Liposomal Antitumor Vaccines Targeting Mucin 1 Elicit a Lipid-Dependent Immunodominant Response

Trichostatin A-modified vaccine provides superior protection against ovarian cancer formation and development

More attention has been paid to immunotherapy for ovarian cancer and the development of tumor vaccines. We developed a trichostatin A (TSA)-modified tumor vaccine with potent immunomodulating activities that can inhibit the growth of ovarian cancer in rats and stimulate immune cell response in vivo. TSA-treated Nutu-19 cells inactivated by X-ray radiation were used as a tumor vaccine in rat ovarian cancer models. Prophylactic and therapeutic experiments were performed with TSA-modified tumor vaccine in rats. Flow cytometry and ELISpot assays were conducted to assess immune response. Immune cell expression in the spleen and thymus were detected by immunohistochemical staining. GM-CSF, IL-7, IL-17, LIF, LIX, KC, MCP-1, MIP-2, M-CSF, IP-10/CXCL10, MIG/CXCL9, RANTES, IL-4, IFN-γ, and VEGF expressions were detected with Milliplex Map Magnetic Bead Panel immunoassay. TSA vaccination in therapeutic and prophylactic models could effectively stimulate innate immunity and boost the adaptive humoral and cell-mediated immune responses to inhibit the growth and tumorigenesis of ovarian cancer. This vaccine stimulated the thymus into reactivating status and enhanced infiltrating lymphocytes in tumor-bearing rats. The expression of key immunoregulatory factors were upregulated in the vaccine group. The intensities of infiltrating CD4+ and CD8+ T cells and NK cells were significantly increased in the vaccine group compared to the control group (P<0.05). This protection was mainly dependent on the IFN-γ pathway and, to a much lesser extent, by the IL-4 pathway. The tumor cells only irradiated by X-ray as the control group still showed a slight immune effect, indicating that irradiated cells may also cause certain immune antigen exposure, but the efficacy was not as significant as that of the TSA-modified tumor vaccine. Our study revealed the potential application of the TSA-modified tumor vaccine as a novel tumor vaccine against tumor refractoriness and growth. These findings offer a better understanding of the immunomodulatory effects of the vaccine against latent tumorigenesis and progression. This tumor vaccine therapy may increase antigen exposure, synergistically activate the immune system, and ultimately improve remission rates. A vaccine strategy designed to induce effective tumor immune response is being considered for cancer immunotherapy.

Antigen/Adjuvant-Displaying Enveloped Viral Replica as a Self-Adjuvanting Anti-Breast-Cancer Vaccine Candidate

We report a promising cancer vaccine candidate comprising antigen/adjuvant-displaying enveloped viral replica as a novel vaccine platform. The artificial viral capsid, which consists of a self-assembled β-annulus peptide conjugated with an HER2-derived antigenic CH401 peptide, was enveloped within a lipid bilayer containing the lipidic adjuvant α-GalCer. The use of an artificial viral capsid as a scaffold enabled precise control of its size to ∼100 nm, which is generally considered to be optimal for delivery to lymph nodes. The encapsulation of the anionically charged capsid by a cationic lipid bilayer dramatically improved its stability and converted its surface charge to cationic, enhancing its uptake by dendritic cells. The developed CH401/α-GalCer-displaying enveloped viral replica exhibited remarkable antibody-production activity. This study represents a pioneering example of precise vaccine design through bottom-up construction and opens new avenues for the development of effective vaccines.

Self-Adjuvanting Protein Vaccine Conjugated with a Novel Synthetic TLR4 Agonist on Virus-Like Liposome Induces Potent Immunity against SARS-CoV-2

Exploring potent adjuvants and new vaccine strategies is crucial for the development of protein vaccines. In this work, we synthesized a new TLR4 agonist, structurally simplified lipid A analogue GAP112, as a potent built-in adjuvant to improve the immunogenicity of SARS-CoV-2 spike RBD protein. The new TLR4 agonist GAP112 was site-selectively conjugated on the N-terminus of RBD to construct an adjuvant-protein conjugate vaccine in a liposomal formulation. It is the first time that a TLR4 agonist is site-specifically and quantitatively conjugated to a protein antigen. Compared with an unconjugated mixture of GAP112/RBD, a two-dose immunization of the GAP112-RBD conjugate vaccine strongly activated innate immune cells, elicited a 223-fold increase in RBD-specific antibodies, and markedly enhanced T-cell responses. Antibodies induced by GAP112-RBD also effectively cross-neutralized SARS-CoV-2 variants (Delta/B.1.617.2 and Omicron/B.1.1.529). This conjugate strategy provides an effective method to greatly enhance the immunogenicity of antigen in protein vaccines against SARS-CoV-2 and other diseases.

Innovative Vaccine Strategy: Self-Adjuvanting Conjugate Vaccines

Self-adjuvanting vaccines, covalent conjugates between antigens and adjuvants, are chemically well-defined compared with conventional vaccines formulated through mixing antigens with adjuvants. Innate immune receptor ligands effectively induce acquired immunity through the activation of innate immunity, thereby enhancing host immune responses. Thus, innate immune receptor ligands are often used as adjuvants in self-adjuvanting vaccines. In a self-adjuvanting vaccine, the covalent linkage of antigen and adjuvant enables their simultaneous uptake into immune cells where the adjuvant consequently induces antigen-specific immune responses. Importantly, self-adjuvanting vaccines do not require immobilization to carrier proteins or co-administration of additional adjuvants and thus avoid inducing undesired immune responses. Because of these excellent properties, self-adjuvanting vaccines are expected to be candidates for next-generation vaccines. Here, we take an overview of vaccine adjuvants, mainly focusing on those utilized in self-adjuvanting vaccines and then we review recent reports on self-adjuvanting conjugate vaccines.

Niosomes as Biocompatible Scaffolds for the Multivalent Presentation of Tumor-Associated Antigens (TACAs) to the Immune System

Fully synthetic tumor-associated carbohydrate antigen (TACA)-based vaccines are a promising strategy to treat cancer. To overcome the intrinsic low immunogenicity of TACAs, the choice of the antigens' analogues and multivalent presentation have been proved to be successful. Here, we present the preparation, characterization, and in vitro screening of niosomes displaying multiple copies of the mucin antigen TnThr (niosomes-7) or of TnThr mimetic 1 (niosomes-2). Unprecedentedly, structural differences, likely related to the carbohydrate portions, were observed for the two colloidal systems. Both niosomal systems are stable, nontoxic and endowed with promising immunogenic properties.

Liposome-Based Carbohydrate Vaccine for Simultaneously Eliciting Humoral and Cellular Antitumor Immunity

Tumor-associated carbohydrate antigen (TACA)-based cancer vaccines achieved promising results, whereas missing the T cell-mediated cellular immune response is still a crucial problem to be solved. Here, we have developed Tn antigen (GalNAc)-modified liposome-encapsulated TLR9 agonist CpG ODN adjuvant as a cancer vaccine. The glyco-liposome vaccines exhibit strong binding ability with an anti-Tn specific antibody and enhance antigen presentation of both bone marrow-derived dendritic cells (BMDCs) and spleen B cells. In vivo immunogenicity studies have demonstrated that the glyco-liposome vaccines can significantly enhance the generation of high anti-Tn antigen antibody titers and further induce a Th1-dependent cellular immune response, evidenced by IFN-γ secretion in an immune coculture of immunized T cells with Tn-expression 4T1 cancer cells. Collectively, our results highlight a liposome-based carbohydrate vaccine as a promising platform, which can simultaneously elicit both humoral and cellular antitumor immunity.

Recent advances and future perspectives on carbohydrate-based cancer vaccines and therapeutics

Carbohydrates are abundantly expressed on the surface of both eukaryotic and prokaryotic cells, often as post translational modifications of proteins. Glycoproteins are recognized by the immune system and can trigger both innate and humoral responses. This feature has been harnessed to generate vaccines against polysaccharide-encapsulated bacteria such as Streptococcus pneumoniae, Hemophilus influenzae type b and Neisseria meningitidis. In cancer, glycosylation plays a pivotal role in malignancy development and progression. Since glycans are specifically expressed on the surface of tumor cells, they have been targeted for the discovery of anticancer preventive and therapeutic treatments, such as vaccines and monoclonal antibodies. Despite the various efforts made over the last years, resulting in a series of clinical studies, attempts of vaccination with carbohydrate-based candidates have proven unsuccessful, primarily due to the immune tolerance often associated with these glycans. New strategies are thus deployed to enhance carbohydrate-based cancer vaccines. Moreover, lessons learned from glycan immunobiology paved the way to the development of new monoclonal antibodies specifically designed to recognize cancer-bound carbohydrates and induce tumor cell killing. Herein we provide an overview of the immunological principles behind the immune response towards glycans and glycoconjugates and the approaches exploited at both preclinical and clinical level to target cancer-associated glycans for the development of vaccines and therapeutic monoclonal antibodies. We also discuss gaps and opportunities to successfully advance glycan-directed cancer therapies, which could provide patients with innovative and effective treatments.

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.

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.

MPLA-Adjuvanted Liposomes Encapsulating S-Trimer or RBD or S1, but Not S-ECD, Elicit Robust Neutralization Against SARS-CoV-2 and Variants of Concern

Safe and effective vaccines are the best method to defeat worldwide SARS-CoV-2 and its circulating variants. The SARS-CoV-2 S protein and its subunits are the most attractive targets for the development of protein-based vaccines. In this study, we evaluated three lipophilic adjuvants, monophosphoryl lipid A (MPLA), Toll-like receptor (TLR) 1/2 ligand Pam3CSK4, and α-galactosylceramide (α-GalCer), in liposomal and nonliposomal vaccines. The immunological results showed that the MPLA-adjuvanted liposomal vaccine induced the strongest humoral and cellular immunity. Therefore, we further performed a systematic comparison of S-trimer, S-ECD, S1, and RBD as antigens in MPLA-adjuvanted liposomes and found that, although these four vaccines all induced robust specific antibody responses, only S-trimer, S1, and RBD liposomes, but not S-ECD, elicited potent neutralizing antibody responses. Moreover, RBD, S-trimer, and S1 liposomes effectively neutralized variants (B.1.1.7/alpha, B.1.351/beta, P.1/gamma, B.1.617.2/delta, and B.1.1.529/omicron). These results provide important information for the subunit vaccine design against SARS-CoV-2 and its variants.

Self-Adjuvanting Lipoprotein Conjugate αGalCer-RBD Induces Potent Immunity against SARS-CoV-2 and its Variants of Concern

Safe and effective vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its variants are the best approach to successfully combat the COVID-19 pandemic. The receptor-binding domain (RBD) of the viral spike protein is a major target to develop candidate vaccines. α-Galactosylceramide (αGalCer), a potent invariant natural killer T cell (iNKT) agonist, was site-specifically conjugated to the N-terminus of the RBD to form an adjuvant-protein conjugate, which was anchored on the liposome surface. This is the first time that an iNKT cell agonist was conjugated to the protein antigen. Compared to the unconjugated RBD/αGalCer mixture, the αGalCer-RBD conjugate induced significantly stronger humoral and cellular responses. The conjugate vaccine also showed effective cross-neutralization to all variants of concern (B.1.1.7/alpha, B.1.351/beta, P.1/gamma, B.1.617.2/delta, and B.1.1.529/omicron). These results suggest that the self-adjuvanting αGalCer-RBD has great potential to be an effective COVID-19 vaccine candidate, and this strategy might be useful for designing various subunit vaccines.

RBD conjugate vaccine with a built-in TLR1/2 agonist is highly immunogenic against SARS-CoV-2 and variants of concern

The coronavirus 2019 (COVID-19) pandemic is causing serious impacts in the world, and safe and effective vaccines and medicines are the best methods to combat the disease. The receptor-binding domain (RBD) of the SARS-CoV-2 spike protein plays a key role in interacting with the angiotensin-converting enzyme 2 (ACE2) receptor, and is regarded as an important target of vaccines. Herein, we constructed the adjuvant-protein conjugate Pam₃CSK₄-RBD as a vaccine candidate, in which the N-terminal of the RBD was site-selectively oxidized by transamination and conjugated with the TLR1/2 agonist Pam₃CSK₄. This demonstrated that the conjugation of Pam₃CSK₄ significantly enhanced the anti-RBD antibody response and cellular response. In addition, sera from the Pam₃CSK₄-RBD immunized group efficiently inhibited the binding of the RBD to ACE2 and protected cells from SARS-CoV-2 and four variants of concern (alpha, beta, gamma and delta), indicating that this adjuvant strategy could be one of the effective means for protein vaccine development.

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.

Potent Neutralizing Antibodies Elicited by RBD-Fc-Based COVID-19 Vaccine Candidate Adjuvanted by the Th2-Skewing iNKT Cell Agonist

The development of a safe and effective COVID-19 vaccine is of paramount importance to terminate the current pandemic. An adjuvant is crucial for improving the efficacy of the subunit COVID19 vaccine. α-Galactosylceramide (αGC) is a classical iNKT cell agonist which causes the rapid production of Th1- and Th2-associated cytokines; we, therefore, expect that the Th1- or Th2-skewing analogues of αGC can better enhance the immunogenicity of the receptor-binding domain in the spike protein of SARS-CoV-2 fused with the Fc region of human IgG (RBD-Fc). Herein, we developed a universal synthetic route to the Th1-biasing (α-C-GC) and Th2-biasing (OCH and C20:2) analogues. Immunization of mice demonstrated that αGC-adjuvanted RBD-Fc elicited a more potent humoral response than that observed with Alum and enabled the sparing of antigens. Remarkably, at a low dose of the RBD-Fc protein (2 μg), the Th2-biasing agonist C20:2 induced a significantly higher titer of the neutralizing antibody than that of Alum.

Harnessing NKT cells for vaccination

Natural killer T (NKT) cells are innate-like T cells capable of enhancing both innate and adaptive immune responses. When NKT cells are stimulated in close temporal association with co-administered antigens, strong antigen-specific immune responses can be induced, prompting the study of NKT cell agonists as novel immune adjuvants. This activity has been attributed to the capacity of activated NKT cells to act as universal helper cells, with the ability to provide molecular signals to dendritic cells and B cells that facilitate T cell and antibody responses, respectively. These signals can override the requirement for conventional CD4⁺ T cell help, so that vaccines can be designed without need to consider CD4⁺ T cell repertoire and major histocompatibility complex Class II diversity. Animal studies have highlighted some drawbacks of the approach, namely, concerns around induction of NKT cell hyporesponsiveness, which may limit vaccine boosting, and potential for toxicity. Here we highlight studies that suggest these obstacles can be overcome by targeted delivery in vivo. We also feature new studies that suggest activating NKT cells can help encourage differentiation of T cells into tissue-resident memory cells that play an important role in prophylaxis against infection, and may be required in cancer therapy.

Mucins as anti-cancer targets: perspectives of the glycobiologist

Mucins are highly O-glycosylated glycoproteins that carry a heterogenous variety of O-glycan structures. Tumor cells tend to overexpress specific mucins, such as the cell surface mucins MUC1 and MUC4 that are engaged in signaling and cell growth, and exhibit abnormal glycosylation. In particular, the Tn and T antigens and their sialylated forms are common in cancer mucins. We review herein methods chosen to use cancer-associated glycans and mucins as targets for the design of anti-cancer immunotherapies. Mucin peptides from the glycosylated and transmembrane domains have been combined with immune-stimulating adjuvants in a wide variety of approaches to produce anti-tumor antibodies and vaccines. These mucin conjugates have been tested on cancer cells in vitro and in mice with significant successes in stimulating anti-tumor responses. The clinical trials in humans, however, have shown limited success in extending survival. It seems critical that the individual-specific epitope expression of cancer mucins is considered in future therapies to result in lasting anti-tumor responses.

Synthesis and Evaluation of Liposomal Anti-GM3 Cancer Vaccine Candidates Covalently and Noncovalently Adjuvanted by αGalCer

GM3, a typical tumor-associated carbohydrate antigen, is considered as an important target for cancer vaccine development, but its low immunogenicity limits its application. αGalCer, an iNKT cell agonist, has been employed as an adjuvant via a unique immune mode. Herein, we prepared and investigated two types of antitumor vaccine candidates: (a) self-adjuvanting vaccine GM3-αGalCer by conjugating GM3 with αGalCer and (b) noncovalent vaccine GM3-lipid/αGalCer, in which GM3 is linked with lipid anchor and coassembled with αGalCer. This demonstrated that βGalCer is an exceptionally optimized lipid anchor, which enables the noncovalent vaccine candidate GM3-βGalCer/αGalCer to evoke a comparable antibody level to GM3-αGalCer. However, the antibodies induced by GM3-αGalCer are better at recognition B16F10 cancer cells and more effectively activate the complement system. Our study highlights the importance of vaccine constructs utilizing covalent or noncovalent assembly between αGalCer with carbohydrate antigens and choosing an appropriate lipid anchor for use in noncovalent vaccine formulation.

Recent advances in self-adjuvanting glycoconjugate vaccines

Compared to traditional vaccines that are formulated into mixtures of an adjuvant and an antigen, a self-adjuvanting vaccine consists of an antigen that is covalently conjugated to a well-defined adjuvant. In self-adjuvanting vaccines, innate immune receptor ligands are usually used as adjuvants. Innate immune receptor ligands effectively trigger acquired immunity through the activation of innate immunity to enhance host immune responses to antigens. When a self-adjuvanting vaccine is used, immune cells simultaneously uptake the antigen and the adjuvant because they are covalently linked. Consequently, the adjuvant can specifically induce immune responses against the conjugated antigen. Importantly, self-adjuvanting vaccines do not require co-administration of additional adjuvants or immobilization to carrier proteins, which enables avoidance of the use of highly toxic adjuvants or the induction of undesired immune responses. Given these excellent properties, self-adjuvanting vaccines are expected to serve as candidates for the next generation of vaccines. Herein, we review vaccine adjuvants, with a focus on the adjuvants used in self-adjuvanting vaccines, and then overview recent advances made with self-adjuvanting conjugate vaccines.

Immunological Evaluation of Co-Assembling a Lipidated Peptide Antigen and Lipophilic Adjuvants: Self-Adjuvanting Anti-Breast-Cancer Vaccine Candidates

Co-assembling vaccines composed of a lipidated HER2-derived antigenic CH401 peptide and either a lipophilic adjuvant, Pam₃ CSK₄ , α-GalCer, or lipid A 506, were evaluated as breast cancer vaccine candidates. This vaccine design was aimed to inherit both antigen multivalency and antigen-specific immunostimulation properties, observed in reported self-adjuvanting vaccine candidates, by using self-assembly and adjuvant-conjugated antigens. Under vaccination concentrations, respective lipophilic adjuvants underwent co-assembly with lipidated CH401, which boosted the anti-CH401 IgG and IgM production. In particular, α-GalCer was responsible for the most significant immune activation. Therefore, the newly developed vaccine design enabled the optimization of adjuvants against the antigenic CH401 peptide in a simple preparatory manner. Overall, the co-assembling vaccine design opens the door for efficient and practical self-adjuvanting vaccine development.

Design, Synthesis, and Preliminary Immunological Studies of MUC1-Based Antitumor Vaccines Adjuvanted with R- and S-FSL-1

Fibroblast stimulating lipopeptide 1 (FSL-1) is the ligand of TLR2 and TLR6 and can be used as the vaccine adjuvant to prepare antitumor vaccines. However, FSL-1 is a stereoisomeric mixture that contains the R stereoisomer and S stereoisomer, and it is still unclear which stereoisomer has better adjuvant activities. In this work, we designed and synthesized MUC1-based antitumor vaccines adjuvanted with the stereoisomers R-FSL-1 and S-FSL-1, which were synthesized from the stereoisomeric building blocks R-Fmoc-Pam₂Cys-OH and S-Fmoc-Pam₂Cys-OH, respectively. Immunological evaluation indicated that both R-FSL-1 and S-FSL-1 can be used as adjuvants for the construction of MUC1-based antitumor vaccines, with R-FSL-1 showing a better adjuvant effect than S-FSL-1.

Improved efficacy of doxorubicin delivery by a novel dual-ligand-modified liposome in hepatocellular carcinoma

Liposomes have been widely used as drug carriers in both biomedical research and for clinical applications, allowing the stabilisation of therapeutic compounds and overcoming obstacles to cellular and tissue uptake. However, liposomes still have low targeting efficiency, resulting in insufficient killing of tumour cells and unnecessary damage to normal cells. In this study, glycyrrhetinic acid (GA) and peanut agglutinin (PNA) were used as ligands to prepare dual-ligand-modified doxorubicin-loaded liposomes (DOX-GA/PNA-Lips) to enhance the targeting accuracy and efficacy of drug delivery against malignant liver cancer. PNA and GA modification enhanced the binding ability of liposomes to liver cancer cells, leading to excellent tissue and cell targeting of DOX-GA/PNA-Lips. DOX-GA/PNA-Lips showed an effective anti-tumour effect in vivo and in vitro, with its targeted delivery facilitating attenuation of the toxic side effects of DOX. These results demonstrated that dual-ligand-modified liposomes may provide an effective strategy for the treatment of hepatocellular carcinoma.

Multifunctional Protein Conjugates with Built-in Adjuvant (Adjuvant-Protein-Antigen) as Cancer Vaccines Boost Potent Immune Responses

Many cancer vaccines are not successful in clinical trials, mainly due to the challenges associated with breaking immune tolerance. Herein, we report a new strategy using an adjuvant-protein-antigen (three-in-one protein conjugates with built-in adjuvant) as an anticancer vaccine, in which both the adjuvant (small-molecule TLR7 agonist) and tumor-associated antigen (mucin 1, MUC1) are covalently conjugated to the same carrier protein (BSA). It is shown that the protein conjugates with built-in adjuvant can increase adjuvant's stimulation, prevent adjuvant's systemic toxicities, facilitate the codelivery of adjuvants and antigens, and enhance humoral and cellular immune responses. The IgG antibody titers elicited by the self-adjuvanting three-in-one protein conjugates were significantly higher than those elicited by the vaccine mixed with TLR7 agonist (more than 15-fold) or other traditional adjuvants. Importantly, the potent immune responses against cancer cells suggest that this new vaccine construct is an effective strategy for the personalized antitumor immunotherapy.

•

Adjuvant-protein-antigen protein conjugates act as new cancer vaccine strategy

•

Built-in adjuvant of TLR7 agonist can reduce toxicities and enhance immune stimulations

•

Three-in-one protein conjugates boost potent immune responses against cancer cells

Tumor-associated O-glycans of MUC1: Carriers of the glyco-code and targets for cancer vaccine design

The transformation from normal to malignant phenotype in human cancers is associated with aberrant cell-surface glycosylation. It has frequently been reported that MUC1, the heavily glycosylated cell-surface mucin, is altered in both, expression and glycosylation pattern, in human carcinomas of the epithelium. The presence of incomplete or truncated glycan structures, often capped by sialic acid, commonly known as tumor-associated carbohydrate antigens (TACAs), play a key role in tumor initiation, progression, and metastasis. Accumulating evidence suggests that expression of TACAs is associated with tumor escape from immune defenses. In this report, we will give an overview of the oncogenic functions of MUC1 that are exerted through TACA interactions with endogenous carbohydrate-binding proteins (lectins). These interactions often lead to creation of a pro-tumor microenvironment, favoring tumor progression and metastasis, and tumor evasion. In addition, we will describe current efforts in the design of cancer vaccines with special emphasis on synthetic MUC1 glycopeptide vaccines. Analysis of the key factors that govern structure-based design of immunogenic MUC1 glycopeptide epitopes are described. The role of TACA type, position, and density on observed humoral and cellular immune responses is evaluated.