Production of canine IFN-gamma in silkworm by recombinant baculovirus and characterization of the product

Structural insight and stability of TNFR-Fc fusion protein (Etanercept) produced by using transgenic silkworms

Therapeutic proteins expressed using transgenic animals have been of great interest for several years. Especially, transgenic silkworm has been studied intensively because of its ease in handling, low-cost, high-yield and unique glycosylation patterns. However, the physicochemical property of the therapeutic protein expressed in transgenic silkworm remains elusive. Here, we constructed an expression system for the TNFR-Fc fusion protein (Etanercept) using transgenic silkworm. The TNFR-Fc fusion protein was employed to N-glycan analysis, which revealed an increased amount of afucosylated protein. Evidence from surface plasmon resonance analysis showed that the TNFR-Fc fusion protein exhibit increased binding affinity for Fcγ receptor IIIa and FcRn compared to the commercial Etanercept, emphasizing the profit of expression system using transgenic silkworm. We have further discussed the comparison of higher order structure, thermal stability and aggregation of the TNFR-Fc fusion protein.

Production of biologically active feline interferon beta in insect larvae using a recombinant baculovirus

Feline interferon beta is a cytokine that belongs to the type I IFN family, with antitumor, antiviral and immunomodulatory functions. In this work, recombinant feline interferon beta (rFeIFNβ) was expressed in insect larvae that constitute important agronomic plagues. rFeIFNβ accumulated in the hemolymph of Spodoptera frugiperda larvae infected with recombinant baculovirus and was purified by Blue-Sepharose chromatography directly from larval homogenates on day 4 post-infection. rFeIFNβ was recovered after purification with a specific activity of 1 × 10⁶ IU mg^-1. By this method, we obtained 8.9 × 10⁴ IU of purified rFeIFNβ per larva. The product was biologically active in vitro, with an antiviral activity of 9.5 × 10⁴ IU mL^-1, as well as a potent antitumor activity comparable to that of the commercial FeIFNω. The glycosylation of rFeIFNβ was confirmed by peptide-N-glycosidase F digestion. Our findings provide a cost-effective platform for large-scale rFeIFNβ production in laboratory research or veterinary medicine applications.

Characterization of anti-CD20 monoclonal antibody produced by transgenic silkworms (Bombyx mori)

In response to the successful use of monoclonal antibodies (mAbs) in the treatment of various diseases, systems for expressing recombinant mAbs using transgenic animals or plants have been widely developed. The silkworm (Bombyx mori) is a highly domesticated insect that has recently been used for the production of recombinant proteins. Because of their cost-effective breeding and relatively easy production scale-up, transgenic silkworms show great promise as a novel production system for mAbs. In this study, we established a transgenic silkworm stably expressing a human-mouse chimeric anti-CD20 mAb having the same amino acid sequence as rituximab, and compared its characteristics with rituximab produced by Chinese hamster ovary (CHO) cells (MabThera®). The anti-CD20 mAb produced in the transgenic silkworm showed a similar antigen-binding property, but stronger antibody-dependent cell-mediated cytotoxicity (ADCC) and weaker complement-dependent cytotoxicity (CDC) compared to MabThera. Post-translational modification analysis was performed by peptide mapping using liquid chromatography/mass spectrometry. There was a significant difference in the N-glycosylation profile between the CHO- and the silkworm-derived mAbs, but not in other post-translational modifications including oxidation and deamidation. The mass spectra of the N-glycosylated peptide revealed that the observed biological properties were attributable to the characteristic N-glycan structures of the anti-CD20 mAbs produced in the transgenic silkworms, i.e., the lack of the core-fucose and galactose at the non-reducing terminal. These results suggest that the transgenic silkworm may be a promising expression system for the tumor-targeting mAbs with higher ADCC activity.

Hypermethylation of the death-associated protein kinase CpG island in canine B-cell lymphoid tumors

Death-associated protein kinase (DAPK) is a 160-kD serine/threonine kinase known as a key molecule in interferon-γ (IFN-γ)-induced apoptosis and tumor suppression. Hypermethylation of the CpG island in DAPK inactivates the gene in a variety of human malignancies. This study aimed to detect the inactivation of DAPK in canine lymphoid tumor cells. The sequence of canine DAPK cDNA was obtained from normal dog peripheral blood mononuclear cells after reverse transcription polymerase chain reaction (RT-PCR). By rapid amplification of 5'-cDNA ends, the transcription initiation site of the DAPK gene was identified. The CpG island located upstream of the translation initiation site was identified by using a search algorithm. The methylation status of the CpG island was examined using bisulfite sequence analysis and methylation-specific PCR (MSP). The inactivation of DAPK gene was examined in 3 canine lymphoid tumor cell lines, GL-1 (B-cell leukemia), CLBL-1 (B-cell lymphoma), and CL-1 (T-cell lymphoma). DAPK mRNA expression was measured by real-time RT-PCR. IFN-γ-induced apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay. The influence of demethylation was examined with 5-aza-2'-deoxycytidine (5-aza-dC). The methylation status in 14 dogs with various lymphoid tumors was screened by MSP. A 1926-bp CpG island containing 280 CpG repeats was identified upstream of the translation start site of canine DAPK. Bisulfate sequence analysis and MSP revealed hypermethylation of the CpG island in GL-1 cells, but not in CLBL-1 or CL-1 cells. The amount of DAPK mRNA was significantly smaller in GL-1 cells than CLBL-1 and CL-1 cells. IFN-γ-induced apoptosis was detected in CLBL-1 and CL-1 cells but not in GL-1 cells. Treatment with 5-aza-dC significantly increased the amount of DAPK mRNA and IFN-γ-induced apoptosis in GL-1 cells. These results revealed the inactivation of DAPK through methylation of its CpG island in GL-1 cells. MSP showed hypermethylation of the DAPK CpG island in 5 of 8 primary B-cell lymphoma samples, but not in any of the 6 primary T-cell lymphoid tumor samples obtained from canine patients. DAPK was inactivated through hypermethylation of its CpG island in canine B-cell lymphoid tumor cells. This study will lead to the use of canine B-cell lymphoid tumors as an animal model to evaluate the efficacy of demethylating agents.

Inhibitory effect of interferon gamma on frequency of Ehrlichia canis-infected cells in vitro

Ehrlichia canis is an obligate intracellular bacterium that infects the macrophage-monocyte cells of dogs, causing canine monocytic ehrlichiosis. Interferon-γ (IFN-γ), along with other cytokines, mediates the immune response to such intracellular bacterial invasions. To determine the role of IFN-γ in the immunity of dogs to E. canis infection, peripheral blood mononuclear cells (PBMC) and white blood cells (WBC) were collected from E. canis-infected dogs and added to a culture of E. canis in DH82 cells. The number of E. canis inclusion-positive cells was significantly reduced in cultures containing PBMC and WBC from E. canis-infected dogs compared to uninfected dogs. However, this resistance was inhibited by the addition of an anti-dog IFN-γ antibody. Resistance was also observed when PBMC were added to the Cell Culture Inserts, which prohibited contact of PBMC to DH82 cells, while allowed the diffusion of soluble cell products. The results of this study indicate that resistance was not dependent on cell to cell contact, but was associated with soluble cell products, such as IFN-γ. The addition of recombinant canine IFN-γ to the E. canis culture also reduced the number of infected cells. A commercial recombinant canine IFN-γ, which is sold in Japan, was also effective at reducing E. canis-infected cell number. These results indicate that IFN-γ has an inhibitory effect on the frequency of E. canis-infected cells in vitro and that contact between effector and target cells is not necessary for the resistance.

Low-dose recombinant canine interferon-gamma for treatment of canine atopic dermatitis: an open randomized comparative trial of two doses

The purpose of this study was to investigate the minimum effective dose of recombinant canine interferon-gamma (rCaIFN-gamma) for the treatment of dogs with atopic dermatitis (AD). Thirty-four dogs with AD from 17 animal hospitals in Japan were administered half or one-fifth of the approved rCaIFN-gamma dose of 10 000 units/kg, three times a week for 4 weeks, followed by once weekly for an additional 4 weeks. Pruritus, excoriation, erythema and alopecia were evaluated and scored by the investigators on weeks 2, 4, 6, 8 and 12. The efficacy rate (number of excellent cases + number of good cases/total number of cases) at week 8 in the 2000 units/kg group was 36.4% for pruritus, 36.4% for excoriation, 45.5% for erythema and 36.4% for alopecia. In contrast, in the 5000 units/kg group, the efficacy rate was 64.3% for pruritus, 57.1% for excoriation, 78.6% for erythema and 78.6% for alopecia. The efficacy rate of the 5000 units/kg group was high for all signs evaluated and comparable to that of the 10 000 units/kg group reported in a previous study. The results of this study showed that 2000 units/kg of rCaIFN-gamma is less effective than 5000 units/kg to treat dogs with AD, and the efficacy of the 5000 units/kg dose is comparable to that of 10 000 units/kg at week 8.

Expression of two heterologous proteins depends on the mode of expression: comparison of in vivo and in vitro methods

The yield of two proteins, avidin and green fluorescent protein (GFP), expressed from a modified Autographa californica nucleopolyhedrovirus (AcMNPV), was compared in Sf9 cell culture monolayer, Sf21 cell suspension culture and intact Spodoptera litura larvae. GFP expressed from the p10 promoter yielded up to 1.5% of total soluble protein in larvae, 20-fold higher than that in monolayer suspension culture. Avidin, expressed from the polh promoter, yielded up to 2.3% of total soluble protein in larvae, 10-fold higher than that in suspension culture and 40-fold higher than that in monolayers. Avidin expression did not affect amounts of GFP in dual-expressing baculovirus compared with those detected from a GFP-only expressing AcMNPV. A biotin-binding assay showed that all avidin expressed in larvae was fully active. Glycosylation patterns of chicken-avidin and Spodoptera-avidin were very similar, though the latter showed a proportion of partially glycosylated material.

Efficient production of canine interferon-alpha in silkworm Bombyx mori by use of a BmNPV/Bac-to-Bac expression system

We exploited the silkworm Bombyx mori for the production of recombinant canine interferon-alpha (CaIFN-alpha). The recombinant baculovirus harboring canine interferon gene was rapidly generated by the BmNPV/Bac-to-Bac system that was recently developed. In B. mori-derived cell lines, the expression of the recombinant protein reached maximal levels around 72-96 h post-infection. For the isolation of the expressed recombinant protein from B. mori larvae, the whole bodies of the infected larvae were homogenized, and the expressed protein was purified by affinity chromatography. Based on the fact that the recombinant CaIFN-alpha showed two bands on the sodium dodecyl sulfate polyacrylamide gel electrophoresis pattern, the expressed protein was thought to be glycosylated. The rCaIFN-alpha yield was about 528 microg per larva, showing that the expression in silkworm was successful. Furthermore, the recombinant protein was proven to be able to inhibit the infection of Madin-Darby canine kidney cells by the vesicular stomatitis virus, indicating that it is biologically active in vitro. The method established in this study provides an efficient way to produce a large amount of CaIFN-alpha and paves the way for further utilization of this protein as a therapeutic agent or vaccine adjuvant in dogs.

A Case of Hyperplastic Dermatosis of the West Highland White Terrier Controlled by Recombinant Canine Interferon-.GAMMA. Therapy

A 3.5-year-old, male West Highland White Terrier was diagnosed as having hyperplastic dermatosis by clinical and histopathological findings. Controlling of Malassezia overgrowth by antifungal drugs provided a temporal improvement of the skin lesions, but the disease was deteriorated within the next 2 months despite the negative demonstration of the yeasts. Induction of recombinant canine interferon-gamma (rCaIFN-gamma) therapy resulted in almost complete cure of the skin lesions within 2 months after the initiation of the therapy. No adverse effects were detected during the therapy. Our results suggested that the rCaIFN-gamma therapy is potential to be a novel therapeutic option for controlling the breed-specific hyperplastic skin disease.

A randomized comparative clinical trial of recombinant canine interferon-gamma (KT-100) in atopic dogs using antihistamine as control

Recombinant canine interferon-gamma (KT-100) or topical antihistamine (diphenhydramine: DH) was administered to dogs with atopic dermatitis (AD) for 4 weeks and their efficacies were compared using pruritus, excoriation, erythema and alopecia as evaluation criteria. Clinical studies on 92 atopic dogs (KT-100 group: 63, DH group: 29) were conducted at 18 animal hospitals in Japan. KT-100 was administered subcutaneously once a day three times a week on alternating days for 4 weeks. DH was administered topically twice daily for 4 weeks. The efficacy rates of the KT-100 group on day 28 were 72.1% for pruritus, 73.8% for excoriation, 75.4% for erythema and 60.7% for alopecia, which were significantly higher than those of the DH group (20.7% for pruritus, 27.6% for excoriation, 24.1% for erythema and 24.1% for alopecia).

Interleukin-12 augments a Th1-type immune response manifested as lymphocyte proliferation and interferon gamma production in Leishmania infantum-infected dogs

The dog is the major reservoir for human visceral leishmaniasis caused by Leishmania infantum. Interleukin-12 is considered to have an essential role in the development of both innate and adaptive immunity to Leishmania spp. and other intracellular pathogens. This study focused on the influence of IL-12 in experimental and natural canine visceral leishmaniasis. Responses of peripheral blood mononuclear cells to IL-12, interleukin-10 and Leishmania soluble antigen were evaluated in L. infantum experimentally infected oligosymptomatic beagles, uninfected beagles, naturally infected polysymptomatic dogs, and their matched uninfected controls. Leishmania soluble antigen induced strong peripheral blood mononuclear cells proliferation both in experimentally infected dogs (median stimulation index [SI]=15.01), and in naturally infected dogs (SI=8.86), but not by cells from the control groups. IL-12 addition further enhanced cell proliferation in naturally (SI=14.95), but not in experimentally infected animals. Peripheral blood mononuclear cells from experimentally infected dogs were able to produce significant amounts of IFN-gamma (3.39 ng/ml) upon LSA stimulation, but no such production was detected in cells from naturally infected or control animals. Interestingly, addition of IL-12 reversed the inhibitory effect of LSA on IFN-gamma production by cells from polysymptomatic naturally infected dogs and the uninfected beagles (4.84 and 7.45 ng/ml, respectively), and further increased IFN-gamma production by peripheral blood mononuclear cells from experimentally infected oligosymptomatic dogs (29.28 ng/ml). IFN-gamma mRNA expression correlated well with IFN-gamma production. Addition of IL-10 to Leishmania soluble antigen stimulated peripheral blood mononuclear cells inhibited proliferation and IFN-gamma production in experimentally infected dogs. Thus, the ability of IL-12 to augment IFN-gamma production by peripheral blood mononuclear cells from dogs with experimental or natural symptomatic canine visceral leishmaniasis makes it a good candidate for cytokine therapy in dogs that are refractory to current therapy.

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.