Why not have a heart-to-heart with a pig?

SATURDAY ESSAY by Steve Connor

THERE IS something deeply ingrained in the human psyche about the fear and revulsion inspired by the image of a creature that is half- man, half-beast. From the Minotaur to Midsummer Night's Dream, the animal- human chimaera has been a grotesque spectacle relegated, thankfully, to the pages of mythology.

But could this always be the case? Now that the Government has laid down the ground rules for the first organ transplants from animal to humans, it seems perfectly likely that the day will arrive when a man could be truly said to be a pig at heart. The first human patients to receive pig hearts could do so as early as next year, though this optimistic timetable is just as likely to slip into the early years of the new millennium.

Many people will be understandably revolted by the idea of men or women walking around with pigs' hearts. The notion of the heart being the seat of emotional strength and fallibility goes back many centuries. The bravery of Richard I emanated from his lionheart, wicked witches throughout the ages were said to be heartless, and Cilla Black made her fame in the Sixties from asking whether anyone with a heart could not help but fall in love.

But this irrational fear of losing your heart to a pig, so to speak, cannot possibly justify the rejection of xenotransplantation, when animal organs and tissues are used in human patients. There is, nevertheless, a definite ``yuk factor'' associated with xenotransplants, especially when it comes to pigs. For many religions, the pig is considered an unclean animal which eats unspeakable things. But for anyone who knows pigs, there is something quite charming, if not unnerving, in the way they stare you right in the eye. As Winston Churchill once said, dogs look up at you, cats look down on you, but pigs treat you as an equal.

Scientists have chosen the pig for very good reasons. It grows to about the same size as a human and so its organs can fit snugly into the space provided by a transplant surgeon. It is a domesticated animal which can be easily handled, and it is sufficiently different from humans to make the notion of using them more acceptable than, say, monkeys.

According to some experts, monkeys look a bit too much like us to be suitable xenotransplant candidates. In fact, they have already been used in the United States for a few unsuccessful transplant experiments on humans, but the research suffered from an image problem connected to the fact that monkeys look ,and often behave, in a very human-like way. Higher primates, such as baboons and chimpanzees, share some of the characteristics - such as self awareness, fear and complex social organisation - that we often take to be uniquely human.

The poor old pig, however, does not get the same respect from the experts. ``We realise that pigs are able to suffer but believe that their suffering is likely to be less than that of higher primates,'' explained Professor David Morton, a biological ethicist at Birmingham University who was a member of a committee investigating the issue, set up by the Nuffield Council on Bioethics two years ago. It seems the pig is just not self- aware enough to suffer pain in the same way as primates and humans.

It would, however, still be hard for people to raise ethical objections to using pigs if they are prepared to eat them. Carrying a pig-skin wallet next to your heart is, from the pig's point of view, just as bad as carrying a porcine heart inside your chest. If we are prepared to slaughter millions of pigs each year for their meat and skin, what could be the objection to killing (as humanely as possible) a few more to save thousands of human lives?

This brings us to the essence of the problem. Only one in three people who need organ transplants receive them. As more people are living longer, the demand for replacement organs, as old ones wear out, continues to rise. Although there is continuing development of mechanical organs and artificial tissues and organs, this is unlikely to go anywhere near meeting the shortfall between supply and demand for at least another 20 or 30 years. In the meantime people, including children, are dying.

This means there is a desperate urgency to improve on the previous attempts at xenotransplants. The most famous example is Fae, the ``baby with a baboon heart'' encapsulated in the lyrics of a song on Graceland, the Paul Simon album. But the days of miracle and wonder were not enough to save two-week-old Fae, who died within three weeks of receiving her primate heart. Her body's immune system had effectively eaten her new heart away in a violent chemical rejection. This type of rejection has continued to frustrate attempts at transplanting organs from one species to another.

Unlike normal organ transplants between people, xenotransplants pose unique difficulties associated with the nature of this violent rejection. Because the tissues of two species are so unrelated, the immune system does not merely reject them, it ``goes nuclear'' and attacks the invader with a powerful array of antibodies known as the complement reaction. For years, transplant scientists could do little to combat the complement reaction - until now.

The breakthrough occurred in Cambridge where scientists were able to insert human genes involved in the complement reaction into pig embryos. The animals therefore grew up to have ``humanised'' organs that should, in theory, be less likely to be rejected. In 1995, the scientists showed that monkeys can survive with genetically-engineered pig organs for more than 60 days. This finally opened the doors to the use of pig organs in human transplant operations.

There was, however, one very real fear of rushing ahead. Many diseases, from Aids to rabies, are known to involve the transfer of animal viruses to humans when the two have come into close contact. HIV is thought to have evolved from a similar virus of African monkeys. Pigs are also known to play an important role in the evolution of new and more deadly strains of the influenza virus. What could be the chances of an unknown pig virus getting into a human transplant patient and from there creating a new and lethal epidemic?

The answer, of course, is that nobody knows for sure. About 18 months ago, scientists discovered a hitherto unknown retrovirus (the same viral group as HIV) in the pig which although it does not cause the pig any harm, can infect human cells in the laboratory, though this is not the same as causing disease in a person. It would be impossible to ensure a virus-free pig for transplants because a disturbing feature of these retroviruses is that they incorporate themselves into the animal's genetic material - its DNA - and so can therefore be inherited from sow to piglet, with scientists powerless to prevent it.

Doomsters would argue that this is a good enough reason to stop everything now before we end up with another BSE-like disaster. ``This is potentially the first step down a very dangerous road indeed,'' said Roger Gale, a Conservative MP, on the announcement of the new government guidelines on xenotransplants. ``Science really is now beginning to play God in a way that even those supportive of the advances of medical science must find disturbing, if not abhorrent.''

Yet just because there is a risk attached to a new innovation, it is hardly grounds for junking the whole idea. Just about every medical advance, from vaccines to antibiotics, has carried risks, but the lives saved have made them worthwhile. The Government guidelines address the concerns over animal welfare and establish the necessary framework for making sure - as much as anyone can - that the risks are kept to a minimum.

If xenotransplants were banned, as some animal welfare groups have proposed, then the alternative is more human suffering and more deaths. Animal rights activists should bear this in mind when they raise their objections. Their love of animals should not become a hatred of humanity.