Fluorine-modified sialyl-Tn-CRM197 vaccine elicits a robust immune response

Active immunization with recombinant GnRH6-CRM197 inhibits reproductive function of male rats

Gonadotropin-releasing hormone (GnRH) vaccines have been successfully used for the inhibition of gonadal development and function, but current GnRH-based vaccines often present variability in the response. Cross-reactive material 197 (CRM197) has been used as carrier molecules to enhance an immune response to associated antigens. So, the synthetic mammalian tandem-repeated GnRH hexamer (GnRH6) gene was integrated into the expression plasmid pET-21a. Recombinant GnRH6-CRM197 protein was subsequently overexpressed in Escherichia coli strain BL21 and purified through Nickel column affinity chromatography and the antigenicity and biological effects of GnRH6-CRM197 were evaluated in rats. Sixteen 4-month-old adult male rats were randomly divided into two groups: the GnRH6-CRM197 group (n = 8) and the control group (n = 8). The GnRH6-CRM197 group rats were subcutaneously immunized with 100 μg of GnRH6-CRM197, administered thrice at 2-week intervals with GnRH6-CRM197.The control group received only a white oil adjuvant. Following the initial immunization, the weights of animals were recorded, and blood samples were collected from the orbital sinus at 4, 4.5, 5, 5.5, 6, 6.5, and 7 months. Serum antibody titers and testosterone concentrations were quantified using ELISA and CLIA, respectively. Additionally, testicular tissues were collected for morphological examination. The results revealed a significant increase in serum GnRH antibody titers (p < 0.05), but a significant decrease in serum testosterone concentrations (p < 0.05), and the weight, length, width, and girth of the testis, and the number of spermatogonia cells, spermatocytes, and sperm cells in the immunized rats. Furthermore, seminiferous tubules revealed significant atrophy and no sperm were observed in the immunized animals. Thus, GnRH6-CRM197 may be an effective antigen and a potential immunocastration vaccine.

Chemoenzymatic synthesis and immunological evaluation of sialyl-Thomsen-Friedenreich (sTF) antigen conjugate to CRM197

sTF (sialyl-Thomsen-Friedenreich) is a type of tumor-associated carbohydrate antigens (TACAs) and is highly expressed in various human malignancies. To validate if sTF could be a valuable molecular target for future cancer vaccine development, in this work the sTF antigen was prepared by adopting a strategy combining chemical and enzymatic methods, and then was covalently conjugated to a carrier protein, CRM197. The preliminary immunological evaluation, performed on BALB/c mice, revealed that the sTF-CRM197 conjugate elicited high titers of specific IgG antibodies. FACS experiments showed that the antisera induced by sTF-CRM197 conjugate could specifically recognize and bind to sTF-positive cancer cells T-47D. Furthermore, the conjugate mediated effective and specific antibody-mediated complement-dependent cytotoxicity (CDC).

Development of NHAcGD2/NHAcGD3 conjugates of bacteriophage MX1 virus-like particles as anticancer vaccines

The successful development of an anticancer vaccine will be a giant leap forward in cancer prevention and treatment. Herein, the bacteriophage MX1 coat protein virus-like particles (MX1 VLPs) have been conjugated with 9NHAc-GD2 (NHAcGD2) to obtain a MX1-NHAcGD2 conjugate. Intriguingly, vaccinating against this conjugate produced a robust anti-NHAcGD2 IgG response in mice, with an average IgG titer of over 3 million. More interestingly, antibodies induced by the MX1-NHAcGD2 conjugate bound well to IMR-32 neuroblastoma cells and had potent complement-dependent cytotoxic (CDC) effects on IMR-32 cells. Inspired by the superiority of the 9NHAc-GD2 antigen, we also designed another 9NHAc-modified ganglioside antigen, 9NHAc-GD3 (NHAcGD3), to overcome the hydrolytic instability of 9-O-acetylated-GD3. By coupling NHAcGD3 with MX1 VLP, the MX1-NHAcGD3 conjugate was constructed. Strikingly, vaccination of MX1-NHAcGD3 elicited high anti-NHAcGD3 IgG antibodies, which effectively recognized human malignant melanoma SK-MEL-28 cells and had a significant CDC effect against this cell line. This study provides novel MX1-NHAcGD2 and MX1-NHAcGD3 conjugates with broad clinical translational prospects as promising anticancer vaccines.

Aberrant Glycosylation as Immune Therapeutic Targets for Solid Tumors

Glycosylation occurs at all major types of biomolecules, including proteins, lipids, and RNAs to form glycoproteins, glycolipids, and glycoRNAs in mammalian cells, respectively. The carbohydrate moiety, known as glycans on glycoproteins and glycolipids, is diverse in their compositions and structures. Normal cells have their unique array of glycans or glycome which play pivotal roles in many biological processes. The glycan structures in cancer cells, however, are often altered, some having unique structures which are termed as tumor-associated carbohydrate antigens (TACAs). TACAs as tumor biomarkers are glycan epitopes themselves, or glycoconjugates. Some of those TACAs serve as tumor glyco-biomarkers in clinical practice, while others are the immune therapeutic targets for treatment of cancers. A monoclonal antibody (mAb) to GD2, an intermediate of sialic-acid containing glycosphingolipids, is an example of FDA-approved immune therapy for neuroblastoma indication in young adults and many others. Strategies for targeting the aberrant glycans are currently under development, and some have proceeded to clinical trials. In this review, we summarize the currently established and most promising aberrant glycosylation as therapeutic targets for solid tumors.

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.

Chemoenzymatic Total Synthesis of Haemophilus ducreyi Lipooligosaccharide Core Octasaccharides Containing Natural and Unnatural Sialic Acids

The first total synthesis of Haemophilus ducreyi lipooligosaccharide core octasaccharides containing natural and unnatural sialic acids has been achieved by an efficient chemoenzymatic approach. A highly convergent [3 + 3] coupling strategy was developed to chemically assemble a unique hexasaccharide bearing multiple rare higher-carbon sugars d-glycero-d-manno-heptose (d,d-Hep), l-glycero-d-manno-heptose (l,d-Hep), and 3-deoxy-α-d-manno-oct-2-ulosonic acid (Kdo). Key features include sequential one-pot glycosylations for oligosaccharide assembly and the construction of the challenging α-(1 → 5)-linked Hep-Kdo glycosidic bond by gold-catalyzed glycosylation with a glycosyl ortho-alkynylbenzoate donor. Furthermore, the sequential enzyme-catalyzed regio- and stereoselective introduction of a galactose residue using β-1,4-galactosyltransferase and different sialic acids using a one-pot multienzyme sialylation system was efficiently accomplished to provide the target octasaccharides.

Cancer Vaccines Based on Fluorine-Modified KH-1 Elicit Robust Immune Response

KH-1 is a tumor-associated carbohydrate antigen (TACA), which serves as a valuable target of antitumor vaccines for cancer immunotherapies. However, most TACAs are thymus-independent antigens (TD-Ag), and they tend to induce immunological tolerance, leading to their low immunogenicity. To overcome these problems, some fluorinated derivatives of the KH-1 antigen were designed, synthesized, and conjugated to the carrier protein CRM197 to form glycoconjugates, which were used for immunological studies with Freund's adjuvant. The results showed that fluorine-modified N-acyl KH-1 conjugates can induce higher titers of antibodies, especially IgG, which can recognize KH-1-positive cancer cells and can eliminate cancer cells through complement-dependent cytotoxicity (CDC). The trifluoro-modified KH-1-TF-CRM197 showed great potential as an anticancer vaccine candidate.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2019-2020

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2020. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. The review is basically divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of arrays. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other areas such as medicine, industrial processes and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. The reported work shows increasing use of incorporation of new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented nearly 40 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show little sign of diminishing.

Fully synthetic Tn-based three-component cancer vaccine using covalently linked TLR4 ligand MPLA and iNKT cell agonist KRN-7000 as built-in adjuvant effectively protects mice from tumor development

We present a new strategy for self-adjuvanting vaccine development that has different types of covalently-linked immunostimulants as the carrier molecule. Using Tn antigen as the model, a three-component vaccine (MPLA-Tn-KRN7000) containing the TLR4 ligand MPLA and the iNKT cell agonist KRN7000 was designed and synthesized. This expands fully synthetic self-adjuvanting vaccine studies that use a single carrier to one with two different types of carriers. The corresponding two-component conjugate vaccines Tn-MPLA, Tn-KRN7000 and Tn-CRM197 were also synthesized, as controls. The immunological evaluation found that MPLA-Tn-KRN7000 elicits robust Tn-specific and T cell-dependent immunity. The antibodies specifically recognized, bound to and exhibited complement-dependent cytotoxicity against Tn-positive cancer cells. In addition, MPLA-Tn-KRN7000 increased the survival rate and survival time of tumor-challenged mice, and surviving mice reject further tumor attacks without any additional treatment. Compared to the glycoprotein vaccine Tn-CRM197, the two-component conjugate vaccines, Tn-MPLA and Tn-KRN7000, and the physical mixture of Tn-MPLA and Tn-KRN7000, MPLA-Tn-KRN7000 showed the most effect at combating tumor cells both in vitro and in vivo. The comparison of immunological studies in wild-type and TLR4 knockout mice, along with the test of binding affinity to CD1d protein suggests that the covalently linked MPLA-KRN7000 immunostimulant induces a synergistic activation of TLR4 and iNKT cell that improves the immunogenicity of Tn. This work demonstrates that MPLA-Tn-KRN7000 has the potential to be a vaccine candidate and provides a new direction for fully synthetic vaccine design.

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.

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.

Fully synthetic Mincle-dependent self-adjuvanting cancer vaccines elicit robust humoral and T cell-dependent immune responses and protect mice from tumor development

A new strategy based on a macrophage-inducible C-type lectin (Mincle) agonist was established to construct synthetic cancer vaccines. Using sialyl-Tn (STn) as a model antigen, four conjugates with the Mincle agonist as a built-in adjuvant were designed and synthesized through a facile and efficient method. All conjugates could induce BMDMs to produce inflammatory cytokines in a Mincle-dependent manner and were found to elicit robust humoral and T cell-dependent immune responses alone in mice. The corresponding antibodies could recognize, bind and exhibit complement-dependent cytotoxicity to STn-positive cancer cells, leading to tumor cell lysis. Moreover, all conjugates could effectively inhibit tumor growth and prolong the mice survival time in vivo, with therapeutic effects better than STn-CRM197/Al. Notably, compared to conventional glycoprotein conjugate vaccines, these fully synthetic conjugate vaccines do not cause "epitope suppression." Mincle ligands thus hold great potential as a platform for the development of new vaccine carriers with self-adjuvanting properties for cancer treatment. Preliminary structure-activity relationship analysis shows that a vaccine containing one STn antigen carried by vizantin exhibits the best efficacy, providing support for further optimization and additional investigation into Mincle agonists as the carrier of self-adjuvanting cancer vaccines.

Chemoenzymatic synthesis and biological evaluation of ganglioside GM3 and lyso-GM3 as potential agents for cancer therapy

A highly efficient chemoenzymatic method for synthesizing ganglioside GM3 and lyso-GM3 was reported here. Enzymatic extension of the chemically synthesized lactosyl sphingosine using efficient one-pot multienzyme (OPME) reaction allowed glycosylation to be carried out in aqueous solutions realizing the greening of reactions. Ganglioside GM3 was synthesized through 10 steps with a total yield of 22%. Lyso-GM3 was very useful for kinds of derivatization. The anti-proliferation activity studies demonstrated that these compounds 14-16 with sphingosine exhibited more potency than the corresponding lyso-GM3 with ceramide. All ganglioside GM3 and lyso-GM3 can effectively inhibit the migration of melanoma B16-F10 cells. These chemoenzymaticlly synthesized GM3 and lyso-GM3 exhibited antitumor activities, which can provide valuable sights to search new antitumor agents for cancer therapy.

Structure-based Design of Anti-cancer Vaccines: The Significance of Antigen Presentation to Boost the Immune Response

Immunotherapy, alone or in combination with other therapies, is widely used against cancer. Glycoprotein Mucin 1 (MUC1), which is overexpressed and aberrantly glycosylated in tumor cells, is one of the most promising candidates to engineer new cancer vaccines. In this context, the development of stable antigens that can elicit a robust immune response is mandatory. Here, we describe the design and in vivo biological evaluation of three vaccine candidates based on MUC1 glycopeptides that comprise unnatural elements in their structure. By placing the Tn antigen (GalNAcα-O-Ser/Thr) at the center of the design, the chemical modifications include changes to the peptide backbone, glycosidic linkage, and at the carbohydrate level. Significantly, the three vaccines elicit robust immune responses in mice and produce antibodies that can be recognized by several human cancer cells. In all cases, a link was stablished between the conformational changes induced by the new elements in the antigen presentation and the immune response induced in mice. According to our data, the development of effective MUC1-based vaccines should use surrogates that mimic the conformational space of aberrantly glycosylated MUC1 glycopeptides found in tumors.

Carbohydrate-Based Macromolecular Biomaterials

Carbohydrates are the most abundant and one of the most important biomacromolecules in Nature. Except for energy-related compounds, carbohydrates can be roughly divided into two categories: Carbohydrates as matter and carbohydrates as information. As matter, carbohydrates are abundantly present in the extracellular matrix of animals and cell walls of various plants, bacteria, fungi, etc., serving as scaffolds. Some commonly found polysaccharides are featured as biocompatible materials with controllable rigidity and functionality, forming polymeric biomaterials which are widely used in drug delivery, tissue engineering, etc. As information, carbohydrates are usually referred to the glycans from glycoproteins, glycolipids, and proteoglycans, which bind to proteins or other carbohydrates, thereby meditating the cell-cell and cell-matrix interactions. These glycans could be simplified as synthetic glycopolymers, glycolipids, and glycoproteins, which could be afforded through polymerization, multistep synthesis, or a semisynthetic strategy. The information role of carbohydrates can be demonstrated not only as targeting reagents but also as immune antigens and adjuvants. The latter are also included in this review as they are always in a macromolecular formulation. In this review, we intend to provide a relatively comprehensive summary of carbohydrate-based macromolecular biomaterials since 2010 while emphasizing the fundamental understanding to guide the rational design of biomaterials. Carbohydrate-based macromolecules on the basis of their resources and chemical structures will be discussed, including naturally occurring polysaccharides, naturally derived synthetic polysaccharides, glycopolymers/glycodendrimers, supramolecular glycopolymers, and synthetic glycolipids/glycoproteins. Multiscale structure-function relationships in several major application areas, including delivery systems, tissue engineering, and immunology, will be detailed. We hope this review will provide valuable information for the development of carbohydrate-based macromolecular biomaterials and build a bridge between the carbohydrates as matter and the carbohydrates as information to promote new biomaterial design in the near future.

Prophylactic Cancer Vaccines Engineered to Elicit Specific Adaptive Immune Response

Vaccines have been used to prevent and eradicate different diseases for over 200 years, and new vaccine technologies have the potential to prevent many common illnesses. Cancer, despite many advances in therapeutics, is still the second leading causes of death in the United States. Prophylactic, or preventative, cancer vaccines have the potential to reduce cancer prevalence by initiating a specific immune response that will target cancer before it can develop. Cancer vaccines can include many different components, such as peptides and carbohydrates, and be fabricated for delivery using a variety of means including through incorporation of stabilizing chemicals like polyethylene glycol (PEG) and pan-DR helper T-lymphocyte epitope (PADRE), fusion with antigen-presenting cells (APCs), microneedle patches, and liposomal encapsulation. There are currently five cancer vaccines used in the clinic, protecting against either human papillomavirus (HPV) or hepatitis B virus (HBV), and preventing several different types of cancer including cervical and oral cancer. Prophylactic cancer vaccines can promote three different types of adaptive responses: humoral (B cell, or antibody-mediated), cellular (T cell) or a combination of the two types. Each vaccine has its advantages and challenges at eliciting an adaptive immune response, but these prophylactic cancer vaccines in development have the potential to prevent or delay tumor development, and reduce the incidence of many common cancers.

Synthesis and immunological evaluation of synthetic peptide based anti-SARS-CoV-2 vaccine candidates

For prevention of the coronavirus disease 2019 caused by the novel coronavirus SARS-CoV-2, an effective vaccine is critical. Herein, several potential peptide epitopes from the spike protein of SARS-CoV-2 have been synthesized and covalently linked with the cross-reactive material (CRM197). Immunization of mice with the resulting conjugates induced high titers of IgG antibodies against the spike protein. Importantly, the post-immune sera effectively neutralized SARS-CoV-2 pseudovirus, suggesting the epitopes identified are protective, and these conjugates are promising leads for anti-SARS-CoV-2 vaccine development.

Synthesis of MUC1-derived glycopeptide bearing a novel triazole STn analog

The synthesis of MUC1 glycopeptides bearing modified tumor-associated carbohydrate antigens (TACAs) represents an effective strategy to develop potential antitumor vaccines that trigger strong immune response. In this context, we present herein the multistep synthesis of the triazole glycosyl amino acid Neu5Ac-α/β2-triazole-6-βGalNAc-ThrOH 1 as STn antigen analog, along with its assembly on the corresponding MUC1 peptide to give NAcProAsp [Neu5Acα/β2-triazole-6-βGalNAc]ThrArgProGlyOH 2. Despite interacting differently with SM3 monoclonal antibody, as shown by molecular dynamic simulations, this unnatural triazole glycopeptide may represent a promising candidate for cancer immunotherapy.

Efficient chemoenzymatic synthesis of fluorinated sialyl Thomsen-Friedenreich antigens and investigation of their characteristics

A set of fluorinated sialyl-T derivatives were efficiently synthesized using one-pot multi-enzyme (OPME) chemoenzymatic approach. The P. multocida α2-3-sialyltransferase (PmST1) involved in the synthesis showed extremely flexible donor and acceptor substrate specificities. These sialosides have been successfully investigated with stability towards Clostridium perfringens sialidase substrate specificity assay using ¹H NMR spectroscopy. Hydrolysis studies monitored by ¹H NMR clearly demonstrated that the fluorine substitution obviously reduced hydrolysis rate of Clostridium perfringens sialidase. To further investigate the fluorine influence, structure-dependent variation of sialoside-lectin binding was observed for MAL and different sialoside-immobilized surfaces. Subtle changes on the ligand of carbohydrate-binding protein were distinguished by SPR. These fluorinated sialyl-T derivatives obtained are valuable probes for further biological studies or antitumor drug design.

6-Deoxy-6-fluoro galactofuranosides: regioselective glycosylation, unexpected reactivity, and anti-leishmanial activity

Selective glycosylation of the C-6 fluorinated galactofuranosyl acceptor 2 was studied with four galactofuranosyl donors. It was highlighted that this electron-withdrawing atom strongly impacted the behavior of the acceptor, thus leading to unprecedented glycosylation pathways. Competition between expected glycosylation of 2, ring expansion of this acceptor and furanosylation, and intermolecular aglycon transfer was observed. Further investigation of the fluorinated synthetic compounds showed that the presence of fluorine atom contributed to increase the inhibition of the growth of Leishmania tarentolae, a non-pathogenic strain of Leishmania.