Friday, July 12, 2013

Allergic reactions to GMOs (or not)

I continue the review of the Institute for Responsible Technology's (IRT) claims of the health impact of GMOs. In my last post, I left off with a promise to look into whether mice fed Bt have powerful immune responses against the toxin. As a refresher, companies that use Bt claim that it only affects insects (please see my last post or Wikipedia for more information on Bt. If you choose to use Wikipedia, please think about giving a donation to the organization).

So, there were 3 papers linked to this specific claim about the health impact of GMOs. Since they were all written by the same authors and had similar titles, I picked the latest one to read, but also flipped through an older paper. The paper was published in 2000 and is very immunology heavy. I'll be honest. I struggled to keep my eyes open and have a whole new level of respect for immunology researchers. But I think I got the gist of it. The authors prepared different forms of the toxin, administered it to mice, and saw that the mice began making antibodies against the toxin. Although I don't know if the response qualified as "powerful" or not, there definitely seemed to be a response of some sort. A few things struck me as odd: one, despite what is implied by the IRT's webpage, the authors didn't make an immediate link between their conclusions and GMOs. Also, the 2000 paper and the older paper were pretty similar, but the 1999 paper didn't mention GMOs at all and they stated that the reason for looking into the antibody responses was to determine if the toxin could be used to produce a vaccine. So the second part can easily be explained: often times, after you finish writing a paper, you add a few interesting facts that are loosely related to your findings in order to make your paper "sexier". I've been guilty of this myself. I clearly remember writing "human chromosome 7 has been associated with numerous parent of origin disorders, including autism". Why would I throw in "including autism"? Because it made my paper seem more interesting, even if it had nothing to do with autism (which it didn't). So it seemed to me that the GM link was thrown in afterwards. But I still felt like I needed to understand if the paper was conclusive evidence of an immune response to Bt in a mammal. As a reminder, we're talking about Bt here, whether it's within the context of a GMO or not.

From what I understood, the study seemed OK: they had controls, they tried two different ways of getting the purified toxin into the mice, and they had done very basic stats showing an immune response. But they didn't come to the conclusions that IRT wanted me to get to. So, I started to look for more recent papers that had cited the paper above to find out if the results had ever been replicated. I found a paper published 10 years later in PLoS (2010). This paper actually looked at the immune impact towards the purified protein and as well as the GMO corn. I started reading it and... snore... another immunology paper. Sheesh... I'm never going to finish this blog post.

The 2010 paper was much more thorough, looked at many additional variables, and was actually about Bt GM corn. As controls, they used proteins with various degrees of allergenicity. I was fascinated to learn that the first paper I had read (the one cited by the IRT) hadn't studied the Bt toxin found in GM corn (which confirmed my theory that the GM-tie was thrown in). As I noted in my previous post, there are various strains of Bt, and each one has different properties. However, the authors note that the toxins produced are similar enough that if you have an immune response to one, you should have an immune response to all. And they hadn't gotten the immune response seen in the first paper. The authors suggest that the first paper had generated a contaminated protein due to their methodology.

They go on to state that although they hadn't seen the specific immune reponse documented in the first paper, they had seen a different immune response. Mammals produce different types of antibodies (that much I DO remember from Immunology 301), so you can have a specific category of antibodies react against a substance. They go on to state that the antibody response that they saw against the Bt toxin, was the same response seen against their negative-control. They conclude that the strain of mice used in their study just seems to be pretty sensitive to protein extracts. Basically, they had zilch.

Finally, they looked at the different immune responses to GM corn vs standard corn. Again, zilch. 

They also provide their funding list. No agribusinesses were listed.

So, I have learned a few things here:
  1. Any future papers that I read where immune responses are examined in mice, I should pay close attention to the strain used. Mice strains seem to be scientists' undoing, as previously reported.
  2. I should also pay attention to the type of Bt toxin examined, since it may not be the same one used in GMOs
  3. I have yet to confirm a single health impact from the IRT's webpage, who proclaims itself as being "The most comprehensive source of GMO health risk information on the web." I'll continue next week with the next reference.
  4. I didn't know that there were so many papers that had examined the issue of allergies against GMO. I guess that they're ignored since the results are not controversial.
  5. I need to take a course in immunology. Or hire an immunology grad-student. The latter is probably cheaper.
To wrap up here, I wanted to add a more personal note. The spouse asked me the other day how I can be so calm and collected when I read a sentence such as "GM corn causes cancer". To tell you the truth, there are often times when I'm not. But I always have to tell myself to think with my mind and not my emotions, even though I often fail. I'm trying to go about this with my feet firmly planted on our organic lawn and let science be my bioluminescent flashlight through this murky controversy (that reminds me of the bioluminescent fish that Sheldon made).


1 comment:

Note: Only a member of this blog may post a comment.