High Level Expression of Active Human Prothrombin in a Vaccina Virus Expression System

Optimization of protein expression systems for modern drug discovery

The expression of high levels of stable and functional proteins remains a bottleneck in many scientific endeavors, including the determination of structures in a high-throughput fashion or the screening for novel active compounds in modern drug discovery. Recently, numerous developments have been made to improve the production of soluble and active proteins in heterologous expression systems. These include modifications to the expression constructs, the introduction of new and/or improved pro- and eukaryotic expression systems, and the development of improved cell-free protein synthesis systems. The introduction of robotics has enabled a massive parallelization of expression experiments, thereby vastly increasing the throughput and, hopefully, the output of such experiments. In addition, the big challenges of recombinant overexpression of membrane and secreted proteins are tackled, and some new methods are reviewed.

Recombinant protein production by large-scale transient gene expression in mammalian cells: state of the art and future perspectives

The expansion of the biologics pipeline depends on the identification of candidate proteins for clinical trials. Speed is one of the critical issues, and the rapid production of high quality, research-grade material for preclinical studies by transient gene expression (TGE) is addressing this factor in an impressive way: following DNA transfection, the production phase for TGE is usually 2-10 days. Recombinant proteins (r-proteins) produced by TGE can therefore enter the drug development and screening process in a very short time--weeks. With "classical" approaches to protein expression from mammalian cells, it takes months to establish a productive host cell line. This article summarizes efforts in industry and academia to use TGE to produce tens to hundreds of milligrams of r-proteins for either fundamental research or preclinical studies.

Large-scale transient expression in mammalian cells for recombinant protein production

Large-scale transient expression from mammalian cells is a new technology. Breakthroughs have been achieved for non-viral delivery methods: transfections can now be done at the 1-10 L scale with mammalian cells grown in suspension. Production of 1-20 mg/L of recombinant protein have been obtained in stirred bioreactors. Modified alphaviruses have provided a fast and efficient expression technology based on viral vectors.

Rational design, recombinant preparation, and in vitro and in vivo characterization of human prothrombin-derived hirudin antagonists

A mutant derivative of human prothrombin in which active site aspartate at position 419 is replaced by an asparagine (D419N-prothrombin) has been designed, expressed in recombinant Chinese hamster ovary cells, and purified to homogeneity. D419N-prothrombin was converted to the related molecules D419N-meizothrombin and D419N-thrombin by limited proteolysis by Echis carinatus and Oxyuranus scutellatus venom protease, respectively, and affinity-purified using an immobilized modified C-terminal hirudin-derived peptide. Neither D419N-thrombin nor D419N-meizothrombin exhibited thrombin activity. Titration resulted in no detection of the active site, but binding to the most specific thrombin inhibitor, hirudin, was conserved in both proteins. In vitro examinations showed that D419N-thrombin and D419N-meizothrombin bind to immobilized hirudin, neutralize hirudin in human blood plasma as well as in the purified system, and reactivate the thrombin-hirudin complex. Animal model studies confirmed that D419N-thrombin and D419N-meizothrombin act as hirudin antagonist in blood circulation without detectable effects on the coagulation system. Thus, both D419N-thrombin and D419N-meizothrombin combine for the first time hirudin-neutralizing properties with the advantages of recombinant production of human coagulation factors.

Effect of serum type and concentration on the expression ofβ-galactosidase in recombinant vaccinia virus infected HeLa S3 cells

The effect of serum type and concentration on recombinant protein expression in vaccinia virus infected HeLa S3 cells was studied in both static and suspension culture. A model heterologous protein,β-galactosidase (β-gal), was used. Calf and horse sera in the range of 0.5-10%(v/v) were investigated. In static culture, the calf serum concentration did not show any significant influence on the β-gal production which was almost completed within 24h postinfection (pi). Higher horse serum concentration, on the other hand, resulted in higher β-gal concentration which continued to increase until 48 h pi. Total β-gal concentrations in 0.5% calf serum at 24 h pi and 10% horse serum at 48 h pi were 2.2±0.7 and 2.2±0.1 IU/ml, respectively. In suspension culture, both sera showed their respective effects on the β-gal production similar to those observed in static culture, indicating that the cultivation method had little influence on β-gal production. Accordingly, the use of 0.5% calf serum after virus infection in recommended for economical β-gal production.

Purification of recombinant human coagulation factors II and IX and protein S expressed in recombinant Vaccinia virus-infected Vero cells

Recombinant human coagulation factors II and IX and recombinant human protein S were expressed by the Vaccinia virus expression system in Vero cells and isolated from the serum-free media. All three recombinant proteins were purified by the same universal strategy. After concentration by anion exchange chromatography, recombinant coagulation factors were purified by anion exchange filtration in the presence of Ca2+. The addition of Ca2+ to the vitamin K-dependent coagulation factors modified their physico-chemical behavior during anion exchange chromatography and resulted in the separation of the recombinant coagulation proteins from contaminating proteins.