Expression, purification and characterization of recombinant toxins consisting of truncated gastrin 17 and pseudomonas exotoxin

Gastric cancer is a major cause of mortality and morbidity around world. However the effectiveness of the current approaches to the diagnosis and treatment of gastric cancer is limited. Recombinant targeted toxins may represent a novel direction of cancer therapy. In this study, we aimed to explore whether recombinant toxins fused with the truncated forms of G17 could target to kill cancer cells by recognizing CCK2R. Four recombinant Pseudomonas toxins PE38 fused with the forward or reverse truncated forms of G17 (G14 and G13) were successfully constructed, expressed, and purified. Their characteristics were further analyzed by SDS-PAGE, western blot and indirect immunofluorescence assay. The cytotoxicity assay demonstrated that only reversely fused recombinant toxins rG14PE38 and rG13PE38 exhibited certain toxicity on several cancer cell lines, and a competition assay indicated that the binding of the reverse gastrin-endotoxin to CCK2R (+) cells may be mediated by interaction between gastrin/gastrin-like and CCK2R.

Reducing dioxin formation by adding hydrogen in simulated fly ash

In this study, simulated fly ash containing CuO/CuCl2 was heated at 350 °C in a flow of N2 and also in a nitrogen flow containing 10 vol% H2, to evaluate the influence of hydrogen adding on dioxin formation. The total polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) output derived from the CuO sample under N2 and 10 % H2 was 7.382 and 0.708 ng/g, respectively. As for CuCl2, it was 589 and 46.1 ng/g, respectively. The results show that the hydrogen adding has a good inhibition effect on PCDD/F formation; the inhibition rate was higher than 90 % for PCDD/Fs. HCl and NH3 were detected by Gasmet in the flue gas; the probable inhibition mechanism of hydrogen reaction was proposed, based on our measurements and others' researches.

Contamination of commercially available seafood by key diarrhetic shellfish poisons along the coast of China

With the increasing number of outbreaks of food-borne diseases caused by okadaic acid (OA) and its analogue dinophysistoxin-1 (DTX-1), two key diarrhetic shellfish poison (DSP) toxins, OA and DTX-1, have become a serious threat to public health and have attracted significant public attention in China. The aim of our study was to monitor OA and DTX-1 contamination in commercially available seafood and to provide references for tracking these toxins and preventing disease outbreaks. From 2010 to 2012, 40 species were collected from six coastal cities of four inland seas in China. An enzyme-linked immunosorbent assay (ELISA) and a lateral flow immunochromatographic (LFIC) test strip were used to analyse the samples, and the results were further confirmed using a commercially available ELISA kit. The monitoring results indicated that 23 of 40 species were positive for contamination. In addition, 14 of the positive species were determined to be inedible because the content of OA and DTX-1 was above the regulatory limit. Simultaneously, we verified that the digestive glands of shellfish tended to accumulate toxin, in contrast to the flesh. The highest concentrations of OA and DTX-1 were recorded in Scapharca broughtonii, which was collected from Qing Dao, in relation to the other analysed species. Moreover, the Arca family as well as Mytilus galloprovincialis were severely contaminated by OA and its analogue. The above results indicate that some of the commercially available seafood from the coastal cities in China may be inedible due to serious marine toxin contamination. The results of this study might play an important role in protecting consumer health and safety screening of marine products.

Molecular cloning, expression and characterization of programmed cell death 10 from sheep (Ovis aries)

Programmed cell death 10 (PDCD10) is a highly conserved adaptor protein. Its mutations result in cerebral cavernous malformations (CCMs). In this study, PDCD10 cDNA from the buffy coat of Small Tail Han sheep (Ovis aries) was cloned from a suppression subtractive hybridization cDNA library, named OaPDCD10. The full-length cDNA of OaPDCD10 was 1343bp with a 639bp open reading frame (ORF) encoding 212 amino acid residues. Tissue distribution of OaPDCD10 mRNA determined that it was ubiquitously expressed in all tested tissue samples, and the highest expression was observed in the heart. The differential expression of OaPDCD10 between infected sheep (challenged with Brucella melitensis) and vaccinated sheep (vaccinated with Brucella suis S2) was also investigated. The results revealed that, compared to the control group, the expression of OaPDCD10 from infected and vaccinated sheep was both significantly up-regulated (p<0.05). Moreover, the expression levels of OaPDCD10 from the vaccinated sheep were significantly higher than the infected sheep (p<0.05) after 30days post-inoculation. The recombinant OaPDCD10 (rOaPDCD10) protein was expressed in Escherichia coli BL21 (DE3), and then purified by affinity chromatography. The rOaPDCD10 protein was demonstrated to induce apoptosis and promote cell proliferation. Our studies are intended to discover potential diagnostic biomarkers of brucellosis to discern infected sheep from vaccinated sheep, and OaPDCD10 could be considered as a potential diagnostic biomarker of brucellosis.

Magnetic bead and gold nanoparticle probes based immunoassay for β-casein detection in bovine milk samples

In this work, a double-probe based immunoassay was developed for rapid and sensitive determination of β-casein in bovine milk samples. In the method, magnetic beads (MBs), employed as supports for the immobilization of anti-β-casein polyclonal antibody (PAb), were used as the capture probe. Colloidal gold nanoparticles (AuNPs), employed as a bridge for loading anti-β-casein monoclonal antibody (McAb) and horseradish peroxidase (HRP), were used as the amplification probe. The presence of β-casein causes the sandwich structures of MBs-PAb-β-casein-McAb-AuNPs through the interaction between β-casein and the anti-β-casein antibodies. The HRP, used as an enzymatic-amplified tracer, can catalytically oxidize the substrate 3,3',5,5'-tetramethylbenzidine (TMB), generating optical signals that are proportional to the quantity of β-casein. The linear range of the immunoassay was from 6.5 to 1520ngmL(-1). The limit of detection (LOD) was 4.8ngmL(-1) which was 700 times lower than that of MBs-antibody-HRP based immunoassay and 6-7 times lower than that from the microplate-antibody-HRP based assay. The recoveries of β-casein from bovine milk samples were from 95.0% to 104.3% that had a good correlation coefficient (R(2)=0.9956) with those obtained by an official standard Kjeldahl method. For higher sensitivity, simple sample pretreatment and shorter time requirement of the antigen-antibody reaction, the developed immunoassay demonstrated the viability for detection of β-casein in bovine milk samples.

Enzyme-antibody dual labeled gold nanoparticles probe for ultrasensitive detection of κ-casein in bovine milk samples

A dual labeled probe was synthesized by coating gold nanoparticles (AuNPs) with anti-κ-CN monoclonal antibody (McAb) and horseradish peroxidase (HRP) enzyme on their surface. The McAb was used as detector and HRP was used as label for signal amplification catalytically oxidize the substrate. AuNPs were used as bridges between the McAb and HRP. Based on the probe, an immunoassay was developed for ultrasensitive detection of κ-CN in bovine milk samples. The assay has a linear response range within 4.2-560 ng mL(-1). The limit of detection (LOD) was 4.2 ng mL(-1) which was 10 times lower than that of traditional McAb-HRP based ELISA. The recoveries of κ-CN from three brand bovine milk samples were from 95.8% to 111.0% that had a good correlation (R(2)=0.998) with those obtained by official standard Kjeldahl method. For higher sensitivity and as simple as the traditional ELISA, the developed immunoassay could provide an alternative approach for ultrasensitive detection of κ-CN in bovine milk sample.

Simple, specific, sensitive and rapid loop-mediated method for detecting Yersinia enterocolitica

Yersinia enterocolitica (YE) is a main pathogenic bacterium causing diarrhea and yersiniosis occurs in both developed and developing countries with high incidence. YE in contaminated food is able to survive for a long duration even under cold storage, thereby enhancing the risk of food infection. In this study, a new loop-mediated isothermal amplification (LAMP) method showing the characteristics of simplicity, rapidity, high specificity and sensitivity was established by targeting outL of pathogenic YE. Two inner-primers and outer-primers were designed and LAMP reaction was optimized for Mg2+, betaine, dNTPs and inner primers concentrations, reaction temperature and time. Sensitivity and specificity of the LAMP assay was evaluated using YE genomic DNA and those of 44 different bacteria strains, respectively. Validation of LAMP detection method was by employing meat samples spiked with varying CFU of YE. The optimized LAMP assay was specific, capable of detecting 97 fg of genomic DNA (equivalent to 37 genome copies) of YE (100-fold more sensitive than PCR) and 80 CFU/ml of YE-spiked meat samples based on ethidium bromide stained amplicon bands on agarose gel-electrophoresis and on GelRed fluorescence of the LAMP reaction solution, respectively. This rapid, sensitive and specific LAMP technique should enable application in field inspection of Y. enterocolitica in food.

A rapid immunomagnetic beads-based immunoassay for the detection of β-casein in bovine milk

An immunomagnetic beads-based enzyme-linked immunosorbent assay (IMBs-ELISA) was developed for the detection of β-casein in bovine milk. Immunomagnetic beads (IMBs) were employed as the solid phase. The anti-β-casein monoclonal antibody (McAb) bound to IMBs was used as capture probe and an anti-β-casein polyclonal antibody (PcAb), labelled with horseradish peroxidase (HRP), was employed as detector probe. Three reaction and two washing steps were needed. Each reaction needed 10 min or less, which significantly shortened detection compared with classic sandwich ELISA. β-Casein in bovine milk was detected across a linear range (2-128 μg mL(-1)). Application results were in accordance with the Kjejdahl method, which suggests the IMBs-ELISA is rapid and reliable for the detection of β-casein in bovine milk.

Production of a monoclonal antibody and development of an immunoassay for detection of Cr(III) in water samples

In this study we report the production of a monoclonal antibody (Mab) specific for Cr(III)-chelate and the development of a competitive immunoassay for detection of Cr(III) in water samples. In the assay, the complete antigen (Cr(III)-ITCBE-BSA) was used as coating antigen, and Cr(III)-ITCBE as competitor competes with coating antigen to bind with Mab. Using this approach, the spiked water samples with Cr(III) were detected. The linear range of the detection was 0.7-12.4 ng mL(-1). The limit of the detection (LOD) was 0.51 ng mL(-1). The spiked results were also confirmed by ICP-MS, which showed a good correlation (R(2)=0.997) between the two methods. The results indicated that the developed assay was reliable and suitable for the detection of Cr(III) in water samples.

Direct competitive immunosorbent assay for detection of MEHP in human urine

Di-(2-ethylhexyl) phthalate (DEHP) is the most commonly used plasticizer for flexible polyvinyl chloride (PVC), which is also known as one of the environmental endocrine disruptors with the reproductive, developmental and embryonic toxicity after entering human body. Mono-2-ethylhexyl phthalate (MEHP) is one of the most complicate metabolites from DEHP in vivo and responsible for many toxic effects of DEHP. In order to evaluate human exposure to DEHP, a direct competitive enzyme-linked immunosorbent (dcELISA) based on monoclonal antibody (mAb) was developed to detect MEHP. A hybridoma cell line 4B9 secreting mAb against MEHP was prepared, and the horseradish peroxidase (HRP) labeled antigen as a probe in the dcELISA was made. After optimization of ELISA reaction conditions, the standard curve with a linear range from 0.56 to 1000 ng mL(-1) and a detection limit of 0.39 ng mL(-1) was established. The cross-reactivities of anti-MEHP mAb to other ten phthalate esters were less than 5% except for mono-methylphthalate (MME). The average recoveries of MEHP from distilled water and negative human urine were both between 87.4% and 94.72% with coefficient of variation (CV) less than 5%. Here, the ELISA method on detecting MEHP was successfully established and applied to real urine sample analyses and the results were confirmed by HPLC. Furthermore, it was indicated that the immunoassay was reliable and suitable for monitoring MEHP.

A novel analytical probe binding to a potential carcinogenic factor of N-glycolylneuraminic acid by SELEX

N-glycolylneuraminic acid (Neu5Gc) is an abundant sialic acid in many mammals and is present in the glycoconjugates of most deuterostome animals. Neu5Gc also occurs in fresh samples of human tumors and fetuses. However, very little is known about the expression level and biologic functions of Neu5Gc due to the limitations of available analytical probes for detection methods. In this study, we first report the development of aptamers specific to Neu5Gc screened by Systematic Evolution of Ligands by Exponential Enrichment (SELEX). After 15 selection rounds, cloning, sequencing and enzyme-linked immuno sorbent assay (ELISA) analysis, 6 different selected aptamers showed specificity for Neu5Gc. Among these 6 aptamers, N8 showed the best half maximal inhibitory concentration (IC50) value (127 ng mL(-1)) and had a relatively high affinity constant (Ka=6.68 × 10(9)M(-1)). The aptamers selected in this study will provide a novel analytical probe for the development of a biosensor to detect Neu5Gc in tissues and sera from patients with tumors as well as to detect Neu5Gc in animal-derived foods. In addition, the successful aptamer candidate can solve the problem that antibody is difficult to prepare in immunological assays. Thus, the discovery of novel aptamers specific for Neu5Gc is important for developing new methods of detecting Neu5Gc for the diagnosis and prevention of cancer as well as food poisoning.

Dioxins and furans releases in Iranian mineral industries

In this project, emissions of Poly-Chlorinated Dibenzo-p-Dioxins and Dibenzo-Furans (PCDD/Fs) were investigated and estimated for selected Iranian mining and ore processing industries, such as integrated iron & steel plant, primary production of aluminium and copper metal, and the production of cement. As a first step of this study the annual emission of PCDD/Fs was estimated at 120gTEQannum(-1) on the base of the UNEP standardised Toolkit for identification and quantification of dioxin and furan releases. Steel and cement were identified as major emission sources and earmarked for further scrutiny. For that reason, filter dust arising in these plants was sampled and analysed, as well as all raw materials employed. After extraction and clean-up according to standard methods, the resulting liquid samples were analysed and quantified by HRGC-HRMS. Complementary analyses using methods such as XRF, TGA/DTA were performed and the emission results statistically evaluated, in order to put PCDD/F emissions in perspective. It is concluded that the dioxins load of cement dust is unusually low, following the low carbon in raw materials, the use of natural gas as a fuel and the absence of waste incineration. Also the production of iron by direct reduction of ore is a low dioxins process; dioxin loads in dust are as usual - correlated with the presence of catalytic metals. Loss on ignition and chlorine are anti-correlated with the main earth elements and with sulphur oxides.

In vitro and in vivo antitumor effects of the recombinant immunotoxin IL6(T23)-PE38KDEL in multiple myeloma

IL6(T23)-PE38KDEL is a chimeric molecule composed of interleukin 6 (IL6), missing the N-terminal 23 amino acids, and fused to a truncated mutant form of Pseudomonas exotoxin (PE38KDEL). The aim of this study was to evaluate this recombinant immunotoxin in terms of its specific cytotoxicity to IL6R-overexpressing multiple myeloma (MM) cells in vitro, as well as its antitumor effects and side effects in vivo. IL6(T23)-PE38KDEL was expressed in Escherichia coli, refolded and purified from inclusion bodies. The purified IL6(T23)-PE38KDEL was found to be selectively cytotoxic to IL6 receptor-positive tumor cells in vitro. IC(50) values of IL6(T23)-PE38KDEL were evaluated by MTS assay. Toxicity and maximum-tolerated dose of IL6(T23)-PE38KDEL were determined in mice. The antitumor activity of IL6(T23)-PE38KDEL was evaluated in mice with MM through intravenous injection and interventional therapy. Intravenous administration of IL6(T23)-PE38KDEL caused a significantly increased survival time in treated mice, and exhibited dose- and time-dependent antitumor effects against MM mice. Moreover, complete tumor regression was observed in 30 and 80% of mice treated intravenously and intraperitoneally, respectively, with 0.4 mg/kg/day for 10 days. These results demonstrated that the recombinant immunotoxin IL6(T23)-PE38KDEL kills IL6R-overexpressing cancer cells, and causes significant tumor regression.

Production of monoclonal antibody and application in indirect competitive ELISA for detecting okadaic acid and dinophytoxin-1 in seafood

BACKGROUND, AIM, AND SCOPE

Okadaic acid (OA) and analogues of dinophysistoxin (DTX) are key diarrheic shellfish poisoning (DSP) toxins, which possibly arouse DSP symptoms by consuming the contaminated shellfish. Because of the stable toxicity in high temperature and the long-term carcinogenicity, the outbreaks of DSP related to consumption of bivalve mollusks contaminated by DSP toxins pose a hazard to public health. Therefore, it is worth developing a fast and reliable analytical method for the detection of OA and analogues in shellfish. In this paper, an indirect competitive enzyme-linked immunosorbent assay (ELISA) (icELISA) for detecting OA and DTX-1 in seafood was developed based on monoclonal antibody (McAb).

METHODS

The OA was conjugated to human immunoglobulin G (IgG) and bovine serum albumin (BSA) by the active ester method as the immune antigen and the detective antigen. The spleen cells from BALB/c mice immunized with OA-IgG were fused with SP2/0 myeloma cells. A hybridoma cell line, which secreted McAb against OA, was selected by "limiting dilution" cloning. An icELISA was developed based on immobilized conjugate (OA-BSA) competing the McAb with the free OA in seafood sample.

RESULTS

A hybridoma cell line, which secreted IgG1 subclass monoclonal antibody (McAb) against OA, was selected. The IC(50) of the McAb for OA and dinophytoxin-1 (DTX-1) were 4.40 and 3.89 ng/mL, respectively. Based on the McAb, an indirect competitive ELISA for detection of OA and DTX-1 in seafood was developed. The regression equation was y = 54.713x - 25.879 with a coefficient correlation of R (2) = 0.9729. The linear range and the limit of detection were 0.4-12.5 and 0.45 ng/mL, respectively. The average recovery of OA and DTX-1 spiked shellfish was 82.29% with the coefficient of variation of 7.67%.

CONCLUSION

The developed icELISA is a fast, sensitive, and convenient assay for detecting of total amount of OA and DTX-1 in seafood.

Cloning, expression, and genus-specificity analysis of 28-kDa OmpK from Vibrio alginolyticus

Some Vibrio species are universal marine pathogens and Vibrio infections are often encountered due to consumption of raw or uncooked seafood. The outer membrane proteins, playing a key role in interaction between bacteria and hosts, are potential candidates for development of vaccine and markers of the genus Vibrio. In this study, the ompK (outer membrane protein K) genes of Vibrio alginolyticus, V. vulnificus, V. parahaemolyticus, V. fluvialis, and V. mimicu were cloned with 798 to 822 nucleotides encoding 266 to 274 amino acids. The ompK gene from V. alginolyticus was expressed in Escherichia coli using pET-22b expression vector. The recombinant fusion OmpK protein with 6xHis tag was purified with nickel chelate affinity chromatography. The polyclonal antibody (titer, 1:102400) against V. alginolyticus OmpK was developed in guinea pigs and it positively reacted with each of 5 Vibrio species but negative to other 18 Gram-negative bacterial strains. The result suggests that Vibrio OmpK protein could be a genus-specific antigen, which can be used for developing vaccines and rapid detection of multiple Vibrio species.

Colloidal gold probe-based immunochromatographic assay for the rapid detection of brevetoxins in fishery product samples

One-step immunochromatographic assay using colloidal gold-labeled monoclonal antibody (Mab) probe for the rapid detection of brevetoxins (PbTxs) in fishery product samples was developed. The described assay was based on a competitive format using two antibodies. The primary antibody was conjugated with colloidal gold (detector reagent), the secondary antibody (capture reagent) was immobilized within a defined detection zone (control line) on a diagnostic cellulose nitrate membrane. The toxin in sample compete with immobilized toxin to bind with gold conjugated Mab. The mobile complex (colloidal gold-Mab-toxin) can be captured by the secondary antibody but cannot be captured by BSA-PbTx (test line). The color density of the test line correlated with the concentration of PbTx in sample in the range 10-4000 ng mL(-1). Spiked samples were detected by the assay and the visual detection limit was found to be 20 ng mL(-1). This qualitative test based on the visual evaluation of results did not require any equipment. The assay time for PbTx detection was less than 10 min, suitable for rapid testing on-site.