Comparison of two luminescence detection methods for staphylococcal enterotoxin C content in simulated milk samples / 细胞与分子免疫学杂志

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.

Anticuerpos anti-estreptavidina: Confusión diagnóstica por interferencia bioquímica / Anti-estreptavidin antibodies. Diagnostic confusion by biochemical interference

Se presenta el caso de una paciente que, durante los estudios por búsqueda de fertilidad y posterior embarazo, mostraba un perfil tiroideo alterado con niveles elevados de T4 libre y TSH normal. Luego de descartar un adenoma tirotropo y ante la ausencia de sintomatología clínica de hipertiroidismo, se investigó la posibilidad de interferencias analíticas en los inmunoensayos utilizados para la medición de las hormonas. Se han descrito interferencias causadas por anticuerpos heterófilos, macro TSH, anticuerpos anti-tiroideos, biotina, y en menor medida anticuerpos anti-estreptavidina y anti-rutenio. Los análisis de la paciente se realizaron en autoanalizador cuya plataforma emplea el sistema estreptavidina-biotina que es muy susceptible a varios interferentes. Un algoritmo propuesto incluye una serie de pruebas simples de realizar e interpretar que permiten detectar o descartar la presencia de interferentes. De acuerdo al mismo, se efectuó la comparación con una plataforma analítica diferente (que no utiliza el sistema estreptavidina-biotina), diluciones seriadas, precipitación con polietilenglicol 6000 y tratamiento con micropartículas recubiertas con estreptavidina. Los resultados obtenidos confirmaron la presencia de anticuerpos anti-estreptavidina en el suero de la paciente. Ante discordancias entre las manifestaciones clínicas y los resultados de laboratorio, se debe investigar la posibilidad de interferencias metodológicas para evitar el riesgo iatrogénico potencial que implica una interpretación bioquímica errónea.

We present the case of a patient who, during studies for fertility and subsequent pregnancy, showed an altered thyroid profile with elevated levels of free T4 and normal TSH. After ruling out a thyrotropic adenoma and in the absence of clinical symptoms of hyperthyroidism, the possibility of analytical interference in the immunoassays used to measure hormones was investigated. Interferences caused by heterophile antibodies, macro TSH, anti-thyroid antibodies, biotin, and to a lesser extent anti-streptavidin and anti-ruthenium antibodies have been described. The analysis of the patient was carried out in a self-analyzer whose platform uses the streptavidin-biotin system that is very susceptible to several interferents. A proposed algorithm includes a series of simple tests to perform and interpret that allow detecting or ruling out the presence of interferents. Accordingly, a comparison was made with a different analytical platform (which does not use the streptavidin-biotin system), serial dilutions, precipitation with polyethylene glycol 6000 and treatment with microparticles coated with streptavidin. Results obtained confirmed the presence of anti-streptavidin antibodies in the patient's serum. In the case of disagreements between clinical manifestations and laboratory results, the possibility of methodological interferences should be investigated in order to avoid the potential iatrogenic risk involved in an erroneous biochemical interpretation.

A comparative study of osteopontin and MMP-2 protein expression in peripheral and central giant cell granuloma of the jaw / Estudo comparativo da expressão das proteínas osteopontina e MMP-2 no granuloma central e periférico de células gigantes de mandíbula

Abstract Introduction: Oral peripheral and central giant cell granulomas are lesions with little-known etiology and pathogenesis. Objective: The aim of this study was to compare matrix metalloproteinases-2 and osteopontin protein expression in the multinucleated giant cells and mononuclear cells of the peripheral and central giant cell granuloma lesions. Methods: In this retrospective study, the presence of matrix metalloproteinases-2 and osteopontin in 37 cases of central giant cell granuloma and 37 cases of peripheral giant cell granuloma paraffin blocks were assessed by streptavidin-biotin immunohistochemistry. Independent sample t-test, Chi-square, Mann-Whitney tests and Spearman's rank correlation coefficient were used. Results: The osteopontin was expressed in both multinucleated giant cells and mononuclear cells in all cases of peripheral and central giant cells granulomas. However, the matrix metalloproteinases-2 expression was positive in 86.5% of giant cells and it was positive in all of mononuclear cells in peripheral giant cells granuloma. In central giant cells granulomas, 91.8% of giant cells and all mononuclear cells were positive for matrix metalloproteinases-2 marker. Percentage and Intensity of staining were significantly higher in central than peripheral giant cells lesions, for both markers (p ˂ 0.05). Conclusion: This study showed that the expression of osteopontin in giant cells supports the theory of osteolcastic nature of these cells. Also, the presence of osteopontin and matrix metalloproteinases-2 in mononuclear cells may indicate the monocyte-macrophage origin of these cells, as the differentiation of the precursors of the mononuclear stromal monocyte/macrophage to osteoclasts is possibly affected by the expression of osteolytic factors. Also, may be differences in biological behaviors of these lesions are associated with the level of osteopontin and matrix metalloproteinases-2 expression.

Resumo Introdução: Os granulomas periféricos e centrais de células gigantes são lesões com etiologia e patogênese pouco conhecidas. Objetivo: Comparar a expressão das proteínas metaloproteinases da matriz-2 e osteopontina nas células gigantes multinucleadas e células mononucleares no granuloma periférico e central de células gigantes. Método: Neste estudo retrospectivo, a presença de metaloproteinases da matriz-2 e osteopontina em 37 casos de granuloma central de células gigantes e 37 casos de granuloma periférico de células gigantes em blocos de parafina foi avaliada por imuno-histoquímica pela estreptavidina-biotina. Foram usados teste t para amostra independente, teste de qui-quadrado, Mann-Whitney e coeficiente de correlação de Spearman. Resultados: A osteopontina foi expressa em células gigantes multinucleadas e células mononucleares em todos os casos de granuloma periférico de células gigantes e granuloma central de células gigantes. No entanto, a expressão de metaloproteinases da matriz-2 foi positiva em 86,5% de células gigantes e foi positiva em todas as células mononucleares em granuloma periférico de células gigantes. Em granuloma central de células gigantes, 91,8% das células gigantes e todas as células mononucleares foram positivas para o marcador metaloproteinases da matriz-2. A porcentagem e intensidade de coloração em granuloma central de células gigantes foram significantemente maiores do que em granuloma periférico de células gigantes para ambos os marcadores (p ˂ 0,05). Conclusão: Este estudo mostrou que a expressão de osteopontina em células gigantes apoia a teoria da natureza osteoclástica dessas células. Além disso, a presença de osteopontina e metaloproteinases da matriz-2 em células mononucleares pode indicar a origem dos monócitos-macrófagos dessas células, uma vez que a diferenciação dos precursores do monócito/macrófago estromal mononuclear em osteoclastos é possivelmente afetada pela expressão de fatores osteolíticos. Além disso, as diferenças nos comportamentos biológicos dessas lesões estão associadas ao nível de expressão de osteopontina e metaloproteinases da matriz-2.

Enzyme-linked immunosorbent assay for detecting anti-pertussis toxin antibody in mouse

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.

Preparation and bioactivity evaluation of streptavidin-tagged human interferon- inducible T cell alpha chemoattractant bifunctional fusion protein / 南方医科大学学报

<p><b>OBJECTIVE</b>To prepare streptavidin-tagged human interferon-inducible T cell alpha chemoattractant bifunctional fusion proteins (SA/hI-TAC) and evaluate its biological activity.</p><p><b>METHODS</b>pET24a-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.</p><p><b>RESULTS</b>SA-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.</p><p><b>CONCLUSIONS</b>We successfully obtained SA/hI-TAC bifunctional fusion proteins, which may potentially be used in local treatment of tumor and as a tumor vaccine.</p>

Single-molecule detection and characterization of DNA replication based on DNA origami / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate single-molecule detection and characterization of DNA replication.</p><p><b>METHODS</b>Single-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.</p><p><b>RESULTS</b>The 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.</p><p><b>CONCLUSIONS</b>The 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.</p>

Development of a method for the separation of HLA-A, -B and -C haploid using biotinylated probe and streptavidin magnetic beads / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To 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.</p><p><b>METHODS</b>Based 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.</p><p><b>RESULTS</b>Among 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.</p><p><b>CONCLUSION</b>The developed method for HLA-A, -B and -C haploid separation is reliable, which can solve certain ambiguity and improve the accuracy of HLA genotyping.</p>

Intravesical anchoring of streptavidin-tagged interleukin-4 fusion protein for immunotherapy of mouse superficial bladder cancer / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To 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.</p><p><b>METHODS</b>IL-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.</p><p><b>RESULTS</b>The 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.</p><p><b>CONCLUSION</b>Intravesical 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.</p>

Generation of streptavidin-tagged human-granulocyte macrophage colony-stimulating factor fusion proteins / 南方医科大学学报

<p><b>OBJECTIVE</b>To obtain streptavidin-tagged human granulocyte-macrophage colony-stimulating factor (SA/hGM-CSF) fusion protein and evaluate its bioactivity .</p><p><b>METHODS</b>PET24a-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.</p><p><b>RESULTS</b>The 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%).</p><p><b>CONCLUSION</b>SA/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.</p>

Immunolocalization of HB-EGF in human skin by streptavidin-peroxidase (HRP) conjugate method / Inmunolocalización de HB-EGF en piel humana por el método de conjugado estreptavidina-peroxidasa (HRP)

EGF family growth factors consists of growth factors, such as transforming growth factor (TGF)-a, heparin-binding EGF-like growth factor (HB-EGF), amphiregulin (AR) and epiregulin, autocrine growth factors in normal human keratinocytes. HB-EGF is mitogen for epithelial cells and like other members of the EGF family, HB-EGF exerts its biological effects via interaction with the EGF receptor (EGFR). HB-EGF is an autocrine growth factor for human keratinocytes, and has a possible role as a paracrine growth factor for fibroblast. Our report concerning immunohistochemical localization of HB-EGF in normal skin by using the streptavidin-peroxidase (HRP) conjugate method, confirms previous data, revealing specific patterns of HB-EGF localization. Identification of HB-EGF in cells of epithelial origin suggests its autocrine and/or paracrine roles in epithelial cell maintenance. Our report especially wants to give a technical contribution, easy to manage and with evident results. A simple technique that does not require use of sophisticated equipment.

La familia factores de crecimiento EGF se compone de representantes como el factor de crecimiento transformante (TGF)-a, factor epidérmico vinculante a la heparina (HB-EGF), anfiregulina (AR) y epirregulina, factores autocrinos de crecimiento en queratinocitos humanos normales. HB-EGF es mitógeno para células epiteliales y al igual que otros miembros de la familia EGF, HB-EGF ejerce sus efectos biológicos a través de la interacción con el receptor de EGF (EGFR). HB-EGF es un factor de crecimiento autocrino de queratinocitos humanos, y tiene un posible papel como factor de crecimiento paracrino de los fibroblastos. Nuestro reporte sobre la localización inmunohistoquímica de HB-EGF en la piel normal mediante el método de conjugado estreptavidina-peroxidasa (HRP), confirma datos anteriores, revelando patrones de localización específicos para HB-EGF. La identificación de HB-EGF en las células de origen epitelial sugiere su papel autocrino y/o paracrinos en el mantenimiento de las células epiteliales. Nuestro informe quiere dar una contribución técnica, fácil de manejar y con resultados evidentes. Una técnica simple que no requiera el uso de equipo sofisticado.

Radiolabeled nano-peptides show specificity for an animal model of human PC3 prostate cancer cells

OBJECTIVES: Cancer has been investigated using various pre-targeting techniques or models focusing on radiobombesin analogues; however, both are not offered together. In this study, nano-bombesin labeling by a pre-targeting system was undertaken to develop an alternative approach for prostate tumor treatment. METHODS: A two-step pre-targeting system utilizing a combination of streptavidin (SA), biotinylated morpholino (B-MORF), biotinylated BBN (B-BBN) with two different spacers (b-Ala and PEG), and a radiolabeled cMORF was evaluated in vitro and in vivo. RESULTS: Final conjugation conditions consisted of a 1:1:2 ratio of SA:B-MORF:B-BBN, followed by addition of 99mTc-cMORF to compensate for free MORF. In vitro binding experiments with prostate cancer cells (PC-3) revealed that total binding was time-dependent for the Ala spacer but not for the PEG spacer. The highest accumulation (5.06 ± 1.98 percent) was achieved with 1 hour of incubation, decreasing as time progressed. Specific binding fell to 1.05 ± 0.35 percent. The pre-targeting biodistribution in healthy Swiss mice was measured at different time points, with the best responses observed for 7-h and 15-h incubations. The effector, 99mTc-MAG3-cMORF, was administered 2 h later. Strong kidney excretion was always documented. The greatest tumor uptake was 2.58 ± 0.59 percentID/g at 7 h for B-bAla-BBN, with a region of interest (ROI) value of 3.9 percent during imaging. The tumor/blood ratio was low due to the slow blood clearance; however, the tumor/muscle ratio was 5.95. CONCLUSIONS: The pre-targeting approach with a peptide was a viable concept. Further evaluation with modified sequences of MORF, including less cytosine, and additional test intervals could be worthwhile.

Preparation and application of a novel HCV diagnostic antigen fused to streptavidin / 中华实验和临床病毒学杂志

<p><b>OBJECTIVE</b>To prepare streptavidin-tagged hepatitis C virus (HCV) fusion protein and explore its application for the detection of antibody against HCV infection.</p><p><b>METHODS</b>A recombinant plasmid pET-11d-C44P-SA was constructed, which coding a novel HCV diagnostic antigens (C44P) and streptavidin (SA) fusion protein, and the fusion protein was generated with BL21 (DE3) E Coli and identified by Western Blot analysis. Then the fusion protein was purified through the Ni-NTA affinity chromatography and over 90% purity has been achieved. Anti-HCV ELISAs were developed when the fusion protein was used in the biotin-pre-coated microplate or ordinary microplate, and then the sensitivity and specificity of the ELISA were evaluated with confirmed human sera panels.</p><p><b>RESULTS</b>The fusion protein was expressed in high yields and purified successfully, the ELISA detection of anti-HCV with human sera panel indicated that its sensitivity and specificity is higher when SA-tagged HCV antigen (C44P-SA) coated in biotin-pre-coated microplate, compared to C44P or C44P-SA coated in ordinary microplate.</p><p><b>CONCLUSION</b>The sensitivity and specificity of anti-HCV ELISA can be improved when a novel HCV diagnostic antigen fused to SA combined with the biotin- pre-coated microplate. This study laid a foundation for improving the performance of HCV diagnostics.</p>

A novel immunotherapy for superficial bladder cancer by the immobilization of streptavidin-tagged bioactive IL-2 on the biotinylated mucosal surface of the bladder wall / 癌症

<p><b>BACKGROUND AND OBJECTIVE</b>Intravesical 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.</p><p><b>METHODS</b>A 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.</p><p><b>RESULTS</b>SA-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.</p><p><b>CONCLUSIONS</b>SA-hIL-2 fusion protein could significantly inhibit tumor growth and extend the survival time in the orthotopic model of MB49 bladder cancer.</p>

Immobilization of streptavidin-tagged bioactive hTNF-alpha on biotinylated mucosal surface of the bladder wall for treatment of superficial bladder cancer in mice / 南方医科大学学报

<p><b>OBJECTIVE</b>To 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.</p><p><b>METHODS</b>A 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.</p><p><b>RESULTS</b>SA-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).</p><p><b>CONCLUSION</b>SA-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.</p>

Expression, purification and bioactivity evaluation of streptavidin-tagged human interleukin-21 fusion protein / 南方医科大学学报

<p><b>OBJECTIVE</b>To obtain streptavidin-tagged human interleukin-21 (hIL21) fusion protein and evaluate its bioactivities.</p><p><b>METHODS</b>hIL21-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.</p><p><b>RESULTS</b>The 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%).</p><p><b>CONCLUSION</b>We 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.</p>

Preparation and bioactivity evaluation of streptavidin-tagged human interleukin-15 fusion protein / 南方医科大学学报

<p><b>OBJECTIVE</b>To obtain streptavidin-tagged human interleukin-15 (SA/hIL15) fusion protein and evaluate its bioactivity.</p><p><b>METHODS</b>pET24a-6His-SA-hIL-15 and pET32a-hIL-15-SA-6His plasmids were constructed and expressed in BL 21(DE3) host bacteria to generate the fusion protein. The recombinant fusion protein IL-15/SA was purified using Ni-NTA affinity chromatography and refolded, and the efficiency of surface modification of the fusion protein on biotinylated cells was examined by fluorescence-activated cell sorting. CCK-8 method was used to evaluate the effect of IL-15/SA fusion protein in inducing the proliferation of human peripheral-blood lymphocyte (PBL) cells stimulated by PHA.</p><p><b>RESULTS</b>The recombinant SA-hIL-15 and hIL15-SA fusion proteins were highly expressed in BL21(DE3) at about 20% of the total bacterial proteins. The purified hIL15-SA fusion protein exhibited a bifunctionality by promoting the proliferation of PBL cells activated by PHA and high-affinity binding to biotinylated cell surface mediated by SA, with a cell surface modification efficiency exceeding 95%. SA-hIL-15 showed a 4-fold higher hIL15 bioactivity than hIL15-SA.</p><p><b>CONCLUSION</b>SA/hIL-15 bifunctional fusion protein has been successfully obtained to facilitate the future development of hIL-15-surface-modified cancer cell vaccine.</p>

Expression, purification and refolding of streptavidin-tagged human tumor necrosis factor-alpha fusion protein / 南方医科大学学报

<p><b>OBJECTIVE</b>To study the purification, refolding and bioactivity of streptavidin-tagged human tumor necrosis factor-alpha (SA-TNF-alpha) bi-functional fusion protein.</p><p><b>METHODS</b>SA-TNF-alpha fusion protein was expressed in BL21(DE3) host bacteria, purified using Ni-NTA affinity chromatography and refolded by dilution and dialysis followed by identification using Western blotting. The effect of SA-TNF-alpha fusion protein against L929 cells was evaluated by MTT assay. Flow cytometry was used to analyze the surface modification of biotinylated MB49 tumor cells by SA-TNF-alpha fusion protein.</p><p><b>RESULTS</b>Recombinant SA- TNF-alpha fusion protein was expressed in BL21(DE3) at about 30% of total bacterial protein, with a purity of about 95% after purification. The SA-TNF-alpha fusion protein existed as dimmers, tetramers and higher order structures after refolding. The fusion protein exhibited a bi-functionality by inhibiting L929 cells and SA-mediated high-affinity binding to biotinylated cell surfaces, with an anchor modification rate of above 90%.</p><p><b>CONCLUSION</b>The dimmers, tetramers and higher order structures of the obtained SA-TNF-alpha fusion protein all exhibit a bi-functionality, and may serve as a potential candidate therapeutic agent for tumors.</p>

Expression and characterization of fusion protein tTF/SA as a universal effector for targeting blood coagulation / 生物工程学报

<p><b>UNLABELLED</b>To prepare a novel fusion protein (tTF/SA) as a universal effector for targeting therapy of blood coagulation and to analyze its biological activities. The fusion gene tTF/SA was constructed by PCR, then inserted into expression vector pET22 b (+), and expressed in E. coli BL21 (DE3). The fusion protein was purified using Nickel-affinity chromatography column. The activities of tTF moiety of the fusion protein were analyzed by clotting assay and FX activation assay, and the binding activities of Streptavidin(SA) to Biotin(B) were analyzed using ELISA.</p><p><b>RESULTS</b>The recombinant plasmid tTF/SA/pET22 b (+) with the correct sequence was obtained. The fusion gene tTF/SA was expressed with high yield in E. coli BL21 (DE3). The purified fusion protein retain the abilities of activating FX, inducing blood coagulation, and binding Biotin. The fusion gene tTF/SA was successfully expressed in E. coli BL21 (DE3). The recombinant tTF/SA proteins retain the activities of TF and SA. The multitarget therapy of selectively inducing thrombosis in tumor blood vessels can be achieved by the combination of tTF/SA, as a universal effector, and biotinlated carriers directing to tumor blood vessels.</p>

Targeted magnetic resonance imaging with intraperitoneal and intravenous streptavidin (SA)-DTPA-Gd: a comparative study in tumor-bearing nude mice / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of streptavidin (SA)-DTPA-Gd after intraperitoneal and intravenous administration for tumor enhancement in targeted magnetic resonance imaging (MRI).</p><p><b>METHODS</b>Biotinylated monoclonal antibody CL3 (600 microg) was intravenously injected into 12 BALB/c nude mice with subcutaneous inoculation of LoVo cells, followed by administration of 80 microg avidin as the chaser 24 h later and then SA-DTPA-Gd was injected intravenously or intraperitoneally after another 30 min. MRI was performed before and 20, 60 min and 3, 6, 9, 12 h after the injection of the contrast agents, and the MR signal intensity of the tumor and liver was determined.</p><p><b>RESULT</b>The maximum enhancement ratio of the tumor was 70.2% in the intravenous injection group and 46.4% in the intraperitoneal group, showing significant difference between them. The maximal enhancement rate of the liver was 23.7% in the intraperitoneal group and 20.4% in the intravenous group, showing no significant difference.</p><p><b>CONCLUSION</b>MR targeted imaging with biotinylated monoclonal antibody CL3 and SA-DTPA-Gd has specific enhancement effect. Higher blood level of SA-DTPA-Gd in the intravenous group facilitates the tumor enhancement in MRI in subcutaneous tumor model.</p>

Development of an Immuno-PCR Protocol for Detection of a Small Amount of Antigen / 대한진단검사의학회지

BACKGROUND: Immuno-PCR has been known as a highly sensitive and specific method, yet no standardized protocol is available. We analyzed each step of immuno-PCR to develop a reliable standardized method. METHODS: We made a protocol modified from several methods reported previously, and performed immuno-PCR, but false positive reactions were noted. To reduce the false positivity, we investigated the buffer reagents and biotin-labelled oligo-nucleotide probe. Using a finally determined protocol, we compared the detection-limits of the immuno-PCR and ELISA methods. RESULTS: Streptavidin was identified as a main reagent causing a non-specific binding, thus it was replaced by neutravidin. The employment of CAS block as a dilution buffer for the biotin-labelled oligo-nucleotide probe and Casein block as a buffer for the detection antibodies resulted in a dramatic reduction in the false positive reactions. The standardized immuno-PCR detected angiogenin antigen at a concentration as low as 5 fg/mL, while an ELISA method detected 5 pg/mL. CONCLUSIONS: The immuno-PCR procedure newly described in this study was ultra-sensitive with no false positivity. This method can be utilized as an epochal tool for detection of a small amount of antigen which would not be discovered by ELISA method.