- WASHINGTON (Reuters) - Corporate
researchers said on Monday they had bred a pig that does not seem to transmit
potentially dangerous viruses to human cells, and said it might be a way
to make animal-to-human transplants safe.
- Charlestown, Massachusetts-based BioTransplant Inc. said
its miniature swine carried the viruses, but for some reason did not transmit
them to human cells the way normal pigs do.
- It hopes it can now genetically engineer its miniature
pigs so that human bodies will accept their tissue and organs.
- ``What we are hoping to do with it is build this inbred
herd as a potentially safer source of cells, tissues and organs for xenotransplants
(animal-to-human transplants),'' Elliot Lebowitz, president and chief executive
officer of BioTransplant, said in a telephone interview.
- ``We are hoping that we can save a lot of lives in a
safer way and also reduce the healthcare costs, which are horrendous for
end-stage organ disease.''
- More than 70,000 Americans and hundreds of thousands
of people around the world are on waiting lists for new organs, but there
are not nearly enough to go around. An estimated 10 people die every day
in the United States alone while waiting for a heart, liver, kidney or
- Pigs are considered a possible good source for organs,
as they are readily available, easily bred and are about the same size
- But there are two huge obstacles. Like most other animals
including humans, pigs carry viruses called endogenous retroviruses. These
viruses have incorporated themselves into the genome, cannot be removed
and are infectious.
- And animal cells have a molecule on their surface that
causes the human immune system to recognize them as foreign and reject
them. Transplanted animal organs quickly die in the human body.
- Earlier this month, Daniel Salomon of the Scripps Institute
in California reported that he had shown that the pig viruses, known as
porcine endogenous retroviruses (PERVs), can infect human cells. He said
earlier studies that suggested PERVs do not infect people may not have
looked in the right places.
- Lebowitz said his company hired one of the discoverers
of PERVs, Clive Patience, to try and get around this problem.
- ``We have shown that it is possible to create pigs which
will not have human infectivity from PERVs,'' Lebowitz said.
- ``It appears that these animals don't contain replication-competent
PERV in human cells. We don't know why.''
- Patience was scheduled to present the findings to a transplant
conference in Rome on Monday and was not immediately reachable for comment.
- Lebowitz said the miniature pigs, created for BioTransplant
by a local supplier of animals for medical research, were highly inbred
and this could be the reason their viruses could not be transmitted to
human cells at least in the laboratory.
- The company has not tested the pig cells in living animals
to see if they can be infected, but said it did incubate human cells with
cells from normal pigs and they became infected.
- The company has licensed its technology to Swiss pharmaceutical
giant Novartis (NOVZn.S), Lebowitz said.
- Several companies are working to create pigs that can
be used for animal-to-human transplants, called xenotransplants. British
scientists at PPL Therapeutics (PTH.L), associated with the Roslin Institute
in Edinburgh where Dolly the sheep was cloned, have cloned pigs with the
aim of creating animals suitable for xenotransplants.
- But U.S.-based Geron said it was reducing funding to
its Roslin subsidiary, Geron Bio-Med, for work on cloning genetically engineered
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