Purpose of review: As clinical trials are in progress involving porcine islet cell transplantation, microbial safety remains a key issue. Therefore, in the context of pig-to-human xenotransplantation, we provide an overview of the recent progress in the studies of relevant viruses including well known problematic viruses, such as herpesviruses and porcine endogenous retroviruses (PERV) in addition to some emerging issues regarding other pathogens.
Recent findings: The ability of herpesvirus to infect across species barriers is probably underestimated and requires monitoring and control of both xenograft donors and recipients for latent infection. Exclusion from donors and recipient monitoring for other exogenous pathogens including newly identified Parvovirus-4 are warranted. The availability of the swine whole genome sequence may help to characterize and select donor animals with less PERV infectivity. Rigorous PERV monitoring in both clinical and preclinical xenotransplantation experiments must be included in clinical protocols.
Summary: A wide range of pathogens, both viruses and bacteria, pose potential safety problems in xenotransplantation, highlighting the importance of prescreening of the donor animals, and careful monitoring and follow-up of the patients.