Considerations of specific pathogen-free swine (SPF) in xenotransplantation

The purpose of this manuscript was to introduce the complexities involved in defining both the appropriate health status and the management programs for SPF swine as they may relate to xenotransplantation. One factor that must always be considered in using swine is that they are considered agricultural animals regardless of their purpose and are regulated as such by municipalities, states, and countries. There are nonflexible regulations related to the interstate transportation of swine and even greater hurdles to international transportation. For example, I tried unsuccessfully for three years to transport a single breeding animal with a congenital heart defect to collaborators in the United Kingdom. Bureaucratic factors on both sides of the Atlantic proved insurmountable because the regulations were formulated for economic and isolation purposes and no exceptions could be granted for research animals. Another factor to be considered is the designation of SPF swine, which in this species has a specific proprietary connotation. If the finalized program for production of swine for xenotransplantation proves to be different from the already established SPF program, then a different designation may have to be used. For example, a term like "xenografic defined flora (XDF)" swine could be used to avoid confusion with the already established registry. If xenotransplantation using swine becomes a reality, then it is important that the parameters used to select such animals be defined in advance. It is unlikely that conventionally reared animals of uncertain health status will be widely accepted because of legal and ethical considerations. Likewise, I do not believe that the use of swine for xenotransplantation will be able to avoid the regulatory measures already in place for laboratory animals. The multidisciplinary approach to the problem initiated by the Institute of Medicine workshop is the most appropriate mechanism for resolving the issues.