EXPRESSION OF PIG ENDOGENOUS RETROVIRUS BY PRIMARY PORCINE ENDOTHELIAL-CELLS AND INFECTION OF HUMAN-CELLS

Background The risk of interspecies transmission of retroviruses durin g xenotransplantation is suggested by reports of pig endogenous retrov irus (PERV) released from porcine cell lines productively infecting hu man cell lines in vitro and of infectious PERV being released from pig peripheral blood mononuclear cells after mitogenic stimulation. Endot helial cells are the main interface between a xenograft and the recipi ent's leucocytes and tissues. Methods We have analysed pig primary aor tic endothelial cells (PAEC) together with other transplantation-relev ant porcine cells and tissues for expression of PERV mRNA. Release of virus particles by PAEC was monitored by reverse transcriptase (RT) ac tivity in the medium of cultured PAEC. Infectivity for human cells was tested by co-cultivation of irradiated PAEC with the human embryonal kidney cell line HEK293 and looking for virus release from the human c ells. Findings PAECs, hepatocytes, lung, and skin from a variety of pi g strains and breeds expressed PERV mRNA, PAEC released infectious par ticles. Go-cultivation of PAEC and HEK293 led to productive infection of the human cells and expression of PERV types A and B. Interpretatio n Release of infectious virus from PAEC occurred without mitogenic sti mulation, suggesting a serious risk of retrovirus transfer after xenot ransplantation.