ISIS Press Release 28/11/05
Immune Reactions to Transgenic Protein Serious.
Independent Scientists Demand A Ban on GM Food & Feed while All GM Crops Are Tested.
The following memo and report were sent to international and national regulators on behalf of the Independent Science Panel.
Immunological assessments carried out for the first time on a transgenic protein revealed that post-translational processing subsequent to gene transfer into an alien species introduced new antigenicities that turned a previously harmless protein into a strong immunogen. In addition, the transgenic protein promoted immune reactions against multiple other proteins in the diet. The detailed findings are reviewed in the report below.
As practically all the transgenic proteins involve cross-species gene transfer, they will be subjected to different post-translational processing, and hence they too, will have the potential to become immunogenic. And yet, none of the transgenic proteins that have been commercially approved has been tested. This omission is a most serious public health issue.
We call on you to impose an immediate ban on all GM food and feed until proper assessment on the immunogenicity of all the transgenic proteins has been carried out.
*The ISP, launched 10 May 2003 at a public conference in London, UK, consists of dozens of prominent scientists from 11 countries spanning the disciplines of agroecology, agronomy, biomathematics, botany, chemical medicine, ecology, epidemiology, histopathology, microbial ecology, molecular genetics, nutritional biochemistry, physiology, toxicology and virology (http://www.indsp.org/ISPMembers.php)
Transgenic Pea that Made Mice Ill Raises serious safety concerns on transgenic proteins in general that must be addressed while a ban on all GM food and feed is imposed. Dr. Mae-Wan Ho
Ten-year project down the drain but are the right lessons learned?
A ten-year project at CSIRO (Commonwealth Scientific and Industrial Research Organization) in Canberra Australia bit the dust when peas modified to resist insects caused inflammation in the lungs of mice . The GM peas will be destroyed, said Gene Technology Regulator Sue Meeks.
The gene coding for the protein, a-amylase inhibitor-1 (aA1) in the common bean (Phaseolus vulgaris L. cv. Tendergreen), was inserted into pea (Pisum sativum L.) to make the pea-plants resistant to attack from weevils.
Dr. T.J. Higgins, deputy chief of CSIRO Plant Industry and co-author of the scientific paper reporting the results remarked it is only the second time in the world that a GM project has been abandoned after a gene transfer from one crop to another, and that it demonstrated the effectiveness of strict regulations on research into GM crops.
Greenpeace campaigner Jeremy Tager said: “It just shows the failure of the science in relation to this gene product.”
Director of GeneEthics Network Bob Phelps referred to the project as a “waste of public money” and highlights the growing concern worldwide about the health impacts of all GM foods.
There are indeed important lessons to be learned from the scientific findings , which raise serious safety concerns over transgenic proteins in general.
Different processing of transgenic protein
The researchers found that the transgenic protein was processed differently and provoked immune reactions not exhibited by the native protein (see later).
Transgenic aA1 protein was compared with the non-transgenic protein on Western blot, a technique that separates different forms of the protein arising from post-translational processing. Previous studies showed that the native polypeptide in bean is cleaved into two chains, a and b, both of which are glycosylated (carbohydrate chains added), and with one or more amino acids removed from the tail end. This results in major forms of the a- and b-chains with molecular masses 11 646 Da and 17 319 Da respectively, together with minor forms containing alternative carbohydrate chains. The transgene in pea yielded a- and b-chains with molecular masses in the11 000 – 18 000 Da region, but with a banding pattern different from the native protein. More detailed comparisons on mass spectroscopy showed that the transgenic a-chain was less heavily glycosylated; and a form with two fewer mannose residues (11 322 Da) was the dominant in transgenic pea, but the least abundant in bean. The b-chain in the transgenic protein also showed a number of other bands besides the major and minor forms present in the native protein.
Immune reactions to transgenic protein
Mice were given about 25mg of seed meal in suspension, containing transgenic pea, nontransgenic pea, or bean, twice a week for 4 weeks. Seven days after the final feeding, the mice were subcutaneously injected in the footpad with the purified protein antigens: native or transgenic aA1, and the swelling induced in the footpad assessed 24 h later.
In a second experiment, the mice were fed seed meal suspensions as before, and seven and nine days after the final meal, purified transgenic aA1 or buffered saline was introduced into the trachea, and inflammation response was measured in the lungs 24 h later.
The results showed that mice fed on non-transgenic pea or bean showed no inflammation response in the footpad or in the lungs, indicating normal immune tolerance to common food.
Mice fed with transgenic pea, however, showed aA1-specific IgG antibodies at two weeks, rising to significant levels after 4 weeks. There was significant swelling of the footpad, or delayed type hypersensitive (DTH) response, when purified aA1 was injected. Similarly, introducing the antigens into the trachea gave an inflammation response in the lungs.
As a control for the general effect of genetic modification, the footpad challenge experiment was repeated with material from two other GM plants, lupin expressing sunflower seed albumin (SSA) and chickpeas expressing aA1. In contrast to transgenic pea, mice fed transgenic lupin or transgenic chickpea did not give DTH response. This shows that the response to transgenic pea was specific.
The peribronchial lymph nodes of the mice were tested for their response to transgenic aA1. Only the lymph nodes of mice fed transgenic peas responded by producing the inflammation cytokines (cell signalling factors) when challenged with transgenic aA1.
Transgenic protein promotes reactions to other proteins
In order to test if the transgenic protein promotes immune reactions to other proteins in the diet, mice were fed purified transgenic or native aA1, or transgenic aA1 with or without ovalbumin three times a week for 2 weeks. One week following feeding, purified ovalbumin or buffered saline were introduced into the trachea of the mice, and inflammation response in the lungs was assessed as before.
Neither ovalbumin alone, nor ovalbumin in combination with native aA1 caused any inflammation response in the footpad or lungs when the mice were challenged with ovalbumin. However, consumption of transgenic aA1 and ovalbumin together promoted a strong ovalbumin-specific antibody response and predisposed the mice to inflammation when challenged with ovalbumin in both the footpad and the trachea. This suggests that transgenic aA1 did promote reactions to other proteins. In confirmation of that, levels of antigen-specific IgG against other proteins such as pea globulins, lectin, and vicilin-4 were also significantly higher in the serum of mice fed transgenic pea than mice fed non-transgenic pea.
Wider implications on the safety of transgenic proteins that must be addressed
The transgenic pea involved gene transfer between plant species, and is generally thought to be much safer compared with the cross-kingdom gene transfer – bacteria to plant – involved in the GM food crops that now cover tens of millions of hectares worldwide.
A harmless bean protein expressed in transgenic pea caused inflammation in mice, and research showed that the most likely reason is because the protein is processed differently in peas. Such post-translational processing of proteins is well known to be species-specific, and as genetic modification almost invariably involves cross-species transfer of proteins, one must expect transgenic proteins to differ structurally from the native proteins as a matter of course. Are they also likely to provoke immune reactions as a result?
It would not happen in every case, as the researchers have found that neither transgenic lupin sunflower seed albumin, nor transgenic chickpea aA1 gave the same results as transgenic pea aA1. But how frequently could it happen?
“Currently, we do not know the frequency at which alterations in structure and immunogenicity of transgenically expressed proteins occur or whether this is unique to transgenically expressed aA1.” The researchers admitted.
Furthermore, when consumed with other proteins, the transgenic pea protein promoted immunological ‘cross-priming’ against those proteins, so that the mice developed specific immunological reactions to them as well. In other words, the transgenic protein can provoke generalised immune response to multiple proteins in the diet, whether transgenic or not.
The previous instance of a GM project being abandoned was the transfer of a Brazil nut allergen into soya , and it involved a known allergen. The present case involves a protein that has all the appearance of being harmless.
As yet, no other GM crop, especially those already out there in the fields and in our food and feed, has been tested in this way. This must now be done. Meanwhile, there must be a ban imposed on all GM food and feed.
1. “GM crops scrapped as mice made ill”, Selina Mitchell and Leigh Dayton, The Australian, 18 November 2005. http://www.theaustralian.news.com.au/common/story_page/0,5744,17283002%255E2702,00.html
Prescott VE, Campbell PM, Moore A, Mattes J, Rothenberg ME, Foster PS, Higgins TJV and Hogan SP. Transgenic expression of bean a-amylase inhibitor in peas results in altered structure and immunogenicity. J Agricultural and Food Chemistry 2005, 53, 9023-30.
Nordlee JA, Taylor SL, Townsend JA, Thomas LA & Bush RK. Identification of a brazil-nut allergen in transgenic soybeans. The New England Journal of Medicine 1996, March14, 688-728.
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