No transmission of porcine endogenous retrovirus after transplantation of adult porcine islets into diabetic nude mice and immunosuppressed rats

Background: The aim of this study was to investigate whether transmission of porcine endogenous retrovirus (PERV) occurs in a model of diabetes reversal by the xenotransplantation of adult porcine islets (APIs) into immunoincompetent diabetic rodents. Methods: Black-6 nu/nu mice and Lewis rats were immunosuppressed with cyclosporin A (CsA) and FTY 720, and rendered diabetic with streptozotocin. Purified APIs were transplanted into the renal subcapsular space; 5000 islet equivalents (IEQs) were used in the nude mice (n = 4) and 40 000 IEQs in the rats (n = 4). The nude mice were sacrificed at 75 days after transplantation. In order to confirm chronic xenograft function, the graft-bearing kidney was removed prior to sacrifice. The rats were followed until xenograft rejection, at which time they were sacrificed. Immediately after sacrifice, tissue samples (liver, spleen, and small intestine) were taken for analysis. Quantitative polymerase chain reaction (PCR) was used to assess evidence of PERV transmission, and porcine cell chimerism. Results: All animals became normoglycemic within 48 h of transplantation. The nude mice remained normoglycemic during the 75-day study period, with removal of the graft-bearing kidney resulting in prompt hyperglycemia. The rats remained normoglycemic until xenograft rejection, which occurred at 66 +/- 28 days. Despite the evidence of porcine cell microchimerism in recipients, real-time PCR detected no evidence of PERV transmission in any of the tissue specimens tested. Conclusions: There was no evidence of PERV transmission following transplantation of pig islets into diabetic nude mice and immunosuppressed rats.