Introduction have paved the way for largeIntroduction have paved the way for large

Introduction

Recent
advances in the field of r-DNA technology and improved agricultural equipments
have paved the way for large scale cultivation of genetically modified crops. Molecular biology methods are very
precise and aim at introducing only one or, at most, a few
well defined genes; rather than inserting parts of chromosomes as in
traditional plant breeding. To date, over 30 million hectares of transgenic
crops are being grown for human consumption. These are high yielding varieties resistant to pathogen attack and tolerant
to environmental imbalances like drought, cold and salinity1. Transgenes expressed in GM crops encode
of proteins foreign to the wild type varieties. These proteins must be
evaluated for their potency to act as novel allergens, before using GM crops as
feed or fodder. Genetic manipulations have the capacity to alter the genetic composition
of the host plant and may also interfere with the already present natural
allergens2,3. Therefore, prior to the release of GM varieties in market it is essential to
conduct allergenicity and toxicity assessments for the safety of the consumers4. Along with this GM food labeling
should also be made mandatory for all new and existing varieties.

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!


order now

                           
Food
allergy is defined as an adverse health effect arising from a hypersensitivity reaction induced upon
exposure to a particular food allergen that occurs reproducibly on subsequent
exposures. IgE-mediated
food allergic reactions are characterized by excessive activation of mast cells
and basophils, resulting in extreme inflammatory responses like eczema, hives,
allergic rhinitis, asthma and gastrointestinal tract allergies. Food
allergies affect 6% of young children and 3-4% of adults in Western countries5. In general population – self reported
prevalence of food allergy range from 5% in Korea,
3.5% in France
and 22.2% in Australia6. The incidence of food allergy-related anaphylaxis is rising
particularly in children younger than 5 years of age7. Over 90% of
food allergy results from exposure to egg, milk, peanut, tree nut, fish, shellfish, soy and wheat8.
The prevalence of food allergy is influenced by age, culture and dietary habits.

 

Regulatory guidelines for safety assessment
of transgenic proteins  

For any proposed protocol to be
used for testing of GM foods, it is important that it is designed in accordance
with internationally established scientific principles and guidelines developed
by Organization for Economic Cooperation and Development (OECD)9,
Food and Agriculture Organization (FAO) of the United Nations/World Health
Organization (WHO)10 and the Codex Alimentarius Commission11.
First ever food safety assessment report proposed the idea of comparative
approach and has laid the basis for later safety evaluation strategies12.
This approach is based on the concept that the safety of GM foods can be
assessed, to a large extent, by comparison to the conventional counterpart
having a history of safe use, and taking into account both intended and
unintended changes. The objective is to identify new or altered hazards
relative to the conventional counterpart. The basic principle for the
comparative assessment of GM foods – known as the concept of substantial
equivalence – was first established through a Joint FAO/WHO Consultation in 1991
(WHO 1991) and was then further elaborated by the OECD (OECD 1993)9.
Joint FAO/WHO Expert Consultation on ‘Safety Aspects of Genetically Modified
Foods of Plant Origin’ proposed the usefulness of the concept of substantial
equivalence and concluded that “there were presently no alternative
strategies that would provide a better assurance of safety of GM foods than the
appropriate use of the concept of substantial equivalence”. Substantial
equivalence (SE) measures whether the genetically modified variety is safe as
its traditional counterpart, if such counterpart exists or to an earlier
approved variety. SE is evaluated on a scale of three – where one (1) refers to
“complete”, two (2) means “partial” and three (3) stands
for “not at all”. SE (1) implies that the GM food is similar to the
native counterpart; SE (2) explains that GM food is substantially equivalent
except for the inserted gene and SE (3) i.e. ‘not at all’ means that the GM
food is not at all equivalent to its counterpart and thorough evaluation of the
transgenic food is mandatory13. GM and non-GM counterpart used for the comparative studies
should be subjected to similar environmental conditions in order to avoid
genotypic and phenotypic differences not related to the transformation process.
Further, attention should be paid to the choice of comparator, the design of
field trials, and statistical analysis of the generated data in order to obtain
authentic results.

                            A thorough safety assessment
strategy comprises of an integrated, case-by-case approach to be used in the
allergenicity assessment of GM foods14. The safety evaluation
protocols mainly focus on investigating:

The source of the transgene
Sequence homology with reported allergens showing greater than 35%
identity over a window of at least 80 amino acids
Resistance to pepsin digestion in simulated gastric fluid (SGF)
Thermal stability
Serum screening studies
Animal models etc.

With the above safety testing
requirements imposed on GM foods, the risk of introducing a plant variety with
a new allergen or toxin using genetic modification is quite reduced. These
protocols need to be improved with the advancements in the field of
science and technology.

As
per the decision tree proposed
by FAO/WHO, 2001 (Figure 1), weight of evidence approach by Codex, 200311,
and guidelines given by ICMR, 200815
below are mentioned some of the parameters to be assessed for safety testing:

 

Source
of the gene

Initially safety assessment
studies were not considered necessary except in circumstances where the genetic
modification could alter the protein content of the host product significantly. On the other
hand, the current decision-tree approach, advocates the assessment of the
binding of the novel protein with IgE from the blood serum of individuals who
are allergic to the source of the donor genetic material16. Information
relating to the source of the gene used in the genetic modification process assists
in categorizing the source as allergenic, moderately allergic or none. When the genetically modified food contains genes selected
from sources with known allergenic effects, it is assumed that the novel gene
product is allergenic unless proven otherwise17.