Plant-based, adjuvant-free, potent multivalent vaccines for avian influenza virus via Lactococcus surface display

Production of active human iduronate-2-sulfatase (IDS) enzyme in Nicotiana benthamiana

Many strategies have been developed to produce high levels of biologically active recombinant proteins in plants for biopharmaceutical purposes. However, the production of an active form of human iduronate-2-sulfatase (hIDS) for the treatment of Hunter syndrome by enzyme replacement therapy (ERT) is challenging due to the requirement for cotranslational modification by a formylglycine-producing enzyme encoded by sulfatase modifying factor 1 (hSUMF1) at the Cys84 residue, which converts it to C(alpha)-formylglycine. In this study, we have shown that hIDS can be highly expressed in N. benthamiana by using different constructs. Among them, BiP-GB1-L-dCBD1-2L-8xHis-L-6xHis-3L-EK-hIDS-HDEL (GB1-CBD1-hIDS) showed a high expression level when transiently co-expressed with the turnip crinkle virus gene silencing suppressor P38 and GB1-fused human calreticulin (GB1-CRT1) as a folding enhancer. The hSUMF1 was co-expressed with hIDS for cotranslational modification. The full-length recombinant proteins were purified using Ni2+-NTA affinity resin followed by enterokinase treatment to obtain tag-free hIDS. The N-terminal fragment was removed using microcrystalline cellulose (MCC) beads. The purified active form of hIDS can successfully cleave the sulfate group from an artificial substrate, 4-nitrocatechol sulfate, at a similar level to commercial hIDS expressed in animal cells. These results suggest that plants could be a promising platform for the production of recombinant hIDS.

Advances in Subcellular Accumulation Design for Recombinant Protein Production in Tobacco

Plants and their use as bioreactors for the generation of recombinant proteins have become one of the hottest topics in the field of Plant Biotechnology and Plant Synthetic Biology. Plant bioreactors offer superior engineering potential compared to other types, particularly in the realm of subcellular accumulation strategies for increasing production yield and quality. This review explores established and emerging strategies for subcellular accumulation of recombinant proteins in tobacco bioreactors, highlighting recent advancements in the field. Additionally, the review provides reference to the crucial initial step of selecting an optimal subcellular localization for the target protein, a design that substantially impacts production outcomes.

Lactobacilli-derived adjuvants combined with immunoinformatics-driven multi-epitope antigens based approach protects against Clostridium perfringens in a mouse model

Clostridium perfringens is ubiquitously distributed and capable of secreting toxins, posing a significant threat to animal health. Infections caused by Clostridium perfringens, such as Necrotic Enteritis (NE), result in substantial economic losses to the livestock industry annually. However, there is no effective commercial vaccine available. Hence, we set out to propose an effective approach for multi-epitope subunit vaccine construction utilizing biomolecules. We utilized immunoinformatics to design a novel multi-epitope antigen against C. perfringens (CPMEA). Furthermore, we innovated novel bacterium-like particles (BLPs) through thermal acid treatment of various Lactobacillus strains and selected BLP23017 among them. Then, we detailed the structure of CPMEA and BLPs and utilized them to prepare a multi-epitope vaccine. Here, we showed that our vaccine provided full protection against C. perfringens infection after a single dose in a mouse model. Additionally, BLP23017 notably augmented the secretion of secretory immunoglobulin A (sIgA) and enhanced antibody production. We conclude that our vaccine possess safety and high efficacy, making it an excellent candidate for preventing C. perfringens infection. Moreover, we demonstrate our approach to vaccine construction and the preparation of BLP23017 with distinct advantages may contribute to the prevention of a wider array of diseases and the novel vaccine development.

Proof of concept in utilizing the peptidoglycan skeleton of pathogenic bacteria as antigen delivery platform for enhanced immune response

Subunit vaccines are becoming increasingly important because of their safety and effectiveness. However, subunit vaccines often exhibit limited immunogenicity, necessitating the use of suitable adjuvants to elicit robust immune responses. In this study, we demonstrated for the first time that pathogenic bacteria can be prepared into a purified peptidoglycan skeleton without nucleic acids and proteins, presenting bacterium-like particles (pBLP). Our results showed that the peptidoglycan skeletons screened from four pathogens could activate Toll-like receptor1/2 receptors better than bacterium-like particles from Lactococcus lactis in macrophages. We observed that pBLP was safe in mouse models of multiple ages. Furthermore, pBLP improved the performance of two commercial vaccines in vivo. We confirmed that pBLP successfully loaded antigens onto the surface and proved to be an effective antigen delivery platform with enhanced antibody titers, antibody avidity, balanced subclass distribution, and mucosal immunity. These results indicate that the peptidoglycan skeleton of pathogenic bacteria represents a new strategy for developing subunit vaccine delivery systems.

The Chinese Hamster Ovary Cell-Based H9 HA Subunit Avian Influenza Vaccine Provides Complete Protection against the H9N2 Virus Challenge in Chickens

(1) Background: Avian influenza has attracted widespread attention because of its severe effect on the poultry industry and potential threat to human health. The H9N2 subtype of avian influenza viruses was the most prevalent in chickens, and there are several commercial vaccines available for the prevention of the H9N2 subtype of avian influenza viruses. However, due to the prompt antigenic drift and antigenic shift of influenza viruses, outbreaks of H9N2 viruses still continuously occur, so surveillance and vaccine updates for H9N2 subtype avian influenza viruses are particularly important. (2) Methods: In this study, we constructed a stable Chinese hamster ovary cell line (CHO) to express the H9 hemagglutinin (HA) protein of the major prevalent H9N2 strain A/chicken/Daye/DY0602/2017 with genetic engineering technology, and then a subunit H9 avian influenza vaccine was prepared using the purified HA protein with a water-in-oil adjuvant. (3) Results: The results showed that the HI antibodies significantly increased after vaccination with the H9 subunit vaccine in specific-pathogen-free (SPF) chickens with a dose-dependent potency of the immunized HA protein, and the 50 μg or more per dose HA protein could provide complete protection against the H9N2 virus challenge. (4) Conclusions: These results indicate that the CHO expression system could be a platform used to develop the subunit vaccine against H9 influenza viruses in chickens.

Bacterium-like particles derived from probiotics: progress, challenges and prospects

Bacterium-like particles (BLPs) are hollow peptidoglycan particles obtained from food-grade Lactococcus lactis inactivated by hot acid. With the advantage of easy preparation, high safety, great stability, high loading capacity, and high mucosal delivery efficiency, BLPs can load and display proteins on the surface with the help of protein anchor (PA), making BLPs a proper delivery system. Owning to these features, BLPs are widely used in the development of adjuvants, vaccine carriers, virus/antigens purification, and enzyme immobilization. This review has attempted to gather a full understanding of the technical composition, characteristics, applications. The mechanism by which BLPs induces superior adaptive immune responses is also discussed. Besides, this review tracked the latest developments in the field of BLPs, including Lactobacillus-derived BLPs and novel anchors. Finally, the main limitations and proposed breakthrough points to further enhance the immunogenicity of BLPs vaccines were discussed, providing directions for future research. We hope that further developments in the field of antigen delivery of subunit vaccines or others will benefit from BLPs.

An updated review on oral protein-based antigen vaccines efficiency and delivery approaches: a special attention to infectious diseases

Various infectious agents affect human health via the oral entrance. The majority of pathogens lack approved vaccines. Oral vaccination is a convenient, safe and cost-effective approach with the potential of provoking mucosal and systemic immunity and maintaining individual satisfaction. However, vaccines should overcome the intricate environment of the gastrointestinal tract (GIT). Oral protein-based antigen vaccines (OPAVs) are easier to administer than injectable vaccines and do not require trained healthcare professionals. Additionally, the risk of needle-related injuries, pain, and discomfort is eliminated. However, OPAVs stability at environmental and GIT conditions should be considered to enhance their stability and facilitate their transport and storage. These vaccines elicit the local immunity, protecting GIT, genital tract and respiratory epithelial surfaces, where numerous pathogens penetrate the body. OPAVs can also be manipulated (such as using specific incorporated ligand and receptors) to elicit targeted immune response. However, low bioavailability of OPAVs necessitates development of proper protein carriers and formulations to enhance their stability and efficacy. There are several strategies to improve their efficacy or protective effects, such as incorporation of adjuvants, enzyme inhibitors, mucoadhesive or penetrating devices and permeation enhancers. Hence, efficient delivery of OPAVs into GIT require proper delivery systems mainly including smart target systems, probiotics, muco-adhesive carriers, lipid- and plant-based delivery systems and nano- and microparticles.

Protection against genotype VII Newcastle disease virus by a mucosal subunit vaccination based on bacterium-like particles bearing the F or HN antigen

Genotype VII Newcastle disease viruses (NDV) are still epidemic in many countries in chicken and waterfowl despite intensive vaccination with conventional live and inactivated vaccines. Here, we developed an effective mucosal subunit vaccine based on a bacterium-like particles (BLPs) delivery platform derived from Lactococcus lactis. The NDV protective antigen F or HN fused protein anchor (PA) was expressed by recombinant baculovirus and loaded on the surface of BLPs, resulting in BLPs-F and BLPs-HN, respectively. Efficient uptake of BLPs-F/HN by antigen-presenting cells activated the innate immune system depending mainly on the combination of chicken TLR2 type 1 (chTLR2t1) and chicken TLR1 type 1 (chTLR1t1) was observed. Delivered intranasally, BLPs-F, BLPs-HN, or BLPs-F/HN (a mixture containing equal amounts of BLPs-F and BLPs-HN) elicited robust local NDV-specific SIgA in the trachea as well as systemic neutralizing antibody and a mixed Th1/Th2 immune response in chickens. Notably, BLPs-F/HN provided as high as 90 % protection rate against intranasal challenge with a lethal dose of virulent genotype VII NDV NA-1 strain. These data indicate that this BLP-based subunit vaccine has the potential to be a novel mucosal vaccine against genotype VII NDV infection.

Assembly of Human Papillomavirus 16 L1 Protein in Nicotiana benthamiana Chloroplasts into Highly Immunogenic Virus-Like Particles

Infection with human papillomavirus (HPV) can cause cervical cancers in women, and vaccination against the virus is one of most effective ways to prevent these cancers. Two vaccines made of virus-like particles (VLPs) of HPV L1 proteins are currently commercially available. However, these HPV vaccines are highly expensive, and thus not affordable for women living in developing countries. Therefore, great demand exists to produce a cost-effective vaccine. Here, we investigate the production of self-assembled HPV16 VLPs in plants. We generated a chimeric protein composed of N-terminal 79 amino acid residues of RbcS as a long-transit peptide to target chloroplasts, the SUMO domain, and HPV16 L1 proteins. The chimeric gene was expressed in plants with chloroplast-targeted bdSENP1, a protein that specifically recognizes the SUMO domain and cleaves its cleavage site. This co-expression of bdSENP1 led to the release of HPV16 L1 from the chimeric proteins without any extra amino acid residues. HPV16 L1 purified by heparin chromatography formed VLPs that mimicked native virions. Moreover, the plant-produced HPV16 L1 VLPs elicited strong immune responses in mice without adjuvants. Thus, we demonstrated the cost-effective production of HPV16 VLPs in plants.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12374-023-09393-6.

Plant-made pharmaceuticals: exploring studies for the production of recombinant protein in plants and assessing challenges ahead

The production of pharmaceutical compounds in plants is attracting increasing attention, as plant-based systems can be less expensive, safer, and more scalable than mammalian, yeast, bacterial, and insect cell expression systems. Here, we review the history and current status of plant-made pharmaceuticals. Producing pharmaceuticals in plants requires pairing the appropriate plant species with suitable transformation technology. Pharmaceuticals have been produced in tobacco, cereals, legumes, fruits, and vegetables via nuclear transformation, chloroplast transformation, transient expression, and transformation of suspension cell cultures. Despite this wide range of species and methods used, most such efforts have involved the nuclear transformation of tobacco. Tobacco readily generates large amounts of biomass, easily accepts foreign genes, and is amenable to stable gene expression via nuclear transformation. Although vaccines, antibodies, and therapeutic proteins have been produced in plants, such pharmaceuticals are not readily utilized by humans due to differences in glycosylation, and few such compounds have been approved due to a lack of clinical data. In addition, achieving an adequate immune response using plant-made pharmaceuticals can be difficult due to low rates of production compared to other expression systems. Various technologies have recently been developed to help overcome these limitations; however, plant systems are expected to increasingly become widely used expression systems for recombinant protein production.

SARS-CoV-2 spike trimer vaccine expressed in Nicotiana benthamiana adjuvanted with Alum elicits protective immune responses in mice

The ongoing coronavirus disease 2019 (COVID-19) pandemic has spurred rapid development of vaccines as part of the public health response. However, the general strategy used to construct recombinant trimeric severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) proteins in mammalian cells is not completely adaptive to molecular farming. Therefore, we generated several constructs of recombinant S proteins for high expression in Nicotiana benthamiana. Intramuscular injection of N. benthamiana-expressed S_ct vaccine (NS_ct Vac) into Balb/c mice elicited both humoral and cellular immune responses, and booster doses increased neutralizing antibody titres. In human angiotensin-converting enzyme knock-in mice, two doses of NS_ct Vac induced anti-S and neutralizing antibodies, which cross-neutralized Alpha, Beta, Delta and Omicron variants. Survival rates after lethal challenge with SARS-CoV-2 were up to 80%, without significant body weight loss, and viral titres in lung tissue fell rapidly, with no infectious virus detectable at 7-day post-infection. Thus, plant-derived NS_ct Vac could be a candidate COVID-19 vaccine.

Production of Recombinant Active Human TGFβ1 in Nicotiana benthamiana

The production of recombinant proteins in plant systems is receiving wider attention. Indeed, various plant-produced pharmaceuticals have been shown to be biologically active. However, the production of human growth factors and cytokines in heterologous systems is still challenging because they often act as complex forms, such as homo- or hetero-dimers, and their production is tightly regulated in vivo. In this study, we demonstrated that the mature form of human TGFβ1 produced and purified from Nicotiana benthamiana shows biological activity in animal cells. To produce the mature form of TGFβ1, various recombinant genes containing the mature form of TGFβ1 were generated and produced in N. benthamiana. Of these, a recombinant construct, BiP:M:CBM3:LAP[C33S]:EK:TGFβ1, was expressed at a high level in N. benthamiana. Recombinant proteins were one-step purified using cellulose-binding module 3 (CBM3) as an affinity tag and microcrystalline cellulose (MCC) beads as a matrix. The TGFβ1 recombinant protein bound on MCC beads was proteolytically processed with enterokinase to separate mature TGFβ1. The mature TGFβ1 still associated with Latency Associated Protein, [LAP(C33S)] that had been immobilized on MCC beads was released by HCl treatment. Purified TGFβ1 activated TGFβ1-mediated signaling in the A549 cell line, thereby inducing phosphorylation of SMAD-2, the expression of ZEB-2 and SNAIL1, and the formation of a filopodia-like structure. Based on these results, we propose that active mature TGFβ1, one of the most challenging growth factors to produce in heterologous systems, can be produced from plants at a high degree of purity via a few steps.

The B1 Domain of Streptococcal Protein G Serves as a Multi-Functional Tag for Recombinant Protein Production in Plants

Plants have long been considered a cost-effective platform for recombinant production. A recently recognized additional advantage includes the low risk of contamination of human pathogens, such as viruses and bacterial endotoxins. Indeed, a great advance has been made in developing plants as a "factory" to produce recombinant proteins to use for biopharmaceutical purposes. However, there is still a need to develop new tools for recombinant protein production in plants. In this study, we provide data showing that the B1 domain of Streptococcal protein G (GB1) can be a multi-functional domain of recombinant proteins in plants. N-terminal fusion of the GB1 domain increased the expression level of various target proteins ranging from 1.3- to 3.1-fold at the protein level depending on the target proteins. GB1 fusion led to the stabilization of the fusion proteins. Furthermore, the direct detection of GB1-fusion proteins by the secondary anti-IgG antibody eliminated the use of the primary antibody for western blot analysis. Based on these data, we propose that the small GB1 domain can be used as a versatile tag for recombinant protein production in plants.