Silkworm-baculovirus Expression System Research Articles

Efficient isolation of specific genomic regions retaining molecular interactions by the iChIP system using recombinant exogenous DNA-binding proteins

Comprehensive understanding of mechanisms of genome functions requires identification of molecules interacting with genomic regions of interest in vivo. We previously developed the insertional chromatin immunoprecipitation (iChIP) technology to isolate specific genomic regions retaining molecular interactions and identify their associated molecules. iChIP consists of locus-tagging and affinity purification. The recognition sequences of an exogenous DNA-binding protein such as LexA are inserted into a genomic region of interest in the cell to be analyzed. The exogenous DNA-binding protein fused with a tag(s) is expressed in the cell and the target genomic region is purified with antibody against the tag(s). In this study, we developed the iChIP system using recombinant DNA-binding proteins to make iChIP more straightforward than the conventional iChIP system using expression of the exogenous DNA-binding proteins in the cells to be analyzed. In this system, recombinant 3xFNLDD-D (r3xFNLDD-D) consisting of the 3xFLAG-tag, a nuclear localization signal (NLS), the DNA-binding domain plus the dimerization domain of the LexA protein, and the Dock-tag is used for isolation of specific genomic regions. r3xFNLDD-D was expressed using a silkworm-baculovirus expression system and purified by affinity purification. iChIP using r3xFNLDD-D could efficiently isolate the single-copy chicken Pax5 (cPax5) locus, in which LexA binding elements were inserted, with negligible contamination of other genomic regions. In addition, we could detect RNA associated with the cPax5 locus using this form of the iChIP system combined with RT-PCR. The iChIP system using r3xFNLDD-D can isolate specific genomic regions retaining molecular interactions without expression of the exogenous DNA-binding protein in the cell to be analyzed. iChIP using r3xFNLDD-D would be more straightforward and useful for analysis of specific genomic regions to elucidate their functions as compared to the previously published iChIP protocol.

Rabies virus nucleoprotein expressed in silkworm pupae at high-levels and evaluation of immune responses in mice

Rabies is one of the most fatal zoonotic diseases in developing countries, where a safe, cheap and effective vaccine against the disease remains unaffordable. In this paper, we describe a new silkworm-baculovirus expression system to express the nucleoprotein (N) gene of rabies virus and evaluation of the immune response in BALB/c mice. A recombinant baculovirus -rBmNPV(RV-N) carrying the N gene of rabies virus Evelyn Rokitniki Abelseth (ERA) strain was constructed and the N protein expression was evaluated in Bombyx mori (BmN) cells and silkworm pupae by immunofluorescence staining, Western blots and enzyme-linked immunosorbent assay (ELISA). The immune response to vaccines was evaluated based on serum IgG antibody titers and challenge experiments. The study revealed that N protein of rabies virus can be highly expressed in silkworm baculovirus expression system and the vaccine of N antigen presents a promising approach for the prevention of rabies virus.

Manufacturing Pharmaceutical-Grade Interferons Using Silkworm- Baculovirus System

To develop feline and canine interferons as medicine for companion animal, silkworm-baculovirus expression system was established as a manufacturing technology. Thus produced interferons were successfully cleared for a sale in commercial market. For expression of feline interferon in the silkworm, recombinant Bombyx mori nucleopolyhedrovirus (BmNPV) was constructed carrying feline interferon cDNA. When the recombinant BmNPV was injected to silkworm larvae, as much as 1.2 × 10 8 unit/mL of feline interferon was produced in their hemolymph. This productivity is 100–fold higher than those of E. coli, yeast and mammalian cell expression system. Similarly, canine interferon-γ was produced in the largest amount in silkworm. Two or more forms of interferons were produced due to various processing in silkworm. For feline interferon, two forms of protein molecule resulting from two different cleavage sites in signal peptide sequence was solved by reconstitution of a single amino acid in signal sequence. In the case of canine interferon- γ, several variations were produced due to glycosylation pattern and C-terminal degradation, but removal of glycosylation sites and elimination of C-terminal 16 amino acids sequence from native sequence lead to uniformity of the expressed protein. Drug formulated two recombinant animal interferons were approved as a treatment of viral diseases and atopic dermatitis by regulatory authorities. Especially, feline interferon is now sold in 20 countries including Japan and Europe.

Bombyx Mori Strains Useful for Efficient Recombinant Protein Production Using a Baculovirus Vector

The silkworm-baculovirus expression system is known as one of the most efficient methods for mass production of recombinant eukaryotic proteins. Many protein species, such as secretory, membrane, and nuclear proteins, are successfully expressed in this system and used for scientific research and industry. Several recent studies have greatly contributed to reducing the amount of time and labor required to generate recombinant viruses. Additionally, modifications of virus vectors have made this system a more attractive alternative for protein scientists. However, there are few reports on the screening and improvement of the silkworm, Bombyx mori, as a host insect. In this review, we describe an overview of the silkworm-baculovirus expression system and the improvement of silkworm as a host insect by the screening of silkworm bioresources and transgenic silkworm technology.

FMD subunit vaccine produced using a silkworm–baculovirus expression system: Protective efficacy against two type Asia1 isolates in cattle

Cattle vaccinated with a single dose of subunit vaccine containing the capsid and 3C proteinase coding regions of foot-and-mouth disease virus (FMDV) Asia I/HNK/CHA/05 strain were protected when challenged 28 days later with a homologous virus. Here, the 50% bovine protective dose (PD50) test was performed to assess the potency of the subunit vaccine. When challenged with two Chinese isolates, the subunit vaccine could achieve 6.5PD50 (challenged with Asia I/HNK/CHA/05 strain) and 5.2PD50 (challenged with Asia I/JSL/05 strain) per dose.

Expression of Foot-and-Mouth Disease Virus Capsid Proteins in Silkworm-Baculovirus Expression System and Its Utilization as a Subunit Vaccine

BackgroundFoot-and-mouth disease (FMD) is a highly contagious disease of livestock that causes severe economic loss in susceptible cloven-hoofed animals. Although the traditional inactivated vaccine has been proved effective, it may lead to a new outbreak of FMD because of either incomplete inactivation of FMDV or the escape of live virus from vaccine production workshop. Thus, it is urgent to develop a novel FMDV vaccine that is safer, more effective and more economical than traditional vaccines.Methodology and Principal FindingsA recombinant silkworm baculovirus Bm-P12A3C which contained the intact P1-2A and 3C protease coding regions of FMDV Asia 1/HNK/CHA/05 was developed. Indirect immunofluorescence test and sandwich-ELISA were used to verify that Bm-P12A3C could express the target cassette. Expression products from silkworm were diluted to 30 folds and used as antigen to immunize cattle. Specific antibody was induced in all vaccinated animals. After challenge with virulent homologous virus, four of the five animals were completely protected, and clinical symptoms were alleviated and delayed in the remaining one. Furthermore, a PD50 (50% bovine protective dose) test was performed to assess the bovine potency of the subunit vaccine. The result showed the subunit vaccine could achieve 6.34 PD50 per dose.ConclusionThe results suggest that this strategy might be used to develop the new subunit FMDV vaccine.

Oral administration activity determination of recombinant osteoprotegerin from silkworm larvae

Osteoprotegerin (OPG) regulates the formation of osteoclasts and is involved in the regulation of bone resorption and remodeling. To investigate the feasibility of using silkworm (Bombyx mori) larvae to produce recombinant osteoprotegerin as a oral administration drug, the rh-OPG was expressed in the larvae of silkworm through the silkworm baculovirus expression system, and was orally administered to mice. Compared with the control, oral administration of rh-OPG was effective to decrease serum calcium concentration in normal mice, and block the bone loss induced by the loss of estrogen in ovariectomized mice. These results indicated that oral administration of rh-OPG expressed in silkworm larvae had the proper bioactivity.

Development and Application of Chymase Inhibitors: Recombinant Human Chymase Produced by Silkworm-Baculovirus Expression System: Its Application for a Chymase Detection Kit

Human chymase is a mast cell-derived serine proteinase, which is a non-angiotensin converting enzyme angiotensin II-generating enzyme. It appears to participate in various diseases, but it is unclear whether chymase plays major roles in physiological and pathophysiological functions in vivo. To obtain information on the physiological and pathophysiological functions of chymase and to search for diseases in which chymase participates, in the present study, we aimed at producing recombinant human chymase in large quantities and at developing an ELISA system using anti-human chymase antibodies. A recombinant human chymase was produced by a silkworm-baculovirus expression system. The recombinant chymase in active form was efficiently purified from larval hemolymph using cation-exchange and heparin column chromatography. This recombinant enzyme was enzymatically identical with native human chymase. On the other hand, the stability of the recombinant enzyme in cultured medium for mammalian cells at 37 degrees C was very high as compared with the stability of the native enzyme; 20% of the activity was maintained 120 h after addition of medium. These results indicated that the recombinant enzyme could also utilize in vitro and in vivo assay systems. We obtained several anti-chymase monoclonal antibodies by using the recombinant human chymase as antigen. These antibodies were used to construct an ELISA system for measuring the chymase concentration in blood. As a result of preliminary examination using this ELISA system, it was shown that the chymase concentration in each serum from hypertensive patients is significantly higher than in normal serum. The ELISA system will be applicable for clinical diagnosis and in vivo evaluation systems for chymase-targeting drugs.