Generation of a tumor vaccine candidate based on conjugation of a MUC1 peptide to polyionic papillomavirus virus-like particles

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.

Identifying Key Drivers of Efficient B Cell Responses: On the Role of T Help, Antigen-Organization, and Toll-like Receptor Stimulation for Generating a Neutralizing Anti-Dengue Virus Response

T help (Th), stimulation of toll-like receptors (pathogen-associated molecular patterns, PAMPs), and antigen organization and repetitiveness (pathogen-associated structural patterns, PASPs) were shown numerous times to be important in driving B-cell and antibody responses. In this study, we dissected the individual contributions of these parameters using newly developed "Immune-tag" technology. As model antigens, we used eGFP and the third domain of the dengue virus 1 envelope protein (DV1 EDIII), the major target of virus-neutralizing antibodies. The respective proteins were expressed alone or genetically fused to the N-terminal fragment of the cucumber mosaic virus (CMV) capsid protein-nCMV, rendering the antigens oligomeric. In a step-by-step manner, RNA was attached as a PAMP, and/or a universal Th-cell epitope was genetically added for additional Th. Finally, a PASP was added to the constructs by displaying the antigens highly organized and repetitively on the surface of CMV-derived virus-like particles (CuMV VLPs). Sera from immunized mice demonstrated that each component contributed stepwise to the immunogenicity of both proteins. All components combined in the CuMV VLP platform induced by far the highest antibody responses. In addition, the DV1 EDIII induced high levels of DENV-1-neutralizing antibodies only if displayed on VLPs. Thus, combining multiple cues typically associated with viruses results in optimal antibody responses.

Study of self-assembling properties of HBc-VLP derivatives aided by molecular dynamic simulations from a thermodynamic perspective

Self-assembling protein nanoparticles showed promise for vaccine design due to efficient antigen presentations and safety. However, the unpredictable formations of epitopes-fused protein assemblies remain challenging in the upstream design. This study suggests employing molecular dynamic (MD) simulations to investigate the assembly properties of Hepatitis B core protein (HBc) from thermodynamic perspectives. Eight HBc derivatives were expressed in E. coli, with their self-assembly properties characterised by high-performance liquid chromatography and transmission electron microscopy. MD simulations on the dimers, based on AlphaFold-predicted 3D structures, analysed the derivative at the atomic level. Results revealed that HBc derivatives can form dissociative polymers or large multi-subunit structures due to assembly failures. The instability of the dimer in aqueous solvents or inappropriate intradimer distances could cause major assembly failures. Polar solvation energies played a vital role too in forming assemble-incompetent dimers. Importantly, our study demonstrated that MD simulations on dimers can provide preliminary predictions on the assembly properties of HBc derivatives, thus aiding vaccine design by lowering the risk of self-assembling failures in engineered proteins.Communicated by Ramaswamy H. Sarma.

Virus-like Particle (VLP) Vaccines for Cancer Immunotherapy

Cancer vaccines are increasingly being studied as a possible strategy to prevent and treat cancers. While several prophylactic vaccines for virus-caused cancers are approved and efficiently used worldwide, the development of therapeutic cancer vaccines needs to be further implemented. Virus-like particles (VLPs) are self-assembled protein structures that mimic native viruses or bacteriophages but lack the replicative material. VLP platforms are designed to display single or multiple antigens with a high-density pattern, which can trigger both cellular and humoral responses. The aim of this review is to provide a comprehensive overview of preventive VLP-based vaccines currently approved worldwide against HBV and HPV infections or under evaluation to prevent virus-caused cancers. Furthermore, preclinical and early clinical data on prophylactic and therapeutic VLP-based cancer vaccines were summarized with a focus on HER-2-positive breast cancer.

Bioengineered Bovine Papillomavirus L1 Protein Virus-like Particle (VLP) Vaccines for Enhanced Induction of CD8 T Cell Responses through Cross-Priming

Safe and effective T cell vaccines are needed for the treatment or prevention of cancers as well as infectious agents where vaccines for neutralizing antibodies have performed poorly. Recent research highlights an important role for tissue-resident memory T cells (T_RM cells) in protective immunity and the role of a subset of dendritic cells that are capable of cross-priming for the induction of T_RM cells. However, efficient vaccine technologies that operate through cross-priming and induce robust CD8+ T cell responses are lacking. We developed a platform technology by genetically engineering the bovine papillomavirus L1 major capsid protein to insert a polyglutamic acid/cysteine motif in place of wild-type amino acids in the HI loop. Virus-like particles (VLPs) are formed by self-assembly in insect cells infected with a recombinant baculovirus. Polyarginine/cysteine-tagged antigens are linked to the VLP by a reversible disulfide bond. The VLP possesses self-adjuvanting properties due to the immunostimulatory activity of papillomavirus VLPs. Polyionic VLP vaccines induce robust CD8+ T cell responses in peripheral blood and tumor tissues. A prostate cancer polyionic VLP vaccine was more efficacious than other vaccines and immunotherapies for the treatment of prostate cancer in a physiologically relevant murine model and successfully treated more advanced diseases than the less efficacious technologies. The immunogenicity of polyionic VLP vaccines is dependent on particle size, reversible linkage of the antigen to the VLP, and an interferon type 1 and Toll-like receptor (TLR)3/7-dependent mechanism.

Chimeric virus-like particles presenting tumour-associated MUC1 epitope result in high titers of specific IgG antibodies in the presence of squalene oil-in-water adjuvant: towards safe cancer immunotherapy

Background

Immunotherapy is emerging as a powerful treatment approach for several types of cancers. Modulating the immune system to specifically target cancer cells while sparing healthy cells, is a very promising approach for safer therapies and increased survival of cancer patients. Tumour-associated antigens are favorable targets for cancer immunotherapy, as they are exclusively expressed by the cancer cells, minimizing the risk of an autoimmune reaction. The ability to initiate the activation of the immune system can be achieved by virus-like particles (VLPs) which are safe and potent delivery tools. VLP‐based vaccines have evolved dramatically over the last few decades and showed great potential in preventing infectious diseases. Immunogenic potency of engineered VLPs as a platform for the development of effective therapeutic cancer vaccines has been studied extensively. This study involves recombinant VLPs presenting multiple copies of tumour-specific mucin 1 (MUC1) epitope as a potentially powerful tool for future immunotherapy.

Results

In this report VLPs based on the structural protein of Norovirus (NoV VP1) were genetically modified to present multiple copies of tumour-specific MUC1 epitope on their surface. Chimeric MUC1 particles were produced in the eukaryotic Leishmania tarentolae expression system and used in combination with squalene oil-in-water emulsion MF59 adjuvant to immunize BALB/c mice. Sera from vaccinated mice demonstrated high titers of IgG and IgM antibodies which were specifically recognizing MUC1 antigen.

Conclusions

The obtained results show that immunization with recombinant chimeric NoV VP1- MUC1 VLPs result in high titers of MUC1 specific IgG antibodies and show great therapeutic potential as a platform to present tumour-associated antigens.

Graphical Abstract

Conjugation of Native-Like HIV-1 Envelope Trimers onto Liposomes Using EDC/Sulfo-NHS Chemistry: Requirements and Limitations

The display of native-like human immunodeficiency virus type 1 envelope (HIV-1 Env) trimers on liposomes has gained wide attention over the last few years. Currently, available methods have enabled the preparation of Env-liposome conjugates of unprecedented quality. However, these protocols require the Env trimer to be tagged and/or to carry a specific functional group. For this reason, we have investigated N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide/N-Hydroxysulfosuccinimide (EDC/Sulfo-NHS) chemistry for its potential to covalently conjugate tag-free, non-functionalized native-like Env trimers onto the surface of carboxyl-functionalized liposomes. The preservation of the liposome's physical integrity and the immunogen's conformation required a fine-tuned two-step approach based on the controlled use of β-mercaptoethanol. The display of Env trimers was strictly limited to activated liposomes of positive charge, i.e., liposomes with a positive zeta potential that carry amine-reactive Sulfo-NHS esters on their surface. In agreement with that, conjugation was found to be highly ionic strength- and pH-dependent. Overall, we have identified electrostatic pre-concentration (i.e., close proximity between negatively charged Env trimers and positively charged liposomes established through electrostatic attraction) to be crucial for conjugation reactions to proceed. The present study highlights the requirements and limitations of potentially scalable EDC/Sulfo-NHS-based approaches and represents a solid basis for further research into the controlled conjugation of tag-free, non-functionalized native-like Env trimers on the surface of liposomes, and other nanoparticles.

Chemical Strategies to Boost Cancer Vaccines

Personalized cancer vaccines (PCVs) are reinvigorating vaccine strategies in cancer immunotherapy. In contrast to adoptive T-cell therapy and checkpoint blockade, the PCV strategy modulates the innate and adaptive immune systems with broader activation to redeploy antitumor immunity with individualized tumor-specific antigens (neoantigens). Following a sequential scheme of tumor biopsy, mutation analysis, and epitope prediction, the administration of neoantigens with synthetic long peptide (SLP) or mRNA formulations dramatically improves the population and activity of antigen-specific CD4+ and CD8+ T cells. Despite the promising prospect of PCVs, there is still great potential for optimizing prevaccination procedures and vaccine potency. In particular, the arduous development of tumor-associated antigen (TAA)-based vaccines provides valuable experience and rational principles for augmenting vaccine potency which is expected to advance PCV through the design of adjuvants, delivery systems, and immunosuppressive tumor microenvironment (TME) reversion since current personalized vaccination simply admixes antigens with adjuvants. Considering the broader application of TAA-based vaccine design, these two strategies complement each other and can lead to both personalized and universal therapeutic methods. Chemical strategies provide vast opportunities for (1) exploring novel adjuvants, including synthetic molecules and materials with optimizable activity, (2) constructing efficient and precise delivery systems to avoid systemic diffusion, improve biosafety, target secondary lymphoid organs, and enhance antigen presentation, and (3) combining bioengineering methods to innovate improvements in conventional vaccination, "smartly" re-educate the TME, and modulate antitumor immunity. As chemical strategies have proven versatility, reliability, and universality in the design of T cell- and B cell-based antitumor vaccines, the union of such numerous chemical methods in vaccine construction is expected to provide new vigor and vitality in cancer treatment.

Immunogenicity Assessment of Rift Valley Fever Virus Virus-Like Particles in BALB/c Mice

Rift Valley fever (RVF) is an acute, febrile zoonotic disease that is caused by the RVF virus (RVFV) and is spread by arthropod vectors. Virus-like particle (VLP) vaccines, which have the advantages of strong immunogenicity and safety, play an important role in the prevention of this disease. VLPs for RVFV were successfully prepared by our research group using a baculovirus-insect cell expression system. To study the immunogenicity of these RVFV VLPs, a correct 3rd or 4th generation recombinant baculovirus, rBac-N-G, was identified and used to infect Sf9 cells, which were cultured in suspension at a large scale. Subsequently, cell debris was removed by centrifugation, and the VLPs were concentrated by ultracentrifugation and purified using a sucrose gradient, after which they were used to immunize BALB/c mice by intramuscular injection. The results showed that the RVFV VLPs prepared by our research group could effectively induce mice to produce RVFV neutralizing antibodies and that the prepared VLPs could stimulate mouse spleen cells to produce high levels of the cytokines IL-4 and IFN-γ. Moreover, the proportion of lymphocytes producing IL-4 and IFN-γ in the spleen of mice immunized with RVFV VLPs was significantly increased. Therefore, the RVFV VLPs prepared in this study had strong immunogenicity and could effectively activate humoral and cellular immunity in mice. This study lays a solid foundation for the development of RVFV VLP vaccine candidates and promotes the healthy development of animal husbandry and human public health.

Use of plant viruses and virus-like particles for the creation of novel vaccines

In recent decades, the development of plant virology and genetic engineering techniques has resulted in the construction of plant virus-based vaccines for protection against different infectious agents, cancers and autoimmune diseases in both humans and animals. Interaction studies between plant viruses and mammalian organisms have suggested that plant viruses and virus-like particles (VLPs) are safe and noninfectious to humans and animals. Plant viruses with introduced antigens are powerful vaccine components due to their strongly organized, repetitive spatial structure; they can elicit strong immune responses similar to those observed with infectious mammalian viruses. The analysis of published data demonstrated that at least 73 experimental vaccines, including 61 prophylactic and 12 therapeutic vaccines, have been constructed using plant viruses as a carrier structure for presentation of different antigens. This information clearly demonstrates that noninfectious viruses are also applicable as vaccine carriers. Moreover, several plant viruses have been used for platform development, and corresponding vaccines are currently being tested in human and veterinary clinical trials. This review therefore discusses the main principles of plant VLP vaccine construction, emphasizing the physical, chemical, genetic and immunological aspects. Results of the latest studies suggest that several plant virus-based vaccines will join the list of approved human and animal vaccines in the near future.

Plant Viruses in Plant Molecular Pharming: Toward the Use of Enveloped Viruses

Plant molecular pharming has emerged as a reliable platform for recombinant protein expression providing a safe and low-cost alternative to bacterial and mammalian cells-based systems. Simultaneously, plant viruses have evolved from pathogens to molecular tools for recombinant protein expression, chimaeric viral vaccine production, and lately, as nanoagents for drug delivery. This review summarizes the genesis of viral vectors and agroinfection, the development of non-enveloped viruses for various biotechnological applications, and the on-going research on enveloped plant viruses.

The 5th virus-like particle and nano-particle vaccines (VLPNPV) conference

Virus-like particles (VLPs) and nano-particles (NPs) are promising vaccine platforms that have led to the successful development of commercially available vaccines. The 5th international virus-like particle and nano-particle vaccines conference was held in Bern, Switzerland, from the 25th to the 27th of September in 2018. Topics included novel vaccine production techniques, methods to enhance vaccine immunogenicity, and preclinical/clinical efficacy evaluation of vaccine candidates. Here, we report on a selection of updates that were presented including the production of vaccines in plants, novel adjuvants to enhance vaccine immunogenicity, novel techniques of conjugating vaccine platforms with target antigens and the use of VLP-based vaccines for cancer and inflammatory diseases.

New Routes and Opportunities for Modular Construction of Particulate Vaccines: Stick, Click, and Glue

Vaccines based on virus-like particles (VLPs) can induce potent B cell responses. Some non-chimeric VLP-based vaccines are highly successful licensed products (e.g., hepatitis B surface antigen VLPs as a hepatitis B virus vaccine). Chimeric VLPs are designed to take advantage of the VLP framework by decorating the VLP with a different antigen. Despite decades of effort, there have been few licensed chimeric VLP vaccines. Classic approaches to create chimeric VLPs are either genetic fusion or chemical conjugation, using cross-linkers from lysine on the VLP to cysteine on the antigen. We describe the principles that make these classic approaches challenging, in particular for complex, full-length antigens bearing multiple post-translational modifications. We then review recent advances in conjugation approaches for protein-based non-enveloped VLPs or nanoparticles, to overcome such challenges. This includes the use of strong non-covalent assembly methods (stick), unnatural amino acids for bio-orthogonal chemistry (click), and spontaneous isopeptide bond formation by SpyTag/SpyCatcher (glue). Existing applications of these methods are outlined and we critically consider the key practical issues, with particular insight on Tag/Catcher plug-and-display decoration. Finally, we highlight the potential for modular particle decoration to accelerate vaccine generation and prepare for pandemic threats in human and veterinary realms.

Protein Complexes and Virus-Like Particle Technology

Virus-like particle (VLP) technologies are based on virus-inspired artificial structures and the intrinsic ability of viral proteins to self-assemble at controlled conditions. Therefore, the basic knowledge about the mechanisms of viral particle formation is highly important for designing of industrial applications. As an alternative to genetic and chemical processes, different physical methods are frequently used for VLP construction, including well characterized protein complexes for introduction of foreign molecules in VLP structures.This chapter shortly discusses the mechanisms how the viruses form their perfectly ordered structures as well as the principles and most interesting application examples, how to exploit the structural and assembly/disassembly properties of viral structures for creation of new nanomaterials.

The dawn of vaccines for cancer prevention

An important role of the immune system is in the surveillance for abnormal or transformed cells, which is known as cancer immunosurveillance. Through this process, the first changes to normal tissue homeostasis caused by infectious or other inflammatory insults can be detected by the immune system through the recognition of antigenic molecules (including tumour antigens) expressed by abnormal cells. However, as they develop, tumour cells can acquire antigenic and other changes that allow them to escape elimination by the immune system. To bias this process towards elimination, immunosurveillance can be improved by the administration of vaccines based on tumour antigens. Therapeutic cancer vaccines have been extensively tested in patients with advanced cancer but have had little clinical success, which has been attributed to the immunosuppressive tumour microenvironment. Thus, the administration of preventive vaccines at pre-malignant stages of the disease holds promise, as they function before tumour-associated immune suppression is established. Accordingly, immunological and clinical studies are yielding impressive results.

Nanoparticles: augmenting tumor antigen presentation for vaccine and immunotherapy treatments of cancer

The major goal of immunity is maintaining host survival. Toward this, immune cells recognize and eliminate targets that pose a danger. Primarily, these are external invaders (pathogens) and internal invaders (cancers). Their recognition relies on distinguishing foreign components (antigens) from self-antigens. Since cancer cells are the host's own cells that are harmfully altered, they are difficult to distinguish from normal self. Furthermore, the antigens least resembling the host are often sequestered in parts of the tumor least accessible to immune responses. Therefore, to sufficiently boost immunity, these tumor antigens must be exposed to the immune system. Toward this, nanoparticles provide an innovating means of tumor antigen presentation and are destined to become an integral part of cancer immunotherapy.

A novel immunization approach for dengue infection based on conserved T cell epitopes formulated in calcium phosphate nanoparticles

Dengue virus (DV) is the etiologic agent of dengue fever, the most significant mosquito-borne viral disease in humans. Most DV vaccine approaches are focused on generating antibody mediated responses; one such DV vaccine is approved for use in humans but its efficacy is limited. While it is clear that T cell responses play important role in DV infection and subsequent disease manifestations, fewer studies are aimed at developing vaccines that induce robust T cells responses. Potent T cell based vaccines require 2 critical components: the identification of specific T cell stimulating MHC associated peptides, and an optimized vaccine delivery vehicle capable of simultaneously delivering the antigens and any required adjuvants. We have previously identified and characterized DV specific HLA-A2 and -A24 binding DV serotypes conserved epitopes, and the feasibility of an epitope based vaccine for DV infection. In this study, we build on those previous studies and describe an investigational DV vaccine using T cell epitopes incorporated into a calcium phosphate nanoparticle (CaPNP) delivery system. This study presents a comprehensive analysis of functional immunogenicity of DV CaPNP/multipeptide formulations in vitro and in vivo and demonstrates the CaPNP/multipeptide vaccine is capable of inducing T cell responses against all 4 serotypes of DV. This synthetic vaccine is also cost effective, straightforward to manufacture, and stable at room temperature in a lyophilized form. This formulation may serve as an effective candidate DV vaccine that protects against all 4 serotypes as either a prophylactic or therapeutic vaccine.

Virus-based nanoparticles as platform technologies for modern vaccines

Nanoscale engineering is revolutionizing the development of vaccines and immunotherapies. Viruses have played a key role in this field because they can function as prefabricated nanoscaffolds with unique properties that are easy to modify. Viruses are immunogenic via multiple pathways, and antigens displayed naturally or by engineering on the surface can be used to create vaccines against the cognate virus, other pathogens, specific molecules or cellular targets such as tumors. This review focuses on the development of virus-based nanoparticle systems as vaccines indicated for the prevention or treatment of infectious diseases, chronic diseases, cancer, and addiction. WIREs Nanomed Nanobiotechnol 2016, 8:554-578. doi: 10.1002/wnan.1383 For further resources related to this article, please visit the WIREs website.

A Modular Vaccine Development Platform Based on Sortase-Mediated Site-Specific Tagging of Antigens onto Virus-Like Particles

Virus-like particles (VLPs) can be used as powerful nanoscale weapons to fight against virus infection. In addition to direct use as vaccines, VLPs have been extensively exploited as platforms on which to display foreign antigens for prophylactic vaccination and immunotherapeutic treatment. Unfortunately, fabrication of new chimeric VLP vaccines in a versatile, site-specific and highly efficient manner is beyond the capability of traditional VLP vaccine design approaches, genetic insertion and chemical conjugation. In this study, we described a greatly improved VLP display strategy by chemoenzymatic site-specific tailoring antigens on VLPs surface with high efficiency. Through the transpeptidation mediated by sortase A, one protein and two epitopes containing N-terminal oligoglycine were conjugated to the LPET motif on the surface of hepatitis B virus core protein (HBc) VLPs with high density. All of the new chimeric VLPs induced strong specific IgG responses. Furthermore, the chimeric VLPs with sortase A tagged enterovirus 71 (EV71) SP70 epitope could elicit effective antibodies against EV71 lethal challenging as well as the genetic insertion chimeric VLPs. The sortase A mediated chemoenzymatic site-specific tailoring of the HBc VLP approach shows great potential in new VLP vaccine design for its simplicity, site specificity, high efficiency, and versatility.

Different applications of virus-like particles in biology and medicine: Vaccination and delivery systems

Virus-like particles (VLPs) mimic the whole construct of virus particles devoid of viral genome as used in subunit vaccine design. VLPs can elicit efficient protective immunity as direct immunogens compared to soluble antigens co-administered with adjuvants in several booster injections. Up to now, several prokaryotic and eukaryotic systems such as insect, yeast, plant, and E. coli were used to express recombinant proteins, especially for VLP production. Recent studies are also generating VLPs in plants using different transient expression vectors for edible vaccines. VLPs and viral particles have been applied for different functions such as gene therapy, vaccination, nanotechnology, and diagnostics. Herein, we describe VLP production in different systems as well as its applications in biology and medicine.

Central nervous system-specific consequences of simian immunodeficiency virus Gag escape from major histocompatibility complex class I-mediated control

In the fourth decade of the HIV epidemic, the relationship between host immunity and HIV central nervous system (CNS) disease remains incompletely understood. Using a simian immunodeficiency virus (SIV)/macaque model, we examined CNS outcomes in pigtailed macaques expressing the MHC class I allele Mane-A1*084:01 which confers resistance to SIV-induced CNS disease and induces the prototypic viral escape mutation Gag K165R. Insertion of gag K165R into the neurovirulent clone SIV/17E-Fr reduced viral replication in vitro compared to SIV/17E-Fr. We also found lower cerebrospinal fluid (CSF), but not plasma, viral loads in macaques inoculated with SIV/17E-Fr K165R versus those inoculated with wildtype. Although escape mutation K165R was genotypically stable in plasma, it rapidly reverted to wildtype Gag KP9 in both CSF and in microglia cultures. We induced robust Gag KP9-specific CTL tetramer responses by vaccinating Mane-A*084:01-positive pigtailed macaques with a Gag KP9 virus-like particle (VLP) vaccine. Upon SIV/17E-Fr challenge, vaccinated animals had lower SIV RNA in CSF compared to unvaccinated controls, but showed no difference in plasma viral loads. These data clearly demonstrate that viral fitness in the CNS is distinct from the periphery and underscores the necessity of understanding the consequences of viral escape in CNS disease with the advent of new therapeutic vaccination strategies.

Nanoengineered strategies to optimize dendritic cells for gastrointestinal tumor immunotherapy: from biology to translational medicine

Nanomedicine may play an important role in improving the clinical efficacy of dendritic cell-based immunotherapy against GI tract malignancies. Dendritic cell-based vaccines have proven their effectiveness against different established GI tract tumors, yet their success is mainly hindered by the strong tumor-induced suppressive microenvironment. The sustained and targeted release of tumor antigens to dendritic cells using different nanoengineered approaches would be an efficient strategy to overcome established immune tolerance. Encapsulation would result in low diffusivity, restricted movement, effective crosspresentation and enhanced T-cell responses. These nanotherapy-based approaches will certainly help with the designing of clinically translatable dendritic cell-based therapeutic vaccines and facilitate the selective removal of residual disease in gastrointestinal cancer patients following standard treatments.

Physicochemical and immunological assessment of engineered pure protein particles with different redox states

The development of subunit antigen delivery formulations has become an important research endeavor, especially in cases where a whole cell vaccine approach has significant biosafety issues. Particle-based systems have shown particular efficacy due to their inherent immunogenicity. In some cases, fabrication techniques can lead to changes in the redox states of encapsulated protein antigens. By employing a uniform, well-characterized, single-protein system, it is possible to elucidate how the molecular details of particle-based protein antigens affect their induced immune responses. Using mesoporous silica-templated, amide bond-stabilized ovalbumin particles, three types of particles were fabricated from native, reduced, and oxidized ovalbumin, resulting in particles with different physicochemical properties and immunogenicity. Phagocytosis, transcription factor activation, and cytokine secretion by a mouse macrophage cell line did not reveal significant differences between the three types of particles. Oxidation of the ovalbumin, however, was shown to inhibit the intracellular degradation of the particles compared with native and reduced ovalbumin particles. Slow intracellular degradation of the oxidized particles was correlated with inefficient antigen presentation and insignificant levels of T cell priming and antibody production in vivo. In contrast, particles fabricated from native and reduced ovalbumin were rapidly degraded after internalization by macrophages in vitro and resulted in significant T cell and B cell immune responses in vivo. Taken together, the current study demonstrates how the redox state of a protein antigen significantly impacts the immunogenicity of the particulate vaccine formulations.

Non-carrier nanoparticles adjuvant modular protein vaccine in a particle-dependent manner

Nanoparticles are increasingly used to adjuvant vaccine formulations due to their biocompatibility, ease of manufacture and the opportunity to tailor their size, shape, and physicochemical properties. The efficacy of similarly-sized silica (Si-OH), poly (D,L-lactic-co-glycolic acid) (PLGA) and poly caprolactone (PCL) nanoparticles (nps) to adjuvant recombinant capsomere presenting antigenic M2e modular peptide from Influenza A virus (CapM2e) was investigated in vivo. Formulation of CapM2e with Si-OH or PLGA nps significantly boosted the immunogenicity of modular capsomeres, even though CapM2e was not actively attached to the nanoparticles prior to injection (i.e., formulation was by simple mixing). In contrast, PCL nps showed no significant adjuvant effect using this simple-mixing approach. The immune response induced by CapM2e alone or formulated with nps was antibody-biased with very high antigen-specific antibody titer and less than 20 cells per million splenocytes secreting interferon gamma. Modification of silica nanoparticle surface properties through amine functionalization and pegylation did not lead to significant changes in immune response. This study confirms that simple mixing-based formulation can lead to effective adjuvanting of antigenic protein, though with antibody titer dependent on nanoparticle physicochemical properties.

Vaccines and Vaccination

Livestock vaccines aim to increase livestock product and improve the health and welfare of livestock animals in a cost-efficient manner and prevent disease transmission. Successful livestock vaccines have been generated for pathogens including bacterial, viral, protozoan, and multicellular pathogens. These livestock vaccines have a significant effect on animal health and products and on human health through growing safe food procurement and preventing zoonotic diseases. There are successful production of biotechnological-based animal vaccines licensed for use that include virus-like particle vaccines, gene-deleted marker vaccines, subunit vaccines, DIVA vaccines, and DNA vaccines.

Cancer immunotherapy: nanodelivery approaches for immune cell targeting and tracking

Cancer is one of the most common diseases afflicting people globally. New therapeutic approaches are needed due to the complexity of cancer as a disease. Many current treatments are very toxic and have modest efficacy at best. Increased understanding of tumor biology and immunology has allowed the development of specific immunotherapies with minimal toxicity. It is important to highlight the performance of monoclonal antibodies, immune adjuvants, vaccines and cell-based treatments. Although these approaches have shown varying degrees of clinical efficacy, they illustrate the potential to develop new strategies. Targeted immunotherapy is being explored to overcome the heterogeneity of malignant cells and the immune suppression induced by both the tumor and its microenvironment. Nanodelivery strategies seek to minimize systemic exposure to target therapy to malignant tissue and cells. Intracellular penetration has been examined through the use of functionalized particulates. These nano-particulate associated medicines are being developed for use in imaging, diagnostics and cancer targeting. Although nano-particulates are inherently complex medicines, the ability to confer, at least in principle, different types of functionality allows for the plausible consideration these nanodelivery strategies can be exploited for use as combination medicines. The development of targeted nanodelivery systems in which therapeutic and imaging agents are merged into a single platform is an attractive strategy. Currently, several nanoplatform-based formulations, such as polymeric nanoparticles, micelles, liposomes and dendrimers are in preclinical and clinical stages of development. Herein, nanodelivery strategies presently investigated for cancer immunotherapy, cancer targeting mechanisms and nanocarrier functionalization methods will be described. We also intend to discuss the emerging nano-based approaches suitable to be used as imaging techniques and as cancer treatment options.

MUC1 and maltose‑binding protein recombinant fusion protein combined with Bacillus Calmette‑Guerin induces MUC1‑specific and nonspecific anti‑tumor immunity in mice

Human mucin 1 (MUC1) is a target for immunotherapy. The major problem associated with MUC1‑based cancer vaccines is the weakness of the immunogenicity of MUC1. The present study aimed to develop an efficient cancer vaccine through generating a recombinant fusion protein consisting of MUC1 and maltose‑binding protein (MBP) by inserting seven tandem repeats encoding the human MUC1 gene into the pMAL‑c2 expression vector. Bacillus Calmette‑Guerin (BCG) was used as an adjuvant. MUC1 was found to predominantly induce T helper type 2 (Th2) cell responses. MUC1/BCG and MUC1‑MBP were found to generate T helper (Th) type 1 and 2 responses, while MUC1‑MBP/BCG induced a Th1 immune profile and stimulated MUC1‑specific cytotoxic T lymphocyte killing activity. MUC1‑MBP, as well as MBP and BCG alone were found to induce natural killer (NK) cell activity, with MUC1‑MBP/BCG observed to synergistically induce NK cell activity. Furthermore, MUC1‑MBP/BCG significantly inhibited MUC1+ B16 cell growth in mice. These findings show that MBP augments the immunogenicity of MUC1 and that BCG enhances the efficacy of the MUC1‑MBP vaccine. Thus, MUC1‑MBP/BCG may have potential as a cancer vaccine for clinical application.

Therapeutic cancer vaccines

Therapeutic cancer vaccines have the potential of being integrated in the therapy of numerous cancer types and stages. The wide spectrum of vaccine platforms and vaccine targets is reviewed along with the potential for development of vaccines to target cancer cell "stemness," the epithelial-to-mesenchymal transition (EMT) phenotype, and drug-resistant populations. Preclinical and recent clinical studies are now revealing how vaccines can optimally be used with other immune-based therapies such as checkpoint inhibitors, and so-called nonimmune-based therapeutics, radiation, hormonal therapy, and certain small molecule targeted therapies; it is now being revealed that many of these traditional therapies can lyse tumor cells in a manner as to further potentiate the host immune response, alter the phenotype of nonlysed tumor cells to render them more susceptible to T-cell lysis, and/or shift the balance of effector:regulatory cells in a manner to enhance vaccine efficacy. The importance of the tumor microenvironment, the appropriate patient population, and clinical trial endpoints is also discussed in the context of optimizing patient benefit from vaccine-mediated therapy.

Bioengineering virus-like particles as vaccines

Virus-like particle (VLP) technology seeks to harness the optimally tuned immunostimulatory properties of natural viruses while omitting the infectious trait. VLPs that assemble from a single protein have been shown to be safe and highly efficacious in humans, and highly profitable. VLPs emerging from basic research possess varying levels of complexity and comprise single or multiple proteins, with or without a lipid membrane. Complex VLP assembly is traditionally orchestrated within cells using black-box approaches, which are appropriate when knowledge and control over assembly are limited. Recovery challenges including those of adherent and intracellular contaminants must then be addressed. Recent commercial VLPs variously incorporate steps that include VLP in vitro assembly to address these problems robustly, but at the expense of process complexity. Increasing research activity and translation opportunity necessitate bioengineering advances and new bioprocessing modalities for efficient and cost-effective production of VLPs. Emerging approaches are necessarily multi-scale and multi-disciplinary, encompassing diverse fields from computational design of molecules to new macro-scale purification materials. In this review, we highlight historical and emerging VLP vaccine approaches. We overview approaches that seek to specifically engineer a desirable immune response through modular VLP design, and those that seek to improve bioprocess efficiency through inhibition of intracellular assembly to allow optimal use of existing purification technologies prior to cell-free VLP assembly. Greater understanding of VLP assembly and increased interdisciplinary activity will see enormous progress in VLP technology over the coming decade, driven by clear translational opportunity.

Recent progress in adjuvant discovery for peptide-based subunit vaccines

Peptide-based subunit vaccines are of great interest in modern immunotherapy as they are safe, easy to produce and well defined. However, peptide antigens produce a relatively weak immune response, and thus require the use of immunostimulants (adjuvants) for optimal efficacy. Developing a safe and effective adjuvant remains a challenge for peptide-based vaccine design. Recent advances in immunology have allowed researchers to have a better understanding of the immunological implication of related diseases, which facilitates more rational design of adjuvant systems. Understanding the molecular structure of the adjuvants allows the establishment of their structure-activity relationships which is useful for the development of next-generation adjuvants. This review summarizes the current state of adjuvants development in the field of synthetic peptide-based vaccines. The structural, chemical and biological properties of adjuvants associated with their immunomodulatory effects are discussed.

Chimeric SV40 virus-like particles induce specific cytotoxicity and protective immunity against influenza A virus without the need of adjuvants

Virus-like particles (VLPs) are a promising vaccine platform due to the safety and efficiency. However, it is still unclear whether polyomavirus-based VLPs are useful for this purpose. Here, we attempted to evaluate the potential of polyomavirus VLPs for the antiviral vaccine using simian virus 40 (SV40). We constructed chimeric SV40-VLPs carrying an HLA-A*02:01-restricted, cytotoxic T lymphocyte (CTL) epitope derived from influenza A virus. HLA-A*02:01-transgenic mice were then immunized with the chimeric SV40-VLPs. The chimeric SV40-VLPs effectively induced influenza-specific CTLs and heterosubtypic protection against influenza A viruses without the need of adjuvants. Because DNase I treatment of the chimeric SV40-VLPs did not disrupt CTL induction, the intrinsic adjuvant property may not result from DNA contaminants in the VLP preparation. In addition, immunization with the chimeric SV40-VLPs generated long-lasting memory CTLs. We here propose that the chimeric SV40-VLPs harboring an epitope may be a promising CTL-based vaccine platform with self-adjuvant properties.

VLPs and particle strategies for cancer vaccines

Effective delivery of tumor antigens to APCs is one of the key steps for eliciting a strong and durable immune response to tumors. Several cancer vaccines have been evaluated in clinical trials, based on soluble peptides, but results have not been fully satisfactory. To improve immunogenicity particles provide a valid strategy to display and/or incorporate epitopes which can be efficiently targeted to APCs for effective induction of adaptive immunity. In the present review, we report some leading technologies for developing particulate vaccines employed in cancer immunotherapy, highlighting the key parameters for a rational design to elicit both humoral and cellular responses.

Bovine papillomavirus: opening new trends for comparative pathology

For many years, research on bovine papillomavirus (BPV) has contributed to the understanding of papillomavirus-induced pathology in humans and animals. The present review shows how recent studies on BPV keep providing evidence concerning key points in viral infection, such as the expression of viral proteins in lymphocytes and the occurrence of productive infections of the placenta. Studies on BPV-induced tumours also provide important information concerning the mechanisms of oncogenesis and immune evasion, as in the cases of connexin 43 down-regulation with loss of intercellular gap junctions and Toll-like receptor 4 (TLR4) down-regulation in equine sarcoids. The biological functions of viral proteins are also being further clarified, as in the case of E2, which was recently shown to load BPV genomes into host chromosomes during the S phase, a process mediated by the ChlR1 protein. In the near future, the ongoing efforts to characterize and classify additional emerging BPV types are likely to broaden even further the possibilities for research.

Immune system targeting by biodegradable nanoparticles for cancer vaccines

The concept of therapeutic cancer vaccines is based on the activation of the immune system against tumor cells after the presentation of tumor antigens. Nanoparticles (NPs) have shown great potential as delivery systems for cancer vaccines as they potentiate the co-delivery of tumor-associated antigens and adjuvants to dendritic cells (DCs), insuring effective activation of the immune system against tumor cells. In this review, the immunological mechanisms behind cancer vaccines, including the role of DCs in the stimulation of T lymphocytes and the use of Toll-like receptor (TLR) ligands as adjuvants will be discussed. An overview of each of the three essential components of a therapeutic cancer vaccine - antigen, adjuvant and delivery system - will be provided with special emphasis on the potential of particulate delivery systems for cancer vaccines, in particular those made of biodegradable aliphatic polyesters, such as poly(lactic-co-glycolic acid) (PLGA) and poly-ε-caprolactone (PCL). Some of the factors that can influence NP uptake by DCs, including size, surface charge, surface functionalization and route of administration, will also be considered.

Expression of human papillomavirus 6b L1 protein in silkworm larvae and enhanced green fluorescent protein displaying on its virus-like particles

Human papillomavirus (HPV) 6b L1 capsid protein was expressed using the Bombyx mori nucleopolyhedrovirus (BmNPV) bacmid expression system in silkworm larvae. Two constructs, full-length L1 (500 a.a) and C-terminal-deleted short L1 (479 a.a), and three PCR-manipulated antigenic loops at amino acids 55–56, 174–175, and 348–349 regions were incorporated with whole enhanced green fluorescent protein (EGFP). Expressed in full, short L1 proteins and variants were purified in heparin affinity column chromatography and confirmed by SDS-PAGE and western blot. The presence of self-assembled virus-like particles (VLPs) and EGFP incorporation on the surface of VLPs were confirmed by the observation of transmission electron and immunoelectron microscopies, respectively. HPV 6b L1 major capsid protein was successfully expressed in silkworm, and effective manipulation on the antigenic regions showed the path to versatile vaccine development based on HPV L1-VLPs.

Adenovirus-vectored type Asia1 foot-and-mouth disease virus (FMDV) capsid proteins as a vehicle to display a conserved, neutralising epitope of type O FMDV

The objective of this study was to explore the immunogenicity of an adenovirus construction expressing a type O foot and mouth disease virus neutralising epitope (8E8) in the context of heterologous capsid proteins. Adenoviruses expressing four chimeric type Asia1 FMDV capsid proteins were constructed by inserting the type O FMDV 8E8 epitope into the G-H loop from the type Asia1 VP1 at amino acid residues 139/140, 150/151, 134/140 or at both 139/140 and 150/151. These recombinant proteins were recognised by antibodies against the type O 8E8 epitope and type Asia1 FMDV. When inoculated in mice, all of the recombinant chimeric capsid proteins for each single epitope insertion induced the production of anti-type O FMDV neutralising antibodies. The recombinant chimeric capsid proteins with a foreign insertion at position 139/140 or 150/151 induced high levels of anti-type Asia1 FMDV neutralising antibodies as the recombinant type Asia1 capsid proteins without any foreign epitope, suggesting that the foreign insertion did not affect the immunogenicity of the type Asia1 FMDV capsid proteins. This study suggests that a foreign epitope displayed on the surface of the FMDV capsid proteins could induce an epitope-specific response. Therefore, the adenovirus-vectored FMDV capsid proteins could be used as a vehicle for the development of an epitope-based vaccine.

Therapeutic cancer vaccines: current status and moving forward

Concurrent with U.S. Food and Drug Administration (FDA) approval of the first therapeutic cancer vaccine, a wide spectrum of other cancer vaccine platforms that target a diverse range of tumor-associated antigens is currently being evaluated in randomized phase II and phase III trials. The profound influence of the tumor microenvironment and other immunosuppressive entities, however, can limit the effectiveness of these vaccines. Numerous strategies are currently being evaluated both preclinically and clinically to counteract these immunosuppressive entities, including the combined use of vaccines with immune checkpoint inhibitors, certain chemotherapeutics, small-molecule targeted therapies, and radiation. The potential influence of the appropriate patient population and clinical trial endpoint in vaccine therapy studies is discussed, as well as the potential importance of biomarkers in future directions of this field.

Potential targets for pancreatic cancer immunotherapeutics

Pancreatic adenocarcinoma is the fourth leading cause of cancer death with an overall 5-year survival of less than 5%. As there is ample evidence that pancreatic adenocarcinomas elicit antitumor immune responses, identification of pancreatic cancer-associated antigens has spurred the development of vaccination-based strategies for treatment. While promising results have been observed in animal tumor models, most clinical studies have found only limited success. As most trials were performed in patients with advanced pancreatic cancer, the contribution of immune suppressor mechanisms should be taken into account. In this article, we detail recent work in tumor antigen vaccination and the recently identified mechanisms of immune suppression in pancreatic cancer. We offer our perspective on how to increase the clinical efficacy of vaccines for pancreatic cancer.

An overview on the field of micro- and nanotechnologies for synthetic Peptide-based vaccines

The development of synthetic peptide-based vaccines has many advantages in comparison with vaccines based on live attenuated organisms, inactivated or killed organism, or toxins. Peptide-based vaccines cannot revert to a virulent form, allow a better conservation, and are produced more easily and safely. However, they generate a weaker immune response than other vaccines, and the inclusion of adjuvants and/or the use of vaccine delivery systems is almost always needed. Among vaccine delivery systems, micro- and nanoparticulated ones are attractive, because their particulate nature can increase cross-presentation of the peptide. In addition, they can be passively or actively targeted to antigen presenting cells. Furthermore, particulate adjuvants are able to directly activate innate immune system in vivo. Here, we summarize micro- and nanoparticulated vaccine delivery systems used in the field of synthetic peptide-based vaccines as well as strategies to increase their immunogenicity.

Applications of viral nanoparticles in medicine

Several nanoparticle platforms are currently being developed for applications in medicine, including both synthetic materials and naturally occurring bionanomaterials such as viral nanoparticles (VNPs) and their genome-free counterparts, virus-like particles (VLPs). A broad range of genetic and chemical engineering methods have been established that allow VNP/VLP formulations to carry large payloads of imaging reagents or drugs. Furthermore, targeted VNPs and VLPs can be generated by including peptide ligands on the particle surface. In this article, we highlight state-of-the-art virus engineering principles and discuss recent advances that bring potential biomedical applications a step closer. Viral nanotechnology has now come of age and it will not be long before these formulations assume a prominent role in the clinic.