Expression, Purification, and Characterization of Recombinant Human α1-Antitrypsin Produced Using Silkworm-Baculovirus Expression System

Production of scFv, Fab, and IgG of CR3022 Antibodies Against SARS-CoV-2 Using Silkworm-Baculovirus Expression System

COVID-19, caused by SARS-CoV-2, is currently spreading around the world and causing many casualties. Antibodies against such emerging infectious diseases are one of the important tools for basic viral research and the development of diagnostic and therapeutic agents. CR3022 is a monoclonal antibody against the receptor binding domain (RBD) of the spike protein (S protein) of SARS-CoV found in SARS patients, but it was also shown to have strong affinity for that of SARS-CoV-2. In this study, we produced large amounts of three formats of CR3022 antibodies (scFv, Fab and IgG) with high purity using a silkworm-baculovirus expression vector system. Furthermore, SPR measurements showed that the affinity of those silkworm-produced IgG antibodies to S protein was almost the same as that produced in mammalian expression system. These results indicate that the silkworm-baculovirus expression system is an excellent expression system for emerging infectious diseases that require urgent demand for diagnostic agents and therapeutic agents.

Two-step purification of tag-free norovirus-like particles from silkworm larvae (Bombyx mori)

Recombinantly expressed VP1 of norovirus self-assembled and formed norovirus-like particles (NoV-LPs). This native VP1 was expressed using the Bombyx mori nucleopolyhedrovirus (BmNPV) expression system in silkworm larva. NoV-LPs were collected from silkworm fat body lysate by density gradient centrifugation. To improve the purity of the NoV-LP, the proteins were further purified using immobilized metal affinity chromatography based on the surface exposed side chain of histidine residues. The additional purification led to a highly purified virus-like particle (VLP). The morphology and size of the purified VLPs were examined using a transmission electron microscope, and dynamic light scattering revealed a monodispersed spherical morphology with a diameter of 34 nm. The purified product had a purity of >90% with a recovery yield of 48.7% (equivalent to 930 μg) from crude lysate, obtained from seven silkworm larvae. In addition, the purified VLP could be recognized by antibodies against GII norovirus in sandwich enzyme-linked immunosorbent assay, which indicated that the silkworm-derived VLP is biologically functional as a NoV-LP in its native state, is structurally correct, and exerts its biological function. Our results suggest that the silkworm-derived NoV-LP may be useful for subsequent applications, such as in a vaccine platform. Moreover, the silkworm-based expression system is known for its robustness, facile up-scalability, and relatively low expense compared to insect cell systems.

Active Human and Murine Tumor Necrosis Factor α Cytokines Produced from Silkworm Baculovirus Expression System

The tumor necrosis factor α (TNFα) has been employed as a promising reagent in treating autoimmunity and cancer diseases. To meet the substantial requirement of TNFα proteins, we report in this study that mature types of recombinant human and murine TNFα proteins are successfully expressed in the baculovirus expression system using silkworm larvae as hosts. The biological activities of purified products were verified in culture murine L929 cells, showing better performance over a commercial Escherichia coli-derived murine TNFα. By comparing the activity of purified TNFα with or without the tag removal, it is also concluded that the overall activity of purified TNFα cytokines could be further improved by the complete removal of C-terminal fusion tags. Collectively, our current attempt demonstrates an alternative platform for supplying high-quality TNFα products with excellent activities for further pharmaceutical and clinical trials.

Augmentation therapy with alpha 1-antitrypsin: present and future of production, formulation, and delivery

Alpha 1-antitrypsin is one of the first protein therapeutics introduced on the market - more than 30 years ago - and, to date, it is indicated only for the treatment of the severe forms of a genetic condition known as alpha-1 antitrypsin deficiency. The only approved preparations are derived from plasma, posing potential problems associated with its limited supply and high processing costs. Moreover, augmentation therapy with alpha 1-antitrypsin is still limited to intravenous infusions, a cumbersome regimen for patients. Here, we review the recent literature on its possible future developments, focusing on i) the recombinant alternatives to the plasma-derived protein, ii) novel formulations, and iii) novel administration routes. Regulatory issues and the still unclear noncanonical functions of alpha 1-antitrypsin - possibly associated with the glycosylation pattern found only in the plasma-derived protein - have hindered the introduction of new products. However, potentially new therapeutic indications other than the treatment of alpha-1 antitrypsin deficiency might open the way to new sources and new formulations.

Implications of a Change of Paradigm in Alpha1 Antitrypsin Deficiency Augmentation Therapy: From Biochemical to Clinical Efficacy

Ever since the first studies, restoring proteinase imbalance in the lung has traditionally been considered as the main goal of alpha1 antitrypsin (AAT) replacement therapy. This strategy was therefore based on ensuring biochemical efficacy, identifying a protection threshold, and evaluating different dosage regimens. Subsequently, the publication of the results of the main clinical trials showing a decrease in the progression of pulmonary emphysema has led to a debate over a possible change in the main objective of treatment, from biochemical efficacy to clinical efficacy in terms of lung densitometry deterioration prevention. This new paradigm has produced a series controversies and unanswered questions which face clinicians managing AAT deficiency. In this review, the concepts that led to the approval of AAT replacement therapy are reviewed and discussed under a new prism of achieving clinical efficacy, with the reduction of lung deterioration as the main objective. Here, we propose the use of current knowledge and clinical experience to face existing challenges in different clinical scenarios, in order to help clinicians in decision-making, increase interest in the disease, and stimulate research in this field.

Expression and Purification of Vaccinia Virus DNA Topoisomerase IB Produced in the Silkworm-Baculovirus Expression System

Type IB DNA topoisomerases are enzymes to change the topological state of DNA molecules and are essential in studying replication, transcription, and recombination of nucleic acids in vitro. DNA topoisomerase IB from Vaccinia virus (vTopIB) is a 32 kDa, type I eukaryotic topoisomerase, which relaxed positively and negatively supercoiled DNAs without Mg²⁺ and ATP. Although vTopIB has been effectively produced in E. coli expression system, no studies remain available to explore an alternative platform to express recombinant vTopIB (rvTopIB) in a higher eukaryote, where the one can expect post-translational modifications that affect the activity of rvTopIB. Here in this study, rvTopIB with N-terminal tags was constructed and expressed in a silkworm-baculovirus expression vector system (silkworm-BEVS). We developed a simple two consecutive chromatography purification to obtain highly pure rvTopIB. The final yield of rvTopIB obtained from a baculovirus-infected silkworm larva was 83.25 μg. We also evaluated the activity and function of rvTopIB by the DNA relaxation activity assays using a negatively supercoiled pUC19 plasmid DNA as a substrate. With carefully assessing optimized conditions for the reaction buffer, we found that divalent ions, Mg²⁺, Mn²⁺, Ca²⁺, as well as ATP stimulate the DNA relaxation activity by rvTopIB. The functional and active form of rvTopIB, together with the yields of the protein we obtained, suggests that silkworm-BEVS would be a potential alternative platform to produce eukaryotic topoisomerases on an industrial scale.

Experimental and investigational drugs for the treatment of alpha-1 antitrypsin deficiency

Introduction: Alpha-1 antitrypsin deficiency (AATD) is most often associated with chronic lung disease, early onset emphysema, and liver disease. The standard of care in lung disease due to AATD is alpha-1 antitrypsin augmentation but there are several new and emerging treatment options under investigation for both lung and liver manifestations. Areas covered: We review therapeutic approaches to lung and liver disease in alpha-1 antitrypsin deficiency (AATD) and the agents in clinical development according to their mode of action. The focus is on products in clinical trials, but data from pre-clinical studies are described where relevant, particularly where progression to trials appears likely. Expert opinion: Clinical trials directed at lung and liver disease separately are now taking place. Multimodality treatment may be the future, but this could be limited by treatment costs. The next 5-10 years may reveal new guidance on when to use therapeutics for slowing disease progression with personalized treatment regimes coming to the forefront.

Chichen type III interferon produced by silkworm bioreactor induces ISG expression and restricts ALV-J infection in vitro

Type III interferon (IFN-λ) has recently been shown to exert a significant antiviral impact against viruses in vertebrates. Avian leukosis virus subgroup J (ALV-J), which causes tumor disease and immunosuppression in infected chicken, is a retrovirus that is difficult to prevent and control because of a lack of vaccines and drugs. Here, we obtained chicken IFN-λ (chIFN-λ) using a silkworm bioreactor and demonstrated that chIFN-λ has antiviral activity against ALV-J infection of both chicken embryo fibroblast cell line (DF1) and epithelial cell line (LMH). We found that chIFN-λ triggered higher levels of particular type III interferon-stimulated genes (type III ISGs) including myxovirus resistance protein (Mx), viperin (RSAD2), and interferon-inducible transmembrane protein 3 (IFITM3) in DF1 and LMH cells. Furthermore, over-expression of Mx, viperin, and IFITM3 could inhibit ALV-J infection in DF1 and LMH cells. Therefore, these results suggested that the anti-ALV-J function of chIFN-λ was specifically implemented by induction of expression of type III ISGs. Our data identified chIFN-λ as a critical antiviral agent of ALV-J infection and provides a potentially and attractive platform for the production of commercial chIFN-λ.

Expression and purification of biologically active human granulocyte-macrophage colony stimulating factor (hGM-CSF) using silkworm-baculovirus expression vector system

Human granulocyte-macrophage colony stimulating factor (hGM-CSF) is a hematopoietic growth factor. It is widely employed as a therapeutic agent targeting neutropenia in cancer patients undergoing chemotherapy and in patients with AIDS or after bone marrow transplantation. In this study, we constructed the recombinant baculoviruses for the expression of recombinant hGM-CSF (rhGM-CSF) with two small affinity tags (His-tag and Strep-tag) at the N or C-terminus. Compared to N-tagged rhGM-CSF, C-tagged rhGM-CSF was highly recovered from silkworm hemolymph. The purified rhGM-CSF proteins migrated as a diffuse band and were confirmed to hold N-glycosylations. A comparable activity was achieved when commercial hGM-CSF was tested as a control. Considering the high price of hGM-CSF in the market, our results and strategies using silkworm-baculovirus system can become a great reference for mass production of the active rhGM-CSF at a lower cost.