCC. Current assays for afucosylated antibodies involve expensive methods. We report an improved bioassay for antibodies that supports ADCC, which encompasses afucosylation. This assay utilizes the externalization of CD107a by NK-92-CD16A cells after antibody recognition. We used anti-CD20 monoclonal antibodies, GA101 WT or glycoengineered (GE), 10% or ~50% afucosylated, and CD20-positive Raji target cells. CD107a increased detection 7-fold compared to flow cytometry to detect Raji-bound antibodies. WT and GE antibody effective concentrations (EC₅₀s) for CD107a externalization differed by 20-fold, with afucosylated GA101-GE more detectable. The EC₅₀s for CD107a externalization vs. ⁵¹Cr cell death were similar for NK-92-CD16A and blood NK cells. Notably, the % CD107a-positive cells were negatively correlated with dead Raji cells and were nearly undetectable at high NK:Raji ratios required for cytotoxicity. This bioassay is very sensitive and adaptable to assess anti-viral antibodies but unsuitable as a surrogate assay to monitor cell death after ADCC. Full article

Therapeutic proteins have unique advantages over small-molecule drugs in the treatment of various diseases, such as higher target specificity, stronger pharmacological efficacy and relatively low side effects. These advantages make them increasingly valued in drug development and clinical practice. However, although highly valued, the intrinsic limitations in their physical, chemical and pharmacological properties often restrict their wider applications. As one of the most important post-translational modifications, glycosylation has been shown to exert positive effects on many properties of proteins, including molecular stability, and pharmacodynamic and pharmacokinetic characteristics. Glycoengineering, which involves changing the glycosylation patterns of proteins, is therefore expected to be an effective means of overcoming the problems of therapeutic proteins. In this review, we summarize recent efforts and advances in the glycoengineering of erythropoietin and IgG monoclonal antibodies, with the goals of illustrating the importance of this strategy in improving the performance of therapeutic proteins and providing a brief overview of how glycoengineering is applied to protein-based drugs. Full article

Efficient characterization of IgE antibodies and their glycan structures is required for understanding their function in allergy and in the emerging AllergoOncology field for antibody immunotherapy. We report the generation, glyco-profiling and functional analysis of native and sialic acid-deficient glyco-engineered human IgE. The antibodies produced from human embryonic kidney cells were purified via a human IgE class-specific affinity matrix and structural integrity was confirmed by SDS-PAGE and size-exclusion chromatography (SEC). Purified IgEs specific for the tumor-associated antigens Chondroitin Sulfate Proteoglycan 4 (CSPG4-IgE) and Human Epidermal Growth Factor Receptor 2 (HER2-IgE) were devoid of by-products such as free light chains. Using neuraminidase-A, we generated sialic acid-deficient CSPG4-IgE as example glyco-engineered antibody. Comparative glycan analyses of native and glyco-engineered IgEs by Hydrophilic interaction liquid chromatography (HILIC)-high performance liquid chromatography (HPLC) indicated loss of sialic acid terminal residues and differential glycan profiles. Native and glyco-engineered CSPG4-IgEs recognized Fc receptors on the surface of human FcεRI-expressing rat basophilic leukemia RBL-SX38 cells, and of CD23/FcεRII-expressing human RPMI-8866 B-lymphocytes and bound to CSPG4-expressing A2058 human melanoma cells, confirming Fab-mediated recognition. When cross-linked on the cell surface, both IgEs triggered RBL-SX38 degranulation. We demonstrate efficient generation and functional competence of recombinant native and sialic acid-deficient IgEs. Full article

Monoclonal antibodies (mAbs) are one of the cornerstones of modern medicine, across an increasing range of therapeutic areas. All therapeutic mAbs are glycoproteins, i.e., their polypeptide chain is decorated with glycans, oligosaccharides of extraordinary structural diversity. The presence, absence, and composition of these glycans can have a profound effect on the pharmacodynamic and pharmacokinetic profile of individual mAbs. Approaches for the glycoengineering of therapeutic mAbs—the manipulation and optimisation of mAb glycan structures—are therefore of great interest from a technological, therapeutic, and regulatory perspective. In this review, we provide a brief introduction to the effects of glycosylation on the biological and pharmacological functions of the five classes of immunoglobulins (IgG, IgE, IgA, IgM and IgD) that form the backbone of all current clinical and experimental mAbs, including an overview of common mAb expression systems. We review selected examples for the use of small molecule inhibitors of glycan biosynthesis for mAb glycoengineering, we discuss the potential advantages and challenges of this approach, and we outline potential future applications. The main aim of the review is to showcase the expanding chemical toolbox that is becoming available for mAb glycoengineering to the biology and biotechnology community. Full article

Interactions with cell surface receptors enhance the therapeutic properties of many important antibodies, including the low-affinity Fc γ Receptors (FcγRs). These interactions require proper processing of the immunoglobulin G Fc N-glycan, and eliminating the N-glycan abolishes binding, restricting antibody production to mammalian expression platforms. Yeasts, for example, generate extensively mannosylated N-glycans that are unsuitable for therapeutics. However, Fc with a specifically truncated N-glycan still engages receptors with considerable affinity. Here we describe the creation and applications of a novel Saccharomyces cerevisiae strain that specifically modifies the IgG1 Fc domain with an N-glycan consisting of a single N-acetylglucosamine residue. This strain displayed glycoengineered Fc on its surface for screening yeast surface display libraries and also served as an alternative platform to produce glycoengineered Rituximab. An IgG-specific endoglycosidase (EndoS2) truncates the IgG1 Fc N-glycan. EndoS2 was targeted to the yeast ER using the signal peptide from the yeast protein disulfide isomerase (PDI) and a yeast ER retention signal (HDEL). Furthermore, >99% of the yeast expressed Rituximab displayed the truncated glycoform as determined by SDS-PAGE and ESI-MS analyses. Lastly, the yeast expressed Rituximab engaged the FcγRIIIa with the expected affinity (K_D = 2.0 ± 0.5 μM) and bound CD20 on Raji B cells. Full article