Xenogeneic infections and public health.

1. The scarcity of available human donor organs for use in allotransplantation has fuelled interest in xenotransplantation, the therapeutic use of living animal tissue in humans. The use of living animal tissue for therapeutic purposes in humans has raised concerns that xenotransplantation clinical trials may pose a presently unquantifiable but undeniable risk to public health. 2. Xenotransplantation has the potential to introduce new infections to the human community by infecting human recipients with agents that were not previously endemic in human populations (xenogeneic infections). 3. Manipulations intended to prevent xenograft rejection may also facilitate the transmission of agents that rarely or never infect humans under natural circumstances. 4. The US Food and Drug Administration (the government agency responsible for monitoring drug safety) has chosen to allow limited numbers of xenotransplantation clinical trials to proceed under carefully monitored conditions outlined in the Public Health Service (PHS) Guideline on Infectious Disease Issues in Xenotransplantation. 5. This PHS guideline particularly emphasizes the importance of pretransplantation screening and post-transplantation surveillance for safety monitoring. 6. Laboratory based surveillance for endogenous retroviruses and other identifiable agents that cannot be removed from the xenograft can augment clinical surveillance. 7. Laboratory based studies of xenograft survivors increase our ability to quantify xenotransplant-associated risks and, thereby, expand our capacity to make science-based assessments of appropriate public policy.