Infectious risk in xenotransplantation

Abstract

Xenotransplantation of tissues from swine into humans poses the threat of transfer of known and unknown porcine microorganisms to xenograft recipients and to the general population. Recent data are reviewed that offer a perspective on the risk for, and prevention of, xenozoonotic infections.

Progress has been reported on the identification, monitoring, and exclusion of exogenous porcine viruses from the donor pig. Human-tropic porcine endogenous retrovirus appears to be a recombinant of porcine endogenous retrovirus types A and C. Published observations of porcine endogenous retrovirus infection of human tissues in murine models appear to be artifacts of pseudotyping of porcine viruses by murine retroviruses and may overestimate the risks posed by xenotransplantation. The role of porcine endogenous retrovirus-encoded xenoantigens in xenograft rejection is under investigation.

A combination of barrier derivation, early weaning, and genetic engineering may be needed to exclude potential pathogens from xenograft tissues. Mouse models are limited in utility for retroviral studies of infectivity for human tissues by the presence of pseudotyping murine leukemia viruses. Protocols for microbiologic monitoring of patients and their social and sexual contacts must precede clinical trials. Techniques exist to monitor potential infectious complications after xenotransplantation so as to allow well monitored clinical trials.