On 2014 Feb 06, Anastasia L Bodnar commented:

This comment focuses on the claim by Aris and Leblanc that CryAb1 toxin was detected. In short, they used an incorrect method and an incorrect standard.

The ELISA kit used by Aris and Leblanc to detect Bt was made by a company called Agdia (as described in section 2.4. of the paper). The kit was created and tested to detect Bt in plant tissues (Agdia doesn’t make any kits for animal tissues). This is potentially a problem because a kit that is not tested on mammalian tissues might cross-react with proteins found in mammals that aren’t found in plants, giving a false positive result. ELISA methods have been developed for Cry proteins in mammalian blood, but these methods have had varying success.

German researchers developed an ELISA method for cows’ blood, which was able to detect Cry proteins in blood that was spiked with the protein. They did not find any significant difference between cows that had been fed Bt and conventional maize for a two month period, and all values detected in all cows’ blood were less than 1.5 ng/mL. Paul V, 2008

Aris and Leblanc did cite a paper that showed fragments and intact Bt protein could be detected with ELISA in the gastrointestinal tract (not in blood). Aris and Leblanc did not mention that the researchers found that Bt was probably digested in cattle, and suggested that a different method besides ELISA should be used to confirm presence of Cry protein. Lutz B, 2005

Aris and Leblanc also cited a paper that used ELISA to detect Cry protein in pigs. ELISA, immunochromatography, and immunoblot were sucessful in detecting Cry protein fragments in the gastrointestinal tract. Aris and Leblanc did not mention that the researchers did not detect any Cry protein in blood with any of these methods. Chowdhury EH, 2003

In addition to using an incorrect method to detect Cry proteins in blood, Aris and Leblanc also used an incorrect standard. Aris and LeBlanc created Cry protein solutions of 0.1 to 10 ng/mL. In Table 2, they report that a a range of 0 to 1.50 ng/mL was detected in maternal blood and 0 to 0.14 was detected in fetal cord blood. The mean and SD for maternal was 0.19 ng/mL ± 0.30 and for fetal was 0.04 ± 0.04 ng/mL. Ideally, test values will be in the middle of a standard curve. Any values outside or at the edges of of the standard curve may be false positives. Aris and Leblanc could have confirmed their results with a Western blot or any number of other methods, but they did not.

On 2014 Feb 06, Anastasia L Bodnar commented:

This comment focuses on the claim by Aris and Leblanc that CryAb1 toxin was detected. In short, they used an incorrect method and an incorrect standard.

The ELISA kit used by Aris and Leblanc to detect Bt was made by a company called Agdia (as described in section 2.4. of the paper). The kit was created and tested to detect Bt in plant tissues (Agdia doesn’t make any kits for animal tissues). This is potentially a problem because a kit that is not tested on mammalian tissues might cross-react with proteins found in mammals that aren’t found in plants, giving a false positive result. ELISA methods have been developed for Cry proteins in mammalian blood, but these methods have had varying success.

German researchers developed an ELISA method for cows’ blood, which was able to detect Cry proteins in blood that was spiked with the protein. They did not find any significant difference between cows that had been fed Bt and conventional maize for a two month period, and all values detected in all cows’ blood were less than 1.5 ng/mL. Paul V, 2008

Aris and Leblanc did cite a paper that showed fragments and intact Bt protein could be detected with ELISA in the gastrointestinal tract (not in blood). Aris and Leblanc did not mention that the researchers found that Bt was probably digested in cattle, and suggested that a different method besides ELISA should be used to confirm presence of Cry protein. Lutz B, 2005

Aris and Leblanc also cited a paper that used ELISA to detect Cry protein in pigs. ELISA, immunochromatography, and immunoblot were sucessful in detecting Cry protein fragments in the gastrointestinal tract. Aris and Leblanc did not mention that the researchers did not detect any Cry protein in blood with any of these methods. Chowdhury EH, 2003

In addition to using an incorrect method to detect Cry proteins in blood, Aris and Leblanc also used an incorrect standard. Aris and LeBlanc created Cry protein solutions of 0.1 to 10 ng/mL. In Table 2, they report that a a range of 0 to 1.50 ng/mL was detected in maternal blood and 0 to 0.14 was detected in fetal cord blood. The mean and SD for maternal was 0.19 ng/mL ± 0.30 and for fetal was 0.04 ± 0.04 ng/mL. Ideally, test values will be in the middle of a standard curve. Any values outside or at the edges of of the standard curve may be false positives. Aris and Leblanc could have confirmed their results with a Western blot or any number of other methods, but they did not.