GM Pigs for Xenotransplantation

A much more serious intervention in farm animals is xenotransplantation. Various pig organs have potential for transplantation into human beings, including hearts and kidneys. Research in this area has been carried out for many years, prompted by hope that this would meet the shortfall in supply for human organs, where people are currently dying while on the waiting list. There are immense technical problems, however, which in turn pose major issues of ethics. This is discussed in more detail in our pages on the Ethics of Xenotransplantation.

The first is the rapid rejection by the human immune system of organs from another species. Pigs have to be genetically modified to try to overcome this. Several human genes have to be added to the pig to send "human" signals that would prevent the human immune system not to reject the organ. There are as many as four genes involved. This requires multiple gene changes, something which has never been done before in a large animal, and is hard to achieve even in plants. It also requires knocking out genes in the pig which would trigger the rejection. So far most genetic engineering has only added genes. The nuclear transfer cloning of piglets by PPL in 2000 has opened a potential way to do this, if gene deletion were done in vitro in cells, and if pigs could be "grown" from these genetically altered cells. This is uncharted scientific territory. No one knows if this can be done to overcome rejection to a sufficient degree for a viable medical procedure.

The second technical barrier is the remote risk of the transfer of a pig retrovirus to humans, to which humans might not be immune. The concern is less for the patient, who is probably terminally ill anyway, but about the possibility that such a virus might be transmitted to the family and then out into the wider human population. This is an extremely remote risk, in terms of probability, but it could have epidemic consequences were such a chain of events to occur. The origins of HIV and the trans-species aspect of BSE both present scenarios sufficient for the government to have a moratorium on clinical trials. Its advisory body on xenotransplantation has recommended draconian restrictions on the patient and family, were clinical trials ever to begin. The implications and evaluation of this lie beyond the scope of the present report, but it clearly indicates the delicacy and complexity of the animal - human interface.

For the present report our main ethical concern is to review the use of animals in this way. To breed and genetically engineer an animal solely to remove an entire live organ represents a different use of animals from anything humans have done before. It is a large leap from using pig heart valves, which are merely dead tissue with convenient elastic properties. The "yuk reaction", which the idea of xenotransplantation often prompts, suggests that having a complete animal heart inside oneself poses underlying questions beyond mere unfamiliarity. Some respond by contending that if we accept eating pigs, it is even more justified to use them this way to save human life. This purely consequential way of framing the issue is shallow, however. Logically it would justify doing literally anything to a pig in order to save human life. It is at odds with any ethical perspective based on the notion that animals have intrinsic value, and the implication from the biblical examples that animal use eventually has limits. The landmark Banner Report on animal ethics established that there are some things we should never do to animals, no matter what the reason.¹³ This "ham sandwich argument" also side steps other issues. Unlike eating animals, there is no parallel to xenotransplantation in nature. The fact that xenotransplantation is unnatural, in that sense, may not necessarily make it wrong, but it prompts a question whether this is an acceptable extension of human use of animals from traditional suppliers of food, clothing, traction, transport and manure?

For some, even if the genetic change is not an objection, the interspecies mixing of whole organs violates a wisdom in God's natural order, of which the retrovirus risk is a physical indication, indeed a warning that this is quite different from eating pigs. For our working group the majority did not feel they would draw an absolute line here, but expressed some serious reservations. We noted that creating pigs to kill them to obtain transplant organs is different from taking the same organ from someone already dead. It constitutes a serious intervention in highly intelligent animals with some close physiological similarities, and for whom many humans have a special fondness. There are also animal welfare questions about the quality of life for the pigs kept, of necessity, in a highly sterile environment.

We suggested a "no, unless" approach. It would only be justified in exceptional circumstances. Does the mismatch in supply and demand for a surgical procedure which has become resource limited - the "shortage" of transplant organs - might meet the case? A few months of life extension, with immunosuppressant drugs merely delaying the inevitable death would not be reason enough. A long, high quality life might well be, if the technology could work well enough. It is justified to conduct research while this remains a realistic prospect. Given the complexity of the multiple genetic modifications that are now likely to be needed, it is not a foregone conclusion that there will come a point where that ethical balance would be reached for it to become an accepted therapy.