Analysis of potential porcine endogenous retrovirus (PERV) transmission in a whole-organ xenotransplantation model without interfering microchimerism

Abstract

The question whether porcine xenografts can lead to porcine endogenous retrovirus (PERV) infection of recipients is critical for the evaluation of the safety of pigto-man xenotransplantation. Unfortunately, polymerase chain reaction (PCR)-based analysis of potential PERV infections in nonhuman-primate whole-organ xenotransplantation models is hampered by false positive results due to chimeric porcine cells. To avoid the inherent analytical problem of xenomicrochimerism, we developed a non-life-supporting pig-to-primate kidney xenotransplantation model: porcine kidneys were transplanted, whereas the functioning recipient kidneys remained in situ. Subsequent to rejection (after 2 hours to 15 days), xenografts were removed, and recipients remained alive for up to 287 days. Immunosuppressive therapy based on cyclophosphamide, cyclosporine, and steroids was maintained for 28 days after transplantation. Using appropriate PCR assays, xenochimerism was found in tissue samples and partly even in peripheral blood leukocytes (PBLs) while the porcine kidneys were in situ. After graft removal, xenochimerism was no longer detectable, thus allowing analysis for possible PERV transmission.

Analysis of pig-to-human porcine endogenous retrovirus transmission in a triple-species kidney xenotransplantation model

“…In fact, we were unable to demonstrate PERV particles in the recipients' serum samples by detection of reverse transcriptase activity. In agreement with a former study [18], no PERV mRNA could be detected, although the approach we used is sensitive enough to detect PERV RNA in pig serum. These results may still be due to insufficient sensitivity of the assay or to relatively quick destruction of virions by the recipients' immune systems.…”

“…Experimental transplantation of pig organs into non-human primates may mirror clinical xenotransplantation much more closely. None of the recent studies analysing potential in vivo infection of non-human primates resulted in evidence of PERV infection [18,19,20,21]. However, it is controversial whether a potentially lower susceptibility of non-human primate cells than that of human ones accounts for the absence of PERV infection in these studies.…”

“…Several studies have supplied evidence for PERV infection of certain non-human primate cells of different species, including gorilla, chimpanzee, baboon and rhesus monkey [13,16,17]. In contrast to the in vitro studies mentioned above, no evidence for PERV infection has been detected in the recent in vivo infection studies using non-human primates [18,19,20,21]. However, the value of non-human primate models for xenotransplantation risk assessment is controversial, as all non-human primate cells tested so far seem to be less permissive than certain human cell lines for PERV infection [19,20,21].…”

Absence of PERV infection in baboons after transgenic porcine liver perfusion1

“…In studies conducted by Martin et al, pig splenocyte transplantation or transient pig kidney transplantation was performed on immunosuppressed baboons [32,33]. Contrary to the rapid disappearance of xenogeneic cells from recipient's blood, they found chimeric porcine cells in a variety of tissue types for up to 535 days.…”

Xenogeneic islet transplantation of microencapsulated porcine islets for therapy of type I diabetes: long-term normoglycemia in STZ-diabetic rats without immunosuppression

“…However the limited supply of human islets and the difficulties with harvesting pure islets, make the use of human islets impractical. The xenogeneic transplantation of porcine islets of Langerhans is regarded as a potential alternative treatment for diabetes mellitus, but acute rejection [3,4] and possible infection with PERV [5,6] are obstacles for the clinical xenogeneic transplantation of porcine pancreatic islets. A solution to these obstacles could be the encapsulation of porcine islets.…”