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December 2021 Pulse

On October 20, 2021, The Straits Times reported that for the first time, ‘a pig kidney has been transplanted into a human without triggering immediate rejection by the recipient’s immune system’. This may signal a significant breakthrough in xenotransplantation that could ‘eventually help alleviate a dire shortage of human organs for transplant’.

Scientists at NYU Langone Health temporarily attached a pig’s kidney to a pair of large blood vessels outside the body of a deceased woman and observed for two days. The functions of the deceased recipient’s body were sustained by a machine after her family had given their consent to the experiment.

The scientists were pleased to report that the kidney functioned normally, filtering waste and producing urine, without displaying any signs of rejection. ‘It had absolutely normal functions’, exclaimed Dr Robert Montgomery of NYU Langone Health. ‘It didn’t have this immediate rejection that we have worried about’. The pig from which the kidney was procured for this experiment was gene-edited to remove the sugar that would trigger rejection.

The history of animal-to-human transplants can be traced as far back as the 17th century, when doctors tried unsuccessfully to use animal blood for transfusions to save human lives. In the 20th century, doctors have made many attempts to transplant organs procured from baboons into humans. The most famous case was Baby Fae, a dying infant who lived for 21 days after receiving a baboon heart.

Not all animals, however, are suitable organ donors. Even the animals that are purportedly closer to humans from an evolutionary standpoint, such as apes and baboons may not be the best candidates for xenotransplantation. Factors such as size, life expectancy, hormonal environment, body temperature, and risk of infections must be taken into consideration in selecting an animal donor.

So far, scientists have found pigs to be the most suitable and common source of xenotransplantation. This is because pig organs are similar in size to human organs. In addition, pigs are relatively easy to clone and modify genetically to remove the possible triggers of negative immunological responses.

A further advantage in using pigs is the fact that they have a relatively short reproduction time and require only about six months to grow to a suitable size to provide transplantable organs. This is well below the average waiting times for human organ transplants – about 191 days for heart transplants and 679 days for kidney transplants in the US.

Currently, pig heart valves are routinely transplanted into humans. Pig skin is also being used as grafts for burn patients, and pig pancreas cells are used to help patients with Type 1 Diabetes.

One drawback is that some religious traditions and cultures prohibit the use of porcine organs as transplants. For example, Islamic cultures generally do not allow the use of organs procured from pigs for transplants, although several Islamic scholars have argued that the saving of lives should override this prohibition. Interestingly, although Judaism forbids the consumption of porcine food products, it allows the use of pig organs as transplants.

Xenotransplantation promises to be a very feasible solution to the chronic shortage in transplantable organs across the globe. However, there are important ethical and social issues related to it that should not be ignored. These issues have to do mainly with safety, but there are also larger social concerns such as animal welfare and just distribution.

SAFETY CONCERNS

The most significant issue surrounding xenotransplantation is safety. There are basically two main safety concerns associated with animal-to-human organ transplants.

The first has to do with the negative immunological response to the xenograft as the immune system of the recipient recognises it as ‘foreign’ and correlatively rejects it. The phenomenon known as ‘hyper-acute rejection’, where the body of the recipient rejects the organ as soon as it is transplanted, is also not uncommon, especially in xenotransplantation.

The risk of rejection can possibly be mitigated or even circumvented by genetically engineering the donor animal. This is done by introducing a small amount of human genetic material into a developing pig embryo so that its organ is not recognised as foreign by the human recipient.

Scientists have achieved some degree of success with this method in animal experiments. In 2016, researchers from the National Institute of Health (NIH) in the US announced that they have kept a pig heart alive in a baboon for three years.

The second danger related to xenotransplantation is the transmission of diseases from the donor animal to the human recipient. That humans are susceptible to zoonoses (animal diseases) is well attested to in the history of modern medicine. Examples include the herpes B virus from macaque monkeys which causes encephalitis in humans, and the human immunodeficiency virus (HIV) that causes AIDS in humans. HIV is very similar to the simian immunodeficiency virus (SIV) in primates.

It is difficult to detect the viruses that may cause harm to humans because some of them do not produce any symptoms in the animals from which they originate. Some viruses, such as the macaque herpes B virus, are relatively harmless to its animal host but cause severe illnesses in human beings. In addition, there are infectious organisms in primates and pigs that are currently unknown. This makes it difficult to ascertain the safety of xenotransplantation with confidence.

The problem becomes more complicated when we take into consideration the fact that viruses can easily and rapidly mutate once they inhabit a different host, in this case, humans. These mutations may allow the animal viruses to more readily infect humans, resist the attack of the human immune system and even become drug-resistant. In addition, animal viruses may combine with human viruses, producing a new virus which is able to pass effectively from human being to human being, thereby putting the general population at risk of infection.

In 1996, the Nuffield Council on Bioethics published a paper entitled ‘Animal-to-Human Transplants: The Ethics of Xenotransplantation’ which proposed the principle of precaution which, in my view, is still relevant today. According to the Council:

The principle of precaution requires that action should be taken to avoid risks in advance of certainty about their nature. This challenges the view that, until there is evidence that a new technology is harmful, it is acceptable to proceed with its development. It suggests that the burden of proof should lie with those developing the technology that it will not cause serious harm.

The Council states that ‘the risks associated with possible transmission of infectious diseases as a consequence of xenotransplantation have not been adequately dealt with. It would not be ethical, therefore to begin clinical trials of xenotransplantation involving human beings.’

Despite the progress made in this field, the cautionary note sounded by the Nuffield Council in 1996 still applies today.

ANIMAL WELFARE

Some ethicists object to the raising of pigs as sources of organs for transplantation. For example, ‘deep ecologists’ would argue that human beings, as part of the natural order, are just one among the many animal species and that they can therefore claim no special privilege or status. Put differently, these ethicists denounce the ‘sin’ of speciesism and argue that human beings are not intrinsically more worthy than other animals.

Buddhist ethicists have raised similar objections to the use of animals as sources for organ transplantation. On the basis of the concept of ‘dependent co-arising’ they maintain that there is no independent self or a separate existence of species. Therefore, because human beings are an inseparable part of the intricate web of living creatures, they must treat other animals as they treat themselves.

Both perspectives eschew the instrumentalization and commodification of animals for the benefit of human beings.

The question that these ethicists and scores of animal rights activists raise is an important one, and should not be trivialised or ignored. Does the human species have the right to use other species for their own – in this case, medical – benefits?

My view is that it is permissible for human beings to use animals for medical treatments. But this must always be done in such a way that does not result in the mistreatment and wonton destruction of animals.

This Christian stance on the use of animals by human beings is articulated succinctly in para 2417 of the Catechism of the Catholic Church:

God entrusted animals to the stewardship of those whom he created in his own image. Hence it is legitimate to use animals for food and clothing. They may be domesticated to help man in his work and leisure. Medical and scientific experimentation on animals is a morally acceptable practice if it remains within reasonable limits and contributes to caring for or saving human lives.

Raising animal populations for medical research and drug production has been practiced for a long time. However, with the advent of new genetic technologies like recombinant DNA technology, the methods of raising these animals have become more sophisticated.

In addition, most governments follow agreed protocols and regulations, such as the 1996 US Public Health Service (PHS) Guidelines entitled ‘Draft Public Health Service (PHS) Guideline on Infectious Diseases in Xenotransplantation’. Section 3.2 of the Guideline states that animals raised for transplantation should be housed in facilities that meet the recommendations set out by the Guide for Care and Use of Laboratory Animals.

As a minimum, these animal facilities ‘should have a routine well-documented herd health and surveillance system’. They should also ‘have on staff veterinarians with expertise in the infectious diseases prevalent in the animal species and should maintain active collaboration with accredited microbiology laboratories.’ In addition, these facilities should be ‘subject to inspection by appropriate members of the transplant teams and public health agencies.’

Apart from the physical health of the laboratory animals, attention must also be given to their mental health – in a word, their total well-being. The British Farm Animal Welfare Committee (FAWC) defines the well-being of laboratory animals in confinement in terms of the famous five freedoms: freedom from hunger and thirst, freedom from discomfort, freedom from pain and injury or disease, freedom to express normal behaviour, and freedom from stress and fear.

Within the constraints of gnotobiotics (the control of pathogenic microorganisms), we should do our best to ensure that these animals enjoy enriched confinements that would give them a sense of wellbeing.

Thus, while it is extremely important that these animals be kept free from pathogens (which means that they cannot be kept outdoors in a pastoral manner), we should ensure that their lives are pleasant. According to biomedical science philosopher Bernard Rollin to achieve this, there must be ‘adequate space, an enriched environment, reservation of social groups, good handling by stock-people, adequate veterinary care, proper diet, climate control.’

CONCLUSION

Even if xenotransplantation is absolutely safe, the public must still be widely consulted before it is put into practice. Societal involvement in the formation of policies and protocols regarding xenotransplantation is also important because everyone has a stake in public health.

To be avoided at all cost is what Bernard Rollin calls the practice of ‘bad ethics.’ In Rollin’s view, there are two factors that ‘militate in favour of the proliferation of bad ethics.’ They are the ‘appalling social lack of understanding of science’ and ‘the scientific community’s denial of the relevance of ethics to science’.

Finally, even if xenotransplantation is accepted, safe and successful, the question of the fair allocation of transplantable organs still needs to be addressed. Here again, the public must be involved in the discussion, and contribute to the fashioning of a policy of organ distribution that is realistic and just.

As political scientist Margaret A. Clark puts it:

Justice and fairness require society’s burdens and benefits be borne equally. Democracy requires that the medical professions, patients, and the body politic have a voice. Physicians should not be forced to choose between saving a life and distributing organs fairly.


Dr Roland Chia is Chew Hock Hin Professor at Trinity Theological College (Singapore) and Theological and Research Advisor of the Ethos Institute for Public Christianity.