Genetically Modified, Cloned Pigs Could Provide Organs for Humans

PPL Therapeutics announced this week that on Christmas Day five genetically modified and cloned Pigs were born that bring the possibility of Xenotransplantation — transplanting organs from animals to human beings — one step closer.

The pigs are genetically modified to make it more likely that an organ transplanted to human beings would not be rejected by the human immune system. Researchers knocked out a gene in the pigs that produces an enzyme that adds a sugar to the surface of the cells. This sugar would be identified immediately by the human immune system which result in an attack and the rejection of the organ.

Which does not mean that organs from these genetically modified pigs are ready to be transplanted into humans. In fact, another gene that performs a similar function would have to be knocked out as well as several human genes added in order for there to be a reasonable chance at transplanted organs not being rejected.

Still, PPL Therapeutics vice-president David Ayares told New Scientist that he hopes human trials could begin within five years. Pigs, by the way, would be ideal for heart transplants since the heart in this particular species of pig is roughly the same size as the human heart.

Since the pigs were cloned, PPL Therapeutics would have the ability to quickly ramp up production of replacement organs should their technology eventually succeed in human trials.

Of course, the animal rights community is opposed to this, with the Campaign for Responsible Transplantation once again raising the red flag about possible pig viruses being passed on to human beings. CRT has spent the last couple of years arguing that the possibility of cross-infection of porcine endogenous retrovirus should lead to an outright ban of xenotransplantation with pigs.

In 1997, researchers proved that, at least in laboratory conditions, PERV could jump from pig cells to human cells. PPL Therapeutics and other companies hoping to market this technology will likely have to create pigs that are free from PERV. The PERV virus has been completely sequenced and patented, however. Another company, Immerge, has bred pigs which it says are genetically modified so they cannot pass along PERV to human beings.

Which is largely irrelevant to the animal rights activists, for whom the argument is largely a smokescreen. Wired, for example, cites an earlier interview with CRT’s Alix Fano in which Fano said,

Every animal has hundreds of retroviruses, and there’s no way you can breed them out. And there could be other viruses lurking in these pigs, not to mention parasites, bacteria, fungi and latent infections of all kind.

Of course if medical technologies are required to meet a criteria of eliminating unknown fears and possibilities, then a lot more has to go out the window than just xenotransplantation. For example, pig heart valves are currently used in valve replacement surgery — and with no reports of cross contamination of pig viruses, parasites, etc. to my knowledge.

Ironically, Dr. Jay Fishman, who sequenced the PERV disease, presented a paper in May 2000 noting that organs transplanted from animals to humans might actually turn out to be safer because common human diseases that cause organ failure would likely not grow in organs transplanted from another species. Wired quotes Fishman as writing in that paper,

Due to the species differences between the host (human) and donor (non-human species), the risk of infection of the transplanted organ … may actually be decreased. This incudes common pathogens such a cytomegalovirus, Epstein-Barr virus, … herpes, hepatitis B and C, and possibly human immunodeficiency viruses.


Cloned pigs as organ donors?. Kristen Philipkoski, Wired, January 3, 2002.

Knock-out pig clones advance transplant hopes. Emma Young, New Scientist, January 3, 2002.

Animal transplants: a step closer?. The BBC, January 3, 2002.

New pig clones born. The BBC, January 2, 2002.

More Xenotransplantation Advances

Even if they don’t lead
immediately to treatments in human beings, the announcement of two recent
advances in genetic engineering of organs provides more evidence of the
sort of technologies likely to hit the mainstream of medical technology
before the end of the next decade.

In mid-February researchers
announced in Science News that they had successfully transplanted
bladders grown in the lab into six beagles. The scientists grew the bladder
cells around a plastic form to make it take the shape of the bladder and
then implanted the artificial bladders in the dogs. Within three months
the artificial bladders were completely active and some of the dogs have
had the bladders for almost a year with no problems.

Obviously getting the technology
to work in human beings is a whole other problem, but these experiments
are doing for this technology what the early animal experiments on organ
transplantations did – they suggest solutions and help scientists better
understand the problems they will encounter when seeking to grow human
organs in the lab.

In a related story, Canadian
researchers are hoping to take that step of translating animal experiments
into a treatment for human beings sometime this year. Researchers there
expect for the first time to use a genetically engineered pig liver to
keep a human being alive while waiting for a liver transplant from a human

Pharmaceutical company Novartis,
which has been harshly criticized by animal rights activists for its efforts
in genetic engineering, is reportedly ready to spend up to $1 billion
to develop a viable pig liver. To avoid the risk of spreading disease
from pigs to human beings, the pigs will be raised under special conditions
to assure they are disease free. The pigs are isolated from other animals
and housed in a sterile environment. The pigs are fed by hand to avoid
microbes that might pass from pig to pig while suckling.

The impetus to move forward
with this technology is especially strong in Canada which has a rather
low rate of human organ donation – only 12.1 donors per million people
compared to the U.S. with 17.7 donors per million people.

As I noted two weeks ago,
the Campaign for Responsible Transplantation attacked Americans for Medical Progress for highlighting former Chicago Bear running back Walter Payton’s
recent announcement that he has a rare fatal liver disease. The CRT attack
on AMP, however, seemed like an act of desperation. They tried to throw
everything but the kitchen sink at AMP – xenotransplantation might not
work, it poses a risk of transmitting disease across species, it could
be avoided by increasing the donor pool, etc.

There are many responses to
these claims (CRT doesn’t seem to keep up with recent scientific advancements
in genetic engineering) but as far as I can tell the bottom line is this:
animal rights activism in the medical experimentation field has been successful
largely to the extent that it has engaged people’s sympathies against
hurting animals, especially unnecessarily. But that play on emotionalism
is a double-edged sword, since most people are openly “speciesist”
who, when it comes down to it, will find the suffering and pain of Walter
Payton far more compelling and worthy of alleviation than that of a pig
whose death could save Payton’s life.

What seems to anger CRT to
no end is that AMP gave them a taste of their own medicine with their
focus on Payton. I say more power to them.

Usual Suspects Attack Americans for Medical Progress over Xenotransplantation

As animal rights activists
and extremist environmental groups gear up to seek an outright ban on
the transplantation of organs from non-human animals to humans, Americans for Medical Progress‘s Jacquie Calnan wrote an excellent, widely published
op-ed on the importance of pursuing research on xenotransplantation and
similar technologies. She and AMP were subsequently attacked in a release
by Physicians Committee for Responsible Medicine, People for the Ethical Treatment of Animals, Greenpeace and

Calnan’s op-ed, “Payton’s
hope” (available at highlighted the problems of former Chicago Bear running back Walter
Payton, who recently announced he has a rare liver disease and may die
within two years if he does not receive a transplant.

As Calnan noted in her op-ed,
although there are 12,000 people on the waiting list for livers, only
about 4,000 such transplants are performed each year. In 1997 more than
1,000 people died while waiting for a matching liver. Calnan’s editorial
did an excellent job of highlighting animal rights hypocrisy, which is
why I suspect it was so quickly attacked. She repeated PETA celebrity
spokesman Bill Maher‘s recent quote to US Magazine that: “To those
people who say, ‘My father is alive because of animal experimentation,’
I say ‘Yeah, well, good for you. This dog died so your father could live.’
Sorry, but I am just not behind that kind of trade off.” Someone
should send Maher a thank you note for so succinctly summing up the animal
rights philosophy.

Calnan mentioned the newly
developed device I mentioned a couple weeks ago that uses pig cells to
help keep some people alive while waiting transplants. The fact is this
technology is here today and it is already saving lives, so the animal
rights and extreme environmental activists have to fall back on two claims
to discredit the technology.

The first is that the risk
of passing diseases from non-humans to humans is too high. Animal rights
activists have released claim after claim trying to make this point, but
most of the more serious ones have later turned out to be baseless. On
the other hand, like any other thing human beings do, there is always
some risk associated with it – the risk of some new deadly disease crossing
from non-humans to humans will never be zero.

But if our society was that
risk-averse no pharmaceutical drugs or medical technology would ever be
approved since the risk of a calamity from any new technology is never
zero. If this sort of principle actually guided medical technology, certainly
technologies that we take for granted, such as vaccination, would never
have been allowed since the potential risks were only poorly known at best.

The second claim is that there
are more than enough organ donors to go around. At the end of her article,
Calnan ask for more people to become organ donors, which is a reasonable
position, but the critics of xenotransplantation seem to assume that those
organ donors are here today. A recent press release from the Boston-based
Campaign for Responsible Transplantation claimed, for example, that Xenotransplantation
advocates “use statistics and emotion to make their case … some 3,000
transplant patients die each year on in the U.S. … [but a ] US General
Accounting Office report … reveals a potential organ donor pool of 150,000
people. This is in stark contrast to previous estimates of 5,000 to 29,000
people annually … if these organs are secured, it would solve the national
organ shortage, and completely eliminate the need for animal organ transplants.”

As is the typical modus operandi with
these groups, however, this last claim is a distortion. The GAO report
was written to explore different methods of evaluating the performance
of Organ Procurement Organizations, who are assigned the task of procuring
organs and getting them into the organ sharing network. In order to do
that sort of evaluation, the GAO wanted a baseline of the upper bound of
eligible organ donors, which it estimated at 147,000 in 1994 using a technique
to estimate actual deaths and then adjust the figures to determine how
many of those deaths would have had harvestable organs.

The interesting thing is that
in the very next paragraph after giving this estimate, the GAO notes the
limits of counting potential organs this way, “we found that both
the death and adjusted-death measures [which are the source of the 147,000
figure] have drawbacks that limit their usefulness, however, including
lack of timely data and inability to identify those deaths suitable for
use in organ donation.”

First, this explicitly concedes
that the 147,000 figure was obtained using a method that the GAO admits
has an “inability to identify those deaths suitable for use in organ
donation,” which is the crux of the problem with human organ donation
itself. If it was too expensive and time consuming for the GAO to go back
four years and decide how many people were eligible organ donors,
imagine the difficulty in trying to harvest those organs on the spot.

It is one thing to look back
several years later and say there were say 40,000 automobile deaths and
of those 6,000 were potential organ donors. It is another thing to be
in place to actually obtain those organs (a severe problem in organ donation
is that even among those who have signed organ donor cards and are good candidates
to donate organs, often the organs are no longer usable by the time doctors
are aware of the potential donor or get permission from family members
to proceed. This is a situation that is unlikely to change significantly
in the near future).

In addition, the CRT release
failed to note that the number organ donors has increased over the last
few years – but the number of people eligible for organ donation has increased
even faster. I suppose if PETA had its way, this wouldn’t be a problem
since there would be no animal research and fewer people would be transplant
candidates since the medical knowledge to save their lives simply wouldn’t
exist, but barring this it seems clear that future advances in medical
science are going to continue to drive the demand for organ donation at
a much faster rate than the increase in donated organs.

If anything the GAO report
on the failures of Organ Procurement Organizations to obtain more organs
is evidence of just how difficult it is going to be to increase the level
of organ donation, and further emphasizes why xenotransplantation and
similar technologies will likely play a key role in the 21st century – provided animal rights activists aren’t given the chance to
halt this important advance.

Animal rights activists oppose xenotransplantation

Every year thousands of people die
who would have lived if it weren’t for the continuing shortage of organs
available for transplantation. Scientists around the world are working
to solve this shortage, but animal rights activists are opposing them
at every turn.

The most viable short term solution
is Xenotransplantation — genetically engineered organs from animals that
can be transplanted into human beings. Currently most such development
is concentrated on developing pig organs as a possible source for human
transplantation. Biotech companies are working at genetically modifying
the pig organs so the human recipient is less likely to reject them.

Animal rights activists, of course,
hate the idea of using pigs to do something as frivolous as save a human
life. Mike Baker, head of the British Union for the Abolition of Vivisection,
said developments in xenotransplantation represent “a very backward
step in terms of animal welfare [that] could pose serious health risks
to the human population.”

A group calling itself the Campaign for Responsible Transplantation is already circulating a petition to ban
all animal-to-human transplantation and environmental groups are also
jumping on the bandwagon, citing the possibility of a deadly virus passing
from animals to human beings in the transplantation process.

While the viral issue is certainly
a serious one, it is being addressed by regulatory agencies in the United
States and Europe responsible for approval of medical products. In both
the United States and Europe, for example, regulatory agencies are developing
strict monitoring protocols for tracking all infections and diseases contracted
by human recipients of xenotransplantation in addition to the rigorous
safeguards to minimize the risk of a crossover disease in the first place.
Unfortunately, the animal rights and environmental activists
seem unlikely to be satisfied with anything but zero risk, which of course
is impossible in any human endeavor (after all, the risk that a deadly
disease will cross over from pigs to human beings just from normal contact
on farms is not zero as the various influenza pandemics are evidence of,
though there are ways to minimize the risk).

Xenotransplantation is simply the
best chance we have to save thousands of lives around the world. Lets
hope animal rights activist and environmentalist extremists don’t close
off this important area of research before scientists even get to explore
it fully.


“Animal organs could save people if the body would accept them,”
Lauran Neergaard, The Associated Press, September 17, 1998.

“Biotech regulations: paving the way for British xenotransplantations,”
Nigel Williams, Science Magazine, August 6, 1998.

Campaign for Responsible Transplantation petition,