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The Risks of Xenotransplantation

One of the major stumbling blocks in xenotransplantation is the fear that transplanting animal organs, cells and tissues into people could expose them to an animal virus that could decimate not only the original recipient [who would be heavily immunosuppressed in the transplant setting], but could spread to the general population. Since xenotransplantation efforts are currently focused on using pigs as donors, many scientists have targeted their research on a virus native to every pig cell--the porcine endogenous retrovirus (PERV). Some worry, however, that in focusing on the PERV threat, scientists may be missing still other, unknown viruses.

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how big are the risks?

Excerpts from FRONTLINE's interviews with xenotransplantation and animal retrovirus researchers, here discussing the potential threat of a cross-species virus being transmitted in xenotransplantation.
Our Report Had an Immediate Effect

In 1997, Professor Robin Weiss's article in the journal Nature outlined his discovery that the porcine endogenous retrovirus (PERV) could infect human cells in culture. In this FRONTLINE interview, Weiss discusses how his work led to the FDA's ban--since lifted--on all xeno clinical trials and; why he doesn't think xenotransplantation can be made risk-free in public health terms.
Infection in Xenotransplantation

In this September 2000 editorial from the British Medical Journal, Harvard Medical School Associate Professor Jay Fishman reviews several studies on PERV infection and concludes "there is no proof yet of safety or danger."
Outbreak:  Some Other Examples of Cross-Species Virus Transmission

Infectious viruses, including the Epstein-Barr virus and cytomegalovirus, can be transmitted during allotransplants--transplants between different individuals of the same species. Thus, many worry that using animal organs in the xenotransplant setting may make it easier for viruses to cross the species barrier. Here are examples of viruses which are believed to have been transferred to humans from animals.
Emerging Infections: Another Warning

During the latter half of the 20th century, many scientists believed infectious diseases had neared extinction. In this April 2000 editorial published in The New England Journal of Medicine, Dr. Michael T. Osterholm describes how factors including changes in the global food supply and the widespread use of antibiotics in both humans and animals may have led to their return.

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