Critical issues related to porcine xenograft exposure to human viruses: lessons from allotransplantation.

Purpose Of Review: Xenotransplantation of tissues from swine into humans poses the threat of bidirectional transfer of porcine or human microorganisms to the recipient or to the xenograft, respectively. This review focuses on recipient-derived infection. Recent data are reviewed that assess the susceptibility of porcine cells to human viruses. On the basis of the experience in allotransplantation, potential consequences for the xenograft are discussed.

Recent Findings: Traditionally, research on xenoses has focused on donor, that is pig-derived, infections. Efforts to exclude pathogens from pig donors have been successful with notable exceptions such as the genetically encoded porcine endogenous retrovirus. Intrinsic resistance of many viruses to infect cells from a different species has been assumed and may confer an advantage for a xenograft. Recent studies, however, have demonstrated the ability of a number of human viruses relevant in allotransplantation to infect porcine cells. Infection was associated with cytopathogenicity as well as cellular changes promoting adhesion and transmigration of human cells or a procoagulant stage.

Summary: Successful infection of porcine cells with human viruses has challenged the concept of species specificity. For some viruses, infection resulted in production of infective progenies and is associated with cytopathogenicity. Cellular alterations potentially enhance the risk for graft damage, rejection or coagulation abnormalities.