Endotoxins are common exogenous pyrogens. Excessive endotoxins in medical devices and injections can lead to serious consequences such as sepsis, septic shock, and even death. Therefore, endotoxin detection plays a crucial role in medical, pharmaceutical, and food sectors. The wide application of Limulus amebocyte lysate (LAL) has led to a sharp decline in the number of horseshoe crabs. Moreover, the LAL assay has limitations such as interbatch variations and difficulty in quantification. The recombinant factor C (rFC) assay is stable between batches, highly sensitive, and capable of quantitation, and thus it can be used as an alternative for the LAL assay. However, the high cost and complex procedures involved in producing recombinant factor C have limited the widespread application of this method. In order to simplify the preparation and reduce the production cost of recombinant factor C, this study focuses on the production of recombinant factor C based on the baculovirus expression system. Multiple measures such as a high-yield and anti-apoptotic vector qBac-IIIG, the optimal signal peptide, and the optimized codon were used to reach the goal of endotoxin detection with cell supernatant. This method simplifies the steps of protein purification. The sensitivity of the supernatant reached 0.05 EU/mL in a 1-L fermentation system, and 500 000 detecting reactions can be supported per liter of fermentation broth. This study increases the yield and activity of recombinant factor C, simplifies the procedures of protein purification, and reduces the cost, laying a foundation for the promotion and application of recombinant factor C in endotoxin detection.
Animals ; Recombinant Proteins/genetics* ; Horseshoe Crabs/chemistry* ; Baculoviridae/metabolism* ; Endotoxins/analysis* ; Protein C/biosynthesis* ; Genetic Vectors/genetics* ; Arthropod Proteins/genetics* ; Enzyme Precursors ; Serine Endopeptidases

Human keratinocyte growth factor-1 (hKGF-1), a member of the fibroblast growth factor (FGF) family, plays crucial roles in organ development, cell proliferation, wound healing, and tissue repair, representing one of the most effective and specific growth factors for skin repair. However, obtaining recombinant hKGF-1 remains challenging due to its universally low expression efficiency in vitro. This study employs the Bombyx mori baculovirus expression system to establish a technological platform that utilizes the economically important insect Bombyx mori as a bioreactor for high-efficiency and low-cost expression and production of recombinant human keratinocyte growth factor 1 (hKGF-1) protein, ultimately achieving high-level expression of hKGF-1 in Bombyx mori ovary cell line (BmN). In this study, we optimized the hKGF-1 sequence based on the codon preference of baculovirus. By fusing hKGF-1 with polyhedrin (highly expressed in this system) and adding extra promoters and enhancers, we significantly improved the expreesion level of hKGF-1 in Bombyx mori cells. The results demonstrated that the aforementioned strategies significantly enhanced the expression level of hKGF-1 in Bombyx mori cells. SDS-PAGE and Western blotting results revealed that the highest hKGF-1 expression (accounting for 8.7% of total cellular protein) was achieved when the Polh promoter was combined in tandem with the P6.9 promoter and hKGF-1 was fused with a 15-residue polyhedrin fragment for co-expression. The optimal harvest time was determined to be 120 h post transfection. This study achieved the efficient expression of hKGF-1 in Bombyx mori cells, establishing an ideal technological platform for the industrial utilization of recombinant hKGF-1. The developed methodology not only provides valuable technical references for the production of other growth factors and complex proteins, but also demonstrates significant implications for employing silkworms as bioreactors for recombinant human protein expression.
Bombyx/metabolism* ; Animals ; Baculoviridae/metabolism* ; Humans ; Fibroblast Growth Factor 7/biosynthesis* ; Recombinant Proteins/genetics* ; Cell Line ; Genetic Vectors/genetics*

Pseudorabies (PR) is an infectious disease caused by the pseudorabies virus (PRV), affecting various domesticated and wild animals. Since pigs are the only natural hosts of PRV, PR poses a serious threat to the pig farming industry. Currently, PR is primarily prevented through vaccination with inactivated vaccines or genetically modified attenuated live vaccines. Developing safe and effective genetically engineered vaccines would facilitate the eradication and control of PR. In this study, the PRV vaccine strain Bartha-K61 was used as the reference strain. The gB protein was expressed via the baculovirus-insect cell expression system. Non-denaturing gel electrophoresis confirmed that the gB protein could form a trimeric structure. The purified gB protein was used to immunize mice, and the immune effect was evaluated by a challenge test. The results showed that the gB antigen induced a strong immune response in mice, with the serum-neutralizing antibody titer above 1:70. The lymphocyte stimulation index reached more than 1.29, and the level of (interferon gamma, IFN-γ) release was higher than 100 pg/mL. After immunization, mice were challenged with the virus at a dose of 10⁴ TCID₅₀/mL, 200 μL per mouse, and the clinical protection rate was 100%. Immunohistochemistry, histopathological section, and tissue viral load results showed that the pathological damage and viral load in the gB-immunized group were significantly lower than those in the PBS group. In summary, the gB protein obtained in this study induced strong humoral and cellular immune responses in mice, laying a foundation for developing a recombinant gB protein subunit vaccine.
Animals ; Mice ; Baculoviridae/metabolism* ; Viral Envelope Proteins/biosynthesis* ; Herpesvirus 1, Suid/genetics* ; Pseudorabies/immunology* ; Swine ; Pseudorabies Vaccines/genetics* ; Antibodies, Viral/blood* ; Insecta/cytology* ; Mice, Inbred BALB C ; Female ; Viral Vaccines/immunology*

To obtain chicken CD40L protein, the cDNA was prepared from chicken splenic cells and used as a template to clone and amplify CD40L by PCR. The target gene was cloned into pFastBac vector to construct a pFastBac-chCD40L donor plasmid. Recombinant plasmid was transformed into DH10Bac and recombinant Bacmid-chCD40L was obtained. The Bacmid-chCD40L plasmid was transfected into sf9 insect cells to obtain His-chCD40L protein. In addition, the target gene was cloned into pQM01 vector to construct a pQM01-chCD40L plasmid, recombinant plasmid was transfected into HEK 293T cells to obtain Strep-chCD40L protein. The chCD40L protein was purified by affinity chromatography, and the concentration of purified chCD40L protein was determined to be 0.01 mg/mL. Primary cells were isolated from the bursal tissue of 3-week old SPF chickens, and the chCD40L protein was added to the culture medium to stimulate cells. The chCD40L could bind to CD40 on B cells as examined by Western blotting, indirect immunofluorescence assay and flow cytometry, suggesting that chCD40L protein is biologically active. We successfully obtained chicken CD40L protein of biological activity, which laid the foundation in the in vitro culture of primary B lymphocytes for the isolation and diagnosis of virulent IBDV.
Animals ; Baculoviridae/genetics* ; CD40 Ligand/genetics* ; Chickens ; Cloning, Molecular ; Genetic Vectors/genetics* ; Recombinant Proteins/genetics*

PURPOSE: Enzyme-linked immunosorbent assay (ELISA) has been used in the diverse field to evaluate influenza virus infection; for the surveillance, diagnosis, efficacy evaluation, and development of the vaccine. The aim of this study was to establish an ELISA for detecting HA strain-specific antibodies using recombinant pandemic A H1N1 (pH1N1) HA1 (rHA1) protein. MATERIALS AND METHODS: rHA1 was produced in baculovirus system. The clinical performance of the developed ELISA was validated using human serum samples, by comparison with standard methods for detecting a neutralizing antibody; hemagglutination inhibition (HI) assay and microneutralization test (MNT). The ability of the ELISA system to evaluate the efficacy test of an influenza vaccine was explored by measuring antibody levels in the serum of vaccinated mice. RESULTS: Our ELISA could detect anti-rHA1 antibody in influenza-infected patients and vaccinated subjects. Compared to HI assay and MNT as reference methods, our method showed good performance in detection of anti-rHA1 antibody. Detection of the anti-rHA1 antibody in vaccinated mice and its correlation with titers in HI assay was also proved in a mice model. CONCLUSION: An ELISA system using rHA1 of pH1N1 influenza virus was developed, and showed good clinical performance in diagnosis of influenza virus infection and evaluation of the vaccination efficacy in both human and animal models.
Animals ; Antibodies ; Antibodies, Neutralizing ; Baculoviridae ; Diagnosis ; Enzyme-Linked Immunosorbent Assay* ; Hemagglutination ; Humans ; Influenza A virus ; Influenza Vaccines ; Influenza, Human* ; Methods ; Mice ; Models, Animal ; Orthomyxoviridae* ; Pandemics* ; Vaccination

PURPOSE: Respiratory syncytial virus (RSV) can cause serious respiratory illnesses such as pneumonia, asthma, and bronchiolitis in infants and elderly or immunocompromised individuals. An RSV vaccine has yet to be developed; only prophylactic anti-RSV antibody is commercially available. So, we investigated whether our vaccine candidate is able to induce type 1 CD4+ T helper (Th1), CD8+ T-cell responses, and protective immunity without vaccine-enhanced disease (VED) against RSV. MATERIALS AND METHODS: We used RSV G protein fragment (Gcf A) with recombinant baculovirus capable of expressing the RSV M2 protein (Bac M2) as a vaccine candidate, and injected this vaccine (Gcf A/Bac M2) intramuscularly, and challenged with RSV intranasally into mice. Enzyme-linked immunosorbent assay, flow cytometry, plaque assay, and weight measurement were performed to confirm humoral immunity, cellular immunity, and protective immunity. RESULTS: The Gcf A/Bac M2 formulation induced a stronger IgG response to Gcf A than Gcf A inoculation alone, and the ratio of IgG1/IgG2a indicated that the responses shifted predominantly to Th1. In addition, both RSV G-specific Th1 responses and RSV M2-specific CD8+ T-cell responses were induced, and G protein-associated eosinophilic infiltration was suppressed compared to the control group. Moreover, the Gcf A/Bac M2 group showed effective protection after an RSV challenge. CONCLUSION: Bac M2 could serve as a vaccine with intrinsic adjuvant activity, and the Gcf A/Bac M2 shows promise as a vaccine candidate for inducing protective immunity without inciting VED.
Aged ; Animals ; Asthma ; Baculoviridae* ; Bronchiolitis ; Enzyme-Linked Immunosorbent Assay ; Eosinophils ; Flow Cytometry ; GTP-Binding Proteins* ; Humans ; Immunity, Cellular ; Immunity, Humoral ; Immunoglobulin G ; Infant ; Mice ; Pneumonia ; Respiratory Syncytial Viruses* ; T-Lymphocytes

PURPOSE: The aim of the present study was to develop a serodiagnostic test for differentiation infected from vaccinated animal (DIVA) strategy accompanying the marker vaccine lacking an immunodominant epitope (IDE) of nucleoprotein of Newcastle disease virus (NDV). MATERIALS AND METHODS: Recombinant epitope-repeat protein (rERP) gene encoding eight repeats of the IDE sequence (ETQFLDLMRAVANSMR) by tetra-glycine linker was synthesized. Recombinant baculovirus carrying the rERP gene was generated to express the rERP in insect cells. Specificity and sensitivity of an indirect enzyme-linked immunosorbent assay (ELISA) employing the rERP was evaluated. RESULTS: The rERP with molecular weight of 20 kDa was successfully expressed by the recombinant baculovirus in an insect-baculovirus system. The rERP was antigenically functional as demonstrated by Western blotting. An indirect ELISA employing the rERP was developed and its specificity and sensitivity was determined. The ELISA test allowed discrimination of NDV infected sera from epitope deletion virus vaccinated sera. CONCLUSION: The preliminary results represent rERP ELISA as a promising DIVA diagnostic tool.
Animals ; Baculoviridae ; Blotting, Western ; Discrimination (Psychology) ; Enzyme-Linked Immunosorbent Assay ; Insects ; Molecular Weight ; Newcastle disease virus* ; Newcastle Disease* ; Nucleoproteins ; Sensitivity and Specificity

As one of the most important aquatic fish, Micropterus salmoides suffers lethal and epidemic disease caused by rhabdovirus at the juvenile stage. In this study, a new strain of M. salmoides rhabdovirus (MSRV) was isolated from Yuhang, Zhejiang Province, China, and named MSRV-YH01. The virus infected the grass carp ovary (GCO) cell line and displayed virion particles with atypical bullet shape, 300-500 nm in length and 100-200 nm in diameter under transmission electron microscopy. The complete genome sequence of this isolate was determined to include 11 526 nucleotides and to encode five classical structural proteins. The construction of the phylogenetic tree indicated that this new isolate is clustered into the Vesiculovirus genus and most closely related to the Siniperca chuatsi rhabdovirus. To explore the potential for a vaccine against MSRV, a glycoprotein (1-458 amino acid residues) of MSRV-YH01 was successfully amplified and cloned into the plasmid pFastBac1. The high-purity recombinant bacmid-glycoprotein was obtained from DH10Bac through screening and identification. Based on polymerase chain reaction (PCR), western blot, and immunofluorescence assay, recombinant virus, including the MSRV-YH01 glycoprotein gene, was produced by transfection of SF9 cells using the pFastBac1-gE2, and then repeatedly amplified to express the glycoprotein protein. We anticipate that this recombinant bacmid system could be used to challenge the silkworm and develop a corresponding oral vaccine for fish.
Animals ; Baculoviridae/metabolism* ; Bass/metabolism* ; Carps/virology* ; Cell Line ; Female ; Genetic Techniques ; Genome, Viral ; Glycoproteins/biosynthesis* ; Insecta ; Ovary/virology* ; Phylogeny ; Plasmids/metabolism* ; Recombinant Proteins/biosynthesis* ; Rhabdoviridae/metabolism*

Baculovirus expression vector system (BEVS) has been successfully applied to the over-expression of various proteins, thus providing sufficient materials for vaccine research. Compared to other systems, BEVS has many advantages: baculovirus solely being parasitic in invertebrates, the resultant products conferring high safety to mammalian, high expression level of recombinant proteins, preferable folding for eukaryotic protein, proper post-translational modification required for biological function, suitable for multiple genes co-expression and large-scale production with serum-free culture media. To better understand the advantages and prospective of BEVS for the vaccine research, this article will review the development of BEVS and its application on vaccine research.
Animals ; Baculoviridae ; Genetic Vectors ; Prospective Studies ; Recombinant Proteins ; Vaccines

PLCζ is a new isoenzyme of the PLC family which plays an important role in activating mammalian oocytes. In recent years, large-scale expression and purification of active PLCζ protein in vitro for structural biology research has not been successful. In this study, the recombinant human PLCζ protein was expressed and purified in the baculovirus expression system. First, the full length of human PLCζ gene was cloned into the pFastBac-HTA plasmid to form the recombinant donor plasmid that was further transformed into DH10Bac Escherichia coli cells to construct the recombined bacmid by the site-specific transposition that was screened by resistance and blue-white spots. Then the bacmid was transfected to Sf9 insect cells via cellfectin to package the recombinant baculovirus. After the amplification of the recombinant baculovirous, the recombinant protein was expressed from the cells transduced by the recombinant baculovirus and was purified by Ni-NTA resin. Purified protein was identified by Western blotting and time-of-flight mass spectrometry and the enzyme activity was determined. The results showed that the recombinant PLCζ protein in the Sf9 cells was achieved at 72 hours after baculovirus infection and expressed in secreted form in cell culture medium. The recombinant protein purified by Ni²⁺ affinity column was identified as PLCζ by Western blotting and ionization time-of-flight mass spectrometry and the enzyme activity was up to 326.8 U/mL. The experimental results provide a reference for the large-scale production and biological application of recombinant human PLCζ protein.
Animals ; Baculoviridae ; Genetic Vectors ; Humans ; Recombinant Proteins ; Sf9 Cells ; Spodoptera