Biopharmaceutical crops are plants that have been genetically
modified to express substances with therapeutic properties,
for example viral proteins for vaccines, hormones or antibodies
(Gomez, 2001; Ellstrand, 2003; Ma, 2003). The first recombinant
pharmaceutical proteins derived from plants were
the human growth hormone expressed in tobacco in 1986
(Barta et al. 1986) and the human seroalbumin also from that
crop, and in potato crops in 1990 (Ma et al., 2005). Twenty
years later, the first drugs produced in transgenic plants are
already being marketed. Although some developments use
cell cultures from plants, insects, animals or microorganisms
to express these molecules, others use complete plants of
rice, tobacco and maize, in confined or open field crops, the
latter promising lower costs. Over time, the technology has
improved considerably, improving the economic feasibility
of this application (Ko and Koprowski, 2005; Stewart and
Knight, 2005). Of all these systems, expression in seeds has
turned out to be of enormous utility for accumulating proteins
in a relatively small volume; they do not degrade because the
endosperm conserves the proteins without any need for low
temperatures, which is a great advantage for the production,
for example, of oral vaccines (Han, et al., 2006). Among cereals,
maize, rice and barley are interesting alternatives; but
maize has a greater annual yield, moderately high protein
content in the seed, and a shorter crop cycle, which gives
it greater potential protein yield per hectare overall (Stoger
et al., 2005). Though maize has the disadvantage of being a
cross-pollinating plant, no other cereal grain achieves such
yields (Stoger et al., 2005), which makes it the most used
system of expression; t holds more than 70% of the permits
issued by APHIS from 1991 to 2004 (Elbeheri, 2005).
There are more than 20 firms in the US, Canada and Europe
specialized in these production platforms (Huot, 2003;
Colorado Institute of Public Policy, 2004). The costs are much
lower than those of microbial systems (Elbeheri, 2005). The
economic and technical feasibility combined with the perception
of maize as an industrial raw material have resulted in it
being the most widely used biopharmaceutical crop. Nonetheless,
these criteria do not consider the potential risks for
millions of people who have a maize-based diet. The first risk
is that the grains that contain the compound may pass into
the food production chain in industrial operations because it
is impossible to distinguish them by sight. Careless handling
in industrial processing can occur; it has already happened
with Starlink maize in 2000 and with rice (USDA, 2006), although
they are not biopharmaceuticals. This has happened
in the US, where the rules on biosafety are well established,
though they are not necessarily implemented adequately
(USDA, 2005). This contamination may have a potential negative
effect in the populations that consume these grains: in
Mexico per capita maize consumptions varies from 285 – 480
g daily, and is the source of as much as 40% of protein intake,
given its low cost (Bourges, 2002; FAO, 2006). |
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The potential effect may be disastrous if added to the second
great risk, the risk of genetic flow. This is not a physical
mix of grains, but rather the release of a pharmaceutical
transgene that is inherited in the offspring, where it can endure
for several generations in an open seed exchange system
as one finds in Mexico (Cleveland and Soleri, 2005). The
potential dangers of exposure to recombinant compounds
by this means would affect practically the entire population
of Mexico, particularly those that produce maize for subsistence
or on a semi-commercial basis. The genetic contamination
of maize could be devastating since Mexico is one of
the centers of genetic diversification, and Mexican culture is
tightly bound to this crop. Using maize for the production of
pharmaceuticals and non-edible industrial products, which
also pose health hazards, is the result of a series of decision
in which Mexicans did not participate but which may
directly affect them. These decisions have been made by
companies and policy makers in the more technologically
developed countries where lobbying has led to prohibitions
on developments in animals because public opinion—which
in these countries is often the driving force behind regulatory
changes—considers them more similar to humans, though
containing them is easier (NAS, 2002), and they have been
used for a long time to produce vaccines and serums, antibodies,
etc. This situation has accorded priority to production
in plants worldwide, which is also cheaper. The consortia and
their experts argue that there are no appreciable or verifiable
risks in these crops. Even if the risks are low, which is debatable,
contamination of food crops with pharmaceutical maize
grains would taint the food supply of 100 million Mexicans.
If maize in Mexico is contaminated by genetic flow, it would
not be easy to eliminate, and it would affect 60% of the noncommercial
and commercial productive units in the country,
e.g., production for family consumption in Mexico, which
uses 33% of the area planted in maize, and produces 37% of
domestic maize production (Nadal, 2000; Brush and Chauvet,
2004). This would directly affect the safety of the food base
of millions of Mexicans, not to mention the impact on megadiversity
in a center of origin. Although there are methods of
biological containment of trangenes such as the transformation
of chloroplasts, which are inherited from the mother plant
(Daniell et al., 2005), inducing the expression with substances
that must be added to the crop (Han et al., 2006), and other
systems of genetic containment (Mascia and Flavell, 2004),
no containment system is infallible. In a case such as this,
where there are possibilities of contamination, and where the
consequences would be disastrous for millions of human beings,
one should apply the precautionary principle.
If there is contamination, what would the potential effect be
on human health?
• Plants and animals process proteins in different ways. Biopharmaceuticals
may be perceived by the human body as |