Monoclonal Antibodies for the Mycotoxins Deoxynivalenol and 3-Acetyl-Deoxynivalenol

Production and characterization of a monoclonal antibody that cross-reacts with the mycotoxins nivalenol and 4-deoxynivalenol

Nivalenol is a mycotoxin produced by certain fungi that are pathogenic to important cereal crops, in particular maize, wheat, and barley. This toxin, 3alpha,4beta,7alpha,15-tetrahydroxy-12,13-epoxytrichothec-9-en-8-one, is found worldwide and is closely related to 4-deoxynivalenol (DON or vomitoxin), a mycotoxin associated with outbreaks of Fusarium head blight in North America. The literature on the toxicity of nivalenol suggests it is similar, if not more toxic, than DON. Despite the development of rapid immunologically based assays for detecting DON, such assays have not existed for detecting nivalenol without chemical modification of the analyte. This paper describes the development of a monoclonal antibody using a nivalenol-glycine protein conjugate. The monoclonal antibody was most specific for an acetylated form of DON (3-Ac-DON), but it exhibited sensitivity and cross-reactivity that were useful for detecting nivalenol and DON at relevant levels without the need to modify either toxin chemically. In an competitive indirect ELISA format, the concentrations of toxins able to inhibit colour development by 50% (IC50) were 1.7, 15.8, 27.5, 68.9, and 1740 ng ml(-1) for the mycotoxins 3-Ac-DON, DON, nivalenol, 15-Ac-DON, and fusarenon-X, respectively. The antibody was also used to develop a competitive direct ELISA for DON and nivalenol, with IC50's of 16.5 ng ml(-1) (DON) and 33.4 ng ml(-1) (nivalenol). These assays are capable of detecting both DON and nivalenol simultaneously, a property that may be useful in regions where these toxins co-occur or in formats, such as immunoaffinity columns, where co-isolation of both toxins is desirable.

Optimization of a fluorescence polarization immunoassay for rapid quantification of deoxynivalenol in durum wheat-based products

A fluorescence polarization immunoassay previously described for deoxynivalenol (DON) screening in wheat was optimized for the rapid quantification of DON in durum wheat kernels, semolina, and pasta. A background signal was observed in both spiked and naturally contaminated samples, strictly depending on the testing matrix. After subtracting the background DON level for durum wheat (0.27 microg of DON per g), semolina (0.08 microg of DON per g), and pasta (0.04 microg of DON per g), an accurate quantification of DON was possible at levels greater than 0.10 microg/g for all matrices. Average recoveries from spiked samples (0.25 to 1.75 microg/g) were 98, 102, and 101% for wheat, semolina, and pasta, respectively. Comparative analyses of 35 naturally contaminated durum wheat samples, 22 semolina samples, and 26 pasta samples performed by both the fluorescence polarization method and high-pressure liquid chromatography/immunoaffinity cleanup showed a good correlation (r > 0.995). The fluorescence polarization method showed better accuracy and precision with respect to the high-pressure liquid chromatography method and is suitable for the rapid and quantitative determination of DON in durum wheat-based products at levels foreseen by existing or coming international regulations.

Detection of deoxynivalenol in foods and indoor air using an array biosensor

Deoxynivalenol (DON), a mycotoxin produced by several Fusaruim species, is a worldwide contaminant of foods and feeds. Because of the potential dangers due to accidental or intentional contamination of foods with DON, there is a need to develop a rapid and highly sensitive method for easy identification and quantification of DON. In this study, we have developed and utilized a competitive immunoassay technique to detect DON in various food matrixes and indoor air samples using an array biosensor. A DON-biotin conjugate, immobilized on a NeutrAvidin-coated optical waveguide, competed with the DON in the sample for binding to fluorescently labeled DON monoclonal antibodies. To demonstrate a simple procedure amenable for on-site use, DON-spiked cornmeal, cornflakes, wheat, barley, and oats were extracted with methanol-water (3:1) and assayed without cleanup or preconcentration. The limits of detection ranged from 0.2 ng/mL in buffer to 50 ng/g in oats. The detection limit of DON spiked into an aqueous effluent from an air sampler was 4 ng/mL.

Rapid methods for deoxynivalenol and other trichothecenes

Method development for deoxynivalenol (DON) and other trichothecenes in recent years was driven by the analytical necessities arising from its widespread (and increasing) occurrence in foods and feeds. This has resulted in the establishment of guideline levels for animal feed, tolerable daily intake (TDI) levels for humans, and most importantly, in the prospect of low-tolerance levels for these toxins in foods in the near future. In order to ensure reliable determination of the toxin content at the tolerance levels, routine analytical methods must have detection limits of less than the tolerance level. This paper intends to give an overview of current analytical developments of rapid testing for deoxynivalenol and other trichothecene mycotoxins, with a special focus on antibody-based techniques. This includes high-throughput instrumental analysis for the laboratory environment, as well as rapid visual tests for on-site testing. The applicability of rapid tests within an integrated detection system for mycotoxins in foods is discussed.

Rapid surface plasmon resonance-based inhibition assay of deoxynivalenol

Deoxynivalenol belongs to a group of highly toxic fungal metabolites produced by Fusarium species that may contaminate food and animal feed, mostly grains. Three different monoclonal mouse anti-deoxynivalenol antibodies were compared for the development of a surface plasmon resonance (SPR)-based immunoassay for the selective and quantitative determination of deoxynivalenol in naturally contaminated matrices. A conjugate of deoxynivalenol with the protein casein was prepared and immobilized on the sensor chip surface. An excess of antibody was added to each test solution before the measurement. The assay was based on the competition for antibody binding between the immobilized deoxynivalenol conjugate on the sensor and the free deoxynivalenol molecules in the test solution. The deoxynivalenol-casein sensor could be reused more than 500 times without significant loss of activity using 6 M guanidine chloride solution for regeneration. The cross-reactivity of the three antibodies in the SPR assay was tested with other trichothecene mycotoxins (3-acetyl-deoxynivalenol, 15-acetyl-deoxynivalenol, nivalenol, HT2-toxin, and T2-toxin). The only sample preparation was extraction with max 80 vol % acetonitrile and 10-fold dilution with the running buffer. The assay had an optimal range between 2.5 and 30 ng/mL deoxynivalenol in the test solution. Most results of the SPR-based assay were in agreement with liquid chromatography/tandem mass spectrometry measurements of naturally contaminated wheat samples.

Identification of grouper (Epinephelus guaza), wreck fish (Polyprion americanus), and Nile perch (Lates niloticus) fillets by polyclonal antibody-based enzyme-linked immunosorbent assay

An indirect enzyme-linked immunosorbent assay (ELISA) has been developed for the species identification of grouper (Epinephelus guaza), wreck fish (Polyprion americanus), and Nile perch (Lates niloticus) fillets. The assay was performed in two different formats, microtiter plates and immunostick tubes, and uses polyclonal antibodies raised in rabbits against muscle-soluble proteins of grouper (anti-GSP), wreck fish (anti-WSP), and Nile perch (anti-PSP). The antibodies were made species-specific by blocking them with the heterologous soluble muscle proteins. Immunorecognition of polyclonal antibodies adsorbed to their specific fish samples was made with swine antirabbit immunoglobulins conjugated to the enzyme horseradish peroxidase. Subsequent enzymatic conversion of the substrate allowed unequivocal identification of the species studied.

Fluorescence polarization as a tool for the determination of deoxynivalenol in wheat

The mould Fusarium graminearum is found worldwide as a pathogen of cereal grains, in particular of wheat and maize, and it produces a mycotoxin known as deoxynivalenol (DON or vomitoxin). Each year, the presence of this compound and related trichothecenes causes substantial losses to agricultural productivity. Rapid methods for the measurement of the toxin in grains are required to monitor and divert effectively contaminated grain from the food supply. A fluorescence polarization (FP) immunoassay using a previously described monoclonal antibody for DON was developed. The assay was based on the competition of unlabeled DON from a sample with a fluorescently tagged DON, DON-fluorescein (DON-FL), for a DON-specific monoclonal antibody in solution. The FP of the tagged DON was increased upon binding with the antibody. In the presence of free toxin, less of the DON-FL was bound and the polarization signal was decreased. The assays were very simple to perform, requiring only mixing of an aqueous extract of wheat with the DON-FL and antibody. The sensitivity of the assay was strongly dependent upon the time between mixing of the sample with the tracer and measurement of the fluorescence polarization, with midpoints for the competition curves ranging from 0.03 microg ml(-1) with a 15-s incubation to >1 microg ml(-1) with a 12-min incubation. Samples of wheat naturally contaminated with DON were evaluated by FP and by an HPLC-UV method, with a good correlation (r2 = 0.97). Although the FP method tended to overestimate DON slightly in the wheat samples, by approxiamtely 20%, the assay was easy to use and very useful for the screening of wheat.

Rapid fluorescence polarization immunoassay for the mycotoxin deoxynivalenol in wheat

The fungus Fusarium graminearum, a pathogen of both wheat and maize, produces a toxin, deoxynivalenol (DON), that causes disease in livestock. A rapid test for DON in wheat was developed using the principle of fluorescence polarization (FP) immunoassay. The assay was based on the competition between DON and a novel DON-fluorescein tracer (DON-FL2) for a DON-specific monoclonal antibody in solution. The method, which is a substantial improvement over our previous DON FP immunoassay, combined a rapid (3 min) extraction step with a rapid (2 min) detection step. A series of naturally contaminated wheat and maize samples were analyzed by both FP immunoassay and liquid chromatography (HPLC-UV). For wheat the HPLC-UV and FP methods agreed well (linear regression r(2) = 0.936), but for maize the two methods did not (r (2) = 0.849). We conclude that the FP method is useful for screening wheat, but not maize, for DON.