Detection of T-2 toxin in Fusarium sporotrichioides-infected corn by enzyme-linked immunosorbent assay

Development of a sensitive monoclonal-based enzyme-linked immunosorbent assay for monitoring T-2 toxin in food and feed

The consumption of food or feed contaminated with high levels of T-2 toxin may cause adverse health effects in humans and other animals. In this study, to monitor T-2 toxin rapidly in food and feed, a sensitive and specific monoclonal antibody (mAb) against T-2 toxin was generated and a simple and rapid indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) developed. T-2 toxin was first converted to T-2-hemisuccinate (T-2HS) and T-2-hemiglutarate (T-2HG), which were then conjugated to bovine serum albumin (BSA) and ovalbumin (OVA) to prepare an immunogen and coating antigen, respectively. After the inoculation of female Balb/c mice and cell fusions, one cell line, 4D8, with the IgG1 isotype was obtained. The 4D8 antibody exhibited the ability specifically to recognise T-2 toxin with IC50 1.46 µg l(-1). Based on this 4D8 mAb, an optimised ic-ELISA protocol was developed using only methanol-water (7:3, v/v) in feed and cereal samples and ethyl acetate in muscle samples. The limits of detection of T-2 toxin in various sample matrices varied from 0.07 to 15.8 µg kg(-1); the recoveries ranged from 50.3% to 113.6%; and the CVs were less than 19.0%. These results suggest that the prepared mAb and the developed ic-ELISA method will be a useful tool for detecting T-2 toxin in foods and feeds.

Simultaneous screening for T-2/HT-2 and deoxynivalenol in cereals using a surface plasmon resonance immunoassay

This manuscript describes a rapid surface plasmon resonance (SPR) immunoassay for the simultaneous determination of the sum of T-2/HT-2 toxins (T-2/HT-2) and deoxynivalenol (DON), in cereals and cereal-based products. The assay is based on an inhibition format employing a monoclonal antibody raised against HT-2 with cross reactivity to T-2 and a polyclonal antibody raised against DON, thereby enabling the detection of the three trichothecene mycotoxins (types A and B). The surface chemistry involved an equal mixture of HT-2 and DON covalently coupled onto a high capacity COOH5 sensor chip. Using the specified antibodies and a mixed toxin sensor surface, and running calibration curves (HT-2 and DON) and samples in parallel it has been proven that it is feasible to develop a multiplex assay on this SPR platform. In-house validation has shown limits of detection of 12, 1 and 29 μg/kg for DON and 31, 47 and 36 μg/kg for HT-2 in wheat, breakfast cereal and maize-based baby food, respectively. Both intra-assay and inter-assay precision were calculated using fortified DON and HT-2 samples. Durum wheat, wheatbased breakfast cereal and maize-based baby food were spiked at various concentration levels and the coefficients of variation calculated ranged from 1.1% to 9.9% for DON and from 1.4% to 11.3% for HT-2. A high correlation was observed between the screening assay and confirmatory mass spectrometry.

A comparative study of qualitative immunochemical screening assays for the combined measurement of T-2/HT-2 in cereals and cereal-based products

Many different immunochemical platforms exist for the screening of naturally occurring contaminants in food from the low cost enzyme linked immunosorbent assays (ELISA) to the expensive instruments such as optical biosensors based on the phenomenon of surface plasmon resonance (SPR). The primary aim of this study was to evaluate and compare a number of these platforms to assess their accuracy and precision when applied to naturally contaminated samples containing HT-2/T-2 mycotoxins. Other important factors considered were the speed of analysis, ease of use (sample preparation techniques and use of the equipment) and ultimately the cost implications. The three screening procedures compared included an SPR biosensor assay, a commercially available ELISA and an enzymelinked immunomagnetic electrochemical array (ELIME array). The qualitative data for all methods demonstrated very good overall agreements with each other, however on comparison with mass spectrometry confirmatory results, the ELISA and SPR assay performed slightly better than the ELIME array, exhibiting an overall agreement of 95.8% compared to 91.7%. Currently, SPR is more costly than the other two platforms and can only be used in the laboratory whereas in theory both the ELISA and ELIME array are portable and can be used in the field, but ultimately this is dependent on the sample preparation techniques employed. Sample preparative techniques varied for all methods evaluated, the ELISA was the most simple to perform followed by that of the SPR method. The ELIME array involved an additional clean-up step thereby increasing both the time and cost of analysis. Therefore in the current format, field use would not be an option for the ELIME array. In relation to speed of analysis, the ELISA outperformed the other methods.

Determination of T-2 toxin in grain and grain products by HPLC and TLC

The purpose of this study was to investigate the T-2 toxin contaminated grain and grain products consumed especially by Turkish population. The T-2 toxin was detected using the high performance liquid chromatography (HPLC) with UV detector at 208 nm and the identify of T-2 was further confirmed by thin layer chromatography (TLC). The recovery was 91 +/- 4.24% for corn flour fortified with the known amount of T-2 toxin (1 ppm). The detection limits of T-2 toxin for the HPLC and the TLC were 25 ng and 50 ng, respectively. A total of 30 commercially available grain and grain product samples were analyzed. Two corn flour samples were found to contain detectable levels of T-2 toxin at a level of 1.60 ppm and 4.08 ppm.

Dipstick enzyme immunoassay to detect Fusarium T-2 toxin in wheat

A dipstick enzyme immunoassay for the rapid detection of Fusarium T-2 toxin in wheat was developed. An Immunodyne ABC membrane was precoated with rabbit anti-mouse immunoglobulins. After the strips were immersed in a solution of monoclonal anti-T-2 toxin antibodies, a direct competitive enzyme immunoassay was performed. This assay included the incubation of the antibody-coated dipsticks in a mixture of sample and T-2 toxin-horseradish peroxidase conjugate. Afterwards, the strips were placed in a chromogen-containing substrate solution (H202-3,3',5,5'-tetramethylbenzidine) for color reaction. The dot color intensity of toxin-positive dipsticks was visually distinguishable from that of the negative control. A portable colorimeter was used to confirm and quantify the visual observations. With coated strips, the tests could be performed in 45 min. The visual detection limit for T-2 toxin in buffer solution was 0.25 ng/ml. Artificially infected wheat samples were extracted with 80% methanol-water. A dilution of the raw extract of 1:8 was sufficient to avoid matrix effects. It was possible to make visually a clear distinction between the negative control and a wheat extract spiked with 12 ng/g.

In vitro neutralization of T-2 toxin toxicity by a monoclonal antibody

A T-2 toxin specific monoclonal antibody, IgG1 K, with a low level of ELISA cross-reactivity to Acetyl T-2, HT-2, and iso T-2 toxins has been produced. The ability of this monoclonal antibody to neutralize the cytotoxicity of T-2 toxin in PHA stimulated cultures of human lymphocytes was determined by the MTT method. The complete neutralization of the toxic effect of 0.02 microM T-2 toxin was obtained with 0.03 microM of MoAb, whereas the 50% neutralizing dose (ND50) was observed at 0.009 microM of MoAb. Partial neutralization was observed with Acetyl T-2 toxin (ND50 = 0.038 microM) and HT-2 (ND50 = 0.94 microM). These results could represent a rational for clinical use of T-2 toxin specific monoclonal antibody in prophylaxis and therapy of T-2 toxemia.

Levels of five mycotoxins in grains harvested in Atlantic Canada as measured by high performance liquid chromatography

An analytical protocol using high performance liquid chromatography (HPLC) was used to analyze samples of spring wheat, winter wheat, 2-row barley, and 6-row barley over a period of three years for the presence of five mycotoxins. These included deoxynivalenol, zearalenone, T-2 toxin, HT-2 toxin, and diacetoxyscirpenol. The protocol employed a single extraction step using acetonitrile-water and two cleanup procedures. One utilized a solid-phase extraction column and the other a charcoal-alumina column. Detection limits ranged from 0.02 to 0.15 micrograms of mycotoxin g-1 grain. Little T-2 toxin, HT-2 toxin, or diacetoxyscirpenol was found in the samples. Deoxynivalenol was detected in 53 to 62% of the samples tested and zearalenone in 25-29% of the samples. Several enzyme-linked immunosorbent assays were used for comparison purposes with deoxynivalenol, zearalenone, and T-2 toxin. These kits provided reliable qualitative, but not quantitative, data.

Application of immunochemical assays to food analysis

Immunochemical assays are powerful bioanalytical techniques with application to several areas in food science, including food analysis, microbiology, nutrition, food safety, food quality, and process control. In principle, immunochemical techniques can be applied to the analysis of any compound, with only one specific antibody needed that can be obtained either from laboratory animals or, when available, from commercial sources. A well-designed immunochemical assay can detect targeted compounds at levels as low as 10(-12) M. Immunochemical techniques require little or no sample pretreatment, making these analytical procedures relatively rapid. The initial cost of developing an immunoanalytical assay may be high, but when the procedure is well established, the cost per test is often a fraction of that for other analytical methods. For these reasons, immunoanalytical assays provide an attractive alternative for the food analyst who requires either inexpensive qualitative screening tests or reliable quantitative methods with a high degree of sensitivity. This review concentrates on the use of enzyme immunoassay to address analytical problems in food chemistry and the analysis of various food components.

Application of immunoassay in the food industry

Immunoassay techniques using the highly specific and sensitive nature of immunological reactions have been developed and applied in the food industry for detecting the naturally occurring constituents, antibiotics, pesticide residues, microorganisms, and fragments of microbial constituents related to food analysis, food production, food processing, and food safety. Both polyclonal and monoclonal antibodies are employed for the development of the various immunoassay systems, including enzyme-linked immunoassay (ELISA) and radioimmunoassay (RIA). Immunoassay techniques provide complementary and/or alternate approaches in reducing the use of costly, sophisticated equipment and analysis time, but still maintaining reliability and improved sensitivity. Immunoassay techniques in their most simple forms provide excellent screening tools to detect adulteration and contaminations qualitatively. The application of immunoassay techniques contributes tremendously to the quality control and safety of our food supply.

Radioimmunoassay of nivalenol in barley

Antibodies against nivalenol (NIV) tetraacetate (Tetra-Ac-NIV) were prepared by immunizing rabbits with a hemisuccinate derivative of 8-hydroxy-3,4,7,15-tetraacetyl-12, 13-epoxytrichothece-9-en conjugated to bovine serum albumin. A radioimmunoassay system with one of these sera was developed to measure NIV contamination in barley. The detection limit for Tetra-Ac-NIV was about 0.5 ng/ml. The relative cross-reactivities of the antiserum with Tetra-Ac-NIV, acetyl T-2 toxin, and scirpenol triacetate, which were determined by the competitive radioimmunoassay, were 1, 0.78, and 0.56, respectively. Other derivatives showed no cross-reactivity. For the determination of NIV in a barley sample, NIV was extracted from the sample with acetonitrile-water (7:3), defatted with hexane, and then acetylated with acetic anhydride to form Tetra-Ac-NIV. The reaction mixture was loaded onto a C18 cartridge to remove excess reagents and impurities. Tetra-Ac-NIV was eluted from the cartridge with 50% methanol in water, and the eluate was subjected to radioimmunoassay. Analysis of six naturally contaminated barley samples for NIV revealed that radioimmunoassay results agreed well with gas chromatographic analyses.

Production and characterization of monoclonal antibodies to nivalenol tetraacetate and their application to enzyme-linked immunoassay of nivalenol

Three monoclonal antibodies were obtained by the fusion of mouse myeloma cells with splenocytes isolated from BALB/c mice that had been immunized with 8-hydroxy-3,4,7,15-tetraacetyl-nivalenol hemiglutarate covalently bound to bovine serum albumin. These anti-nivalenol tetraacetate monoclonal antibodies were of the IgG type and highly specific to nivalenol tetraacetate, with an apparent association constant of about 10(8)M-1. The relative cross-reactivities of one monoclonal antibody with nivalenol tetraacetate, acetyl T-2 toxin, and scirpenol triacetate were found to be 1.0, 0.02 and 0.03, respectively. Other derivatives showed no cross-reactivity at all. An indirect enzyme-linked immunosorbent assay (ELISA) based on the competitive binding principle was developed using the antibody from clone D18.102.59. The sensitivity of the system was about 0.1 ng of nivalenol tetraacetate per assay. Comparison of nivalenol levels detected in naturally contaminated barley samples by competitive indirect ELISA and gas chromatography (GC) showed good agreement, indicating that the antibody is useful for the measurement of nivalenol in naturally contaminated cereals and grains.

Production and characterization of a monoclonal antibody cross-reactive with most group A trichothecenes

A monoclonal antibody cross-reactive with most group A trichothecenes was produced by fusion of P3/NS-1/1-AG4-1 myeloma cells with spleen cells isolated from a BALB/c mouse that had been immunized with 3-acetyl-neosolaniol-hemisuccinate conjugated to bovine serum albumin. One stable clone, H159B1D5, which produced monoclonal antibody that bound with both T-2 toxin and diacetoxyscirpenol (DAS) was obtained after subcloning. Enzyme-linked immunosorbent assay (ELISA) revealed that the antibody belongs to the immunoglobulin G1 (kappa chain) isotype and had binding constants of 2.81 x 10(9), 1.05 x 10(9), and 1.57 x 10(8) liters per mole for T-2 tetraol tetraacetate, T-2 toxin, and DAS, respectively. The relative cross-reactivities of the antibody with T-2 tetraol tetraacetate, T-2 toxin, and DAS were 200, 100, and 20, respectively, with tritiated T-2 toxin as the marker ligand. The relative cross-reactivities for the above toxins were 667, 100, and 73, respectively, with tritiated DAS as the marker ligand. No cross-reaction with HT-2 and deoxynivalenol triacetate was observed in either system. By using this monoclonal antibody, an indirect ELISA for analysis of T-2 toxin was also developed. The linear portion of the standard curve for analysis of T-2 toxin in each analysis by radioimmunoassay and ELISA was in the range of 0.1 to 2 ng and 0.05 to 1.0 ng, respectively.

A sensitive enzyme-linked immunosorbent assay for detection of T-2 toxin with monoclonal antibodies

Six monoclonal antibodies (mAbs, T-2.1, 2, 3, 4, 5, 6) which react with a trichothecene mycotoxin, T-2 toxin (T-2), were prepared. All antibodies specifically reacted with T-2 but less (0.5% of T-2) with the metabolites such as HT-2 toxin and 3'-hydroxy-T-2 toxin. Significant but less than 0.02% cross-reactivity was observed with T-2 triol, 3'-hydroxy-HT-2 toxin and neosolaniol. No significant reaction with other trichothecenes such as deoxynivalenol, nivalenol, fusarenon-X, crotocin, or roridin A was observed. The least detectable amount of T-2 with the best mAb T-2.1 was 2.5 pg T-2 per assay. This specific and highly sensitive assay for T-2 was applied for the quantitation of T-2 in wheat flour spiked with mycotoxin, with combination of a simple extraction procedure.

Development of a sensitive enzyme-linked immunosorbent assay for the detection of diacetoxyscirpenol

An enzyme-linked immunosorbent assay (ELISA) for the detection of diacetoxyscirpenol (DAS) was developed. Antibodies against DAS were obtained after immunization of rabbits with DAS-hemiglutarate-human serum albumin (DAS-HG-HSA). After an immunization period of 6 weeks a sufficient level of specific antibodies was reached. A DAS-hemisuccinate-horseradish peroxidase-conjugate (DAS-HS-HRP) was prepared by an ester method and used as enzyme-labelled toxin in the competitive assay. The detection limit for DAS was about 10 pg/ml. The relative cross reactivity of the assay was 597.5, 5.2, 100.0, 2.5, and 1.5% for 3 alpha-acetyl-DAS, DAS, T-2 toxin, neosolaniol, and 15-acetoxyscirpenol, respectively.

Improved preparation of T-2 toxin-protein conjugates

T-2 toxin (T-2) was converted into T-2 hemisuccinate (T-2 HS), T-2 hemiglutarate (T-2 HG) and T-2 hemiphthalate (T-2 HP), and conjugated with bovine serum albumin (BSA), ovalbumin (OVA) and keyhole limpet haemocyanin (KLH) using carbodiimide under various conditions. The recovery of T-2 conjugated proteins and the amount of T-2 bound were largely dependent on the amount of coupling reagent, pH, reaction temperature, buffer and reaction time. In regard to T-2 derivatives binding with a protein, T-2 HG was the most efficient, followed by T-2 HS and then T-2 HP. With regard to T-2 to protein binding, KLH was the most efficient, followed by BSA and then OVA. To promote T-2-protein binding, phosphate-buffered saline was more effective than cacodylate buffer. Within a pH range of 5.5-7.0, weakly acidic conditions were more efficient than neutral conditions for promoting T-2-protein binding.

Enzyme immunoassay for the macrocyclic trichothecene roridin A: production, properties, and use of rabbit antibodies

Antisera against roridin A were prepared by using a roridin A-hemisuccinate derivative coupled to human serum albumin as the immunogen. Antibodies could be detected in the sera of the immunized rabbits as early as 4 weeks after the initial exposure. After one booster injection at week 14, high antibody titers were measured over a period of 21 weeks. The specificity and sensitivity of the antibodies were tested by using roridin A-hemisuccinate coupled to horseradish peroxidase as an enzyme-linked toxin in a competitive assay with a double-antibody solid phase. The assay was most specific for the tested macrocyclic trichothecenes, and the relative cross-reactivities with roridin A, roridin J, verrucarin A, satratoxin H, and satratoxin G were 1, 0.41, 0.15, 0.15, and 0.07, respectively. When 16 nonmacrocyclic trichothecenes were tested, only diacetylverrucarol (0.0015) and verrucarol (0.0005) showed minor cross-reactivity. The sensitivity of the enzyme immunoassay for the detection of roridin A was in the range of 5 to 50 ng/ml (0.16 to 1.6 ng per assay).

Production and characterization of antibodies against HT-2 toxin and T-2 tetraol tetraacetate

Three new immunogens which were prepared by conjugation of the carboxymethyl oxime (CMO) derivatives of HT-2 toxin, T-2 tetraol (T-2 4ol), and T-2 tetraol tetraacetate (T-2 4Ac) to bovine serum albumin (BSA) were tested for the production of antibodies against the major metabolites of T-2 toxin. Antibodies against HT-2 toxin and T-2 4Ac were obtained from rabbits 5 to 10 weeks after immunizing the animals with CMO-HT-2-BSA and CMO-T-2 4Ac-BSA conjugates. Immunization with CMO-T-2 4ol-BSA resulted in no antibody against T-2 4ol. The antibody produced against HT-2 toxin had great affinity for HT-2 toxin as well as good cross-reactivity with T-2 toxin. The relative cross-reactivities of anti-HT-2 toxin antibody with HT-2 toxin, T-2 toxin, iso-T-2 toxin, acetyl-T-2 toxin, 3'-OH HT-2, 3'-OH T-2, T-2 triol, and 3'-OH acetyl-T-2, were 100, 25, 10, 3.3, 0.25, 0.15, 0.12 and 0.08%, respectively. Antibody against CMO-T-2 4Ac was very specific for T-2 4Ac and had less than 0.1% cross-reactivity with T-2 toxin, HT-2 toxin, acetyl-T-2 toxin, diacetoxyscirpenol, deoxynivalenol, and deoxynivalenol triacetate as compared with T-2 4Ac. The detection limits for HT-2 toxin and T-2 4ol by radioimmunoassay were approximately 0.1 and 0.5 ng per assay, respectively.

Hapten-protein conjugates prepared by the mixed anhydride method. Cross-reactive antibodies in heterologous antisera

Poly-L-lysine conjugates of three structurally unrelated mycotoxins were made by either a mixed anhydride intermediate (MA) or an activated N-hydroxysuccinimide ester intermediate (AE). Control conjugates, with no mycotoxin, were also prepared by each method. Antisera elicited by mycotoxin-albumin conjugates produced by the MA method bound to the three poly-L-lysine-MA mycotoxin conjugates and the MA control conjugate , but bound only to the poly-L-lysine-AE conjugates of the homologous mycotoxin. Binding of antisera to homologous poly-L-lysine conjugates was always inhibited by free hapten when the conjugate was prepared by the AE method but not by the MA method. The specific inhibition of antibody binding by various synthetic haptens indicated that the cross-reactions associated with the MA method were due to the undesired conjugation of isobutylformate during the mixed anhydride procedure.

Improved method for production of antibodies against T-2 toxin and diacetoxyscirpenol in rabbits

A new, improved approach for the production of antibodies against T-2 toxin and diacetoxyscirpenol (DAS) was developed. The method involves the use of immunogens which were prepared by conjugating O-carboxymethoxyl oxime (CMO) derivatives of both toxins to bovine serum albumin (BSA). Isomers a and b of CMO-T-2 toxin and isomer b of CMO-DAS were tested. Antibodies against both toxins were demonstrated as early as 4 weeks after immunization. a-CMO-T-2-BSA conjugate was a better immunogen than the b isomer, and the highest titers (6,000) were reached 14 weeks after immunization and one booster injection. Antibody titers for rabbits immunized with the b isomer of CMO-T-2 never reached more than 2,000. The specificity of antibodies obtained from rabbits after immunization with CMO-T-2-BSA was similar to that of hemisuccinate-T-2-BSA. Anti-b-T-2 antibodies had slightly higher cross-reactivity with H-T-2 toxin than did the antibody obtained from rabbits immunized with the conjugate of the a isomer. The relative cross-reactivities of anti-a-CMO-T-2 antibody with T-2, acetyl-T-2, H-T-2, T-2-triol, 3'-OH-T-2, and T-2 tetraol were 1, 4.5, 5.7, 250, 500, and 3,000, respectively. The relative cross-reactivities of anti-b-T-2 antibody with T-2, acetyl-T-2, H-T-2, and T-2 triol were 1, 2, 3, and 488, respectively. Antibodies against b-CMO-DAS showed a high degree of cross-reactivity with monoacetoxyscirpenols (MAS). The relative cross-reactivities of anti-B-DAS antibody with DAS, 4-MAS, 15-MAS, acetyl-deoxynivalenol, T-2-toxin, acetyl-T-2, and neosolaniol were 1, 4, 5, 76, 107, 147, and 266, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Indirect enzyme-linked immunosorbent assay for the mycotoxin zearalenone

A competitive indirect enzyme-linked immunosorbent assay (ELISA) was developed for the detection of zearalenone, an estrogenic mycotoxin. Zearalenone was converted to zearalenone-6'-carboxymethyloxime and conjugated to bovine serum albumin and poly-L-lysine for use as immunogen and solid-phase marker, respectively. Immunization of rabbits with the bovine serum albumin conjugate resulted in zearalenone antibody titers of 20,480 in 11 weeks. A competitive indirect ELISA was conducted by simultaneously incubating zearalenone with zearalenone antiserum over zearalenone-6'-carboxymethyloxime poly-L-lysine solid phase and then determining the bound rabbit immunoglobulin with goat anti-rabbit peroxidase conjugate. Response range for zearalenone in the resulting competition curve was between 1 and 50 ng/ml. Reactivities of this antiserum for alpha-zearalenol, beta-zearalenol, alpha-zearalanol, and beta-zearalanol were, respectively, 50, 12, 6, and 3% of that found for zearalenone. By using the competitive indirect ELISA, zearalenone was detectable in methanol-water extracts of corn, wheat, and pig feed samples.

Preparation and characterization of monoclonal antibodies to the trichothecene mycotoxin T-2

Two mouse immunoglobulin G1 monoclonal antibodies that bind to the trichothecene mycotoxin T-2 were prepared. These antibodies, designated 12C12 and 15H6, had affinities for T-2 of 3.5 X 10(6) and 5.8 X 10(7) liters/mol, respectively. A competitive inhibition enzyme immunoassay that employed these antibodies had a sensitivity for T-2 of 50 ng per assay. Both antibodies bound to the metabolite HT-2 but not to the related trichothecenes monoacetoxyscirpenol, diacetoxyscirpenol, deoxynivalenol, and deoxyverrucarol. Evidence is presented that T-2-protein conjugates inhibit protein synthesis in lymphoid cells and that this apparent immunotoxicity may be due to the release of T-2 from the protein carrier.