Genetically engineered foods: a threat to human health? Encontro de Investigadores, Ciência 2009 Rita Batista

Which GM foods are under commercialization in EU? 5 plant species approved for human consumption: Soya (drinks, tofu, oil, flour, lecitin…) Maize (oil, flour, syrup, sweet maize, cereals, etc…) Oilseed rape (oil) Cotton (oil) 2 types of genes introduced : Insect resistance (Cry genes) Herbicide tolerance/resistance (CP4EPSPS and PAT genes) Sugar beet (sugar)

What are the major health concerns of GE plants ?

Putative horizontal transfer Transfer of antibiotic marker genes to gastrointestinal bacteria or bacteria we eat together with food Natural prevalence of antibiotic resistance in soil and enteric bacteria DNA breakdown Recipient bacteria → take up and integrate DNA into their genome DNA → associated with appropriate regulatory sequences Transferred trait → confer competitive advantage Despite: The concern persists: Food processing Passage through gastrointestinal tract Bacterial restriction enzymes No scientific evidence for uptake ingested DNA by gastrointestinal bacteria as consequence of food consumption

Putative transgene horizontal transfer Another concern: Inactivation of orally administered antibiotic by the resistance markers Directly By integration of antibiotic resistance marker genes in gut epithelial cells most common ARM gene Rapidly inactivated by stomach acid and degraded by digestive enzymes From E. coli → ubiquitous in nature Confers resistance to antibiotics with no therapeutic relevance Argument of a putative increase of antibiotic resistance by gastrointestinal bacteria due to nptII HT is unacceptable nptII

Putative transgene horizontal transfer Inactivation of orally administered antibiotic by marker gene product By integration of antibiotic resistance marker genes in gut epithelial cells Gastrointestinal epithelial cells do not divide and have a short life span (7 days) Integration of antibiotic resistance marker genes in gut epithelial cells would not compromise public health

No expert panel has ever identified a significant risk associated with antibiotic resistance marker genes use Despite: Putative transgene horizontal transfer Efforts aimed to produce ARM free GM plant products Removal of these genes after transgenic plant selection Use of intron-containing marker genes Use of antibiotic resistance plant genes

Consumption of “foreign” DNA Consumption of DNA from foreign species (i.e. viruses or bacteria) in the genome of a food plant Bacteria and viruses always present in our food All DNAs are chemically equivalent Potential risk of DNA consumption would not depend on the species of origin → only on its sequence

Consumption of “foreign” DNA CaMV35Spro lead to inappropriate over expression of genes in species to which it is transferred? Consumption of any CaMV-infected vegetables result in ingestion of far more copies of 35S pro than consumption of transgenic plants carrying this promoter Several barriers would limit potential interaction of CaMV35Spro with human DNA CaMV is present in 10% cabbages and cauliflowers CaMV infects most plant cells and produces 105 particle per cell (each with one copy of 19Spro and 35Spro)

Unexpected alterations in nutritional composition GE cause unexpected and/or undesired effects in nutritional composition of final product? Concern also valid for plants obtained through conventional breeding techniques GM foods nutritional and biochemical characteristics are tested before its commercialization

Allergenicity/ toxicity To date, no experimental evidence has supported a higher degree of toxicity/ allergenicity of approved GE foods as compared to their non-transgenic counterparts Products of introduced genes represent allergens and/or toxins or induce unintended effects on plant metabolism that lead to upregulated expression of allergens and/or toxins? Studies claiming for higher toxicity/ allergenicity of GE foods tainted with important flaws Two allergenicity problems promptly detected by regulatory systems Pioneer Hi-Bred GE soybean variety Aventis Starlink GE maize variety

What are our major research interests in this issue? Are GM foods more allergenic than conventional? Does genetic engineering provoke more alterations than other modern conventional breeding techniques? How important is natural plant variability in the context of the food safety assessment process? Develop highthrouput methodologies to check for the safety of genetically modified foods Contribute to fill the lack of scientific data

What have been the major conclusions obtained so far? None of the tested products have presented increased allergenicity after genetic modification Transcriptome alterations due to genetic modification were < for transgenic vs mutagenized plants Safety assessment of improved plant varieties should be carried out on a case-by-case basis and not simply restricted to foods obtained through genetic engineering Probability of an individual having eaten GM food near 100%

The beginning…