Current state-of-the-art in the use of plants for the production of recombinant vaccines against infectious bursal disease virus

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.

Antimicrobial Peptides: The Production of Novel Peptide-Based Therapeutics in Plant Systems

The increased prevalence of antibiotic resistance is alarming and has a significant impact on the economies of emerging and underdeveloped nations. The redundancy of antibiotic discovery platforms (ADPs) and injudicious use of conventional antibiotics has severely impacted millions, across the globe. Potent antimicrobials from biological sources have been extensively explored as a ray of hope to counter the growing menace of antibiotic resistance in the population. Antimicrobial peptides (AMPs) are gaining momentum as powerful antimicrobial therapies to combat drug-resistant bacterial strains. The tremendous therapeutic potential of natural and synthesized AMPs as novel and potent antimicrobials is highlighted by their unique mode of action, as exemplified by multiple research initiatives. Recent advances and developments in antimicrobial discovery and research have increased our understanding of the structure, characteristics, and function of AMPs; nevertheless, knowledge gaps still need to be addressed before these therapeutic options can be fully exploited. This thematic article provides a comprehensive insight into the potential of AMPs as potent arsenals to counter drug-resistant pathogens, a historical overview and recent advances, and their efficient production in plants, defining novel upcoming trends in drug discovery and research. The advances in synthetic biology and plant-based expression systems for AMP production have defined new paradigms in the efficient production of potent antimicrobials in plant systems, a prospective approach to countering drug-resistant pathogens.

An Improved Immunochromatographic Strip Based on Plant-Derived E2 for Detection of Antibodies against Classical Swine Fever Virus

Vaccination is an effective method to control the spread of classical swine fever virus (CSFV), which is a major cause of economic losses to the swine industry. Although serological detection assays are commonly used to assess immune status, current methods for monitoring of antibodies (Abs) are time-consuming, expensive, and require cell culture and virus manipulation. To address these problems, the E2 protein of CSFV was expressed in transgenic rice seeds as a labeled antigen for the development of an immunochromatographic test strip (ICTS) for rapid, precise, and cost-effective detection of Abs. The ICTS has a reasonable sensitivity of 1:128,000 for detection of serum Abs against CSFV and no cross-reactivity with Abs of other porcine viruses. The similarity of the results between the proposed ICTS and a commercial enzyme-linked immunosorbent assay was 94.1% (128/136) for detection of serum Abs from immunized animals and 92.3% (72/78) for detection of maternally derived Abs. The proposed assay was successfully used to monitor Abs against E2 of both pigs and rabbits immunized with a live attenuated vaccine or an E2 subunit vaccine. The results confirmed that the ICTS can be applied to detect Ab levels in animals with different immunological backgrounds. The ICTS based on plant-derived E2 is a relatively inexpensive, rapid, and accurate assay for detection of Abs against CSFV and avoids the risk of contamination by animal products. IMPORTANCE The E2 protein of classical swine fever virus (CSFV) was expressed in transgenic rice endosperms as a diagnostic antigen for use with a rapid colloidal gold assay for the detection of antibodies (Abs) against CSFV. This improved test was used to monitor Abs against the E2 protein in both pigs and rabbits immunized with a live attenuated vaccine or E2 subunit vaccine. The assay successfully detected Ab levels in serum samples from piglets with different immunological backgrounds. In contrast to current E2 protein-based diagnostic methods using Escherichia coli or insect cells as expression systems, plant-derived E2 avoids the limitations of low immunogenicity of eukaryotic expression systems and potential contamination of fetal bovine serum with bovine viral diarrhea virus in cell culture.

Chitosan/Calcium-Coated Ginsenoside Rb1 Phosphate Flower-like Microparticles as an Adjuvant to Enhance Immune Responses

Simple Summary

The field-level control over IBD is primarily via vaccination. The development of high effective IBV vaccine has drawing great attentions worldwide. Herein, the GRb1 was encap-sulated into Calcium phosphate and chitosan core-structure nanoparticles microspheres, which con-stitute a novel system for nanoparticle delivery (GRb1/IL-4@CS/Cap). The new nano-adjuvant de-livery system could induce the activation of chicken dendritic cells ( DCs ), with up-regulate the expression of MHC II and CD80, and increase the production of IL-1β and TNF-α. At the same time, it can trigger higher levels of IBDV-specific IgG and higher IgG2a/IgG1 ratio, and promote the production of IFN-γ, TNF-α, IL-4, IL-6, IL-1α, and IL-1βand other cytokines in chicken serum after vaccination, it provides an effective adjuvant system for the development of chicken IBDV attenu-ated vaccine.

Abstract

Infectious bursal disease (IBD) is a highly contagious immunocompromising disorder that caused great economic losses in the poultry industry. The field-level control over IBD is primarily via vaccination. The development of a highly effective IBV vaccine has drawn great attention worldwide. Chitosan/Calcium Phosphate (CS/CaP) nanoparticle was a newly developed effective biological delivery system for drug and antigen. Ginsenoside Rb1 is one of the main bioactive components of ginseng root extract, which has antioxidant, anti-inflammatory and immunological enhancement effects. Until now, the combined effect of CS/CaP and ginsenoside Rb1 on the chicken immune response had remained unknown. In this study, the GRb1 and IL-4 were encapsulated into Calcium phosphate and chitosan core structure nanoparticles microspheres (GRb1/IL-4@CS/CaP), and the effect of a newly developed delivery system on an infectious bursal disease virus (IBDV) attenuated vaccine was further evaluated. The results demonstrated that GRb1/IL-4@CS/CaP treatment could induce the activation of chicken dendritic cells (DCs), with the upregulated expression of MHCII and CD80, and the increased production of IL-1β and TNF-α. Importantly, GRb1/IL-4@CS/CaP could trigger a higher level of IBDV-specific IgG and a higher ratio of IgG2a/IgG1 than the traditional adjuvant groups, promoting the production of cytokine, including IFN-γ, TNF-α, IL-4, IL-6, IL-1α, and IL-1β, in chicken serum after 28 d and 42 d post-vaccine. Taken in all, GRb1/IL-4@CS/CaP could elicit prolonged vigorous immune responses for IBDV attenuated vaccine in chicken, which might provide an effective adjuvant system for avian vaccine development.

Development of a Novel Assay Based on Plant-Produced Infectious Bursal Disease Virus VP3 for the Differentiation of Infected From Vaccinated Animals

Infectious bursal disease virus is the causative agent of Gumboro disease, a severe infection that affects young chickens and is associated with lymphoid depletion in the bursa of Fabricius. Traditional containment strategies are based either on inactivated or live-attenuated vaccines. These approaches have several limitations such as residual virulence or low efficacy in the presence of maternally derived antibodies (MDA) but, most importantly, the impossibility to detect the occurrence of natural infections in vaccinated flocks. Therefore, the development of novel vaccination strategies allowing the differentiation of infected from vaccinated animals (DIVA) is a priority. Recently, commercial vectored and experimental subunit vaccines based on VP2 have been proved effective in protecting from clinical disease and posed the basis for the development of novel DIVA strategies. In this study, an engineered version of the VP3 protein of IBDV (His-VP3) was produced in plants, successfully purified from Nicotiana benthamiana leaves, and used to develop an enzyme-linked immunosorbent assay (ELISA) for the detection of anti-VP3 antibodies. The His-VP3 ELISA was validated with a panel of 180 reference sera and demonstrated to have 100% sensitivity (95% CI: 94.7-100.0) and 94.17% specificity (95% CI: 88.4-97.6). To evaluate the application of His-VP3 ELISA as a DIVA test, the novel assay was used to monitor, in combination with a commercial kit, detecting anti-VP2 antibodies, the immune response of chickens previously immunized with an inactivated IBDV vaccine, a recombinant Turkey herpes virus carrying the VP2 of IBDV (HVT-ND-IBD) or with plant-produced VP2 particles. The combined tests correctly identified the immune status of the vaccinated specific pathogen free white-leghorn chickens. Moreover, the His-VP3 ELISA correctly detected MDA against VP3 in commercial broiler chicks and showed that antibody titers fade with time, consistent with the natural decrease of maternally derived immunity. Finally, the novel assay, in combination with a VP2-specific ELISA, demonstrated its potential application as a DIVA test in chickens inoculated with VP2-based vaccines, being able to detect the seroconversion after challenge with a very virulent IBDV strain.

Oral Immunization With Plant-Based Vaccine Induces a Protective Response Against Infectious Bursal Disease

Infectious bursal disease virus (IBDV) is the etiological agent of an immunosuppressive and highly contagious disease that affects young birds causing important economic losses in the poultry industry worldwide. We have previously developed a plant-based vaccine candidate for infectious bursal disease (IBD) that is able to protect against infection with IBDV when administered through intramuscular (im) route. Given that oral vaccination is non-invasive and stimulates the immunity of the mucosal gastrointestinal surface, the initial site of contact and entry of IBDV, the aim of this work was to study if our immunogen was also able to elicit a protective immune response when orally administered. We demonstrated that 85% of the animals that received two oral doses of the vaccine formulation and all animals that were orally boosted after an im prime scheme developed virus neutralizing antibodies and were protected against IBDV infection, evidenced by the bursa/body weight (BB) ratio, absence of T-cell infiltration, and low viral load in bursa. Although mild to moderate bursal damage was observed in some of these animals, these lesions were not as severe as the ones observed in challenged control groups, which also presented signs of acute inflammation, bursal atrophy, T-cell infiltration, and absence of viral clearance. These results show that two immunizations with our recombinant immunogen are able to induce a specific and protective immune response in chicken against IBDV when orally administered in a prime/boost scheme or when the oral boost follows an im prime scheme. In conclusion, our oral plant-based vaccine candidate could represent a viable alternative to conventional vaccines and is of great interest to the poultry industry.

The expression in plants of an engineered VP2 protein of Infectious Bursal Disease Virus induces formation of structurally heterogeneous particles that protect from a very virulent viral strain

Infectious Bursal Disease Virus (IBDV), the etiological agent of Gumboro disease, causes mortality and immunosuppression in chickens and major losses to poultry industry worldwide. The IBDV major capsid protein VP2 is considered the best candidate for the production of novel subunit vaccines. This structural protein contains the major conformational epitopes responsible for the induction of IBDV neutralizing antibodies in chickens and has been demonstrated able to form supramolecular structures in yeast and insect cells. The aim of this study was to express an engineered version of the VP2 protein (His-pVP2) to verify its ability to self-assemble into virus-like particles in plants. The recombinant VP2 was transiently expressed by agroinfiltration in Nicotiana benthamiana and transmission electron microscopy of sucrose density gradient fractions revealed the presence of a mixed population of differently shaped particles ranging from spherical capsids, with a diameter between ~25 and ~70 nm, to tubular structures, with variable length (from 100 to 400 nm). The recombinant VP2-based particles when used for the intramuscular immunization of specific-pathogen-free chicks resulted able to induce the production of anti-IBDV specific antibodies at titers comparable to those induced by a commercial vaccine. Moreover, all the immunized birds survived to the challenge with a Moroccan very virulent IBDV strain with no major histomorphological alterations of the Bursa of Fabricius, similarly to what obtained with the commercial inactivated vaccine.

Plant production and functional characterization of catfish interleukin-22 as a natural immune stimulant for aquaculture fish

As the world population increases and wild caught fisheries decline, aquaculture offers a sustainable solution addressing this global challenge. However, disease management remains difficult. With limited options, there is a need for innovative solutions. The cytokine interleukin-22 (IL-22) has emerged as a possible therapeutic target for fish and has been correlated with protection under pathogen challenge. Plant-based production systems have the potential to effectively manufacture and bring unique efficacy-enhancing features to the aquaculture industry; namely, the advantages of low cost for this commodity market, ready scalability, and reduced environmental impact. Catfish IL-22 produced at significant yield and purity highlights the use of plants as a promising production platform for therapeutic proteins with utility to the aquaculture industry. Purified cfIL-22 shows similar in vitro bioactivity to its mammalian homolog that include increased proliferation of catfish cells highlighting the tissue preservation capabilities associated with this protein. Recombinant cfIL-22 also upregulated expression of genes encoding a tissue repair protein, fibronectin, an antimicrobial peptide, Natural killer lysin-1, and a common innate immune protein, interferon. These findings support plant-made recombinant catfish interleukin-22 as a potential therapeutic for the aquaculture industry and further analysis of this protein for promoting animal health.

Development of diagnostic tools for IBDV detection using plants as bioreactors

Infectious bursal disease virus (IBDV) is the etiological agent of an immunosuppressive and highly contagious disease that affects young birds, thus causing important economic losses in the poultry industry. Multimeric particles with different architectures based on the capsid protein VP2 have been widely produced for different purposes. We hereby show the production and easy recovery of IBDV subviral particles (SVP) from transiently transformed Nicotiana benthamiana. The SVP, which were observed by electronic microscopy, proved to be antigenically and immunogenically similar to the virion. Indeed, anti-IBDV antibodies from samples of infected birds recognized these SVP and, when injected intramuscularly, these subviral particles also evoked a humoral immune response in chickens. We developed an in-house ELISA using SVP as coating reagent that demonstrated to be highly accurate and in good agreement with a commercial ELISA. This study demonstrates that the recombinant antigen generated and the technology used to produce it are suitable for developing a diagnostic tool against Infectious bursal disease.