In order to achieve large-scale production of HSV-IgM (HSV1, HSV2) human-mouse chimeric antibody in vitro, the gene sequence of the corresponding hybridoma cell was harvested by RNA ligase-mediated rapid amplification of cDNA ends (RLM-RACE) technique to clone the chimeric antibody into eukaryotic expression vectors, and express the target proteins in CHO-S cells. At the same time, the screening process of stable cell lines was optimized, and the pressure conditions of pool construction stage and monoclonal screening stage were explored. Finally, the target protein was purified by protein L affinity purification method and the biological activity was detected. The recombinant IgM antibodies, HSV1 and HSV2, weighted at 899 kDa and 909 kDa respectively, were prepared. The optimal screening pressure was 20P200M (the first phase of pressure) and 50P1000M (the second phase of pressure). The final titer for the monoclonal expression of HSV1-IgM and HSV2-IgM was 1 620 mg/L and 623 mg/L, respectively. This study may facilitate the development of quality control products of HSV1 and HSV2 IgM series recombinant antibodies as well as efficient expression of IgM subtype antibodies in vitro.
Cricetinae ; Humans ; Animals ; Mice ; Immunoglobulin M/genetics* ; Antibodies, Viral ; CHO Cells ; Cricetulus ; Hybridomas ; Recombinant Fusion Proteins

Objective To investigate the preventive therapeutic effect and possible mechanism of single chain variable fragments chimeric protein (SD) of ovalbumin epitopes internalizing receptor DEC-205 antibody on food allergy in mice. Methods Mice were randomly divided to five groups (control, PBS, scFv DEC 100 μg, SD 50 μg, SD 100 μg) and treated for 24 hours before OVA administration. After challenge, the serum level of OVA-specific IgE, IgG1, IgG2a and IL-4 were detected by ELISA. Infiltration of eosinophils and mast cells in the jejunum was observed by HE staining and toluidine blue staining respectively. The bone marrow of tibia and femur was isolated and cultured to obtain immature dendritic cells(BMDCs), which were further treated with LPS (10 ng/mL), TSLP (50 ng/mL), scFv DEC protein (1000 ng/mL) and SD protein (10,100,1000)ng/mL for 24 hours, and the IL-10 level of supernatant was assayed by ELISA. Results Compared with PBS group, the number of SD-treated mice with diarrhea was markedly reduced. The difference in rectal temperature and the levels of serum OVA-specific IgE, IgG1, IgG2a and IL-4 decreased significantly after prophylactic administration of SD; The number of eosinophils and mast cells in jejunum also decreased significantly while the IL-10 level in the supernatant of BMDCs increased significantly after SD intervention. Conclusion SD mitigates experimental FA response by fosters the immune tolerance property of dendritic cells.
Mice ; Animals ; Ovalbumin ; Interleukin-10 ; Single-Chain Antibodies/genetics* ; Immunoglobulin E ; Epitopes/therapeutic use* ; Interleukin-4 ; Food Hypersensitivity/prevention & control* ; Immunoglobulin G ; Recombinant Fusion Proteins/genetics* ; Mice, Inbred BALB C ; Disease Models, Animal

Antioxidant enzymes fused with cell-penetrating peptides could enter cells and protect cells from irradiation damage. However, the unselective transmembrane ability of cell-penetrating peptide may also bring antioxidant enzymes into tumor cells, thus protecting tumor cells and consequently reducing the efficacy of radiotherapy. There are active matrix metalloproteinase (MMP)-2 or MMP-9 in most tumor cellular microenvironments. Therefore, a fusion protein containing an MMP-2/9 cleavable substrate peptide X, a cell-penetrating peptide R9, a glutathione S-transferase (GST), and a human Cu, Zn superoxide dismutase (SOD1), was designed and named GST-SOD1-X-R9. In the tumor microenvironment, GST-SOD1-X-R9 would lose its cell-penetrating peptide and could not enter tumor cells due to the cleavage of substrate X by active MMP-2/9, thereby achieving selected entering normal cells. The complete nucleotide sequence of SOD1-X-R9 was synthesized and inserted into the prokaryotic expression vector pGEX-4T-1. The pGEX4T-1-SOD1-X-R9 recombinant plasmid was obtained, and soluble expression of the fusion protein was achieved. GST-SOD1-X-R9 was purified by ammonium sulfate precipitation and GST affinity chromatography. The molecular weight of the fusion protein was approximately 47 kDa, consistent with the theoretical value. The SOD and GST activities were 2 954 U/mg and 328 U/mg, respectively. Stability test suggested that almost no change in either SOD activity or GST activity of GST-SOD1-X-R9 was observed under physiological conditions. The fusion protein could be partially digested by collagenase Ⅳ in solution. Subsequently, the effect of MMP-2/9 activity on transmembrane ability of the fusion protein was tested using 2D and 3D cultured HepG2 cells. Little extracellular MMP-2 activity of HepG2 cells was observed under 2D culture condition. While under the 3D culture model, the size and the MMP-2 activity of the HepG2 tumor spheroid increased daily. GST-SOD1-R9 proteins showed the same transmembrane efficiency in 2D cultured HepG2 cells, but the transmembrane efficiency of GST-SOD1-X-R9 in 3D cultured HepG2 spheres was reduced remarkably. This study provided a basis for further investigating the selectively protective effect of GST-SOD1-X-R9 against oxidative damage in normal cells.
Ammonium Sulfate ; Antioxidants ; Cell-Penetrating Peptides/pharmacology* ; Endopeptidases ; Glutathione Transferase/metabolism* ; Humans ; Matrix Metalloproteinase 2/genetics* ; Matrix Metalloproteinase 9/genetics* ; Recombinant Fusion Proteins ; Recombinant Proteins ; Superoxide Dismutase/metabolism* ; Superoxide Dismutase-1

Antimicrobial peptides are the most promising alternatives to antibiotics. However, the strategy of producing antimicrobial peptides by recombinant technology is complicated and expensive, which is not conducive to the large-scale production. Oxysterlin 1 is a novel type of cecropin antimicrobial peptide mainly targeting on Gram-negative bacteria and is of low cytotoxicity. In this study, a simple and cost-effective method was developed to produce Oxysterlin 1 in Escherichia coli. The Oxysterlin 1 gene was cloned into a plasmid containing elastin-like polypeptide (ELP) and protein splicing elements (intein) to construct the recombinant expression plasmid (pET-ELP-I-Oxysterlin 1). The recombinant protein was mainly expressed in soluble form in E. coli, and then the target peptide can be purified with a simple salting out method followed by pH changing. The final yield of Oxysterlin 1 was about 1.2 mg/L, and the subsequent antimicrobial experiment showed the expected antimicrobial activity. This study holds promise for large-scale production of antimicrobial peptides and the in-depth study of its antimicrobial mechanism.
Elastin ; Escherichia coli/genetics* ; Inteins ; Peptides/pharmacology* ; Pore Forming Cytotoxic Proteins ; Recombinant Fusion Proteins/genetics*

The influence of different affinity tags on enzyme characteristics varies. The (S)-carbonyl reductase 2 (SCR2) from Candida parapsilosis can reduce 2-hydroxyacetophenone, which is a valuable prochiral ketones. Different affinity tags, i.e. his-tag, strep-tag and MBP-tag, were attached to the N terminus of SCR2. These tagged SCR2 enzymes, i.e. his6-SCR2, strep-SCR2 and MBP-SCR2, were heterologously expressed in Escherichia coli and purified to study their characteristics towards 2-hydroxyacetophenone reduction. Affinity tags did affect the characteristics of the recombinant SCR2 enzymes. Specifically, affinity tags affect the stability of recombinant SCR2 enzymes: 1) At pH 6.0, the remaining enzyme activities of his6-SCR2 and strep-SCR2 were only 95.2% and 90.0% of the untagged SCR2, while that of MBP-SCR2 was 1.2 times of the untagged SCR2 after incubating for 13 h at 30 °C. 2) The half-life of MBP-SCR2 at 50 °C was 26.6%-48.8% longer than those of strep-SCR2, his6-SCR2 and untagged SCR2. 3) The kcat of MBP-SCR2 was about 1.25-1.45 times of that of small affinity-tagged and untagged SCR2 after storing at -80 °C for 60 d. Structural informatics indicated that the α-helices at the C terminus of MBP-SCR2 contributed to the stability of the N terminus of fusion protein of SCR2. Data from circular dichroism showed that the MBP-tag has some influence on the secondary structure of SCR2, while melting temperature analysis demonstrated that the Tm of the recombinant MBP-SCR2 was about 5 °C higher than that of the untagged SCR2. This study obtained an efficient and stable recombinant SCR2, i.e. the MBP-SCR2. Moreover, this study could serve as a reference for other researchers to evaluate and select appropriate affinity tags for their research.
Alcohol Oxidoreductases ; Escherichia coli/genetics* ; Recombinant Fusion Proteins/genetics*

Tissue inhibitor of metalloproteinases-2 (TIMP-2) inhibits tumor migration and invasion. Obtaining TIMP-2 protein is conducive to a comprehensive and in-depth study of its function and mechanism in tumorigenesis and development. We collected human TIMP-2 protein through prokaryotic expression in vitro. We expressed, purified and characterized human TIMP-2 protein. First, the human TIMP-2 gene was cloned from the cDNA obtained by reverse transcription of total RNA of human lung cancer A549 cells, and constructed to pET28a vector. The recombinant plasmid pET28a-TIMP-2 was transformed into Escherichia coli BL21(DE3) after restriction endonuclease digestion and sequencing analysis. The expression of TIMP-2 protein was induced by isopropyl-β-D-thiogalactoside (IPTG), and the expression conditions were optimized. After purification by nickel affinity column, the fusion protein His-TIMP-2 was identified by Western blotting method and its biological activity was detected by gelatin zymography. The fusion protein His-TIMP-2 existed in the form of inclusion body in E. coli. In a certain range, the concentration of IPTG had no significant effect on the expression amount of His-TIMP-2. But in this expression system, induction temperature and time were the key parameters, and the expression amount of His-TIMP-2 in E. coli increased with the increase of induction temperature. The purified and refolded fusion protein could effectively inhibit the activity of matrix metalloproteinases expressed by human lung cancer A549 cells. The acquisition of active fusion protein lays a foundation for further study of the function and mechanism of human TIMP-2, and is of great significance for tumor therapy.
Cloning, Molecular ; Escherichia coli/genetics* ; Humans ; Recombinant Fusion Proteins/genetics* ; Recombinant Proteins ; Tissue Inhibitor of Metalloproteinase-2/genetics*

In order to prepare human-mouse chimeric cytomegalovirus-immunoglobulin M (CMV-IgM) in vitro and study the effects of different signal peptides on the secretion of CMV-IgM, genes were amplified from hybridoma cell line using RLM-RACE to construct the expression vector of chimeric CMV-IgM. Then, the signal peptide of SigF itself was replaced by five different secreted signal peptides (SigA-SigE) by PCR method, and the CHO cell was chosen as host cell for in vitro expression. SDS-PAGE, SEC-HPLC and ELISA experiments were carried out to evaluate the protein expression level and immunoreactivity of the purified CMV-IgM. A 910 kDa recombinant protein was successfully prepared and signal peptides (SigA-SigE) had an increased expressed CMV-IgM, which were 6.72, 5.19, 1.44, 1.85 and 1.98 times higher than that of the CMV 6# cell signal peptide SigF. In summary, this work provides a theoretical basis for the development of human-mouse chimeric CMV-IgM, and a novel route to increase the expression level of CMV-IgM.
Animals ; Antibodies, Viral ; genetics ; immunology ; Cricetinae ; Cytomegalovirus ; immunology ; Enzyme-Linked Immunosorbent Assay ; Gene Expression ; Humans ; Immunoglobulin M ; immunology ; Mice ; Protein Sorting Signals ; Recombinant Fusion Proteins ; immunology

Drugs targeting immune checkpoint are used for cancer treatment, but resistance to single drug may occur. Combination therapy blocking multiple checkpoints simultaneously can improve clinical outcome. Therefore, we designed a recombinant protein rPC to block multiple targets, which consists of extracellular domains of programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4). The coding sequence was inserted into expression vector and stably transfected into HEK293 cells. The culture supernatant was collected and rPC was affinity-purified. Real-time quantitative PCR was used to evaluate the expression levels of ligands for PD-1 and CTLA-4 in several human cancer cell lines. The binding of rPC with cancer cells was examined by immunofluorescence cell staining, the influence of rPC on cancer cell growth was assayed by CCK-8. The results showed that rPC could be expressed and secreted by stably transfected HEK293 cells, the purified rPC could bind to lung cancer NCI-H226 cells which have high levels of ligands for PD-1 and CTLA-4, no direct impact on cancer cell growth could be observed by rPC treatment. The recombinant protein rPC can be functionally assayed further for developing novel immunotherapeutic drugs for cancer.
Animals ; CTLA-4 Antigen ; genetics ; Cell Proliferation ; HEK293 Cells ; Humans ; Lung Neoplasms ; metabolism ; Programmed Cell Death 1 Receptor ; genetics ; Protein Binding ; Protein Domains ; genetics ; Recombinant Fusion Proteins ; genetics ; isolation & purification ; metabolism

Rv2742 is a novel gene identified from Mycobacterium tuberculosis H37Rv by the proteogenomics strategy. The aim of this study was to establish a system of soluble expression and purification of the missing protein Rv2742 in M. tuberculosis H37Rv, to provide reference for further research on the biological function of Rv2742. The soluble protein was not successfully induced by prokaryotic expression vectors pGEX-4T-2-Rv2742, pET-32a-Rv2742, pET-28a-Rv2742 and pMAL-c2X-Rv2742. After the codon of novel gene Rv2742 was optimized according to E. coli codon usage frequency, only the recombinant strain containing plasmid pMAL-c2X-Rv2742 could produce soluble products of Rv2742 encoding gene. In addition, the expression effects of the desired fusion protein were also analyzed under different conditions including hosts, culture temperatures and IPTG concentrations. The optimum expression conditions were as follows: Rosetta (DE3) host, 16 °C culture temperature and 0.5 mmol/L IPTG. After being purified by affinity chromatography with amylose resin, the fusion protein sequence was confirmed by LC-MS/MS. These results indicated that the novel gene Rv2742 product could be successfully induced and expressed in a soluble form by the expression system pMAL-c2X with MBP tag. Our findings provide reference for studies on potential interaction and immunogenicity.
Chromatography, Liquid ; Cloning, Molecular ; Escherichia coli ; Mycobacterium tuberculosis ; genetics ; Recombinant Fusion Proteins ; Tandem Mass Spectrometry

OBJECTIVE: To develop methods of extraction and purification of Cterminal NUDT9 homology domain of human transient receptor potential melastatin 2 (TRPM2) channel. METHODS: After sonication and centrifuge of strain Rosetta (DE3) which was induced by isopropylthio-β-D-galactoside, GST-NUDT9-H was collected after the binding of supernatant with GST beads and eluted with reduced glutathione. Then the elution buffer containing fusion protein was purified by size exclusion chromatography after concentration and centrifuge. Finally, with the cleavage of thrombin and binding with the GST beads, NUDT9-H with high purity in supernatant was collected. RESULTS: The GST-NUDT9-H fusion protein was stabilized with lysis buffer containing 0.5% n-dodecyl -β-d-maltoside (DDM), and wash buffer containing 0.025% DDM in size-exclusion chromatography system, and finally the NUDT9-H with high purity was obtained after cleaved by thrombin (1 U/2 mg fusion protein) for 24 h. CONCLUSIONS Due to the poor stability of NUDT9-H, it is necessary to add DDM in extraction and purification buffer to stabilize the conformation of NUDT9-H, so as to increase its yields and purity.
Escherichia coli ; genetics ; Glucosides ; chemistry ; Humans ; Protein Domains ; Protein Stability ; Pyrophosphatases ; chemistry ; genetics ; isolation & purification ; Recombinant Fusion Proteins ; chemistry ; isolation & purification ; TRPM Cation Channels ; chemistry ; isolation & purification ; Thrombin ; metabolism