Production of biologically active recombinant bovine interferon-gamma by two different baculovirus gene expression systems using insect cells and silkworm larvae

A simple method for recombinant protein purification using self-assembling peptide-tagged tobacco etch virus protease

Recombinant protein purification remains to be a major challenge in biotechnology and medicine. In this paper we report a simple method for recombinant protein purification using self-assembling peptide-tagged tobacco etch virus protease (TEVp). After construction of an N-terminal ELK16 peptide fusion expression vector, we expressed ELK16-TEVp fusion protein in E. coli. SDS-PAGE analysis showed that ELK16-TEVp was expressed as active protein aggregates which could be purified to 91% purity with 92% recovery by centrifugation in the presence 0.5% Triton X-100. By using His-tagged bovine interferon-γ (His-BoIFN-γ) as the substrate, we demonstrated that EKL16-TEVp had a protease activity of 1.3 × 10(4) units/mg protein with almost 100% cleavage efficiency under the optimized conditions. More importantly, EKL16-TEVp could be removed from the cleavage reaction by single-step centrifugation. After removing the His-tag by nickel-conjugated agarose bead absorption, the recombinant BoIFN-γ (rBoIFN-γ) was purified to 98.3% purity with 63% recovery. The rBoIFN-γ had an antiviral activity of 1.6 × 10(3) units/mg protein against vesicular stomatitis virus. These data suggest that ELK16-TEVp may become a universal tool for recombinant protein purification.

Generation and application of a 293 cell line stably expressing bovine interferon-gamma

A stable mammalian cell line expressing highly active bovine interferon-gamma (BoIFN-γ) was generated using Flp recombinase-mediated integration. This recombinant 293 cell line (B1) efficiently secreted FLAG-tagged BoIFN-γ protein into the culture supernatant, as determined by ELISA and Western blot. The recombinant BoIFN-γ exhibited high anti-viral activity, suggesting that the 293 cells expressed BoIFN-γ that structurally and biologically resembled the natural protein. Two monoclonal antibodies (mAbs) with high affinity for the 293 cell-expressed BoIFN-γ were identified using this cell line, and these mAbs can be used for the development of diagnostic kits. Thus, this work demonstrates the successful generation of a 293 cell line that produces large quantities of highly active BoIFN-γ and demonstrates its potential application in the research of bovine infectious diseases.

Biological activity of recombinant bovine interferon τ produced by a silkworm-baculovirus gene expression system

Bovine interferon (bIFN) τ plays a crucial role in maternal-fetal recognition and was expressed using a Bombyx mori (Bm) nuclear polyhedrosis virus (silkworm baculovirus) gene expression system. The biological effects of Bm-recombinant bIFNτ (rbIFNτ) on prostaglandin (PG) F_2α synthesis were investigated in cultured bovine endometrial epithelial cells with oxytocin (OT, 100 nM) and on the in vitro development of bovine embryos. Bm-rbIFNτ and OT were shown to suppress PGF_2α production in a dose-dependent manner. When in vitro produced morula stage embryos were cultured for 72 hr in modified CR1aa medium supplemented with or without rbIFNτ, Bm-rbIFNτ (10 ng/ml) significantly promoted development to the expanded blastocyst stage. In conclusion, Bm-rbIFNτ was suggested to have the same bioactivity as native IFNτ.

Introduction to advanced biologics

The changing structure and environment of the animal industry have brought about the need for new-generation vaccines, therapeutic methods, and diagnostic methods. This review briefly explains the present situation and future prospects of advanced biologics.

Stability of recombinant bovine interferon-γ antiviral activity in the absence of stabilizing additives

The stability of recombinant bovine interferon-γ (rbIFN-γ) produced by a baculovirus expression system was investigated under different storage conditions: freezing-thawing and storage for 30 days at temperatures of -80, 4, 25, and 37°C. Antiviral activity was not significantly decreased by freeze-thawing at least five times. Furthermore, although not statistically different, antiviral activity gradually decreased as temperature increased. These findings suggest that rbIFN-γ possesses high thermal and freeze-thaw stability.

Development of efficient method for purified recombinant bovine granulocyte-macrophage colony-stimulating factor production with baculovirus-silkworm gene expression system

Recombinant bovine granulocyte-macrophage colony-stimulating factor (rboGM-CSF) was produced by the baculovirus-silkworm expression system. It was purified to 98% by (NH(4))(2)SO(4), followed by a three-step column chromatography with silica gel, ion exchange resin and a metal chelate column. The specific activity of purified rboGM-CSF was 1.6-6.3 x 10(6) ED(50) mg(-1). By this method, the specific activity was raised 160-fold and 21% of the expressed rboGM-CSF was recovered.

Production of an active feline interferon in the cocoon of transgenic silkworms using the fibroin H-chain expression system

We constructed the fibroin H-chain expression system to produce recombinant proteins in the cocoon of transgenic silkworms. Feline interferon (FeIFN) was used for production and to assess the quality of the product. Two types of FeIFN fusion protein, each with N- and C-terminal sequences of the fibroin H-chain, were designed to be secreted into the lumen of the posterior silk glands. The expression of the FeIFN/H-chain fusion gene was regulated by the fibroin H-chain promoter domain. The transgenic silkworms introduced these constructs with the piggyBac transposon-derived vector, which produced the normal sized cocoons containing each FeIFN/H-chain fusion protein. Although the native-protein produced by transgenic silkworms have almost no antiviral activity, the proteins after the treatment with PreScission protease to eliminate fibroin H-chain derived N- and C-terminal sequences from the products, had very high antiviral activity. This H-chain expression system, using transgenic silkworms, could be an alternative method to produce an active recombinant protein and silk-based biomaterials.

Expression cloning of gamma interferon-inducing antigens of Mycobacterium avium subsp. paratuberculosis

Three recombinant proteins, Map10, Map39, and Map41, produced based on nucleotide sequences obtained from the screening of Mycobacterium avium subsp. paratuberculosis genomic library expressed in Escherichia coli significantly elicited gamma interferon production in peripheral blood mononuclear cells from infected cattle. Two of these proteins were members of the PPE protein family.

High-level expression of recombinant 3AB1 non-structural protein from FMDV in insect larvae

For its potential usefulness in diagnosis, the non-structural protein 3AB1 from foot-and-mouth disease virus was expressed as a soluble protein by using Autographa californica nuclear polyhedrosis virus as a vector. The 3AB1 coding sequence was introduced into AcNPV genome via pBAcPAK3AB1 transfer vector to originate Ac3AB1 recombinant baculovirus of phenotype occ-. Rachiplusia nu larvae were injected with supernatants of Sf9 cells infected with Ac3AB1 and 5 days post-infection total protein extracts were obtained. An intense band of approximately 21.5 kDa was observed when total larvae extracts were SDS-PAGE resolved and the recombinant protein detected by an FMDV-infected guinea pig serum. ELISA tests and Western blot experiments were carried out using sera both from FMDV-infected cattle and from vaccinated animals. The recombinant protein was only recognized by sera from infected animals, suggesting that this method of production in insect larvae could be applied to an efficient mass production of proteins of diagnostic interest.

Increase in gammadelta T cells in the blood of cattle persistently infected with bovine leukemia virus following administration of recombinant bovine IFN-gamma

To examine the effect of recombinant bovine interferon-gamma (rbIFN-gamma) on cattle persistently infected with bovine leukemia virus (BLV), BLV-infected cattle were inoculated intraperitoneally with IFN-gamma. All cattle were febrile after inoculation with IFN-gamma and then recovered within 48 h. Flow cytometric analysis showed that the numbers of CD4+ and CD8+ T cells were decreased for 2-3 days and then their numbers were recovered. The number of gammadelta T cells increased after the fever. In contrast, the number of IgM+ lymphocytes remained low for about 1 week. Moreover, the numbers of syncytia produced by peripheral blood lymphocytes decreased and remained low compared to that before IFN-gamma administration. These results suggest that IFN-gamma induces the up-regulation of gammadelta T cells, decreases the number of IgM+ lymphocytes and suppresses the growth of BLV in BLV-infected cattle in vivo.

Generation of Multinucleated Giant Cells In Vitro from Bovine Monocytes and Macrophages

The generation of multinucleated giant cells (MGC) from cells of the bovine monocyte-macrophage lineage was investigated. Freshly isolated monocytes were incubated with the conditioned medium (CM) of peripheral blood mononuclear cell cultures treated with Concanavalin A for 1-4 days (CM1 to CM4). Only CM1 generated MGC despite similar concentrations of IFNgamma in all CMs. Nevertheless, MGC formation from monocytes was enhanced by adding either macrophage colony-stimulating factor (M-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF), MGC formations from macrophages were observed only when macrophages were cultured with GM-CSF plus CM. These results indicate that several mechanisms to generate MGC from bovine monocytes-macrophage lineage cells exist, and that GM-CSF is a major mediator of MGC formation in cattle.

N-linked glycan structures of mouse interferon-β produced by Bombyx mori larvae

The full-length mouse interferon-beta (mIFN-beta) cDNA, including the secretion signal peptide coding region under control of the polyhedrin promoter, was introduced into Bombyx mori nucleopolyhedrovirus (BmNPV). Recombinant mIFN-beta (rmIFN-beta) was accumulated in the haemolymph of infected silkworm larvae. Western blot analysis showed isoforms of rmIFN-beta, suggesting that rmIFN-beta is glycosylated. The glycan structures of purified rmIFN-beta were determined. The N-glycans were liberated by hydrazinolysis and the resulting oligosaccharides were labeled with 2-aminopyridine. The pyridylaminated (PA) glycans were purified by gel filtration, reversed-phase HPLC, and size-fractionation HPLC. The structures of the PA-sugar chains were identified by a combination of two-dimensional PA-sugar chain mapping, MS analysis, and exoglycosidase digestions.

Quantitation of bovine macrophage colony-stimulating factor in bovine serum by ELISA

We established an enzyme-linked immunosorbent assay (ELISA) system for the quantitation of bovine macrophage colony-stimulating factor (M-CSF) and used it to measure the serum M-CSF levels in bovine fetuses and calves. The average serum M-CSF level was 2.7+/-1.5 ng/ml in 39 calves under 100 days old, and 1.8+/-0.8 ng/ml in 15 cattle between 101 and 418 days old. Fetal sera samples (n = 6) prepared from cattle between 150 and 280 days of gestational age had a higher average level of M-CSF (8.8+/-1.4 ng/ml). Alteration in serum M-CSF levels in each individual calf was also measured. The serum levels of M-CSF in calves at 0-1 day after birth ranged from 0.52 to 7.3 ng/ml. During the period 113-125 days after birth, serum levels were around 1.4+/-0.39 ng/ml. Although serum M-CSF levels generally decreased as the age of calves advanced, differences among individuals, especially among newborn calves, were observed.

Purification and diagnostic utility of a recombinant hepatitis E virus capsid protein expressed in insect larvae

We report here the expression and purification of a truncated form of the hepatitis E virus ORF2 protein (ORF2delta111/deltaTM), from the fat bodies of Spodoptera litura larvae infected with a recombinant baculovirus. The purified protein migrated as a doublet of approximately 56 kDa on SDS-PAGE and was found to be glycosylated by staining with concanavalin A-linked horseradish peroxidase. The protein was used in a sensitive and specific enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to HEV. The results showed complete concordance with those obtained using a commercial kit for the detection of anti-HEV antibodies. Antigen expression in the insect larvae system presents a rapid and low-cost method that obviates the need for expensive tissue culture scale-ups or special equipment.

Expression of biologically active recombinant equine interferon-gamma by two different baculovirus gene expression systems using insect cells and silkworm larvae

The full-length equine interferon-gamma (eIFN-gamma) cDNA, including the secretion signal peptide coding region, was recloned into baculovirus transfer vector pAcYM1. This vector was co-transfected with Autographa californica nuclear polyhedrosis virus DNA or hybrid nuclear polyhedrosis virus DNA into Spodoptera frugiperda cells. The recombinant viruses, named AcEIFN-gamma and HyEIFN-gamma, were then recovered. Recombinant eIFN-gamma (reIFN-gamma) was accumulated in the culture fluid of the AcEIFN-gamma or HyEIFN-gamma infected Tricoplusia ni -derived cell line, BTI TN 5B1-4, and hemolymph of HyEIFN-gamma infected silkworm larvae. These reIFN-gamma forms were shown to be 14, 16, 18 and 20kDa proteins, and glycosylated as confirmed by SDS-PAGE and tunicamycin treatment. Both reIFN-gamma proteins, showed high-level biological activities to vesicular stomatitis virus by cytopathic effect reduction assay, and MHC class II antigen induction on the equine fetal kidney-78 cell line.

High level expression of C-terminal truncated recombinant chicken interferon-gamma in baculovirus vector system

Chicken interferon-gamma (ChIFN-gamma) was expressed by baculovirus in a C-terminal truncated form, namely ChIFN-gammaT, to accelerate the secretion of the expressed protein. It is also expressed as ChIFN-gammaT bearing poly His tag, ChIFN-gammaTHis, for easy purification. The expressed proteins were detected by SDS-PAGE analysis with Coomassie brilliant blue staining. The purified ChIFN-gammaTHis with nickel chelated column showed anti-viral activity in vitro and stimulation of the secretion of nitrogen intermediates such as nitric oxide in chicken peripheral blood mononuclear cells. Antiserum against ChIFN-gammaTHis recognized the 15 kDa, 16 kDa, and 32 kDa bands that seemed to be an unglycosylated monomer, a glycosylated monomer, and a homodimer of ChIFN-gammaTHis in the culture supernatant, respectively. The anti-serum also recognized around 14 kDa and 28 kDa bands in the sera of chickens or concanavalin A stimulated spleen cell culture supernatants that seemed to be monomeric and dimeric forms of a natural ChIFN-gamma, respectively.

Anti-viral effect of recombinant bovine interferon gamma on bovine leukaemia virus

The antiviral activity of recombinant bovine interferon gamma (rbIFN-gamma) against bovine leukaemia virus (BLV) was evaluated by an in vitro assay. rbIFN-gamma was prepared using a baculovirus expression system and replication of BLV was measured by syncytium assay. Antiviral effects were observed when bovine and sheep cells were used as target cells or effector cells and treated with 0.1 unit/ml of rbIFN-gamma. Formed syncytium numbers were reduced less than 1/20 when these cells were treated with 10 units/ml of rbIFN-gamma. However, the antiviral effects on cells of heterologous species were decreased and more than 1000 units/ml of rbIFN-gamma were required to induce an anti-BLV effect on the combination of CC81 cells as target cells and Bat2Cl6 cells as effector cells, which originated from the cat and bat, respectively. When the degree of BLV production was estimated by reverse transcriptase (RT) activity, no antiviral effect of rbIFN-gamma was induced soon after the treatment, but it was evident in the cells persistently infected with BLV. These results showed that rbIFN-gamma suppresses the replication of BLV in vitro, but has effective biological activity on cells of homologous species.