Virus experts are concerned that such organ and tissue transplants from animals, particularly monkeys, to people will open a new route for potentially dangerous animal viruses to infect the human population.
Peter Plagemann, an expert on primate viruses at the University of Minnesota in Minneapolis, said that baboons could harbour a little-understood agent known as simian haemorrhagic fever virus which, although harmless in baboons, could cause death by massive internal bleeding when injected into other primates who have not developed a natural resistance to the disease.
Dr Plagemann said there was no reliable test for the virus and so no guaranteed method of ensuring bone marrow cells from baboons were free of the infection. "It is obvious that transplanting tissue from infected baboons into humans would result in the transfer of considerable amounts of this virus. It could result in the selection of a variant of the virus that can replicate in humans."
If an animal virus such as simian haemorrhagic fever gains a foothold in the human population, it could effectively result in the creation of a deadly new disease in man. Dr Plagemann said the threat was similar to having another kind of Ebola virus emerge as a result of animal tissue transplants.
It is widely believed that the transfer of a monkey Aids-like virus into humans by an unknown route led to the origin of HIV. Other animal viruses are also known to have infected humans, such as a measles-type virus from horses which infected two people in Australia last year, killing one. The Ebola virus is believed to reside in an as yet undiscovered animal host.
Health authorities in the United States have given approval for the baboon experiment to begin within the next few weeks, subject to certain safety criteria. But the American surgeon leading the operation admitted there was no guarantee of preventing the transfer of a potentially dangerous baboon virus into humans.
The baboon bone-marrow transplant is being planned by the universities of Pittsburgh and California at San Francisco. Professor Suzanne Ildstad, the surgeon who will carry out the operation, told the Independent on Sunday that there was no way of treating the baboon tissue to guarantee it was infection-free. "We're doing everything possible. We've screened the baboons for everything known to infect humans," she said. If there is any risk, it is small compared to the potential benefits to Aids patient if the operation succeeds in restoring their defective immune systems, she added.
If operations like this do lead to the transfer of primate viruses, it is unlikely they will be highly infectious, she said. "We won't be creating something that wipes out the human race."
In Britain, Ian Kennedy, professor of medical law and ethics at King's College, London, and chair of a new committee set up to investigate animal organ transplants, will next week meet Stephen Dorrell, the Secretary of State for Health, to discuss the dangers of animal-to-human transplants.
A group of Cambridge scientists believe that the first transplant of a pig's heart into a human patient could take place next year. Other disorders, ranging from kidney and liver disease to leukaemia, are also possible contenders for "xenotransplants" - the transfer of animal tissue into humans.Reuse content