Efficacy and Safety of a Recombinant Plant-Based Adjuvanted Covid-19 Vaccine

Embracing Medication Needs of Patients based on Ethical, Dietary, and Religious Preferences

Purpose: Many patients seek medications without animal-derived ingredients for a multitude of reasons. The purpose of this comprehensive qualitative review is to assess current literature on the topic of animal-free medications and identify the roles that key stakeholders can play in addressing the needs of these patients. Methods: A comprehensive literature search was conducted on PubMed and Google Scholar from inception to June 2022 to identify key articles surrounding the topic of animal-free ingredients and medications. Results: The need for animal-free medications impacts not just vegans and vegetarians, but also those with dietary restrictions due to other beliefs. Three key stakeholder initiatives can address the needs of these patients: 1) Healthcare professionals (HCPs) should strive to select appropriate medications considering their patients' religious and/or cultural background; 2) patients must be involved and notify their providers about their dietary requirements; 3) pharmaceutical industry and manufacturers need to consider animal-free product formulations and provide clear labeling. Conclusion: There is a rising interest in animal-free medications and several organizations and advocacy groups have raised concerns for easier access to these medications. However, more regulatory guidance or oversight is needed. For the nearly 25% animal-free medications available in the market, independent certification marks would facilitate informed consumer decision-making.

The SARS-CoV-2 Spike Protein Receptor-Binding Domain Expressed in Rice Callus Features a Homogeneous Mix of Complex-Type Glycans

The spike protein receptor-binding domain (RBD) of SARS-CoV-2 is required for the infection of human cells. It is the main target that elicits neutralizing antibodies and also a major component of diagnostic kits. The large demand for this protein has led to the use of plants as a production platform. However, it is necessary to determine the N-glycan structures of an RBD to investigate its efficacy and functionality as a vaccine candidate or diagnostic reagent. Here, we analyzed the N-glycan profile of the RBD produced in rice callus. Of the two potential N-glycan acceptor sites, we found that one was not utilized and the other contained a mixture of complex-type N-glycans. This differs from the heterogeneous mixture of N-glycans found when an RBD is expressed in other hosts, including Nicotiana benthamiana. By comparing the glycosylation profiles of different hosts, we can select platforms that produce RBDs with the most beneficial N-glycan structures for different applications.

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.

Green horizons: how plant synthetic biology can enable space exploration and drive on Earth sustainability

As humanity looks towards expanding activity from low Earth orbit to the Moon and beyond, resource use efficiency and self-sustainability will be critical to ensuring success in the long term. Furthermore, solutions developed for the stringent requirements of space will be equally valuable in meeting sustainability goals here on Earth. Advances in synthetic biology allow us to harness the complex metabolism of life to produce the materials we need in situ. Translating those lessons learned from microbial systems to more carbon-efficient photosynthetic organisms is an area of growing interest. Plants can be engineered to sustainably meet a range of needs, from fuels to materials and medicines.

Bacterial growth-mediated systems remodelling of Nicotiana benthamiana defines unique signatures of target protein production in molecular pharming

The need for therapeutics to treat a plethora of medical conditions and diseases is on the rise and the demand for alternative approaches to mammalian-based production systems is increasing. Plant-based strategies provide a safe and effective alternative to produce biological drugs but have yet to enter mainstream manufacturing at a competitive level. Limitations associated with batch consistency and target protein production levels are present; however, strategies to overcome these challenges are underway. In this study, we apply state-of-the-art mass spectrometry-based proteomics to define proteome remodelling of the plant following agroinfiltration with bacteria grown under shake flask or bioreactor conditions. We observed distinct signatures of bacterial protein production corresponding to the different growth conditions that directly influence the plant defence responses and target protein production on a temporal axis. Our integration of proteomic profiling with small molecule detection and quantification reveals the fluctuation of secondary metabolite production over time to provide new insight into the complexities of dual system modulation in molecular pharming. Our findings suggest that bioreactor bacterial growth may promote evasion of early plant defence responses towards Agrobacterium tumefaciens (updated nomenclature to Rhizobium radiobacter). Furthermore, we uncover and explore specific targets for genetic manipulation to suppress host defences and increase recombinant protein production in molecular pharming.

Comparative efficacy and safety of COVID-19 vaccines in phase III trials: a network meta-analysis

BACKGROUND

Over a dozen vaccines are in or have completed phase III trials at an unprecedented speed since the World Health Organization (WHO) declared COVID-19 a pandemic. In this review, we aimed to compare and rank these vaccines indirectly in terms of efficacy and safety using a network meta-analysis.

METHODS

We searched Embase, MEDLINE, and the Cochrane Library for phase III randomized controlled trials (RCTs) from their inception to September 30, 2023. Two investigators independently selected articles, extracted data, and assessed the risk of bias. Outcomes included efficacy in preventing symptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the incidence of serious adverse events (SAEs) according to vaccine type and individual vaccines in adults and elderly individuals. The risk ratio and mean differences were calculated with 95% confidence intervals using a Bayesian network meta-analysis.

RESULTS

A total of 25 RCTs involving 22 vaccines were included in the study. None of vaccines had a higher incidence of SAEs than the placebo. Inactivated virus vaccines might be the safest, with a surface under the cumulative ranking curve (SUCRA) value of 0.16. BIV1-CovIran showed the highest safety index (SUCRA value: 0.13), followed by BBV152, Soberana, Gam-COVID-Vac, and ZF2001. There were no significant differences among the various types of vaccines regarding the efficacy in preventing symptomatic SARS-CoV-2 infection, although there was a trend toward higher efficacy of the mRNA vaccines (SUCRA value: 0.09). BNT162b2 showed the highest efficacy (SUCRA value: 0.02) among the individual vaccines, followed by mRNA-1273, Abdala, Gam-COVID-Vac, and NVX-CoV2373. BNT162b2 had the highest efficacy (SUCRA value: 0.08) in the elderly population, whereas CVnCoV, CoVLP + AS03, and CoronaVac were not significantly different from the placebo.

CONCLUSIONS

None of the different types of vaccines were significantly superior in terms of efficacy, while mRNA vaccines were significantly inferior in safety to other types. BNT162b2 had the highest efficacy in preventing symptomatic SARS-CoV-2 infection in adults and the elderly, whereas BIV1-CovIran had the lowest incidence of SAEs in adults.

Efficacy of adjuvant-associated COVID-19 vaccines against SARS-CoV-2 variants of concern in randomized controlled trials: A systematic review and meta-analysis

BACKGROUND

Adjuvants may enhance the efficacy of vaccines. however, the efficacy of adjuvant-associated COVID-19 vaccines (ACVs) remains unclear since the emergence of the COVID-19 pandemic. This study aimed to address this gap by conducting a systematic review and meta-analysis of the efficacy of ACVs against Severe Acute Respiratory Syndrome Coronavirus 2 CoV (SARS-CoV-2) variants of concern (VOC).

METHODS

A systematic search was conducted of randomized controlled trials (RCTs) evaluating the vaccine efficacy (VE) of ACVs against VOC (alpha, beta, gamma, delta, or Omicron), up to May 27, 2023. The DerSimonian-Laird random-effects model was used to assess VE with 95% confidence intervals (CI) through meta-analysis. Cochrane Risk of Bias tools were used to assess the risk of bias in RCTs.

RESULTS

Eight RCTs with 113,202 participants were included in the analysis, which incorporated 4 ACVs [Matrix-M (NVX-CoV2373), Alum (BBV152), CpG-1018/Alum (SCB-2019), and AS03 (CoVLP]). The pooled efficacy of full vaccination with ACVs against VOC was 88.0% (95% CI: 83.0-91.5). Full vaccination was effective against Alpha, Beta, Delta, and Gamma variants, with VE values of 93.66% (95% CI: 86.5-100.74), 64.70% (95% CI: 41.87-87.54), 75.95% (95% CI: 67.9-83.99), and 91.26% (95% CI: 84.35-98.17), respectively. Currently, there is a lack of RCT evidence regarding the efficacy of ACVs against the Omicron variant.

CONCLUSION

In this meta-analysis, it should be that full vaccination with ACVs has high efficacy against Alpha or Gamma variants and moderate efficacy against Beta and Delta variants. Notably, with the exception of the aluminum-adjuvanted vaccine, the other ACVs had moderate to high efficacy against the SARS-CoV-2 variant. This raises concerns about the effectiveness of ACVs booster vaccinations against Omicron.

Research progress on emulsion vaccine adjuvants

Vaccination is the most cost-effective method for preventing various infectious diseases. Compared with conventional vaccines, new-generation vaccines, especially recombinant protein or synthetic peptide vaccines, are safer but less immunogenic than crude inactivated microbial vaccines. The immunogenicity of these vaccines can be enhanced using suitable adjuvants. This is the main reason why adjuvants are of great importance in vaccine development. Several novel human emulsion-based vaccine adjuvants (MF59, AS03) have been approved for clinical use. This paper reviews the research progress on emulsion-based adjuvants and focuses on their mechanism of action. An outlook can be provided for the development of emulsion-based vaccine adjuvants.

Safety, immunogenicity and protective effectiveness of heterologous boost with a recombinant COVID-19 vaccine (Sf9 cells) in adult recipients of inactivated vaccines

Vaccines have proven effective in protecting populations against COVID-19, including the recombinant COVID-19 vaccine (Sf9 cells), the first approved recombinant protein vaccine in China. In this positive-controlled trial with 85 adult participants (Sf9 cells group: n = 44; CoronaVac group: n = 41), we evaluated the safety, immunogenicity, and protective effectiveness of a heterologous boost with the Sf9 cells vaccine in adults who had been vaccinated with the inactivated vaccine, and found a post-booster adverse events rate of 20.45% in the Sf9 cells group and 31.71% in the CoronaVac group (p = 0.279), within 28 days after booster injection. Neither group reported any severe adverse events. Following the Sf9 cells vaccine booster, the geometric mean titer (GMT) of binding antibodies to the receptor-binding domain of prototype SARS-CoV-2 on day 28 post-booster was significantly higher than that induced by the CoronaVac vaccine booster (100,683.37 vs. 9,451.69, p < 0.001). In the Sf9 cells group, GMTs of neutralizing antibodies against pseudo SARS-CoV-2 viruses (prototype and diverse variants of concern [VOCs]) increased by 22.23-75.93 folds from baseline to day 28 post-booster, while the CoronaVac group showed increases of only 3.29-10.70 folds. Similarly, neutralizing antibodies against live SARS-CoV-2 viruses (prototype and diverse VOCs) increased by 68.18-192.67 folds on day 14 post-booster compared with the baseline level, significantly greater than the CoronaVac group (19.67-37.67 folds). A more robust Th1 cellular response was observed with the Sf9 cells booster on day 14 post-booster (mean IFN-γ+ spot-forming cells per 2 × 105 peripheral blood mononuclear cells: 26.66 vs. 13.59). Protective effectiveness against symptomatic COVID-19 was approximately twice as high in the Sf9 cells group compared to the CoronaVac group (68.18% vs. 36.59%, p = 0.004). Our study findings support the high protective effectiveness of heterologous boosting with the recombinant COVID-19 vaccine (Sf9 cells) against symptomatic COVID-19 of diverse SARS-CoV-2 variants of concern, while causing no apparent safety concerns.

Effect of Platform Type on Clinical Efficacy of SARS-CoV-2 Vaccines in Prime Vaccination Settings: A Systematic Review and Meta-Regression of Randomized Controlled Trials

This systematic review investigated the association between platform type and the clinical efficacy of SARS-CoV-2 vaccines using the meta-regression of randomized controlled trials to compare the rates of the first appearance of symptomatic COVID-19 on the platforms. The trial search was conducted using PubMed, ClinicalTrials.gov, and the EU Clinical Trials Register. The main selection criteria included: non-active control, immunocompetent individuals without previous vaccination, and a low risk of bias. The platform effect was summarized with an incidence rate ratio (IRR) and a 95% confidence interval for every platform category against the reference. IRR was obtained by random-effect meta-regression with adjustment for confounding by effect modifiers. The analysis was conducted in per-protocol (PP) and modified intention-to-treat (mITT) sets. Six vaccine types with 35 trials were included. Vector vaccines were a reference category. In the PP set, rates of symptomatic COVID-19 on mRNA and protein subunit vaccines were significantly lower than on the vector: IRR = 0.30 [0.19; 0.46], p = 0.001 and 0.63 [0.46; 0.86], p = 0.012, respectively. There was no difference for inactivated and virus-like particle vaccines compared to the vector: IRR = 0.98 [0.71; 1.36], p = 0.913 and 0.70 [0.41; 1.20], p = 0.197, respectively. The rate of cases on DNA vaccines was significantly higher than that on the vector: IRR = 2.58 [1.17; 5.68], p = 0.034. Results for the mITT set were consistent. Platform type is an effect modifier of the clinical efficacy of SARS-CoV-2 vaccines.

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.

Plant-derived strategies to fight against severe acute respiratory syndrome coronavirus 2

The coronavirus disease 2019 (COVID-19) pandemic has caused an unprecedented crisis, which has been exacerbated because specific drugs and treatments have not yet been developed. In the post-pandemic era, humans and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) will remain in equilibrium for a long time. Therefore, we still need to be vigilant against mutated SARS-CoV-2 variants and other emerging human viruses. Plant-derived products are increasingly important in the fight against the pandemic, but a comprehensive review is lacking. This review describes plant-based strategies centered on key biological processes, such as SARS-CoV-2 transmission, entry, replication, and immune interference. We highlight the mechanisms and effects of these plant-derived products and their feasibility and limitations for the treatment and prevention of COVID-19. The development of emerging technologies is driving plants to become production platforms for various antiviral products, improving their medicinal potential. We believe that plant-based strategies will be an important part of the solutions for future pandemics.

E and M SARS-CoV-2 membrane protein expression and enrichment with plant lipid droplets

Plants are gaining traction as a cost-effective and scalable platform for producing recombinant proteins. However, expressing integral membrane proteins in plants is challenging due to their hydrophobic nature. In our study, we used transient and stable expression systems in Nicotiana benthamiana and Camelina sativa respectively to express SARS-CoV-2 E and M integral proteins, and target them to lipid droplets (LDs). LDs offer an ideal environment for folding hydrophobic proteins and aid in their purification through flotation. We tested various protein fusions with different linkers and tags and used three dimensional structure predictions to assess their effects. E and M mostly localized in the ER in N. benthamiana leaves but E could be targeted to LDs in oil accumulating tobacco when fused with oleosin, a LD integral protein. In Camelina sativa seeds, E and M were however found associated with purified LDs. By enhancing the accumulation of E and M within LDs through oleosin, we enriched these proteins in the purified floating fraction. This strategy provides an alternative approach for efficiently producing and purifying hydrophobic pharmaceuticals and vaccines using plant systems.

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.

Global Emergence of SARS-CoV2 Infection and Scientific Interventions to Contain its Spread

The global pandemic caused by COVID-19 posed a significant challenge to public health, necessitating rapid scientific interventions to tackle the spread of infection. The review discusses the key areas of research on COVID-19 including viral genomics, epidemiology, pathogenesis, diagnostics, and therapeutics. The genome sequencing of the virus facilitated the tracking of its evolution, transmission dynamics, and identification of variants. Epidemiological studies have provided insights into disease spread, risk factors, and the impact of public health infrastructure and social distancing measures. Investigations of the viral pathogenesis have elucidated the mechanisms underlying immune responses and severe manifestations including the long-term effects of COVID-19. Overall, the article provides an updated overview of the diagnostic methods developed for SARS-CoV-2 and discusses their strengths, limitations, and appropriate utilization in different clinical and public health settings. Furthermore, therapeutic approaches including antiviral drugs, immunomodulatory therapies, and repurposed medications have been investigated to alleviate disease severity and improve patient outcomes. Through a comprehensive analysis of these scientific efforts, the review provides an overview of the advancements made in understanding and tackling SARS-CoV-2, while underscoring the need for continued research to address the evolving challenges posed by this global health crisis.

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.

A review of SARS-CoV-2 variants and vaccines: Viral properties, mutations, vaccine efficacy, and safety

The severe acute respiratory syndrome coronavirus disease 2 instigated by coronavirus disease of 2019 (COVID-19) has delivered an unfathomable obstruction that has touched all sectors worldwide. Despite new vaccine technologies and mass administration of booster doses, the virus persists, and unknown the ending of the pandemic for new variants and sub-variants. Moreover, whether leaning on home medications or using plant extracts is sufficient often to combat the virus has generated tremendous interest in the scientific fraternity. Different databases including PubMed, Scopus, Web of Science, and Google Scholar used to find published articles linked with related topics. Currently, COVID-19 third and fourth shots of vaccines are progressively administered worldwide, where some countries trail others by a significant margin. Many proteins related to viral activity have changed, possibly boosting the virus infectivity and making antibodies ineffective. This study will reminisce the viral genome, associated pathways for viral protein functions, variants, and their mutations. The current, comprehensive review will also provide information on vaccine technologies developed by several biotech companies and the efficacy of their doses, costs including boosters on a mass level. As no vaccine is working to protect fully against all the variants, the new proactive vaccine research needs to be conducted based on all variants, their sub-lineage, and mutations.

Progress and prospect: Biosynthesis of plant natural products based on plant chassis

Plant-derived natural products are a specific class of active substances with numerous applications in the medical, energy, and industrial fields. Many of these substances are in high demand and have become the fundamental materials for various purposes. Recently, the use of synthetic biology to produce plant-derived natural products has become a significant trend. Plant chassis, in particular, offer unique advantages over microbial chassis in terms of cell structure, product affinity, safety, and storage. The development of the plant hairy root tissue culture system has accelerated the commercialization and industrialization of synthetic biology in the production of plant-derived natural products. This paper will present recent progress in the synthesis of various plant natural products using plant chassis, organized by the types of different structures. Additionally, we will summarize the four primary types of plant chassis used for synthesizing natural products from plant sources and review the enabling technologies that have contributed to the development of synthetic biology in recent years. Finally, we will present the role of isolated and combined use of different optimization strategies in breaking the upper limit of natural product production in plant chassis. This review aims to provide practical references for synthetic biologists and highlight the great commercial potential of plant chassis biosynthesis, such as hairy roots.

Mammalian cells-based platforms for the generation of SARS-CoV-2 virus-like particles

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of COVID-19. Though many COVID-19 vaccines have been developed, most of them are delivered via intramuscular injection and thus confer relatively weak mucosal immunity against the natural infection. Virus-Like Particles (VLPs) are self-assembled nanostructures composed of key viral structural proteins, that mimic the wild-type virus structure but are non-infectious and non-replicating due to the lack of viral genetic material. In this study, we efficiently generated SARS-CoV-2 VLPs by co-expressing the four SARS-CoV-2 structural proteins, specifically the membrane (M), small envelope (E), spike (S) and nucleocapsid (N) proteins. We show that these proteins are essential and sufficient for the efficient formation and release of SARS-CoV-2 VLPs. Moreover, we used lentiviral vectors to generate human cell lines that stably produce VLPs. Because VLPs can bind to the virus natural receptors, hence leading to entry into cells and viral antigen presentation, this platform could be used to develop novel vaccine candidates that are delivered intranasally.

Recent advances towards natural plants as potential inhibitors of SARS-Cov-2 targets

CONTEXT

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is still ongoing and currently the most striking epidemic disease. With the rapid global spread of SARS-CoV-2 variants, new antivirals are urgently needed to avert a more serious crisis. Inhibitors from traditional medicines or natural plants have shown promising results to fight COVID-19 with different mechanisms of action.

OBJECTIVES

To provide comprehensive and promising approaches to the medical community in the fight against this epidemic by reviewing potential plant-derived anti-SARS-CoV-2 inhibitors.

METHODS

Structural databases such as TCMSP (http://lsp.nwu.edu.cn/tcmsp.php), TCM Database @ Taiwan (http://tcm.cmu.edu.tw/), BATMAN-TCM (http://bionet.ncpsb.org/batman-tcm/) and TCMID (http://www.megabionet.org/tcmid/), as well as PubMed, Sci Finder, Research Gate, Science Direct, CNKI, Web of Science and Google Scholar were searched for relevant articles on TCMs and natural products against SARS-CoV-2.

RESULTS

Seven traditional Chinese medicines formulas have unique advantages in regulating the immune system for treating COVID-19. The plant-derived natural compounds as anti-SARS-CoV-2 inhibitors were identified based on 5 SARS-CoV-2 key proteins, namely, angiotensin-converting enzyme 2 (ACE2), 3 C-like protease (3CLpro), papain-like protease (PLpro), spike (S) protein, and nucleocapsid (N) protein.

CONCLUSIONS

A variety of natural products, such as flavonoids, terpenoids, phenols, and alkaloids, were identified, which could be used as potential SASR-Cov-2 inhibitors. These shed new light on the efficient discovery of SASR-Cov-2 inhibitors from natural products.

Immunogenicity and safety of adjuvant-associated COVID-19 vaccines: A systematic review and meta-analysis of randomized controlled trials

Background

The benefits and risks of adjuvant-associated COVID-19 vaccines (ACVs) are unclear. The study aimed to assess the immunogenicity and safety of ACVs compared with controls (placebo or the same vaccine without adjuvants [NACVs]).

Methods

Randomized controlled trials sourced from PubMed, EMBASE, Web of Science, and Cochrane Library were systematically reviewed. Evaluators extracted information independently. The evidence quality was assessed using random-effects models. The risk of bias was assessed using the Cochrane Risk of Bias tool.

Results

Of the 33 studies, 27 analyzed immunogenicity (n = 9069, ACVs group; n = 3757, control), and 26 analyzed safety (n = 58669, ACVs groups; n = 30733 control). Compared with controls, full vaccination with ACVs produced significant immune responses (relative risk [RR] of seroneutralization reaction, 12.3; 95 % confidence interval [95 % CI], 6.92-21.89; standardized mean deviation of geometric mean titer 3.96, 95 % CI, 3.35-4.58). Additionally, ACVs produced significant immunoreactivity compared with NACVs only (P < 0.05). Furthermore, full vaccination with ACVs significantly increased the risk of local and systemic adverse reactions (AEs) compared with controls. However, vaccination with ACVs did not significantly increase the risk of systemic and localized AEs compared with vaccination with NACVs only (P > 0.05). It was observed that ACVs had a lower risk of all-cause mortality than controls (RR, 0.51; 95 % CI 0.30-0.87). It was further found that ACVs produced nAb response against all sublines of the Omicron variant, but the antibody titers were lower than those for the SARS-CoV-2 original strain.

Conclusions

The findings of this meta-analysis demonstrate that ACVs may have a superior effect and an acceptable safety in preventing COVID-19. Although these results suggest the potential of ACVs, further studies are required.

Analysis of the protective efficacy of approved COVID-19 vaccines against Omicron variants and the prospects for universal vaccines

By the end of 2022, different variants of Omicron had rapidly spread worldwide, causing a significant impact on the Coronavirus disease 2019 (COVID-19) pandemic situation. Compared with previous variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), these new variants of Omicron exhibited a noticeable degree of mutation. The currently developed platforms to design COVID-19 vaccines include inactivated vaccines, mRNA vaccines, DNA vaccines, recombinant protein vaccines, virus-like particle vaccines, and viral vector vaccines. Many of these platforms have obtained approval from the US Food and Drug Administration (FDA) or the WHO. However, the Omicron variants have spread in countries where vaccination has taken place; therefore, the number of cases has rapidly increased, causing concerns about the effectiveness of these vaccines. This article first discusses the epidemiological trends of the Omicron variant and reviews the latest research progress on available vaccines. Additionally, we discuss progress in the development progress and practical significance of universal vaccines. Next, we analyze the neutralizing antibody effectiveness of approved vaccines against different variants of Omicron, heterologous vaccination, and the effectiveness of multivalent vaccines in preclinical trials. We hope that this review will provide a theoretical basis for the design, development, production, and vaccination strategies of novel coronavirus vaccines, thus helping to end the SARS-CoV-2 pandemic.

From bench to bedside: potential of translational research in COVID-19 and beyond

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and coronavirus disease 2019 (COVID-19) have been around for more than 3 years now. However, due to constant viral evolution, novel variants are emerging, leaving old treatment protocols redundant. As treatment options dwindle, infection rates continue to rise and seasonal infection surges become progressively common across the world, rapid solutions are required. With genomic and proteomic methods generating enormous amounts of data to expand our understanding of SARS-CoV-2 biology, there is an urgent requirement for the development of novel therapeutic methods that can allow translational research to flourish. In this review, we highlight the current state of COVID-19 in the world and the effects of post-infection sequelae. We present the contribution of translational research in COVID-19, with various current and novel therapeutic approaches, including antivirals, monoclonal antibodies and vaccines, as well as alternate treatment methods such as immunomodulators, currently being studied and reiterate the importance of translational research in the development of various strategies to contain COVID-19.

Artificial intelligence-driven systems engineering for next-generation plant-derived biopharmaceuticals

Recombinant biopharmaceuticals including antigens, antibodies, hormones, cytokines, single-chain variable fragments, and peptides have been used as vaccines, diagnostics and therapeutics. Plant molecular pharming is a robust platform that uses plants as an expression system to produce simple and complex recombinant biopharmaceuticals on a large scale. Plant system has several advantages over other host systems such as humanized expression, glycosylation, scalability, reduced risk of human or animal pathogenic contaminants, rapid and cost-effective production. Despite many advantages, the expression of recombinant proteins in plant system is hindered by some factors such as non-human post-translational modifications, protein misfolding, conformation changes and instability. Artificial intelligence (AI) plays a vital role in various fields of biotechnology and in the aspect of plant molecular pharming, a significant increase in yield and stability can be achieved with the intervention of AI-based multi-approach to overcome the hindrance factors. Current limitations of plant-based recombinant biopharmaceutical production can be circumvented with the aid of synthetic biology tools and AI algorithms in plant-based glycan engineering for protein folding, stability, viability, catalytic activity and organelle targeting. The AI models, including but not limited to, neural network, support vector machines, linear regression, Gaussian process and regressor ensemble, work by predicting the training and experimental data sets to design and validate the protein structures thereby optimizing properties such as thermostability, catalytic activity, antibody affinity, and protein folding. This review focuses on, integrating systems engineering approaches and AI-based machine learning and deep learning algorithms in protein engineering and host engineering to augment protein production in plant systems to meet the ever-expanding therapeutics market.

SARS-CoV-2 spike protein S1 subunit induces potent neutralizing responses in mice and is effective against Delta and Omicron variants

SARS-CoV-2, the virus responsible for the COVID-19 pandemic, belongs to the betacoronavirus genus. This virus has a high mutation rate, which rapidly evolves into new variants with different properties, such as increased transmissibility or immune evasion. Currently, the most prevalent global SARS-CoV-2 variant is Omicron, which is more transmissible than previous variants. Current available vaccines may be less effective against some currently existing SARS-CoV-2 variants, including the Omicron variant. The S1 subunit of the spike protein of SARS-CoV-2 has been a major target for COVID-19 vaccine development. It plays a crucial role in the virus's entry into host cells and is the primary target for neutralizing antibodies. In this study, the S1 subunit of the spike protein of SARS-CoV-2 was engineered and produced at a high level in Nicotiana benthamiana plant. The expression level of the recombinant S1 protein was greater than the 0.5-g/kg fresh weight, and the purification yield was at least ~0.3 g of pure protein/kg of plant biomass, which would make a plant-produced S1 antigen an ideal vaccine candidate for commercialization. Purified, the plant-produced SARS-CoV-2 S1 protein exhibited significantly higher binding to the SARS-CoV-2 receptor, angiotensin-converting enzyme 2 (ACE2). Moreover, we also show that recombinant S1 protein/antigen-elicited antibodies can neutralize the Delta or Omicron variants. Collectively, our results demonstrate that a plant-produced S1 antigen could be a promising vaccine candidate against SARS-CoV-2 variants including Omicron.

Delivery of biologics: Topical administration

Biologics are unaffordable to a large majority of the global population because of prohibitively expensive fermentation systems, purification and the requirement for cold chain for storage and transportation. Limitations of current production and delivery systems of biologics were evident during the recent pandemic when <2.5% of vaccines produced were available to low-income countries and ∼19 million doses were discarded in Africa due to lack of cold-chain infrastructure. Among FDA-approved biologics since 2015, >90% are delivered using invasive methods. While oral or topical drugs are highly preferred by patients because of their affordability and convenience, only two oral drugs have been approved by FDA since 2015. A newly launched oral biologic costs only ∼3% of the average cost of injectable biologics because of the simplified regulatory approval process by elimination of prohibitively expensive fermentation, purification, cold storage/transportation. In addition, the cost of developing a new biologic injectable product (∼$2.5 billion) has been dramatically reduced through oral or topical delivery. Topical delivery has the unique advantage of targeted delivery of high concentration protein drugs, without getting diluted in circulating blood. However, only very few topical drugs have been approved by the FDA. Therefore, this review highlights recent advances in oral or topical delivery of proteins at early or advanced stages of human clinical trials using chewing gums, patches or sprays, or nucleic acid drugs directly, or in combination with, nanoparticles and offers future directions.

An Overview of SARS-CoV-2 Etiopathogenesis and Recent Developments in COVID-19 Vaccines

The Coronavirus disease-2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has significantly impacted the health and socioeconomic status of humans worldwide. Pulmonary infection of SARS-CoV-2 results in exorbitant viral replication and associated onset of inflammatory cytokine storm and disease pathology in various internal organs. However, the etiopathogenesis of SARS-CoV-2 infection is not fully understood. Currently, there are no targeted therapies available to cure COVID-19, and most patients are treated empirically with anti-inflammatory and/or anti-viral drugs, based on the disease symptoms. Although several types of vaccines are currently implemented to control COVID-19 and prevent viral dissemination, the emergence of new variants of SARS-CoV-2 that can evade the vaccine-induced protective immunity poses challenges to current vaccination strategies and highlights the necessity to develop better and improved vaccines. In this review, we summarize the etiopathogenesis of SARS-CoV-2 and elaborately discuss various types of vaccines and vaccination strategies, focusing on those vaccines that are currently in use worldwide to combat COVID-19 or in various stages of clinical development to use in humans.

Formulation development and comparability studies with an aluminum-salt adjuvanted SARS-CoV-2 spike ferritin nanoparticle vaccine antigen produced from two different cell lines

The development of safe and effective second-generation COVID-19 vaccines to improve affordability and storage stability requirements remains a high priority to expand global coverage. In this report, we describe formulation development and comparability studies with a self-assembled SARS-CoV-2 spike ferritin nanoparticle vaccine antigen (called DCFHP), when produced in two different cell lines and formulated with an aluminum-salt adjuvant (Alhydrogel, AH). Varying levels of phosphate buffer altered the extent and strength of antigen-adjuvant interactions, and these formulations were evaluated for their (1) in vivo performance in mice and (2) in vitro stability profiles. Unadjuvanted DCFHP produced minimal immune responses while AH-adjuvanted formulations elicited greatly enhanced pseudovirus neutralization titers independent of ∼100%, ∼40% or ∼10% of the DCFHP antigen adsorbed to AH. These formulations differed, however, in their in vitro stability properties as determined by biophysical studies and a competitive ELISA for measuring ACE2 receptor binding of AH-bound antigen. Interestingly, after one month of 4°C storage, small increases in antigenicity with concomitant decreases in the ability to desorb the antigen from the AH were observed. Finally, we performed a comparability assessment of DCFHP antigen produced in Expi293 and CHO cells, which displayed expected differences in their N-linked oligosaccharide profiles. Despite consisting of different DCFHP glycoforms, these two preparations were highly similar in their key quality attributes including molecular size, structural integrity, conformational stability, binding to ACE2 receptor and mouse immunogenicity profiles. Taken together, these studies support future preclinical and clinical development of an AH-adjuvanted DCFHP vaccine candidate produced in CHO cells.

Impact of mutations on the plant-based production of recombinant SARS-CoV-2 RBDs

Subunit vaccines based on recombinant viral antigens are valuable interventions to fight existing and evolving viruses and can be produced at large-scale in plant-based expression systems. The recombinant viral antigens are often derived from glycosylated envelope proteins of the virus and glycosylation plays an important role for the immunogenicity by shielding protein epitopes. The receptor-binding domain (RBD) of the SARS-CoV-2 spike is a principal target for vaccine development and has been produced in plants, but the yields of recombinant RBD variants were low and the role of the N-glycosylation in RBD from different SARS-CoV-2 variants of concern is less studied. Here, we investigated the expression and glycosylation of six different RBD variants transiently expressed in leaves of Nicotiana benthamiana. All of the purified RBD variants were functional in terms of receptor binding and displayed almost full N-glycan occupancy at both glycosylation sites with predominately complex N-glycans. Despite the high structural sequence conservation of the RBD variants, we detected a variation in yield which can be attributed to lower expression and differences in unintentional proteolytic processing of the C-terminal polyhistidine tag used for purification. Glycoengineering towards a human-type complex N-glycan profile with core α1,6-fucose, showed that the reactivity of the neutralizing antibody S309 differs depending on the N-glycan profile and the RBD variant.

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.

An Efficient and Scalable Method for the Production of Immunogenic SARS-CoV-2 Virus-like Particles (VLP) from a Mammalian Suspension Cell Line

The rapid evolution of new SARS-CoV-2 variants poses a continuing threat to human health. Vaccination has become the primary therapeutic intervention. The goal of the current work was the construction of immunogenic virus-like particles (VLPs). Here, we describe a human cell line for cost-efficient and scalable production of immunogenic SARS-CoV-2 VLPs. The modular design of the VLP-production platform facilitates rapid adaptation to new variants. Methods: The N, M-, and E-protein genes were integrated into the genome of Expi293 cells (ExpiVLP_MEN). Subsequently, this cell line was further modified for the constitutive expression of the SARS-CoV-2 spike protein. The resulting cell line (ExpiVLP_SMEN) released SARS-CoV-2 VLP upon exposure to doxycycline. ExpiVLP_SMEN cells were readily adapted for VLP production in a 5 L bioreactor. Purified VLPs were quantified by Western blot, ELISA, and nanoparticle tracking analysis and visualized by electron microscopy. Immunogenicity was tested in mice. Results: The generated VLPs contained all four structural proteins, are within the size range of authentic SARS-CoV-2 virus particles, and reacted strongly and specifically with immunoserum from naturally infected individuals. The VLPs were stable in suspension at 4 °C for at least 10 weeks. Mice immunized with VLPs developed neutralizing antibodies against lentiviruses pseudotyped with the SARS-CoV-2 spike protein. The flexibility of the VLP-production platform was demonstrated by the rapid switch of the spike protein to a new variant of concern (BA.1/Omicron). The present study describes an efficient, scalable, and adaptable production method of immunogenic SARS-CoV-2 VLPs with therapeutic potential.

Developing an efficient MGCR microneedle nanovaccine patch for eliciting Th 1 cellular response against the SARS-CoV-2 infection

Rationale: Novel vaccine R&D is essential to interrupt the COVID-19 pandemic and other epidemics in the future. Subunit vaccines have received tremendous attention for their low cost and safety. To improve the immunogenicity of subunit vaccines, we developed a novel vaccine adjuvant system. Methods: Here we rationally designed a CpG 1018 and graphene oxide-based bi-adjuvant system to deliver the Receptor-Binding Domain (RBD) of the SARS-CoV-2 spike protein and obtained the graphene oxide-based complex adjuvant nanovaccine (GCR). Furthermore, we developed a microneedle patch vaccine (MGCR) based on the GCR vaccine. Results: GCR nanovaccine displayed superb antigen loading and encapsulation efficiency. Two dosages of vaccination of GCR nanovaccine could elicit adequate RBD-specific binding antibody response with 2.14-fold higher IgG titer than Alum adjuvant vaccine. The peptide pools assay demonstrated the robust RBD-specific Type 1 Cellular response induced by the GCR nanovaccine in CD8+ T cells. Furthermore, we prepared an MGCR microneedle patch, which generated a similar RBD-specific binding antibody response to the GCR vaccine, sustained a high antibody level above 16 weeks, and significantly elevated the Tcm proportion in mouse spleen. The MGCR microneedle patch vaccine also could be stably stored at room temperature for several months and administrated without medical staff, which maximizes the vaccine distribution efficiency. Conclusion: The vaccine system could significantly improve the vaccine distribution rate in low-income areas and offer a potential vaccination approach to fight against the SARS-Cov-2 infection and other pandemics occurred in the future.

Synthetic biology for plant genetic engineering and molecular farming

Many efforts have been put into engineering plants to improve crop yields and stress tolerance and boost the bioproduction of valuable molecules. Yet, our capabilities are still limited due to the lack of well-characterized genetic building blocks and resources for precise manipulation and given the inherently challenging properties of plant tissues. Advancements in plant synthetic biology can overcome these bottlenecks and release the full potential of engineered plants. In this review, we first discuss the recently developed plant synthetic elements from single parts to advanced circuits, software, and hardware tools expediting the engineering cycle. Next, we survey the advancements in plant biotechnology enabled by these recent resources. We conclude the review with outstanding challenges and future directions of plant synthetic biology.

COVID-19: An Overview of SARS-CoV-2 Variants-The Current Vaccines and Drug Development

The world is presently in crisis facing an outbreak of a health-threatening microorganism known as COVID-19, responsible for causing uncommon viral pneumonia in humans. The virus was first reported in Wuhan, China, in early December 2019, and it quickly became a global concern due to the pandemic. Challenges in this regard have been compounded by the emergence of several variants such as B.1.1.7, B.1.351, P1, and B.1.617, which show an increase in transmission power and resistance to therapies and vaccines. Ongoing researches are focused on developing and manufacturing standard treatment strategies and effective vaccines to control the pandemic. Despite developing several vaccines such as Pfizer/BioNTech and Moderna approved by the U.S. Food and Drug Administration (FDA) and other vaccines in phase 4 clinical trials, preventive measures are mandatory to control the COVID-19 pandemic. In this review, based on the latest findings, we will discuss different types of drugs as therapeutic options and confirmed or developing vaccine candidates against SARS-CoV-2. We also discuss in detail the challenges posed by the variants and their effect on therapeutic and preventive interventions.

Exigency of Plant-Based Vaccine against COVID-19 Emergence as Pandemic Preparedness

After two years since the declaration of COVID-19 as a pandemic by the World Health Organization (WHO), more than six million deaths have occurred due to SARS-CoV-2, leading to an unprecedented disruption of the global economy. Fortunately, within a year, a wide range of vaccines, including pathogen-based inactivated and live-attenuated vaccines, replicating and non-replicating vector-based vaccines, nucleic acid (DNA and mRNA)-based vaccines, and protein-based subunit and virus-like particle (VLP)-based vaccines, have been developed to mitigate the severe impacts of the COVID-19 pandemic. These vaccines have proven highly effective in reducing the severity of illness and preventing deaths. However, the availability and supply of COVID-19 vaccines have become an issue due to the prioritization of vaccine distribution in most countries. Additionally, as the virus continues to mutate and spread, questions have arisen regarding the effectiveness of vaccines against new strains of SARS-CoV-2 that can evade host immunity. The urgent need for booster doses to enhance immunity has been recognized. The scarcity of "safe and effective" vaccines has exacerbated global inequalities in terms of vaccine coverage. The development of COVID-19 vaccines has fallen short of the expectations set forth in 2020 and 2021. Furthermore, the equitable distribution of vaccines at the global and national levels remains a challenge, particularly in developing countries. In such circumstances, the exigency of plant virus-based vaccines has become apparent as a means to overcome supply shortages through fast manufacturing processes and to enable quick and convenient distribution to millions of people without the reliance on a cold chain system. Moreover, plant virus-based vaccines have demonstrated both safety and efficacy in eliciting robust cellular immunogenicity against COVID-19 pathogens. This review aims to shed light on the advantages and disadvantages of different types of vaccines developed against SARS-CoV-2 and provide an update on the current status of plant-based vaccines in the fight against the COVID-19 pandemic.

Plant-produced RBD and cocktail-based vaccine candidates are highly effective against SARS-CoV-2, independently of its emerging variants

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel and highly pathogenic coronavirus that caused an outbreak in Wuhan City, China, in 2019 and then spread rapidly throughout the world. Although several coronavirus disease 2019 (COVID-19) vaccines are currently available for mass immunization, they are less effective against emerging SARS-CoV-2 variants, especially the Omicron (B.1.1.529). Recently, we successfully produced receptor-binding domain (RBD) variants of the spike (S) protein of SARS-CoV-2 and an antigen cocktail in Nicotiana benthamiana, which are highly produced in plants and elicited high-titer antibodies with potent neutralizing activity against SARS-CoV-2. In this study, based on neutralization ability, we demonstrate that plant-produced RBD and cocktail-based vaccine candidates are highly effective against SARS-CoV-2, independently of its emerging variants. These data demonstrate that plant-produced RBD and cocktail-based proteins are the most promising vaccine candidates and may protect against Delta and Omicron-mediated COVID-19. This is the first report describing vaccines against SARS-CoV-2, which demonstrate significant activities against Delta and Omicron variants.

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.

Molecular Farming Strategy for the Rapid Production of Protein-Based Reagents for Use in Infectious Disease Diagnostics

Recombinant proteins are a major breakthrough in biomedical research with a wide range of applications from diagnostics to therapeutics. Strategic construct design, consistent expression platforms, and suitable upstream and downstream techniques are key considerations to produce commercially viable recombinant proteins. The recombinant antigenic protein production for use either as a diagnostic reagent or subunit vaccine formulation is usually carried out in prokaryotic or eukaryotic expression platforms. Microbial and mammalian systems dominate the biopharmaceutical industry for such applications. However, there is no universal expression system that can meet all the requirements for different types of proteins. The adoptability of any expression system is likely based on the quality and quantity of the proteins that can be produced from it. The huge demand of recombinant proteins for different applications requires an inexpensive production platform for rapid development. The molecular farming scientific community has been promoting the plant system for nearly 3 decades as a cost-effective alternative to produce high-quality proteins for research, diagnostic, and therapeutic applications. Here, we discuss how plant biotechnology could offer solutions for the rapid and scalable production of protein antigens as low-cost diagnostic reagents for use in functional assays.

Adjuvant physiochemistry and advanced nanotechnology for vaccine development

Vaccines comprising innovative adjuvants are rapidly reaching advanced translational stages, such as the authorized nanotechnology adjuvants in mRNA vaccines against COVID-19 worldwide, offering new strategies to effectively combat diseases threatening human health. Adjuvants are vital ingredients in vaccines, which can augment the degree, extensiveness, and longevity of antigen specific immune response. The advances in the modulation of physicochemical properties of nanoplatforms elevate the capability of adjuvants in initiating the innate immune system and adaptive immunity, offering immense potential for developing vaccines against hard-to-target infectious diseases and cancer. In this review, we provide an essential introduction of the basic principles of prophylactic and therapeutic vaccination, key roles of adjuvants in augmenting and shaping immunity to achieve desired outcomes and effectiveness, and the physiochemical properties and action mechanisms of clinically approved adjuvants for humans. We particularly focus on the preclinical and clinical progress of highly immunogenic emerging nanotechnology adjuvants formulated in vaccines for cancer treatment or infectious disease prevention. We deliberate on how the immune system can sense and respond to the physicochemical cues (e.g., chirality, deformability, solubility, topology, and chemical structures) of nanotechnology adjuvants incorporated in the vaccines. Finally, we propose possible strategies to accelerate the clinical implementation of nanotechnology adjuvanted vaccines, such as in-depth elucidation of nano-immuno interactions, antigen identification and optimization by the deployment of high-dimensional multiomics analysis approaches, encouraging close collaborations among scientists from different scientific disciplines and aggressive exploration of novel nanotechnologies.

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.

Vaccine adjuvants: mechanisms and platforms

Adjuvants are indispensable components of vaccines. Despite being widely used in vaccines, their action mechanisms are not yet clear. With a greater understanding of the mechanisms by which the innate immune response controls the antigen-specific response, the adjuvants' action mechanisms are beginning to be elucidated. Adjuvants can be categorized as immunostimulants and delivery systems. Immunostimulants are danger signal molecules that lead to the maturation and activation of antigen-presenting cells (APCs) by targeting Toll-like receptors (TLRs) and other pattern recognition receptors (PRRs) to promote the production of antigen signals and co-stimulatory signals, which in turn enhance the adaptive immune responses. On the other hand, delivery systems are carrier materials that facilitate antigen presentation by prolonging the bioavailability of the loaded antigens, as well as targeting antigens to lymph nodes or APCs. The adjuvants' action mechanisms are systematically summarized at the beginning of this review. This is followed by an introduction of the mechanisms, properties, and progress of classical vaccine adjuvants. Furthermore, since some of the adjuvants under investigation exhibit greater immune activation potency than classical adjuvants, which could compensate for the deficiencies of classical adjuvants, a summary of the adjuvant platforms under investigation is subsequently presented. Notably, we highlight the different action mechanisms and immunological properties of these adjuvant platforms, which will provide a wide range of options for the rational design of different vaccines. On this basis, this review points out the development prospects of vaccine adjuvants and the problems that should be paid attention to in the future.

The role of vaccines in the COVID-19 pandemic: what have we learned?

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged late in 2019 and caused the coronavirus disease 2019 (COVID-19) pandemic that has so far claimed approximately 20 million lives. Vaccines were developed quickly, became available in the end of 2020, and had a tremendous impact on protection from SARS-CoV-2 mortality but with emerging variants the impact on morbidity was diminished. Here I review what we learned from COVID-19 from a vaccinologist's perspective.

T-cell immunity to SARS-CoV-2: what if the known best is not the optimal course for the long run? Adapting to evolving targets

Humanity did surprisingly well so far, considering how unprepared it was to respond to the coronavirus disease 2019 (COVID-19) threat. By blending old and ingenious new technology in the context of the accumulated knowledge on other human coronaviruses, several vaccine candidates were produced and tested in clinical trials in record time. Today, five vaccines account for the bulk of the more than 13 billion doses administered worldwide. The ability to elicit biding and neutralizing antibodies most often against the spike protein is a major component of the protection conferred by immunization but alone it is not enough to limit virus transmission. Thus, the surge in numbers of infected individuals by newer variants of concern (VOCs) was not accompanied by a proportional increase in severe disease and death rate. This is likely due to antiviral T-cell responses, whose evasion is more difficult to achieve. The present review helps navigating the very large literature on T cell immunity induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and vaccination. We examine the successes and shortcomings of the vaccinal protection in the light of the emergence of VOCs with breakthrough potential. SARS-CoV-2 and human beings will likely coexist for a long while: it will be necessary to update existing vaccines to improve T-cell responses and attain better protection against COVID-19.

Plant-Produced Nanoparticles Based on Artificial Self-Assembling Peptide Bearing the Influenza M2e Epitope

Despite advances in vaccine development, influenza remains a persistent global health threat and the search for a broad-spectrum recombinant vaccine against influenza continues. The extracellular domain of the transmembrane protein M2 (M2e) of the influenza A virus is highly conserved and can be used to develop a universal vaccine. M2e is a poor immunogen by itself, but it becomes highly immunogenic when linked to an appropriate carrier. Here, we report the transient expression of a recombinant protein comprising four tandem copies of M2e fused to an artificial self-assembling peptide (SAP) in plants. The hybrid protein was efficiently expressed in Nicotiana benthamiana using the self-replicating potato virus X-based vector pEff. The protein was purified using metal affinity chromatography under denaturing conditions. The hybrid protein was capable of self-assembly in vitro into spherical particles 15-30 nm in size. The subcutaneous immunization of mice with M2e-carrying nanoparticles induced high levels of M2e-specific IgG antibodies in serum and mucosal secretions. Immunization provided mice with protection against a lethal influenza A virus challenge. SAP-based nanoparticles displaying M2e peptides can be further used to develop a recombinant "universal" vaccine against influenza A produced in plants.

Assessing the robustness of COVID-19 vaccine efficacy trials: systematic review and meta-analysis, January 2023

BackgroundVaccines play a crucial role in the response to COVID-19 and their efficacy is thus of great importance.AimTo assess the robustness of COVID-19 vaccine efficacy (VE) trial results using the fragility index (FI) and fragility quotient (FQ) methodology.MethodsWe conducted a Cochrane and PRISMA-compliant systematic review and meta-analysis of COVID-19 VE trials published worldwide until 22 January 2023. We calculated the FI and FQ for all included studies and assessed their associations with selected trial characteristics using Wilcoxon rank sum tests and Kruskal-Wallis H tests. Spearman correlation coefficients and scatter plots were used to quantify the strength of correlation of FIs and FQs with trial characteristics.ResultsOf 6,032 screened records, we included 40 trials with 54 primary outcomes, comprising 909,404 participants with a median sample size per outcome of 13,993 (interquartile range (IQR): 8,534-25,519). The median FI and FQ was 62 (IQR: 22-123) and 0.50% (IQR: 0.24-0.92), respectively. FIs were positively associated with sample size (p < 0.001), and FQs were positively associated with type of blinding (p = 0.023). The Spearman correlation coefficient for FI with sample size was moderately strong (0.607), and weakly positive for FI and FQ with VE (0.138 and 0.161, respectively).ConclusionsThis was the largest study on trial robustness to date. Robustness of COVID-19 VE trials increased with sample size and varied considerably across several other important trial characteristics. The FI and FQ are valuable complementary parameters for the interpretation of trial results and should be reported alongside established trial outcome measures.

Design and characterization of chimeric Rabies-SARS-CoV-2 virus-like particles for vaccine purposes

Due to the high number of doses required to achieve adequate coverage in the context of COVID-19 pandemics, there is a great need for novel vaccine developments. In this field, there have been research approaches that focused on the production of SARS-CoV-2 virus-like particles. These are promising vaccine candidates as their structure is similar to that of native virions but they lack the genome, constituting a biosafe alternative. In order to produce these structures using mammal cells, it has been established that all four structural proteins must be expressed. Here we report the generation and characterization of a novel chimeric virus-like particle (VLP) that can be produced by the expression of a single novel fusion protein that contains SARS-CoV-2 spike (S) ectodomain fused to rabies glycoprotein membrane anchoring region in HEK293 cells. This protein is structurally similar to native S and can autonomously bud forming enveloped VLPs that resemble native virions both in size and in morphology, displaying S ectodomain and receptor binding domain (RBD) on their surface. As a proof of concept, we analyzed the immunogenicity of this vaccine candidate in mice and confirmed the generation of anti-S, anti-RBD, and neutralizing antibodies. KEY POINTS: • A novel fusion rabies glycoprotein containing S ectodomain was designed. • Fusion protein formed cVLPs that were morphologically similar to SARS-CoV-2 virions. • cVLPs induced anti-S, anti-RBD, and neutralizing antibodies in mice.

Safety and immunogenicity of the protein-based PHH-1V compared to BNT162b2 as a heterologous SARS-CoV-2 booster vaccine in adults vaccinated against COVID-19: a multicentre, randomised, double-blind, non-inferiority phase IIb trial

Background

A SARS-CoV-2 protein-based heterodimer vaccine, PHH-1V, has been shown to be safe and well-tolerated in healthy young adults in a first-in-human, Phase I/IIa study dose-escalation trial. Here, we report the interim results of the Phase IIb HH-2, where the immunogenicity and safety of a heterologous booster with PHH-1V is assessed versus a homologous booster with BNT162b2 at 14, 28 and 98 days after vaccine administration.

Methods

The HH-2 study is an ongoing multicentre, randomised, active-controlled, double-blind, non-inferiority Phase IIb trial, where participants 18 years or older who had received two doses of BNT162b2 were randomly assigned in a 2:1 ratio to receive a booster dose of vaccine-either heterologous (PHH-1V group) or homologous (BNT162b2 group)-in 10 centres in Spain. Eligible subjects were allocated to treatment stratified by age group (18-64 versus ≥65 years) with approximately 10% of the sample enrolled in the older age group. The primary endpoints were humoral immunogenicity measured by changes in levels of neutralizing antibodies (PBNA) against the ancestral Wuhan-Hu-1 strain after the PHH-1V or the BNT162b2 boost, and the safety and tolerability of PHH-1V as a boost. The secondary endpoints were to compare changes in levels of neutralizing antibodies against different variants of SARS-CoV-2 and the T-cell responses towards the SARS-CoV-2 spike glycoprotein peptides. The exploratory endpoint was to assess the number of subjects with SARS-CoV-2 infections ≥14 days after PHH-1V booster. This study is ongoing and is registered with ClinicalTrials.gov, NCT05142553.

Findings

From 15 November 2021, 782 adults were randomly assigned to PHH-1V (n = 522) or BNT162b2 (n = 260) boost vaccine groups. The geometric mean titre (GMT) ratio of neutralizing antibodies on days 14, 28 and 98, shown as BNT162b2 active control versus PHH-1V, was, respectively, 1.68 (p < 0.0001), 1.31 (p = 0.0007) and 0.86 (p = 0.40) for the ancestral Wuhan-Hu-1 strain; 0.62 (p < 0.0001), 0.65 (p < 0.0001) and 0.56 (p = 0.003) for the Beta variant; 1.01 (p = 0.92), 0.88 (p = 0.11) and 0.52 (p = 0.0003) for the Delta variant; and 0.59 (p ≤ 0.0001), 0.66 (p < 0.0001) and 0.57 (p = 0.0028) for the Omicron BA.1 variant. Additionally, PHH-1V as a booster dose induced a significant increase of CD4⁺ and CD8⁺ T-cells expressing IFN-γ on day 14. There were 458 participants who experienced at least one adverse event (89.3%) in the PHH-1V and 238 (94.4%) in the BNT162b2 group. The most frequent adverse events were injection site pain (79.7% and 89.3%), fatigue (27.5% and 42.1%) and headache (31.2 and 40.1%) for the PHH-1V and the BNT162b2 groups, respectively. A total of 52 COVID-19 cases occurred from day 14 post-vaccination (10.14%) for the PHH-1V group and 30 (11.90%) for the BNT162b2 group (p = 0.45), and none of the subjects developed severe COVID-19.

Interpretation

Our interim results from the Phase IIb HH-2 trial show that PHH-1V as a heterologous booster vaccine, when compared to BNT162b2, although it does not reach a non-inferior neutralizing antibody response against the Wuhan-Hu-1 strain at days 14 and 28 after vaccination, it does so at day 98. PHH-1V as a heterologous booster elicits a superior neutralizing antibody response against the previous circulating Beta and the currently circulating Omicron BA.1 SARS-CoV-2 variants in all time points assessed, and for the Delta variant on day 98 as well. Moreover, the PHH-1V boost also induces a strong and balanced T-cell response. Concerning the safety profile, subjects in the PHH-1V group report significantly fewer adverse events than those in the BNT162b2 group, most of mild intensity, and both vaccine groups present comparable COVID-19 breakthrough cases, none of them severe.

Funding

HIPRA SCIENTIFIC, S.L.U.

Vaccine confidence among those living with allergy during the COVID pandemic (ACCORD): A scoping review

Background

Reports of allergic reactions to coronavirus disease 2019 (COVID-19) vaccines, coupled with an "infodemic" of misinformation, carry the potential to undermine confidence in the COVID-19 vaccines. However, no attempts have been made to comprehensively synthesize the literature on how allergic disease and fear of allergic reactions to the vaccines contribute to hesitancy.

Objectives

Our aim was to review the academic and gray literature on COVID-19 vaccine hesitancy and allergic reactions.

Methods

We searched 4 databases (CINAHL, PsycINFO, MEDLINE, and Embase) using a search strategy developed by content and methodologic experts. No restrictions were applied regarding COVID-19 vaccine type, country of study, or patient age. Eligible articles were restricted to 10 languages.

Results

Of the 1385 unique records retrieved from our search, 60 articles (4.3%) were included. Allergic reactions to the COVID-19 vaccine were rare but slightly more common in individuals with a history of allergic disease. A fifth of the studies (13 of 60 [22%]) discussed vaccine hesitancy due to possibility of an allergic reaction. Additionally, the present review identified research on details of vaccine-related anaphylaxis (eg, a mean and median [excluding clinical trial data] of 12.4 and 5 cases per million doses, respectively) and allergic reactions (eg, a mean and median [excluding clinical trial data] of 489 and 528 cases per million doses, respectively).

Conclusion

COVID-19 vaccine acceptance among individuals living with allergy and among those with no history of allergic disease may be affected by fear of an allergic reaction. Despite the low incidence of allergic reactions to the COVID-19 vaccine, fear of such reactions is one of the most commonly cited concerns reported in the literature.