Pigs are favourable xenotransplantation sources because of their human-like physiology, large litters, short gestation period and genetic malleability [10] . However, pig to human virus transmission has been a concern since it was shown that porcine endogenous retroviruses (PERVs) could infect human cells in culture [6, [11] [12] [13] . Although PERV transmission has yet to be documented in xenotransplantation patients, significant concerns still exist regarding PERV and other potentially pathogenic viruses [14, 15] . Strategies to reduce the likelihood of PERV transmission have been proposed, such as selective breeding for lower levels of PERV, RNAi transgenesis to knock-down PERV expression or systematic deletion of active PERV copies (e.g., [15, 16] ). The first two are unlikely to be completely effective or risk-free and the third, albeit theoretically feasible, may be overly technical and prohibitively expensive. Therefore, alternative, robust and costeffective methods to reduce PERV transmission and possible xenozoonotic infections are desirable.