Optimization of Ammonium Sulfate Concentration for Purification of Colorectal Cancer Vaccine Candidate Recombinant Protein GA733-FcK Isolated from Plants

Gn protein expressed in plants for diagnosis of severe fever with thrombocytopenia syndrome virus

Severe fever with thrombocytopenia syndrome virus (SFTSV) causes the highly fatal disease in humans. To facilitate diagnosis, the native form of subunit glycoprotein (Gn), a prime target for potential vaccines and therapies, was produced in Nicotiana benthamiana using a Bamboo mosaic virus-based vector system. By fusion with secretory signal tags, SSExt, derived from the extension protein, and the (SP)10 motif, the yield of the recombinant Gn (rGn) was remarkably increased to approximately 7 mg/kg infiltrated leaves. Ultimately, an rGn-based ELISA was successfully established for the detection of SFTSV-specific antibodies in serum samples from naturally infected monkeys. As validated with the reference method, the specificity and sensitivity of rGn-ELISA were 94% and 96%, respectively. In conclusion, utilizing well-suited fusion tags facilitates rGn production and purification in substantial quantities while preserving its antigenic properties. The rGn-ELISA, characterized by its commendable sensitivity and specificity could serve as a viable alternative diagnostic method for assessing SFTSV seroprevalence. KEY POINTS: • SFTSV Gn, fused with secretory signal tags, was expressed by the BaMV-based vector. • The plant fusion tags increased expression levels and eased the purification of rGn. • The rGn-ELISA was established and validated; its specificity and sensitivity > 94%.

Expression of BSN314 lysozyme genes in Escherichia coli BL21: a study to demonstrate microbicidal and disintegarting potential of the cloned lysozyme

This study is an extension of our previous studies in which the lysozyme was isolated and purified from Bacillus subtilis BSN314 (Naveed et al., 2022; Naveed et al., 2023). In this study, the lysozyme genes were cloned into the E. coli BL21. For the expression of lysozyme in E. coli BL21, two target genes, Lyz-1 and Lyz-2, were ligated into the modified vector pET28a to generate pET28a-Lyz1 and pET28a-Lyz2, respectively. To increase the production rate of the enzyme, 0.5-mM concentration of IPTG was added to the culture media and incubated at 37 °C and 220 rpm for 24 h. Lyz1 was identified as N-acetylmuramoyl-L-alanine amidase and Lyz2 as D-alanyl-D-alanine carboxypeptidase. They were purified by multi-step methodology (ammonium sulfate, precipitation, dialysis, and ultrafiltration), and antimicrobial activity was determined. For Lyz1, the lowest MIC/MBC (0.25 μg/mL; with highest ZOI = 22 mm) were recorded against Micrococcus luteus, whereas the highest MIC/MBC with lowest ZOI were measured against Salmonella typhimurium (2.50 μg /mL; with ZOI = 10 mm). As compared with Aspergillus oryzae (MIC/MFC; 3.00 μg/mL), a higher concentration of lysozyme was required to control the growth of Saccharomyces cerevisiae (MIC/MFC; 50 μg/mL). Atomic force microscopy (AFM) was used to analyze the disintegrating effect of Lyz1 on the cells of selected Gram-positive bacteria, Gram-negative bacteria, and yeast. The AFM results showed that, as compared to Gram-negative bacteria, a lower concentration of lysozyme (Lyz1) was required to disintegrate the cell of Gram-positive bacteria.

Development of a tag-free plant-made interferon gamma production system with improved therapeutic efficacy against viruses

Plants offer a promising platform for cost-effective production of biologically active therapeutic glycoproteins. In previous studies, we have developed a plant expression system based on Bamboo mosaic virus (BaMV) by incorporating secretory signals and an affinity tag, which resulted in notably enhanced yields of soluble and secreted fusion glycoproteins (FGs) in Nicotiana benthamiana. However, the presence of fusion tags on recombinant glycoproteins is undesirable for biomedical applications. This study aimed to develop a refined expression system that can efficiently produce tag-free glycoproteins in plants, with enhanced efficacy of mature interferon gamma (mIFNγ) against viruses. To accommodate the specific requirement of different target proteins, three enzymatically or chemically cleavable linkers were provided in this renovated BaMV-based expression system. We demonstrated that Tobacco etch virus (TEV) protease could process the specific cleavage site (LTEV) of the fusion protein, designated as SSExtHis(SP)10LTEV-mIFNγ, with optimal efficiency under biocompatible conditions to generate tag-free mIFNγ glycoproteins. The TEV protease and secretory-affinity tag could be effectively removed from the target mIFNγ glycoproteins through Ni2+-NTA chromatography. In addition, the result of an antiviral assay showed that the tag-free mIFNγ glycoproteins exhibited enhanced biological properties against Sindbis virus, with comparable antiviral activity of the commercialized HEK293-expressed hIFNγ. Thus, the improved BaMV-based expression system developed in this study may provide an alternative strategy for producing tag-free therapeutic glycoproteins intended for biomedical applications.

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.

In vitro assembly of chimeric virus-like particles composed of a porcine circovirus 2b capsid protein and a B-cell epitope of infectious bursal disease virus

OBJECTIVES

To develop a method for in vitro assembly of recombinant proteins expressed in E. coli into chimeric virus-like particles (cVLPs).

RESULTS

A fusion protein (Bepi-Cap-A) between capsid protein (Cap) of PCV2b and B cell epitope (Bepi) of IBDV was expressed in E. Coli, and purified. For assembling them into cVLPs (Bepi-Cap-VLP), the Bepi-Cap-A was suspended in buffer C [0.03% ("%" stands for "v/v" unless otherwise indicated) polyethylene glycol, 0.4 M Tris, 10 mM β-mercaptoethanol, 5% glycerol, 0.02% (w/v) gellan gum, 0.1 M glycine, 0.03% Tween 80, 500 mM NaCl], and incubated. After centrifugation, the pellet was resuspended in buffer D [50 mM Na₂HPO₄, 50 mM NaH₂PO₄, 0.01% (w/v) gellan gum, 0.05 mM EDTA, 500 mM NaCl, 0.03% Tween 80, pH 6.5], and then dialyzed against dialysis buffer (50 mM Na₂HPO₄, 50 mM NaH₂PO₄, 500 mM NaCl, 0.03% Tween 80, pH 6.5). The procedure resulted in typical and immunogenic Bepi-Cap-VLP.

CONCLUSIONS

The data provide a method which is feasible for in vitro assembly of recombinant proteins into chimeric virus-like particles.

Simple Methods for the Preparation of Colloidal Chitin, Cell Free Supernatant and Estimation of Laminarinase

Colloidal chitin (CC) is a common substrate used in research work involving chitin-active enzymes (chitinases). Cell free supernatant (CFS) is prepared from fermented broth. Preparation of CC and CFS usually involve large amounts of liquid, which must be separated from the solids. This necessitates the use of a large volume centrifugation facility, which may not be accessible to everyone. Filtration is a viable alternative to centrifugation, and several filter elements are described in the literature. Each of those elements has its own set of disadvantages like non-availability, high cost, fragility, and non-reusability. Here we describe the use of lab coat clothing material (LCCM) for the preparation of CC and CFS. For filtration purposes, the LCCM was found to be functional, rugged, reusable, and cost-effective. Also described here is a new method for the estimation of laminarinase using a laminarin infused agarose gel plate. An easily available optical fabric brightener (OFB) was used as a stain for the agarose plate. The laminarin infused agarose plate assay is simple, inexpensive, and was found to be impervious to high amounts of ammonium sulfate (AS) in enzyme precipitates.

Production of a Bacteria-like Particle Vaccine Targeting Rock Bream (Oplegnathus fasciatus) Iridovirus Using Nicotiana benthamiana

Viral diseases are extremely widespread infections that change constantly through mutations. To produce vaccines against viral diseases, transient expression systems are employed, and Nicotiana benthamiana (tobacco) plants are a rapidly expanding platform. In this study, we developed a recombinant protein vaccine targeting the major capsid protein (MCP) of iridovirus fused with the lysine motif (LysM) and coiled-coil domain of coronin 1 (ccCor1) for surface display using Lactococcus lactis. The protein was abundantly produced in N. benthamiana in its N-glycosylated form. Total soluble proteins isolated from infiltrated N. benthamiana leaves were treated sequentially with increasing ammonium sulfate solution, and recombinant MCP mainly precipitated at 40-60%. Additionally, affinity chromatography using Ni-NTA resin was applied for further purification. Native structure analysis using size exclusion chromatography showed that recombinant MCP existed in a large oligomeric form. A minimum OD₆₀₀ value of 0.4 trichloroacetic acid (TCA)-treated L. lactis was required for efficient recombinant MCP display. Immunogenicity of recombinant MCP was assessed in a mouse model through enzyme-linked immunosorbent assay (ELISA) with serum-injected recombinant MCP-displaying L. lactis. In summary, we developed a plant-based recombinant vaccine production system combined with surface display on L. lactis.

Plant-based vaccines and cancer therapy: Where are we now and where are we going?

Therapeutic vaccines are an effective approach in cancer therapy for treating the disease at later stages. The Food and Drug Administration (FDA) recently approved the first therapeutic cancer vaccine, and further studies are ongoing in clinical trials. These are expected to result in the future development of vaccines with relatively improved efficacy. Several vaccination approaches are being studied in pre-clinical and clinical trials, including the generation of anti-cancer vaccines by plant expression systems.This approach has advantages, such as high safety and low costs, especially for the synthesis of recombinant proteins. Nevertheless, the development of anti-cancer vaccines in plants is faced with some technical obstacles.Herein, we summarize some vaccines that have been used in cancer therapy, with an emphasis on plant-based vaccines.

Effect of leaf position and days post-infiltration on transient expression of colorectal cancer vaccine candidate proteins GA733-Fc and GA733-FcK in Nicotiana benthamiana plant

Immunization with thetumor-associated antigen GA733 glycoprotein, which is highly expressed in colorectal cancer, is considered to be a promising strategy for cancer prevention and treatment. We cloned a fusion gene of GA733 and immunoglobulin Fc fragment (GA733-Fc), and that of GA733-Fc and an endoplasmic reticulum retention motif (GA733-FcK) into the Cowpea mosaic virus (CPMV)-based transient plant expression vector, pEAQ-HT. Agrobacterium tumefaciens (LBA4404) transformed with the vectors pEAQ-HT-GA733-Fc and pEAQ-HT-GA733-FcK was infiltrated into the leaves of Nicotiana benthamiana plants. To optimize harvesting of leaf to express therapeutic glycoproteins both spatially and temporally, protein expression levels at various leaf positions (top, middle, and base) and days post-infiltration (dpi) were investigated. The GA733-Fc and GA733-FcK genes were detected in leaves at 1–10 dpi using PCR. As assessed by western blot, GA733-Fc and GA733-FcK were expressed at the highest levels in the top leaf position at 5 dpi, and GA733-FcK was expressed more than GA733-Fc. The proteins were successfully purified from infiltrated N. benthamiana leaves using protein A affinity chromatography. ELISA verified that an anti-GA733 antibody recognized both purified proteins. Thus, a functional GA733-Fc colorectal cancer vaccine protein can be transiently expressed using a CPMV virus-based vector, with an optimized expression time and leaf position post-infiltration.

A set of simple methods for detection and extraction of laminarinase

A carefully designed ammonium sulfate precipitation will simplify extraction of proteins and is considered to be a gold standard among various precipitation methods. Therefore, optimization of ammonium sulfate precipitation can be an important functional step in protein purification. The presence of high amounts of ammonium sulphate precludes direct detection of many enzymatically active proteins including reducing sugar assays (e.g. Nelson-Somogyi, Reissig and 3,5-dinitrosalicylic acid methods) for assessing carbohydrases (e.g. laminarinase (β (1-3)-glucanohydrolase), cellulases and chitinases). In this study, a simple method was developed using laminarin infused agarose plate for the direct analysis of the ammonium sulphate precipitates from Streptomyces rimosus AFM-1. The developed method is simple and convenient that can give accurate results even in presence of ammonium sulfate in the crude precipitates. Laminarin is a translucent substrate requiring the use of a stain to visualize the zones of hydrolysis in a plate assay. A very low-cost and locally available fluorescent optical fabric brightener Tinopal CBS-X has been used as a stain to detect the zones of hydrolysis. We also report simple methods to prepare colloidal chitin and cell free supernatant in this manuscript.

Optimization of the human colorectal carcinoma antigen GA733-2 production in tobacco plants

The colorectal carcinoma-associated protein GA733-2 is one of the representative candidate protein for the development of plant-derived colorectal cancer vaccine. Despite of its significant importance for colorectal vaccine development, low efficiency of GA733-2 production limits its wide applications. To improve productivity of GA733-2 in plants, we here tested multiple factors that affect expression of recombinant GA733-2 (rGA733-2) and rGA733 fused to fragment crystallizable (Fc) domain (rGA733-Fc) protein. The rGA733-2 and rGA733-Fc proteins were highly expressed when the pBINPLUS vector system was used for transient expression in tobacco plants. In addition, the length of interval between rGA733-2 and left border of T-DNA affected the expression of rGA733 protein. Transient expression analysis using various combinations of Agrobacterium tumefaciens strains (C58C1, LBA4404, and GV3101) and tobacco species (Nicotiana tabacum cv. Xanthi nc and Nicotiana benthamiana) revealed that higher accumulation of rGA733-2 and rGA733-Fc proteins were obtained by combination of A. tumefaciens LBA4404 and Nicotiana benthamiana. Transgenic plants generated by introduction of the rGA733-2 and rGA733-Fc expression cassettes also significantly accumulated corresponding recombinant proteins. Bioactivity and stability of the plant-derived rGA733 and rGA733-Fc were evaluated by further in vitro assay, western blot and N-glycosylation analysis. Collectively, we here suggest the optimal condition for efficient production of functional rGA733-2 protein in tobacco system.

Fusion of a Novel Native Signal Peptide Enhanced the Secretion and Solubility of Bioactive Human Interferon Gamma Glycoproteins in Nicotiana benthamiana Using the Bamboo Mosaic Virus-Based Expression System

Plant viruses may serve as expression vectors for the efficient production of pharmaceutical proteins in plants. However, the downstream processing and post-translational modifications of the target proteins remain the major challenges. We have previously developed an expression system derived from Bamboo mosaic virus (BaMV), designated pKB19, and demonstrated its applicability for the production of human mature interferon gamma (mIFNγ) in Nicotiana benthamiana. In this study, we aimed to enhance the yields of soluble and secreted mIFNγ through the incorporation of various plant-derived signal peptides. Furthermore, we analyzed the glycosylation patterns and the biological activity of the mIFNγ expressed by the improved pKB19 expression system in N. benthamiana. The results revealed that the fusion of a native N. benthamiana extensin secretory signal (SS^Ext) to the N-terminal of mIFNγ (designated SS^Ext mIFNγ) led to the highest accumulation level of protein in intracellular (IC) or apoplast washing fluid (AWF) fractions of N. benthamiana leaf tissues. The addition of 10 units of 'Ser-Pro' motifs of hydroxyproline-O-glycosylated peptides (HypGPs) at the C-terminal end of SS^Ext mIFNγ (designated SS^Ext mIFNγ(SP)₁₀) increased the solubility to nearly 2.7- and 1.5-fold higher than those of mIFNγ and SS^Ext mIFNγ, respectively. The purified soluble SS^Ext mIFNγ(SP)₁₀ protein was glycosylated with abundant complex-type N-glycan attached to residues N⁵⁶ and N¹²⁸, and exhibited biological activity against Sindbis virus and Influenza virus replication in human cell culture systems. In addition, suspension cell cultures were established from transgenic N. benthamiana, which produced secreted SS^Ext mIFNγ(SP)₁₀ protein feasible for downstream processing. These results demonstrate the applicability of the BaMV-based vector systems as a useful alternative for the production of therapeutic proteins, through the incorporation of appropriate fusion tags.

Expression of Colorectal Cancer Antigenic Protein Fused to IgM Fc in Chinese Cabbage (Brassica rapa)

The epithelial cell adhesion molecule (EpCAM) is a tumor-associated antigen and a potential target for tumor vaccine. The EpCAM is a cell-surface glycoprotein highly expressed in colorectal carcinomas. The objective of the present study is to develop an edible vaccine system through Agrobacterium-mediated transformation in Chinese cabbage (Brassica rapa). For the transformation, two plant expression vectors containing genes encoding for the EpCAM recombinant protein along with the fragment crystallizable (Fc) region of immunoglobulin M (IgM) and Joining (J)-chain tagged with the KDEL endoplasmic reticulum retention motif (J-chain K) were constructed. The vectors were successfully transformed and expressed in the Chinese cabbage individually using Agrobacterium. The transgenic Chinese cabbages were screened using genomic polymerase chain reaction (PCR) in T₀ transgenic plant lines generated from both transformants. Similarly, the immunoblot analysis revealed the expression of recombinant proteins in the transformants. Further, the T₁ transgenic plants were generated by selfing the transgenic plants (T₀) carrying EpCAM-IgM Fc and J-chain K proteins, respectively. Subsequently, the T₁ plants generated from EpCAM-IgM Fc and J-chain K transformants were crossed to generate F₁ plants carrying both transgenes. The presence of both transgenes was validated using PCR in the F₁ plants. In addition, the expression of Chinese cabbage-derived EpCAM-IgM Fc × J-chain K was evaluated using immunoblot and ELISA analyses in the F₁ plants. The outcomes of the present study can be utilized for the development of a potential anti-cancer vaccine candidate using Chinese cabbage.

Expression of a Large Single-Chain 13F6 Antibody with Binding Activity against Ebola Virus-Like Particles in a Plant System

Pathogenic animal and human viruses present a growing and persistent threat to humans worldwide. Ebola virus (EBOV) causes zoonosis in humans. Here, two structurally different anti-Ebola 13F6 antibodies, recognizing the heavily glycosylated mucin-like domain (MLD) of the glycoprotein (GP), were expressed in transgenic Nicotiana tabacum plants and designed as inexpensive and effective diagnostic antibodies against Ebola virus disease (EVD). The first was anti-EBOV 13F6 full size antibody with heavy chain (HC) and light chain (LC) (monoclonal antibody, mAb 13F6-FULL), while the second was a large single-chain (LSC) antibody (mAb 13F6-LSC). mAb 13F6-LSC was constructed by linking the 13F6 LC variable region (VL) with the HC of mAb 13F6-FULL using a peptide linker and extended to the C-terminus using the endoplasmic reticulum (ER) retention motif KDEL. Agrobacterium-mediated plant transformation was employed to express the antibodies in N. tabacum. PCR, RT-PCR, and immunoblot analyses confirmed the gene insertion, transcription, and protein expression of these antibodies, respectively. The antibodies tagged with the KDEL motif displayed high-mannose type N-glycan structures and efficient binding to EBOV-like particles (VLPs). Thus, various forms of anti-EBOV plant-derived mAbs 13F6-FULL and LSC with efficient binding affinity to EBOV VLP can be produced in the plant system.

Expression and in vitro function of anti-cancer mAbs in transgenic Arabidopsis thaliana

The anti-colorectal cancer monoclonal antibody CO17-1A (mAb CO), which recognizes the tumor-associated antigen EpCAM, was expressed in transgenic Arabidopsis plants. PCR and western blot analyses showed the insertion and expression of heavy chain (HC)/HC fused to the KDEL ER retention modif (HCK) and light chain (LC) of mAb CO and mAb CO with HCK (mAb COK) in Arabidopsis transformants. Both plant-derived mAb^P CO and mAb^P COK were purified from a biomass of approximately 1,000 seedlings grown in a greenhouse. In sandwich ELISA, both mAb^P CO showed a slightly higher binding affinity for the target, EpCAM, compared to mAb^M CO. In cell ELISA, both mAbs^P COs showed binding affinity to the human colorectal cancer cell line SW480. Furthermore, mAb^M CO, mAb^P CO, and mAb^P COK exhibited dose and time-dependent regression effects on SW480 cells in vitro. In summation, both mAb^P CO and mAb^P COK, expressed in Arabidopsis, recognized the target antigen EpCAM and showed anti-proliferative activity against human colorectal cancer cells.

Purification of plant-derived anti-virus mAb through optimized pH conditions for coupling between protein A and epoxy-activated beads

The main goal of this research was to determine optimum pH conditions for coupling between protein A and epoxy-activated Sepharose beads for purification of monoclonal antibodies (mAbs) expressed in plants. To confirm the effect of pH conditions on purification efficacy, epoxy-activated agarose beads were coupled to protein A under the pH conditions of 8.5, 9.5, 10.5, and 11.5 (8.5R, 9.5R, 10.5R, and 11.5R, respectively). A total of 300 g of fresh leaf tissue of transgenic Arabidopsis expressing human anti-rabies mAb (mAb^P) SO57 were harvested to isolate the total soluble protein (TSP). An equal amount of TSP solution was applied to five resin groups including commercial protein A resin (GR) as a positive control. The modified 8.5R, 9.5R, 10.5R, and 11.5R showed delayed elution timing compared to the GR control resin. Nano-drop analysis showed that the total amount of purified mAb^PSO57 mAbs from 60 g of fresh leaf mass were not significantly different among 8.5R (400 μg), 9.5R (360 μg), 10.5R (380 μg), and GR (350 μg). The 11.5R (25 μg) had the least mAb^PSO57. SDS-PAGE analysis showed that the purity of mAb^PSO57 was not significantly different among the five groups. Rapid fluorescent focus inhibition tests revealed that virus-neutralizing efficacies of purified mAb^PSO57 from all the five different resins including the positive control resin were similar. Taken together, both pH 8.5 and 10.5 coupling conditions with high recovery rate should be optimized for purification of mAb^PSO57 from transgenic Arabidopsis plant, which will eventually reduce down-stream cost required for mAb production using the plant system.

Endoplasmic reticulum retention motif fused to recombinant anti-cancer monoclonal antibody (mAb) CO17-1A affects mAb expression and plant stress response

The endoplasmic reticulum (ER) is the main site of protein synthesis, folding, and secretion to other organelles. The capacity of the ER to process proteins is limited, and excessive accumulation of unfolded and misfolded proteins can induce ER stress, which is associated with plant diseases. Here, a transgenic Arabidopsis system was established to express anti-cancer monoclonal antibodies (mAbs) that recognize the tumor-associated antigen GA733-2. Monoclonal antibody (mAb) CO17-1A recognize a tumor-associated epitope expressed on the colorectal cancer cell surface. The ER retention Lys-Asp-Glu-Leu (KDEL) motif sequence was added to the C-terminus of the heavy chain to retain anti-colorectal cancer mAbs in the ER, consequently boosting mAb production. Agrobacterium-mediated floral dip transformation was used to generate T₁ transformants, and homozygous T₄ seeds obtained from transgenic Arabidopsis plants expressing anti-colorectal cancer mAbs were used to confirm the physiological effects of KDEL tagging. Germination rates were not significantly different between both plants expressing mAb CO without KDEL mAb CO (CO plant) and mAb CO with KDEL mAb COK (COK plant). However, COK plants primary root lengths were shorter than those of CO plants and non-transgenic Arabidopsis plants in in vitro media. Most ER stress-related genes, with the exception of bZIP28 and IRE1a, were upregulated in COK plants compared to CO plants. Western blot and SDS-PAGE analyses showed that COK plants exhibited up to five times higher expression and mAb amounts than plants. Enhanced expression in mAb COK plants was confirmed by immunohistochemical analyses. mAb COK was distributed across most of the area of leaf tissues, whereas mAb CO was mainly distributed in extracellular areas. Surface plasmon resonance analyses revealed that mAb CO and mAb COK possessed equivalent or slightly better binding activities to antigen EpCAM compared to a commercially available parental antibody. N-glycosylation analysis showed that mAb CO had plant specific residues whereas mAb COK mainly showed an oligo-mannose N-glycan structure without the plant specific glycan residues. In this study, the reduction of plant growth and biomass induced by ER retention signal peptide might be only in in vitro conditions, and thus should be carefully considered for the initial screening for transgenic lines on culture media. Taken together, nevertheless the fusion of ER retention signal peptide is an effective approach for enhancing the yields of recombinant proteins in vivo.

Production of Recombinant Anti-Cancer Vaccines in Plants

Plant expression systems have been developed to produce anti-cancer vaccines. Plants have several advantages as bioreactors for the production of subunit vaccines: they are considered safe, and may be used to produce recombinant proteins at low production cost. However, several technical issues hinder large-scale production of anti-cancer vaccines in plants. The present review covers design strategies to enhance the immunogenicity and therapeutic potency of anti-cancer vaccines, methods to increase vaccine-expressing plant biomass, and challenges facing the production of anti-cancer vaccines in plants. Specifically, the issues such as low expression levels and plant-specific glycosylation are described, along with their potential solutions.

Expression of a Human Prostatic Acid Phosphatase (PAP)-IgM Fc Fusion Protein in Plants Using In vitro Tissue Subculture

In this study, prostatic acid phosphatase (PAP), which is overexpressed in human prostate cancer cells, was cloned to be fused to the IgM constant fragment (Fc) for enhancing immunogenicity and expressed in transgenic tobacco plants. Then, the transgenic plants were propagated by in vitro tissue subculture. Gene insertion and expression of the recombinant PAP-IgM Fc fusion protein were confirmed in each tested the first, second, and third subculture generations (SG₁, SG₂, and SG₃, respectively). Transcription levels were constantly maintained in the SG_1, SG₂, and SG₃ leaf section (top, middle, and base). The presence of the PAP-IgM Fc gene was also confirmed in each leaf section in all tested subculture generations. RNA expression was confirmed in all subculture generations using real-time PCR and quantitative real-time PCR. PAP-IgM Fc protein expression was confirmed in all leaves of the SG₁, SG₂, and SG₃ recombinant transgenic plants by using quantitative western blotting and chemiluminescence immunoassays. These results demonstrate that the recombinant protein was stably expressed for several generations of in vitro subculture. Therefore, transgenic plants can be propagated using in vitro tissue subculture for the production of recombinant proteins.

The Last Ten Years of Advancements in Plant-Derived Recombinant Vaccines against Hepatitis B

Disease prevention through vaccination is considered to be the greatest contribution to public health over the past century. Every year more than 100 million children are vaccinated with the standard World Health Organization (WHO)-recommended vaccines including hepatitis B (HepB). HepB is the most serious type of liver infection caused by the hepatitis B virus (HBV), however, it can be prevented by currently available recombinant vaccine, which has an excellent record of safety and effectiveness. To date, recombinant vaccines are produced in many systems of bacteria, yeast, insect, and mammalian and plant cells. Among these platforms, the use of plant cells has received considerable attention in terms of intrinsic safety, scalability, and appropriate modification of target proteins. Research groups worldwide have attempted to develop more efficacious plant-derived vaccines for over 30 diseases, most frequently HepB and influenza. More inspiring, approximately 12 plant-made antigens have already been tested in clinical trials, with successful outcomes. In this study, the latest information from the last 10 years on plant-derived antigens, especially hepatitis B surface antigen, approaches are reviewed and breakthroughs regarding the weak points are also discussed.

Plant Recycling for Molecular Biofarming to Produce Recombinant Anti-Cancer mAb

The expression and glycosylation patterns of anti-colorectal cancer therapeutic monoclonal antibody (mAb) CO17-1A recognizing the tumor-associated antigen GA733-2, expressed in human colorectal carcinoma cells, were observed in the leaf and stem tissues of primary (0 cycle), secondary (1 cycle), and tertiary (2 cycle) growths of seedlings obtained from the stem cut of T2 plants. The bottom portion of the stem of T2 seedlings was cut to induce the 1 cycle shoot growth, which was again cut to induce the 2 cycle shoot growth. In the 1 and 2 cycle growths, the periods for floral organ formation (35 days) was shorter than that (100 days) for the 0 cycle growth. The genes of heavy and light chains of mAb CO17-1A existed at the top, middle, and basal portions of the leaves and stem obtained from the 0, 1, and 2 cycle plants. The protein levels in the leaves and stem tissues from the 1 and 2 cycles were similar to those in the tissues from the 0 cycle. The glycosylation level and pattern in the leaf and stem did not alter dramatically over the different cycles. Surface plasmon resonance (SPR) confirmed that mAbs CO17-1A obtained from leaf and stem tissues of the 0, 1, and 2 cycles had similar binding affinity for the GA733-2 antigen. These data suggest that the shoot growth by bottom stem cutting is applicable to speed up the growth of plant biomass expressing anti-colorectal cancer mAb without variation of expression, glycosylation, and functionality.