Infectious risk in xenotransplantation--what post-transplant screening for the human recipient?

Xenotransplantation may be associated with the transmission of pig microorganisms including viruses, bacteria, fungi, and parasites. As the recipient may be immunosuppressed, infection and pathologic consequences may be more pronounced compared to non-immunosuppressed individuals. Transmission of most microorganisms with exception of porcine endogenous retroviruses (PERV) may be prevented by screening the donor pig and qualified pathogen-free breeding. PERVs represent a special risk as they are present in the genome of all pigs and infect human cells in vitro. Until now, no PERV transmission was observed in experimental and clinical xenotransplantations as well as in numerous infection experiments. Nevertheless, several strategies have been developed to prevent PERV transmission.