Introduction
Genetically modified (GM) crops are needed to meet the requirement of ever-growing world population. Billions of people worldwide are unable to meet their daily micro-nutritional requirement, and there is need to increase food production by 70% by the year 2050. With the continued increase in population, the major challenge is how to manage the food for everyone. To some extent, GM foods may fulfill this requirement (Delaney, 2015). By the use of latest molecular biology techniques, desirable traits in plants can be introduced by artificial insertion of gene from unrelated species or sometimes from an entirely different kingdom. Development of GM crops began in the late 1980s with the advancement in the biotechnology technique for directly altering the DNA of the genome and rearrangement of DNA by using methods such as electroporation’ or infection with recombinant vectors (e.g., Agrobacterium tumefaciens). These GM crops have new trait(s) introduced in it as compared to native crop (e.g., insects resistance, herbicides and disease resistance, drought tolerance, or improved nutritional content). Conventional plant breeding methods were time-consuming and imprecise. However, the desired trait can be inserted into a plant with higher accuracy using genetic engineering methods (e.g., insertion of Bt gene in corn, which offers insect resistance). This gene, isolated from a bacterium, named Bacillus thuringiensis, produces a protein that can kill the insect larvae. The first GM crops, tomato and soybean, were evaluated for risk assessment and approved by the United States Food and Drug Administration (USFDA). It should be ensured that GM foods are safe before their release into the market. There is a chance that an inserted gene may result in the translation of protein that has the ability to provoke an allergenic response that can sensitize the consumers. Furthermore, it is also possible that inserted gene may elicit allergenic potential by cross-reactivity in an already sensitized population. To save sensitive consumers from unwanted exposure to allergens, appropriate preventive measures should be taken. Humans are exposed to a variety of allergens present in the environment and food. Pollens, fungi, insects, and a variety of food products of animal or plant origin may be harmful to the exposed sensitized group. It is often believed that GM crop/foods may cause additional problems if effective measures are not taken. Also, people should be aware of the ill effects of allergens as no effective medical treatments are currently available for treating this health concern. Therefore, it is essential to assess the allergenic potential of GM crops and food prior to commercialization.
The 20th anniversary (1996–2015) of the commercialization of GM crops concluded recently. Accumulated hectare utilized for irrigation of the GM crops in this time duration exceeded two billion hectares, which is equivalent to twice the total land mass of China or the United States, clearly signifying that biotech crops are putting their roots strongly. The two billion accumulated hectares comprise 1.0 billion hectares of biotech soybean, 0.6 billion hectares of biotech maize, 0.3 billion hectares of biotech cotton, and 0.1 billion hectares of biotech canola. Up to ~18 million farmers benefit from biotech crops in the past 20-year period (1996–2015) and ~90% were small resource-poor farmers. In 2011, commercially cultivated GM crops were Alfalfa (Medicago sativa), Argentine Canola (Brassica napus), Bean (Phaseolus vulgaris), Carnation (Dianthus caryophyllus), Chicory (Cichorium intybus), Cotton (Gossypium hirsutum L.), Creeping Bentgrass (Agrostis stolonifera), Flax or Linseed (Linumusitatissumum L.), Maize (Zea mays L.), Melon (Cucumismelo), Papaya (Carica papaya), Petunia (Petunia), Plum (Prunus domestica), Polish canola (Brassica rapa), Poplar (Populus nigra), Potato (Solanum tuberosum L.), Rice (Oryza sativa L.), Rose (Rosa hybrida), Soybean (Glycine max L.), Squash (Cucurbita pepo), Sugar beet (Beta vulgaris), Sweet pepper (Capsicum annuum), Tobacco (Nicotiana tabacum L.), Tomato (Lycopersicon esculentum), and Wheat (Triticum aestivum). About 45 countries including Argentina, Australia, Bolivia, Brazil, Burkina Faso, Canada, Chile, China, Colombia, Costa Rica, Czech Republic, Egypt, Arab Republic, El Salvador, Germany, Honduras, India, Iran, Islamic Republic, Japan, Korea, Malaysia, Mexico, Myanmar, Netherlands, New Zealand, Pakistan, Paraguay, Philippines, Poland, Portugal, Romania, Russian Federation, Singapore, Slovak Republic, South Africa, Spain, Sweden, Switzerland, Taiwan, Thailand, Turkey, the United Kingdom, the United States of America, and Uruguay are taking their step ahead for the development of various GM crops. In a landmark development, India ranked first in cotton production in the world with 11.6 million hectares planted by 7.7 million small farmers. (source: http://www.isaaa.org/gmapprovaldatabase/default.asp). Herbicide and drought tolerance, insect resistance, improved nutritional characteristics of foods or feeds and altered fatty acid profiles are major choice of developers in the most GM crops, nowadays.
The first international and national provisions for the safety assessment and regulation of GM crop- derived foods were started by Organization for Economic Co-operation and Development (OECD, 1986) and the first regulatory approval of a GM crop had come after approximately one decade (in 1995). In 1996, the International Food Biotechnology Council (IFBC) and the International Life Sciences Institute (ILSI) jointly developed a decision-tree approach (Metcalfe et al., 1996) that is widely accepted by regulatory authorities all over the world. In GM foods, the inserted proteins are needed to be assessed before their insertion and it is very important to ensure that the products of novel genes introduced into GM crop are not harmful. It is also important to ensure that the process of transformation does not cause any unintended change in the characteristics and levels of expression of endogenous allergenic proteins. The safety assessment focuses on the new gene products and whole foods derived from the GM crop. Both intended and potential unintended effects of the genetic modification should be taken into account. The assessment of GM crops involves the steps like characterization of the parent crop, characterization of the donor organisms from which any recombinant DNA sequences are derived, the transformation process and the introduced recombinant DNA sequences, safety assessment of the introduced gene products (proteins as well as metabolites), and food safety assessment of whole food derived from edible part. Earlier, GM brinjal in India was suspended (for an indefinite time period) prior to its intended release due to safety-related issues (Kumar et al., 2011a,b). But recently, issue related to GM crops is gaining attention in India (Padmanaban, 2014; Warrier and Pande, 2016).
During the safety assessment of GM foods, allergenicity is one of the most important issues. Food allergy is an increasing global health concern. It is an immune provocation in susceptible individuals, triggered by certain food proteins, including proteins derived from GM foods. Sensitization develops when a susceptible individual is exposed to an amount of protein sufficient to induce an immune response. Subsequent exposure to the same or similar allergenic protein in sensitized individuals can provoke an adverse reaction. Allergic reactions may be mild and local, but sometimes can be severe, systemic, and fatal. Severe allergic reactions with a rapid onset of symptoms are known as anaphylaxis reactions. The susceptibility of any individual is dependent on several factors, including genetic predisposition and environmental factors.
In food, every protein may not be responsible for provoking immunological reactions but certain proteins that can induce allergic complications are known as allergens. Every allergen is an antigen, but not every antigen is an allergen. In an allergenic protein, certain regions have immune reactive capacity; these regions are known as epitopes. It has been reported that certain biochemical characteristics are shared by many (but not necessarily all) food allergens; one such characteristic is the relative stability and resistant to the denaturation of proteins. Pepsin resistance is thought to be an important property of allergens because when any portion of the protein that remains intact, the chance of an immune response is higher. In the United States, each year about 30,000 people come to hospital emergency departments due to food-induced anaphylaxis, and nearly 200 people die (Sampson, 2003). The recent study in US children population demonstrates the increasing trend in the incidence of food-induced anaphylaxis. Peanuts followed by tree nuts/seeds are implicated as the major contributing factor in this increase (Motosue et al., 2018). In the United Kingdom, millions of people suffer from food-induced allergic reactions. Food and Agriculture Organization (FAO) of the United Nations and World Health Organization (WHO) expert consultation committee on allergenicity of foods derived from biotechnology documented an approach for assessing the allergenic potential of novel proteins in transgenic crops (Codex Alimentarius, 2003).