Objective To compare the sensitivity and accuracy of amplified luminescent proximity homogeneous assay linked immunosorbent assay (AlphaLISA) and magnetic particles-based chemiluminescence immunoassay (MP-CLIA) for detection of staphylococcal enterotoxin C (SEC) in the simulated milk samples. Methods The AlphaLISA was constructed using goat anti-SEC polyclonal antibody-coupled receptor microspheres, biotin-labeled SEC monoclonal antibody and streptavidin-coupled donor microspheres. The MP-CLIA was constructed using goat anti-SEC polyclonal antibody conjugated alkaline phosphatase, biotin-labeled anti-SEC monoclonal antibody and streptavidin conjugated magnetic beads. Results The sensitivity of AlphaLISA to detect SEC content in simulated milk samples was 4.04 ng/L, and the coefficient of variation (CV) was 1.98%~9.82%. The sensitivity of MP-CLIA was 108.19 ng/L and CV was 4.63%~20.40%. Conclusion Compared with MP-CLIA, AlphaLISA is more sensitive and accurate to detecting SEC.
Animals ; Streptavidin ; Biotin ; Luminescence ; Milk ; Antibodies, Monoclonal ; Goats ; Immunoassay/methods*

PURPOSE: Although the DTaP and Tdap vaccines used to prevent pertussis have been used for a long time, there is no standard method for measuring pertussis antigens. Therefore, this preliminary study was conducted to develop an enzyme-linked immunosorbent assay method using an animal model for measuring antibodies against pertussis toxin, the most important pertussis pathogenic antigen, in the sera of vaccinated mice. MATERIALS AND METHODS: Bordetella pertussis Tohama phase I was cultured for 24–30 hours, and then pertussis toxin was purified from the culture medium by chromatography. Purified pertussis toxin was diluted in phosphate-buffered saline-coating buffer, and 100 µL of diluted pertussis toxin was added to each well and reacted at room temperature for 4 hours. Positive serum was diluted to 1/1,250–1/80,000 and negative serum was diluted to 1/50 to determine the coating concentration with the optimal signal/noise ratio. Optimal test conditions were confirmed from the dilution factors of the secondary antibody and streptavidin horseradish peroxidase (SA-HRP). RESULTS: Optimal conditions were as follows: 4 µg/mL for coating antigen; 1/40,000 for secondary antibody; and 1/1,000 for the SA-HRP dilution factor. Comparison of the sera obtained from mice treated with a developing vaccine and commercial vaccine with National Institute for Biological Standard and Control standard serum under the established conditions showed the following results: 1,300.62, 534.94, and 34.85, respectively. CONCLUSION: The method developed in this study is suitable for measuring anti-pertussis toxin antibodies and may be applicable for clinical sample analysis or indirect diagnosis of pertussis.
Animals ; Antibodies ; Bordetella pertussis ; Chromatography ; Diagnosis ; Enzyme-Linked Immunosorbent Assay* ; Horseradish Peroxidase ; Methods ; Mice* ; Models, Animal ; Pertussis Toxin ; Streptavidin ; Vaccines ; Whooping Cough

OBJECTIVETo prepare streptavidin-tagged human interferon-inducible T cell alpha chemoattractant bifunctional fusion proteins (SA/hI-TAC) and evaluate its biological activity.

METHODSpET24a-SA-hI-TAC/pET21a-hI-TAC-SA plasmids were constructed and expressed in BL21. SA-hI-TAC and hI-TAC-SA fusion proteins were purified by Ni-NTA affinity chromatography, refolded by dialysis and identified by Western blotting. The bifunctionality of the fusion proteins (biotin-binding function and hI-TAC activity) was analyzed by flow cytometry and lymphocyte chemotaxis experiment, respectively.

RESULTSSA-hI-TAC/hI-TAC-SA fusion proteins were expressed at about 12% and 25% of the total bacterial protein, respectively. The two fusion proteins had a purity of about 85% and 90% after purification, and their purity reached 98% after purification with S-100 gel filtration chromatography. Both of the fusion proteins were efficiently immobilized on the surface of biotinylated mouse bladder cancer MB49 cells (91.3% for SA-hI-TAC and 98.8% for hI-TAC-SA). SA/hI-TAC induced lymphocyte chemotaxis in a dose-dependent manner, and hI-TAC-SA showed a stronger chemotactic effect than SA-hI-TAC.

CONCLUSIONSWe successfully obtained SA/hI-TAC bifunctional fusion proteins, which may potentially be used in local treatment of tumor and as a tumor vaccine.

Animals ; Biotinylation ; Blotting, Western ; Cancer Vaccines ; Cell Line, Tumor ; Chemokine CXCL11 ; chemistry ; Chromatography, Affinity ; Humans ; Interferons ; chemistry ; Mice ; Plasmids ; Recombinant Fusion Proteins ; biosynthesis ; chemistry ; Streptavidin

OBJECTIVETo develop a method for separating the human leukocyte antigen (HLA)-A, -B and -C haploid using biotinylated probes and streptavidin magnetic beads in order to solve ambiguous HLA genotyping results.

METHODSBased on sequence information of HLA alleles from the IMGT/HLA database, the 5-biotinylated probes were designed. The probe was mixed and extended with corresponding genomic DNA, and incubated with streptavidin magnetic beads, which could form a streptavidin magnetic beads-biotin-probe DNA complex. The unique DNA haploid binding to corresponding probe was isolated after washes and elution. The separated haploid genomic DNA was used as template for HLA-A, -B and -C loci amplification and sequencing analysis.

RESULTSAmong the 12 HLA-A probes, 19 HLA-B probes and 13 HLA-C probes, DNA sequencing has confirmed that 9 HLA-A probes, 9 HLA-B probes and 5 HLA-C probes could successfully separate the haploid from genomic DNA samples.

CONCLUSIONThe developed method for HLA-A, -B and -C haploid separation is reliable, which can solve certain ambiguity and improve the accuracy of HLA genotyping.

Genotype ; HLA-A Antigens ; genetics ; HLA-B Antigens ; genetics ; HLA-C Antigens ; genetics ; Haploidy ; Humans ; Molecular Probe Techniques ; instrumentation ; Polymerase Chain Reaction ; instrumentation ; methods ; Streptavidin ; chemistry

OBJECTIVETo investigate single-molecule detection and characterization of DNA replication.

METHODSSingle-stranded DNA (ssDNA) as the template of DNA replication was attached to DNA origami by a hybridization reaction based on the complementary base-pairing principle. DNA replication catalyzed by E.coli DNA polymerase I Klenow Fragment (KF) was detected using atomic force microscopy (AFM). The height variations between the ssDNA and the double-stranded DNA (dsDNA), the distribution of KF during DNA replication and biotin-streptavidin (BA) complexes on the DNA strand after replication were detected. Agarose gel electrophoresis was employed to analyze the changes in the DNA after replication.

RESULTSThe designed ssDNA could be anchored on the target positions of over 50% of the DNA origami. The KF was capable of binding to the ssDNA fixed on DNA origami and performing its catalytic activities, and was finally dissociated from the DNA after replication. The height of DNA strand increased by about 0.7 nm after replication. The addition of streptavidin also resulted in an DNA height increase to about 4.9 nm due to the formation of BA complexes on the biotinylated dsDNA. The resulting dsDNA and BA complex were subsequently confirmed by agarose gel electrophoresis.

CONCLUSIONSThe combination of AFM and DNA origami allows detection and characterization of DNA replication at the single molecule level, and this approach provides better insights into the mechanism of DNA polymerase and the factors affecting DNA replication.

Biotinylation ; DNA ; chemistry ; DNA Replication ; DNA, Single-Stranded ; chemistry ; DNA-Directed DNA Polymerase ; Electrophoresis, Agar Gel ; Microscopy, Atomic Force ; Nucleic Acid Hybridization ; Streptavidin

OBJECTIVETo evaluate the antitumor efficacy of streptavidin-tagged interleukin-4 (IL-4-SA) bifunctional fusion protein in the immunotherapy of mouse model of superficial bladder cancer.

METHODSIL-4-SA fusion protein was prepared and its biological activity was determined. One day after MB49 cell implantation, 100 µl of 1 mg/ml NHS-PEO4-biotin was instilled into the bladder for 30 minutes, followed by intravesical instillation of 100 µl PBS, GFP-SA+IL-4 or IL-4-SA and incubation for 1 hour. The bladder irrigation was performed twice a week for three weeks. The CTL cytotoxicity and profile of CD8(+) tumor-infiltrating lymphocytes were analyzed.

RESULTSThe IL-4-SA fusion protein was durably anchored to the biotinylated mucosal surface of bladder wall for up to 5 days.On day 80 after the implantation of MB49 cells, all of PBS-treated mice died, and 8 out of 10 mice in the GFP-SA-treated group died from tumor burden.In contrast, 5 out of 10 mice in the IL-4-SA-treated group were tumor-free. The MB49 tumor-specific cytotoxicity from mice in the IL-4-SA group was (11.3 ± 1.2)%, (22.7 ± 1.5)% and (31.0 ± 3.0)% at the effector to target ratios of 1:1, 25:1 and 50:1, respectively. But the corresponding cytotoxicity was (4.3 ± 0.6)%, (9.0 ± 1.0)% and (14.3 ± 1.5)% in the GFP-SA+IL-4 group, and (3.3 ± 0.6)%, (7.3 ± 0.6)%, (12.7 ± 2.1)% in the PBS group. The tumor-specific cytotoxicity in the SA-CD40L group was significantly higher than that in the control groups (P < 0.05). The infiltrating CD8(+) T cells in tumors in the IL-4-SA-treated group were increased compare with those in other groups.

CONCLUSIONIntravesical anchoring of IL-4-SA elicites strong and long-lasting immunoprotection against superficial bladder cancer, and the novel immunotherapy may be an attractive therapeutic alternative in future.

Administration, Intravesical ; Animals ; Biotinylation ; CD8-Positive T-Lymphocytes ; pathology ; Cell Line, Tumor ; Humans ; Immunotherapy ; methods ; Interleukin-4 ; metabolism ; therapeutic use ; Male ; Mice ; Mice, Inbred C57BL ; Neoplasm Transplantation ; Recombinant Fusion Proteins ; metabolism ; therapeutic use ; Streptavidin ; metabolism ; therapeutic use ; Urinary Bladder Neoplasms ; metabolism ; therapy

OBJECTIVETo obtain streptavidin-tagged human granulocyte-macrophage colony-stimulating factor (SA/hGM-CSF) fusion protein and evaluate its bioactivity .

METHODSPET24a-6His-SA-L-hGM-CSF and PET24a-hGM-CSF-L-SA-6His plasmids were constructed and expressed in Rosetta (DE3) host bacteria to generate the fusion proteins. The two fusion proteins were refolded by gradient dialysis after Ni-NTA affinity chromatography and finally purified using DEAE-sepharose FF anion exchange chromatography. MTT method was used to evaluate the effect of SA/hGM-CSF fusion proteins in inducing the proliferation of human erythroleukemia cells (TF-1). The efficiency of the fusion proteins for surface modification of biotinylated MB49 tumor cells was evaluated by flow cytometry.

RESULTSThe recombinant fusion proteins SA-hGM-CSF and hGM-CSF-SA were highly expressed in Rosetta (DE3) at about 20% of the total bacterial proteins, with a purity of about 96% after purification. The two fusion proteins exhibited bifunctional activities, namely the pro-proliferation effect on human erythroleukemia cells (TF-1) and SA-mediated high-affinity binding to biotinylated cell surfaces (with an anchoring modified rate of about 99%).

CONCLUSIONSA/hGM-CSF bi-fusion proteins obtained in this study lays the groundwork for the development of cancer cell vaccines with surface modification by hGM-CSF.

Biomarkers ; Cancer Vaccines ; biosynthesis ; Cell Line, Tumor ; Diterpenes ; pharmacology ; Escherichia coli ; metabolism ; Granulocyte-Macrophage Colony-Stimulating Factor ; biosynthesis ; Humans ; Membrane Fusion Proteins ; biosynthesis ; Plasmids ; Streptavidin ; chemistry

BACKGROUND AND OBJECTIVEIntravesical administration of Bacillus Calmette-Guerin (BCG) after transurethral resection is by far the most effective local therapy for superficial bladder cancer, the fifth most common cancer in the world. However, approximately one-third of patients fail to respond and most patients eventually relapse. In addition, there are pronounced side effects of BCG therapy, such as BCG sepsis and a high frequency of BCG-induced cystitis. This study established a novel immunotherapy through immobilization of streptavidin-tagged human IL-2 (SA-hIL-2) on the biotinylated mucosal surface of bladder wall.

METHODSA mouse orthotopic model of MB49 bladder cancer was established by perfusing MB49 cells into mouse bladders. The SA-hIL-2 fusion protein was immobilized on the biotinylated mucosal surface of the bladder wall. Treatment began on day 1 after MB49 implantation, once every 3 days for 6 times. Immunohistochemical assay was performed to assess the persistence of SA-hIL-2 immobilized on the biotinylated mucosal surface of the bladder wall. The mice were monitored for tumor growth and survival. On day 60 after MB49 implantation, the SA-hIL-2-cured mice, which were found to have no hematuria or palpable tumors, were challenged with wild-type MB49 cells implanted into the pretreated bladder and monitored for survival.

RESULTSSA-hIL-2 could be immobilized efficiently and durably on the bladder mucosal surface as long as 7 days. On day 60 after MB49 implantation, 9 out of 20 SA-hIL-2-treated mice survived, but all mice in PBS control group died. More importantly, 5 out of 9 tumor-free mice in the SA-hIL-2 group were protected against a second intravesical wild-type MB49 tumor challenge.

CONCLUSIONSSA-hIL-2 fusion protein could significantly inhibit tumor growth and extend the survival time in the orthotopic model of MB49 bladder cancer.

Animals ; Biotinylation ; Cell Line, Tumor ; Female ; Immobilized Proteins ; metabolism ; therapeutic use ; Immunotherapy ; methods ; Interleukin-2 ; metabolism ; therapeutic use ; Mice ; Mice, Inbred C57BL ; Mucous Membrane ; metabolism ; Neoplasm Transplantation ; Receptors, Interleukin-2 ; metabolism ; Recombinant Fusion Proteins ; metabolism ; therapeutic use ; Streptavidin ; metabolism ; therapeutic use ; Urinary Bladder ; pathology ; Urinary Bladder Neoplasms ; immunology ; therapy

OBJECTIVETo obtain streptavidin-tagged human interleukin-21 (hIL21) fusion protein and evaluate its bioactivities.

METHODShIL21-SA-pET21 and pET24a-SA- hIL21 plasmids were constructed and expressed in BL21(DE3) host bacteria. The hIL21-SA and SA- hIL21 fusion protein were purified through Ni-NTA affinity chromatography and refolded by dialysis. Flow cytometry was used to detect hIL21-SA and SA- hIL21 fusion protein on the biotinylated MB49 tumor cells. MTT assay was used to evaluate the effect of the fusion protein on the proliferation of human peripheral blood lymphocytes (PBLs) stimulated by Anti-CD3.

RESULTSThe recombinant fusion proteins were highly expressed in BL21(DE3) at about 30% of the total bacterial proteins. The two fusion proteins exhibited bifunctional activities, i.e. both biotin-binding property and hIL21 activity and SA-mediated high-affinity binding to biotinylated cell surfaces (with anchoring modified rate of about 95.18% and 96.91%).

CONCLUSIONWe have successfully obtained bifunctional fusion protein hIL21-SA and SA- hIL21,which will provide a basis for further study of tumor biotherapy using the proteins.

Cancer Vaccines ; immunology ; Cell Line, Tumor ; Escherichia coli ; genetics ; metabolism ; Humans ; Interleukins ; biosynthesis ; genetics ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; immunology ; Streptavidin ; biosynthesis ; genetics

OBJECTIVETo investigate a novel immunotherapy through immobilization of streptavidin-tagged hTNF-alpha on the biotinylated mucosal surface of the bladder wall for bladder cancer treatment in mice.

METHODSA total of 120 female C57BL/6j mice were randomized into 5 equal groups, namely blank control, PBS, soluble hTNF-alpha, SA-GFP, and SA-hTNF-alpha treatment groups. Twenty-four hours after establishment of a mouse model of orthotopic superficial bladder cancer, SA-hTNF-alpha fusion protein was immobilized on the biotinylated mucosal surface of the bladder wall, which was repeated every 4 days for a total of 6 sessions. Immunohistochemistry was performed to detect the retention time of SA-hTNF-alpha fusion protein in the biotinylated mouse bladder mucosa and the distribution of CD4(+) and CD8(+) lymphocytes in the mucosa and tumor tissues, with the tumor growth and mouse survival also observed. The cytotoxiciy of the tumor-specific lymphocytes was evaluated. The mice responding well to the treatment were re-challenged by MB49 and monitored for survival.

RESULTSSA-hTNF-alpha could be efficiently and stably immobilized on the bladder mucosal surface for as long as 7 days. On day 60 after MB49 implantation, 18 out of 22 SA- hTNF-alpha-treated mice survived, with 9 appearing tumor-free, but all the mice in PBS control group died. Five out of 9 tumor-free mice in SA-hTNF-alpha group showed resistance to a re-challenge with intravesical MB49. The numbers of CD4(+) and CD8(+) lymphocytes were significantly greater in SA-hTNF-alpha group than in the other groups (P<0.05). The cytotoxicity of the tumor-specific lymphocytes was significantly stronger in SA-hTNF-alpha group than in the other groups (P<0.05).

CONCLUSIONSA-hTNF-alpha immobilized on the biotinylated mucosal surface of the bladder wall can significantly inhibit the tumor growth and promote the survival of the mice bearing orthotopic superficial bladder cancer.

Administration, Intravesical ; Animals ; Biotinylation ; Carcinoma, Transitional Cell ; immunology ; therapy ; Female ; Immobilized Proteins ; therapeutic use ; Immunotherapy ; methods ; Mice ; Mice, Inbred C57BL ; Recombinant Fusion Proteins ; metabolism ; therapeutic use ; Streptavidin ; metabolism ; therapeutic use ; Tumor Necrosis Factor-alpha ; metabolism ; therapeutic use ; Urinary Bladder Neoplasms ; immunology ; therapy