general population by xenotransplantation. There was strong feeling among a number of committee members that special regulation of xenotransplant research is not justified because other types of research, including allotransplantation, also involve substantial risks. Other members of the committee argued that the potential for transmission of new infections to humans is a unique risk, justifying special regulations. However, all members of the committee agreed that some mechanism is needed to ensure attention to and reduction of the risk of infectious disease transmission. One mechanism acceptable to all committee members was the establishment of national guidelines. The committee was aware of and commends the efforts of the Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) in developing the first set of guidelines, which are soon to be released, but were not final before this report was complete. The development of these guidelines involved discussions with other federal agencies and representatives from stakeholder groups. The importance of such guidelines should be emphasized. Hence:

Recommendation 1: The committee recommends that guidelines for human trials of xenotransplantation address four major areas: (1) procedures to screen source animals for the presence of infectious organisms and consideration of the development of specific pathogen-free animals for use in xenotransplants; (2) continued surveillance throughout their lifetimes of patients and periodic surveillance of their contacts (families, health care workers, and others) for evidence of infectious diseases; (3) establishment of tissue banks containing tissue and blood samples from source animals and patients; and (4) establishment of national and local registries of patients receiving xenotransplants. Special efforts should be made to coordinate with international registries and databases.

These areas were discussed at the workshop as key elements for the effective monitoring of infectious disease transmission. For example, screening of source animals should focus first on those organisms known to infect that animal species and known to be pathogenic in humans. However, screening broadly for a wide range of organisms should be performed while conducting early trials until evidence is provided that screening for a particular organism is unnecessary. Screening of donor tissue must be complemented with mandatory active surveillance of patients receiving xenotransplants, as well as their contacts, for the sole purpose of determining the safety of xenotransplantation. Such surveillance will require collection of tissue and serum samples and coordination of information in a central database or registry. The requirement of lifelong surveillance certainly raises dangers from potential



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