Comparative Immunogenicity of the Recombinant Receptor-Binding Domain of Protein S SARS-CoV-2 Obtained in Prokaryotic and Mammalian Expression Systems

The receptor-binding domain (RBD) of the protein S SARS-CoV-2 is considered to be one of the appealing targets for developing a vaccine against COVID-19. The choice of an expression system is essential when developing subunit vaccines, as it ensures the effective synthesis of the correctly folded target protein, and maintains its antigenic and immunogenic properties. Here, we describe the production of a recombinant RBD protein using prokaryotic (pRBD) and mammalian (mRBD) expression systems, and compare the immunogenicity of prokaryotic and mammalian-expressed RBD using a BALB/c mice model. An analysis of the sera from mice immunized with both variants of the protein revealed that the mRBD expressed in CHO cells provides a significantly stronger humoral immune response compared with the RBD expressed in E.coli cells. A specific antibody titer of sera from mice immunized with mRBD was ten-fold higher than the sera from the mice that received pRBD in ELISA, and about 100-fold higher in a neutralization test. The data obtained suggests that mRBD is capable of inducing neutralizing antibodies against SARS-CoV-2.

Virus-Like Particles: Revolutionary Platforms for Developing Vaccines Against Emerging Infectious Diseases

Virus-like particles (VLPs) are nanostructures that possess diverse applications in therapeutics, immunization, and diagnostics. With the recent advancements in biomedical engineering technologies, commercially available VLP-based vaccines are being extensively used to combat infectious diseases, whereas many more are in different stages of development in clinical studies. Because of their desired characteristics in terms of efficacy, safety, and diversity, VLP-based approaches might become more recurrent in the years to come. However, some production and fabrication challenges must be addressed before VLP-based approaches can be widely used in therapeutics. This review offers insight into the recent VLP-based vaccines development, with an emphasis on their characteristics, expression systems, and potential applicability as ideal candidates to combat emerging virulent pathogens. Finally, the potential of VLP-based vaccine as viable and efficient immunizing agents to induce immunity against virulent infectious agents, including, SARS-CoV-2 and protein nanoparticle-based vaccines has been elaborated. Thus, VLP vaccines may serve as an effective alternative to conventional vaccine strategies in combating emerging infectious diseases.

Expression, Microencapsulation of Recombinant Human Epidermal Growth Factor, and Release Study in Gastric Ulcer Representing Condition

Recombinant human epidermal growth factor (rhEGF) has been studied and expressed in various expression systems. It has been also commercialized and clinically used, yet limited to topical diseases. However, being naturally expressed in different tissues, the rhEGF is potential to be applied not only for external wound and skin disorders, but also to regenerates internal damaged epidermal cells such found in gastric ulcer. In the recent study, chitosan microparticles were developed to facilitate delivery of the rhEGF and to overcome gastric degradation that majorly interfere protein, particularly rhEGF oral administration. The rhEGF was expressed in E. coli BL21(DE3) and purified using Ni-NTA chromatography. The refolded rhEGF showed proliferation activity on MC7 cells. rhEGF loaded chitosan microparticles were stable in the gastric and specifically released the loaded rhEGF in the high oxidative environment in acidic pH representing gastric ulcer condition.

Genetic Engineering Technique in Virus-Like Particle Vaccine Construction

Vaccine becomes a very effective strategy to deal with various infectious diseases even to the point of eradication as in the smalpox virus. At present many conventional vaccines such as inactivated and live-attenuated vaccines. However, these vaccine methods have side effects on the population. Viral-like particle (VLP) is an alternative vaccine based on recombinant DNA technology that is safe with the same immunogenicity as conventional viruses. This vaccine has been shown to induce humoral immune responses mediated by antibodies and cellular immune responses mediated by cytotoxic T cells. With these advantages, currently various types of vaccines have only been developed on a VLP basis. VLP can be produced from a variety of recombinant gene expression systems including bacterial cell expression systems, yeast cells, insect cells, mammalian cells, plant cells, and cell-free systems.

Recent Developments of Recombinant Protein Expression for Therapeutic Purposes

In the most recent seven to eight years, the therapeutic recombinant proteins have rapidly expanded in the biotechnology domain due to its wide variety of needs. There has been significant development in the mammalian expression system for fine purification and increased level of expressed recombinant proteins [1,2]. Many drugs like tetracycline have been demonstrated on the Chinese Hamster Ovary cell line for promising multi control strategies and effective cytotoxicity. Mammalian expression system improves the proper glycosylation of recombinant proteins which are very helpful to increase solubility of product [3-6]. Meanwhile on the prokaryotic expression system, E. coli has proven to be an easier to handle, friendly and economical strain [2]. Recently these expression systems are using to work on antibody fragment productions and their proper folding with co-expression of chaperones [7]. Moreover E. coli has been used for the production of cancer cell penetrating peptides which promises the targeted delivery of drugs to specific effector cells only. Yeast systems are also being used for the antibody fragments production and the high level production of insulin. Interestingly cell free expression systems are also participating in this game and that would be very fascinating to see in the coming years about cell extract medium for production of high level recombinant protein [8, 9]. Purification and optimization of recombinant protein has always been a challenging situation for scientists and they paid more attention to increase the overall yield of the product. Many affinity chromatography techniques has been introduced for efficient purification of protein of interest [10]. Despite these research and developments in methodologies to produce and purify the recombinant therapeutic protein, scientists still face the hurdles and challenges with all expression systems. Rationally E. coli produces inclusion bodies and many mammalian cell types do not show the same results with the same recombinant protein. [11]. So there is a requirement for adding the appropriate features to the expression systems focused to better improvising recovery, production and purification of recombinant protein. Copyright(c) The Author

Biotechnology Applications of Cell-Free Expression Systems

Cell-free systems are a rapidly expanding platform technology with an important role in the engineering of biological systems. The key advantages that drive their broad adoption are increased efficiency, versatility, and low cost compared to in vivo systems. Traditionally, in vivo platforms have been used to synthesize novel and industrially relevant proteins and serve as a testbed for prototyping numerous biotechnologies such as genetic circuits and biosensors. Although in vivo platforms currently have many applications within biotechnology, they are hindered by time-constraining growth cycles, homeostatic considerations, and limited adaptability in production. Conversely, cell-free platforms are not hindered by constraints for supporting life and are therefore highly adaptable to a broad range of production and testing schemes. The advantages of cell-free platforms are being leveraged more commonly by the biotechnology community, and cell-free applications are expected to grow exponentially in the next decade. In this study, new and emerging applications of cell-free platforms, with a specific focus on cell-free protein synthesis (CFPS), will be examined. The current and near-future role of CFPS within metabolic engineering, prototyping, and biomanufacturing will be investigated as well as how the integration of machine learning is beneficial to these applications.

Thermal Analysis of Protein Stability and Ligand Binding in Complex Media

ABSTRACTScreening of ligands that can bind to biologic products of in vitro expression systems typically requires some purification of the expressed biologic target. Such purification is often laborious and time consuming and a limiting challenge. What is required, that could represent an enormous advantage, is the ability to screen expressed proteins in the crude lysate stage without purification. For that purpose, we explore here the utility of differential scanning calorimetry (DSC) measurements for detecting the presence of specific proteins and their interactions with ligands in the complex media where they were prepared, i.e. crude lysates. Model systems were designed to mimic analogous conditions comparable to those that might be encountered in actual in vitro expression systems. Results are reported for several examples where DSC measurements distinctly showed differences in the thermal denaturation behaviors of the crude lysate alone, proteins and proteins plus binding ligands added to the crude lysate. Results were obtained for Streptavidin/Biotin binding in E. coli lysate, and binding of Angiotensin Converting Enzyme 2 (ACE2) by captopril or lisinopril in the lysate supernatant derived from cultured Human Kidney cells (HEK293). ACE2 binding by the reactive binding domain (RBC) of SARS-CoV-2 was also examined. Binding of ACE2 by RBC and lisinopril were similar and consistent with the reported ACE2 inhibitory activity of lisinopril.

High Efficiency Recombinant Protein Purification Using mCherry and YFP Nanobody Affinity Matrices

Mammalian cell lines are important expression systems for large proteins and protein complexes, particularly when the acquisition of post-translational modifications in the proteins native environment is desired. However, low or variable transfection efficiencies are challenges that must be overcome to use such an expression system. Expression of recombinant proteins as a fluorescent protein fusion enables real-time monitoring of protein expression, and also provides an affinity handle for one-step protein purification using a suitable affinity reagent. Here we describe a panel of anti-GFP and anti-mCherry nanobody affinity matrices and their efficacy for purification of GFP/YFP or mCherry fusion proteins. We define the molecular basis by which they bind their target protein using X-ray crystallography. From these analyses we define an optimal pair of nanobodies for purification of recombinant protein tagged with GFP/YFP or mCherry, and demonstrate these nanobody-sepharose supports are stable to many rounds of cleaning and extended incubation in denaturing conditions. Finally, we demonstrate the utility of the mCherry-tag system by using it to purify recombinant human Topoisomerase 2α expressed in HEK293F cells. The mCherry-tag and GFP/YFP-tag expression systems can be utilized for recombinant protein expression individually or in tandem for mammalian protein expression systems where real-time monitoring of protein expression levels and a high-efficiency purification step is needed.

Revisiting the Role of Ser982 Phosphorylation in Stoichiometry Shift of the Electrogenic Na+/qHCO3− Cotransporter NBCe1

In most cell types and heterologous expression systems, the electrogenic sodium-bicarbonate cotransporter NBCe1 operates with a 1Na+–2HCO3− stoichiometry that, given typical transmembrane electrochemical gradients, promotes Na+ and HCO3− influx. However, NBCe1 in the kidney mediates HCO3− efflux (HCO3− reabsorption), a direction that has been predicted to be favored only if NBCe1 operates with a 1:3 stoichiometry. The phosphorylation state of Ser982 in the cytosolic carboxy-terminal domain of NBCe1 has been reported to be a key determinant of the transporter stoichiometry, with non-phosphorylated Ser982 favoring a 1:3 stoichiometry. Conversely, phosphoproteomic data from renal cortical preparations have revealed the presence of NBCe1 peptides including phosphoserine982 (pSer982) and/or pSer985 although it was not known what proportion of NBCe1 molecules were phosphorylated. In the present study, we report the generation, characterization, and application of a novel phosphospecific antibody raised against NBCe1/pSer982 and show that, contrary to expectations, Ser982 is more prevalently phosphorylated in murine kidneys (in which NBCe1 mediates HCO3− efflux) than in murine colons (in which NBCe1 mediates HCO3− influx). Using phosphomimetic mutants of murine NBCe1 expressed in Xenopus oocytes, we found no evidence that the phosphorylation state of Ser982 or Ser985 alone influences the transport stoichiometry or conductance. Furthermore, we found that the phosphorylation of NBCe1/Ser982 is enhanced in murine kidneys following a 24 h induction of metabolic acidosis. We conclude that the phosphorylation status of Ser982 is not a key determinant of NBCe1 stoichiometry but correlates with presumed NBCe1 activity.

Vaccine Production

Introduction Vaccines are biological products that elicit a protective immune response. The details of the manufacturing processes are varied depending on the particular characteristics of the vaccine. There are classically, three basic types of vaccines against viral and bacterial pathogens (For mRNA-, DNA- and vector-vaccines see Chapters 7, 8, 9): Live-attenuated. Killed (non-live). Subunit. “Classical” Vaccine Production The basic classical process includes 5 phases: expression, harvest, inactivation, purification, formulation. The expression systems for viral and bacterial vaccines are distinct. Bacterial expression is performed in fermenters. Viral vaccines are produced in animal cell culture or embryonated chicken eggs. Processes for whole viral or bacterial vaccines often involve only limited processing after expression. Subunit vaccines routinely require the most purification to separate the product from other contaminants. Challenges Challenges for bacterial vaccines include testing to ensure the safety and efficacy of the product. Inactivation procedures need to be carefully controlled. Live attenuated vaccines need to be tested to ensure the vaccine strains are still safe and effective. Viral vaccines require testing to ensure foreign infectious agents are not introduced during processing. Both cultured cells and egg present risks for infection. Live viral vaccines and gene vectors need to be carefully engineered and tested to minimize safety concerns. Highly variable vaccine targets such as influenza need to be re-adapted to current circulating strains.