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GENETICALLY ENGINEERED CROP PRODUCE IS NOT
POTENTIALLY MORE ALLERGENIC THAN THE COUNTERPARTS
C Kameswara
Rao
Foundation for Biotechnology
Awareness and Education,
ALLERGY
Allergy
is an abnormal state of hypersensitivity of our body to normally innocuous
substances in the food, medicine or the environment. Allergy is neither new nor universal and it
is not an infection that would spread.
Every one of us suffers from intolerance of, or allergic reactions to,
one or the other element in our environment or certain foods or drugs, for a
certain time in our lives. Nevertheless,
there is no single substance that causes allergy in every one of us. Allergies affect millions of people and cause
several thousand deaths globally every year.
Atmospheric
pollen, dust mites, animal dander, insect stings, molds, latex, cosmetics,
fragrances and several others in day to day contact may cause reactions in people.
Walnuts,
pecans, Brazil nuts, cashews, peanuts, soybeans, some varieties of rice and
wheat, cucumbers, mushrooms, fish, shellfish, eggs, milk, mother’s milk, some vegetables
and fruits, etc., as also certain drugs like penicillin and aspirin, may cause
intolerance or even true allergy in certain individuals.
Some
people suddenly develop reactions to foods they have been eating for
decades. In some this happened when they
shifted to a new place of residence, which did not revert when they moved back
to the old place, showing that environmental influences are not necessarily the
cause of the problem. Most allergies
disappear as mysteriously as they appear.
While
there are no reliable data on food allergies in the developing countries, in
the
In
a school class containing several children of diverse genetic backgrounds but
of the same age group, some one or the other would be sensitive to one or the
other food item, though sensitivity to eggs, fish and nuts is common. As school children share their lunch boxes it
is a hard task for parents to decide on what foods they can pack without
risking sensitive reactions from any of their child’s friends in the class
and the problem is worse when they arrange parties for their children’s
friends. The greater and unanticipated risk
is from inadvertent or accidental servings of offending foods.
In
highly sensitive individuals even 1/44,000 of a peanut kernel may threaten
life. Nevertheless, there never was even
a simmer of protest against marketing any of the many conventional foods
established as severely allergenic in certain individuals.
Since
the scenario of food allergies is complex, it would be well to remember the
following generalizations on food
allergy: a) true food allergy is uncommon, but can be very serious,
b) food intolerance, significantly different from food allergy, is quite common
and confused with food allergy, c) the causes of true food allergies differ
from individual to individual and from children to adults, d) the diagnosis of
true food allergies is complex and time consuming and takes into consideration
a detailed history of food habits and reactions, and elimination test to identify
the causative food, and e) the best way to avoid food allergy is to avoid the
offending food while emergency management involves drugs such as
adrenaline.
RISK OF ALLERGY FROM GENETICALLY
ENGINEERED CROPS
Risk
of allergy from genetically engineered (GE) crops and foods is projected as a
major biosafety issue, stemming from baseless allegations,
rooted in two, but now irrelevant cases.
A
gene for the Brazil nut protein was introduced into soybean to increase the
content of methionine, an essential amino acid which
the human body does not synthesize. The
serum from people allergic to Brazil nuts cross-reacted with
extracts of transgenic soybean and not with extracts of its isogenic,
which links the problem to Brazil nut proteins, and not the soybean. Though no one actually developed allergy
by eating the transgenic soybean that was never released for public consumption,
since the transgenic is likely to affect people who are allergenic to Brazil
nuts, Pioneer Hi-Bred International, the developer of the product, did
not proceed with it, an example of self-regulation.
The
Bt Cry 9c
protein in the Aventis Starlink
Bt corn controls the European corn
borer. Cry 9c protein binds to the
pest’s gut at a site different from that of the Cry 1 proteins, and so
would be effective even if the pest develops some resistance to Cry 1 proteins. Cry 9c protein was found to be slightly more
stable in simulated digestion than other Bt proteins, and so it was thought that it might be
allergenic. The United States Department
of Agriculture (USDA) cleared the Cry 9c transgenic corn for use as both food
and feed, but the US Environment Protection Agency (EPA) took a precautionary
measure and approved this corn only for animal feed, as animals do not
generally suffer from food allergies. Bt Cry 9c protein
was never demonstrated to be allergenic.
The US Centers for Disease Control (CDC) tested samples of blood from 17
people claimed to have developed allergenic reactions to Starlink
and found that none of the blood samples
showed cross-reactivity to Cry 9c
protein. The Cry 9c gene is not deployed
in any commercial product now. Since
transgenic products approved as only feed may get into the food products, as
has happened with Starlink Bt Cry 9c corn that appeared in Taco Bell taco shells, no
transgenic is now approved exclusively for use as feed. This shows that the regulatory regime is in
fact vigilant.
Ignoring
the scientific background of food allergies and the fact that the two questioned
transgenes are neither allergenic nor deployed in any
product, these two cases are repeated ad nauseam to make the world
believe that all GE foods are allergenic and to repeatedly demand a blanket ban
on GE foods. In
IMMUNOLOGICAL BASIS OF ALLERGY
The
term allergy is used very loosely and most people seem to have no idea of what
it actually implies. True allergy
involves the immune system. Often food
allergy is not differentiated from other types of adverse non-immunological
reactions to food. Since the public fear
allergy, it is being exploited to whip up fear against GE foods.
Mammalian
systems produce four different classes of immunoglobulin proteins (Ig), the antibodies, in response to the presence of hazardous
alien proteins (called antigens) that enter the body system through food or
pathogens. Vaccines contain antigens (of
cholera or smallpox or other pathogens) and vaccination prepares the body into
producing antibodies against specific pathogens. The antibodies bind to the antigens when
encountered in the body system affording the most valuable means of our body’s
defense.
The
IgM antibodies form first, but both the quantity and
importance of the later formed IgG antibodies is far
greater. IgG
antibodies are the most important body defense system. They bind to the antigens neutralizing them. While IgA
antibodies are specifically involved in the defense of the oral cavity, the
function of IgD antibodies is not very clear.
For
some poorly understood reasons, our immune system also produces another class
of antibodies, the IgE, in response to a few
proteins, which through a complex sequence of cascading biochemical events lead
to true allergic reactions, manifesting as skin rashes, intestinal inflammation,
cramps and diarrhoea or respiratory disorders. This process is anaphylaxis, on record since
2641 BCE, which varies in different individuals from mild and annoying to life
threatening. The active compounds,
triggered by IgE involvement, such as histamine are
mostly inflammatory agents that get into the blood stream making the problem
systemic, when a number of different areas of the body are affected at the same
time. Some similar reactions do not
involve the IgE antibodies (anaphylactoid
reactions), but nonetheless are an important health hazard.
Some
non-protein compounds, such as penicillin and aspirin, may also cause severe reactions,
and these agents called haptens must bind to an
endogenous carrier protein to cause the symptoms.
DIAGNOSIS OF ALLERGY
Identifying
an allergen is a long drawn process.
For each individual a list of suspected sources allergens is drawn and
through a dermal prick test the possibilities are narrowed down by eliminating
those that do not cause any reaction at the test site on the skin. Identification of the offending substance and
demonstrating that it is true allergy involving IgE
antibodies is done through an enzyme linked immunological assay procedure.
TREATMENT OF ALLERGY
The
best way to avoid allergy is to avoid contact with the allergen, identified
basing on each individual’s experience.
Repeated
exposure to small quantities of an allergen over a long period of time results
in higher and higher titres of IgG
antibodies, which in course of time would be adequate to neutralize the
allergen before it had a chance to elicit IgE
antibodies. This is how we overcome
allergies naturally or allergies are clinically treated (immunotherapy). This slow process has worked well in
treating environment based allergies and its success has just been demonstrated
with peanuts on children
who earlier developed strong reactions on eating even very small quantities.
While
there is no assured treatment to cure allergies, anaphylactic reactions are
treated using anti-histamine or steroid drugs.
Both children and adults prone to severe anaphylactic reactions carry a
device to inject a measured quantity of the drug of choice, in case of an
emergency.
PREDICTING ALLERGENIC POTENTIAL OF FOODS
A
protein that is degraded by the gastric enzymes before reaching the intestine
is very unlikely to cause allergy.
This has been the basis to investigate a protein further for its
allergenic potential.
Basing
on voluminous data on the biochemistry of over 200 known allergenic proteins, tests
have been developed to identify potential food allergens. It is now understood that only certain short
stretches of amino acids (the components of proteins) constitute allergenic
sites. These identified sites, not the
whole protein, trigger the production of IgE
antibodies. A consensus document on the biosafety of Bt in
crops (Organization for Economic
Cooperation and Development, July 2007), records that none of the Bt proteins deployed in crops, including
Cry 1Ac, Cry 1Ab, Cry 2Ab and Cry 9c, share similar amino acid sequences with
known proteinaceous food allergens. So far, no allergenic reactions have been
reported during extensive biosafety tests on GE crops
in several countries or on consumption of foods from GE crops for more than a
decade by over 350 million people in
Transgenic
crop varieties are substantially equivalent
to their isogenics, except for the protein coded by
the transgene.
The risk of allergy needs to be considered when a GE food or drug
contains new protein(s), coded by the introduced genes, but not present in the isogenic variety.
For example, the Bt
protein in the Bt potato tuber is
new. Now this protein is known to be
safe for human consumption. Similarly,
the iron carrier protein ferritin, whose gene from
bean or soybean is being introduced into rice to enhance its iron content, is
not allergenic.
If
a gene product in the non-transgenic (isogenic)
variety were an allergen, it would be so in the transgenic as well. Proteins that are normally not allergenic
will not suddenly become allergens in a transgenic plant. Whether a particular protein is allergenic
or not depends more on the consuming individuals rather than on the protein
itself. This makes identification of
allergenic proteins quite tricky. The
remote possibility that Bt
crop foods might sporadically cause allergenic reactions in a few individuals,
in spite of voluminous evidence to the contrary, cannot be the reason to dump
the whole technology which is otherwise beneficial in a number of ways.
It
is near impossible to test for all the antigens and haptens
in a product for the potential of allergy.
Even so, scientists have not been complacent and every new protein in a
transgenic food or feed is examined for allergenicity. In fact, among all the foods we consume, the
GE foods are the most thoroughly tested for allergenicity
and toxicity.
Concern
for public safety is very essential, but spreading fear on political
compulsions, exploiting ignorance, is scare mongering. What we need is a rational attitude with
concern for the larger benefits for the larger sections of the society and not
irrational blanket bans on whole technologies.
No one ever said that the production of any of the large number of
conventional foods known to cause severe allergies in a few people should be
stopped.
February 26, 2009