Protest organisation Take the Flour Back (TTFB) and and others who support them are basing some of their claims about lack of safety of genetically modified food on a particular study by Canadian workers which claims to detect insect protection protein known as Bt in blood fluids of pregnant women and in human foetuses.
( Maternal and fetal exposure to pesticides associated to genetically modified foods in Eastern Townships of Quebec, Canada, by Aziz Aris, Samuel Leblanc, Reproductive Toxicology 2011).
The same protein Bt is present in many genetically modified insect protected plants such as Bt corn.
Claims about this protein entering the human body are made by TTFB in promotional videos present on the protest website for instance, and have been recently been reported in British newspapers by food writers sympathetic to the claims of TTFB.
The information is spurious.
The scientists reporting finding Bt protein in the human samples (Aris and Leblanc) are detecting only noise in the assay system because they use an invalid assay system (Agdia) intended to test plants, not animals for Bt.
The inconvenient truth about this is described in an earlier paper Paul and others 2007 that demonstrates how to do a valid assay for this Bt protein and also shows what kind of results you get from a valid test with animal samples.
The basic message is that: no detectable Bt protein in GM food enters an animal body from the gut.
Aris and Leblanc 2011 are not aware of this paper by Paul and others as they fail cite it in their reference list but they should because it was published years earlier than their report. They use a commercial assay (Agdia) that is intended for use with plant material on human tissue samples. Paul and others publication shows this is a faulty analysis procedure.
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| Agdia kit for measuring Bt protein in plant and leaf tissue |
Development and validation of a sensitive enzyme immunoassay for surveillance of Cry1Ab toxin in bovine blood plasma of cows fed Bt-maize (MON810)
SUMMARY
The increasing global adoption of genetically modified (GM) plant derivatives in animal feed has provoked a strong demand for an appropriate detection method to evaluate the existence of transgenic protein in animal tissues and animal by-products derived from GM plant fed animals. A highly specific and sensitive sandwich enzyme immunoassay for the surveillance of transgenic Cry1Ab protein from Bt-maize in the blood plasma of cows fed on Bt-maize was developed and validated according to the criteria of EU-Decision 2002/657/EC.
The sandwich assay is based on immuno-affinity purified polyclonal antibody raised against Cry1Ab protein in rabbits. Native and biotinylated forms of this antibody served as capture antibody and detection antibody for the ELISA, respectively. Streptavidin-horseradish peroxidase conjugate and TMB substrate provided the means for enzymatic colour development.
The immunoassay allowed Cry1Ab protein determination in bovine blood plasma in an analytical range of 0.4–100 ngmL-1 with a decision limit (CCalpha) of 1.5 ngmL-1 and detection capability (CCbeta) of 2.3 ngmL-1. Recoveries ranged from 89 to 106% (mean value of 98%) in spiked plasma.
In total, 20 plasma samples from cows (n = 7) fed non-transgenic maize and 24 samples from cows (n = 8) fed transgenic maize (collected before and, after 1 and 2 months of feeding) were investigated for the presence of the Cry1Ab protein. There was no difference amongst both groups (all the samples were below 1.5 ngmL-1; CCalpha). No plasma sample was positive for the presence of the Cry1Ab protein at CCalpha and CCbeta of the assay.
FROM THE INTRODUCTIONA number of ELISA [21–25] and commercial kits (QuantiPlate kit for Cry1Ab/Cry1Ac, Envirologix and DAS ELISA kit for Bt-Cry1Ab/1Ac protein, Agdia) are already existing for the detection and quantification of Cry1Ab protein expressed in GM crops and their by-products. These commercial kits have been also used in various livestock feeding studies on GMO for the surveillance of transgenic protein in the animal tissues and gastrointestinal contents [17–20,26].
Though the commercially available Cry1Ab protein ELISA kits (QuantiPlate kit for bCry1Ab/Cry1Ac, Envirologix and Agdia)were reported to detect Cry1Ab protein down to 1ngmL-1 of spiked blood [26], however, the study missed the most important assay validation part. Further, in another study [19] the same ELISA kit (Envirologix) did not work for the analysis of blood plasma for the surveillance of transgenic protein. Hence, such commercial kits designed for transgenic protein (Cry1Ab or Cry1Ac) quantification in plant materials warrants for a proper assay validation before used for protein analysis in animal systems.Therefore, an assay for the specific detection, including all validation criteria, is required, in particular for the monitoring of transgenic protein in animal products (like blood plasma, milk and meat) derived form GM plant fed animals.
The aim of the present study was: (a) to raise and purify the Cry1Ab toxin specific polyclonal antibody for the development of a sensitive, specific sandwich ELISA for the surveillance of Cry1Ab protein in blood plasma of cows receiving ration supplemented with Bt-maize (MON810) and (b) to validate of this assay as per the requirements of assay validation cited in the guidelines of EU-Decision 2002/657/EC[27]
RESULTS3.4. Application of developed ELISA for the surveillance of Bt-toxin in blood plasma of cows fed transgenic maize (MON810)
In total 45 blood plasma samples (collected before and, after 1 and 2 months of feeding) were analyzed for the presence of the Cry1Ab protein from both, transgenic (n = 8) and non-transgenic (n = 7) ration fed cows. There was no difference amongst both groups (all plasma samples were below 1.5 ngmL-1; CCalpha value). No sample was positive for the presence of the Cry1Ab protein at the decision limit (CCalpha) and detection capability (CCbeta) of the assay (Fig. 5). The absence of transgenic (Cry1Ab) protein from Bt-maize in blood plasma of cows is supported by the other findings reporting the lack of transgenic protein in the tissues (liver, spleen, kidney, lymph nodes and muscles) from livestock that had consumed GM corn [18,19,29]. The reasons for the absence of the Cry1Ab protein from Bt-maize in the blood plasma of cows fed transgenic ration could be the lack of the absorption mechanism involved in the transfer of this toxin from the gut into the blood stream. This could be further supported by the findings reporting the lack of Cry1Ab toxin specific receptors on bovine intestinal epithelium [13,14] and in vivo degradation of trans-genic protein during ruminal digestion [17]. The absence of novel protein in blood plasma of cows fed Bt-maize may consider it as a safe animal feed. The previous findings [16] of a short-term Bt11 maize feeding study on calves demonstrating no negative effects on development of any discernible clinical symptoms, growth rate, hematology, blood biochemistry, and rumen functions further supports Bt-maize as a safe animal feed. In addition the animal performance studies on lactating cows fed GM corn has depicted no changes in animal health, behavior, milk yield and milk composition in comparison to non-GM corn fed cows [30–32]. Though the short-term feeding studies consider GM corn as a safe animal feed, however, before drawing any definitive conclusions a long-term feeding study is warranted.
...This is, to our knowledge, the first immunoassay for a specific detection of Cry1Ab toxin in the blood plasma of cows fed transgenic maize. The assay also fulfills all the validation criteria as prescribed in the guidelines of EU-Decision 2002/657/EC.Though the commercially available Cry1Ab protein ELISA kits (QuantiPlate kit for Cry1Ab/Cry1Ac, Envirologix and Agdia) were reported to detect Cry1Ab protein down to 1ngmL-1 of spiked blood [26], however, the study missed the most important assay validation part. Further, in another study [19] the same ELISA kit (Envirologix) did not work for the analysis of blood plasma for the surveillance of transgenic protein...
Vijay Paul a,., Kerstin Steinke a,b, Heinrich H.D. Meyer a
a Physiology Weihenstephan, Technical University Munich, Weihenstephaner Berg 3,
85350 Freising, Germany
b Bavarian State Research Center for Agriculture, Institute for Animal Nutrition and Feed Management,Prof.-Duerrwaechter-Platz 3, 85586 Poing, Germany
Analytica Chimica Acta 6 0 7 ( 2 0 0 8 ) 106–113
See also earlier GMO Pundit Posts
See next post False claims for the nitty-gritty detail about Aris and Leblanc's errors.
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