Porcine endogenous retroviruses inhibit human immune cell function: risk for xenotransplantation?

Transgenic pigs are currently the most favored potential source of organs for xenotransplantation. Like all mammalian species they all harbor endogenous retroviruses in their genome. These porcine endogenous retroviruses (PERVs) are produced from several primary cells and cell lines and are able to infect human cells. Here we demonstrate that different pig strains and different animals of one strain differ in their ability to produce PERVs from normal blood cells. We report that purified PERV particles show a protein pattern typical for type C retroviruses and are antigenically related to mammalian leukemia viruses. Like most retroviruses, purified PERVs and peptides derived from the highly conserved immunosuppressive domain of their transmembrane envelope protein inhibit human immune cell functions. This indicates that high titer replication of PERVs in the transplant recipient could therefore lead to an immunodeficiency disease.