Moving Forward with Xenotransplantation

There has been a lot of debate back and forth in recent years over the safety and efficacy of Xenotransplantation. Massachusetts-based BioTransplant says its time to move on to actually doing such transplants and hopes that within three years it will gain FDA approval to begin clinical trials in human beings.

The main safety concern with xenotransplants is the risk of viruses passing from animals to human beings through such transplantations. The risk was confirmed in 1997 when researchers demonstrated that porcine endogenous retrovirus (PERV) could jump from pig cells to human cells.

BioTransplant hopes to meet this risk head on with a two-pronged strategy. First, it recently licensed the genetic map for PERV. Dr. Jay Fishman, an associate professor of medicine at Harvard Medical School, managed to sequence and patent the genetic map of PERV. BioTransplant licensed the sequences so they can keep the virus out of any pig transplant organs. BioTransplant’s Elliot Lebowitz told Wired,

What’s important is once you know the code in terms of the alphabet that makes up this virus, you could detect the virus if it were in a pig or human patient, and also you could develop the ability to delete the virus.

BioTransplant has also been working on breeding a subspecies of pigs that cannot pass along PERV to human beings. It has developed an inbred strain of miniature swine that is larger than pigs, making their organs more suitable for human-sized bodies, and according to BioTransplant the swine are PERV-free.

BioTransplant will, of course, have to back up its optimism with solid animal data before the FDA will allow it to go forward with human testing.

Still, if everything works out, it might turn out that animal to human transplants could be far safer than human to human organ transplants. Fishman presented a paper at last year’s meeting of the American Society for Microbiology that made just this argument. If the PERV problem can be eliminated, Fishman wrote,

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 includes common pathogens such as cytomegalovirus, Epstein-Barr virus, human herpes virus 6, 7 and 8, hepatitis B and C, and possibly human immunodeficiency viruses, and even HIV 1 and 2.


Organ transplant: men are pigs? Kristen Philipkoski, Wired, February 27, 2001.

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