For the first time, scientists have discovered a retrovirus that infects swine human cells. The discovery, published in next month's issue of Nature Medicine , raises new questions about whether people could contract diseases if exotic animal organs become regularly transplanted into human patients. It may also force US regulators to tighten their xenotransplantation guidelines.
Critics have long argued that the transplantation of animal tissue in even a small number of immunocompromised patients could allow obscure pathogens to jump from animals to humans. Now a team led by Robin Weiss of the Cancer Research Institute of London reports that the "PK" porcine endogenous retrovirus, which does not seem to affect pigs, can replicate in mink and human cells. In addition, after one round of viral replication, human cells lack a key sugar that flags as cells compromises the immune system to destroy.
Although there is no evidence that PK causes human disease, retroviruses are particularly worrying candidates to cross the species barrier, said virologist Jon Allen Foundation San Antonio Southwest for biomedical research . They thrive in body fluids and tend to be copied repeatedly into gene sequences reception, which can cause genetic havoc sometimes lead to cancer. "We had assumed that the pig tissues were safer than the baboon tissues, but now we see that they can infect human cells," says Allen. The study suggests, he said, "maybe we should reconsider what guidelines we have and what species we use."
The United States shall permit the limited xenotransplantation while the British government last month announced that human clinical trials will not continue until the procedures are shown to be safe (see science NOW, January 17). officials US health now "have reason to pause," says Allen. "I hope they take it." Other experts predict the US will consider stricter guidelines. "I would not be terribly shocked if something was adopted, nor do I think it wrong," said Fritz Bach, a xenotransplantation researcher at Harvard Medical School. "But it is certainly not the time to say forget xenotransplantation. "
uS officials have declined to speculate whether the results would lead to stricter guidelines." This emphasizes the need for caution again, adding some concrete data to help us quantify risks and benefits, "said Amy Patterson, Acting Director of the Division of Food and Drug Administration of cell and gene therapies. The FDA plans to develop new guidelines on xenotransplantation later this year.
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