In vitro analysis of Porcine Endogenous Retroviruses in different pig cell types.

The shortage of organs for human transplantation is a topic of extreme interest, and xenotransplantation with porcine organs has been recognized as a promising solution. However, the potential spillover linked to infectious agents present in pigs remains a concern. Among these, Pig Endogenous Retroviruses (PERVs), whose proviral DNAs are integrated in the genome of all pig breeds, represent an extremely important biological risk. This study aims to evaluate PERVs distribution in several swine cell lines and samples of domestic and feral pigs. Moreover, the capacity of PERVs to infect human and non-human primate cells and to integrate in the cellular genome was tested by Real-Time PCR and by Reverse Transcriptase assay. Results indicated a widespread diffusion of PERVs both in cell lines and samples analysed: the viral genome was found in all the established cell lines, in 40% of the primary cell lines and in 60% of the tissue samples tested. The assays indicated that the virus can be transmitted from porcine to human cells: in the specific case, infected NSK and NPTr cells allow passage to human 293 and MRC-5 cells with active production of the virus demonstrable via PCR and RT assay. In light of these aspects and also the lack of studies on PERVs, it appears clear that there are still many questions to be clarified, also by means of future studies, before xenotransplantation can be considered microbiologically safe.