Xenotransplantation: Why We Shouldn't

Xenotransplantation, as defined by the U.S. Food and Drug Administration (FDA), is "any procedure that involves the transplantation, implantation, or infusion into a human recipient of either (a) live cells, tissues, or organs from a nonhuman animal source, or (b) human body fluids, cells, tissues or organs that have had ex vivo contact with live nonhuman animal cells, tissues or organs."

Translation…
Xenotransplantation (pronounced ZEENO-transplantation) is the process of transferring (transplanting) organs, tissues, or cells from one animal to another. The term comes from combining "xeno", the Greek world for stranger, with the word "transplant". By transferring, we mean transplanting, implanting, or infusing organs, tissues, or cells from one species of animal to another---or to a human being. These days, the likely source of animal organs for humans is genetically-engineered pigs (primarily small swine).

The FDA defines several different types of xenotransplants. (1) Solid organ xenotransplant, which is removing an organ, such as a kidney, liver, lung, or heart, from a donor animal (pig) and transplanting it into people. (2) Cellular or tissue xenotransplant, which is grafting tissues or cells (such as islet [insulin-producing] cells) from a donor animal and grafting or implanting it directly into the organ of a recipient (such as the pancreas of a person with type 1 diabetes). (3) External therapies, which is filtering and/or purifying human blood cells outside of the body through an animal organ (such as a kidney) or cells in an external device. (4) Human/animal hybrid, which is human cells grown in culture with non-human animal cells that are then transplanted back into human patients.

Plus, there are "non-living" animal tissues, such as pig heart valves, that have been used for repairing hearts in humans for many years.

(A great deal of "xenotransplantation" takes place in laboratory experiments, particularly in the field of cancer where human tumor cells may be transplanted into mice or other animals to see if a possible anti-cancer agent will work. That’s not part of this discussion.)

Want a reason why we SHOULD NOT perform xenotransplants? I’ll give you millions.

First, animals are frequent carriers of infectious agents. These most certainly can be transferred into human beings. (If it’s just by proximity, the process is called "zoonosis". If it’s by transplantation, it’s called "xenozoonosis".) The FDA guidelines to industry intent on producing organs (or any products) for xenotransplantation state:

"Infectious agents of concern will differ among source animal species and among cell or tissue types within each species. Therefore, you should individualize clinical tests for the specific product in question. The categories of infectious agents of concern include bacteria, fungi, mycoplasma, virsues, and the agent(s) causative for TSEs [transmissible spongiform enceaphalopathy]. Tests should be available for agents known potentially to be present, including those that are pathogenic in the source animal species and agents that are known to infect human cells in vivo or in vitro. You should have the capability to test for latent viruses or pathogens, and you should be prepared to develop and validate clinical tests for new pathogens that may not be recognized at the time of xenotransplantation. You should identify specific infectious agents for which tests will be performed."

That’s one tall order! The FDA is insisting that animals for xenotransplantation are disease-free. Not only for viruses and bacteria that they know, but for those they DON’T know, but can anticipate. Assuming they can anticipate!

We’re currently worried about Avian Flu. They’re talking 5 to 150 million potential deaths. But we don’t know what mutation the virus may undergo that could make it extremely lethal. And remember, the worry about Avian Flu jumping to humans is just from being close to infected animals.

Enter xenotransplantation---where you’re not only close to the animal, you’re putting a chunk of it inside you. (Chickens aren’t the only ones with potentially dangerous viruses; pigs have them too.)
Plus…

There’s an even bigger worry with xenotransplantation. The greatest danger is from what are known as porcine endogenous retroviruses or "PERVs". PERVs are retroviruses that are embedded in pig DNA and could be potnetially transmitted to patients, and spread beyond just patients, following solid organ xenotransplantation. As described by the Australian Government’s National Health and Medical research Council, PERVs are:

"…present in almost all strains of pigs and cannot be removed by raising pigs in sterile conditions. Although PERV is inactive, and therefore harmless in pigs, there are concerns that transplantation into humans may activate the virus, creating a new human disease that could spread to those close to the transplant recipient and eventually to the wider community. PERVs can infect human cells in the laboratory, suggesting that they could infect humans through xenotransplantation…"

And you’re putting this in a person whose immune system is compromised---that is, not working well!

Worse, retroviruses do not always initially cause obvious signs of a disease. If a retrovirus were present in a xenotransplant organ were to infect the human recipient of that organ, it could spread to close contacts, caregivers, and even the general population before it had even become obvious that an infection had occurred.

The risk from PERVs is so great that the US FDA has guidelines calling for establishing a national database for xenotransplantation, maintaining specimens from animals and xenotransplant recipients for as long as 50 years, lifetime monitoring of xenotransplant patients and mandatory autopsy upon death, repeated monitoring of health care providers, and all (intimate) contacts of the patient FOR LIFE.

In short, there’s genuine concern that a PERV could mutate in a human host and create a deadly disease that could kill more than just the patients. Something that could kill people around them.
So, if you’re worried about the Avian Flu killing millions of people, maybe you---relax. There something potentially a lot worse.

---For FAQs on xenotransplantation: http://www.nelsonerlick.com/html/explore_xenotrans_faqs.html.
---For links on xenotransplantation:
http://www.nelsonerlick.com/html/explore_xenotrans_links.html
---Dr. Nelson Erlick
Author, The Xeno Solution and GermLine