Role of DNA Methylation in Expression and Transmission of Porcine Endogenous Retroviruses

Abstract

c Porcine endogenous retroviruses (PERV) represent a major safety concern in pig-to-human xenotransplantation. To date, no PERV infection of a xenograft recipient has been recorded; however, PERVs are transmissible to human cells in vitro. Some recombinants of the A and C PERV subgroups are particularly efficient in infection and replication in human cells. Transcription of PERVs has been described in most pig cells, but their sequence and insertion polymorphism in the pig genome impede identification of transcriptionally active or silenced proviral copies. Furthermore, little is known about the epigenetic regulation of PERV transcription. Here, we report on the transcriptional suppression of PERV by DNA methylation in vitro and describe heavy methylation in the majority of PERV 5= long terminal repeats (LTR) in porcine tissues. In contrast, we have detected sparsely methylated or nonmethylated proviruses in the porcine PK15 cells, which express human cell-tropic PERVs. We also demonstrate the resistance of PERV DNA methylation to inhibitors of methylation and deacetylation. Finally, we show that the high permissiveness of various human cell lines to PERV infection coincides with the inability to efficiently silence the PERV proviruses by 5=LTR methylation. In conclusion, we suggest that DNA methylation is involved in PERV regulation, and that only a minor fraction of proviruses are responsible for the PERV RNA expression and porcine cell infectivity.

Specific and Stable Suppression of HIV Provirus Expression In Vitro by Chimeric Zinc Finger DNA Methyltransferase 1

“…After embryonic development, they are strictly repressed and become permanently silenced 8, 9. Several studies have demonstrated that DNA methylation plays a crucial role in such timing and long-lasting control in silencing HERVs 10, 11, 12, 13, 14…”

Identification of DNA methylation regulated novel host genes relevant to inhibition of virus replication in porcine PK15 cell using double stranded RNA mimics and DNA methyltransferase inhibitor

“…Matouskováatt. al found that 5′long terminal repeats (LTRs) of PERV amplified from PK15 contained 2.7% methylated CpG and no specific patterns of CpG methylation were observed in PERV 5′LTR sequences [39]. These results suggest minor methylation variation in PERV 5′LTR in PK15.…”

“…Researchers suggested that DNA hypomethylation is involved in porcine endogenous retrovirus (PERV) activation [39]. PK15 cell lines have been shown to be positive for PERV.…”

First update of the International Xenotransplantation Association consensus statement on conditions for undertaking clinical trials of porcine islet products in type 1 diabetes—Chapter 2a: source pigs—preventing xenozoonoses

“…Methods have been developed to screen for the absence of intact genomic PERV‐C env sequences (hereafter referred to as “PERV‐C negative”), which due to sequence variations require multiple assays as well as the PERV mRNA expression levels , allowing for the potential selection of donor animals and porcine islet products. Methods being developed in the field of epigenomics promise to illuminate the role of epigenetic transcriptional silencing of retrovirus and PERV expression . The appropriate role of the PERV infectivity assay which entails the long‐term in vitro coculture of islet product or surrogate donor cells with susceptible human cells for the assessment of PERV infectivity potential remains uncertain.…”