Effect of TLR ligands co-encapsulated with multiepitopic antigen in nanoliposomes targeted to human DCs via Fc receptor for cancer vaccines

Advancements in Nanoparticle-Based Adjuvants for Enhanced Tuberculosis Vaccination: A Review

Tuberculosis (TB) remains a leading cause of morbidity and mortality worldwide, necessitating the development of more effective vaccines. Nanoparticle-based adjuvants represent a promising approach to enhancing tuberculosis vaccine efficacy. This review focuses on the advantages of nanoparticulate-loaded vaccines, emphasizing their ability to improve antigen delivery, safety, and immunogenicity. We discuss the various types of nanoparticles and their unique physicochemical properties that contribute to improved antigen delivery and sustained immune activation. Additionally, we highlight the advantages of nanoparticle-based adjuvants in inducing strong cellular and humoral immunity, enhancing vaccine stability, and reducing adverse effects. Finally, we address current challenges and future perspectives in the application of these novel adjuvants, emphasizing their potential to transform TB vaccine strategies and ultimately contribute to better global health outcomes.

Immunologically effective biomaterials enhance immunotherapy of prostate cancer

Prostate cancer (PCa) is one of the most common malignant neoplasms affecting the male population. The onset of the disease is insidious and often associated with severe consequences, such as bone metastases at the time of initial diagnosis. Once it advances to metastatic castration-resistant PCa (mCRPC), conventional treatment methods become ineffective. As research on the mechanism of tumor therapy advances, immunotherapy has been evolving rapidly. However, PCa is a solid tumor type that primarily faces the challenges of poor immunogenicity and inhibitory tumor microenvironment (TME). Fortunately, the extensive use of biomaterials has led to continuous advancement in PCa immunotherapy. These innovative materials aim to address intractable issues, such as immune escape and immune desert, to inhibit tumor progression and metastasis. This detailed review focuses on the regulation of different aspects of tumor immunity by immunologically effective biomaterials, including modulating adaptive immunity, innate immunity, and the immune microenvironment, to enhance the efficacy of PCa immunotherapy. In addition, this review provides a perspective on the future prospects of immunotherapeutic nanoplatforms based on biomaterials in the treatment of PCa.

Nanovaccines: Immunogenic tumor antigens, targeted delivery, and combination therapy to enhance cancer immunotherapy

Nanovaccines have been designed to overcome the limitations associated with conventional vaccines. Effective delivery methods such as engineered carriers or smart nanoparticles (NPs) are critical requisites for inducing self-tolerance and optimizing vaccine immunogenicity with minimum side effects. NPs can be used as adjuvants, immunogens, or nanocarriers to develop nanovaccines for efficient antigen delivery. Multiloaded nanovaccines carrying multiple tumor antigens along with immunostimulants can effectively increase immunity against tumor cells. They can be biologically engineered to boost interactions with dendritic cells and to allow a gradual and constant antigen release. Modifying NPs surface properties, using high-density lipoprotein-mimicking nanodiscs, and developing nano-based artificial antigen-presenting cells such as dendritic cell-derived-exosomes are amongst the new developed technologies to enhance antigen-presentation and immune reactions against tumor cells. The present review provides an overview on the different perspectives, improvements, and barriers of successful clinical application of current cancer therapeutic and vaccination options. The immunomodulatory effects of different types of nanovaccines and the nanoparticles incorporated into their structure are described. The advantages of using nanovaccines to prevent and treat common illnesses such as AIDS, malaria, cancer and tuberculosis are discussed. Further, potential paths to develop optimal cancer vaccines are described. Given the immunosuppressive characteristics of both cancer cells and the tumor microenvironment, applying immunomodulators and immune checkpoint inhibitors in combination with other conventional anticancer therapies are necessary to boost the effectiveness of the immune response.

Dendritic cell-targeting polymer nanoparticle-based immunotherapy for cancer: A review

Cancer immunity is dependent on dynamic interactions between T cells and dendritic cells (DCs). Polymer-based nanoparticles target DC receptors to improve anticancer immune responses. In this paper, DC surface receptors and their specific coupling natural ligands and antibodies are reviewed and compared. Moreover, reaction mechanisms are described, and the synergistic effects of immune adjuvants are demonstrated. Also, extracellular-targeting antigen-delivery strategies and intracellular stimulus responses are reviewed to promote the rational design of polymer delivery systems.

Tyrosinase-Related Protein2 Peptide with Replacement of N-Terminus Residue by Cysteine Binds to H-2Kb and Induces Antigen-Specific Cytotoxic T Lymphocytes after Conjugation with CpG-DNA

Recent studies have shown the potent efficacy of peptide-based vaccines for cancer immunotherapy. Immunological performance is optimized through the co-delivery of adjuvant and antigenic peptide molecules to antigen-presenting cells simultaneously. In our previous study, we showed that a conjugate consisting of 40-mer CpG-DNA and an antigenic ovalbumin peptide through disulfide bonding could efficiently induce ovalbumin-specific cytotoxic T lymphocyte (CTL) responses in vivo. In this study, based on the conjugation design, we prepared a conjugate consisting of 30-mer CpG-DNA (CpG30) and a cancer antigenic peptide of Tyrosinase-related protein 2 (TRP2_180-188) using a cysteine residue attached at the N-terminus of TRP2_180-188. However, the immunization of mice with this conjugate did not induce efficient TRP2_180-188-specific immune responses. It was thought that the resultant peptide (10-mer) cleaved from the conjugate might be too long to fit into the H-2K^b molecule because the optimal length for binding to it is 8-9 amino acids. We newly designed a conjugate consisting of CpG30 and the C-TRP2_181-188 peptide (9-mer), in which the N-terminal serine residue of TRP2_180-188 is replaced by a cysteine. By adjusting the peptide length, we succeeded in inducing strong TRP2_180-188 peptide-specific CTL activity upon immunization with the CpG30-C-TRP2_181-188 conjugate. Furthermore, various CpG30-C-TRP2_181-188 conjugates having other CpG-DNA sequences or cysteine analogues also induced the same level of CTL activity. Therefore, CpG-C-peptide conjugates prepared by replacement of the amino acid residue at the N-terminus with a cysteine residue could be a new and effective platform for peptide vaccines for targeting specific antigens of cancers and infectious diseases.

Innate sensing and cellular metabolism: role in fine tuning antiviral immune responses

Several studies over the last decade have identified intimate links between cellular metabolism and macrophage function. Metabolism has been shown to both drive and regulate macrophage function by producing bioenergetic and biosynthetic precursors as well as metabolites (and other bioactive molecules) that regulate gene expression and signal transduction. Many studies have focused on lipopolysaccharide-induced reprogramming, assuming that it is representative of most inflammatory responses. However, emerging evidence suggests that diverse pathogen-associated molecular patterns (PAMPs) are associated with unique metabolic profiles, which may drive pathogen specific immune responses. Further, these metabolic pathways and processes may act as a rheostat to regulate the magnitude of an inflammatory response based on the biochemical features of the local microenvironment. In this review, we will discuss recent work examining the relationship between cellular metabolism and macrophage responses to viral PAMPs and describe how these processes differ from lipopolysaccharide-associated responses. We will also discuss how an improved understanding of the specificity of these processes may offer new insights to fine-tune macrophage function during viral infections or when using viral PAMPs as therapeutics.

Application of lipid-based nanoparticles in cancer immunotherapy

Immunotherapy is revolutionizing the clinical management of patients with different cancer types by sensitizing autologous or allogenic immune cells to the tumor microenvironment which eventually leads to tumor cell lysis without rapidly killing normal cells. Although immunotherapy has been widely demonstrated to be superior to chemotherapies, only a few populations of patients with specific cancer types respond to such treatment due to the failure of systemic immune activation. In addition, severe immune-related adverse events are rapidly observed when patients with very few responses are given higher doses of such therapies. Recent advances of lipid-based nanoparticles (NPs) development have made it possible to deliver not only small molecules but also mRNAs to achieve systemic anticancer immunity through cytotoxic immune cell activation, checkpoint blockade, and chimeric antigen receptor cell therapies, etc. This review summarized recent development and applications of LNPs in anticancer immunotherapy. The diversity of lipid-based NPs would encapsulate payloads with different structures and molecular weights to achieve optimal antitumor immunity through multiple mechanisms of action. The discussion about the components of lipid-based NPs and their immunologic payloads in this review hopefully shed more light on the future direction of anticancer immunotherapy.

Optically Coupled PtOEP and DPA Molecules Encapsulated into PLGA-Nanoparticles for Cancer Bioimaging

Triplet-triplet annihilation upconversion (TTA-UC) nanoparticles (NPs) have emerged as imaging probes and therapeutic probes in recent years due to their excellent optical properties. In contrast to lanthanide ion-doped inorganic materials, highly efficient TTA-UC can be generated by low excitation power density, which makes it suitable for clinical applications. In the present study, we used biodegradable poly(lactic-co-glycolic acid) (PLGA)-NPs as a delivery vehicle for TTA-UC based on the heavy metal porphyrin Platinum(II) octaethylporphyrin (PtOEP) and the polycyclic aromatic hydrocarbon 9,10-diphenylanthracene (DPA) as a photosensitizer/emitter pair. TTA-UC-PLGA-NPs were successfully synthesized according to an oil-in-water emulsion and solvent evaporation method. After physicochemical characterization, UC-efficacy of TTA-UC-PLGA-NPs was assessed in vitro and ex vivo. TTA-UC could be detected in the tumour area 96 h after in vivo administration of TTA-UC-PLGA-NPs, confirming the integrity and suitability of PLGA-NPs as a TTA-UC in vivo delivery system. Thus, this study provides proof-of-concept that the advantageous properties of PLGA can be combined with the unique optical properties of TTA-UC for the development of advanced nanocarriers for simultaneous in vivo molecular imaging and drug delivery.

Development of Peptide-Based Vaccines for Cancer

Peptides cancer vaccines are designed based on the epitope peptides that can elicit humoral and cellular immune responses targeting tumor-associated antigens (TAAs) or tumor-specific antigens (TSAs). In order to develop a clinically safe and more effective vaccine for the future, several issues need to be addressed, and these include the selection of optimal antigen targets, adjuvants, and immunization regimens. Another emerging approach involves the use of personalized peptide-based vaccines based on neoantigens to enhance antitumor response. Rationally designed combinatorial therapy is currently being investigated with chemotherapeutic drugs or immune checkpoint inhibitor therapies to improve the efficacy. This review discusses an overview of the development of peptide-based vaccines, the role of adjuvants, and the delivery systems for peptide vaccines as well as combinatorial therapy as potential anticancer strategies.

Smart Lipid-Based Nanosystems for Therapeutic Immune Induction against Cancers: Perspectives and Outlooks

Cancer immunotherapy, a promising and widely applied mode of oncotherapy, makes use of immune stimulants and modulators to overcome the immune dysregulation present in cancer, and leverage the host's immune capacity to eliminate tumors. Although some success has been seen in this field, toxicity and weak immune induction remain challenges. Liposomal nanosystems, previously used as targeting agents, are increasingly functioning as immunotherapeutic vehicles, with potential for delivery of contents, immune induction, and synergistic drug packaging. These systems are tailorable, multifunctional, and smart. Liposomes may deliver various immune reagents including cytokines, specific T-cell receptors, antibody fragments, and immune checkpoint inhibitors, and also present a promising platform upon which personalized medicine approaches can be built, especially with preclinical and clinical potentials of liposomes often being frustrated by inter- and intrapatient variation. In this review, we show the potential of liposomes in cancer immunotherapy, as well as the methods for synthesis and in vivo progression thereof. Both preclinical and clinical studies are included to comprehensively illuminate prospects and challenges for future research and application.

Functionalized Nanoparticles Targeting Tumor-Associated Macrophages as Cancer Therapy

The tumor microenvironment (TME) plays a central role in regulating antitumor immune responses. As an important part of the TME, alternatively activated type 2 (M2) macrophages drive the development of primary and secondary tumors by promoting tumor cell proliferation, tumor angiogenesis, extracellular matrix remodeling and overall immunosuppression. Immunotherapy approaches targeting tumor-associated macrophages (TAMs) in order to reduce the immunosuppressive state in the TME have received great attention. Although these methods hold great potential for the treatment of several cancers, they also face some limitations, such as the fast degradation rate of drugs and drug-induced cytotoxicity of organs and tissues. Nanomedicine formulations that prevent TAM signaling and recruitment to the TME or deplete M2 TAMs to reduce tumor growth and metastasis represent encouraging novel strategies in cancer therapy. They allow the specific delivery of antitumor drugs to the tumor area, thereby reducing side effects associated with systemic application. In this review, we give an overview of TAM biology and the current state of nanomedicines that target M2 macrophages in the course of cancer immunotherapy, with a specific focus on nanoparticles (NPs). We summarize how different types of NPs target M2 TAMs, and how the physicochemical properties of NPs (size, shape, charge and targeting ligands) influence NP uptake by TAMs in vitro and in vivo in the TME. Furthermore, we provide a comparative analysis of passive and active NP-based TAM-targeting strategies and discuss their therapeutic potential.

DEC-205 receptor-mediated long-circling nanoliposome as an antigen and Eucommia ulmoides polysaccharide delivery system enhances the immune response via facilitating dendritic cells maturation

DEC-205 receptor-mediated dendritic cells (DC) targeting nanoliposomes is a promising delivery system in eliciting an immune response against pathogens. When this delivery system carries both antigen and immunomodulator, it can effectively regulate the DC function as well as the initial T cell response. To maximize the desired therapeutic effects of Eucommia ulmoides Oliv. polysaccharides (EUPS), and induce an efficient humoral and cellular immune response against an antigen, we encapsulated the OVA and EUPS in long-circling nanoliposomes and conjugated it with anti-DEC-205 receptor antibody to obtain a DEC-205-targeted nanoliposomes (anti-DEC-205-EUPS-OVA-LPSM). The physicochemical properties and immune-modulating effects were investigated in vitro and in vivo by a series of the experiment to evaluate the targeting efficiency of anti-DEC-205-EUPS-OVA-LPSM. In vitro, anti-DEC-205-EUPS-OVA-LPSM (160 μg mL⁻¹) could enhance DCs proliferation and increase their phagocytic efficiency. In vivo anti-DEC-205-EUPS-OVA-LPSM remarkably promoted the OVA-specific IgG and IgG isotypes levels, enhanced the splenocyte proliferation, and induced the NK cell and CTL cytotoxicity. Besides, the anti-DEC-205-EUPS-OVA-LPSM enhanced the maturation of DCs. These findings suggest that the DEC-205 receptor antibody-conjugated EUPS nanoliposome can act as an efficient antigen delivery system to enhance the cellular and humoral immune response by promoting DC maturation. This indicates that the anti-DEC-205-EUPS-OVA-LPSM has significant potential as an immune-enhancing agent and antigen delivery system.

Lipid-Based Nanoparticles for Delivery of Vaccine Adjuvants and Antigens: Toward Multicomponent Vaccines

Despite the many advances that have occurred in the field of vaccine adjuvants, there are still unmet needs that may enable the development of vaccines suitable for more challenging pathogens (e.g., HIV and tuberculosis) and for cancer vaccines. Liposomes have already been shown to be highly effective as adjuvant/delivery systems due to their versatility and likely will find further uses in this space. The broad potential of lipid-based delivery systems is highlighted by the recent approval of COVID-19 vaccines comprising lipid nanoparticles with encapsulated mRNA. This review provides an overview of the different approaches that can be evaluated for the design of lipid-based vaccine adjuvant/delivery systems for protein, carbohydrate, and nucleic acid-based antigens and how these strategies might be combined to develop multicomponent vaccines.

Beyond Just Peptide Antigens: The Complex World of Peptide-Based Cancer Vaccines

Peptide-based cancer vaccines rely upon the strong activation of the adaptive immune response to elicit its effector function. They have shown to be highly specific and safe, but have yet to prove themselves as an efficacious treatment for cancer in the clinic. This is for a variety of reasons, including tumour heterogeneity, self-tolerance, and immune suppression. Importance has been placed on the overall design of peptide-based cancer vaccines, which have evolved from simple peptide derivatives of a cancer antigen, to complex drugs; incorporating overlapping regions, conjugates, and delivery systems to target and stimulate different components of antigen presenting cells, and to bolster antigen cross-presentation. Peptide-based cancer vaccines are increasingly becoming more personalised to an individual's tumour antigen repertoire and are often combined with existing cancer treatments. This strategy ultimately aids in combating the shortcomings of a more generalised vaccine strategy and provides a comprehensive treatment, taking into consideration cancer cell variability and its ability to avoid immune interrogation.

Mimicking Pathogens to Augment the Potency of Liposomal Cancer Vaccines

Liposomes have emerged as interesting vehicles in cancer vaccination strategies as their composition enables the inclusion of both hydrophilic and hydrophobic antigens and adjuvants. In addition, liposomes can be decorated with targeting moieties to further resemble pathogenic particles that allow for better engagement with the immune system. However, so far liposomal cancer vaccines have not yet reached their full potential in the clinic. In this review, we summarize recent preclinical studies on liposomal cancer vaccines. We describe the basic ingredients for liposomal cancer vaccines, tumor antigens, and adjuvants, and how their combined inclusion together with targeting moieties potentially derived from pathogens can enhance vaccine immunogenicity. We discuss newly identified antigen-presenting cells in humans and mice that pose as promising targets for cancer vaccines. The lessons learned from these preclinical studies can be applied to enhance the efficacy of liposomal cancer vaccination in the clinic.

Mesoporous Silica Nanoparticles as pH-Responsive Carrier for the Immune-Activating Drug Resiquimod Enhance the Local Immune Response in Mice

Nanoparticle-based delivery systems for cancer immunotherapies aim to improve the safety and efficacy of these treatments through local delivery to specialized antigen-presenting cells (APCs). Multifunctional mesoporous silica nanoparticles (MSNs), with their large surface areas, their tunable particle and pore sizes, and their spatially controlled functionalization, represent a safe and versatile carrier system. In this study, we demonstrate the potential of MSNs as a pH-responsive drug carrier system for the anticancer immune-stimulant R848 (resiquimod), a synthetic Toll-like receptor 7 and 8 agonist. Equipped with a biotin-avidin cap, the tailor-made nanoparticles showed efficient stimuli-responsive release of their R848 cargo in an environmental pH of 5.5 or below. We showed that the MSNs loaded with R848 were rapidly taken up by APCs into the acidic environment of the lysosome and that they potently activated the immune cells. Upon subcutaneous injection into mice, the particles accumulated in migratory dendritic cells (DCs) in the draining lymph nodes, where they strongly enhanced the activation of the DCs. Furthermore, simultaneous delivery of the model antigen OVA and the adjuvant R848 by MSNs resulted in an augmented antigen-specific T-cell response. The MSNs significantly improved the pharmacokinetic profile of R848 in mice, as the half-life of the drug was increased 6-fold, and at the same time, the systemic exposure was reduced. In summary, we demonstrate that MSNs represent a promising tool for targeted delivery of the immune modulator R848 to APCs and hold considerable potential as a carrier for cancer vaccines.

Peptide-based therapeutic cancer vaccine: Current trends in clinical application

The peptide‐based therapeutic cancer vaccines have attracted enormous attention in recent years as one of the effective treatments of tumour immunotherapy. Most of peptide‐based vaccines are based on epitope peptides stimulating CD8⁺ T cells or CD4⁺ T helper cells to target tumour‐associated antigens (TAAs) or tumour‐specific antigens (TSAs). Some adjuvants and nanomaterials have been exploited to optimize the efficiency of immune response of the epitope peptide to improve its clinical application. At present, numerous peptide‐based therapeutic cancer vaccines have been developed and achieved significant clinical benefits. Similarly, the combination of peptide‐based vaccines and other therapies has demonstrated a superior efficacy in improving anti‐cancer activity. We delve deeper into the choices of targets, design and screening of epitope peptides, clinical efficacy and adverse events of peptide‐based vaccines, and strategies combination of peptide‐based therapeutic cancer vaccines and other therapies. The review will provide a detailed overview and basis for future clinical application of peptide‐based therapeutic cancer vaccines.

Liposome-Based Drug Delivery Systems in Cancer Immunotherapy

Cancer immunotherapy has shown remarkable progress in recent years. Nanocarriers, such as liposomes, have favorable advantages with the potential to further improve cancer immunotherapy and even stronger immune responses by improving cell type-specific delivery and enhancing drug efficacy. Liposomes can offer solutions to common problems faced by several cancer immunotherapies, including the following: (1) Vaccination: Liposomes can improve the delivery of antigens and other stimulatory molecules to antigen-presenting cells or T cells; (2) Tumor normalization: Liposomes can deliver drugs selectively to the tumor microenvironment to overcome the immune-suppressive state; (3) Rewiring of tumor signaling: Liposomes can be used for the delivery of specific drugs to specific cell types to correct or modulate pathways to facilitate better anti-tumor immune responses; (4) Combinational therapy: Liposomes are ideal vehicles for the simultaneous delivery of drugs to be combined with other therapies, including chemotherapy, radiotherapy, and phototherapy. In this review, different liposomal systems specifically developed for immunomodulation in cancer are summarized and discussed.

Development of multi-epitope peptide-based vaccines against SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a pandemic involving so far more than 22 million infections and 776,157 deaths. Effective vaccines are urgently needed to prevent SARS-CoV-2 infections. No vaccines have yet been approved for licensure by regulatory agencies. Even though host immune responses to SARS-CoV-2 infections are beginning to be unravelled, effective clearance of virus will depend on both humoral and cellular immunity. Additionally, the presence of Spike (S)-glycoprotein reactive CD4+ T-cells in the majority of convalescent patients is consistent with its significant role in stimulating B and CD8+ T-cells. The search for immunodominant epitopes relies on experimental evaluation of peptides representing the epitopes from overlapping peptide libraries which can be costly and labor-intensive. Recent advancements in B- and T-cell epitope predictions by bioinformatic analysis have led to epitope identifications. Assessing which peptide epitope can induce potent neutralizing antibodies and robust T-cell responses is a prerequisite for the selection of effective epitopes to be incorporated in peptide-based vaccines. This review discusses the roles of B- and T-cells in SARS-CoV-2 infections and experimental validations for the selection of B-, CD4+ and CD8+ T-cell epitopes which could lead to the construction of a multi-epitope peptide vaccine. Peptide-based vaccines are known for their low immunogenicity which could be overcome by incorporating immunostimulatory adjuvants and nanoparticles such as Poly Lactic-co-Glycolic Acid (PLGA) or chitosan.

Development of an Enzyme-Mediated, Site-Specific Method to Conjugate Toll-Like Receptor 2 Agonists onto Protein Antigens: Toward a Broadly Protective, Four Component, Group A Streptococcal Self-Adjuvanting Lipoprotein-Fusion Combination Vaccine

Subunit vaccines composed of protein antigens covalently attached to Toll-like receptor (TLR) agonists elicit superior immune responses compared to mixtures of antigens and TLR agonists. Among different conjugation approaches, enzyme-mediated ligation is one of the few that provides an opportunity for the generation of homogeneous, molecularly defined products in which protein antigens are maintained with native structures, which is most critical to elicit protective immune responses upon vaccination. Four highly conserved protein antigens from Group A Streptococcus (GAS) have the potential to be safe and efficacious vaccine candidates. After a TLR2 agonist fibroblast-stimulating lipopeptide-1 (FSL-1) was successfully attached onto each antigen using sortase A and techniques for their purification were developed, a combination vaccine containing interleukin 8 (IL-8) protease (Streptococcus pyogenes cell envelope proteinase [SpyCEP]), Group A Streptococcal C5a peptidase (SCPA), anchorless virulence factor arginine deiminase (ADI), and trigger factor (TF)-TLR2 conjugates was produced. This combination was assessed for immunity in mice and compared with mixtures of the four antigens with FSL-1 or alum. High titer antigen-specific IgG antibodies were detected from all vaccine groups, with antibodies elicited from FSL-1 conjugates around 10-fold higher compared to the FSL-1 mixture group. Furthermore, the FSL-1 conjugates afforded a more balanced T_H1/T_H2 immune response than the alum-adjuvanted group, suggesting that this combination vaccine represents a promising candidate for the prevention of GAS diseases. Thus, we established a conjugation platform that allows for the production of defined, site-specific antigen-adjuvant conjugates, which maintain the native three-dimensional structure of antigens and can be potentially applied to a variety of protein antigens.

Advancements in prophylactic and therapeutic nanovaccines

Vaccines activate suitable immune responses to fight against diseases but can possess limitations such as compromised efficacy and immunogenic responses, poor stability, and requirement of adherence to multiple doses. ‘Nanovaccines’ have been explored to elicit a strong immune response with the advantages of nano-sized range, high antigen loading, enhanced immunogenicity, controlled antigen presentation, more retention in lymph nodes and promote patient compliance by a lower frequency of dosing. Various types of nanoparticles with diverse pathogenic or foreign antigens can help to overcome immunotolerance and alleviate the need of booster doses as required with conventional vaccines. Nanovaccines have the potential to induce both cell-mediated and antibody-mediated immunity and can render long-lasting immunogenic memory. With such properties, nanovaccines have shown high potential for the prevention of infectious diseases such as acquired immunodeficiency syndrome (AIDS), malaria, tuberculosis, influenza, and cancer. Their therapeutic potential has also been explored in the treatment of cancer. The various kinds of nanomaterials used for vaccine development and their effects on immune system activation have been discussed with special relevance to their implications in various pathological conditions.

Statement of Significance

Interaction of nanoparticles with the immune system has opened multiple avenues to combat a variety of infectious and non-infectious pathological conditions. Limitations of conventional vaccines have paved the path for nanomedicine associated benefits with a hope of producing effective nanovaccines. This review highlights the role of different types of nanovaccines and the role of nanoparticles in modulating the immune response of vaccines. The applications of nanovaccines in infectious and non-infectious diseases like malaria, tuberculosis, AIDS, influenza, and cancers have been discussed. It will help the readers develop an understanding of mechanisms of immune activation by nanovaccines and design appropriate strategies for novel nanovaccines.

Enhanced efficacy of a multi-epitope vaccine for type A and O foot‑and-mouth disease virus by fusing multiple epitopes with Mycobacterium tuberculosis heparin-binding hemagglutinin (HBHA), a novel TLR4 agonist

Foot-and-mouth disease (FMD) is an acute, severe, and highly contagious disease that affects cloven-hoofed animals and can lead to serious economic losses and social effects. Therefore, a safe and effective subunit vaccine is required to prevent and control FMD. Dendritic cells (DCs) are a type of professional antigen presenting cell (APC). Immature DCs are typically stimulated by various adjuvants via immune receptors (e.g., toll-like receptor 4 [TLR4]), which activate DCs to induce their maturation. TLR4 has been well-established to induce both innate and adaptive immune responses to various external microbial or internal damage-related molecular patterns. In this study, the multi-epitope immunogen, HAO, of foot-and-mouth disease virus (FMDV) serotypes A and O was fused with the recombinant protein, heparin-binding hemagglutinin (HBHA), a novel TLR4 agonist, to obtain a new recombinant fusion protein, termed HAO-HBHA. HAO-HBHA was found to be highly efficient at activating murine DCs by the TLR4 pathway, both in vitro and in vivo. HAO-HBHA elicited strong specific humoral immune responses detected with an ELISA and virus neutralizing antibody test (VNT). HAO-HBHA also elevated the cellular immune responses, as indicated by intracellular cytokine (e.g., IFN-γ, TNF-α, IL-4, IL-6, IL-10, and IL-12p70) expression in Th1 and Th2 cells. As a TLR4 agonist, HBHA has significant advantages for enhancing the immune efficacy of a FMDV serotype A and O bivalent multi-epitope vaccine. These findings provide a novel strategy for the development of a safe and effective multi-epitope vaccine candidate against FMDV and further extends the application of TLR agonist-based vaccine platforms.

Nanoparticle systems for cancer vaccine

As effective tools for public health, vaccines prevent disease by priming the body's adaptive and innate immune responses against an infection. Due to advances in understanding cancers and their relationship with the immune system, there is a growing interest in priming host immune defenses for a targeted and complete antitumor response. Nanoparticle systems have shown to be promising tools for effective antigen delivery as vaccines and/or for potentiating immune response as adjuvants. Here, we highlight relevant physiological processes involved in vaccine delivery, review recent advances in the use of nanoparticle systems for vaccines and discuss pertinent challenges to viably translate nanoparticle-based vaccines and adjuvants for public use.

Topological Aspects of the Design of Nanocarriers for Therapeutic Peptides and Proteins

Supramolecular chemistry holds great potential for the design of versatile and safe carriers for therapeutic proteins and peptides. Nanocarriers can be designed to meet specific criteria for given application (exact drug, administration route, target tissue, etc.). However, alterations in the topology of formulation components can drastically change their activity. This is why the supramolecular topology of therapeutic nanoconstructions has to be considered. Herein, we discuss several topological groups used for the design of nanoformulations for peptide and protein delivery: modification of polypeptide chains by host-guest interactions; packaging of proteins and peptides into liposomes; complexation and conjugation with dendrimers. Each topological type has its own advantages and disadvantages, so careful design of nanoformulations is needed. Ideally, each case where nanomedicine is needed requires a therapeutic construction specially created for that taking into account features of the administration route, target tissue, or organ, properties of a drug, its bioavailability, etc. The wide number of studies in the field of protein delivery by supramolecular and nanocarriers for proteins and peptides evidence their increasing potential for different aspects of the innovative medicine. Although significant progress has been achieved in the field, there are several remaining challenges to be overcome in future.

Application of built-in adjuvants for epitope-based vaccines

Several studies have shown that epitope vaccines exhibit substantial advantages over conventional vaccines. However, epitope vaccines are associated with limited immunity, which can be overcome by conjugating antigenic epitopes with built-in adjuvants (e.g., some carrier proteins or new biomaterials) with special properties, including immunologic specificity, good biosecurity and biocompatibility, and the ability to vastly improve the immune response of epitope vaccines. When designing epitope vaccines, the following types of built-in adjuvants are typically considered: (1) pattern recognition receptor ligands (i.e., toll-like receptors); (2) virus-like particle carrier platforms; (3) bacterial toxin proteins; and (4) novel potential delivery systems (e.g., self-assembled peptide nanoparticles, lipid core peptides, and polymeric or inorganic nanoparticles). This review primarily discusses the current and prospective applications of these built-in adjuvants (i.e., biological carriers) to provide some references for the future design of epitope-based vaccines.

Prospects on the Use of Schizochytrium sp. to Develop Oral Vaccines

Although oral subunit vaccines are highly relevant in the fight against widespread diseases, their high cost, safety and proper immunogenicity are attributes that have yet to be addressed in many cases and thus these limitations should be considered in the development of new oral vaccines. Prominent examples of new platforms proposed to address these limitations are plant cells and microalgae. Schizochytrium sp. constitutes an attractive expression host for vaccine production because of its high biosynthetic capacity, fast growth in low cost culture media, and the availability of processes for industrial scale production. In addition, whole Schizochytrium sp. cells may serve as delivery vectors; especially for oral vaccines since Schizochytrium sp. is safe for oral consumption, produces immunomodulatory compounds, and may provide bioencapsulation to the antigen, thus increasing its bioavailability. Remarkably, Schizochytrium sp. was recently used for the production of a highly immunoprotective influenza vaccine. Moreover, an efficient method for transient expression of antigens based on viral vectors and Schizochytrium sp. as host has been recently developed. In this review, the potential of Schizochytrium sp. in vaccinology is placed in perspective, with emphasis on its use as an attractive oral vaccination vehicle.

Bioconjugation Approaches to Producing Subunit Vaccines Composed of Protein or Peptide Antigens and Covalently Attached Toll-Like Receptor Ligands

Traditional vaccines derived from attenuated or inactivated pathogens are effective at inducing antibody-based protective immune responses but tend to be highly reactogenic, causing notable adverse effects. Vaccines with superior safety profiles can be produced by subunit approaches, utilizing molecularly defined antigens (e.g., proteins and polysaccharides). These antigens, however, often elicit poor immunological responses, necessitating the use of adjuvants. Immunostimulatory adjuvants have the capacity to activate antigen presenting cells directly through specific receptors (e.g., Toll-like receptors (TLRs)), resulting in enhanced presentation of antigens as well as the secretion of proinflammatory chemokines and cytokines. Consequently, innate immune responses are amplified and adaptive immunity is generated. Recently, site-specific conjugation of such immunostimulatory adjuvants (e.g., TLR ligands) onto defined antigens has shown superior efficacy over unconjugated mixtures, suggesting that the development of chemically characterized immunostimulatory adjuvants and optimized approaches for their conjugation with antigens may provide a better opportunity for the development of potent, novel vaccines. This review briefly summarizes various TLR agonists utilized as immunostimulatory adjuvants and focuses on the development of techniques (e.g., recombinant, synthetic, and semisynthetic) for generating adjuvant-antigen fusion vaccines incorporating peptide or protein antigens.