title: Activation of primary porcine endothelial cells induces release of porcine endogenous retroviruses.
abstract: BACKGROUND
  Endothelial cells form the interface between the porcine graft and the recipient and frequently become activated after xenotransplantation. To evaluate the safety of xenotransplantation further, we assessed the effect of cellular activation on the expression and release of porcine endogenous retroviruses from primary endothelial cells isolated from transgenic and nontransgenic pigs.
  
  
  METHODS
  Primary porcine endothelial cells, cultured from pigs transgenic for human decay accelerating factor, were treated with human tumor necrosis factor-alpha, porcine interferon-gamma, or lipopolysaccharide. The release of porcine endogenous retroviruses into the supernatant was monitored at 24-hr intervals (up to 72 hr) by polymerase chain reaction-based reverse transcriptase (PBRT) assay. Activated and unactivated endothelial cells were co-cultured with human cells to investigate the capacity of any virus released from the porcine cells to infect human cells.
  
  
  RESULTS
  Virus was not detected in supernatants from quiescent cells by PBRT analysis. The number of viral particles released from endothelial cells was 10 to 5 x 10 viral particles/mL after cellular activation with tumor necrosis factor-alpha, interferon-gamma, or lipopolysaccharide, as shown by PBRT analysis. In contrast, in vitro infection of human cells was observed with unactivated endothelial cells only and was not observed in co-cultures with the activated porcine cells.
  
  
  CONCLUSIONS
  Cytokine treatment of primary porcine endothelial cells results in an increase in the release of virus into the supernatant, but the observed increase in viral titer was not mirrored by an increase in infectivity toward human cells.
authors.affiliation: Department of Parasitology, National Institute for Medical Research, Mill Hill, London, United Kingdom. deirdrecunningham@cunning48.freeserve.co.uk
authors.forename: Deirdre A
authors.initials: DA
authors.lastname: Cunningham
authors.forename: Gabriella J
authors.initials: GJ
authors.lastname: Dos Santos Cruz
authors.forename: Xosé M
authors.initials: XM
authors.lastname: Fernández-Suárez
authors.forename: Alison J
authors.initials: AJ
authors.lastname: Whittam
authors.forename: Christopher
authors.initials: C
authors.lastname: Herring
authors.forename: Laura
authors.initials: L
authors.lastname: Copeman
authors.forename: Andrew
authors.initials: A
authors.lastname: Richards
authors.forename: Gillian A
authors.initials: GA
authors.lastname: Langford
mesh_terms: D000818:Animals; D018958:CD55 Antigens / Q000502:physiology*; D002478:Cells, Cultured; D020077:Endogenous Retroviruses / Q000302:isolation & purification*; D042783:Endothelial Cells / Q000821:virology*; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D013552:Swine / Q000821:virology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D018958:CD55 Antigens; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma