Pig endogenous retrovirus -: a threat to clinical xenotransplantation?

Transplantation shows good results for patients with end-stage disease, but there is an increasing lack of organs. Xenotransplantation, the transfer of live animal cells, tissues, or organs to another species, offers a potential solution to this shortfall. Pig is regarded as the animal of choice for this purpose. Meanwhile demonstration of pig endogenous retrovirus (PERV) in all porcine herds has caused serious concern with respect to a possible transmission of the virus to humans with a transplanted organ. Transmission to human cells has been documented under certain in vitro conditions. However, no such transmission has been demonstrated in vivo. The possible consequences of introducing PERV into immunocompromised human organisms are not known and it is necessary to collect more information. Novel and sensitive genomic assays to detect PERV infection are now available in addition to established virological, immunoserological and molecular methods. In order to minimise the risk of PERV transmission rigorous procedures should be established. International guidelines to reduce the risk should be followed. Although a number of immunological, physiological and virological questions need to be answered before the introduction of xenotransplantation as an alternative clinical treatment, some problems can only be solved by judicious clinical trials.