Production of an antibody Fab fragment using 2A peptide in insect cells.

Antibody Fab fragments consist of heavy chain (Hc) and light chain (Lc) polypeptides assembled with a disulphide bond. The production of a recombinant Fab fragment requires the simultaneous expression of two genes encoding both an Hc and an Lc in the same host cell. In the present study, we investigated the production of Fab fragments in lepidopteran insect cells using a bicistronic plasmid vector carrying the Hc and Lc genes linked with a 2A self-cleaving peptide sequence from the porcine teschovirus-1. We also examined the arrangement of a GSG spacer sequence and a furin cleavage site sequence with the 2A sequence. Western blot analysis and enzyme-linked immunosorbent assay (ELISA) of culture supernatants showed that Trichoplusia ni BTI-TN-5B1-4 (High Five) cells transfected with a plasmid in which the Hc and Lc genes were joined by the 2A sequence successfully secreted Fab fragments with antigen-binding activity after self-cleavage of the 2A peptide. The GSG linker enhanced 2A cleavage efficiency, and the furin recognition site was useful for removal of 2A residues from the Hc. Transfection with a single plasmid that contained sequences for GSG, the furin cleavage site, GSG, and the 2A peptide between the Hc and Lc genes exhibited a higher productivity than co-transfection with a set of plasmids separately carrying the Hc or Lc gene. These results demonstrate that bicistronic expression with the appropriate combination of a furin recognition site, GSG linkers, and a 2A peptide may be an effective way to efficiently produce recombinant antibody molecules in insect cells.

Production of Japanese encephalitis virus-like particles using the baculovirus-insect cell system.

The production of a secreted form of Japanese encephalitis (JE) virus-like particles (VLPs) using the baculovirus-insect cell system was investigated. A recombinant baculovirus that contained the JE virus (JEV) prM signal sequence and the genes encoding the precursor (prM) of the viral membrane protein (M) and the envelope glycoprotein (E) was constructed. Western blotting and enzyme-linked immunosorbent assay (ELISA) of the culture supernatant showed that Spodoptera frugiperda Sf9 cells infected with the recombinant baculovirus had secreted the E protein. Sucrose density-gradient sedimentation analysis of the culture supernatant suggested that secreted E antigen molecules were in a particulate form. Baculovirus-infected Sf9 cells produced more than a 10-fold higher yield of E antigen than that produced by previously reported recombinant CHO cells. Following infection with a recombinant baculovirus encoding a form of prM with a pr/M cleavage site mutation designed to suppress cell-fusion activity of E, Sf9 cells showed an E antigen yield comparable to a yield obtained with the baculovirus encoding the authentic form of prM. Baculovirus-infected Trichoplusia ni BTI-TN-5B1-4 (High Five) cells secreted less of the E antigen than Sf9 cells. Moreover, the Drosophila BiP signal sequence gave an E antigen yield comparable to the prM signal sequence, while the honeybee melittin signal sequence and the baculovirus gp64 signal sequence resulted in lower yields of the E antigen. These results provide information important to the development of VLP production processes using the baculovirus-insect cell system.

Immobilization of 293 cells using porous support particles for adenovirus vector production.

Adenovirus vector production by anchorage-independent 293 cells immobilized using porous biomass support particles (BSPs) was investigated in static and shake-flask cultures for efficient large-scale production of adenovirus vectors for gene therapy applications. The density of cells immobilized within BSPs was evaluated by measuring their WST-8 (2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt) reduction activity. In shake-flask culture, 293-F cells, which were adapted to serum-free suspension culture, were not successfully retained within reticulated polyvinyl formal (PVF) resin BSPs (2 × 2 × 2 mm cubes) with matrices of relatively small pores (pore diameter 60 µm). When the BSPs were coated with a cationic polymer polyethyleneimine, a high cell density of more than 10(7) cells cm(-3)-BSP was achieved in both static and shake-flask cultures with regular replacement of the culture medium. After infection with an adenovirus vector carrying the enhanced green fluorescent protein gene (Ad EGFP), the specific Ad EGFP productivity of the immobilized cells was comparable to the maximal productivity of non-immobilized 293-F cells by maintaining favorable conditions in the culture environment.

Adenovirus vector production using low-multiplicity infection of 293 cells.

The use of low-multiplicity infection of 293 cells in static culture with regular medium replacement was investigated for efficient large-scale production of adenovirus vectors for gene therapy applications. An adenovirus vector carrying the enhanced green fluorescent protein gene (Ad EGFP) was used to infect 293-F cells at a low multiplicity of infection (MOI) of 0.00001-0.1 transductional unit (TU) cell(-1). The cells, which have the ability to grow in suspension, were incubated in T-flasks and the serum-free culture medium was replaced with fresh medium via centrifugation every 2 days. Because only a small proportion of cells were initially infected at low MOIs (<1 TU cell(-1)), uninfected cells continued to grow until they were infected by progeny adenoviruses released from previously infected cells. When 293-F cells at a relatively low density of 1 x 10(5) cells cm(-3) were infected with Ad EGFP at a low MOI of 0.001 TU cell(-1), the vector yield was 2.7-fold higher than the maximum yield obtained with high-multiplicity infection (MOI = 10 TU cell(-1)) in batch culture. These results indicate that efficient adenovirus vector production using low MOIs is achieved by minimization of either nutrient depletion and/or accumulation of inhibitory metabolites in the culture medium.

Tandem multimer expression of angiotensin I-converting enzyme inhibitory peptide in Escherichia coli.

It is common for small tandem peptide multimer genes to be indirectly inserted into expression vectors and fused with a protein tag. In this study, a multimer of the tandem angiotensin I-converting enzyme inhibitory peptide (ACE-IP) gene was directly transferred to a commercially available vector and the designed gene was expressed as a repeated peptide in Escherichia coli BL21(DE3)pLysS. The process further developed in our study was the construction of six-repeated ACE-IP synthetic genes and their direct insertion. Protein expression in inclusion bodies was confirmed by SDS-PAGE and Western blot. Acid hydrolysis of inclusion bodies produced single-unit peptides through cleavage of the aspartyl-prolyl bonds. This cleaved recombinant peptide (rACE-IP) was purified using immuno-affinity chromatography followed by reversed phase-HPLC. 105-115 mg of the lyophilized recombinant peptide was obtained from 1 L E. coli culture. In vitro biological activity of rACE-IP was indistinguishable from that of the natural peptide produced by hydrolysis in artificial gastric juice or by acidic hydrolysis. The rACE-IP prepared by recombinant DNA technology and solid-phase synthesis methods showed a similar IC(50). This strategy could be used for the expression of important peptides, which have N-terminal proline (P) and C-terminal aspartic acid residues (D) for commercial applications, e.g. functional foods and drinks.

Angiotensin-I converting enzyme (ACE) inhibitory mechanism of tripeptides containing aromatic residues.

Angiotensin-I converting enzyme (ACE) plays important roles in the regulation of blood pressure, and ACE inhibitory peptides in food materials have attracted attention for their antihypertensive function. In this study, the function of amino acids in ACE inhibitory tripeptides was clarified.

New detection method for hydrogen gas for screening hydrogen-producing microorganisms using water-soluble wilkinson's catalyst derivative.

A water-soluble color indicator was developed for the effective screening of hydrogen-producing microorganisms. This indicator consists of a coloring agent and a water-soluble derivative of Wilkinson's catalyst. Wilkinson's catalyst, Tris(triphenylphosphine) rhodium chloride, had been developed as a catalyst for the hydrogenation of olefins. We used a sulfonate of the catalyst for the hydrogenation of coloring agent in an aqueous medium. Several coloring agents, such as methyl orange, methyl red sodium, neutral red and Evan's blue, dissolved in water together with the sulfonated catalyst showed a change in color when hydrogen gas was fed into the solution by sparging at room temperature. We confirmed that methyl orange was decolorized by biologically produced hydrogen, when the photosynthetic bacterial strain Rhodobacter capsulatus ST-410 was grown in a medium containing 0.6 mM catalyst and 0.075 mM methyl orange in test tubes of 5 ml working volume.