Efficacy, immunogenicity, and safety of a plant-derived, quadrivalent, virus-like particle influenza vaccine in adults (18-64 years) and older adults (≥65 years): two multicentre, randomised phase 3 trials

Immunogenicity and safety evaluation of a newly manufactured recombinant Baculovirus-Expressed quadrivalent influenza vaccine in adults 18 years old and Above: An Open-Label, phase III extension study

In the face of global health threats, there is a growing demand for vaccines that can be manufactured on a large scale within compressed timeline. This study responds to this imperative by delving into the evaluation of FluGuard, a novel recombinant influenza vaccine developed by Nivad Pharmed Salamat Company in Iran. Positioned as a phase 3 extension, the research aimed to evaluate the safety and immunogenicity of FluGuard in volunteers aged 18 and above. The study was conducted as a single-center, open-label clinical trial. All eligible volunteers received FluGuard (2021-2022 Formula) on day 0. Safety assessments occurred at days 1, 4, 7, 14, 28 and 42 post-vaccination. Immunogenicity was measured through seroconversion, seroprotection, and geometric mean titer fold increase in subgroups of 250 volunteers. Among the 4,260 volunteers were screened and assessed for eligibility, 1000 were enrolled. At day 28 post-vaccination, seroconversion rates for A/H1N1, A/H3N2, B/Yamagata, B/Victoria were 53.4 % [95 %CI: 46.7-60], 57.7 % [95 %CI: 51.1-64.3], 54.3 % [95 %CI: 47.7-60.9], and 36.2 % [95 %CI: 29.8-42.6], respectively in volunteers 18 years and above. The most common solicited adverse events were pain at the injection site, malaise, and headache. No suspected unexpected adverse events and adverse events of special interest occurred during the study period. Our findings suggested that FluGuard® exhibits a desirable safety profile and provides sufficient immunogenicity against influenza virus types A and B. However, extended studies are warranted to assess the long-term protective efficacy. Trial Registration: The study protocol was accepted by Iranian registry of clinical trial; https://www.irct.ir; IRCT20201104049265N2.

Development of a dual immunochromatographic test strip to detect E2 and Erns antibodies against classical swine fever

Background

It is essential to consider a practical antibody test to successfully implement marker vaccines and validate vaccination efficacy against classical swine fever virus (CSFV). The test should include a serological antibody assay, combined with a tool for differentiating infected from vaccinated animals (DIVA). The immunochromatographic test strip (ICS) has been exclusively designed for detecting CSFV E2 antibodies while lacking in detecting Erns antibodies, which can be employed and satisfy DIVA strategy. This study developed a novel ICS for detecting CSFV E2/Erns dual-antibody. The effectiveness of ICS in evaluating the DIVA capability of two novel chimeric pestivirus vaccine candidates was assessed.

Methods

Recombinant E2 or Erns protein was transiently expressed in the plant benthamiana using Agrobacterium tumefaciens. ICS was subsequently assembled, and goat anti-rabbit IgG and recombinant CSFV E2 or Erns protein were plated onto the nitrocellulose membrane as control and test lines, respectively. The sensitivity and specificity of ICS were evaluated using sera with different neutralizing antibody titers or positive for antibodies against CSFV and other pestiviruses. The coincidence rates for detecting E2 and Erns antibodies between ICS and commercial enzyme-linked immunosorbent assay (ELISA) kits were also computed. ICS performance for DIVA capability was evaluated using sera from pigs vaccinated with conventional vaccine or chimeric vaccine candidates.

Results

E2 and Erns proteins were successfully expressed in N. benthamiana-produced recombinant proteins. ICS demonstrated high sensitivity in identifying CSFV E2 and Erns antibodies, even at the low neutralizing antibody titers. No cross-reactivity with antibodies from other pestiviruses was confirmed using ICS. There were high agreement rates of 93.0 and 96.5% between ICS and two commercial ELISA kits for E2 antibody testing. ICS also achieved strong coincidence rates of 92.9 and 89.3% with two ELISA kits for Erns antibody detection. ICS confirmed the absence of CSFV Erns-specific antibodies in sera from pigs vaccinated with chimeric vaccine candidates.

Conclusion

E2 and Erns proteins derived from the plant showed great potential and can be used to engineer a CSFV E2/Erns dual-antibody ICS. The ICS was also highly sensitive and specific for detecting CSFV E2 and Erns antibodies. Significantly, ICS can fulfill the DIVA concept by incorporating chimeric vaccine candidates.

Development of Virus-like Particle Plant-Based Vaccines against Avian H5 and H9 Influenza A Viruses

Avian influenza A virus (AIV) is a significant cause of mortality in poultry, causing substantial economic loss, particularly in developing countries, and has zoonotic potential. For example, highly pathogenic avian influenza (HPAI) viruses of the H5 subtype have been circulating in Egypt for around two decades. In the last decade, H5N1 viruses of clade 2.2.1 have been succeeded by the antigenically distinct H5N8 clade 2.3.4.4b viruses. Furthermore, H9N2 viruses co-circulate with the H5N8 viruses in Egyptian poultry. It is widely recognised that effective vaccination against IAV requires a close antigenic match between the vaccine and viruses circulating in the field. Therefore, approaches to develop cost-effective vaccines that can be rapidly adapted to local virus strains are required for developing countries such as Egypt. In this project, the haemagglutinin (HA) proteins of Egyptian H5 and H9 viruses were expressed by transient transfection of plants (Nicotiana benthamiana). The formation of virus-like particles (VLPs) was confirmed by transmission electron microscopy. Mice were immunised with four doses of either H5 or H9 VLPs with adjuvant. Antibody and cellular immune responses were measured against the corresponding recombinant protein using ELISA and enzyme-linked immunosorbent assay (ELISpot), respectively. Chickens were immunised with one dose of H5 VLPs, eliciting HA-specific antibodies measured by ELISA and a pseudotyped virus neutralisation test using a heterologous H5 HA. In conclusion, plant-based VLP vaccines have potential for producing an effective vaccine candidate within a short time at a relatively low cost.

Fighting flu: novel CD8+ T-cell targets are required for future influenza vaccines

Seasonal influenza viruses continue to cause severe medical and financial complications annually. Although there are many licenced influenza vaccines, there are billions of cases of influenza infection every year, resulting in the death of over half a million individuals. Furthermore, these figures can rise in the event of a pandemic, as seen throughout history, like the 1918 Spanish influenza pandemic (50 million deaths) and the 1968 Hong Kong influenza pandemic (~4 million deaths). In this review, we have summarised many of the currently licenced influenza vaccines available across the world and current vaccines in clinical trials. We then briefly discuss the important role of CD8+ T cells during influenza infection and why future influenza vaccines should consider targeting CD8+ T cells. Finally, we assess the current landscape of known immunogenic CD8+ T-cell epitopes and highlight the knowledge gaps required to be filled for the design of rational future influenza vaccines that incorporate CD8+ T cells.

Protective efficacy of a plant-produced beta variant rSARS-CoV-2 VLP vaccine in golden Syrian hamsters

In the quest for heightened protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants, we engineered a prototype vaccine utilizing the plant expression system of Nicotiana benthamiana, to produce a recombinant SARS-CoV-2 virus-like particle (VLP) vaccine presenting the S-protein from the Beta (B.1.351) variant of concern (VOC). This innovative vaccine, formulated with either a squalene oil-in-water emulsion or a synthetic CpG oligodeoxynucleotide adjuvant, demonstrated efficacy in a golden Syrian Hamster challenge model. The Beta VLP vaccine induced a robust humoral immune response, with serum exhibiting neutralization not only against SARS-CoV-2 Beta but also cross-neutralizing Delta and Omicron pseudoviruses. Protective efficacy was demonstrated, evidenced by reduced viral RNA copies and mitigated weight loss and lung damage compared to controls. This compelling data instills confidence in the creation of a versatile platform for the local manufacturing of potential pan-sarbecovirus vaccines, against evolving viral threats.

Medicinal Plants against Viral Infections: A Review of Metabolomics Evidence for the Antiviral Properties and Potentials in Plant Sources

Most plants have developed unique mechanisms to cope with harsh environmental conditions to compensate for their lack of mobility. A key part of their coping mechanisms is the synthesis of secondary metabolites. In addition to their role in plants' defense against pathogens, they also possess therapeutic properties against diseases, and their use by humans predates written history. Viruses are a unique class of submicroscopic agents, incapable of independent existence outside a living host. Pathogenic viruses continue to pose a significant threat to global health, leading to innumerable fatalities on a yearly basis. The use of medicinal plants as a natural source of antiviral agents has been widely reported in literature in the past decades. Metabolomics is a powerful research tool for the identification of plant metabolites with antiviral potentials. It can be used to isolate compounds with antiviral capacities in plants and study the biosynthetic pathways involved in viral disease progression. This review discusses the use of medicinal plants as antiviral agents, with a special focus on the metabolomics evidence supporting their efficacy. Suggestions are made for the optimization of various metabolomics methods of characterizing the bioactive compounds in plants and subsequently understanding the mechanisms of their operation.

A preliminary study of the immunogenic response of plant-derived multi-epitopic peptide vaccine candidate of Mycoplasma gallisepticum in chickens

Mycoplasma gallisepticum (MG) is responsible for chronic respiratory disease in avian species, characterized by symptoms like respiratory rales and coughing. Existing vaccines for MG have limited efficacy and require multiple doses. Certain MG cytoadherence proteins (GapA, CrmA, PlpA, and Hlp3) play a crucial role in the pathogen's respiratory tract colonization and infection. Plant-based proteins and therapeutics have gained attention due to their safety and efficiency. In this study, we designed a 21.4-kDa multi-epitope peptide vaccine (MEPV) using immunogenic segments from cytoadherence proteins. The MEPV's effectiveness was verified through computational simulations. We then cloned the MEPV, introduced it into the plant expression vector pSiM24-eGFP, and expressed it in Nicotiana benthamiana leaves. The plant-produced MEPV proved to be immunogenic when administered intramuscularly to chickens. It significantly boosted the production of immunoglobulin Y (IgY)-neutralizing antibodies against cytoadherence protein epitopes in immunized chickens compared to that in the control group. This preliminary investigation demonstrates that the plant-derived MEPV is effective in triggering an immune response in chickens. To establish an efficient poultry health management system and ensure the sustainability of the poultry industry, further research is needed to develop avian vaccines using plant biotechnology.

Multifactorial analysis of terminator performance on heterologous gene expression in Physcomitrella

KEY MESSAGE

Characterization of Physcomitrella 3'UTRs across different promoters yields endogenous single and double terminators for usage in molecular pharming. The production of recombinant proteins for health applications accounts for a large share of the biopharmaceutical market. While many drugs are produced in microbial and mammalian systems, plants gain more attention as expression hosts to produce eukaryotic proteins. In particular, the good manufacturing practice (GMP)-compliant moss Physcomitrella (Physcomitrium patens) has outstanding features, such as excellent genetic amenability, reproducible bioreactor cultivation, and humanized protein glycosylation patterns. In this study, we selected and characterized novel terminators for their effects on heterologous gene expression. The Physcomitrella genome contains 53,346 unique 3'UTRs (untranslated regions) of which 7964 transcripts contain at least one intron. Over 91% of 3'UTRs exhibit more than one polyadenylation site, indicating the prevalence of alternative polyadenylation in Physcomitrella. Out of all 3'UTRs, 14 terminator candidates were selected and characterized via transient Dual-Luciferase assays, yielding a collection of endogenous terminators performing equally high as established heterologous terminators CaMV35S, AtHSP90, and NOS. High performing candidates were selected for testing as double terminators which impact reporter levels, dependent on terminator identity and positioning. Testing of 3'UTRs among the different promoters NOS, CaMV35S, and PpActin5 showed an increase of more than 1000-fold between promoters PpActin5 and NOS, whereas terminators increased reporter levels by less than tenfold, demonstrating the stronger effect promoters play as compared to terminators. Among selected terminator attributes, the number of polyadenylation sites as well as polyadenylation signals were found to influence terminator performance the most. Our results improve the biotechnology platform Physcomitrella and further our understanding of how terminators influence gene expression in plants in general.

Enhanced binding and inhibition of SARS-CoV-2 by a plant-derived ACE2 protein containing a fused mu tailpiece

Infectious diseases such as Coronavirus disease 2019 (COVID-19) and Middle East respiratory syndrome (MERS) present an increasingly persistent crisis in many parts of the world. COVID-19 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The angiotensin-converting enzyme 2 (ACE2) is a crucial cellular receptor for SARS-CoV-2 infection. Inhibition of the interaction between SARS-CoV-2 and ACE2 has been proposed as a target for the prevention and treatment of COVID-19. We produced four recombinant plant-derived ACE2 isoforms with or without the mu tailpiece (μ-tp) of immunoglobulin M (IgM) and the KDEL endoplasmic reticulum retention motif in a plant expression system. The plant-derived ACE2 isoforms bound whole SARS-CoV-2 virus and the isolated receptor binding domains of SARS-CoV-2 Alpha, Beta, Gamma, Delta, and Omicron variants. Fusion of μ-tp and KDEL to the ACE2 protein (ACE2 μK) had enhanced binding activity with SARS-CoV-2 in comparison with unmodified ACE2 protein derived from CHO cells. Furthermore, the plant-derived ACE2 μK protein exhibited no cytotoxic effects on Vero E6 cells and effectively inhibited SARS-CoV-2 infection. The efficient and rapid scalability of plant-derived ACE2 μK protein offers potential for the development of preventive and therapeutic agents in the early response to future viral outbreaks.

Production, purification and immunogenicity of Gag virus-like particles carrying SARS-CoV-2 components

The virus-like particle (VLP) platform is a robust inducer of humoral and cellular immune responses; hence, it has been used in vaccine development for several infectious diseases. In the current work, VLPs carrying SARS-CoV-2 Spike (S) protein (Wuhan strain) with an HIV-1 Gag core were produced using suspension HEK 293SF-3F6 cells by transient transfection. The Gag was fused with green fluorescent protein (GFP) for rapid quantification of the VLPs. Five different versions of Gag-Spike VLPs (Gag-S-VLPs) consisting of Gag-S alone or combined with other SARS-CoV-2 components, namely Gag-S-Nucleocapsid (N), Gag-S-Matrix (M), Gag-S-Envelope (E), Gag-S-MEN, along with Gag alone were produced and processed by clarification, nuclease treatment, concentration by tangential flow filtration (TFF) and diafiltration. A pilot mouse study was performed to evaluate the immunogenicity of the Gag-S-VLPs through the measurement of the humoral and/or cellular responses against all the mentioned SARS-CoV-2 components. Antibody response to Spike was observed in all variants. The highest number of Spike-specific IFN-γ + T cells was detected with Gag-S-VLPs. No induction of antigen-specific cellular responses to M, N or E proteins were detected with any of the Gag-S, M, E/or N VLPs tested. Therefore, the Gag-S-VLP, by reason of consistently eliciting strong antigen-specific cellular and antibody responses, was selected for further evaluation. The purification process was improved by replacing the conventional centrifugation by serial microfiltration in the clarification step, followed by Spike-affinity chromatography to get concentrated VLPs with higher purity. Three different doses of Gag-S-VLP in conjunction with two adjuvants (Quil-A or AddaVax) were used to assess the dose-dependent antigen-specific cellular and antibody responses in mice. The Gag-S-VLP adjuvanted with Quil-A resulted in a stronger Spike-specific cellular response compared to that adjuvanted with AddaVax. A strong spike neutralisation activity was observed for all doses, independent of the adjuvant combination.

Protective efficacy of the oral vaccine Tc24:Co1 produced in Schizochytrium sp. against Trypanosoma cruzi infection in a mouse model

Trypanosoma cruzi parasite - causal Chagas disease agent - affects about 7 million people; no vaccine is available, and current medications have not been entirely effective. Multidisciplinary efforts are necessary for developing clinical vaccine prototypes. Thus, this research study aims to assess the expressed and whole-cell administration protection of the oral vaccine prototype Tc24:Co1 using Schizochytrium sp. microalga. High recombinant protein expression yields (675 μg/L) of algal culture were obtained. Additionally, Schizochytrium sp.-Tc24:Co1 resulted stable at 4 °C for up to six months and at 25 °C for three months. After receiving four oral doses of the vaccine, the mice showed a significant humoral immune response and a parasitemia reduction associated with a lack of heart inflammatory damage compared with the unvaccinated controls. The Schizochytrium sp.-Tc24:Co1 vaccine demonstrates to be promising as a prototype for further development showing protective effects against a T. cruzi challenge in a mouse model.

Plant-expressed Zika virus envelope protein elicited protective immunity against the Zika virus in immunocompetent mice

Zika virus infection causes multiple clinical issues, including Guillain-Barré syndrome and neonatal malformation. Vaccination is considered as the only strategy for the prevention of ZIKV-induced clinical issues. This study developed a plant-based recombinant vaccine that transiently expressed the ZIKV envelope protein (ZikaEnv:aghFc) in Nicotiana benthamiana and evaluated the protective immunity afforded by it in immunocompetent mice. ZikaEnv:aghFc induced both humoral and cellular immunity at a low dose (1-5 μg). This immune-inducing potential was enhanced further when adjuvanted CIA09A. In addition, antigen-specific antibodies and neutralizing antibodies were vertically transferred from immunized females to their progeny and afforded both protective immunity to ZIKV and cross-protection to Dengue virus infection. These results suggest that our plant-based ZIKV vaccine provides a safe and efficient protective strategy with a competitive edge.

Integrated antibody and cellular immunity monitoring are required for assessment of the long term protection that will be essential for effective next generation vaccine development

The COVID pandemic exposed the critical role T cells play in initial immunity, the establishment and maintenance of long term protection, and of durable responsiveness against novel viral variants. A growing body of evidence indicates that adding measures of cellular immunity will fill an important knowledge gap in vaccine clinical trials, likely leading to improvements in the effectiveness of the next generation vaccines against current and emerging variants. In depth cellular immune monitoring in Phase II trials, particularly for high risk populations such as the elderly or immune compromised, should result in better understanding of the dynamics and requirements for establishing effective long term protection. Such analyses can result in cellular immunity correlates that can then be deployed in Phase III studies using appropriate, scalable technologies. Measures of cellular immunity are less established than antibodies as correlates of clinical immunity, and some misconceptions persist about cellular immune monitoring usefulness, cost, complexity, feasibility, and scalability. We outline the currently available cellular immunity assays, review their readiness for use in clinical trials, their logistical requirements, and the type of information each assay generates. The objective is to provide a reliable source of information that could be leveraged to develop a rational approach for comprehensive immune monitoring during vaccine development.

Accumulation of colicin M protein and its biological activity in transgenic lettuce and mizuna plants

Food-borne illnesses caused by pathogenic Escherichia coli strains, especially enterohaemorrhagic E. coli (EHEC), are a serious public health problem, as debilitating disease and even death from such food poisonings have been repeatedly reported. Colicin M (ColM), a non-antibiotic antimicrobial protein produced by some strains of E. coli, has shown promising activity in controlling multiple enteropathogenic strains of E. coli and related pathogens. As contaminated green leafy vegetables are a frequent source of pathogenic E. coli infections, we genetically modified (GM) two edible crops, lettuce (Lactuca sativa L.) and mizuna (Brassica rapa subsp. nipposinica var. laciniata), to stably express the ColM gene and assessed the antibacterial activity of tissue extracts from these plants against selected E. coli strains in vitro. Transgenic plants of these species were developed using Agrobacterium-mediated transformation with a vector containing the ColM-coding gene (cma) under the control of the 35S promoter. Western blot analysis of recombinant ColM protein was performed in selected transgenic plants to confirm cma gene expression and quantify ColM accumulation. Extracts of transgenic plants expressing ColM showed significant activity against two major strains of EHEC (O157:H7 and O104:H4) as well as E. coli strains resistant to beta-lactam- and carbapenem-class antibiotics. Importantly, the antibacterial activity persisted in several subsequent generations of transgenic lettuce and mizuna plants that stably expressed the ColM gene. In addition, our results also show that the antibacterial activity of dried (up to 40°C) biomass of transgenic plants remained stable without a decrease for at least three months.

Plant glycoengineering for designing next-generation vaccines and therapeutic proteins

Protein glycosylation has a huge impact on biological processes in all domains of life. The type of glycan present on a recombinant glycoprotein depends on protein intrinsic features and the glycosylation repertoire of the cell type used for expression. Glycoengineering approaches are used to eliminate unwanted glycan modifications and to facilitate the coordinated expression of glycosylation enzymes or whole metabolic pathways to furnish glycans with distinct modifications. The formation of tailored glycans enables structure-function studies and optimization of therapeutic proteins used in different applications. While recombinant proteins or proteins from natural sources can be in vitro glycoengineered using glycosyltransferases or chemoenzymatic synthesis, many approaches use genetic engineering involving the elimination of endogenous genes and introduction of heterologous genes to cell-based production systems. Plant glycoengineering enables the in planta production of recombinant glycoproteins with human or animal-type glycans that resemble natural glycosylation or contain novel glycan structures. This review summarizes key achievements in glycoengineering of plants and highlights current developments aiming to make plants more suitable for the production of a diverse range of recombinant glycoproteins for innovative therapies.

Development and characterization of a plant-derived norovirus-like particle vaccine

BACKGROUND

Norovirus (NoV) is the most common cause of diarrheal episodes globally. Issues with in vitro cultivation systems, genetic variation, and animal models have hindered vaccine development. Plant-derived virus-like particles (VLPs) may address some of these concerns because they are highly immunogenic, can be administered by different routes, and can be rapidly produced to accommodate emerging viral strains.

METHODS

NoV VLPs (NoVLP) composed of the surface viral protein (VP) 1 of the GI and GII genogroups were produced in Nicotiana benthamiana using an Agrobacterium tumefaciens-based recombinant transient expression system. Leaves from infiltrated plants were harvested and NoVLPs were extracted and purified. The safety and immunogenicity of the GII.4 NoVLP, the genotype currently causing most human disease, were subsequently examined in rabbits and mice.

RESULTS

Fifteen GI and GII NoVLPs were successfully expressed in N. benthamiana and were structurally similar to NoV virions, as determined by cryogenic transmission electron microscopy. The NoVLP was well-tolerated, with no local or systemic signs of toxicity in rabbits. Three intramuscular doses of the GII.4 NoVLP adjuvanted with aluminum hydroxide induced robust IgG titers, IgG-secreting cells, histo-blood group antigen blocking titers, and IFNγ-secreting T cells in mice. In addition to circulating antibodies, oral administration of the NoVLP in mice induced significant IgA levels in feces, indicative of a mucosal response.

CONCLUSIONS

The plant-made NoVLP vaccine was safe and immunogenic in mice and rabbits. Multi-modal vaccination, combining oral and intramuscular administration could be considered for future clinical development to maximize systemic and mucosal immune responses.

A mosaic influenza virus-like particles vaccine provides broad humoral and cellular immune responses against influenza A viruses

The development of a universal influenza vaccine to elicit broad immune responses is essential in reducing disease burden and pandemic impact. In this study, the mosaic vaccine design strategy and genetic algorithms were utilized to optimize the seasonal influenza A virus (H1N1, H3N2) hemagglutinin (HA) and neuraminidase (NA) antigens, which also contain most potential T-cell epitopes. These mosaic immunogens were then expressed as virus-like particles (VLPs) using the baculovirus expression system. The immunogenicity and protection effectiveness of the mosaic VLPs were compared to the commercial quadrivalent inactivated influenza vaccine (QIV) in the mice model. Strong cross-reactive antibody responses were observed in mice following two doses of vaccination with the mosaic VLPs, with HI titers higher than 40 in 15 of 16 tested strains as opposed to limited cross HI antibody levels with QIV vaccination. After a single vaccination, mice also show a stronger level of cross-reactive antibody responses than the QIV. The QIV vaccinations only elicited NI antibodies to a small number of vaccine strains, and not even strong NI antibodies to its corresponding vaccine components. In contrast, the mosaic VLPs caused robust NI antibodies to all tested seasonal influenza virus vaccine strains. Here, we demonstrated the mosaic vaccines induces stronger cross-reactive antibodies and robust more T-cell responses compared to the QIV. The mosaic VLPs also provided protection against challenges with ancestral influenza A viruses of both H1 and H3 subtypes. These findings indicated that the mosaic VLPs were a promising strategy for developing a broad influenza vaccine in future.

Translatability scoring in prospective and retrospective COVID drug development cases

BACKGROUND

The ongoing pandemic of severe acute respiratory syndrome coronavirus 2 has led to an enormous surge of clinical research. So far, the speed and success rate of related drug development projects, especially of vaccines, is unprecedented. For the first time, this situation allowed for the opportunistic evaluation of a translatability score, originally proposed in 2009, in a prospective manner.

METHODS

Several vaccines and treatments under development in clinical phase III trials were selected for translational scoring with the translatability score. Six prospective and six retrospective case studies were performed. The scores had to be determined for a fictive date before any results of the phase III trial were reported in any media. Spearman correlation analysis and a Kruskal Wallis test were performed for statistical evaluation.

RESULTS

A significant correlation between the translatability scores and the clinical outcomes in translation was found, as judged on the basis of positive/intermediate/negative endpoint studies or market approval. The Spearman correlation analysis of all cases (r = 0.91, p < 0.001), the prospective cases alone (r = 0.93, p = 0.008), and the retrospective cases alone (r = 0.93, p = 0.008) showed a strong correlation between the score and outcome; R2 demonstrated a score-derived determination of outcomes by 86%.

CONCLUSIONS

The score detects strengths and weaknesses of a given project, resulting in the opportunity of selective amelioration of a project, as well as prospective portfolio risk balancing. Its substantial predictive value that has been demonstrated here for the first time could be of particular interest for biomedical industry (pharmaceutical and device manufacturers), funding agencies, venture capitalists, and researchers in the area. Future evaluations will have to address the generalizability of results obtained in an exceptional pandemic situation, and the potential adaptations of weighing factors/items to particular therapeutic areas.

Chemical and biological conjugation strategies for the development of multivalent protein vaccine nanoparticles

The development of subunit vaccine platforms has been of considerable interest due to their good safety profile and ability to be adapted to new antigens, compared to other vaccine typess. Nevertheless, subunit vaccines often lack sufficient immunogenicity to fully protect against infectious diseases. A wide variety of subunit vaccines have been developed to enhance antigen immunogenicity by increasing antigen multivalency, as well as stability and delivery properties, via presentation of antigens on protein nanoparticles. Increasing multivalency can be an effective approach to provide a potent humoral immune response by more strongly engaging and clustering B cell receptors (BCRs) to induce activation, as well as increased uptake by antigen presenting cells and their subsequent T cell activation. Proper orientation of antigen on protein nanoparticles is also considered a crucial factor for enhanced BCR engagement and subsequent immune responses. Therefore, various strategies have been reported to decorate highly repetitive surfaces of protein nanoparticle scaffolds with multiple copies of antigens, arrange antigens in proper orientation, or combinations thereof. In this review, we describe different chemical bioconjugation methods, approaches for genetic fusion of recombinant antigens, biological affinity tags, and enzymatic conjugation methods to effectively present antigens on the surface of protein nanoparticle vaccine scaffolds.

Production of Plant-Derived Japanese Encephalitis Virus Multi-Epitope Peptide in Nicotiana benthamiana and Immunological Response in Mice

The current production of the Japanese encephalitis virus (JEV) vaccine is based on animal cells, where various risk factors for human health should be resolved. This study used a transient expression system to express the chimeric protein composed of antigenic epitopes from the JEV envelope (E) protein in Nicotiana benthamiana. JEV multi-epitope peptide (MEP) sequences fused with FLAG-tag or 6× His-tag at the C- or N-terminus for the purification were introduced into plant expression vectors and used for transient expression. Among the constructs, vector pSK480, which expresses MEP fused with a FLAG-tag at the C-terminus, showed the highest level of expression and yield in purification. Optimization of transient expression procedures further improved the target protein yield. The purified MEP protein was applied to an ICR mouse and successfully induced an antibody against JEV, which demonstrates the potential of the plant-produced JEV MEP as an alternative vaccine candidate.

The Re-Emergence of Hepatitis E Virus in Europe and Vaccine Development

Hepatitis E virus (HEV) is one of the leading causes of acute viral hepatitis. Transmission of HEV mainly occurs via the fecal-oral route (ingesting contaminated water or food) or by contact with infected animals and their raw meat products. Some animals, such as pigs, wild boars, sheep, goats, rabbits, camels, rats, etc., are natural reservoirs of HEV, which places people in close contact with them at increased risk of HEV disease. Although hepatitis E is a self-limiting infection, it could also lead to severe illness, particularly among pregnant women, or chronic infection in immunocompromised people. A growing number of studies point out that HEV can be classified as a re-emerging virus in developed countries. Preventative efforts are needed to reduce the incidence of acute and chronic hepatitis E in non-endemic and endemic countries. There is a recombinant HEV vaccine, but it is approved for use and commercially available only in China and Pakistan. However, further studies are needed to demonstrate the necessity of applying a preventive vaccine and to create conditions for reducing the spread of HEV. This review emphasizes the hepatitis E virus and its importance for public health in Europe, the methods of virus transmission and treatment, and summarizes the latest studies on HEV vaccine development.

The position of Spy Tag/Catcher system in hepatitis B core protein particles affects the immunogenicity and stability of the synthetic vaccine

Presenting exogenous antigens on virus-like particles (VLPs) through "plug-and-display" decoration strategies based on SpyTag/SpyCatcher isopeptide bonding have emerged as attractive technology for vaccine synthesis. However, whether the position of ligation site in VLPs will impose effects on immunogenicity and physiochemical properties of the synthetic vaccine remains rarely investigated. Here in the present work, the well-established hepatitis B core (HBc) protein was used as chassis to construct dual-antigen influenza nanovaccines, with the conserved epitope peptides derived from extracellular domain of matrix protein M2 (M2e) and hemagglutinin (HA) as target antigens. The M2e antigen was genetically fused to the HBc in the MIR region, together with the SpyTag peptide, which was fused either in the MIR region or at the N-terminal of the protein, so that a recombinant HA antigen (rHA) linked to SpyCatcher can be displayed on it, at two different localizations. Both synthetic nanovaccines showed ability in inducing strong M2e and rHA-specific antibodies and cellular immunogenicity; nevertheless, the one in which rHA was conjugated by N-terminal Tag ligation, was superior to another one synthesized by linking the rHA to MIR region SpyTagged-HBc in all aspects, including higher antigen-specific immunogenicity responses, lower anti-HBc carrier antibody, as well as better dispersion stability. Surface charge and hydrophobicity properties of the two synthetic nanovaccines were analyzed, results revealed that linking the rHA to MIR region SpyTagged-HBc lead to more significant and disadvantageous alteration in physiochemical properties of the HBc chassis. This study will expand our knowledge on "plug-and-display" decoration strategies and provide helpful guidance for the rational design of HBc-VLPs based modular vaccines by using SpyTag/Catcher synthesis.

Application of Traditional Vaccine Development Strategies to SARS-CoV-2

Over the past 150 years, vaccines have revolutionized the relationship between people and disease. During the COVID-19 pandemic, technologies such as mRNA vaccines have received attention due to their novelty and successes. However, more traditional vaccine development platforms have also yielded important tools in the worldwide fight against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A variety of approaches have been used to develop COVID-19 vaccines that are now authorized for use in countries around the world. In this review, we highlight strategies that focus on the viral capsid and outwards, rather than on the nucleic acids inside. These approaches fall into two broad categories: whole-virus vaccines and subunit vaccines. Whole-virus vaccines use the virus itself, in either an inactivated or an attenuated state. Subunit vaccines contain instead an isolated, immunogenic component of the virus. Here, we highlight vaccine candidates that apply these approaches against SARS-CoV-2 in different ways. In a companion article (H. M. Rando, R. Lordan, L. Kolla, E. Sell, et al., mSystems 8:e00928-22, 2023, https://doi.org/10.1128/mSystems.00928-22), we review the more recent and novel development of nucleic acid-based vaccine technologies. We further consider the role that these COVID-19 vaccine development programs have played in prophylaxis at the global scale. Well-established vaccine technologies have proved especially important to making vaccines accessible in low- and middle-income countries. Vaccine development programs that use established platforms have been undertaken in a much wider range of countries than those using nucleic acid-based technologies, which have been led by wealthy Western countries. Therefore, these vaccine platforms, though less novel from a biotechnological standpoint, have proven to be extremely important to the management of SARS-CoV-2. IMPORTANCE The development, production, and distribution of vaccines is imperative to saving lives, preventing illness, and reducing the economic and social burdens caused by the COVID-19 pandemic. Vaccines that use cutting-edge biotechnology have played an important role in mitigating the effects of SARS-CoV-2. However, more traditional methods of vaccine development that were refined throughout the 20th century have been especially critical to increasing vaccine access worldwide. Effective deployment is necessary to reducing the susceptibility of the world's population, which is especially important in light of emerging variants. In this review, we discuss the safety, immunogenicity, and distribution of vaccines developed using established technologies. In a separate review, we describe the vaccines developed using nucleic acid-based vaccine platforms. From the current literature, it is clear that the well-established vaccine technologies are also highly effective against SARS-CoV-2 and are being used to address the challenges of COVID-19 globally, including in low- and middle-income countries. This worldwide approach is critical for reducing the devastating impact of SARS-CoV-2.

A plant-produced SARS-CoV-2 spike protein elicits heterologous immunity in hamsters

Molecular farming of vaccines has been heralded as a cheap, safe and scalable production platform. In reality, however, differences in the plant biosynthetic machinery, compared to mammalian cells, can complicate the production of viral glycoproteins. Remodelling the secretory pathway presents an opportunity to support key post-translational modifications, and to tailor aspects of glycosylation and glycosylation-directed folding. In this study, we applied an integrated host and glyco-engineering approach, NXS/T Generation™, to produce a SARS-CoV-2 prefusion spike trimer in Nicotiana benthamiana as a model antigen from an emerging virus. The size exclusion-purified protein exhibited a characteristic prefusion structure when viewed by transmission electron microscopy, and this was indistinguishable from the equivalent mammalian cell-produced antigen. The plant-produced protein was decorated with under-processed oligomannose N-glycans and exhibited a site occupancy that was comparable to the equivalent protein produced in mammalian cell culture. Complex-type glycans were almost entirely absent from the plant-derived material, which contrasted against the predominantly mature, complex glycans that were observed on the mammalian cell culture-derived protein. The plant-derived antigen elicited neutralizing antibodies against both the matched Wuhan and heterologous Delta SARS-CoV-2 variants in immunized hamsters, although titres were lower than those induced by the comparator mammalian antigen. Animals vaccinated with the plant-derived antigen exhibited reduced viral loads following challenge, as well as significant protection from SARS-CoV-2 disease as evidenced by reduced lung pathology, lower viral loads and protection from weight loss. Nonetheless, animals immunized with the mammalian cell-culture-derived protein were better protected in this challenge model suggesting that more faithfully reproducing the native glycoprotein structure and associated glycosylation of the antigen may be desirable.

Facilitating viral vector movement enhances heterologous protein production in an established plant system

Molecular farming technology using transiently transformed Nicotiana plants offers an economical approach to the pharmaceutical industry to produce an array of protein targets including vaccine antigens and therapeutics. It can serve as a desirable alternative approach for those proteins that are challenging or too costly to produce in large quantities using other heterologous protein expression systems. However, since cost metrics are such a critical factor in selecting a production host, any system-wide modifications that can increase recombinant protein yields are key to further improving the platform and making it applicable for a wider range of target molecules. Here, we report on the development of a new approach to improve target accumulation in an established plant-based expression system that utilizes viral-based vectors to mediate transient expression in Nicotiana benthamiana. We show that by engineering the host plant to support viral vectors to spread more effectively between host cells through plasmodesmata, protein target accumulation can be increased by up to approximately 60%.

Regional characteristics of influenza seasonality patterns in mainland China, 2005-2017: a statistical modeling study

OBJECTIVES

To quantify the seasonal and antigenic characteristics of influenza to help understand influenza activity and inform vaccine recommendations.

METHODS

We employed a generalized linear model with harmonic terms to quantify the seasonal pattern of influenza in China from 2005-2017, including amplitude (circulatory intensity), semiannual periodicity (given two peaks a year), annual peak time, and epidemic duration. The antigenic differences were distinguished as antigenic similarity between 2009 and 2020. We categorized regions above 33° N, between 27° N and 33° N, and below 27° N as the north, central, and south regions, respectively.

RESULTS

We estimated that the amplitude in the north region (median: 0.019, 95% CI: 0.018-0.021) was significantly higher than that in the central region (median: 0.011, 95% CI: 0.01-0.012, P <0.001) and south region (median: 0.008, 95% CI: 0.007-0.008, P <0.001) for influenza A virus subtype H3N2 (A/H3N2). The A/H3N2 in the central region had a semiannual periodicity (median: 0.548, 95% CI: 0.517-0.577), while no semiannual pattern was found in other regions or subtypes/lineages. The antigenic similarity was low (below 50% in the 2009-2010, 2014-2015, 2016-2018, and 2019-2020 seasons) for A/H3N2.

CONCLUSION

Our study depicted the seasonal pattern differences and antigenic differences of influenza in China, which provides information for vaccination strategies.

Immunogenicity and efficacy of recombinant subunit SARS-CoV-2 vaccine candidate in the Syrian hamster model

SARS-CoV-2 causes devastating impact on the human population and has become a major public health concern. The frequent emergence of SARS-CoV-2 variants of concern urges the development of safe and efficacious vaccine against SARS-CoV-2 variants. We developed a candidate vaccine Baiya SARS-CoV-2 Vax 1, based on SARS-CoV-2 receptor-binding domain (RBD) by fusing with the Fc region of human IgG. The RBD-Fc fusion was produced in Nicotiana benthamiana. Previously, we reported that this plant-produced vaccine is effective in inducing immune response in both mice and non-human primates. Here, the efficacy of our vaccine candidate was tested in Syrian hamster challenge model. Hamsters immunized with two intramuscular doses of Baiya SARS-CoV-2 Vax 1 induced neutralizing antibodies against SARS-CoV-2 and protected from SARS-CoV-2 challenge with reduced viral load in the lungs. These preliminary results demonstrate the ability of plant-produced subunit vaccine Baiya SARS-CoV-2 Vax 1 to provide protection against SARS-CoV-2 infection in hamsters.

Plants as Biofactories for Therapeutic Proteins and Antiviral Compounds to Combat COVID-19

The outbreak of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) had a profound impact on the world's health and economy. Although the end of the pandemic may come in 2023, it is generally believed that the virus will not be completely eradicated. Most likely, the disease will become an endemicity. The rapid development of vaccines of different types (mRNA, subunit protein, inactivated virus, etc.) and some other antiviral drugs (Remdesivir, Olumiant, Paxlovid, etc.) has provided effectiveness in reducing COVID-19's impact worldwide. However, the circulating SARS-CoV-2 virus has been constantly mutating with the emergence of multiple variants, which makes control of COVID-19 difficult. There is still a pressing need for developing more effective antiviral drugs to fight against the disease. Plants have provided a promising production platform for both bioactive chemical compounds (small molecules) and recombinant therapeutics (big molecules). Plants naturally produce a diverse range of bioactive compounds as secondary metabolites, such as alkaloids, terpenoids/terpenes and polyphenols, which are a rich source of countless antiviral compounds. Plants can also be genetically engineered to produce valuable recombinant therapeutics. This molecular farming in plants has an unprecedented opportunity for developing vaccines, antibodies, and other biologics for pandemic diseases because of its potential advantages, such as low cost, safety, and high production volume. This review summarizes the latest advancements in plant-derived drugs used to combat COVID-19 and discusses the prospects and challenges of the plant-based production platform for antiviral agents.

Determination of the synergistic anti-influenza effect of Huangqin Su tablet and Oseltamivir and investigation of mechanism of the tablet based on gut microbiota and network pharmacology

Huangqin Su (HQS) tablet is mainly composed of baicalein which has been evaluated for its ability to inhibit influenza. The present study aimed to investigate the effect of HQS and oseltamivir phosphate (OS) (single or combination therapy) on influenza-induced acute pneumonia in male and female ICR mice. The regulatory effect of HQS on gut microbiota was also studied by using 16 s rDNA sequencing, and the targets and mechanisms of HQS against influenza were comprehensively analyzed by network pharmacology. Pharmacodynamic results, including lung index and pathological changes, showed that HQS exhibited significant anti-influenza efficacy and could improve the efficacy of low-dose OS (P < 0.05 and P < 0.01, respectively). The results of 16 s rDNA sequencing revealed that HQS modulated the gut microbiota and remarkably enriched the abundance of Lactobacillus. The findings of network pharmacology research suggested that the anti-influenza mechanism of HQS was related to TLRs, MAPK, and other signal transduction pathways. Taken together, this study identified the possibility of the combined use of HQS and OS and demonstrated the role of HQS in modulating the gut microbiota of mice against influenza. Network pharmacology studies also suggested that the anti-influenza effect of HQS was related to TLRs, MAPK, TNF, and other signaling pathways.

The race toward a universal influenza vaccine: Front runners and the future directions

Influenza virus is the pathogen of influenza (flu) and millions of people suffer from the infection worldwide, posing a significant health risk. The current influenza vaccines induce neutralizing antibodies against hemagglutinin (HA) to achieve strain-specific neutralization. The effectiveness of seasonal vaccines is usually low and unpredictable because of the antigenic variation and genetic plasticity of viruses, as well as the interference of preexisting immunity. A universal influenza vaccine is urgently needed to prevent a wide variety of influenza viruses. Nevertheless, reaching this difficult optimal goal requires a step-by-step approach. Innovative strategies and vaccine platforms are being developed in order to generate robust cross-protective immunity. In this review, we summarize candidate influenza vaccines that meet two criteria: first, they are designed to provide protection against multiple influenza viruses; second, they had passed regulatory evaluations and have entered various stages of clinical trials. We discuss these vaccine candidates based on the different vaccine-production platforms, with the focus on antigen selection, design, adjuvants, immunomodulators, and routes of vaccine delivery in the development of universal influenza vaccines.

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.

Application of Traditional Vaccine Development Strategies to SARS-CoV-2

Over the past 150 years, vaccines have revolutionized the relationship between people and disease. During the COVID-19 pandemic, technologies such as mRNA vaccines have received attention due to their novelty and successes. However, more traditional vaccine development platforms have also yielded important tools in the worldwide fight against the SARS-CoV-2 virus. A variety of approaches have been used to develop COVID-19 vaccines that are now authorized for use in countries around the world. In this review, we highlight strategies that focus on the viral capsid and outwards, rather than on the nucleic acids inside. These approaches fall into two broad categories: whole-virus vaccines and subunit vaccines. Whole-virus vaccines use the virus itself, either in an inactivated or attenuated state. Subunit vaccines contain instead an isolated, immunogenic component of the virus. Here, we highlight vaccine candidates that apply these approaches against SARS-CoV-2 in different ways. In a companion manuscript, we review the more recent and novel development of nucleic-acid based vaccine technologies. We further consider the role that these COVID-19 vaccine development programs have played in prophylaxis at the global scale. Well-established vaccine technologies have proved especially important to making vaccines accessible in low- and middle-income countries. Vaccine development programs that use established platforms have been undertaken in a much wider range of countries than those using nucleic-acid-based technologies, which have been led by wealthy Western countries. Therefore, these vaccine platforms, though less novel from a biotechnological standpoint, have proven to be extremely important to the management of SARS-CoV-2.

The Plant Viruses and Molecular Farming: How Beneficial They Might Be for Human and Animal Health?

Plant viruses have traditionally been studied as pathogens in the context of understanding the molecular and cellular mechanisms of a particular disease affecting crops. In recent years, viruses have emerged as a new alternative for producing biological nanomaterials and chimeric vaccines. Plant viruses were also used to generate highly efficient expression vectors, revolutionizing plant molecular farming (PMF). Several biological products, including recombinant vaccines, monoclonal antibodies, diagnostic reagents, and other pharmaceutical products produced in plants, have passed their clinical trials and are in their market implementation stage. PMF offers opportunities for fast, adaptive, and low-cost technology to meet ever-growing and critical global health needs. In this review, we summarized the advancements in the virus-like particles-based (VLPs-based) nanotechnologies and the role they played in the production of advanced vaccines, drugs, diagnostic bio-nanomaterials, and other bioactive cargos. We also highlighted various applications and advantages plant-produced vaccines have and their relevance for treating human and animal illnesses. Furthermore, we summarized the plant-based biologics that have passed through clinical trials, the unique challenges they faced, and the challenges they will face to qualify, become available, and succeed on the market.

Tobacco-Based Vaccines, Hopes, and Concerns: A Systematic Review

Emerging infectious diseases have vigorously devastated the global economy and health sector; cost-effective plant-based vaccines (PBV) can be the potential solution to withstand the current health economic crisis. The prominent role of tobacco as an efficient expression system for PBV has been well-established for decades, through this review we highlight the importance of tobacco-based vaccines (TBV) against evolving infectious diseases in humans. Studies focusing on the use of TBV for human infectious diseases were searched in PubMed, Google Scholar, and science direct from 1995 to 2021 using the keywords Tobacco-based vaccines OR transgenic tobacco OR Nicotiana benthamiana vaccines AND Infectious diseases or communicable diseases. We carried out a critical review of the articles and studies that fulfilled the eligibility criteria and were included in this review. Of 976 studies identified, only 63 studies fulfilling the eligibility criteria were included, which focused on either the in vitro, in vivo, or clinical studies on TBV for human infectious diseases. Around 43 in vitro studies of 23 different infectious pathogens expressed in tobacco-based systems were identified and 23 in vivo analysis studies were recognized to check the immunogenicity of vaccine candidates while only 10 of these were subjected to clinical trials. Viral infectious pathogens were studied more than bacterial pathogens. From our review, it was evident that TBV can be an effective health strategy to combat the emerging viral infectious diseases which are very difficult to manage with the current health facilities. The timely administration of cost-effective TBV can prevent the outburst of viral infections, thereby can protect the global healthcare system to a greater extent.

High-Yield Production of Chimeric Hepatitis E Virus-Like Particles Bearing the M2e Influenza Epitope and Receptor Binding Domain of SARS-CoV-2 in Plants Using Viral Vectors

Capsid protein of Hepatitis E virus (HEV) is capable of self-assembly into virus-like particles (VLPs) when expressed in Nicotiana benthamiana plants. Such VLPs could be used as carriers of antigens for vaccine development. In this study, we obtained VLPs based on truncated coat protein of HEV bearing the M2e peptide of Influenza A virus or receptor-binding domain of SARS-CoV-2 spike glycoprotein (RBD). We optimized the immunogenic epitopes' presentation by inserting them into the protruding domain of HEV ORF2 at position Tyr485. The fusion proteins were expressed in Nicotiana benthamiana plants using self-replicating potato virus X (PVX)-based vector. The fusion protein HEV/M2, targeted to the cytosol, was expressed at the level of about 300-400 μg per gram of fresh leaf tissue and appeared to be soluble. The fusion protein was purified using metal affinity chromatography under native conditions with the final yield about 200 μg per gram of fresh leaf tissue. The fusion protein HEV/RBD, targeted to the endoplasmic reticulum, was expressed at about 80-100 μg per gram of fresh leaf tissue; the yield after purification was up to 20 μg per gram of fresh leaf tissue. The recombinant proteins HEV/M2 and HEV/RBD formed nanosized virus-like particles that could be recognized by antibodies against inserted epitopes. The ELISA assay showed that antibodies of COVID-19 patients can bind plant-produced HEV/RBD virus-like particles. This study shows that HEV capsid protein is a promising carrier for presentation of foreign antigen.

In Vivo Fate of Cowpea Mosaic Virus In Situ Vaccine: Biodistribution and Clearance

Cowpea mosaic virus (CPMV) is a nucleoprotein nanoparticle that functions as a highly potent immunomodulator when administered intratumorally and is used as an in situ vaccine. CPMV in situ vaccination remodels the tumor microenvironment and primes a highly potent, systemic, and durable antitumor immune response against the treated and untreated, distant metastatic sites (abscopal effect). Potent efficacy was demonstrated in multiple tumor mouse models and, most importantly, in canine cancer patients with spontaneous tumors. Data indicate that presence of anti-CPMV antibodies are not neutralizing and that in fact opsonization leads to enhanced efficacy. Plant viruses are part of the food chain, but to date, there is no information on human exposure to CPMV. Therefore, patient sera were tested for the presence of immunoglobulins against CPMV, and indeed, >50% of deidentified patient samples tested positive for CPMV antibodies. To get a broader sense of plant virus exposure and immunogenicity in humans, we also tested sera for antibodies against tobacco mosaic virus (>90% patients tested positive), potato virus X (<20% patients tested positive), and cowpea chlorotic mottle virus (no antibodies were detected). Further, patient sera were analyzed for the presence of antibodies against the coliphage Qβ, a platform technology currently undergoing clinical trials for in situ vaccination; we found that 60% of patients present with anti-Qβ antibodies. Thus, data indicate human exposure to CPMV and other plant viruses and phages. Next, we thought to address agronomical safety; i.e., we examined the fate of CPMV after intratumoral treatment and oral gavage (to mimic consumption by food). Because live CPMV is used, an important question is whether there is any evidence of shedding of infectious particles from mice or patients. CPMV is noninfectious toward mammals; however, it is infectious toward plants including black-eyed peas and other legumes. Biodistribution data in tumor-bearing and healthy mice indicate little leaching from tumors and clearance via the reticuloendothelial system followed by biliary excretion. While there was evidence of shedding of RNA in stool, there was no evidence of infectious particles when plants were challenged with stool extracts, thus indicating agronomical safety. Together these data aid the translational development of CPMV as a drug candidate for cancer immunotherapy.

Plant-produced recombinant cytokines IL-37b and IL-38 modulate inflammatory response from stimulated human PBMCs

Affordable therapeutics are vitally needed for humans worldwide. Plant-based production of recombinant proteins can potentially enhance, back-up, or even substitute for the manufacturing capacity of the conventional, fermenter-based technologies. We plastome-engineered a tobacco cultivar to express high levels of two "plantakines" - recombinant human cytokines, interleukins IL-37b and IL-38, and confirmed their native conformation and folding. Assessment of their biological functionality was performed ex vivo by analyzing the effects exerted by the plantakines on levels of 11 cytokines secreted from human peripheral blood mononuclear cells (PBMCs) challenged with an inflammatory agent. Application of the plant-produced IL-37b and IL-38 in PBMCs stimulated with Lipopolysaccharide or Phytohaemagglutinin resulted in significant, and in particular cases-dose-dependent modulation of pro-inflammatory cytokines secretion, showing attenuation in two-thirds of significant level modulations observed. Plantakine treatments that increased inflammatory responses were associated with the higher dosage. Our results demonstrate feasibility of manufacturing functional recombinant human proteins using scalable, cost-effective and eco-friendly plant-based bioreactors.

Plant-based expression platforms to produce high-value metabolites and proteins

Plant-based heterologous expression systems can be leveraged to produce high-value therapeutics, industrially important proteins, metabolites, and bioproducts. The production can be scaled up, free from pathogen contamination, and offer post-translational modifications to synthesize complex proteins. With advancements in molecular techniques, transgenics, CRISPR/Cas9 system, plant cell, tissue, and organ culture, significant progress has been made to increase the expression of recombinant proteins and important metabolites in plants. Methods are also available to stabilize RNA transcripts, optimize protein translation, engineer proteins for their stability, and target proteins to subcellular locations best suited for their accumulation. This mini-review focuses on recent advancements to enhance the production of high-value metabolites and proteins necessary for therapeutic applications using plants as bio-factories.

Impact of glycoengineering and antidrug antibodies on the anticancer activity of a plant-made lectin-Fc fusion protein

Plants are an efficient production platform for manufacturing glycoengineered monoclonal antibodies and antibody-like molecules. Avaren-Fc (AvFc) is a lectin-Fc fusion protein or lectibody produced in Nicotiana benthamiana, which selectively recognizes cancer-associated high-mannose glycans. In this study, we report the generation of a glycovariant of AvFc that is devoid of plant glycans, including the core α1,3-fucose and β1,2-xylose residues. The successful removal of these glycans was confirmed by glycan analysis using HPLC. This variant, AvFc^ΔXF , has significantly higher affinity for Fc gamma receptors and induces higher levels of luciferase expression in an antibody-dependent cell-mediated cytotoxicity (ADCC) reporter assay against B16F10 murine melanoma cells without inducing apoptosis or inhibiting proliferation. In the B16F10 flank tumour mouse model, we found that systemic administration of AvFc^ΔXF , but not an aglycosylated AvFc variant lacking affinity for Fc receptors, significantly delayed the growth of tumours, suggesting that Fc-mediated effector functions were integral. AvFc^ΔXF treatment also significantly reduced lung metastasis of B16F10 upon intravenous challenge whereas a sugar-binding-deficient mutant failed to show efficacy. Lastly, we determined the impact of antidrug antibodies (ADAs) on drug activity in vivo by pretreating animals with AvFc^ΔXF before implanting tumours. Despite a significant ADA response induced by the pretreatment, we found that the activity of AvFc^ΔXF was unaffected by the presence of these antibodies. These results demonstrate that glycoengineering is a powerful strategy to enhance AvFc's antitumor activity.

Transient Expression of Flavivirus Structural Proteins in Nicotiana benthamiana

Flaviviruses are a threat to public health and can cause major disease outbreaks. Tick-borne encephalitis (TBE) is caused by a flavivirus, and it is one of the most important causes of viral encephalitis in Europe and is on the rise in Sweden. As there is no antiviral treatment available, vaccination remains the best protective measure against TBE. Currently available TBE vaccines are based on formalin-inactivated virus produced in cell culture. These vaccines must be delivered by intramuscular injection, have a burdensome immunization schedule, and may exhibit vaccine failure in certain populations. This project aimed to develop an edible TBE vaccine to trigger a stronger immune response through oral delivery of viral antigens to mucosal surfaces. We demonstrated successful expression and post-translational processing of flavivirus structural proteins which then self-assembled to form virus-like particles in Nicotiana benthamiana. We performed oral toxicity tests in mice using various plant species as potential bioreactors and evaluated the immunogenicity of the resulting edible vaccine candidate. Mice immunized with the edible vaccine candidate did not survive challenge with TBE virus. Interestingly, immunization of female mice with a commercial TBE vaccine can protect their offspring against TBE virus infection.

Recombinant vaccines in 2022: a perspective from the cell factory

The last big outbreaks of Ebola fever in Africa, the thousands of avian influenza outbreaks across Europe, Asia, North America and Africa, the emergence of monkeypox virus in Europe and specially the COVID-19 pandemics have globally stressed the need for efficient, cost-effective vaccines against infectious diseases. Ideally, they should be based on transversal technologies of wide applicability. In this context, and pushed by the above-mentioned epidemiological needs, new and highly sophisticated DNA-or RNA-based vaccination strategies have been recently developed and applied at large-scale. Being very promising and effective, they still need to be assessed regarding the level of conferred long-term protection. Despite these fast-developing approaches, subunit vaccines, based on recombinant proteins obtained by conventional genetic engineering, still show a wide spectrum of interesting potentialities and an important margin for further development. In the 80’s, the first vaccination attempts with recombinant vaccines consisted in single structural proteins from viral pathogens, administered as soluble plain versions. In contrast, more complex formulations of recombinant antigens with particular geometries are progressively generated and explored in an attempt to mimic the multifaceted set of stimuli offered to the immune system by replicating pathogens. The diversity of recombinant antimicrobial vaccines and vaccine prototypes is revised here considering the cell factory types, through relevant examples of prototypes under development as well as already approved products.

Three methods for inoculation of viral vectors into plants

Agriculture is facing new challenges, with global warming modifying the survival chances for crops, and new pests on the horizon. To keep up with these challenges, gene delivery provides tools to increase crop yields. On the other hand, gene delivery also opens the door for molecular farming of pharmaceuticals in plants. However, towards increased food production and scalable molecular farming, there remain technical difficulties and regulatory hurdles to overcome. The industry-standard is transformation of plants via Agrobacterium tumefaciens, but this method is limited to certain plants, requires set up of plant growth facilities and fermentation of bacteria, and introduces lipopolysaccharides contaminants into the system. Therefore, alternate methods are needed. Mechanical inoculation and spray methods have already been discussed in the literature - and here, we compare these methods with a newly introduced petiole injection technique. Because our interest lies in the development of plant viruses as immunotherapies targeting human health as well as gene delivery vectors for agriculture applications, we turned toward tobacco mosaic virus as a model system. We studied the effectiveness of three inoculation techniques: mechanical inoculation, Silwet-77 foliar spray and petiole injections. The foliar spray method was optimized, and we used 0.03% Silwet L-77 to induce infection using either TMV or a lysine-added mutant TMV-Lys. We developed a method using a needle-laden syringe to target and inject the plant virus directly into the vasculature of the plant - we tested injection into the stem and petiole. Stem inoculation resulted in toxicity, but the petiole injection technique was established as a viable strategy. TMV and TMV-Lys were purified from single plants and pooled leaf samples - overall there was little variation between the techniques, as measured by TMV or TMV-Lys yields, highlighting the feasibility of the syringe injection technique to produce virus nanoparticles. There was variation between yields from preparation to preparation with mechanical, spray and syringe inoculation yielding 40-141 mg, 36-56 mg, 18-56 mg TMV per 100 grams of leaves. Similar yields were obtained using TMV-Lys, with 24-38 mg, 17-28, 7-36 mg TMV-Lys per 100 grams of leaves for mechanical, spray and syringe inoculation, respectively. Each method has its advantages: spray inoculation is highly scalable and therefore may find application for farming, the syringe inoculation could provide a clean, aseptic, and controlled approach for molecular farming of pharmaceuticals under good manufacturing protocols (GMP) and would even be applicable for gene delivery to plants in space.

Quadrivalent Vaccines for the Immunization of Adults against Influenza: A Systematic Review of Randomized Controlled Trials

Vaccination is the most effective intervention to prevent influenza. Adults at risk of complications are among the targets of the vaccination campaigns and can be vaccinated with different types of quadrivalent influenza vaccines (QIVs). In the light of assessing the relative immunogenicity and efficacy of different QIVs, a systematic review was performed. Randomized controlled trials conducted in adults aged 18–64 years until 30 March 2021 were searched through three databases (Medline, Cochrane Library and Scopus). Twenty-four RCTs were eventually included. After data extraction, a network meta-analysis was not applicable due to the lack of common comparators. However, in the presence of at least two studies, single meta-analyses were performed to evaluate immunogenicity and efficacy; on the contrary, data from single studies were considered. Seroconversion rate for H1N1 was higher for standard QIVs, while for the remaining strains it was higher for low-dose adjuvanted QIVs. For seroprotection rate, the recombinant vaccine recorded the highest values for H3N2, while for the other strains, the cell-based QIVs achieved better results. In general, standard and cell-based QIVs showed an overall good immunogenicity profile. Nevertheless, as a relative comparative analysis was not possible, further research would be deserved.

Preclinical evaluation of a plant-derived SARS-CoV-2 subunit vaccine: Protective efficacy, immunogenicity, safety, and toxicity

Coronavirus disease 2019 (COVID-19) is an acute respiratory illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The prevention of SARS-CoV-2 transmission has become a global priority. Previously, we showed that a protein subunit vaccine that was developed based on the fusion of the SARS-CoV-2 receptor-binding domain (RBD) to the Fc portion of human IgG1 (RBD-Fc), produced in Nicotiana benthamiana, and adjuvanted with alum, namely, Baiya SARS-CoV-2 Vax 1, induced potent immunological responses in both mice and cynomolgus monkeys. Hence, this study evaluated the protective efficacy, safety, and toxicity of Baiya SARS-CoV-2 Vax 1 in K18-hACE2 mice, monkeys and Wistar rats. Two doses of vaccine were administered three weeks apart on Days 0 and 21. The administration of the vaccine to K18-hACE2 mice reduced viral loads in the lungs and brains of the vaccinated animals and protected the mice against challenge with SARS-CoV-2. In monkeys, the results of safety pharmacology tests, general clinical observations, and a core battery of studies of three vital systems, namely, the central nervous, cardiovascular, and respiratory systems, did not reveal any safety concerns. The toxicology study of the vaccine in rats showed no vaccine-related pathological changes, and all the animals remained healthy under the conditions of this study. Furthermore, the vaccine did not cause any abnormal toxicity in rats and was clinically tolerated even at the highest tested concentration. In addition, general health status, body temperature, local toxicity at the administration site, hematology, and blood chemistry parameters were also monitored. Overall, this work presents the results of the first systematic study of the safety profile of a plant-derived vaccine, Baiya SARS-CoV-2 Vax 1; this approach can be considered a viable strategy for the development of vaccines against COVID-19.

Nanoparticle- and Microparticle-Based Vaccines against Orbiviruses of Veterinary Importance

Bluetongue virus (BTV) and African horse sickness virus (AHSV) are widespread arboviruses that cause important economic losses in the livestock and equine industries, respectively. In addition to these, another arthropod-transmitted orbivirus known as epizootic hemorrhagic disease virus (EHDV) entails a major threat as there is a conducive landscape that nurtures its emergence in non-endemic countries. To date, only vaccinations with live attenuated or inactivated vaccines permit the control of these three viral diseases, although important drawbacks, e.g., low safety profile and effectiveness, and lack of DIVA (differentiation of infected from vaccinated animals) properties, constrain their usage as prophylactic measures. Moreover, a substantial number of serotypes of BTV, AHSV and EHDV have been described, with poor induction of cross-protective immune responses among serotypes. In the context of next-generation vaccine development, antigen delivery systems based on nano- or microparticles have gathered significant attention during the last few decades. A diversity of technologies, such as virus-like particles or self-assembled protein complexes, have been implemented for vaccine design against these viruses. In this work, we offer a comprehensive review of the nano- and microparticulated vaccine candidates against these three relevant orbiviruses. Additionally, we also review an innovative technology for antigen delivery based on the avian reovirus nonstructural protein muNS and we explore the prospective functionality of the nonstructural protein NS1 nanotubules as a BTV-based delivery platform.

Plant-Derived Human Vaccines: Recent Developments

The idea of producing vaccines in plants originated in the late 1980s. Initially, it was contemplated that this notion could facilitate the concept of edible vaccines, making them more cost effective and easily accessible. Initial studies on edible vaccines focussed on the use of a variety of different transgenic plant host species for the production of vaccine antigens. However, adequate expression levels of antigens, the difficulties predicted with administration of consistent doses, and regulatory rules required for growth of transgenic plants gave way to the development of vaccine candidates that could be purified and administered parenterally. The field has subsequently advanced with improved expression techniques including a shift from using transgenic to transient expression of antigens, refinement of purification protocols, a deeper understanding of the biological processes and a wealth of evidence of immunogenicity and efficacy of plant-produced vaccine candidates, all contributing to the successful practice of what is now known as biopharming or plant molecular farming. The establishment of this technology has resulted in the development of many different types of vaccine candidates including subunit vaccines and various different types of nanoparticle vaccines targeting a wide variety of bacterial and viral diseases. This has brought further acceptance of plants as a suitable platform for vaccine production and in this review, we discuss the most recent advances in the production of vaccines in plants for human use.

Broad neutralization against SARS-CoV-2 variants induced by ancestral and B.1.351 AS03-Adjuvanted recombinant Plant-Derived Virus-Like particle vaccines

Since 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection resulting in the coronavirus disease 2019 (COVID-19) has afflicted hundreds of millions of people in a worldwide pandemic. Several safe and effective COVID-19 vaccines are now available. However, the rapid emergence of variants and risk of viral escape from vaccine-induced immunity emphasize the need to develop broadly protective vaccines. A recombinant plant-derived virus-like particle vaccine for the ancestral COVID-19 (CoVLP) recently authorized by Canadian Health Authorities and a modified CoVLP.B1351 targeting the B.1.351 variant (both formulated with the adjuvant AS03) were assessed in homologous and heterologous prime-boost regimen in mice. Both strategies induced strong and broadly cross-reactive neutralizing antibody (NAb) responses against several Variants of Concern (VOCs), including B.1.351/Beta, B.1.1.7/Alpha, P.1/Gamma, B.1.617.2/Delta and B.1.1.529/Omicron strains. The neutralizing antibody (NAb) response was robust with both primary vaccination strategies and tended to be higher for almost all VOCs following the heterologous prime-boost regimen.

Design and assembly of plant-based COVID-19 candidate vaccines: reсent development and future prospects

An outbreak of a new variant of the coronavirus infection, known as COVID-19, occurred at the end of 2019 in China, in the city of Wuhan. It was caused by the SARS-CoV-2 virus. This variant of the virus is characterized by a high degree of variability and, as the current situation with its spread across different regions of the globe shows, it can lead to a progressive spread of infection among the human population and become the cause of a pandemic. The world scientific community is making tremendous efforts to develop means of protection,prevention and treatment of this disease based on modern advances in molecular biology, immunology and vaccinology. This review provides information on the current state of research in the field of vaccine development against COVID-19 with an emphasis on the role of plants in solving this complex problem. Although plants have long been used by mankind as sources of various medicinal substances, in a pandemic, plant expression systems become attractive as biofactories or bioreactors for the production of artificially created protein molecules that include protective antigens against viral infection. The design and creation of such artificial molecules underlies the development of recombinant subunit vaccines aimed at a rapid response against the spread of infections with a high degree of variability. The review presents the state of research covering a period of just over two years, i. e. since the emergence of the new outbreak of coronavirus infection. The authors tried to emphasize the importance of rapid response of research groups from various scientific fields towards the use of existing developments to create means of protection against various pathogens. With two plant expression systems – stable and transient – as examples, the development of work on the creation of recombinant subunit vaccines against COVID-19 in various laboratories and commercial companies is shown. The authors emphasize that plant expression systems have promise for the development of not only protective means under conditions of rapid response (subunit vaccines), but also therapeutic agents in the form of monoclonal antibodies against COVID-19 synthesized in plant cells.