Synthesis and immunological evaluation of the unnatural β-linked mucin-1 Thomsen-Friedenreich conjugate

Glycosyl benzoates as novel substrates for glycosynthases

The development of a procedure for the one-pot synthesis of glycosyl benzoates directly from unprotected sugars in aqueous media using 2-chloro-1,3-dimethylimidazolium chloride (DMC), thiobenzoic acid, and triethylamine is reported. These glycosyl donors are excellent substrates for wild-type and mutant glycosidases. β-Glucosyl benzoate was hydrolysed by the GH1 β-glucosidase derived from Halothermothrix orenii (HorGH1). Subsequent use of this substrate in thioligase-mediated glycosylation of p-nitrothiophenol demonstrated their superiority as donors compared to their p-nitrophenol counterparts with excellent conversions. Using a series of arene nucleophiles, we also demonstrate good to excellent conversions (up to 94%) of β-glucosyl benzoate to the corresponding p-nitrophenyl- and thioglycosides.

Immunomodulatory glycomedicine: Introducing next generation cancer glycovaccines

Cancer remains a leading cause of death worldwide due to the lack of safer and more effective therapies. Cancer vaccines developed from neoantigens are an emerging strategy to promote protective and therapeutic anti-cancer immune responses. Advances in glycomics and glycoproteomics have unveiled several cancer-specific glycosignatures, holding tremendous potential to foster effective cancer glycovaccines. However, the immunosuppressive nature of tumours poses a major obstacle to vaccine-based immunotherapy. Chemical modification of tumour associated glycans, conjugation with immunogenic carriers and administration in combination with potent immune adjuvants constitute emerging strategies to address this bottleneck. Moreover, novel vaccine vehicles have been optimized to enhance immune responses against otherwise poorly immunogenic cancer epitopes. Nanovehicles have shown increased affinity for antigen presenting cells (APCs) in lymph nodes and tumours, while reducing treatment toxicity. Designs exploiting glycans recognized by APCs have further enhanced the delivery of antigenic payloads, improving glycovaccine's capacity to elicit innate and acquired immune responses. These solutions show potential to reduce tumour burden, while generating immunological memory. Building on this rationale, we provide a comprehensive overview on emerging cancer glycovaccines, emphasizing the potential of nanotechnology in this context. A roadmap towards clinical implementation is also delivered foreseeing advances in glycan-based immunomodulatory cancer medicine.

Pairing Nanoparticles Geometry with TLR Agonists to Modulate Immune Responses for Vaccine Development

Nanotechnology-based vaccine development necessitates understanding the crucial biophysical properties of nanostructures that alter immune responses. In this study, we demonstrate the synergistic effect of gold nanoparticles (AuNPs) shapes with toll-like receptor (TLR) agonists in immune modulation activity. Our results showed that CpG- and imidazoquinoline-conjugated rod-shaped AuNPs display relatively fast uptake by bone marrow-derived macrophage cells but exhibit poor immunogenic responses compared to their spherical and star-shaped AuNP counterparts. Surprisingly, star-shaped AuNPs exhibited intense pro-inflammatory cytokine secretion. Further mechanistic studies showed that star-shaped AuNPs were abundantly localized in the late endosome and lysosomal regions, whereas rod-shaped AuNPs were majorly sequestered in the mitochondrial region. These findings reveal that the shape of the nanostructures plays a pivotal role in driving the adjuvant molecules toward their receptors and altering immune responses.

Isolipoic acid-linked gold nanoparticles bearing the thomsen friedenreich tumor-associated carbohydrate antigen: Stability and in vitro studies

We have previously prepared gold nanoparticles (AuNPs) bearing the Thomsen-Friedenreich antigen disaccharide (TF_ag), a pan-carcinoma, Tumor-Associated Carbohydrate Antigen (TACA), as tools for various assays and biological applications. Conjugation to AuNPs typically involves the use of thiols due to the affinity of sulfur for the gold surface of the nanoparticle. While a use of a single thiol-containing ligand bound to the gold surface is standard practice, several studies have shown that ligands bearing multiple thiols can enhance the strength of the conjugation in a nearly linear fashion. (R)-(+)-α-Lipoic acid (LA), a naturally occurring disulfide-containing organic acid that is used as a cofactor in many enzymatic reactions, has been used as a linker to conjugate various molecules to AuNPs through its branched di-thiol system to enhance nanoparticle stability. We sought to use a similar system to increase nanoparticle stability that was devoid of the chiral center in (R)-(+)-α-lipoic acid. Isolipoic acid, an isomer of LA, where the exocyclic pentanoic acid chain is shifted by one carbon on the dithiolane ring to produce an achiral acid, was thought to act similarly as LA without the risk of any contaminating (L)-(−) isomer. We synthesized AuNPs with ligands of both serine and threonine glycoamino acids bearing the TF_ag linked to isolipoic acid and examined their stability under various conditions. In addition, these particles were shown to bind to Galectin-3 and inhibit the interaction of Galectin-3 with a protein displaying copies of the TF_ag. These agents should prove useful in the design of potential antimetastatic therapeutics that would benefit from achiral linkers that are geometrically linear and achiral.

A self-adjuvanting anti-tumor nanoliposomal vaccine based on fluorine-substituted MUC1 glycopeptide

Herein, a self-adjuvanting fluorinated MUC1-based nanoliposomal antitumor vaccine was constructed for the first time. Both the tumor-associated antigen and the mode of its presentation affect the immune response for antitumor vaccines.

Current strategies for characterization of mucin-domain glycoproteins

Glycosylation, and especially O-linked glycosylation, remains a critical blind spot in the understanding of post-translational modifications. Due to their nature as proteins defined by a large density and abundance of O-glycosylation, mucins present extra challenges in the analysis of their structure and function. However, recent breakthroughs in multiple areas of research have rendered mucin-domain glycoproteins more accessible to current characterization techniques. In particular, the adaptation of mucinases to glycoproteomic workflows, the manipulation of cellular glycosylation pathways, and the advances in synthetic methods to more closely mimic mucin domains have introduced new and exciting avenues to study mucin glycoproteins. Here, we summarize recent developments in understanding the structure and biological function of mucin domains and their associated glycans, from glycoproteomic tools and visualization methods to synthetic glycopeptide mimetics.

Glycoconjugate Nanoparticle-Based Systems in Cancer Immunotherapy: Novel Designs and Recent Updates

For many years, cell-surface glycans (in particular, Tumor-Associated Carbohydrate Antigens, TACAs) have been the target of both passive and active anticancer immunotherapeutic design. Recent advances in immunotherapy as a treatment for a variety of malignancies has revolutionized anti-tumor treatment regimens. Checkpoint inhibitors, Chimeric Antigen Receptor T-cells, Oncolytic virus therapy, monoclonal antibodies and vaccines have been developed and many approvals have led to remarkable outcomes in a subset of patients. However, many of these therapies are very selective for specific patient populations and hence the search for improved therapeutics and refinement of techniques for delivery are ongoing and fervent research areas. Most of these agents are directed at protein/peptide epitopes, but glycans–based targets are gaining in popularity, and a handful of approved immunotherapies owe their activity to oligosaccharide targets. In addition, nanotechnology and nanoparticle-derived systems can help improve the delivery of these agents to specific organs and cell types based on tumor-selective approaches. This review will first outline some of the historical beginnings of this research area and subsequently concentrate on the last 5 years of work. Based on the progress in therapeutic design, predictions can be made as to what the future holds for increasing the percentage of positive patient outcomes for optimized systems.

Alum Adjuvant and Built-in TLR7 Agonist Synergistically Enhance Anti-MUC1 Immune Responses for Cancer Vaccine

The tumor-associated antigen mucin 1 (MUC1) is an attractive target of antitumor vaccine, but its weak immunogenicity is a big challenge for the development of vaccine. In order to enhance immune responses against MUC1, herein, we conjugated small molecular toll-like receptor 7 agonist (TLR7a) to carrier protein BSA via MUC1 glycopeptide to form a three-component conjugate (BSA-MUC1-TLR7a). Furthermore, we combined the three-component conjugate with Alum adjuvant to explore their synergistic effects. The immunological studies indicated that Alum adjuvant and built-in TLR7a synergistically enhanced anti-MUC1 antibody responses and showed Th1-biased immune responses. Meanwhile, antibodies elicited by the vaccine candidate effectively recognized tumor cells and induced complement-dependent cytotoxicity. In addition, Alum adjuvant and built-in TLR7a synergistically enhanced MUC1 glycopeptide-specific memory CD8+ T-cell immune responses. More importantly, the vaccine with the binary adjuvant can significantly inhibit tumor growth and prolong the survival time of mice in the tumor challenge experiment. This novel vaccine construct provides an effective strategy to develop antitumor vaccines.

MUC1 Specific Immune Responses Enhanced by Coadministration of Liposomal DDA/MPLA and Lipoglycopeptide

Mucin 1 (MUC1), a well-known tumor-associated antigen and attractive target for tumor immunotherapy, is overexpressed in most human epithelial adenomas with aberrant glycosylation. However, its low immunogenicity impedes the development of MUC1-targeted antitumor vaccines. In this study, we investigated three liposomal adjuvant systems containing toll-like receptor 4 (TLR4) agonist monophosphoryl lipid A (MPLA) and auxiliary lipids of different charges: cationic lipid dimethyldioctadecylammonium (DDA), neutral lipid distearoylglycerophosphocholine (DSPC) or anionic lipid dioleoylphosphatidylglycerol (DOPG), respectively. ELISA assay evidenced that the positively charged DDA/MPLA liposomes are potent immune activators, which induced remarkable levels of anti-MUC1 antibodies and exhibited robust Th1-biased immune responses. Importantly, the antibodies induced by DDA/MPLA liposomes efficiently recognized and killed MUC1-positive tumor cells through complement-mediated cytotoxicity. In addition, antibody titers in mice immunized with P2-MUC1 vaccine were significantly higher than those from mice immunized with P1-MUC1 or MUC1 vaccine, which indicated that the lipid conjugated on MUC1 antigen also played important role for immunomodulation. This study suggested that the liposomal DDA/MPLA with lipid-MUC1 is a promising antitumor vaccine, which can be used for the immunotherapy of various epithelial carcinomas represented by breast cancer.

Targeting Tumor Glycans for Cancer Therapy: Successes, Limitations, and Perspectives

Simple Summary

Aberrant glycosylation is a common feature of many cancers, and it plays crucial roles in tumor development and biology. Cancer progression can be regulated by several physiopathological processes controlled by glycosylation, such as cell–cell adhesion, cell–matrix interaction, epithelial-to-mesenchymal transition, tumor proliferation, invasion, and metastasis. Different mechanisms of aberrant glycosylation lead to the formation of tumor-associated carbohydrate antigens (TACAs), which are suitable for selective cancer targeting, as well as novel antitumor immunotherapy approaches. This review summarizes the strategies developed in cancer immunotherapy targeting TACAs, analyzing molecular and cellular mechanisms and state-of-the-art methods in clinical oncology.

Abstract

Aberrant glycosylation is a hallmark of cancer and can lead to changes that influence tumor behavior. Glycans can serve as a source of novel clinical biomarker developments, providing a set of specific targets for therapeutic intervention. Different mechanisms of aberrant glycosylation lead to the formation of tumor-associated carbohydrate antigens (TACAs) suitable for selective cancer-targeting therapy. The best characterized TACAs are truncated O-glycans (Tn, TF, and sialyl-Tn antigens), gangliosides (GD2, GD3, GM2, GM3, fucosyl-GM1), globo-serie glycans (Globo-H, SSEA-3, SSEA-4), Lewis antigens, and polysialic acid. In this review, we analyze strategies for cancer immunotherapy targeting TACAs, including different antibody developments, the production of vaccines, and the generation of CAR-T cells. Some approaches have been approved for clinical use, such as anti-GD2 antibodies. Moreover, in terms of the antitumor mechanisms against different TACAs, we show results of selected clinical trials, considering the horizons that have opened up as a result of recent developments in technologies used for cancer control.

Mechanisms of cellular and humoral immunity through the lens of VLP-based vaccines

INTRODUCTION

Vaccination can be effective defense against many infectious agents and the corresponding diseases. Discoveries elucidating the mechanisms of the immune system have given hopes to developing vaccines against diseases recalcitrant to current treatment/prevention strategies. One such finding is the ability of immunogenic biological nanoparticles to powerfully boost the immunogenicity of poorer antigens conjugated to them with virus-like particle (VLP)-based vaccines as a key example. VLPs take advantage of the well-defined molecular structures associated with sub-unit vaccines and the immunostimulatory nature of conjugate vaccines.

AREAS COVERED

In this review, we will discuss how advances in understanding the immune system can inform VLP-based vaccine design and how VLP-based vaccines have uncovered underlying mechanisms in the immune system.

EXPERT OPINION

As our understanding of mechanisms underlying the immune system increases, that knowledge should inform our vaccine design. Testing of proof-of-concept vaccines in the lab should seek to elucidate the underlying mechanisms of immune responses. The integration of these approaches will allow for VLP-based vaccines to live up to their promise as a powerful plug-and-play platform for next generation vaccine development.

Total synthesis of the O-antigen repeating unit of Providencia stuartii O49 serotype through linear and one-pot assemblies

Capsular polysaccharides of pathogenic bacteria have been reported to be effective vaccines against diseases caused by them. Providencia stuartii is a class of enterobacteria of the family Providencia that is responsible for several antibiotic resistant infections, particularly urinary tract infections of patients with prolonged catheterization in hospital settings. Towards the goal of development of vaccine candidates against this pathogen, we herein report the total synthesis of a trisaccharide repeating unit of the O-antigen polysaccharide of the P. stuartii O49 serotype containing the →6)-β-ᴅ-Galp-(1→3)-β-ᴅ-GalpNAc(1→4)-α-ᴅ-Galp(1→ linkage. The synthesis of the trisaccharide repeating unit was carried out first by a linear strategy involving the [1 + (1 + 1 = 2)] assembly, followed by a one-pot synthesis involving [1 + 1 + 1] strategy from the corresponding monosaccharides. The one-pot method provided a higher yield of the protected trisaccharide intermediate (73%) compared to the two step synthesis (66%). The protected trisaccharide was then deprotected and N-acetylated to finally afford the desired trisaccharide repeating unit as its α-p-methoxyphenyl glycoside.

Chemoenzymatic Synthesis of 9NHAc-GD2 Antigen to Overcome the Hydrolytic Instability of O-Acetylated-GD2 for Anticancer Conjugate Vaccine Development

Ganglioside GD2 is an attractive tumor-associated carbohydrate antigen for anti-cancer vaccine development. However, its low immunogenicity and the significant side effects observed with anti-GD2 antibodies present significant obstacles for vaccines. To overcome these, a new GD2 derivative bearing an N-acetamide (NHAc) at its non-reducing end neuraminic acid (9NHAc-GD2) has been designed to mimic the 9-O-acetylated-GD2 (9OAc-GD2), a GD2 based antigen with a restricted expression on tumor cells. 9NHAc-GD2 was synthesized efficiently via a chemoenzymatic method and subsequently conjugated with a powerful carrier bacteriophage Qβ. Mouse immunization with the Qβ-9NHAc-GD2 conjugate elicited strong and long-lasting IgG antibodies, which were highly selective toward 9NHAc-GD2 with little cross-recognition of GD2. Immunization of canines with Qβ-9NHAc-GD2 showed the construct was immunogenic in canines with little adverse effects, paving the way for future clinical translation to humans.

Developing Acid-Responsive Glyco-Nanoplatform Based Vaccines for Enhanced Cytotoxic T-lymphocyte Responses Against Cancer and SARS-CoV-2

Cytotoxic T-lymphocytes (CTLs) are central for eliciting protective immunity against malignancies and infectious diseases. Here, for the first time, partially oxidized acetalated dextran nanoparticles (Ox-AcDEX NPs) with an average diameter of 100 nm are fabricated as a general platform for vaccine delivery. To develop effective anticancer vaccines, Ox-AcDEX NPs are conjugated with a representative CTL peptide epitope (CTLp) from human mucin-1 (MUC1) with the sequence of TSAPDTRPAP (referred to as Mp1) and an immune-enhancing adjuvant R837 (referred to as R) via imine bond formation affording AcDEX-(imine)-Mp1-R NPs. Administration of AcDEX-(imine)-Mp1-R NPs results in robust and long-lasting anti-MUC1 CTL immune responses, which provides mice with superior protection from the tumor. To verify its universality, this nanoplatform is also exploited to deliver epitopes from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to prevent coronavirus disease 2019 (COVID-19). By conjugating Ox-AcDEX NPs with the potential CTL epitope of SARS-CoV-2 (referred to as Sp) and R837, AcDEX-(imine)-Sp-R NPs are fabricated for anti-SARS-CoV-2 vaccine candidates. Several epitopes potentially contributing to the induction of potent and protective anti-SARS-CoV-2 CTL responses are examined and discussed. Collectively, these findings shed light on the universal use of Ox-AcDEX NPs to deliver both tumor-associated and virus-associated epitopes.

MUC1: Structure, Function, and Clinic Application in Epithelial Cancers

The transmembrane glycoprotein mucin 1 (MUC1) is a mucin family member that has different functions in normal and cancer cells. Owing to its structural and biochemical properties, MUC1 can act as a lubricant, moisturizer, and physical barrier in normal cells. However, in cancer cells, MUC1 often undergoes aberrant glycosylation and overexpression. It is involved in cancer invasion, metastasis, angiogenesis, and apoptosis by virtue of its participation in intracellular signaling processes and the regulation of related biomolecules. This review introduces the biological structure and different roles of MUC1 in normal and cancer cells and the regulatory mechanisms governing these roles. It also evaluates current research progress and the clinical applications of MUC1 in cancer therapy based on its characteristics.