H5N1 virus-like particle vaccine elicits cross-reactive neutralizing antibodies that preferentially bind to the oligomeric form of influenza virus hemagglutinin in humans

SARS-CoV-2 spike-based virus-like particles incorporate influenza H1/N1 antigens and induce dual immunity in mice

A vaccine effective against both SARS-CoV-2 and influenza A (IAV) viruses could represent a cost-effective strategy to reduce their combined public health burden as well as potential complications arising from co-infection. Based on previous findings that full-length SARS-CoV-2 spike (S) expression can induce high-level, enveloped VLP (eVLP) production in CHO cells, we tested whether IAV H1N1 hemagglutinin (H1) and neuraminidase (N1) could also be displayed on these particles. We found that co-incorporation of the IAV surface antigens in spike VLPs (S-VLPs) was highly efficient: upon transient co-expression of S + H1 or S + H1 + N1 in CHO cells, the resulting VLPs contained similar amounts of the SARS-CoV-2 S and IAV antigens. The self-assembled bivalent (S/H1) and trivalent (S/H1/N1) VLPs released into the culture media were purified by single-step chromatography using a S-VLP affinity resin. Western blot analysis and immuno‑gold labeling transmission electron microscopy (TEM) of purified VLPs confirmed the coexistence of S, H1 and N1 antigens in the same particles. Finally, we demonstrated that two doses of adjuvanted bivalent and trivalent VLPs elicit specific functional antibodies and cellular immunity in a mouse model, suggesting potential for combined SARS-CoV-2/IAV vaccine development.

Phage display technology and its impact in the discovery of novel protein-based drugs

INTRODUCTION

Phage display technology is a well-established versatile in vitro display technology that has been used for over 35 years to identify peptides and antibodies for use as reagents and therapeutics, as well as exploring the diversity of alternative scaffolds as another option to conventional therapeutic antibody discovery. Such successes have been responsible for spawning a range of biotechnology companies, as well as many complementary technologies devised to expedite the drug discovery process and resolve bottlenecks in the discovery workflow.

AREAS COVERED

In this perspective, the authors summarize the application of phage display for drug discovery and provide examples of protein-based drugs that have either been approved or are being developed in the clinic. The amenability of phage display to generate functional protein molecules to challenging targets and recent developments of strategies and techniques designed to harness the power of sampling diverse repertoires are highlighted.

EXPERT OPINION

Phage display is now routinely combined with cutting-edge technologies to deep-mine antibody-based repertoires, peptide, or alternative scaffold libraries generating a wealth of data that can be leveraged, e.g. via artificial intelligence, to enable the potential for clinical success in the discovery and development of protein-based therapeutics.

Cross-protection against influenza viruses by chimeric M2e-H3 stalk protein or multi-subtype neuraminidase plus M2e virus-like particle vaccine in ferrets

Current influenza vaccine is not effective in providing cross-protection against variants. We evaluated the immunogenicity and efficacy of multi-subtype neuraminidase (NA) and M2 ectodomain virus-like particle (m-cNA-M2e VLP) and chimeric M2e-H3 stalk protein vaccines (M2e-H3 stalk) in ferrets. Our results showed that ferrets with recombinant m-cNA-M2e VLP or M2e-H3 stalk vaccination induced multi-vaccine antigen specific IgG antibodies (M2e, H3 stalk, NA), NA inhibition, antibody-secreting cells, and IFN-γ secreting cell responses. Ferrets immunized with either m-cNA-M2e VLP or M2e-H3 stalk vaccine were protected from H1N1 and H3N2 influenza viruses by lowering viral titers in nasal washes, trachea, and lungs after challenge. Vaccinated ferret antisera conferred broad humoral immunity in naïve mice. Our findings provide evidence that immunity to M2e and HA-stalk or M2e plus multi-subtype NA proteins induces cross-protection in ferrets.

Epitopes and Mimotopes Identification Using Phage Display for Vaccine Development against Infectious Pathogens

Traditional vaccines use inactivated or weakened forms of pathogens which could have side effects and inadequate immune responses. To overcome these challenges, phage display has emerged as a valuable tool for identifying specific epitopes that could be used in vaccines. This review emphasizes the direct connection between epitope identification and vaccine development, filling a crucial gap in the field. This technique allows vaccines to be engineered to effectively stimulate the immune system by presenting carefully selected epitopes. Phage display involves screening libraries of random peptides or gene/genome fragments using serum samples from infected, convalescent, or vaccinated individuals. This method has been used to identify epitopes from various pathogens including SARS-CoV-2, Mycobacterium tuberculosis, hepatitis viruses, H5N1, HIV-1, Human T-lymphotropic virus 1, Plasmodium falciparum, Trypanosoma cruzi, and Dirofilaria repens. Bacteriophages offer advantages such as being immunogenic carriers, low production costs, and customization options, making them a promising alternative to traditional vaccines. The purpose of this study has been to highlight an approach that encompasses the entire process from epitope identification to vaccine production using a single technique, without requiring additional manipulation. Unlike conventional methods, phage display demonstrates exceptional efficiency and speed, which could provide significant advantages in critical scenarios such as pandemics.

Respiratory Viruses and Virus-like Particle Vaccine Development: How Far Have We Advanced?

With technological advancements enabling globalization, the intercontinental transmission of pathogens has become much easier. Respiratory viruses are one such group of pathogens that require constant monitoring since their outbreak leads to massive public health crises, as exemplified by the influenza virus, respiratory syncytial virus (RSV), and the recent coronavirus disease 2019 (COVID-19) outbreak caused by the SARS-CoV-2. To prevent the transmission of these highly contagious viruses, developing prophylactic tools, such as vaccines, is of considerable interest to the scientific community. Virus-like particles (VLPs) are highly sought after as vaccine platforms for their safety and immunogenicity profiles. Although several VLP-based vaccines against hepatitis B and human papillomavirus have been approved for clinical use by the United States Food and Drug Administration, VLP vaccines against the three aforementioned respiratory viruses are lacking. Here, we summarize the most recent progress in pre-clinical and clinical VLP vaccine development. We also outline various strategies that contributed to improving the efficacy of vaccines against each virus and briefly discuss the stability aspect of VLPs that makes it a highly desired vaccine platform.

Evaluation of Virus-Free Manufacture of Recombinant Proteins Using CRISPR-Mediated Gene Disruption in Baculovirus-Infected Insect Cells

The manufacture and downstream processing of virus-like particles (VLPs) using the baculovirus expression vector system (BEVS) is complicated by the presence of large concentrations of baculovirus particles, which are similar in size and density to VLPs, and consequently are difficult to separate. To reduce the burden of downstream processing, CRISPR-Cas9 technology was used to introduce insertion-deletion (indel) mutations within the Autographa californica multiple nucleopolyhedrovirus (AcMNPV) gp64 open reading frame, which encodes the major envelope protein of AcMNPV. After comfirming the site-specific targeting of gp64 leading to reduced budded virus (BV) release, the gag gene of human immunodeficiency virus type 1 was expressed to produce Gag VLPs. This approach was effective for producing VLPs using the BEVS whilst simultaneously obstructing BV release.

Universal protection against influenza viruses by multi-subtype neuraminidase and M2 ectodomain virus-like particle

Annual influenza vaccination is recommended to update the variable hemagglutinin antigens. Here, we first designed a virus-like particle (VLP) displaying consensus multi-neuraminidase (NA) subtypes (cN1, cN2, B cNA) and M2 ectodomain (M2e) tandem repeat (m-cNA-M2e VLP). Vaccination of mice with m-cNA-M2e VLP induced broad NA inhibition (NAI), and M2e antibodies as well as interferon-gamma secreting T cell responses. Mice vaccinated with m-cNA-M2e VLP were protected against influenza A (H1N1, H5N1, H3N2, H9N2, H7N9) and influenza B (Yamagata and Victoria lineage) viruses containing substantial antigenic variations. Protective immune contributors include cellular and humoral immunity as well as antibody-dependent cellular cytotoxicity. Furthermore, comparable cross protection by m-cNA-M2e VLP vaccination was induced in aged mice. This study supports a novel strategy of developing a universal vaccine against influenza A and B viruses potentially in both young and aged populations by inducing multi-NA subtype and M2e immunity with a single VLP entity.

Characterization of Immune Response towards Generation of Universal Anti-HA-Stalk Antibodies after Immunization of Broiler Hens with Triple H5N1/NA-HA-M1 VLPs

(1) Background: Avian influenza viruses (AIVs) promptly evade preexisting immunity by constantly altering the immunodominant neutralizing antibody epitopes (antigenic drift) or by procuring new envelope serotypes (antigenic shift). As a consequence, the majority of antibodies elicited by infection or vaccination protect only against closely related strains. The immunodominance of the globular head of the main glycoprotein has been shown to mask the immunogenicity of the conserved regions located within the hemagglutinin (HA) protein. It has been shown that the broadly neutralizing universal antibodies recognize the HA2 domain in headless hemagglutinin (HA-stalk). Therefore, the HA-stalk is a highly conserved antigen, which makes it a good candidate to be used in universal vaccine development against AIVs. (2) Methods: Sf9 insect cells were used to produce triple H5N1/NA-HA-M1 influenza virus-like particles (VLPs) via co-expression of neuraminidase, hemagglutinin and matrix proteins from a tricistronic expression cassette. Purified influenza VLPs were used to immunize broiler hens. An in-depth characterization of the immune response was performed with an emphasis on the pool of elicited universal antibodies. (3) Results: Our findings suggest, that after vaccination with triple H5N1/NA-HA-M1 VLPs, hens generate a pool of broad-spectrum universal anti-HA-stalk antibodies. Furthermore, these universal antibodies are able to recognize the mammalian-derived HA-stalk recombinant proteins from homologous H5N1 and heterologous H7N9 AIVs as well as from the heterosubtypic human H1N1 influenza strain. (4) Conclusions: Our findings may suggest that highly pathogenic avian influenza H5 HA protein contain functional epitopes that are attractive targets for the generation of broad-spectrum antibodies against AIVs in their native hosts.

Protective immunity induced by oral vaccination with a recombinant Lactococcus lactis vaccine against H5Nx in chickens

BACKGROUND

The development of an influenza vaccine for poultry that provides broadly protective immunity against influenza H5Nx viruses is a challenging goal.

RESULTS

Lactococcus lactis (L. lactis)/pNZ8149-HA1-M2 expressing hemagglutinin-1 (HA1) of A/chicken/Vietnam/NCVD-15A59/2015 (H5N6) and the conserved M2 gene of A/Vietnam/1203/2004 (H5N1) was generated. L. lactis/pNZ8149-HA1-M2 could induce significant humoral, mucosal and cell-mediated immune responses, as well as neutralization antibodies. Importantly, L. lactis/pNZ8149-HA1-M2 could prevent disease symptoms without significant weight loss and confer protective immunity in a chicken model against lethal challenge with divergent influenza H5Nx viruses, including H5N6 and H5N1.

CONCLUSIONS

L. lactis/pNZ8149-HA1-M2 can serve as a promising vaccine candidate in poultry industry for providing protection against H5Nx virus infection in the field application.

Minimal Dosage of Porcine Circovirus Type 2d Based Virus-like Particles to Induce Stable Protective Immunity against Infection

In recent years, porcine circovirus type 2d (PCV2d) has achieved a dominant position worldwide. Various PCV2d capsid-based vaccines have been used to alleviate concerns regarding the emergence of the variant. This study aimed to determine the dosage of recombinant PCV2d capsid protein to induce protective efficacy against experimental challenge with a virulent PCV2d strain. Conventional 3-week-old pigs were intramuscularly inoculated with different doses of the protein (60, 20, 10 and 2 µg). Four weeks after vaccination, all pigs were challenged with pathogenic PCV2d (SNU140003), which was isolated from a farm severely experiencing PCV2-associated disease in Korea. Vaccination with greater than 10 µg of the capsid protein caused a significant (p < 0.05) reduction in PCV2d viremia, lymphoid lesions and lymphoid PCV2 antigen levels in vaccinated challenged pigs compared to unvaccinated challenged pigs. The vaccination also resulted in significantly higher (p < 0.05) titers of neutralizing antibodies against PCV2d. However, the pigs vaccinated with 2 µg had significantly lower neutralizing antibody titers than the other vaccinated groups. They showed a similar level of challenged PCV2d in serum and lymphoid lesion score compared to unvaccinated challenged pigs. The difference in efficacy among the vaccinated groups indicates that there may be a baseline dosage to induce sufficient neutralizing antibodies to prevent viral replication in pigs. In conclusion, at least 10 µg dosage of capsid protein is essential for stable protective efficacy against PCV2d in a pig model.

Solutions against emerging infectious and noninfectious human diseases through the application of baculovirus technologies

Abstract

Baculoviruses are insect pathogens widely used as biotechnological tools in different fields of life sciences and technologies. The particular biology of these entities (biosafety viruses 1; large circular double-stranded DNA genomes, infective per se; generally of narrow host range on insect larvae; many of the latter being pests in agriculture) and the availability of molecular-biology procedures (e.g., genetic engineering to edit their genomes) and cellular resources (availability of cell lines that grow under in vitro culture conditions) have enabled the application of baculoviruses as active ingredients in pest control, as systems for the expression of recombinant proteins (Baculovirus Expression Vector Systems—BEVS) and as viral vectors for gene delivery in mammals or to display antigenic proteins (Baculoviruses applied on mammals—BacMam). Accordingly, BEVS and BacMam technologies have been introduced in academia because of their availability as commercial systems and ease of use and have also reached the human pharmaceutical industry, as incomparable tools in the development of biological products such as diagnostic kits, vaccines, protein therapies, and—though still in the conceptual stage involving animal models—gene therapies. Among all the baculovirus species, the Autographa californica multiple nucleopolyhedrovirus has been the most highly exploited in the above utilities for the human-biotechnology field. This review highlights the main achievements (in their different stages of development) of the use of BEVS and BacMam technologies for the generation of products for infectious and noninfectious human diseases.

Key points

• Baculoviruses can assist as biotechnological tools in human health problems.

• Vaccines and diagnosis reagents produced in the baculovirus platform are described.

• The use of recombinant baculovirus for gene therapy–based treatment is reviewed.

Virus-Like Particle Vaccines Against Respiratory Viruses and Protozoan Parasites

The field of vaccinology underwent massive advances over the past decades with the introduction of virus-like particles (VLPs), a supra-molecular nanoparticle vaccine platform that resembles viral structures without the ability to replicate in hosts. This innovative approach has been remarkably effective, as evidenced by its profound immunogenicity and safety. These highly desirable intrinsic properties enabled their further development as vaccines against a multitude of diseases. To date, several VLP-based vaccines have already been commercialized and many more are undergoing clinical evaluation prior to FDA approval. However, efficacious vaccines against a plethora of pathogens are still lacking, which imposes a tremendous socioeconomic burden and continues to threaten public health throughout the globe. This is especially the case for several respiratory pathogens and protozoan parasites. In this review, we briefly describe the fundamentals of VLP vaccines and the unique properties that enable these to be such valuable vaccine candidates and summarize current advances in VLP-based vaccines targeting respiratory and parasitic diseases of global importance.

Solubility Controlling Peptide Tags of Opposite Charges Generate a Bivalent Immune Response Against Dengue ED3 Serotypes 3 and 4

We previously demonstrated that a protein’s immunogenicity could be substantially increased by attaching a hydrophobic solubility controlling peptide tag (SCP-tag) producing small sub-visible aggregates. Here, we report the oligomerization of Dengue envelop protein domain 3 (ED3), and consequently, its immunogenicity increase by mixing ED3s attached with SCP-tags of opposite charges at equimolar concentration. We used ED3 of serotype 3 (D3ED3) and serotype 4 (D4ED3), which are, respectively, moderately and poorly immunogenic, and their SCP tagged variants constructed by attaching either a C-termini 5-Aspartic acid (C5D) or a 5-Lysine (C5K) tag. Light scattering indicated that the isolated tagged ED3s remained monomeric, but mixing the C5D and C5K tagged ED3s at equimolar concentration generated sub-visible aggregates or oligomers of ~500 nm through electrostatic interaction. In addition, the oligomerized ED3s remained in a native-like state, as assessed by fluorescence spectroscopy and circular dichroism. The in vivo immunogenicity of the D3ED3 and D4ED3 oligomers generated by the charged tags increased by 5 and 16 fold, respectively. Furthermore, injection of heterotypic ED3 oligomers (D3C5D+D4C5K) induced an immune response against both D3ED3 and D4ED3 in 3 of 4 responsive mice, and the IgG titer of the bivalent anti-D3C5D-D4C5K sera was over 100 times higher than that generated by co-injecting the untagged D3ED3 and D4ED3 (D3+D4). Altogether, these observations suggest that SCP-tags could be used as a platform for producing a long-sought tetravalent dengue vaccine.

Comprehensive Review on Current Interventions, Diagnostics, and Nanotechnology Perspectives against SARS-CoV-2

The coronavirus disease 2019 (COVID-19) has dramatically challenged the healthcare system of almost all countries. The authorities are struggling to minimize the mortality along with ameliorating the economic downturn. Unfortunately, until now, there has been no promising medicine or vaccine available. Herein, we deliver perspectives of nanotechnology for increasing the specificity and sensitivity of current interventional platforms toward the urgent need of quickly deployable solutions. This review summarizes the recent involvement of nanotechnology from the development of a biosensor to fabrication of a multifunctional nanohybrid system for respiratory and deadly viruses, along with the recent interventions and current understanding about severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Progress in the development of virus-like particle vaccines against respiratory viruses

Introduction: Influenza virus, human respiratory syncytial virus (RSV), and human metapneumovirus (HMPV) are important human respiratory pathogens. Recombinant virus-like particle (VLP) vaccines are suggested to be potential promising platforms to protect against these respiratory viruses. This review updates important progress in the development of VLP vaccines against respiratory viruses.Areas Covered: This review summarizes progress in developing VLP and nanoparticle-based vaccines against influenza virus, RSV, and HMPV. The PubMed was mainly used to search for important research articles published since 2010 although earlier key articles were also referenced. The research area covered includes VLP and nanoparticle platform vaccines against seasonal, pandemic, and avian influenza viruses as well as RSV and HMPV respiratory viruses. The production methods, immunogenic properties, and vaccine efficacy of respiratory VLP vaccines in preclinical animal models and clinical studies were reviewed in this article.Expert opinion: Previous and current preclinical and clinical studies suggest that recombinant VLP and nanoparticle vaccines are expected to be developed as promising alternative platforms against respiratory viruses in future. Therefore, continued research efforts are warranted.

Qualitative Profiling of the Humoral Immune Response Elicited by rVSV-ΔG-EBOV-GP Using a Systems Serology Assay, Domain Programmable Arrays

Development of an effective vaccine became a worldwide priority after the devastating 2013-2016 Ebola disease outbreak. To qualitatively profile the humoral response against advanced filovirus vaccine candidates, we developed Domain Programmable Arrays (DPA), a systems serology platform to identify epitopes targeted after vaccination or filovirus infection. We optimized the assay using a panel of well-characterized monoclonal antibodies. After optimization, we utilized the system to longitudinally characterize the immunoglobulin (Ig) isotype-specific responses in non-human primates vaccinated with rVSV-ΔG-EBOV-glycoprotein (GP). Strikingly, we observed that, although the IgM response was directed against epitopes over the whole GP, the IgG and IgA responses were almost exclusively directed against the mucin-like domain (MLD) of the glycan cap. Further research will be needed to characterize this possible biased IgG and IgA response toward the MLD, but the results corroborate that DPA is a valuable tool to qualitatively measure the humoral response after vaccination.

Neuraminidase expressing virus-like particle vaccine provides effective cross protection against influenza virus

Neuraminidase is the second major surface antigen on influenza virus. We investigated the immunogenicity and cross protective efficacy of virus-like particle containing neuraminidase derived from 2009 pandemic H1N1 influenza virus (N1 VLP) in comparison with inactivated split influenza vaccine. Immunization of mice with N1 VLP induced antibody responses specific for virus and cross-reactive neuraminidase inhibition activity whereas an inactivated split vaccine induced strain-specific hemagglutination inhibition activity. N1 VLP-immunized mice developed cross protective immunity against antigenically different influenza viruses, as determined by body weight changes, lung viral titers, infiltrating innate immune cells, and cytokines, and antibody secreting cells, and germinal center B cells. Also, N1 VLP-immune sera provided cross-protection in naïve mice. Immunity by N1 VLP vaccination was not compromised in Fc receptor γ-chain deficient mice. These results suggest that neuraminidase-presenting VLP can be developed as an effective cross-protective vaccine candidate along with current influenza vaccination.

Flagellin-expressing virus-like particles exhibit adjuvant effects on promoting IgG isotype-switched long-lasting antibody induction and protection of influenza vaccines in CD4-deficient mice

Incorporation of membrane-anchored flagellin molecules into the surfaces of influenza virus-like particles (VLP) was previously reported to promote T helper (Th) 1-biased IgG antibody production and protective efficacy of co-presented vaccine antigens. Herein, we investigated the potential adjuvant effects and mechanisms of flagellin-expressing VLP (FliC-VLP) as an independent component on influenza vaccination in wild-type and mutant mouse models. FliC-VLP adjuvanted influenza vaccination was highly effective in promoting the induction of Th1-biased IgG isotype switched antibodies, enhanced protection, and long-lasting IgG antibody responses in both wild-type and CD4-knockout mice. In contrast, the adjuvant effects of soluble flagellin were Th2-biased and required CD4 T helper cells. The adjuvant effects of FliC-VLP were less dependent on CD4 T cells and flagellin-mediated innate immune signaling pathways. The results suggest that FliC-VLP might play an effective adjuvant role in an immune competent condition as well as in a defect of CD4 T cells.

Enhancing the cross protective efficacy of live attenuated influenza virus vaccine by supplemented vaccination with M2 ectodomain virus-like particles

Current influenza vaccines including live attenuated influenza virus (LAIV) provide suboptimal protection against drift and potential pandemic strains. We hypothesized that supplementing LAIV with a highly conserved antigenic target M2 ectodomain (M2e) would confer cross-protection by inducing humoral and cellular immune responses to conserved antigenic targets. Intranasal vaccination with LAIV (A/Netherlands/602/09, H1N1) supplemented with tandem repeat M2e containing virus-like particles (M2e5x VLP) induced M2e- and virus-specific antibodies. Upon heterosubtypic virus challenge, M2e5x VLP-supplemented LAIV vaccination of mice induced significantly improved cross protection by preventing weight loss and lowering lung viral titers. Further mechanistic studies on heterosubtypic immunity suggest that T cell responses to M2e and nucleoprotein as well as systemic and mucosal antibodies to M2e and viruses might be contributing to cross protection. Therefore, this study demonstrates a novel vaccination strategy to improve the cross protective efficacy of LAIV by supplementing with a conserved M2e antigenic target.

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.

Engineering a Rugged Nanoscaffold To Enhance Plug-and-Display Vaccination

Nanoscale organization is crucial to stimulating an immune response. Using self-assembling proteins as multimerization platforms provides a safe and immunogenic system to vaccinate against otherwise weakly immunogenic antigens. Such multimerization platforms are generally based on icosahedral viruses and have led to vaccines given to millions of people. It is unclear whether synthetic protein nanoassemblies would show similar potency. Here we take the computationally designed porous dodecahedral i301 60-mer and rationally engineer this particle, giving a mutated i301 (mi3) with improved particle uniformity and stability. To simplify the conjugation of this nanoparticle, we employ a SpyCatcher fusion of mi3, such that an antigen of interest linked to the SpyTag peptide can spontaneously couple through isopeptide bond formation (Plug-and-Display). SpyCatcher-mi3 expressed solubly to high yields in Escherichia coli, giving more than 10-fold greater yield than a comparable phage-derived icosahedral nanoparticle, SpyCatcher-AP205. SpyCatcher-mi3 nanoparticles showed high stability to temperature, freeze-thaw, lyophilization, and storage over time. We demonstrate approximately 95% efficiency coupling to different transmission-blocking and blood-stage malaria antigens. Plasmodium falciparum CyRPA was conjugated to SpyCatcher-mi3 nanoparticles and elicited a high avidity antibody response, comparable to phage-derived virus-like particles despite their higher valency and RNA cargo. The simple production, precise derivatization, and exceptional ruggedness of this nanoscaffold should facilitate broad application for nanobiotechnology and vaccine development.

Virus-Like Particles Are a Superior Platform for Presenting M2e Epitopes to Prime Humoral and Cellular Immunity against Influenza Virus

Influenza virus M2 protein has a highly conserved ectodomain (M2e) as a cross-protective antigenic target. We investigated the antigenic and immunogenic properties of tandem repeat M2e (5xM2e) proteins and virus-like particles (5xM2e VLP) to better understand how VLP and protein platform vaccines induce innate and protective adaptive immune responses. Despite the high antigenic properties of 5xM2e proteins, the 5xM2e VLP was superior to 5xM2e proteins in inducing IgG2a isotype antibodies, T cell responses, plasma cells and germinal center B cells as well as in conferring cross protection. Mice primed with 5xM2e VLP were found to be highly responsive to 5xM2e protein boost, overcoming the low immunogenicity and protective efficacy of 5xM2e proteins. Immunogenic differences between VLPs and proteins in priming immune responses might be due to an intrinsic ability of 5xM2e VLP to stimulate dendritic cells secreting T helper type 1 (Th1) cytokines. We also found that 5xM2e VLP was effective in inducing inflammatory cytokines and chemokines, and in recruiting macrophages, monocytes, neutrophils, and CD11b⁺ dendritic cells at the injection site. Therefore, this study provides evidence that 5xM2e VLP is an effective vaccine platform, inducing cross-protection by stimulating innate and adaptive immune responses.

Virus-like particles presenting flagellin exhibit unique adjuvant effects on eliciting T helper type 1 humoral and cellular immune responses to poor immunogenic influenza virus M2e protein vaccine

Current licensed adjuvants including aluminum hydroxide (alum) bias immune responses toward T helper type 2 (Th2) immune responses. We tested whether virus-like particles presenting flagellin (Flag VLP) exhibit adjuvant effects on eliciting Th1 type immune responses and improving the efficacy of poor immunogenic tandem repeat M2e (M2e5x) protein vaccine against influenza virus. Co-immunization of mice with Flag VLP and M2e5x protein vaccine induced significantly higher levels of IgG2a isotype (Th1) antibodies in sera and mucosal sites, effector CD4⁺ T cells secreting IFN-γ and granzyme B, and more effective lung viral clearance and protection compared to alum adjuvant. Flag VLP stimulated primary macrophages and dendritic cells to secrete inflammatory cytokines, which is partially dependent on the Toll-like receptor 5. This study provides insight into developing effective vaccine adjuvants.

Developing a platform system for gene delivery: amplifying virus-like particles (AVLP) as an influenza vaccine

Delivery of a gene of interest to target cells is highly desirable for translational medicine, such as gene therapy, regenerative medicine, vaccine development, and studies of gene function. Parainfluenza virus 5 (PIV5), a paramyxovirus with a negative-sense RNA genome, normally infects cells without causing obvious cytopathic effect, and it can infect many cell types. To exploit these features of PIV5, we established a system generating self-amplifying, virus-like particles (AVLP). Using enhanced green fluorescent protein (EGFP) as a reporter, AVLP encoding EGFP (AVLP–EGFP) successfully delivered and expressed the EGFP gene in primary human cells, including stem cells, airway epithelial cells, monocytes, and T cells. To demonstrate the application of this system for vaccine development, we generated AVLPs to express the HA and M1 antigens from the influenza A virus strain H5N1 (AVLP–H5 and AVLP–M1H5). Immunization of mice with AVLP–H5 and AVLP–M1H5 generated robust antibody and cellular immune responses. Vaccination with a single dose of AVLP–H5 and M1H5 completely protected mice against lethal H5N1 challenge, suggesting that the AVLP-based system is a promising platform for delivery of desirable genes.

An ‘imitation virus’ can be used to deliver genetic material to target cells, with farreaching potential for medical application. The capacity to safely and affordably introduce genes into cells is highly-sought. A team led by the University of Georgia’s Biao He created a protein shell using parainfluenza virus 5 proteins, with the resultant particles possessing the ability to infect multiple types of cell and deliver desired genetic material. The team proved the utility of their system by using it to express immunity-promoting components of avian influenza virus in live mice—successfully vaccinating the animals, and enabling them to survive a subsequent lethal infection. His group also showed that their system is also able to deliver and express genes in human cells, prompting further research into this useful tool.

Influenza virus-like particles harboring H9N2 HA and NA proteins induce a protective immune response in chicken

Background

Avian influenza viruses represent a growing threat of an influenza pandemic. The co‐circulation of multiple H9N2 genotypes over the past decade has been replaced by one predominant genotype—G57 genotype, which displays a changed antigenicity and improved adaptability in chickens. Effective H9N2 subtype avian influenza virus vaccines for poultry are urgently needed.

Objective

In this study, we constructed H9N2 subtype avian influenza virus‐like particle (VLP) and evaluated its protective efficacy in specific pathogen‐free (SPF) chickens to lay the foundation for developing an effective vaccine against influenza viruses.

Methods

Expression of influenza proteins in VLPs was confirmed by Western blot, hemagglutination inhibition (HI), and neuraminidase inhibition (NI). The morphology was observed by electron microscopy. A group of 15 three‐week‐old SPF chickens was divided into three subgroups of five chickens immunized with VLP, commercial vaccine, and PBS. Challenge study was performed to evaluate efficacy of VLP vaccine.

Results and Conclusions

The hemagglutinin (HA) and neuraminidase (NA) proteins were co‐expressed in the infected cells, self‐assembled, and were released into the culture medium in the form of VLPs of diameter ~80 nm. The VLPs exhibited some functional characteristics of a full influenza virus, including hemagglutination and neuraminidase activity. In SPF chickens, the VLPs elicited serum antibodies specific for H9N2 and induced a higher HI titer (as detected by a homologous antigen) than did a commercial H9N2 vaccine (A/chicken/Shanghai/F/1998). Viral shedding from VLP vaccine subgroup was reduced compared with commercial vaccine subgroup and control subgroup.

A Bivalent Heterologous DNA Virus-Like-Particle Prime-Boost Vaccine Elicits Broad Protection against both Group 1 and 2 Influenza A Viruses

Current seasonal influenza vaccines are efficacious when vaccine strains are matched with circulating strains. However, they do not protect antigenic variants and newly emerging pandemic and outbreak strains. Thus, there is a critical need for developing so-called "universal" vaccines that protect against all influenza viruses. In the present study, we developed a bivalent heterologous DNA virus-like particle prime-boost vaccine strategy. We show that mice immunized with this vaccine were broadly protected against lethal challenge from group 1 (H1, H5, and H9) and group 2 (H3 and H7) viruses, with 94% aggregate survival. To determine the immune correlates of protection, we performed passive immunizations and in vitro assays. We show that this vaccine elicited antibody responses that bound HA from group 1 (H1, H2, H5, H6, H8, H9, H11, and H12) and group 2 (H3, H4, H7, H10, H14, and H15) and neutralized homologous and intrasubtypic H5 and H7 and heterosubtypic H1 viruses and hemagglutinin-specific CD4 and CD8 T cell responses. As a result, passive immunization with immune sera fully protected mice against H5, H7, and H1 challenge, whereas with both immune sera and T cells the mice survived heterosubtypic H3 and H9 challenge. Thus, it appears that (i) neutralizing antibodies alone fully protect against homologous and intrasubtypic H5 and H7 and (ii) neutralizing and binding antibodies are sufficient to protect against heterosubtypic H1, (iii) but against heterosubtypic H3 and H9, binding antibodies and T cells are required for complete survival. We believe that this vaccine regimen could potentially be a candidate for a "universal" influenza vaccine.IMPORTANCE Influenza virus infection is global health problem. Current seasonal influenza vaccines are efficacious only when vaccine strains are matched with circulating strains. However, these vaccines do not protect antigenic variants and newly emerging pandemic and outbreak strains. Because of this, there is an urgent need to develop so-called "universal" influenza vaccines that can protect against both current and future influenza strains. In the present study, we developed a bivalent heterologous prime-boost vaccine strategy. We show that a bivalent vaccine regimen elicited broad binding and neutralizing antibody and T cell responses that conferred broad protection against diverse challenge viruses in mice, suggesting that this bivalent prime-boost strategy could practically be a candidate for a "universal" influenza vaccine.

A review of studies of the proteomes of circulating microparticles: key roles for galectin-3-binding protein-expressing microparticles in vascular diseases and systemic lupus erythematosus

Subcellular microvesicles (MVs) have attracted increasing interest during the past decades. While initially considered as inert cellular debris, several important roles for MVs in physiological homeostasis, cancer, cardiovascular, and autoimmune diseases have been uncovered. Although still poorly understood, MVs are involved in trafficking of information from cell-to-cell, and are implicated in the regulation of immunity, thrombosis, and coagulation. Different subtypes of extracellular MVs exist. This review focuses on the cell membrane-derived shedded MVs (ranging in size from 200 to 1000 nm) typically termed microparticles (MPs). The numbers and particularly the composition of MPs appear to reflect the state of their parental cells and MPs may therefore carry great potential as clinical biomarkers which can be elucidated and developed by proteomics in particular. Determination of the identity of the specific proteins and their quantities, i.e. the proteome, in complex samples such as MPs enables an in-depth characterization of the phenotypical changes of the MPs during disease states. At present, only a limited number of proteomic studies of circulating MPs have been carried out in healthy individuals and disease populations. Interestingly, these studies indicate that a small set of MP-proteins, in particular, overexpression of galectin-3-binding protein (G3BP) distinguish MPs in patients with venous thromboembolism and the systemic autoimmune disease, systemic lupus erythematosus (SLE). G3BP is important in cell–cell adhesion, clearance, and intercellular signaling. MPs overexpressing G3BP may thus be involved in thrombosis and hemostasis, vascular inflammation, and autoimmunity, further favoring G3BP as a marker of “pathogenic” MPs. MPs expressing G3BP may also hold a potential as biomarkers in other conditions such as cancer and chronic viral infections. This review highlights the methodology and results of the proteome studies behind these discoveries and places them in a pathophysiological and biomarker perspective.

Exploration of the BF2*15 major histocompatibility complex class I binding motif and identification of cytotoxic T lymphocyte epitopes from the H5N1 influenza virus nucleoprotein in chickens

The binding motif of BF2*15 major histocompatibility complex (MHC) class I was explored by analyzing the interaction between an infectious bronchitis virus octapeptide and BF2*15, and the cytotoxic T lymphocyte (CTL) epitope from the nucleoprotein (NP) of H5N1 virus was identified using experimental methods. Computational methods, including homology modeling, molecular dynamics simulation, and molecular docking analysis, were used. The recombinant plasmid pCAGGS-NP was constructed, and NP expression was confirmed by indirect immunofluorescence and Western blot in transfected 293T cells. Antibodies against NP in pCAGGS-NP-inoculated specific-pathogen-free chickens were detected by enzyme-linked immunosorbent assay (ELISA). Interferon γ (IFN-γ) mRNA was quantified, and IFN-γ production was evaluated using quantitative reverse transcription PCR and capture ELISA, respectively. CD8(+) T-lymphocyte proliferation was detected using flow cytometric analysis. The BF2*15 MHC class I binding motif "x-Arg/Lys-x-x-x-Arg/Lys" was explored. Quantification of chicken IFN-γ mRNA, evaluation of IFN-γ production, and measurement of CD8(+) T-lymphocyte proliferation confirmed that the peptide NP67-74 of H5N1 was the BF2*15 MHC-class-I-restricted CTL epitope.

Production of Influenza Virus HA1 Harboring Native-Like Epitopes by Pichia pastoris

The outbreak of the H5N1 highly pathogenic avian influenza which exhibits high variation had brought a serious threat to the safety of humanity. To overcome this high variation, hemagglutinin-based recombinant subunit vaccine with rational design has been considered as a substitute for traditional virion-based vaccine development. Here, we expressed HA1 part of the hemagglutinin protein using the Pichia pastoris expression system and attained a high yield of about 120 mg/L through the use of fed-batch scalable fermentation. HA1 protein in the culture supernatant was purified using two-step ion-exchange chromatography. The resultant HA1 protein was homogeneous in solution in a glycosylated form, as confirmed by endoglycosidase H treatment. Sedimentation velocity tests, silver staining of protein gels, and immunoblotting were used for verification. The native HA1 reacted well with conformational, cross-genotype, neutralizing monoclonal antibodies, whereas a loss of binding activity was noted with the denatured HA1 form. Moreover, the murine anti-HA1 serum exhibited a virus-capture capability in the hemagglutination inhibition assay, which suggests that HA1 harbors native-like epitopes. In conclusion, soluble HA1 was efficiently expressed and purified in this study. The functional glycosylated protein will be an alternative for the development of recombinant protein-based influenza vaccine.

Virus like particle-based vaccines against emerging infectious disease viruses

Emerging infectious diseases are major threats to human health. Most severe viral disease outbreaks occur in developing regions where health conditions are poor. With increased international travel and business, the possibility of eventually transmitting infectious viruses between different countries is increasing. The most effective approach in preventing viral diseases is vaccination. However, vaccines are not currently available for numerous viral diseases. Virus-like particles (VLPs) are engineered vaccine candidates that have been studied for decades. VLPs are constructed by viral protein expression in various expression systems that promote the selfassembly of proteins into structures resembling virus particles. VLPs have antigenicity similar to that of the native virus, but are non-infectious as they lack key viral genetic material. VLP vaccines have attracted considerable research interest because they offer several advantages over traditional vaccines. Studies have shown that VLP vaccines can stimulate both humoral and cellular immune responses, which may offer effective antiviral protection. Here we review recent developments with VLP-based vaccines for several highly virulent emerging or re-emerging infectious diseases. The infectious agents discussed include RNA viruses from different virus families, such as the Arenaviridae, Bunyaviridae, Caliciviridae, Coronaviridae, Filoviridae, Flaviviridae, Orthomyxoviridae, Paramyxoviridae, and Togaviridae families.

CD47 Plays a Role as a Negative Regulator in Inducing Protective Immune Responses to Vaccination against Influenza Virus

An integrin-associated protein CD47, which is a ligand for the inhibitory receptor signal regulatory protein α, is expressed on B and T cells, as well as on most innate immune cells. However, the roles of CD47 in the immune responses to viral infection or vaccination remain unknown. We investigated the role of CD47 in inducing humoral immune responses after intranasal infection with virus or immunization with influenza virus-like particles (VLPs). Virus infection or vaccination with VLPs containing hemagglutinin from A/PR8/34 influenza virus induced higher levels of antigen-specific IgG2c isotype dominant antibodies in CD47-deficient (CD47KO) mice than in wild-type (WT) mice. CD47KO mice with vaccination showed greater protective efficacy against lethal challenge, as evidenced by no loss in body weight and reduced lung viral titers compared to WT mice. In addition, inflammatory responses which include cytokine production, leukocyte infiltrates, and gamma interferon-producing CD4(+) T cells, as well as an anti-inflammatory cytokine (interleukin-10), were reduced in the lungs of vaccinated CD47KO mice after challenge with influenza virus. Analysis of lymphocytes indicated that GL7(+) germinal center B cells were induced at higher levels in the draining lymph nodes of CD47KO mice compared to those in WT mice. Notably, CD47KO mice exhibited significant increases in the numbers of antigen-specific memory B cells in spleens and plasma cells in bone marrow despite their lower levels of background IgG antibodies. These results suggest that CD47 plays a role as a negative regulator in inducing protective immune responses to influenza vaccination.

IMPORTANCE

Molecular mechanisms that control B cell activation to produce protective antibodies upon viral vaccination remain poorly understood. The CD47 molecule is known to be a ligand for the inhibitory receptor signal regulatory protein α and expressed on the surfaces of most immune cell types. CD47 was previously demonstrated to play an important role in modulating the migration of monocytes, neutrophils, polymorphonuclear neutrophils, and dendritic cells into the inflamed tissues. The results of this study demonstrate new roles of CD47 in negatively regulating the induction of protective IgG antibodies, germinal center B cells, and plasma cells secreting antigen-specific antibodies, as well as macrophages, upon influenza vaccination and challenge. As a consequence, vaccinated CD47-deficient mice demonstrated better control of influenza viral infection and enhanced protection. This study provides insights into understanding the regulatory functions of CD47 in inducing adaptive immunity to vaccination.

Progress in developing virus-like particle influenza vaccines

Recombinant vaccines based on virus-like particles (VLPs) or nanoparticles have been successful in their safety and efficacy in preclinical and clinical studies. The technology of expressing enveloped VLP vaccines has combined with molecular engineering of proteins in membrane-anchor and immunogenic forms mimicking the native conformation of surface proteins on the enveloped viruses. This review summarizes recent developments in influenza VLP vaccines against seasonal, pandemic, and avian influenza viruses from the perspective of use in humans. The immunogenicity and efficacies of influenza VLP vaccine in the homologous and cross-protection were reviewed. Discussions include limitations of current influenza vaccination strategies and future directions to confer broadly cross protective new influenza vaccines as well as vaccination.

"Kill" the messenger: Targeting of cell-derived microparticles in lupus nephritis

Immune complex (IC) deposition in the glomerular basement membrane (GBM) is a key early pathogenic event in lupus nephritis (LN). The clarification of the mechanisms behind IC deposition will enable targeted therapy in the future. Circulating cell-derived microparticles (MPs) have been proposed as major sources of extracellular autoantigens and ICs and triggers of autoimmunity in LN. The overabundance of galectin-3-binding protein (G3BP) along with immunoglobulins and a few other proteins specifically distinguish circulating MPs in patients with systemic lupus erythematosus (SLE), and this is most pronounced in patients with active LN. G3BP co-localizes with deposited ICs in renal biopsies from LN patients supporting a significant presence of MPs in the IC deposits. G3BP binds strongly to glomerular basement membrane proteins and integrins. Accordingly, MP surface proteins, especially G3BP, may be essential for the deposition of ICs in kidneys and thus for the ensuing formation of MP-derived electron dense structures in the GBM, and immune activation in LN. This review focuses on the notion of targeting surface molecules on MPs as an entirely novel treatment strategy in LN. By targeting MPs, a double hit may be achieved by attenuating both the autoantigenic fueling of immune complexes and the triggering of the adaptive immune system. Thereby, early pathogenic events may be blocked in contrast to current treatment strategies that primarily target and modulate later events in the cellular and humoral immune response.

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.

Antibody Persistence in Adults Two Years after Vaccination with an H1N1 2009 Pandemic Influenza Virus-Like Particle Vaccine

The influenza virus is a human pathogen that causes epidemics every year, as well as potential pandemic outbreaks, as occurred in 2009. Vaccination has proven to be sufficient in the prevention and containment of viral spreading. In addition to the current egg-based vaccines, new and promising vaccine platforms, such as cell culture-derived vaccines that include virus-like particles (VLPs), have been developed. VLPs have been shown to be both safe and immunogenic against influenza infections. Although antibody persistence has been studied in traditional egg-based influenza vaccines, studies on antibody response durations induced by VLP influenza vaccines in humans are scarce. Here, we show that subjects vaccinated with an insect cell-derived VLP vaccine, in the midst of the 2009 H1N1 influenza pandemic outbreak in Mexico City, showed antibody persistence up to 24 months post-vaccination. Additionally, we found that subjects that reported being revaccinated with a subsequent inactivated influenza virus vaccine showed higher antibody titres to the pandemic influenza virus than those who were not revaccinated. These findings provide insights into the duration of the antibody responses elicited by an insect cell-derived pandemic influenza VLP vaccine and the possible effects of subsequent influenza vaccination on antibody persistence induced by this VLP vaccine in humans.

Lessons learned from successful human vaccines: Delineating key epitopes by dissecting the capsid proteins

Recombinant VLP-based vaccines have been successfully used against 3 diseases caused by viral infections: Hepatitis B, cervical cancer and hepatitis E. The VLP approach is attracting increasing attention in vaccine design and development for human and veterinary use. This review summarizes the clinically relevant epitopes on the VLP antigens in successful human vaccines. These virion-like epitopes, which can be delineated with molecular biology, cryo-electron microscopy and x-ray crystallographic methods, are the prerequisites for these efficacious vaccines to elicit functional antibodies. The critical epitopes and key factors influencing these epitopes are discussed for the HEV, HPV and HBV vaccines. A pentamer (for HPV) or a dimer (for HEV and HBV), rather than a monomer, is the basic building block harboring critical epitopes for the assembly of VLP antigen. The processing and formulation of VLP-based vaccines need to be developed to promote the formation and stabilization of these epitopes in the recombinant antigens. Delineating the critical epitopes is essential for antigen design in the early phase of vaccine development and for critical quality attribute analysis in the commercial phase of vaccine manufacturing.

Effect of AcHERV-GmCSF as an Influenza Virus Vaccine Adjuvant

Introduction

The first identification of swine-originated influenza A/CA/04/2009 (pH1N1) as the cause of an outbreak of human influenza accelerated efforts to develop vaccines to prevent and control influenza viruses. The current norm in many countries is to prepare influenza vaccines using cell-based or egg-based killed vaccines, but it is difficult to elicit a sufficient immune response using this approach. To improve immune responses, researchers have examined the use of cytokines as vaccine adjuvants, and extensively investigated their functions as chemoattractants of immune cells and boosters of vaccine-mediated protection. Here, we evaluated the effect of Granulocyte-macrophage Colony-Stimulating Factor (GmCSF) as an influenza vaccine adjuvant in BALB/c mice.

Method and Results

Female BALB/c mice were immunized with killed vaccine together with a murine GmCSF gene delivered by human endogenous retrovirus (HERV) envelope coated baculovirus (1×10⁷ FFU AcHERV-GmCSF, i.m.) and were compared with mice immunized with the killed vaccine alone. On day 14, immunized mice were challenged with 10 median lethal dose of mouse adapted pH1N1 virus. The vaccination together with GmCSF treatment exerted a strong adjuvant effect on humoral and cellular immune responses. In addition, the vaccinated mice together with GmCSF were fully protected against infection by the lethal influenza pH1N1 virus.

Conclusion

Thus, these results indicate that AcHERV-GmCSF is an effective molecular adjuvant that augments immune responses against influenza virus.

ISCOMATRIX™ adjuvant promotes epitope spreading and antibody affinity maturation of influenza A H7N9 virus like particle vaccine that correlate with virus neutralization in humans

In a previously reported phase I clinical trial, subjects vaccinated with two doses of an unadjuvanted H7N9 virus like particle (VLP) vaccine responded poorly (15.6% seroconversion rates with 45μg hemagglutinin (HA) dose). In contrast, 80.6% of subjects receiving H7N9 VLP vaccine (5μg HA) with ISCOMATRIX™ adjuvant developed hemagglutination-inhibition (HI) responses. To better understand the role of adjuvant, complete antibody epitope repertoires of post-vaccination sera were investigated using Whole Genome Fragment Phage Display Library (GFPDL). In addition, antibody affinity maturation following vaccination was measured against HA1 and HA2 antigenic domains using real time Surface Plasmon Resonance (SPR) based kinetic assays. Unadjuvanted H7N9-VLP vaccine generated primarily antibodies targeting the C-terminus of the HA1 domain, predicted to be mostly buried on the native HA spikes, while adjuvanted VLP vaccine generated antibodies against large epitopes in the HA1 spanning the receptor binding domain (RBD). SPR analysis using a functional H7-HA1 domain demonstrated that sera from adjuvanted H7N9-VLP vaccine induced higher total binding antibodies and significantly higher antibody affinity maturation to HA1 compared to sera from unadjuvanted vaccine. Total antibody binding and affinity to the HA1 (but not HA2) domain correlated with HI and neutralization titers. This study demonstrates that ISCOMATRIX™ adjuvanted vaccine promotes higher quality antibody immune response against avian influenza in naïve humans.

The baculovirus expression vector system: A commercial manufacturing platform for viral vaccines and gene therapy vectors

The baculovirus expression vector system (BEVS) platform has become an established manufacturing platform for the production of viral vaccines and gene therapy vectors. Nine BEVS-derived products have been approved - four for human use (Cervarix(®), Provenge(®), Glybera(®) and Flublok(®)) and five for veterinary use (Porcilis(®) Pesti, BAYOVAC CSF E2(®), Circumvent(®) PCV, Ingelvac CircoFLEX(®) and Porcilis(®) PCV). The BEVS platform offers many advantages, including manufacturing speed, flexible product design, inherent safety and scalability. This combination of features and product approvals has previously attracted interest from academic researchers, and more recently from industry leaders, to utilize BEVS to develop next generation vaccines, vectors for gene therapy, and other biopharmaceutical complex proteins. In this review, we explore the BEVS platform, detailing how it works, platform features and limitations and important considerations for manufacturing and regulatory approval. To underscore the growth in opportunities for BEVS-derived products, we discuss the latest product developments in the gene therapy and influenza vaccine fields that follow in the wake of the recent product approvals of Glybera(®) and Flublok(®), respectively. We anticipate that the utility of the platform will expand even further as new BEVS-derived products attain licensure. Finally, we touch on some of the areas where new BEVS-derived products are likely to emerge.

Advances in the development of influenza virus vaccines

Influenza virus infections are a major public health concern and cause significant morbidity and mortality worldwide. Current influenza virus vaccines are an effective countermeasure against infection but need to be reformulated almost every year owing to antigenic drift. Furthermore, these vaccines do not protect against novel pandemic strains, and the timely production of pandemic vaccines remains problematic because of the limitations of current technology. Several improvements have been made recently to enhance immune protection induced by seasonal and pandemic vaccines, and to speed up production in case of a pandemic. Importantly, vaccine constructs that induce broad or even universal influenza virus protection are currently in preclinical and clinical development.

Systems biology from virus to humans

Natural infection and then recovery are considered to be the most effective means for hosts to build protective immunity. Thus, mimicking natural infection of pathogens, many live attenuated vaccines such as influenza virus, and yellow fever vaccine 17D were developed and have been successfully used to induce protective immunity. However, humans fail to generate long-term protective immunity to some pathogens after natural infection such as influenza virus, respiratory syncytial virus (RSV), and human immunodeficiency virus (HIV) even if they survive initial infections. Many vaccines are suboptimal since much mortality is still occurring, which is exampled by influenza and tuberculosis. It is critically important to increase our understanding on protein components of pathogens and vaccines as well as cellular and host responses to infections and vaccinations. Here, we highlight recent advances in gene transcripts and protein analysis results in the systems biology to enhance our understanding of viral pathogens, vaccines, and host cell responses.

Adenovirus-based vaccines against avian-origin H5N1 influenza viruses

Since 1997, human infection with avian H5N1, having about 60% mortality, has posed a threat to public health. In this review, we describe the epidemiology of H5N1 transmission, advantages and disadvantages of different influenza vaccine types, and characteristics of adenovirus, finally summarizing advances in adenovirus-based H5N1 systemic and mucosal vaccines.

Advances and challenges in the development and production of effective plant-based influenza vaccines

Influenza infections continue to present a major threat to public health. Traditional modes of influenza vaccine manufacturing are failing to satisfy the global demand because of limited scalability and long production timelines. In contrast, subunit vaccines (SUVs) can be produced in heterologous expression systems in shorter times and at higher quantities. Plants are emerging as a promising platform for SUV production due to time efficiency, scalability, lack of harbored mammalian pathogens and possession of the machinery for eukaryotic post-translational protein modifications. So far, several organizations have utilized plant-based transient expression systems to produce SUVs against influenza, including vaccines based on virus-like particles. Plant-produced influenza SUV candidates have been extensively evaluated in animal models and some have shown safety and immunogenicity in clinical trials. Here, the authors review ongoing efforts and challenges to producing influenza SUV candidates in plants and discuss the likelihood of bringing these products to the market.

Adjuvanted influenza vaccines

Influenza is one of the most common causes of human morbidity and mortality that is preventable by vaccination. Immunization with available vaccines provides incomplete protection against illness caused by influenza virus, especially in high-risk groups such as the elderly and young children. Thus, more efficacious vaccines are needed for the entire population, and all the more so for high-risk groups. One way to improve immune responses and protection is to formulate the vaccine with antigen carriers and/or adjuvants, which can play an important role in improving immune responses and delivery to antigen-presenting cells, especially for a vaccine like influenza that is based on protein antigens usually administered without a carrier or adjuvant. In this review, the authors present an overview of available vaccines, focusing on research and development of new adjuvants used in influenza vaccines, as well as adjuvanted influenza vaccines aimed to improve immune responses, protection and breadth of coverage for influenza.