Pig Xenographs: Risk of Endogenous Viruses
Another major obstacle to the use of transgenic pigs as a source of replacement organs for humans is the risk of new infectious diseases. In 1997, Robin A. Weiss, a virologist at University College London, discovered a new class of pig viruses called “porcine endogenous retroviruses” (PERVs) and determined that they have the ability to infect cultured human cells.
The transplantation of a pig organ into a human host would therefore create the opportunity for the transmission of PERVs, potentially enabling such viruses to evolve into human pathogens with a potential for person-to-person spread. Indeed, a retrospective study of patients who received heart valves from pigs identified the DNA of PERVs in some recipients.
Thus, there are real grounds for concern that xenografts from pigs could provide a path for the transmission of novel viruses from animals to humans. Until this issue is resolved definitively, clinical trials of xenotransplantation are unlikely to move forward. In sum, the jury is still out on the feasibility – and the desirability – of obtaining replacement organs from transgenic pigs.21