Xenotransplantation - Nuffield Council on Bioethics
Xenotransplantation - Nuffield Council on Bioethics
Xenotransplantation - Nuffield Council on Bioethics
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Transmissi<strong>on</strong> of infectious diseases<br />
Chapter 6<br />
Transmissi<strong>on</strong> of infectious diseases<br />
6.1 In principle, xenografts, if successful, would offer huge benefits to individual patients.<br />
Xenografting, however, may also involve certain risks. This chapter discusses the risk<br />
that using animals to supply organs will result in the transmissi<strong>on</strong> of infectious<br />
diseases from animals to the human populati<strong>on</strong>. As discussed in Chapter 4, the<br />
Working Party recommends that the development of xenotransplantati<strong>on</strong> should<br />
involve pigs, not primates as source animals (paragraph 4.40). One important reas<strong>on</strong><br />
c<strong>on</strong>tributing to that decisi<strong>on</strong> is the greater c<strong>on</strong>cern about disease transmissi<strong>on</strong> from<br />
primates. The evidence for that c<strong>on</strong>cern is presented in this chapter. The fact that<br />
xenotransplantati<strong>on</strong> of babo<strong>on</strong> organs and tissue into human beings is proposed and,<br />
indeed, already occurring in the US 1 is a further reas<strong>on</strong> for discussing the risks that<br />
diseases will pass from primates to xenograft recipients and thereby into the wider<br />
populati<strong>on</strong>.<br />
6.2 Many disease-causing organisms (pathogens) are comm<strong>on</strong> to human beings and other<br />
animals. 2 For example, the bacterium causing tuberculosis infects both human beings<br />
and babo<strong>on</strong>s, and human beings and pigs both carry the virus that causes influenza.<br />
Clearly it would be important to make sure that any animal used to supply organs<br />
was free from infectious organisms that cause disease in human beings, just as it is<br />
important to make sure that human organ d<strong>on</strong>ors are free from infecti<strong>on</strong>s that might<br />
be transmitted to a transplant recipient. The use of animals as a source of organs, it<br />
is argued, would allow for more thorough screening than is possible with human<br />
organ d<strong>on</strong>ors, and so the risk of such diseases might be reduced.<br />
6.3 In additi<strong>on</strong> to organisms that can infect both human beings and other animals, any<br />
animal species will be infected with organisms that do not usually infect other species.<br />
<str<strong>on</strong>g>Xenotransplantati<strong>on</strong></str<strong>on</strong>g>, however, may allow such organisms to infect xenograft<br />
recipients who may, c<strong>on</strong>sequently, c<strong>on</strong>tract previously unknown diseases. There is<br />
also a risk that the infectious organisms might cause disease in and destroy the<br />
transplanted organ, even if they do not harm the human recipient. Even if not<br />
infected with disease-causing organisms when transplanted, the xenografted organ may<br />
remain susceptible to infectious organisms of animals. This is most likely to be a<br />
problem with lung transplants, where infectious organisms of animals would easily<br />
get access to the transplanted animal tissue. Any pers<strong>on</strong> thinking about volunteering<br />
1<br />
Aids patient given babo<strong>on</strong> b<strong>on</strong>e marrow. (1995) Lancet, 378:756.<br />
2<br />
The word ‘organisms’ should be taken to include viruses and pri<strong>on</strong>s. While not strictly correct, the Working<br />
Party adopted this c<strong>on</strong>venti<strong>on</strong> in the interests of accessibility and brevity.<br />
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