Recombinant proteins in newly developed foods: identification of allergenic activity

Public health issues related with the consumption of food obtained from genetically modified organisms

Genetically Modified Organisms (GMOs) are a fact of modern agriculture and a major field of discussion in biotechnology. As science incessantly achieves innovative and unexpected breakthroughs, new medical, political, ethical and religious debates arise over the production and consumption of transgenic organisms. Despite no described medical condition being directly associated with a diet including approved GM crops in large exposed populations such as 300,000,000 Americans and a billion Chinese, public opinion seems to look at this new technology with either growing concern or even disapproval. It is generally recognized that a high level of vigilance is necessary and highly desirable, but it should also be considered that GMOs are a promising new challenge for the III Millennium societies, with remarkable impact on many disciplines and fields related to biotechnology. To acquire a basic knowledge on GMO production, GM-food consumption, GMO interaction with humans and environment is of primary importance for risk assessment. It requires availability of clear data and results from rigorous experiments. This review will focus on public health risks related with a GMO-containing diet. The objective is to summarize state of the art research, provide fundamental technical information, point out problems and perspectives, and make available essential tools for further research. Are GMO based industries and GMO-derived foods safe to human health? Can we consider both social, ethical and public health issues by means of a constant and effective monitoring of the food chain and by a clear, informative labeling of the products? Which are the so far characterized or alleged hazards of GMOs? And, most importantly, are these hazards actual, potential or merely contrived? Several questions remain open; answers and solutions belong to science, to politics and to the personal opinion of each social subject.

Molecular characterization of recombinant T1, a non-allergenic periwinkle (Catharanthus roseus) protein, with sequence similarity to the Bet v 1 plant allergen family

More than 25% of the population suffer from Type I allergy, an IgE-mediated hypersensitivity disease. Allergens with homology to the major birch ( Betula verrucosa ) pollen allergen, Bet v 1, belong to the most potent elicitors of IgE-mediated allergies. T1, a cytokinin-inducible cytoplasmic periwinkle ( Catharanthus roseus ) protein, with significant sequence similarity to members of the Bet v 1 plant allergen family, was expressed in Escherichia coli. Recombinant T1 (rT1) did not react with IgE antibodies from allergic patients, and failed to induce basophil histamine release and immediate-type skin reactions in Bet v 1-allergic patients. Antibodies raised against purified rT1 could be used for in situ localization of natural T1 by immunogold electron microscopy, but did not cross-react with most of the Bet v 1-related allergens. CD analysis showed significant differences regarding secondary structure and thermal denaturation behaviour between rT1 and recombinant Bet v 1, suggesting that these structural differences are responsible for the different allergenicity of the proteins. T1 represents a non-allergenic member of the Bet v 1 family that may be used to study structural requirements of allergenicity and to engineer hypo-allergenic plants by replacing Bet v 1-related allergens for primary prevention of allergy.

IgE-mediated allergy to corn: a 50 kDa protein, belonging to the Reduced Soluble Proteins, is a major allergen

BACKGROUND

Although corn is often cited as an allergenic food, very few studies have been devoted to the identification of corn allergens and corn allergy has been rarely confirmed by double-blind, placebo-controlled food challenge (DBPCFC). Recently, Pastorello et al. (1) identified some salt-soluble IgE-binding proteins of corn flour as potential allergens. One of these, corresponding to corn Lipid Transfer Protein (LTP), appeared to be the major one. The aim of this study was to verify the clinical significance of the skin prick test (SPT) and CAP-FEIA CAP-System IgE fluozoenzyme immunosorbent assay (Pharmacia Diagnostic, Uppsala, Sweden) positivities to corn and to identify the presence of IgE-binding proteins in the corn flour salt-insoluble protein fractions (comprising up to 96% of the total protein) using sera of patients with DBPCFC-documented food allergy to corn. In addition the effect of cooking and proteolytic digestion on the corn allergens was investigated.

METHODS

Sixteen subjects with SPT and CAP-FEIA positivities to corn flour were examined. Only six of them complained of suffering from urticaria and/or other symptoms after ingestion of corn-based foods. The patients were food challenged with cooked corn flour (polenta). IgE-binding proteins were detected by immunoblotting. The digestibility of the IgE-binding proteins was examined during a pepsin attack followed by a pancreatin digestion performed on a cooked corn flour sample.

RESULTS

Oral challenge was positive only for six patients with symptoms after ingestion of corn. A 50 kDa protein, belonging to the corn Reduced Soluble Protein (RSP) fraction was recognized by the serum IgE of all the DBPCFC-positive subjects and resulted to be resistant to both heating and peptic/pancreatic digestion. SPT with the purified RSP fraction gave positive results for all of the DBPCFC-positive patients examined.

CONCLUSIONS

SPT and CAP-FEIA positivities to corn flour had no clinical significance for most of the patients and food allergy to corn has to be proved by DBPCFC. A salt-unextractable protein of 50 kDa, belonging to the RSP fraction, represents a potential allergen in food hypersensitivity to corn because of its stability to cooking and digestion.

Health and safety issues pertaining to genetically modified foods

Genetic modification involves the insertion of genes from other organisms (within or between species) into host cells to select for desirable qualities. Potential benefits of GM foods include increased nutritional value; reduced allergenicity; pest and disease-resistance; and enhanced processing value. Possible detrimental outcomes include producing foods with novel toxins, allergens or reduced nutritional value, and development of antibiotic resistance or herbicide-resistant weeds. Benefits to individuals or populations need to be weighed against adverse health and environmental risks, and may differ between developing and Westernised countries. Whether testing and monitoring should exceed requirements for conventional foods is under debate. While not necessarily scientifically justifiable, consumer concerns have resulted in Australian and New Zealand requirements to label foods containing GM-produced proteins. Dissatisfied consumer advocacy groups are calling for all foods involving GM technology to be labelled, irrelevant of whether the final product contains novel protein. Goals to improve the quantity, quality and safety of foods are laudable; however, the primary aim of the bio-food industry is financial gain. GM foods may be as safe as conventional foods but public distrust runs high. It is important that discussion is informed by science and that claims of both benefits and risks are evidence-based, to ensure that the process is driven neither by the vested interest of the bio-technical multinational companies on the one hand, nor ill-informed public fears on the other.

Allergenicity test of genetically modified soybean in Sprague Dawley rats

Allergenicity of genetically-modified (GM) soybean was evaluated in male Sprague Dawley rats. To confirm the GM soybean used in this study, the polymerase chain reaction (PCR) was performed using the chromosomal DNA of soybeans. The PCR result provided the clear discrimination of genetically-modified (GM) soybeans. To evaluate the allergenicity of GM soybean and non-GM control one, the soybean homogenate was sensitized subcutaneously 3 times a week for 3 weeks. The doses of soybean were 0, 2 and 20 mg/kg in the protein basis. A week after the last sensitization, antisera were recovered from individual animals. When the sera were injected intradermally on the clipped back of unsensitized rats with various dilutions, followed by a challenge with 20 mg/kg of soybean homogenate containing 1% Evans blue, no sign of passive cutaneous anaphylaxis reaction was detected. In addition, when the sera were treated in the cultures of peritoneal mast cells, the increase of histamine release by anti-(GM soybean) sera was not observed when compared to that by anti-(non-GM soybean) sera. The present results indicate that the GM soybean might not act as a strong allergen in male Sprague Dawley rats.