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.
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.
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.
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."
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.
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
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