3 Recent Advances 61secondary antibody are used and detection is
done by ELISA-chemiluminescence (Moynagh and
Schimmel 2000). Although these tests are 100%
reliable, they can only be done in postmortem brain
tissue.
To improve the sensitivity of current detection
methods and enable live-animal BSE detection,
intense research has been done in developing assays
that take advantage of the infectious capacity of the
PrPSc to convert the normal prion proteins into
pathogenic ones. A team of researchers from Serono
Pharmaceutical Research Institute in Geneva cul-
tured mutated prions in vitro for the first time and
have devised a method to replicate them to high
enough levels to detect the disease at an earlier stage
(Saborio et al. 2001). The technique, called protein
misfolding cyclic amplification (PMCA), is similar
to a PCR reaction, in which amplification of small
amounts of the pathogenic protein in a sample is
achieved through multiple cycles of PrPSc incuba-
tion in the presence of excess PrPc, followed by dis-
ruption of the aggregates through sonication in the
presence of detergents (Fig 3.16). This new tech-
nique has the potential to improve BSE and other
TSE detection methods, to give a better understand-
ing of prion diseases and to help in the search for
drug targets for brain diseases. More recently, re-
searchers from Chronix Biomedical in San Fran-
cisco and the Institute of Veterinary Medicine in
Göttingen, Germany, claim to have developed the
first BSE test that can be performed on live animals
(Urnovitz 2003). This detection method, called the
surrogate marker living test for BSE, is a real-time
PCR test based on in vitro detection of specific RNA
in the bovine serum. It uses blood samples from
cows for the identification of a microvesicle RNA,
and it is considered a surrogate marker test because
it detects blood RNA and not prion proteins. RNA is
found in the blood fraction that contains primarily
microvesicles, and while microvesicles are found in
both healthy and diseased animals, their RNA con-
tents appear to be different. Cattle that show reactiv-
ity to this test should be subjected to a second more
specific test for conclusive diagnosis of mad cow
disease (Urnovitz 2003).
CONCLUSION
Research on transgenic organisms for the food
industry has been intended mostly to benefit produc-
ers. The creation of pathogen-, insect-, and herbi-
cide-resistant transgenic plants have led to increased
productivity and decreased costs of producing many
food crops. Similarly, the introduction of foreign
genes in transgenic salmon enabled it to grow three
times faster then wild-type salmon. The benefits of
the next generation of biotechnology research will
be directed toward consumers and will entail the
creation of designer foods with enhanced character-
istics such as better nutrition, taste, quality, and safe-
ty. A good example of such research is the use of
biotechnology to decrease the amount of saturated
fatty acids in vegetable oils.
Among the many possibilities available in the
field of food biotechnology, future research in
the area of plant genetic engineering is aimed at
increasing the shelf life of fresh fruits and vegeta-
bles, creating plants that produce sweet proteins, de-
veloping caffeine-free coffee and tea, and improving
the flavor of fruits and vegetables. Great progress
has been achieved in using plants as bioreactors for
manufacturing and as a delivery system for vac-
cines. A variety of crops such as tobacco, potato,
tomato, and banana has been used to produce exper-
imental vaccines against infectious diseases. Ad-
vances in genetic engineering will enable the crea-
tion of transgenic plants that produce proteins
essential for the production of pharmaceuticals such
as growth hormones, antigens, antibodies, enzymes,
collagen, and blood proteins.
The applications of genetic engineering in the
food industry are not limited to the manipulation of
plant genomes. Animals and microorganisms also
have been extensively researched to produce better
food products. In the area of animal bioengineering,
the main focus has been on the use of the mammary
gland and the egg as bioreactors in the manufactur-
ing of biopharmaceuticals. So far, the focus of ani-
mal bioengineering research has been directed
toward the benefit of the producers. In the future,
transgenic animal research will be shifted towards
the production of healthier meat products, with
decreased amounts of fat and cholesterol.
Microorganisms, especially yeast, have been vital
to the food processing industry for centuries.
Among their many qualities, yeast plays an impor-
tant role in the production of fermented foods,
enzymes, and proteins. Future research on genetic
engineering of microorganisms may be focused on
the large-scale production of biologically active