Genetic Modification of Porcine Endogenous Retrovirus (PERV) Sequences in Cultured Pig Cells as a Model for Decreasing Infectious Risk in Xenotransplantation

Xenotransplantation of porcine (pig) organs into human patients has been proposed as a solution to the shortage of transplantable organs in human medicine. A potential safety barrier to clinical implementation of xenotransplantation is the infectious risk associated with expression of endogenous retroviral sequences in the porcine genome. Notably, Porcine Endogenous Retroviruses (PERVs) have been shown capable of infecting human cells in culture. The ability to specifically modify genomic loci in a wide range of in vitro and in vivo models has recently become widely accessible due to development of synthetic engineered nuclease technologies. Among them, Tal Effector Nucleases (TALENs) can be designed to recognize and catalyze double stranded DNA breaks (DSBs) in investigator‐specified genomic loci. These DSBs, when resolved by endogenous DNA repair mechanisms, commonly leave mutagenic insertions or deletions (indels) in target loci. This pilot study addresses the possibility of genetically modifying the porcine genome to specifically ablate PERV sequences via Tal Effector Nuclease (TALEN) genome editing techniques. TALEN sequences were designed and constructed against PERV pol and gag genes and were transfected into porcine PK(15) cells. Targeted pol and gag loci in PK(15) cells displayed TALEN‐induced genetic modification. These results suggest the potential utility of genome engineering strategies in ablating PERV gene expression in porcine xenotransplantation.