Animal Biotechnology Science-Based Concerns (2002) / Chapter Skim
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3. Animals Engineered for Human Health Purposes
3. Animals Engineered for Human Health Purposes
Pages 51-60
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From page 51... ...
BIOPHARMACEUTICAL PRODUCTION A large number of genes encoding useful protein products—hormones, blood proteins, and others has been introduced into domestic animals, leading to their expression in milk, eggs, or blood (Dove, 2000; Table 3.19. So far, none of these animals has been used for commercial production.
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From page 52... ...
These standard products are subject to specific regulatory procedures, and essentially the same regulatory framework is expected to apply for products of both biopharming and standard technology as regards common issues such as purity of the final product, microbial contamination, levels of adventitious DNA, and the like. Nevertheless, a few more specialized concerns arise.
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From page 53... ...
In mice, there is a well-studied model in which recombination between benign endogenous proviruses or endogenous proviruses, and infecting viruses early in the life of the animal, can cause a high incidence of lymphoma Pearly 100 percent in some mouse strains) 6 months later (Stoye et al., 1991, Rosenberg and Jolicoer, 1997~.
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From page 54... ...
This would create a regulatory problem of dealing with unapproved transgenes after their release into the food chain a problem analogous to that posed by the appearance in food products of Starlink, a transgenic maize unapproved at the time for human consumption (Fox, 2001~. XENOTRANSPLANTATION Xenotransplantation differs from other uses of genetically engineered animals in that it has the potential to create something entirely new permanent
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From page 55... ...
For regulatory purposes, human cells cultured ex viva with the cells of any other animal, such as mouse cell lines, also are considered to be xenotransplants (DHHS, 2001~; co-cultivation with mouse cell lines has been used in the preparation of some cultured skin grafts as well as human stem cell lines; Thomson et al., 1998~. While nonhuman primates, such as the baboon, would seem to have physiologic and immunogenetic advantages such as the lack of a hyperacute immune response, their scarcity as well as the difficulty of clearing them of adventitious infectious agents (as well as ethical concerns)
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From page 56... ...
The principal concern is that the uniquely close relationship created between recipient and host will allow novel opportunities for transmission of infectious disease, and possible creation of new disease agents in the process. While the history of close contact between humans and pigs is a very long one, and one would imagine that all possible transmission of infectious agents between the two species already would have been seen and thoroughly studied, it is possible that the "co-culture" environment of a transplant would be qualitatively different in ways that would allow different outcomes.
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From page 57... ...
Enterovirus swine vesicular disease Human enteroviruses Encephalomyocarditis Rhinovirus Caliciviridae Enteric calicivirus Swine hepatitis E 2,5 1 5 l Astroviridae Porcine astrovirus 5 Togaviridae Western encephalitis 1 Eastern encephalitis 1 Venezuelan encephalitis 1 Getah 1 Chikungunya Flaviviridae Japanese B encephalitis 1 Louping Ill/TBE complex 1 Wesslebron disease 1 Apoi 2 Dengue fever 1 West Nile fever 1 Classical swine fever (hog cholera)
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From page 58... ...
Desoxyviridae African swine fever 5 NOTE: 1=Zoonotic. 2=Replicates in human cells or weak evidence for zoonotic potential.
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From page 59... ...
Nevertheless, given the release of viruses infectious to human cells by many types of pig cells; the close similarity of these viruses to viruses lmown to cause cancer, immunodeficiency, and other diseases in mice and cats; the well-known adaptability and variability of retroviruses; and the example of the rapid worldwide spread of HIV and AIDS, there is serious concern that the novel association between pig and human tissues might create novel evolutionary opportunities for the virus, leading to the appearance of a new pathogen. Although such a pathogen could have serious long-term adverse consequences for the transplant recipient, this issue is not an area of concern since it is far outweighed by the potential benefits of the transplant.
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From page 60... ...
Attempts also are being made to identify specific proviruses responsible for production of infectious virus and then to selectively breed them out of lines of animals to be used as transplant donors (Herring et al., 20013. TABLE 3.4 Theoretical scale of risks associated with PERV transmission from xenotransplants.
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