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[Duurzaamlijst] food and mouth & transgenic edible vaccines

On 6 Mar 2001:
Prof. Joe Cummins
e-mail: jcummins@uwo.ca

"Foot and mouth disease transgenic edible vaccines: Solution or
problem" The recent outbreak of foot and mouth virus (FMDV) has
many to wonder whether or not there was a connection between the
outbreak and experiments in genetic technology. There have been
experiments done using transgenic constructions to construct
vaccines to treat the disease. Field testing such constructions does
not fall under regulations governing transgenic crops used for food.
It is worth enquiring of the governments of countries about the
studies, if any, being undertaken. The transgenic vaccines reported
have been transgenic alfalfa with foot and mouth virus structural
proteins (Wigdorovitz et al a 1999), plants infected with tobacco
mosaic virus genetically altered with FMDV structural protein
(Wigdorovitz et al b1999) or bacterial plasmids containing genes for
FMDV protein (Wong et al 2000). Use of genetically modified (GM)
organisms to deliver edible vaccines has proven effective in
protecting farm animals but the procedure is not without drawbacks.
One complication with oral vaccines is called "oral tolerance". 
antigens are taken up in food repeatedly the antigen may suppress
production of antibody. In autoimmune diseases such as arthritis,
diabetes and multiple sclerosis antigens are produced in target
tissues leading to disease. When quantities of the target antigen ,
such as collagen in arthritis, is fed the autoimmune disease is
suppressed and many patients experience relief. Indeed, antigens for
autoimmune disease are being introduced into crop plants to treat the
symptoms of autoimmune disease. However, oral vaccines in regular food
supplies may suppress immunity to the disease normally protected by
the vaccine(Langridge 2000, Weiner 1997). Measures must be taken to
prevent the spread of food vaccines to the general food supply.
Transplacental exposure to the edible vaccine may cause the fetus to
be tolerant to the virus to the extent that the animal may become a
carrier of the virus without showing symptoms ( an example of a
carrier might be "typhoid Mary" of elementary texts). The crops
modified to be used as edible vaccines should be scrupulously
maintained for that purpose alone. Recently corn modified as an edible
vaccine for a swine virus was promoted by the company inventing it. It
was promised that the GM corn would be grown under "rigorously
controlled conditions and used only for the expressed purpose of
vaccine production"("Edible Vaccine Success" In Brief Nature
Biotechnology 18,367,2000). Such commitment is essential but such
promises should be viewed in the light of StarLink corn that was
approved only for animal consumption but appeared in foods for human
consumption. GM crops as edible vaccines should be restricted to plant
tissue culture or to contained plant growth chambers or high security
greenhouses. In conclusion, edible vaccines for FMDV have been tested
and described in the scientific literature. Edible vaccines are
effective but have potential side effects that may actually contribute
to spread of the disease. Government regulators should make any
experiments with edible vaccines public. References Landridge,W
"Edible Vaccines" 2000 Scientific American on line Sept. Weiner,H.
"Oral tolerance for treatment of autoimmune diseases" 1997 Ann Rev Med
Franzone,P,Sadir.A,Escribano,J and Borca,M "Induction of a protective
antibody response to foot and mouth disease virus in mice following
oral or parenteral immunization with alfalfa transgenic plants
expressing the viral structural protein VP1" 1999 aVirology 255,347-53
Wigdorovitz,A,Perez Filgueira, Roberson,N,Carrilo,C, Sadir,A, Morris,T
and Borca,M "Protection of mice against challenge with foot and mouth
disease virus (FMDV) byy immunization with foliar extracts of plants
infected with recombinant tobacco mosaic virus expressing the FMDV
structurl protein VP1" 1999b Virology 264,85-91
Wong,T,Cheng,E,Chan,Z,Sheng,W,Yan,W,Zheng,Z and Xie,Y "Plasmids
encoding foot and mouth disease virus VP1 epitopes elicited immune
responses in mice and swine and protected swine against viral
infection" 2000 Virology 278,27-35

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