ISIS Press Release 04/07/06
GM Protein in Ice Cream
Genetically modified fish antifreeze protein is potentially
able to cause inflammation and should not be approved without comprehensive
tests
Prof. Joe Cummins, Dr. Mae-Wan
Ho and Prof. Malcolm Hooper
This report has been submitted to the Food Standards Agency to oppose
approval of Unilever’s application on behalf of the Independent Science Panel
www.indsp.org.uk.
A fully referenced version
of this article is posted on ISIS’ members’ website. Membership details here
Unilever is seeking approval of a genetically modified (GM) (FAQ on genetic engineering) ice-structuring
protein derived from a polar fish, ocean pout, for use in making ice cream smoother
and creamier. The GM protein is produced in transgenic bakers’ yeast.
Ice-structuring, or antifreeze protein protects the ocean pout in freezing waters
by preventing large ice crystals forming; in ice cream and other frozen food
it would have the same effect. Unilever applied to the
Food Standards Agency (FSA) UK
for approval, and its proposal is now open for public comment [1]. Unilever
has sent similar petitions to the United States Food and Drug Administration
(FDA) to obtain the Generally Recognized As Safe (GRAS) status for the
food additive [2] and to Food Standards Australia New Zealand [3]. Both applications
have been approved, which is unfortunate.
The transgenic protein produced in yeast was designated ISP Type III HPLC 12
glyco–ISP. The preparation tested by Unilever contained peptides from yeast
and sugars along with the recombinant protein. Unilever conducted a subchronic
feeding test of the preparation on rats by oral gavage (force feeding) for 3
weeks, as well as a battery of genotoxicity tests that proved to be negative.
A series of tests that included those suggested by the World Health Organisation
for allergy were carried out, along with tests for reactivity with serum obtained
from a few people allergic to fish. The report stressed that the recombinant
protein was identical to protein found in edible fish [1], although that kind
of statement is generally untrue as will be discussed below.
There is voluminous literature on antifreeze glycoproteins, particularly those
from polar fish. There are four main types of glycoproteins each differing significantly
from the others. Type III proteins are around 6500 daltons in size, they form
a beta-sandwich structure and are found only in ocean pout [4]. Although the
antifreeze protein itself is not immunogenic for the ocean pout, there is nevertheless
a strong immune response to the micro ice crystals complex with antifreeze protein
circulating in the fish’s blood, indicating that the complex functions as conventional
antigens for the ocean pout [5].
The GM protein from transgenic yeast is the product of a synthetic approximation
of the pout antifreeze protein gene. The code sequence was altered to facilitate
production in yeast without altering the amino acid sequence. Multiple copies
of the synthetic gene were inserted into the yeast chromosomes to boost the
synthesis of the protein [1].
Production of
proteins in yeast destined for human consumption or therapy is fraught with
the problem of secondary modification of the proteins by glycosylation or
other modifications that result in the human
(or animal) immune system recognizing the yeast modified proteins
as antigens. There has been progress in “humanizing” the glycosylation patterns of proteins produced
in yeast [6, 7]. However, there has been no effort to “humanize” the glycosylation
pattern of the antifreeze protein produced in the yeast strain
used to produce the protein.
Are the cursory studies on allergenicity carried out by Unilever on the GM
protein to be used in ice cream adequate to rule out allergy and other immune
reactions in the tens of millions of people that will consume the ice cream?
It is worth pointing
out that the transgenic protein
is already used in ice cream in the USA, Australia and New Zealand, and
that ice cream has not been labeled,
so any problems resulting from its use may go unrecognized.
We should recall that the transgenic expression of a bean gene in peas turned
it into a strong immunogen, resulting in debilitating even fatal lung inflammation
in mice. That response was related to the glycosylation pattern of the transgenic
protein [8, 9] (“Transgenic pea
that made mice ill" SiS 29). Unilever does not appear to have carried
out the inflammation tests even though there is every indication from the scientific
literature that pouter antifreeze protein is immunologically active.
There is also the question of
latency. Some chronic inflammatory diseases emerge gradually, building up
from an initial response that is small and clinically variable or insignificant
(asymptomatic) [10]. But there is a potential cascade effect that when triggered,
will lead to autoimmune effects that could affect any organ. Without long
term testing, we could be letting off an immunological time bomb. Tests for
inflammatory effects must be done in both young and older animals will full
analysis of inflammatory cytokines, antibodies and related molecules. Tests
in young animals are particularly important as ice cream is consumed from
the earliest age when there are crucial development processes occurring.
In conclusion, contrary to the claims of Unilever, there is no evidence that
the transgenic ice- structuring protein is identical to the protein produced
in pouter fish. The transgenic protein appears to have the glycosylation pattern
of yeast, making that protein a unique antigen. Even though allergenicity was
studied in a cursory way, there is clear precedent for studying inflammation
comprehensively in the long term in both young and older animals before exposing
the European public to the transgenic ice cream.
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