title: Psoralen photochemical inactivation of Orientia tsutsugamushi in platelet concentrates.
abstract: BACKGROUND
  The risk of transfusion transmission of disease has been reduced by the combination of predonation questions and improved transfusion-transmitted disease assays, but the risk is still present. This study was conducted to determine if psoralen photochemistry could inactivate an obligate intracellular bacterium, with documented potential for transfusion, in PCs to further improve safety.
  
  
  METHODS
  PCs were inoculated with MNCs infected with Orientia tsutsugamushi. The concentrates were treated with amounts ranging from 0.86 to 138 micromol per L of 4'-(aminomethyl)-4,5',8-trimethylpsoralen hydrochloride (AMT) combined with a constant long-wave UVA light (320-400 nm) exposure of 5 J per cm(2). The effects of photochemical treatment were analyzed by using a mouse infectivity assay along with in vitro testing by PCR, indirect fluorescence antibody, direct fluorescence antibody, and Giemsa staining.
  
  
  RESULTS
  AMT, at 0.86 micromol per L or more, combined with UVA light of 5 J per cm(2), inactivated O. tsutsugamushi that contaminated PCs. The PCs that did not receive the combined treatment caused infection.
  
  
  CONCLUSIONS
  The psoralen AMT, in conjunction with UVA light exposure, effectively abolished the infectivity of PCs deliberately contaminated with the scrub typhus organism O. tsutsugamushi, as tested in a mouse infectivity assay.
authors.affiliation: Department of Blood Research, Walter Reed Army Medical Center, Washington, DC, USA.
authors.forename: K J
authors.initials: KJ
authors.lastname: Belanger
authors.forename: D J
authors.initials: DJ
authors.lastname: Kelly
authors.forename: F C
authors.initials: FC
authors.lastname: Mettille
authors.forename: C V
authors.initials: CV
authors.lastname: Hanson
authors.forename: L E
authors.initials: LE
authors.lastname: Lippert
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000382:microbiology*; D051379:Mice; D012285:Orientia tsutsugamushi / Q000187:drug effects* / Q000302:isolation & purification; D011701:PUVA Therapy; D012612:Scrub Typhus / Q000188:drug therapy