Virus-like Particle Vaccines and Platforms for Vaccine Development

Immunogenicity of novel vB_EcoS_NBD2 bacteriophage-originated nanotubes as a carrier for peptide-based vaccines

Non-infectious virus-like nanoparticles mimic native virus structures and can be modified by inserting foreign protein fragments, making them immunogenic tools for antigen presentation. This study investigated, for the first time, the immunogenicity of long and flexible polytubes formed by yeast-expressed tail tube protein gp39 of bacteriophage vB_EcoS_NBD2 and evaluated their ability to elicit an immune response against the inserted protein fragments. Protein gp39-based polytubes induced humoral immune response in mice, even without the use of adjuvant. Bioinformatics analysis guided the selection of protein fragments from Acinetobacter baumannii for insertion into the C-terminus of gp39. Chimeric polytubes, displaying 28-amino acid long OmpA protein fragment, induced IgG response against OmpA protein fragment in immunized mice. These polytubes demonstrated their effectiveness both as antigen carrier and an adjuvant, when the OmpA fragments were either displayed on chimeric polytubes or used alongside with the unmodified polytubes. Our findings expand the potential applications of long and flexible polytubes, contributing to the development of novel antigen carriers with improved immunogenicity and antigen presentation capabilities.

Tailored Viral-like Particles as Drivers of Medical Breakthroughs

Despite the recognized potential of nanoparticles, only a few formulations have progressed to clinical trials, and an even smaller number have been approved by the regulatory authorities and marketed. Virus-like particles (VLPs) have emerged as promising alternatives to conventional nanoparticles due to their safety, biocompatibility, immunogenicity, structural stability, scalability, and versatility. Furthermore, VLPs can be surface-functionalized with small molecules to improve circulation half-life and target specificity. Through the functionalization and coating of VLPs, it is possible to optimize the response properties to a given stimulus, such as heat, pH, an alternating magnetic field, or even enzymes. Surface functionalization can also modulate other properties, such as biocompatibility, stability, and specificity, deeming VLPs as potential vaccine candidates or delivery systems. This review aims to address the different types of surface functionalization of VLPs, highlighting the more recent cutting-edge technologies that have been explored for the design of tailored VLPs, their importance, and their consequent applicability in the medical field.

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.

Expression of VP2 protein of Novel goose parvovirus in baculovirus and evaluation of its immune effect

Short-beak and dwarfism syndrome (SBDS) is a new disease caused by a genetic variant of goose parvovirus in ducks that results in enormous economic losses for the waterfowl industry. Currently, there is no commercial vaccine for this disease, so it is urgent to develop a safer and more effective vaccine to prevent this disease. In this study, we optimized the production conditions to enhance the expression of the recombinant VP2 protein and identified the optimal conditions for subsequent large-scale expression. Furthermore, the protein underwent purification via nickel column affinity chromatography, followed by concentration using ultrafiltration tube. Subsequently, it was observed by transmission electron microscopy (TEM) that the NGPV recombinant VP2 protein assembled into virus-like particles (VLPs) resembling those of the original virus. Finally, the ISA 78-VG adjuvant was mixed with the NGPV-VP2 VLPs to be prepared as a subunit vaccine. Furthermore, both agar gel precipitation test (AGP) and serum neutralization test demonstrated that NGPV VLP subunit vaccine could induce the increase of NGPV antibody in breeding ducks. The ducklings were also challenged with the NGPV, and the results showed that the maternal antibody level could provide sufficient protection to the ducklings. These results indicated that the use of the NGPV VLP subunit vaccine based on the baculovirus expression system could facilitate the large-scale development of a reliable vaccine in the future.

Protein Nanoparticles as Vaccine Platforms for Human and Zoonotic Viruses

Vaccines are one of the most effective medical interventions, playing a pivotal role in treating infectious diseases. Although traditional vaccines comprise killed, inactivated, or live-attenuated pathogens that have resulted in protective immune responses, the negative consequences of their administration have been well appreciated. Modern vaccines have evolved to contain purified antigenic subunits, epitopes, or antigen-encoding mRNAs, rendering them relatively safe. However, reduced humoral and cellular responses pose major challenges to these subunit vaccines. Protein nanoparticle (PNP)-based vaccines have garnered substantial interest in recent years for their ability to present a repetitive array of antigens for improving immunogenicity and enhancing protective responses. Discovery and characterisation of naturally occurring PNPs from various living organisms such as bacteria, archaea, viruses, insects, and eukaryotes, as well as computationally designed structures and approaches to link antigens to the PNPs, have paved the way for unprecedented advances in the field of vaccine technology. In this review, we focus on some of the widely used naturally occurring and optimally designed PNPs for their suitability as promising vaccine platforms for displaying native-like antigens from human viral pathogens for protective immune responses. Such platforms hold great promise in combating emerging and re-emerging infectious viral diseases and enhancing vaccine efficacy and safety.

Knowledge on Human Papillomavirus Infections, Cancer Biology, Immune Interactions, Vaccination Coverage and Common Treatments: A Comprehensive Review

Human papillomavirus (HPV) is a circular, double-stranded DNA virus and recognized as the most prevalent sexually transmitted infectious agent worldwide. The HPV life cycle encompasses three primary stages. First, the virus infiltrates the basal cells of the stratified epidermis. Second, there is a low-level expression of viral genes and preservation of the viral genome in the basal layer. Lastly, productive replication of HPV occurs in differentiated cells. An effective immune response, involving various immune cells, including innate immunity, keratinocytes, dendritic cells, and natural killer T cells, is instrumental in clearing HPV infection and thwarting the development of HPV-associated tumors. Vaccines have demonstrated their efficacy in preventing genital warts, high-grade precancerous lesions, and cancers in females. In males, the vaccines can also aid in preventing genital warts, anal precancerous lesions, and cancer. This comprehensive review aims to provide a thorough and detailed exploration of HPV infections, delving into its genetic characteristics, life cycle, pathogenesis, and the role of high-risk and low-risk HPV strains. In addition, this review seeks to elucidate the intricate immune interactions that govern HPV infections, spanning from innate immunity to adaptive immune responses, as well as examining the evasion mechanisms used by the virus. Furthermore, the article discusses the current landscape of HPV vaccines and common treatments, contributing to a holistic understanding of HPV and its associated diseases.

The Potential of Plant-Produced Virus-like Particle Vaccines for African Horse Sickness and Other Equine Orbiviruses

African horse sickness is a devastating viral disease of equids. It is transmitted by biting midges of the genus Culicoides with mortalities reaching over 90% in naïve horses. It is endemic to sub-Saharan Africa and is seasonally endemic in many parts of southern Africa. However, outbreaks in Europe and Asia have occurred that caused significant economic issues. There are attenuated vaccines available for control of the virus but concerns regarding the safety and efficacy means that alternatives are sought. One promising alternative is the use of virus-like particles in vaccine preparations, which have the potential to be safer and more efficacious as vaccines against African horse sickness. These particles are best made in a complex, eukaryotic system, but due to technical challenges, this may cause significant economic strain on the developing countries most affected by the disease. Therefore, this review also summarises the success so far, and potential, of recombinant protein expression in plants to reduce the economic strain of production.

Vaccine adjuvants: current status, research and development, licensing, and future opportunities

Vaccines represent one of the most significant inventions in human history and have revolutionized global health. Generally, a vaccine functions by triggering the innate immune response and stimulating antigen-presenting cells, leading to a defensive adaptive immune response against a specific pathogen's antigen. As a key element, adjuvants are chemical materials often employed as additives to increase a vaccine's efficacy and immunogenicity. For over 90 years, adjuvants have been essential components in many human vaccines, improving their efficacy by enhancing, modulating, and prolonging the immune response. Here, we provide a timely and comprehensive review of the historical development and the current status of adjuvants, covering their classification, mechanisms of action, and roles in different vaccines. Additionally, we perform systematic analysis of the current licensing processes and highlights notable examples from clinical trials involving vaccine adjuvants. Looking ahead, we anticipate future trends in the field, including the development of new adjuvant formulations, the creation of innovative adjuvants, and their integration into the broader scope of systems vaccinology and vaccine delivery. The article posits that a deeper understanding of biochemistry, materials science, and vaccine immunology is crucial for advancing vaccine technology. Such advancements are expected to lead to the future development of more effective vaccines, capable of combating emerging infectious diseases and enhancing public health.

Enhancing Protective Antibodies against Opioids through Antigen Display on Virus-like Particles

Opioid use disorder (OUD) has become a public health crisis, with recent significant increases in the number of deaths due to overdose. Vaccination can provide an attractive complementary strategy to combat OUD. A key for high vaccine efficacy is the induction of high levels of antibodies specific to the drug of abuse. Herein, a powerful immunogenic carrier, virus-like particle mutant bacteriophage Qβ (mQβ), has been investigated as a carrier of a small molecule hapten 6-AmHap mimicking heroin. The mQβ-6-AmHap conjugate was able to induce significantly higher levels of IgG antibodies against 6-AmHap than mice immunized with the corresponding tetanus toxoid-6-AmHap conjugate in head-to-head comparison studies in multiple strains of mice. The IgG antibody responses were persistent with high anti-6-AmHap titers 600 days after being immunized with mQβ-6-AmHap. The antibodies induced exhibited strong binding toward multiple heroin/morphine derivatives that have the potential to be abused, while binding weakly to medications used for OUD treatment and pain relief. Furthermore, vaccination effectively reduced the impacts of morphine on mice in both ambulation and antinociception assays, highlighting the translational potential of the mQβ-6-AmHap conjugate to mitigate the harmful effects of drugs of abuse.

The quest for nanoparticle-powered vaccines in cancer immunotherapy

Despite recent advancements in cancer treatment, this disease still poses a serious threat to public health. Vaccines play an important role in preventing illness by preparing the body's adaptive and innate immune responses to combat diseases. As our understanding of malignancies and their connection to the immune system improves, there has been a growing interest in priming the immune system to fight malignancies more effectively and comprehensively. One promising approach involves utilizing nanoparticle systems for antigen delivery, which has been shown to potentiate immune responses as vaccines and/or adjuvants. In this review, we comprehensively summarized the immunological mechanisms of cancer vaccines while focusing specifically on the recent applications of various types of nanoparticles in the field of cancer immunotherapy. By exploring these recent breakthroughs, we hope to identify significant challenges and obstacles in making nanoparticle-based vaccines and adjuvants feasible for clinical application. This review serves to assess recent breakthroughs in nanoparticle-based cancer vaccinations and shed light on their prospects and potential barriers. By doing so, we aim to inspire future immunotherapies for cancer that harness the potential of nanotechnology to deliver more effective and targeted treatments.

Bacteriophage Virus-Like Particles: Platforms for Vaccine Design

Virus-like particles (VLPs) derived from bacteriophages have many applications in biomedical sciences, especially in the development of candidate vaccines against viral and bacterial infections. Bacteriophage VLPs can be manufactured cheaply and in large quantities in bacteria compared to eukaryotic expression systems. In addition to this, bacteriophage VLPs are excellent platforms for vaccine design for the following reason: Humans do not have preexisting antibodies against bacteriophage VLPs. Thus, antigens displayed on bacteriophage VLP platforms are expected to be highly immunogenic. As such, VLPs derived from MS2, PP7, Qβ, AP205, P22 bacteriophages, etc. have been used to develop candidate vaccines against human infectious and noninfectious agents. This mini-review summarizes data from some of the candidate bacteriophage-based VLP peptide vaccines that have been developed. The review also highlights some strategies used to develop the candidate bacteriophage-based VLP peptide vaccines.

Development of a Tag/Catcher-mediated capsid virus-like particle vaccine presenting the conserved Neisseria gonorrhoeae SliC antigen that blocks human lysozyme

Virus-like particles (VLPs) are promising nanotools for the development of subunit vaccines due to high immunogenicity and safety. Herein, we explored the versatile and effective Tag/Catcher-AP205 capsid VLP (cVLP) vaccine platform to address the urgent need for the development of an effective and safe vaccine against gonorrhea. The benefits of this clinically validated cVLP platform include its ability to facilitate unidirectional, high-density display of complex/full-length antigens through an effective split-protein Tag/Catcher conjugation system. To assess this modular approach for making cVLP vaccines, we used a conserved surface lipoprotein, SliC, that contributes to the Neisseria gonorrhoeae defense against human lysozyme, as a model antigen. This protein was genetically fused at the N- or C-terminus to the small peptide Tag enabling their conjugation to AP205 cVLP, displaying the complementary Catcher. We determined that SliC with the N-terminal SpyTag, N-SliC, retained lysozyme-blocking activity and could be displayed at high density on cVLPs without causing aggregation. In mice, the N-SliC-VLP vaccines, adjuvanted with AddaVax or CpG, induced significantly higher antibody titers compared to controls. In contrast, similar vaccine formulations containing monomeric SliC were non-immunogenic. Accordingly, sera from N-SliC-VLP-immunized mice also had significantly higher human complement-dependent serum bactericidal activity. Furthermore, the N-SliC-VLP vaccines administered subcutaneously with an intranasal boost elicited systemic and vaginal IgG and IgA, whereas subcutaneous delivery alone failed to induce vaginal IgA. The N-SliC-VLP with CpG (10 µg/dose) induced the most significant increase in total serum IgG and IgG3 titers, vaginal IgG and IgA, and bactericidal antibodies.

Challenges and Opportunities in the Process Development of Chimeric Vaccines

Vaccines are integral to human life to protect them from life-threatening diseases. However, conventional vaccines often suffer limitations like inefficiency, safety concerns, unavailability for non-culturable microbes, and genetic variability among pathogens. Chimeric vaccines combine multiple antigen-encoding genes of similar or different microbial strains to protect against hyper-evolving drug-resistant pathogens. The outbreaks of dreadful diseases have led researchers to develop economical chimeric vaccines that can cater to a large population in a shorter time. The process development begins with computationally aided omics-based approaches to design chimeric vaccines. Furthermore, developing these vaccines requires optimizing upstream and downstream processes for mass production at an industrial scale. Owing to the complex structures and complicated bioprocessing of evolving pathogens, various high-throughput process technologies have come up with added advantages. Recent advancements in high-throughput tools, process analytical technology (PAT), quality-by-design (QbD), design of experiments (DoE), modeling and simulations, single-use technology, and integrated continuous bioprocessing have made scalable production more convenient and economical. The paradigm shift to innovative strategies requires significant attention to deal with major health threats at the global scale. This review outlines the challenges and emerging avenues in the bioprocess development of chimeric vaccines.

Virus-Like Particles Based on the Novel Goose Parvovirus (NGPV) VP2 Protein Protect Ducks against NGPV Challenge

Novel goose parvovirus (NGPV), a genetic variant of goose parvovirus, has been spreading throughout China since 2015 and mainly infects ducklings with the symptoms of growth retardation, beak atrophy, and protruding tongue, leading to huge economic losses every year. A safe and effective vaccine is urgently needed to control NGPV infection. In this study, virus-like particles (VLPs) of NPGV were assembled and evaluated for their immunogenicity. The VP2 protein of NGPV was expressed in Spodoptera frugiperda insect cells using baculovirus as vector. The VP2 protein was efficiently expressed in the nucleus of insect cells, and the particles with a circular or hexagonal shape and a diameter of approximately 30 nm, similar to the NGPV virion, were observed using transmission electron microscopy (TEM). The purified particles were confirmed to be composed of VP2 using western blot and TEM, indicating that the VLPs of NGPV were successfully assembled. Furthermore, the immunogenicity of the VLPs of NGPV was evaluated in Cherry Valley ducks. The level of NGPV serum antibodies increased significantly at 1-4 weeks post-immunization. No clinical symptoms or deaths of ducks occurred in all groups after being challenged with NGPV at 4 weeks post-immunization. There was no viral shedding in the immunized group. However, viral shedding was detected at 3-7 days post-challenge in the non-immunized group. Moreover, VLPs can protect ducks from histopathological lesions caused by NGPV and significantly reduce viral load in tissue at 5 days post-challenge. Based on these findings, NGPV VLPs are promising candidates for vaccines against NGPV.

mRNA and Adenoviral Vector Vaccine Platforms Utilized in COVID-19 Vaccines: Technologies, Ecosystem, and Future Directions

New technological platforms, such as mRNA and adenoviral vector vaccines, have been utilized to develop coronavirus disease 2019 (COVID-19) vaccines. These new modalities enable rapid and flexible vaccine design and cost-effective and swift manufacturing, effectively combating pandemics caused by mutating viruses. Innovation ecosystems, including universities, startups, investors, and governments are crucial for developing these cutting-edge technologies. This review summarizes the research and development trajectory of these vaccine technologies, their investments, and the support surrounding them, in addition to the technological details of each technology. In addition, this study examines the importance of an innovation ecosystem in developing novel technologies, comparing it with the case of Japan, which has lagged behind in COVID-19 vaccine development. It also explores the direction of vaccine development in the post-COVID-19 era.

Stereoselective Synthesis of Sialyl Lewisa Antigen and the Effective Anticancer Activity of Its Bacteriophage Qβ Conjugate as an Anticancer Vaccine

Sialyl Lewisa (sLea ), also known as cancer antigen 19-9 (CA19-9), is a tumor-associated carbohydrate antigen. The overexpression of sLea on the surface of a variety of cancer cells makes it an attractive target for anticancer immunotherapy. However, sLea -based anticancer vaccines have been under-explored. To develop a new vaccine, efficient stereoselective synthesis of sLea with an amine-bearing linker was achieved, which was subsequently conjugated with a powerful carrier bacteriophage, Qβ. Mouse immunization with the Qβ-sLea conjugate generated strong and long-lasting anti-sLea IgG antibody responses, which were superior to those induced by the corresponding conjugate of sLea with the benchmark carrier keyhole limpet hemocyanin. Antibodies elicited by Qβ-sLea were highly selective toward the sLea structure, could bind strongly with sLea -expressing cancer cells and human pancreatic cancer tissues, and kill tumor cells through complement-mediated cytotoxicity. Furthermore, vaccination with Qβ-sLea significantly reduced tumor development in a metastatic cancer model in mice, demonstrating tumor protection for the first time by a sLea -based vaccine, thus highlighting the significant potential of sLea as a promising cancer antigen.

Stereoselective Synthesis of Sialyl Lewisa Antigen and the Effective Anticancer Activity of Its Bacteriophage Qβ Conjugate as an Anticancer Vaccine

Sialyl Lewisa (sLea ), also known as cancer antigen 19-9 (CA19-9), is a tumor-associated carbohydrate antigen. The overexpression of sLea on the surface of a variety of cancer cells makes it an attractive target for anticancer immunotherapy. However, sLea -based anticancer vaccines have been under-explored. To develop a new vaccine, efficient stereoselective synthesis of sLea with an amine-bearing linker was achieved, which was subsequently conjugated with a powerful carrier bacteriophage, Qβ. Mouse immunization with the Qβ-sLea conjugate generated strong and long-lasting anti-sLea IgG antibody responses, which were superior to those induced by the corresponding conjugate of sLea with the benchmark carrier keyhole limpet hemocyanin. Antibodies elicited by Qβ-sLea were highly selective toward the sLea structure, could bind strongly with sLea -expressing cancer cells and human pancreatic cancer tissues, and kill tumor cells through complement-mediated cytotoxicity. Furthermore, vaccination with Qβ-sLea significantly reduced tumor development in a metastatic cancer model in mice, demonstrating tumor protection for the first time by a sLea -based vaccine, thus highlighting the significant potential of sLea as a promising cancer antigen.

Next-Generation TB Vaccines: Progress, Challenges, and Prospects

Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), is a prevalent global infectious disease and a leading cause of mortality worldwide. Currently, the only available vaccine for TB prevention is Bacillus Calmette-Guérin (BCG). However, BCG demonstrates limited efficacy, particularly in adults. Efforts to develop effective TB vaccines have been ongoing for nearly a century. In this review, we have examined the current obstacles in TB vaccine research and emphasized the significance of understanding the interaction mechanism between MTB and hosts in order to provide new avenues for research and establish a solid foundation for the development of novel vaccines. We have also assessed various TB vaccine candidates, including inactivated vaccines, attenuated live vaccines, subunit vaccines, viral vector vaccines, DNA vaccines, and the emerging mRNA vaccines as well as virus-like particle (VLP)-based vaccines, which are currently in preclinical stages or clinical trials. Furthermore, we have discussed the challenges and opportunities associated with developing different types of TB vaccines and outlined future directions for TB vaccine research, aiming to expedite the development of effective vaccines. This comprehensive review offers a summary of the progress made in the field of novel TB vaccines.