High Throughput Transfection of HEK293 Cells for Transient Protein Production

Research progress and immunological insights of shrimp allergens

Allergic diseases have become a major health issue in the 21st century. The FAO has pinpointed the eight most prevalent allergens worldwide, with shrimp allergy attracting global concern due to its escalating incidence. This review delves into the current knowledge of shrimp allergen types and traits, immune response mechanisms, advancements in cross-reactivity research, and breakthroughs in diagnostic and therapeutic methods. It highlights the variety of shrimp allergens, such as tropomyosin and arginine kinase, and concentrates on IgE-mediated immediate hypersensitivity reactions, involving mast cells and basophils, alongside the role of T cells and cytokines in non-IgE-mediated delayed hypersensitivity reactions. The exploration of cross-reactivity underscores the connection between shrimp allergy and allergies to other animals. Utilizing bioinformatics tools, including homology analysis, epitope prediction, and molecular modeling, has enhanced our comprehension of allergen molecular features. In treatment and diagnosis, innovative approaches like immunotherapy and gene editing technology hold potential to decrease allergic sensitivity, while emerging reduction techniques like heat treatment and enzymatic hydrolysis offer new strategies for the prevention and management of food allergies. The evolution of allergen detection and purification technologies has spurred innovation in testing methodologies, encompassing traditional in vivo tests like SPT and DBPCFC, in addition to a range of other techniques such as immunoassays, biochip technology, PCR, and histamine release experiments, propelling the instantaneous and accurate identification of allergens. These scientific breakthroughs not only expand our understanding of shrimp allergen biology but also lay the foundation for developing more effective allergy prevention and control strategies.

Apo- and holo-transferrin differentially interact with hephaestin and ferroportin in a novel mechanism of cellular iron release regulation

BACKGROUND

Apo- (iron free) and holo- (iron bound) transferrin (Tf) participate in precise regulation of brain iron uptake at endothelial cells of the blood-brain barrier. Apo-Tf indicates an iron-deficient environment and stimulates iron release, while holo-Tf indicates an iron sufficient environment and suppresses additional iron release. Free iron is exported through ferroportin, with hephaestin as an aid to the process. Until now, the molecular mechanisms of apo- and holo-Tf influence on iron release was largely unknown.

METHODS

Here we use a variety of cell culture techniques, including co-immunoprecipitation and proximity ligation assay, in iPSC-derived endothelial cells and HEK 293 cells to investigate the mechanism by which apo- and holo-Tf influence cellular iron release. Given the established role of hepcidin in regulating cellular iron release, we further explored the relationship of hepcidin to transferrin in this model.

RESULTS

We demonstrate that holo-Tf induces the internalization of ferroportin through the established ferroportin degradation pathway. Furthermore, holo-Tf directly interacts with ferroportin, whereas apo-Tf directly interacts with hephaestin. Only pathophysiological levels of hepcidin disrupt the interaction between holo-Tf and ferroportin, but similar hepcidin levels are unable to interfere with the interaction between apo-Tf and hephaestin. The disruption of the holo-Tf and ferroportin interaction by hepcidin is due to hepcidin's ability to more rapidly internalize ferroportin compared to holo-Tf.

CONCLUSIONS

These novel findings provide a molecular mechanism for apo- and holo-Tf regulation of iron release from endothelial cells. They further demonstrate how hepcidin impacts these protein-protein interactions, and offer a model for how holo-Tf and hepcidin cooperate to suppress iron release. These results expand on our previous reports on mechanisms mediating regulation of brain iron uptake to provide a more thorough understanding of the regulatory mechanisms mediating cellular iron release in general.

Molecular cloning, expression analysis and functional characterization of chicken cytochrome P450 27A1: A novel mitochondrial vitamin D3 25-hydroxylase

Vitamin D₃ is hydroxylated by cytochrome P450 (CYP) before exerting biological effects. The chicken CYP involved in vitamin D₃ 25-hydroxylation has yet to be cloned, and little is known about its functional characteristics, tissue distribution, and cellular expression. We identified a novel, full-length CYP27A1 gene cloned from chicken hepatocyte cDNA that encodes a putative protein of 518 amino acids. Swiss modeling revealed that chicken CYP27A1 has a classic open-fold form. Multisequence homology alignment determined that CYP27A1 contains conserved motifs for substrate recognition and binding. Quantitative real-time PCR analysis in 2-mo-old Partridge Shank broilers demonstrated that CYP27A1 mRNA levels were highest in the liver, followed by the thigh muscles, the breast muscles, and kidneys. The transcripts of CYP27A1 in breast muscles were significantly higher in males than in females. A subcellular localization analysis demonstrated that CYP27A1 was mainly expressed in the mitochondria. In vitro enzyme assays suggested that recombinant CYP27A1 hydroxylates vitamin D₃ at the C-25 position to form 25-hydroxyvitamin D₃ (25(OH)D₃). The K_m and V_max values for CYP27A1-dependent vitamin D₃ 25-hydroxylation were estimated to be 4.929 μM and 0.389 mol min^-1 mg^-1 protein, respectively. In summary, these results suggest that CYP27A1 encodes a mitochondrial CYP that plays an important physiologic role in the 25-hydroxylation of vitamin D₃ in chickens, providing novel insights into vitamin D₃ metabolism in this species.

Evaluation of the Mucosal Immunity Effect of Bovine Viral Diarrhea Virus Subunit Vaccine E2Fc and E2Ft

Classified as a class B infectious disease by the World Organization for Animal Health (OIE), bovine viral diarrhea/mucosal disease is an acute, highly contagious disease caused by the bovine viral diarrhea virus (BVDV). Sporadic endemics of BVDV often lead to huge economic losses to the dairy and beef industries. To shed light on the prevention and control of BVDV, we developed two novel subunit vaccines by expressing bovine viral diarrhea virus E2 fusion recombinant proteins (E2Fc and E2Ft) through suspended HEK293 cells. We also evaluated the immune effects of the vaccines. The results showed that both subunit vaccines induced an intense mucosal immune response in calves. Mechanistically, E2Fc bonded to the Fc γ receptor (FcγRI) on antigen-presenting cells (APCs) and promoted IgA secretion, leading to a stronger T-cell immune response (Th1 type). The neutralizing antibody titer stimulated by the mucosal-immunized E2Fc subunit vaccine reached 1:64, which was higher than that of the E2Ft subunit vaccine and that of the intramuscular inactivated vaccine. The two novel subunit vaccines for mucosal immunity developed in this study, E2Fc and E2Ft, can be further used as new strategies to control BVDV by enhancing cellular and humoral immunity.

Far upstream element -binding protein 1 (FUBP1) participates in the malignant process and glycolysis of colon cancer cells by combining with c-Myc

Human distal upstream element (Fuse) binding protein 1 (FUBP1) is a transcriptional regulator of c-Myc and represents an important prognostic marker in many cancers. Therefore, the present study aimed to investigate whether FUBP1 could combine with c-Myc to participate in the progression of colon cancer. Detection of FUBP1 expression was done through reverse transcription-quantitative PCR (RT-qPCR), and the combination of FUBP1 and c-Myc was detected by immunoprecipitation assay. Cell counting kit (CCK)-8, colony formation, transwell and wound healing were applied for assessing the ability of cells to proliferate, migrate, and invade; glycolysis and lactic acid detection kits were used to detect glucose uptake and lactic acid content, while western blotting was adopted to detect the protein expression of glycolysis-related genes. FUBP1 expression was elevated in HCT116 cells relative to other colon cancer cell lines, and silencing FUBP1 could inhibit the ability of HCT116 cells to proliferate, migrate, invade and glycolysis, and enhance its apoptosis. In addition, the results of immunoprecipitation experiments showed that FUBP1 could bind to c-Myc. c-Myc overexpression reversed the inhibitory effects of FUBP1 knockdown on the ability of HCT116 cells to proliferate, migrate, invade and glycolysis. The results indicated that FUBP1 could participate in the deterioration process of colon cancer cells by combining with c-Myc, and it has clinical significance for understanding the key role of FUBP1 in tumor genesis.

Impact of lipopolysaccharides on cultivation and recombinant protein expression in human embryonal kidney (HEK-293) cells

The human embryonal kidney 293 cell (HEK-293) is a widely used expression host for transient gene expression. The genes or plasmids used for the transient transfections are usually propagated and extracted from the gram-negative bacterium Escherichia coli, the workhorse for molecular biologists. As a gram-negative bacterium E. coli has an outer membrane (OM) containing lipopolysaccharides (LPS) or endotoxins. LPS are very potent inducers of inflammatory cytokines in the body. In early research phases DNA intended for transient transfections is not routinely checked for LPS-levels. In this study we addressed the question whether LPS has an impact on the cultivation and production of a recombinant antibody. At high concentrations the presence of LPS has a detrimental impact on cell viability and recombinant protein expression. But low LPS concentrations are tolerated and might even enhance protein expression levels.

Optimized Recombinant Production of Secreted Proteins Using Human Embryonic Kidney (HEK293) Cells Grown in Suspension

Recombinant proteins are an essential milestone for a plethora of different applications ranging from pharmaceutical to clinical, and mammalian cell lines are among the currently preferred systems to obtain large amounts of proteins of interest due to their high level of post-translational modification and manageable large-scale production. In this regard, human embryonic kidney 293 (HEK293) cells constitute one of the main standard lab-scale mammalian hosts for recombinant protein production since these cells are relatively easy to handle, scale-up, and transfect. Here, we present a detailed protocol for the cost-effective, reproducible, and scalable implementation of HEK293 cell cultures in suspension (suitable for commercially available HEK293 cells, HEK293-F) for high-quantity recombinant production of secreted soluble multi-domain proteins. In addition, the protocol is optimized for a Monday-to-Friday maintenance schedule, thus simplifying and streamlining the work of operators responsible for cell culture maintenance. Graphic abstract: Schematic overview of the workflow described in this protocol.

Optimization of a transient antibody expression platform towards high titer and efficiency

Transient gene expression (TGE) using mammalian cells is an extensively used technology for the production of antibodies and recombinant proteins and has been widely adopted by both academic and industrial labs. Chinese Hamster Ovary (CHO) cells have become one of the major workhorses for TGE of recombinant antibodies due to their attractive features: post-translational modifications, adaptation to high cell densities, and use of serum-free media. In this study, we describe the optimization of parameters for TGE for antibodies from CHO cells. Through a matrix evaluation of multiple factors including inoculum, transfection conditions, amount and type of DNA used, and post-transfection culture conditions, we arrived at an uniquely optimized process with higher titer and reduced costs and time, thus increasing the overall efficiency of early antibody material supply. We further investigated the amount of coding DNA used in TGE and the influence of kinetics and size of the transfection complex on the in vitro efficiency of the transfection. We present here the first report of an optimized TGE platform using Filler DNA in an early drug discovery setting for the screening and production of therapeutic mAbs.

Development of a high cell density transient CHO platform yielding mAb titers greater than 2 g/L in only 7 days

We developed a simple transient Chinese Hamster Ovary expression platform. Titers for a random panel of 20 clinical monoclonal antibodies (mAbs) ranged from 0.6 to 2.7 g/L after 7 days. Two factors were the key in obtaining these high titers. First, we utilized an extremely high starting cell density (20 million cells/ml), and then arrested further cell growth by employing mild hypothermic conditions (32°C). Second, we performed a 6-variable Design of Experiments to find optimal concentrations of plasmid DNA (coding DNA), boost DNA (DNA encoding the XBP1S transcription factor), transfection reagent (polyethylenimine [PEI]), and nutrient feed amounts. High coding DNA concentrations (12.5 mg/L) were found to be optimal. We therefore diluted expensive coding DNA with inexpensive inert filler DNA (herring sperm DNA). Reducing the coding DNA concentration by 70% from 12.5 to 3.75 mg/L did not meaningfully reduce mAb titers. Titers for the same panel of 20 clinical mAbs ranged from 0.7 to 2.2 g/L after reducing the coding DNA concentration to 3.75 mg/L. Finally, we found that titer and product quality attributes were similar for a clinical mAb (rituximab) expressed at very different scales (volumes ranging from 3 ml to 2 L).