Use of virus vectors for the expression in plants of active full-length and single chain anti-coronavirus antibodies

Plant-Produced Therapeutic Crizanlizumab Monoclonal Antibody Binds P-Selectin to Alleviate Vaso-occlusive Pain Crises in Sickle Cell Disease

Sickle Cell Disease (SCD) is a severe genetic disorder causing vascular occlusion and pain by upregulating the adhesion molecule P-selectin on endothelial cells and platelets. It primarily affects infants and children, causing chronic pain, circulatory problems, organ damage, and complications. Thus, effective treatment and management are crucial to reduce SCD-related risks. Anti-P-selectin antibody Crizanlizumab (Crimab) has been used to treat SCD. In this study, the heavy and light chain (HC and LC) genes of anti-P-Selectin antibody Crimab were cloned into a plant expression binary vector. The HC gene was under control of the duplicated 35S promoter and nopaline synthase (NOS) terminator, whereas the LC gene was under control of the potato proteinase inhibitor II (PIN2) promoter and PIN2 terminator. Agrobacterium tumefaciens LBA4404 was used to transfer the genes into the tobacco (Nicotiana tabacum cv. Xanthi) plant. In plants the genomic PCR and western blot confirmed gene presence and expression of HC and LC Crimab proteins in the plant, respectively. Crimab was successfully purified from transgenic plant leaf using protein A affinity chromatography. In ELISA, plant-derived Crimab (CrimabP) had similar binding activity to P-selectin compared to mammalian-derived Crimab (CrimabM). In surface plasmon resonance, the KD (dissociation binding constant) and response unit values were lower and higher than CrimabP, respectively. Taken together, these results demonstrate that the transgenic plant can be applied to produce biofunctional therapeutic monoclonal antibody.

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.

Seeds as Economical Production Platform for Recombinant Proteins

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The cost-effective production of high-quality and biologically active recombinant molecules especially proteins is extremely desirable. Seed-based recombinant protein production platforms are considered as superior choice owing to lack of human/animal pathogenic organisms, lack of cold chain requirements for transportation and long-term storage, easy scalability and development of edible biopharmaceuticals in plants with objective to be used in purified or partially processed form is desirable. This review article summarizes the exceptional features of seed-based biopharming and highlights the needs of exploiting it for commercial purposes. Plant seeds offer a perfect production platform for high-value molecules of industrial as well as therapeutic nature owing to lower water contents, high protein storage capacity, weak protease activity and long-term storage ability at ambient temperature. Exploiting extraordinarily high protein accumulation potential, vaccine antigens, antibodies and other therapeutic proteins can be stored without effecting their stability and functionality up to years in seeds. Moreover, ability of direct oral consumption and post-harvest stabilizing effect of seeds offer unique feature of oral delivery of pharmaceutical proteins and vaccine antigens for immunization and disease treatment through mucosal as well as oral route.

Cowpea mosaic virus: the plant virus-based biotechnology workhorse

In the 50 years since it was first described, Cowpea mosaic virus (CPMV) has become one of the most intensely studied plant viruses. Research in the past 15 to 20 years has shifted from studying the underlying genetics and structure of the virus to focusing on ways in which it can be exploited in biotechnology. This work led first to the use of virus particles to present peptides, then to the creation of a variety of replicating virus vectors and finally to the development of a highly efficient protein expression system that does not require viral replication. The circle has been completed by the use of the latter system to create empty particles for peptide presentation and other novel uses. The history of CPMV in biotechnology can be likened to an Ouroborus, an ancient symbol depicting a snake or dragon swallowing its own tail, thus forming a circle.

Virus-specific read-through codon preference affects infectivity of chimeric cucumber green mottle mosaic viruses displaying a dengue virus epitope

A Cucumber green mottle mosaic virus (CGMMV) was used to present a truncated dengue virus type 2 envelope (E) protein binding region from amino acids 379 to 423 (EB4). The EB4 gene was inserted at the terminal end of the CGMMV coat protein (CP) open reading frame (ORF). Read-through sequences of TMV or CGMMV, CAA-UAG-CAA-UUA, or AAA-UAG-CAA-UUA were, respectively, inserted in between the CP and the EB4 genes. The chimeric clones, pRT, pRG, and pCG+FSRTRE, were transcribed into full-length capped recombinant CGMMV transcripts. Only constructs with the wild-type CGMMV read-through sequence yielded infectious viruses following infection of host plant, muskmelon (Cucumis melo) leaves. The ratio of modified to unmodified CP for the read-through expression clone developed was also found to be approximately 1:1, higher than what has been previously reported. It was also observed that infectivity was not affected by differences in pI between the chimera and its wild counterpart. Analysis of recombinant viruses after 21-days-postinculation (dpi) revealed that deletions occurred resulting in partial reversions of the viral population to near wild type and suggesting that this would be the limiting harvest period for obtaining true to type recombinants with this construct.

Cowpea mosaic virus-based systems for the expression of antigens and antibodies in plants

This chapter describes the use of Cowpea mosaic virus-based vectors for the production of foreign proteins such as antigens and antibodies in plants. The systems include vectors based on both full-length and deleted versions of RNA-2. In both cases, the modified RNA-2 is replicated by coinoculation with RNA-1. The constructs based on full-length RNA-2 retain the ability to spread systemically throughout an inoculated plant and the infection can be passaged. The vector based on a deleted version of RNA-2 can stably incorporate larger inserts but lacks the ability to move systemically. However, it has the added advantage of biocontainment. In both cases, vector constructs modified to contain a foreign gene of interest can be delivered by agroinfiltration to obtain transient expression of the foreign protein. If required, the same constructs can also be used for stable nuclear transformation. Both types of vector have proved effective for the production in plants of a diverse range of proteins including antigens and antibodies.

Transient expression of antibodies in plants using syringe agroinfiltration

The improvements in agroinfiltration methods for plant-based transient expression now allow the production of significant amounts of recombinant proteins in a matter of days. While vacuum-based agroinfiltration has been brought to large scale to meet the cost, speed and surge capacity requirements for vaccine and therapeutic production, the more accessible and affordable syringe agroinfiltration procedure still represents a fast and high-yielding approach to recombinant protein production at lab scale. The procedure exemplified here has proven its reproducibility and high-yield capacity for the production of proteins with varying levels of complexity, including monoclonal antibodies.

Viral vectors for production of recombinant proteins in plants

Global demand for recombinant proteins has steadily accelerated for the last 20 years. These recombinant proteins have a wide range of important applications, including vaccines and therapeutics for human and animal health, industrial enzymes, new materials and components of novel nano-particles for various applications. The majority of recombinant proteins are produced by traditional biological "factories," that is, predominantly mammalian and microbial cell cultures along with yeast and insect cells. However, these traditional technologies cannot satisfy the increasing market demand due to prohibitive capital investment requirements. During the last two decades, plants have been under intensive investigation to provide an alternative system for cost-effective, highly scalable, and safe production of recombinant proteins. Although the genetic engineering of plant viral vectors for heterologous gene expression can be dated back to the early 1980s, recent understanding of plant virology and technical progress in molecular biology have allowed for significant improvements and fine tuning of these vectors. These breakthroughs enable the flourishing of a variety of new viral-based expression systems and their wide application by academic and industry groups. In this review, we describe the principal plant viral-based production strategies and the latest plant viral expression systems, with a particular focus on the variety of proteins produced and their applications. We will summarize the recent progress in the downstream processing of plant materials for efficient extraction and purification of recombinant proteins.

Protease activity, self interaction, and small interfering RNA binding of the silencing suppressor p1b from cucumber vein yellowing ipomovirus

The RNA silencing pathway mediated by small interfering RNAs (siRNAs) plays an important antiviral role in eukaryotes. To counteract this defense barrier, a large number of plant viruses express proteins with RNA silencing suppression activity. Recently, it was reported that the ipomovirus Cucumber vein yellowing virus (CVYV), which lacks the typical silencing suppressor of members of the family Potyviridae, i.e., HCPro, has a duplicated P1 coding sequence and that the downstream P1 copy, named P1b, has silencing suppression activity. In this study, we provide experimental evidence that P1b is a serine protease that self-cleaves at its C terminus but that its proteolytic activity is not essential for silencing suppression. In contrast, a putative zinc finger and a conserved basic motif in the N-terminal region of the protein are required for efficient silencing suppression. In vitro gel filtration-fast protein liquid chromatography and in vivo bimolecular fluorescence complementation assays showed that P1b binds itself to form oligomeric structures and that the zinc finger-like motif is essential for the self interaction. Moreover, we observed that CVYV P1b forms complexes with synthetic siRNAs, and this ability correlated with both silencing suppression activity and enhancement of Potato virus X pathogenicity in a mutational analysis. Together, these results suggest that CVYV P1b resembles potyviral HCPro and other viral proteins in interfering RNA silencing by preventing siRNA loading into the RNA-induced silencing complex.

Expression of multiple proteins using full-length and deleted versions of cowpea mosaic virus RNA-2

The use of multiple copies of vectors based on either full-length or deleted versions of cowpea mosaic virus RNA-2 for the production of heteromeric proteins in plants was investigated. Co-infiltration of two full-length RNA-2 constructs containing different marker genes into Nicotiana benthamiana in the presence of RNA-1 showed that the two foreign proteins were efficiently expressed within the same cell in inoculated tissue. Furthermore, the proteins were co-localized to the same subcellular compartments, an essential prerequisite for heteromer formation. However, segregation of two separate RNA-2 molecules, and therefore expression of the two proteins, was observed on systemic spread of the recombinant viruses. Thus, efficient assembly of heteromeric proteins is likely to occur only in inoculated tissue. To determine the optimum approach for expression in inoculated tissue, the heavy and light chains of the blood group-typing immunoglobulin G (IgG) C5-1 were inserted into full-length and deleted versions of RNA-2, and the constructs were agroinfiltrated in the presence of RNA-1. The results obtained showed that full-size IgG molecules accumulated using both approaches, but that the levels were significantly higher when deleted RNA-2 vectors were used. The levels were also greatly enhanced by the inclusion of an endoplasmic reticulum retention signal at the C-terminus of the heavy chain. As the potential benefit of using full-length RNA-2 constructs, the ability to spread systemically, appears to be irrelevant to the production of heteromeric proteins, the use of deleted versions of RNA-2 is clearly advantageous, particularly as they offer the benefit of biocontainment.

Production of vaccines and therapeutic antibodies for veterinary applications in transgenic plants: an overview

During the past two decades, antibodies, antibody derivatives and vaccines have been developed for therapeutic and diagnostic applications in human and veterinary medicine. Numerous species of dicot and monocot plants have been genetically modified to produce antibodies or vaccines, and a number of diverse transformation methods and strategies to enhance the accumulation of the pharmaceutical proteins are now available. Veterinary applications are the specific focus of this article, in particular for pathogenic viruses, bacteria and eukaryotic parasites. We focus on the advantages and remaining challenges of plant-based therapeutic proteins for veterinary applications with emphasis on expression platforms, technologies and economic considerations.

Recombinant dimeric small immunoproteins neutralize transmissible gastroenteritis virus infectivity efficiently in vitro and confer passive immunity in vivo

Small immunoproteins (SIPs) are single-chain molecules comprising the variable regions of an antibody assembled in a single polypeptide (scFv) and joined to the immunoglobulin heavy-chain dimerizing domain. To investigate the potential of these molecules to provide protection against enteric infections when supplied orally, SIPs were generated against Transmissible gastroenteritis virus (TGEV), a highly pathogenic porcine virus. Different variants of TGEV-specific SIPs were created, of ε and α isotypes, by exploiting the dimerizing domains εCH4 and αCH3 of human and swine origin. Transfected cells secreted these recombinant mini-antibodies efficiently, mainly as dimers stabilized covalently by inter-chain disulphide bridges. The specificity and functionality of the recombinant TGEV-specific SIPs were determined by in vitro binding, neutralization and infection-interference assays. The neutralization indices of the TGEV-specific SIPs were all very similar to that of the original TGEV-specific mAb, thus confirming that the immunological properties have been preserved in the recombinant SIPs. In vivo protection experiments on newborn piglets have, in addition, demonstrated a strong reduction of virus titre in infected tissues of animals treated orally with TGEV-specific SIPs. It has therefore been demonstrated that it is possible to confer passive immunization to newborn pigs by feeding them with recombinant SIPs.